73 results on '"Chul-Hoon Kim"'
Search Results
2. A Hybrid Ru(II)/TiO2 Catalyst for Steadfast Photocatalytic CO2 to CO/Formate Conversion Following a Molecular Catalytic Route
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Hyun Seok Lee, So-Yoen Kim, Min Su Choe, Ho-Jin Son, Daehan Lee, Sang Ook Kang, Chul Hoon Kim, S.J. Choi, and Changhyun Back
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Inorganic Chemistry ,chemistry.chemical_compound ,Monomer ,chemistry ,Polymer chemistry ,Photocatalysis ,Homogeneous catalysis ,Formate ,Electron donor ,Physical and Theoretical Chemistry ,Fourier transform infrared spectroscopy ,Catalysis - Abstract
Herein, we employed a molecular Ru(II) catalyst immobilized onto TiO2 particulates of (4,4'-Y2-bpy)RuII(CO)2Cl2 (RuP; Y = CH2PO(OH)2), as a hybrid catalyst system to secure the efficient and steady catalytic activity of a molecular bipyridyl Ru(II)-complex-based photocatalytic system for CO2 reduction. From a series of operando FTIR spectrochemical analyses, it was found that the TiO2-fixed molecular Ru(II) complex leads to efficient stabilization of the key monomeric intermediate, RuII-hydride (LRuII(H)(CO)2Cl), and suppresses the formation of polymeric Ru(II) complex (-(L(CO)2Ru-Ru(CO)2L)n-), which is a major deactivation product produced during photoreaction via the Ru-Ru dimeric route. Active promotion of the monomeric catalytic route in a hetero-binary system (IrPS + TiO2/RuP) that uses TiO2-bound Ru(II) complex as reduction catalyst led to highly increased activity as well as durability of photocatalytic behavior with respect to the homogeneous catalysis of free Ru(II) catalyst (IrPS + Ru(II) catalyst). This catalytic strategy produced maximal turnover numbers (TONs) of >4816 and >2228, respectively, for CO and HCOO- production in CO2-saturated N,N-dimethylformamide (DMF)/TEOA (16.7 vol % TEOA) solution containing a 0.1 M sacrificial electron donor.
- Published
- 2021
3. Electron Injection Process of Porphyrin Dye into a Heterogeneous TiO2/Re(I) Photocatalyst
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Sang Ook Kang, Min Su Choe, S.J. Choi, Ho-Jin Son, Daehan Lee, Jae Yoon Shin, Chul Hoon Kim, Chyongjin Pac, and So-Yoen Kim
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Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Electron injection ,Scientific method ,Photocatalysis ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
We now report full details of the collisional ET process at the interface between the solvated porphyrin dye (a representative molecular dye) and heterogeneous TiO2 particles (a well-defined n-type...
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- 2021
4. Rapid Exciton Migration and Amplified Funneling Effects of Multi-Porphyrin Arrays in a Re(I)/Porphyrinic MOF Hybrid for Photocatalytic CO2 Reduction
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Won-Jo Jung, S.J. Choi, Chyongjin Pac, Ho-Jin Son, Kyutai Park, Jin-Ook Baeg, Sang Ook Kang, Soyeon Kim, and Chul Hoon Kim
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Materials science ,Exciton ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Heterogeneous catalysis ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,Turnover number ,Catalysis ,chemistry.chemical_compound ,Bipyridine ,chemistry ,Photocatalysis ,General Materials Science ,Carboxylate ,0210 nano-technology - Abstract
A porphyrinic metal-organic framework (PMOF) known as PCN-222(Zn) was chemically doped with a molecular Re(I) catalyst-bearing carboxylate anchoring group to form a new type of metal-organic framework (MOF)-Re(I) hybrid photocatalyst. The porphyrinic MOF-sensitized hybrid (PMOF/Re) was prepared with an archetypical CO2 reduction catalyst, (L)ReI(CO)3Cl (Re(I); L = 4,4'-dicarboxylic-2,2'-bipyridine), in the presence of 3 vol % water produced CO with no leveling-off tendency for 59 h to give a turnover number of ≥1893 [1070 ± 80 μmol h-1 (g MOF)-1]. The high catalytic activity arises mainly from efficient exciton migration and funneling from photoexcited porphyrin linkers to the peripheral Re(I) catalytic sites, which is in accordance with the observed fast exciton (energy) migration (≈1 ps) in highly ordered porphyrin photoreceptors and the effective funneling into Re(I) catalytic centers in the Re(I)-doped PMOF sample. Enhanced catalytic performance is convincingly supported by serial photophysical measurements including decisive Stern-Volmer interpretation.
- Published
- 2021
5. Collisional Electron Transfer Route between Homogeneous Porphyrin Dye and Catalytic TiO2/Re(I) Particles for CO2 Reduction
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Ho-Jin Son, Chul Hoon Kim, Jin-Ook Baeg, Sang Ook Kang, Chyongjin Pac, and S.J. Choi
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Quenching (fluorescence) ,Materials science ,Energy Engineering and Power Technology ,Photochemistry ,Porphyrin ,Catalysis ,Reduction (complexity) ,Electron transfer ,chemistry.chemical_compound ,chemistry ,Electron injection ,Homogeneous ,Materials Chemistry ,Electrochemistry ,Photocatalysis ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Abstract
Dye detachment issue in the TiO2-mediated dye-sensitized photocatalytic system engenders an electron injection route based on collisional quenching between the detached solution-phase dye and dispe...
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- 2020
6. Ancillary Ligand Effects on Heteroleptic Ir III Dye in Dye‐Sensitized Photocatalytic CO 2 Reduction: Photoaccumulation of Charges on Arylated Bipyridine Ligand and Its Control on Catalytic Performance
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Jae Yoon Shin, Ha-Yeon Cheong, Ho-Jin Son, Sang Ook Kang, Dae Won Cho, Chyongjin Pac, S.J. Choi, Ju Hyoung Jo, and Chul Hoon Kim
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010405 organic chemistry ,Chemistry ,Ligand ,Organic Chemistry ,Photodissociation ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Catalysis ,0104 chemical sciences ,Turnover number ,Bipyridine ,chemistry.chemical_compound ,Homogeneous ,Photocatalysis ,Iridium - Abstract
Herein, we report the synthesis, and photochemical and -physical properties, as well as the catalytic performance, of a series of heteroleptic IrIII photosensitizers (IrPSs), [Ir(C^N)2 (N^NAryl )]+ , possessing ancillary ligands that are varied with aryl-substituents on bipyridyl unit [C^N=(2-pyridyl)benzo[b]thiophen-3-yl (btp); N^NAryl =4,4'-Y2 -bpy (Y=-Ph or -PhSi(Ph)3 ]. We found that the π-extension of bipyridyl ligand by aryl-substitution put bipyridyl ligand in use as an electron relay unit that performed charge accumulation before delivering to the catalytic center, greatly improving the overall CO2 -to-CO conversion activities. In a typical run, the aryl-substituted IrPS (tBu IrP-PhSi )-sensitized homogeneous systems (IrPS+ReI catalyst) gave a turnover number of 1340 (ΦCO =24.2 %) at the early stage of photolysis (
- Published
- 2020
7. Phenothiazine Functionalized Multifunctional A−π–D−π–D−π–A-Type Hole-Transporting Materials via Sequential C–H Arylation Approach for Efficient and Stable Perovskite Solar Cells
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Hwan Kyu Kim, Chunyuan Lu, Chul Hoon Kim, Kyutai Park, and Mahalingavelar Paramasivam
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Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Acceptor ,Small molecule ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,chemistry ,Phenothiazine ,General Materials Science ,Lewis acids and bases ,0210 nano-technology ,Perovskite (structure) - Abstract
Three phenothiazine-based A-π-D-π-D-π-A-type small molecules containing various terminal acceptor units, which act as Lewis base blocks, have been synthesized via an efficient and step-economical, direct C-H arylation strategy in the aim toward the development of hole-transporting materials (HTMs) with multifunctional features (such as efficient hole extraction layer, trap passivation layer, and hydrophobic protective layer) for perovskite solar cells (PrSCs). Optical-electrochemical correlation and density functional theory studies reveal that dicyanovinylene acceptor in SGT-421 downshifted the highest occupied molecular orbital (HOMO) level (-5.41 eV), which is more proximal to the valence band (-5.43 eV) of the perovskite, whereas N-methyl rhodanine in SGT-420 and 1,3-indanedione (IND) in SGT-422 destabilized the HOMO, leading to an increased interfacial energy-level offset. SGT-421 exhibits superior properties in terms of a sufficiently low-lying HOMO level and favorable energy-level alignment, intrinsic hole mobility, interfacial hole transfer, hydrophobicity, and trap passivation ability over spiro-OMeTAD as a benchmark small-molecule HTM. As envisaged in the design concept, SGT-421-based PrSC not only yields a comparable efficiency of 17.3% to the state-of-art of spiro-OMeTAD (18%), but also demonstrates the enhanced long-term stability compared to the spiro-OMeTAD because of its multifunctional features. More importantly, the synthetic cost of SGT-421 is estimated to be 2.15 times lower than that of spiro-OMeTAD. The proposed design strategy and the study of acceptor-property relationship of HTMs would provide valuable insights into and guidelines for the development of new low-cost and efficient multifunctional HTMs toward the realization of efficient and long-term stable PrSCs.
- Published
- 2019
8. Ring Closure Reaction Pathway of a Diarylethene in Solution Using Femtosecond Time‐resolved Fluorescence Spectra
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Chul Hoon Kim, Taiha Joo, Kiho Seo, Intae Eom, and Sangdeok Shim
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chemistry.chemical_compound ,Materials science ,Diarylethene ,chemistry ,Femtosecond ,Closure (topology) ,General Chemistry ,Time-resolved spectroscopy ,Ring (chemistry) ,Photochemistry ,Spectral line - Published
- 2019
9. Molecular design and synthesis of D–π–A structured porphyrin dyes with various acceptor units for dye-sensitized solar cells
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Haoran Zhou, Min Su Kim, Chul Hoon Kim, Sung Ho Kang, Jung-Min Ji, Hyun Seok Lee, and Hwan Kyu Kim
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Materials science ,Photovoltaic system ,Energy conversion efficiency ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Photochemistry ,01 natural sciences ,Acceptor ,Porphyrin ,0104 chemical sciences ,Dye-sensitized solar cell ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,0210 nano-technology ,Absorption (electromagnetic radiation) ,HOMO/LUMO - Abstract
Two porphyrin sensitizers, SGT-023 and SGT-025, were synthesized through acceptor structural engineering. SGT-023 was designed by replacing the commonly used benzothiadiazole (BTD) unit in the well-known platform of D-porphyrin-triple bond-BTD-acceptor sensitizers (e.g., SM315 and SGT-021) with a pyridothiadiazole unit as a stronger electron-withdrawing group. As for SGT-025, an additional ethynylene bridge was inserted into the acceptor part of the well-known skeleton of D-porphyrin-triple bond-BTD-acceptor sensitizers. The impact of the auxiliary acceptors on the optical, electrochemical, and photovoltaic properties was investigated and compared with a benchmark dye, SGT-021, developed by our group. Consequently, both porphyrin sensitizers could red-shift the absorption range and downshift the lowest unoccupied molecular orbital (LUMO) energy level, which was supposed to achieve higher light harvest efficiency (LHE). Under standard global AM 1.5G solar light conditions, SGT-025 attained a relatively high maximum power conversion efficiency (PCE) of 11.0%, which was slightly lower than that of the reference dye SGT-021 (12.6%), and a moderate PCE of 5.6% was obtained by SGT-023. The main reason is the lower charge collection efficiency, which can be attributed to the tilted dye adsorption mode on TiO2. This may allow for faster charge recombination which eventually leads to lower Jsc, Voc and PCE.
- Published
- 2019
10. Novel trifluoropropoxy-substituted asymmetric carbazole derivatives as efficient and hydrophobic hole transporting materials for high-performance and stable perovskite solar cells
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Chul Hoon Kim, M. Aftabuzzaman, Hwan Kyu Kim, and Chunyuan Lu
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Electron mobility ,Materials science ,Carbazole ,General Chemical Engineering ,Energy conversion efficiency ,General Chemistry ,Industrial and Manufacturing Engineering ,Contact angle ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Environmental Chemistry ,Molecule ,Thermal stability ,Glass transition ,Perovskite (structure) - Abstract
For highly efficient and stable perovskite solar cells (PSCs), small molecular hole transporting materials (HTMs) with high glass transition temperature, hydrophobicity, excellent film-formation and excellent hole mobility is highly desireable. However, developing a single molecule, which could meet all the above mention properties, is challenging. Herein, novel small molecules were design and synthesized, which show a suitable HOMO energy level and fulfill the above metioned properties simultaneously. For this purpose, we incorporate a hydrophobic trifluoropropoxy-terminal group to diphenylamine in SGT-405(3,6), a carbazole-based promising non-spiro-type small molecular HTM with excellent performance and low-cost, leading to two new HTMs (SGT-405s(C2,CF3) and SGT-405d(C2,CF3)). Among them SGT-405s(C2,CF3) showed an excellent hole mobility of 3.32 × 10–4 cm2 V−1 s−1, a remarkable high Tg of 183 ℃ and increased water contact angle of 87° compared to that of spiro OMeTAD (77.7°). Due to these superior properties, compared to those of spiro-OMeTAD, PSCs based on SGT-405s(C2,CF3) showed a remarkable power conversion efficiency (PCE) of 20.14%, which is higher than that of spiro-OMeTAD (18.97%), together with enhanced long-term and thermal stability. Our work revealed for the first time that trifluoropropoxy is a potential terminal group and an effective strategy for the design of new HTMs possessing superior properties in terms of glass transition temperature, hydrophobicity and film formation, for realizing efficient PSCs with enhanced moisture and thermal stability, simultaneously.
- Published
- 2022
11. Elucidation of Excited-State Properties of Bimetallic Ir(III)–Pt(II) Complexes with Conjugated Bridging Ligands
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Ho-Jin Son, Chul Hoon Kim, Yang-Jin Cho, Hyun Wook Cha, Bong Soo Seo, So-Yoen Kim, and Sang Ook Kang
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chemistry.chemical_compound ,Crystallography ,General Energy ,Bridging (networking) ,Pyrazine ,chemistry ,Excited state ,Bridging ligand ,Physical and Theoretical Chemistry ,Conjugated system ,Bimetallic strip ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
We investigated excited-state properties of 4′,7′-phenanthrolino-5′,6′:2,3-pyrazine (ppz)-bridged bimetallic complexes, (L)2Ir-ppz-PtCl2 (Ir-ppz-Pt) (L = 2-(4′,6′-difluorophenyl)pyridinato-N,C2 (dfppy)), and [(L)2Ir]2(ppz) (Ir-ppz-Ir). These properties were compared to those of reported dpp bridging complexes, 2,3-bis(2-pyridyl)pyrazine (dpp)-bridged bimetallic complexes, Ir-dpp-Pt, and Ir-dpp-Ir. Excited-state properties of hetero-bimetallic Ir–Pt systems were very different from those of related Ru–Pt systems with a dpp bridging ligand; Ru-dpp-Pt displayed the spin forbidden metal-to-ligand charge-transfer emission, whereas Ir-dpp-Pt was relatively silent in emission. Steady-state photochemical studies and photodynamic studies were undertaken for each Ir or Pt center within peripheries of bridging ligands to confirm either energy or ET and at the same time its direction. Thermodynamic driving force of the electron-transfer (ET) process from Ir to Pt in the hetero-bimetallic Ir–Pt systems was predicted b...
- Published
- 2018
12. Hyperpolarized [1-13C]lactate flux increased in the hippocampal region in diabetic mice
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Young Suk Choi, Jong Eun Lee, Eosu Kim, Jae Eun Song, Chul Hoon Kim, Donghyun Kim, and Ho Taek Song
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0301 basic medicine ,Blood Glucose ,Male ,Magnetic Resonance Spectroscopy ,ATP citrate lyase ,medicine.medical_treatment ,Hippocampus ,lcsh:RC346-429 ,chemistry.chemical_compound ,0302 clinical medicine ,Citrate synthase ,Phosphorylation ,Hyperpolarized 13C ,Carbon Isotopes ,Glucose Transporter Type 1 ,Mice, Inbred ICR ,biology ,Acetyl-CoA ,Diabetes ,Fasting ,medicine.drug ,medicine.medical_specialty ,Diet, High-Fat ,Glucagon ,Streptozocin ,Diabetes Mellitus, Experimental ,Brain metabolism ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Internal medicine ,Glucose Intolerance ,medicine ,Animals ,Lactic Acid ,RNA, Messenger ,Molecular Biology ,lcsh:Neurology. Diseases of the nervous system ,Insulin ,Research ,Glucose transporter ,Feeding Behavior ,Streptozotocin ,030104 developmental biology ,Endocrinology ,chemistry ,Gene Expression Regulation ,Pyruvate metabolism ,Hyperglycemia ,biology.protein ,ATP Citrate (pro-S)-Lyase ,GLUT1 ,030217 neurology & neurosurgery - Abstract
Increasing evidence suggests there is a relationship between cognitive impairment and metabolic dysfunction. Diabetes is a chronic disease, and metabolic factors affecting brain metabolisms, such as serum glucose, insulin, and glucagon, are altered according to disease progression. In our previous study, we applied hyperpolarized [1-13C] pyruvate magnetic resonance spectroscopy in prediabetic mice after feeding them a 60% high-fat diet (HFD) for 6 months. Ultimately, we detected significantly increased [1-13C]lactate conversion in the whole brain and an almost five-fold increased [1-13C]lactate/pyruvate ratio in the hippocampal region. In the present study, we induced diabetes in mice by injecting streptozotocin and feeding them an HFD for 6 months. Unlike in prediabetic mice, [1-13C]lactate conversion in the diabetic mice did not differ from that in the control group, but [1-13C]lactate/total 13C ratio showed an almost 1.4-fold increase in the hippocampal region. We measured the amount of the lactate and mRNA levels of glucose transporters from isolated hippocampus and cortex samples. In the hippocampus, significantly decreased GLUT1 mRNA levels and increased lactate were detected, suggesting an inconsistency between glucose and pyruvate metabolism. Pyruvate can be produced from oxaloacetate as well as glucose. We investigated ATP citrate lyase (ACLY) because it cleaves citrate into oxaloacetate and acetyl CoA. Phosphorylated ACLY (Ser455), the active form, was increased in both hippocampus and cortex samples of mice injected with streptozotocin and fed an HFD. Also, phosphorylated ACLY/total ACLY showed a positive correlation with lactate amount in the hippocampus. Our results suggest that the brain has different responses to diabetic progression, but, in the hippocampus, maintains metabolic alteration toward increasing lactate production from the prediabetic to the diabetic stage. We suggest that ACLY-mediated pyruvate be used to support lactate levels in the hippocampus in cases of limited glucose availability.
- Published
- 2019
13. Geometry and steric effects on the electronic states of aryl-o-carboranes
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Chul Hoon Kim, Ho-Jin Son, Sang Ook Kang, So-Yoen Kim, and Yang-Jin Cho
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Steric effects ,Absorption spectroscopy ,010405 organic chemistry ,Aryl ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Electron transfer ,Crystallography ,chemistry ,Excited state ,Steric factor ,Materials Chemistry ,Physical and Theoretical Chemistry ,Ground state ,HOMO/LUMO - Abstract
o-Carborane was used to alter the electronic states of π-conjugated organic aryls, and demonstrated as an effective electron control unit, to tune HOMO and LUMO energies for the electron transfer. Two different types of bis-aryl compounds were selected: one with di-phenyls and its fused fluorenyl, and another with two isomers of naphthyls, α- and β-forms. Among the series of aryl compounds, the second type of naphthyls were more susceptible to electronic alteration and α-isomer of naphthyl showed the most perturbed electronic state. The ground state structures confirmed by crystallographic measurements provide a close correlation of structure and electronic property between photo-responsive aryl groups and o-carborane. In addition to the distance effect, within similar proximity of the aryl functional groups, namely naphthyl case, the steric factor controlled the altered electronic state. HOMO and LUMO energies were estimated and confirmed by cyclic voltammograms and DFT calculations, respectively, and established the authenticity of the electronic alteration. Excited states were calculated by the TD-DFT correlations with the corresponding absorption spectra to illustrate the electronic perturbation in a systematic fashion suggesting that excited states were lowered in regard to the electronic perturbation. Therefore, within bis-aryls-o-carborane series, the following decreasing energy order is observed; α-Np, β-Np, Flu, diPh, and Ph. The final verification of the lowered energy was made according to the electron transfer efficiency between the well-studied iridium based photosensitizer, Ir(ppy)3 and two typical bis-aryls-o-carboranes, α-Np and Ph. The electron transfer efficiency of α-Np is 10 times greater than that of Ph (1.231 × 107 M−1s−1 for α-Np and 9.275 × 105 M−1s−1 for Ph).
- Published
- 2018
14. Development of a Lower Energy Photosensitizer for Photocatalytic CO2 Reduction: Modification of Porphyrin Dye in Hybrid Catalyst System
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S.J. Choi, Sang Ook Kang, Qiankai Ba, Ho-Jin Son, Ha-Yeon Cheong, Chul Hoon Kim, Dong-Il Won, Chyongjin Pac, Jong-Su Lee, and Yang-Jin Cho
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Materials science ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Heterogeneous catalysis ,01 natural sciences ,Porphyrin ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Light intensity ,Acetylene ,chemistry ,Photocatalysis ,Photosensitizer ,Irradiation ,0210 nano-technology - Abstract
A series of Zn–porphyrin dyes was prepared and anchored onto a TiO2 surface to complete a dye-sensitized photocatalyst system, Zn–porphyrin-|TiO2|-Cat, and tested as lower energy photosensitizers for photocatalytic CO2 reduction. Three major synthetic modifications were performed on the Zn–porphyrin dye to obtain a lower energy sensitization and improve the catalyst lifetime. We found that incorporating acetylene and linear hexyl groups into the Zn–porphyrin core allowed facile lower energy sensitization, and the addition of the cyanophosphonic acid as an anchoring group gave the long-term dye stability on the TiO2 surface. Under irradiation with red light of >550 nm and a light intensity of 207 mW/cm2, the hybrid ZnPCNPA catalyst showed a TONRe of ∼800 over an extended time period of 90 h. The photocatalytic activities of porphyrin hybrids differ greatly with the binding strength of the anchoring groups of dye and spectral range of the irradiated light and its intensity.
- Published
- 2018
15. Resveratrol Induces Mitochondrial Apoptosis and Inhibits Epithelial-Mesenchymal Transition in Oral Squamous Cell Carcinoma Cells
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Jae-Yeol Lee, Sang-Hun Shin, Hae-Mi Kang, In-Ryoung Kim, Bong-Soo Park, Chul-Hoon Kim, In-Kyo Chung, Seong-Eon Kim, and Hae Ryoun Park
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0301 basic medicine ,Cancer Research ,Epithelial-Mesenchymal Transition ,Cell Survival ,Cell ,Morphogenesis ,Medicine (miscellaneous) ,Apoptosis ,Resveratrol ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Cell Movement ,Cell Line, Tumor ,medicine ,Humans ,Epithelial–mesenchymal transition ,Membrane Potential, Mitochondrial ,Nutrition and Dietetics ,Cancer ,Cell migration ,medicine.disease ,Antineoplastic Agents, Phytogenic ,Tongue Neoplasms ,030104 developmental biology ,medicine.anatomical_structure ,Oncology ,chemistry ,Cell culture ,Caspases ,030220 oncology & carcinogenesis ,Carcinoma, Squamous Cell ,Cancer research - Abstract
OSCC is the most common malignant cancer of the head and neck. EMT is an essential cellular process critical to the morphogenesis and homeostasis of solid tissues. It is also involved in the initial stage of cancer metastasis and invasion in which cells lose epithelial characteristics. While cancer therapy protocols such as surgery, radiation, and chemotherapy are effective and useful, the drug tolerance and toxicity of OSCC patients remain a problem. Resveratrol is mainly produced in red grape skin and exhibits anti-oxidative, anti-inflammatory, anti-proliferative, and anti-cancer properties. This study was undertaken to investigate the underlying mechanisms giving rise to the induction of apoptosis by resveratrol in the human tongue squamous cell carcinoma cell line. Resveratrol treatment resulted in a time- and dose-dependent decrease in cell viability and increased the apoptotic cell ratio in CAL-27, SCC15, and SCC25 cells. Resveratrol treatment of CAL-27 cells showed that several lines of apoptotic manifestation and decreased cell migration, invasion, and EMT-inducing transcription factor. Taken together, our findings demonstrate the inhibitory effect of resveratrol in human OSCC cells via the mitochondrial pathway and that resveratrol is able to inhibit cell invasion and migration by inhibiting the EMT-inducing transcription factors.
- Published
- 2017
16. Photosensitization Behavior of Ir(III) Complexes in Selective Reduction of CO2 by Re(I)-Complex-Anchored TiO2 Hybrid Catalyst
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Ha-Yeon Cheong, Yang-Jin Cho, Chul Hoon Kim, Dae Won Cho, Chyongjin Pac, Sang Ook Kang, So-Yoen Kim, and Ho-Jin Son
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010405 organic chemistry ,Cationic polymerization ,Electron donor ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Selective reduction ,Photosensitizer ,Irradiation ,Physical and Theoretical Chemistry - Abstract
A series of cationic Ir(III) complexes ([Ir(btp)2(bpy-X2)]+ (Ir-X+: btp = (2-pyridyl)benzo[b]thiophen-3-yl; bpy-X2 = 4,4′-X2-2,2′-bipyridine (X = OMe, tBu, Me, H, and CN)) were applied as visible-light photosensitizer to the CO2 reduction to CO using a hybrid catalyst (TiO2/ReP) prepared by anchoring of Re(4,4′-Y2-bpy)(CO)3Cl (ReP; Y = CH2PO(OH)2) on TiO2 particles. Irradiation of a solution containing Ir-X+, TiO2/ReP particles, and an electron donor (1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole) in N,N-dimethylformamide at greater than 400 nm resulted in the reduction of CO2 to CO with efficiencies in the order X = OMe > tBu ≈ Me > H; Ir-CN+ has no photosensitization effect. A notable observation is that Ir-tBu+ and Ir-Me+ are less efficient than Ir-OMe+ at an early stage of the reaction but reveal persistent photosensitization behavior for a much longer period of time unlike the latter. Comparable experiments showed that (1) the Ir-X+ sensitizers are commonly superior compared to Ru(bpy)32+, a widely ...
- Published
- 2017
17. Photophysics and Excited-State Properties of Cyclometalated Iridium(III)–Platinum(II) and Iridium(III)–Iridium(III) Bimetallic Complexes Bridged by Dipyridylpyrazine
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Sang Ook Kang, Chang Min Choi, Ho-Jin Son, Dae Won Cho, So-Yoen Kim, Nam Kim, Chul Hoon Kim, Chyongjin Pac, and Yang-Jin Cho
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Pyrazine ,010405 organic chemistry ,Ligand ,Stereochemistry ,chemistry.chemical_element ,Bridging ligand ,Chromophore ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,chemistry ,Pyridine ,Iridium ,Physical and Theoretical Chemistry ,Platinum ,Bimetallic strip - Abstract
We investigated the electrochemical and excited-state properties of 2,3-bis(2-pyridyl)pyrazine (dpp)-bridged bimetallic complexes, (L)2Ir-dpp-PtCl [1, L = 2-(4′,6′-difluorophenyl)pyridinato-N,C2 (dfppy); 2, L = 2-phenylpyridinato-N,C2 (ppy)] and [(L)2Ir]2(dpp) [3, L = dfppy; 4, L = ppy] compared to monometallic complexes, (L)2Ir-dpp (5, L = dfppy; 6, L = ppy) and dpp-PtCl (dpp-PtIICl2; 7). The single-crystal X-ray crystallographic structures of 1, 3, 5, and 6 showed that 1 and 3 have approximately coplanar structures of the dpp unit, while the noncoordinated pyridine ring of dpp in 5 and 6 is largely twisted with respect to the pyrazine ring. We found that the properties of the bimetallic complex significantly depended on the electronic and geometrical modulations of each fragment: (1) electronic structure of the main L (C^N) ligand in an iridium chromophore (L = dfppy or ppy) and (2) planarity of the bridging ligand (dpp). Their electrochemical and photophysical properties revealed that efficient electro...
- Published
- 2017
18. Agmatine ameliorates type 2 diabetes induced-Alzheimer's disease-like alterations in high-fat diet-fed mice via reactivation of blunted insulin signalling
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Hosung Jung, Somang Kang, Chul Hoon Kim, Eosu Kim, Jong Eun Lee, and Ho Taek Song
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Blood Glucose ,Male ,0301 basic medicine ,medicine.medical_specialty ,Agmatine ,Amyloid beta ,medicine.medical_treatment ,Type 2 diabetes ,Diet, High-Fat ,Mice ,Random Allocation ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,0302 clinical medicine ,Insulin resistance ,Alzheimer Disease ,Internal medicine ,medicine ,Animals ,Insulin ,Cognitive decline ,Maze Learning ,Pharmacology ,Mice, Inbred ICR ,biology ,Brain ,Type 2 Diabetes Mellitus ,Alzheimer's disease ,medicine.disease ,Streptozotocin ,Brain insulin resistance ,High-fat diet ,030104 developmental biology ,Endocrinology ,Diabetes Mellitus, Type 2 ,chemistry ,biology.protein ,Insulin Resistance ,030217 neurology & neurosurgery ,medicine.drug - Abstract
The risk of Alzheimer's disease (AD) is higher in patients with type 2 diabetes mellitus (T2DM). Previous studies in high-fat diet-induced AD animal models have shown that brain insulin resistance in these animals leads to the accumulation of amyloid beta (Aβ) and the reduction in GSK-3β phosphorylation, which promotes tau phosphorylation to cause AD. No therapeutic treatments that target AD in T2DM patients have yet been discovered. Agmatine, a primary amine derived from l-arginine, has exhibited anti-diabetic effects in diabetic animals. The aim of this study was to investigate the ability of agmatine to treat AD induced by brain insulin resistance. ICR mice were fed a 60% high-fat diet for 12 weeks and received one injection of streptozotocin (100 mg/kg/ip) 4 weeks into the diet. After the 12-week diet, the mice were treated with agmatine (100 mg/kg/ip) for 2 weeks. Behaviour tests were conducted prior to sacrifice. Brain expression levels of the insulin signal molecules p-IRS-1, p-Akt, and p-GSK-3β and the accumulation of Aβ and p-tau were evaluated. Agmatine administration rescued the reduction in insulin signalling, which in turn reduced the accumulation of Aβ and p-tau in the brain. Furthermore, agmatine treatment also reduced cognitive decline. Agmatine attenuated the occurrence of AD in T2DM mice via the activation of the blunted insulin signal.
- Published
- 2017
19. Important role of ancillary ligand in the emission behaviours of blue-emitting heteroleptic Ir(<scp>iii</scp>) complexes
- Author
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Chul Hoon Kim, Sang Ook Kang, Douglas W. Crandell, Jin-Hyoung Kim, Mu-Hyun Baik, So-Yoen Kim, Yang-Jin Cho, Won-Sik Han, Ho-Jin Son, and Ji-won Lee
- Subjects
Materials science ,Trifluoromethyl ,Dopant ,Ligand ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Reaction rate constant ,chemistry ,Materials Chemistry ,Blue emitting ,0210 nano-technology ,Boron ,Phosphorescence ,Diode - Abstract
A series of heteroleptic Ir(III) complexes composed of 2-(2,4-difluoro-3-(trifluoromethyl)phenyl)-4-methylpyridine (dfCF3) as the main ligand and such ancillary ligands as acetylacetonate [Ir(dfCF3)2(acac)] (acac), picolinate [Ir(dfCF3)2(pic)] (pic), and tetrakis-pyrazolyl borate [Ir(dfCF3)2(bor)] (bor) were prepared, and their emission behaviors depending on the ancillary ligands were systematically investigated. It was found that the Huang–Rhys factors (SMs) of the emission decrease in the order bor (0.97) > acac (0.87) > pic (0.76), while the nonradiative rate constants (knr/105 s−1) calculated from the quantum yields and lifetimes of emission were in the order acac (4.89) > pic (1.17) > bor (0.28). It was assumed that the large difference of knr for the complexes arose from important contributions of the ancillary ligands to the crossing from an emissive state (3MLCT) to a nonemissive metal-centered state (3MC). The activation energies for the crossing from 3MLCT to 3MC were estimated from the temperature dependencies of the emission lifetime and were found to be 46 meV for acac, 61 meV for pic, and >100 meV for bor. The experimental results were in line with the theoretical calculations based on integrating quantum chemical modeling methods. By the excellent emission behavior, bor was applied as a dopant to prototype deep-blue phosphorescent organic light-emitting diode devices, which revealed high emission efficiency and colour purity.
- Published
- 2017
20. Blunted response of hippocampal AMPK associated with reduced neurogenesis in older versus younger mice
- Author
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Sooah Jang, Minsun Park, Eun Woo Kim, Su Kyoung Lee, Kee Namkoong, Jihyeon Jeong, Jong Eun Lee, Eosu Kim, Hyun Jeong Kim, and Chul Hoon Kim
- Subjects
Doublecortin Domain Proteins ,Male ,0301 basic medicine ,Aging ,medicine.medical_specialty ,Neurogenesis ,AMP-Activated Protein Kinases ,Hippocampal formation ,Hippocampus ,Energy homeostasis ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,Adenosine Triphosphate ,0302 clinical medicine ,Neurotrophic factors ,Internal medicine ,medicine ,Animals ,Hypoglycemic Agents ,DAPI ,Muscle, Skeletal ,Protein kinase A ,Biological Psychiatry ,Pharmacology ,business.industry ,Brain-Derived Neurotrophic Factor ,Neuropeptides ,AMPK ,Skeletal muscle ,Ribonucleotides ,Aminoimidazole Carboxamide ,Mice, Inbred C57BL ,030104 developmental biology ,Endocrinology ,medicine.anatomical_structure ,Bromodeoxyuridine ,Gene Expression Regulation ,chemistry ,business ,Microtubule-Associated Proteins ,030217 neurology & neurosurgery - Abstract
The rate of hippocampal neurogenesis declines with aging. This is partly explained by decreased neural responsiveness to various cues stimulating metabolism. AMP-activated protein kinase (AMPK), a pivotal enzyme regulating energy homeostasis in response to metabolic demands, showed the diminished sensitivity in peripheral tissues during aging. AMPK is also known to be involved in neurogenesis. We aimed to see whether AMPK reactivity is also blunted in the aged hippocampus, and thus is associated with aging-related change in neurogenesis. Following subchronic (7days) intraperitoneal and acute intracerebroventricular (i.c.v.) administration of either 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR; AMPK activator) or saline (sham) to young (16-week-old) and old (72-week-old) mice, we measured changes in AMPK activity, brain-derived neurotrophic factor (BDNF) expression or neurogenesis in the hippocampus. AICAR-induced changes in AMPK activity were observed in the hippocampus of young mice after acute i.c.v. injection. However, neither subchronic nor acute treatment induced significant changes in AMPK activity in old mice. Intriguingly, directions of AICAR-induced changes in AMPK activity were opposite between the hippocampus (decrease) and skeletal muscle (increase). ATP levels were inversely correlated with hippocampal AMPK activity, suggesting that the higher energy levels achieved by AICAR treatment might deactivate neuronal AMPK in young mice. The blunted response of AMPK to AICAR in old age was also indicated by the observations that the levels of neurogenesis and BDNF expression were significantly changed only in young mice upon AICAR treatment. Our findings suggest that the blunted response of neuronal AMPK in old age might be responsible for aging-associated decline in neurogenesis. Therefore, in addition to activation of AMPK, recovering its sensitivity may be necessary to enhance hippocampal neurogenesis in old age.
- Published
- 2016
21. D-π-A-Structured Porphyrins with Extended Auxiliary π-Spacers for Highly Efficient Dye-Sensitized Solar Cells
- Author
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Su Hyun Kim, Jung-Min Ji, Chul Hoon Kim, Haoran Zhou, and Hwan Kyu Kim
- Subjects
Materials science ,Band gap ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,chemistry.chemical_compound ,Dye-sensitized solar cell ,chemistry ,polycyclic compounds ,heterocyclic compounds ,General Materials Science ,0210 nano-technology - Abstract
Zn(II)-porphyrin dyes (SGT-030 and SGT-031) with extended auxiliary π-spacers in the donor (D) part have been prepared and applied to dye-sensitized solar cells (DSSCs). The porphyrin dyes containe...
- Published
- 2019
22. Effects of stock density on the laying performance, blood parameter, corticosterone, litter quality, gas emission and bone mineral density of laying hens in floor pens
- Author
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S. B. Park, Chul Hoon Kim, Hyeon-Jung Kang, and Sun Hyo Kim
- Subjects
stock density ,040301 veterinary sciences ,Eggs ,Oviposition ,Population ,Biology ,Laying ,animal welfare ,0403 veterinary science ,chemistry.chemical_compound ,Eating ,Stocking ,Animal science ,Nutrient ,Corticosterone ,Ammonia ,Bone Density ,laying performance ,Animals ,Eggshell ,Animal Husbandry ,Stock (geology) ,Bone mineral ,Blood biochemistry ,Ecology ,corticosterone ,0402 animal and dairy science ,04 agricultural and veterinary sciences ,General Medicine ,Carbon Dioxide ,040201 dairy & animal science ,Animal Well-Being and Behavior ,Housing, Animal ,Diet ,Research Note ,chemistry ,Hy-line Brown laying hens ,Animal Science and Zoology ,Female ,bone mineral density ,Chickens - Abstract
The effects of stocking density on the performance, egg quality, leukocyte concentration, blood biochemistry, corticosterone levels, bone mineral density, and noxious gas emission of laying hens were investigated. Eight hundred 34-week-old Hy-Line Brown laying hens (Gallus gallus domesticus) were randomly assigned to one of 4 treatments, each of which was replicated 4 times. Four stocking densities, including 5, 6, 7, and 10 birds/m2, were compared. A commercial-type basal diet was formulated to meet or exceed nutrient recommendations for laying hens from the National Research Council. The diet was fed to the hens ad libitum for 8 wk. Results indicated that hen-day egg production, egg mass, and feed intake were less for (P < 0.01) 10 birds/m2 stock density than other stock densities. Production rate of floor and broken eggs and eggshell strength were greater (P < 0.01) for 10 birds/m2 stock density than other stock densities. There were no significant differences in the level of leukocytes among densities. However, heterophils and the H/L ratio were greater (P < 0.01) for 10 birds/m2 than in stock density of 6 or 7 birds/m2. Serum corticosterone was greater (P < 0.01) 10 birds/m2 than stock density than other stock densities. Litter moisture and gas emission (CO2 and NH3) were greater (P < 0.01) for 10 birds/m2 than stock density than 6 and 7 birds/m2 stock density. Bone mineral content was not influenced by increasing stock density. However, bone mineral density was less (P < 0.05) for 10 m2 stock density than other stock densities. These results indicate that increasing the density beyond 5 birds/m2 elicits some negative effects on laying performance of Hy-Line brown laying hens.
- Published
- 2016
23. Agmatine Ameliorates High Glucose-Induced Neuronal Cell Senescence by Regulating the p21 and p53 Signaling
- Author
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Juhyun Song, Eosu Kim, Chul Hoon Kim, Jong Eun Lee, Somang Kang, Yumi Oh, Byeori Lee, and Ho Taek Song
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Cell death ,p53 ,0301 basic medicine ,Senescence ,medicine.medical_specialty ,Programmed cell death ,Agmatine ,Arginine ,Pro-inflammatory cytokines ,Cell ,Cellular homeostasis ,Biology ,Proinflammatory cytokine ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,chemistry.chemical_compound ,0302 clinical medicine ,Internal medicine ,medicine ,chemistry.chemical_classification ,Reactive oxygen species ,p21 ,Cell biology ,030104 developmental biology ,medicine.anatomical_structure ,Endocrinology ,chemistry ,Hyperglycemia ,Original Article ,Neurology (clinical) ,High glucose ,030217 neurology & neurosurgery - Abstract
Neuronal senescence caused by diabetic neuropathy is considered a common complication of diabetes mellitus. Neuronal senescence leads to the secretion of pro-inflammatory cytokines, the production of reactive oxygen species, and the alteration of cellular homeostasis. Agmatine, which is biosynthesized by arginine decarboxylation, has been reported in previous in vitro to exert a protective effect against various stresses. In present study, agmatine attenuated the cell death and the expression of pro-inflammatory cytokines such as IL-6, TNF-alpha and CCL2 in high glucose in vitro conditions. Moreover, the senescence associated-β-galatosidase's activity in high glucose exposed neuronal cells was reduced by agmatine. Increased p21 and reduced p53 in high glucose conditioned cells were changed by agmatine. Ultimately, agmatine inhibits the neuronal cell senescence through the activation of p53 and the inhibition of p21. Here, we propose that agmatine may ameliorate neuronal cell senescence in hyperglycemia.
- Published
- 2016
24. Pore dilatation increases the bicarbonate permeability of CFTR, ANO1 and glycine receptor anion channels
- Author
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Ikhyun Jun, Mary Hongying Cheng, Eunji Sim, Jinsei Jung, Bong Lim Suh, Yonjung Kim, Hankil Son, Kyungsoo Park, Chul Hoon Kim, Joo-Heon Yoon, David C. Whitcomb, Ivet Bahar, and Min Goo Lee
- Subjects
0301 basic medicine ,biology ,Physiology ,Chemistry ,Bicarbonate ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,ANO1 ,03 medical and health sciences ,chemistry.chemical_compound ,030104 developmental biology ,Permeability (electromagnetism) ,biology.protein ,Biophysics ,Glycine receptor - Published
- 2016
25. Dye‐Sensitized Solar Cells: 14.2% Efficiency Dye‐Sensitized Solar Cells by Co‐sensitizing Novel Thieno[3,2‐ b ]indole‐Based Organic Dyes with a Promising Porphyrin Sensitizer (Adv. Energy Mater. 15/2020)
- Author
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Yu Kyung Eom, Jung-Min Ji, Hwan Kyu Kim, Chul Hoon Kim, and Haoran Zhou
- Subjects
Indole test ,chemistry.chemical_compound ,Dye-sensitized solar cell ,Materials science ,chemistry ,Renewable Energy, Sustainability and the Environment ,Co sensitization ,General Materials Science ,Photochemistry ,Porphyrin - Published
- 2020
26. NLRP3 Inflammasome Contributes to Lipopolysaccharide-induced Depressive-Like Behaviors via Indoleamine 2,3-dioxygenase Induction
- Author
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Sujeong Hong, Sangjun Park, Seon-A Jeon, Eun Ju Lee, Je-Wook Yu, Jungmin Yang, Boyoung Han, Seunghwan Son, Junghyun Son, Chul Hoon Kim, and Inhwa Hwang
- Subjects
0301 basic medicine ,Lipopolysaccharides ,Lipopolysaccharide ,indoleamine 2,3-dioxygenase ,Amitriptyline ,Inflammation ,Regular Research Articles ,Gene Expression Regulation, Enzymologic ,Pathogenesis ,03 medical and health sciences ,chemistry.chemical_compound ,Mice ,0302 clinical medicine ,Mediator ,NLR Family, Pyrin Domain-Containing 3 Protein ,medicine ,Animals ,Indoleamine-Pyrrole 2,3,-Dioxygenase ,Pharmacology (medical) ,RNA, Messenger ,Indoleamine 2,3-dioxygenase ,Cells, Cultured ,Pharmacology ,Mice, Knockout ,Analysis of Variance ,integumentary system ,Dose-Response Relationship, Drug ,business.industry ,Depression ,Caspase 1 ,Brain ,Inflammasome ,NLRP3 inflammasome ,Enzyme Activation ,Mice, Inbred C57BL ,Psychiatry and Mental health ,Disease Models, Animal ,Editor's Choice ,030104 developmental biology ,chemistry ,Immunology ,Systemic administration ,Antidepressant ,Cytokines ,medicine.symptom ,business ,Neuroglia ,030217 neurology & neurosurgery ,medicine.drug - Abstract
Background Inflammation may play a significant role in the pathogenesis of depression, although the molecular target for the treatment of inflammation-mediated depressive symptoms remains to be elucidated. Recent studies have implicated the NLRP3 inflammasome in various psychiatric disorders, including depression. However, the underlying mechanism by which NLRP3 inflammasome activation mediates the progression of depressive-like behaviors remains poorly understood. Methods We examined whether NLRP3 deficiency influenced depressive-like behaviors and cerebral inflammation following systemic administration of lipopolysaccharide in mice. To further assess the contribution of the NLRP3 inflammasome to the progression of depression, we evaluated the effects of NLRP3 signaling on levels of indoleamine 2,3-dioxygenase. Results Nlrp3-deficient mice exhibited significant attenuation of depressive-like behaviors and cerebral caspase-1 activation in a lipopolysaccharide-induced model of depression. Treatment with the antidepressant amitriptyline failed to block NLRP3-dependent activation of caspase-1, but inhibited lipopolysaccharide-promoted production of interleukin-1β mRNA via suppressing NF-κB signaling in mouse mixed glial cultures. Interestingly, lipopolysaccharide administration produced NLRP3-dependent increases in indoleamine 2,3-dioxygenase expression and activity of mouse brain. Furthermore, inflammasome-activating stimulations, but not treatment with the inflammasome product interleukin-1β, triggered indoleamine 2,3-dioxygenase mRNA induction in mixed glial cells. Conclusions Our data indicate that the NLRP3 inflammasome is significantly implicated in the progression of systemic inflammation-induced depression. NLRP3-dependent caspase-1 activation produced significant increases in indoleamine 2,3-dioxygenase levels, which may play a significant role in lipopolysaccharide-induced depression. Collectively, our findings suggest that indoleamine 2,3-dioxygenase is a potential downstream mediator of the NLRP3 inflammasome in inflammation-mediated depressive-like behaviors.
- Published
- 2017
27. Effect of Cholesterol on the Phase Change of Lipid Membranes by Antimicrobial Peptides
- Author
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Hyungkeun Choi and Chul Hoon Kim
- Subjects
chemistry.chemical_compound ,Phase change ,Chromatography ,Membrane ,chemistry ,Biochemistry ,Hexagonal crystal system ,Cholesterol ,Antimicrobial peptides ,General Chemistry - Published
- 2014
28. Self-Assembly of Supramolecular Light-Harvesting Arrays from Symmetric Perylene-3,4-dicarboximide Trefoils
- Author
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Yi Lin Wu, Kelly M. Lefler, Chul Hoon Kim, and Michael R. Wasielewski
- Subjects
Chemistry ,Supramolecular chemistry ,Excimer ,Crystallography ,chemistry.chemical_compound ,Phenylene ,Excited state ,Ultrafast laser spectroscopy ,Organic chemistry ,General Materials Science ,Emission spectrum ,Physical and Theoretical Chemistry ,Spectroscopy ,Perylene - Abstract
Unlike the widely studied perylene-3,4:9,10-bis(dicarboximide) (PDI) dyes, self-assembly of the corresponding perylene-3,4-dicarboximide (PMI) dyes into large arrays and studies of their excited state properties have received far less attention. Two symmetric PMI trefoils were synthesized by connecting the 9-position of the perylene core either directly (1) or through a phenylene linker (2) to the 1,3,5-positions of a central benzene ring. Synchrotron-based small- and wide-angle X-ray scattering measurements in methylcyclohexane show that trefoil 1 self-assembles into cofacial trimers (13) on average, while trefoil 2 forms much larger assemblies that are tridecamers (213) on average. Their photophysics were characterized using steady-state as well as transient absorption and emission spectroscopy. Time-resolved spectroscopy reveals that both 13 and 213 initially form excitonically coupled excited states that subsequently relax to excimer states having 20 and 8.4 ns lifetimes, respectively, which decay to ground-state primarily nonradiatively. The data are consistent with stronger electronic coupling between the PMI molecules in 213 relative to 13.
- Published
- 2014
29. Ground and excited state electronic spectra of perylenediimide dimers with flexible and rigid geometries in DNA conjugates
- Author
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Chul Hoon Kim, Michael R. Wasielewski, George C. Schatz, Martin McCullagh, Prakash P. Neelakandan, Tarek A. Zeidan, Frederick D. Lewis, and Josh Vura-Weis
- Subjects
inorganic chemicals ,Dimer ,Exciton ,General Chemistry ,Chromophore ,Excimer ,Photochemistry ,Fluorescence ,nervous system diseases ,body regions ,chemistry.chemical_compound ,chemistry ,Excited state ,Ultrafast laser spectroscopy ,Ground state - Abstract
The structure and electronic spectra of six DNA conjugates possessing two face-to-face perylenediimide (PDI) chromophores have been investigated. Structures of hairpins possessing two adjacent PDI base analogues opposite a tetrahydrofuran abasic site on the same or opposite strands were simulated using molecular dynamics. These structures are compared with those previously reported for a duplex and hairpin dimer possessing PDI linkers. The minimized structures all have face-to-face PDI geometries but differ in the torsional angle between PDI long axes and the offset between PDI centers. These structures provide the basis for analysing differences in the electronic spectra of the PDI dimers both in the ground state (UV-Vis and circular dichroism spectra) and excited state (fluorescence and transient absorption) determined in aqueous buffer and in the denaturing solvent dimethyl sulfoxide. PDI dimers with rigid structures and large PDI–PDI torsional angles display large effects of exciton coupling in their UV-Vis and CD spectra and also display split transient absorption bands; whereas PDI dimers with smaller PDI–PDI torsional angles and flexible structures display weaker UV-Vis and CD exciton coupling and a single transient absorption band. The excimer fluorescence maxima and decay times for all of these DNA–PDI constructs are similar.
- Published
- 2014
30. A genetic variant in GLP1R is associated with response to DPP-4 inhibitors in patients with type 2 diabetes
- Author
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Hye Sun Park, Obin Kwon, Chul Sik Kim, Yong Ho Lee, Lee Kyung Kim, Chul Hoon Kim, Eun Yeong Choe, Eugene Han, Kyong Soo Park, Soo Heon Kwak, Sang Hak Lee, Hye Jin Wang, and Eun Seok Kang
- Subjects
0301 basic medicine ,Male ,medicine.medical_specialty ,animal structures ,Population ,Incretin ,Observational Study ,030209 endocrinology & metabolism ,Dipeptidyl peptidase-4 inhibitor ,Type 2 diabetes ,Incretins ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Diabetes mellitus ,Internal medicine ,Genotype ,medicine ,Humans ,education ,Glycemic ,education.field_of_study ,Dipeptidyl-Peptidase IV Inhibitors ,response ,glucagon-like peptide-1 receptor ,business.industry ,Genetic Variation ,General Medicine ,Middle Aged ,medicine.disease ,030104 developmental biology ,Endocrinology ,chemistry ,Diabetes Mellitus, Type 2 ,type 2 ,dipeptidyl peptidase-4 inhibitor ,diabetes mellitus ,ComputingMethodologies_DOCUMENTANDTEXTPROCESSING ,Female ,Glycated hemoglobin ,business ,medicine.drug ,Research Article - Abstract
Supplemental Digital Content is available in the text, Incretin hormone-based therapy in type 2 diabetes has been widely used, and dipepdityl peptidase-4 (DPP-4) inhibitors, which prevent incretin degradation, have become popular oral hypoglycemic agents. The efficacy of DPP-4 inhibitors varies from individuals, and factors determining responses to DPP-4 inhibitors have not been fully established. We aimed to investigate whether genetic variations in glucagon-like peptide (GLP-1) receptor are associated with responses to DPP-4 inhibitors in patients with type 2 diabetes. Genetic variations of rs3765467 in GLP-1 receptor were explored in 246 patients with type 2 diabetes who received DPP-4 inhibitors treatment for 24 weeks in addition to previous medication. Patients with glycated hemoglobin (HbA1c) > 7% and who were naive to any DPP-4 inhibitors were enrolled. Responders were defined as those who showed a > 10% reduction in HbA1c after DPP-4 inhibitor treatment. DPP-4 inhibitors improved glycemic parameters and lipid profiles. Compared to the major genotype (GG), a larger proportion of patients with the minor allele genotype (GA/AA) were responders (P = 0.018), and also showing greater HbA1c reductions (1.3 ± 1.1 vs 0.9 ± 1.2%; P = 0.022). This genetic effect remained significant even after adjustment for other confounding factors (OR = 2.00, 95% CI = 1.03–3.89). Polymorphism in the GLP-1 receptor may influence DPP-4 inhibitor response. Further studies in larger population will help determine the association between genetic variation and interindividual differences in DPP-4 inhibitor therapy.
- Published
- 2016
31. Tubby domain superfamily protein is required for the formation of the 7S SNARE complex in Drosophila
- Author
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Chul Hoon Kim, Yong Taek Jeong, Seok Jun Moon, Ji Eun Lee, and Eun Jang Yoon
- Subjects
0301 basic medicine ,Nervous system ,Hot Temperature ,Mutant ,Biophysics ,Regulator ,Tubby protein ,Biology ,Biochemistry ,Animals, Genetically Modified ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,medicine ,Animals ,Drosophila Proteins ,Neurotransmitter ,Molecular Biology ,Genetics ,Neurons ,fungi ,Cell Biology ,Phenotype ,Cell biology ,030104 developmental biology ,medicine.anatomical_structure ,Drosophila melanogaster ,chemistry ,Mutation ,Synapses ,Nerve Net ,SNARE complex ,SNARE Proteins ,030217 neurology & neurosurgery ,Function (biology) ,Heat-Shock Response ,Locomotion - Abstract
Tubby domain superfamily protein (TUSP) is a distant member of the Tubby-like protein (TULP) family. Although other TULPs play important roles in sensation, metabolism, and development, the molecular functions of TUSP are completely unknown. Here, we explore the function of TUSP in the Drosophila nervous system where it is expressed in all neurons. Tusp mutant flies exhibit a temperature-sensitive paralysis. This paralysis can be rescued by tissue-specific expression of Tusp in the giant fibers and peripherally synapsing interneurons of the giant fiber system, a well-characterized neuronal circuit that mediates rapid escape behavior in flies. Consistent with this paralytic phenotype, we observed a profound reduction in the assembly of the ternary 7S SNARE complex that is required for neurotransmitter release despite seeing no changes in the expression of each individual SNARE complex component. Together, these data suggest TUSP is a novel regulator of SNARE assembly and, therefore, of neurotransmitter release.
- Published
- 2016
32. Optimization of the radiosynthesis of [18F]MEFWAY for imaging brain serotonin 1A receptors by using the GE TracerLab FXFN-Promodule
- Author
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Minkyung Lee, Jae Yong Choi, Young Hoon Ryu, Tae Joo Jeon, Young Beom Seo, Eun Jung Kim, JeeHae Kang, Jong Doo Lee, Phong Truong, Dong Goo Kim, Chul Hoon Kim, and Tae Hyun Choi
- Subjects
Chemistry ,Methylamine ,medicine.drug_class ,Organic Chemistry ,Radiochemistry ,Extraction (chemistry) ,Radiosynthesis ,Total synthesis ,Carboxamide ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,Yield (chemistry) ,Drug Discovery ,medicine ,Organic chemistry ,Radiology, Nuclear Medicine and imaging ,Methanol ,Acetonitrile ,Spectroscopy - Abstract
The aim of this study was to develop a highly reliable radiofluorination method for the preparation of N-{2-[4-(2-methoxyphenyl)piperazinyl]ethyl}-N-(2-pyridyl)-N-(4-(18) F-fluoromethylcyclohexane)carboxamide ([(18) F]Mefway) by using a fully automated system. The optimal condition is composed of two parts. The extraction system of the trapped F-18 in the anion exchange resin (i.e., quaternary methylamine cartridge) is a complex of Kryptofix 2.2.2. (K222, 4 mg/0.9 mL methanol) and K2 CO3 (1 mg/0.1 mL H2 O). After removing the solvents, the trans-tosylated Mefway precursor (1 mg/0.5 mL acetonitrile) was reacted with dried K222-K[(18) F] at 100°C for 5 min. After purification and formulation, [(18) F]Mefway was obtained with 38 ± 2.4% (decay corrected, n = 34) radiochemical yield, a total synthesis time of 52 ± 3.4 min, specific activity was 120.6 ± 8.7 GBq/µmol at the end of synthesis and a radiochemical purity of 99%. According to the quality control tests, formulated [(18) F]Mefway is suitable to apply parenteral clinical application.
- Published
- 2013
33. Hydroxychalcones as Potential Anti-Angiogenic Agent
- Author
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Radha Karki, Youra Kang, Jung-Ae Kim, Eung-Seok Lee, Kyungsook Kwak, and Chul Hoon Kim
- Subjects
Vascular endothelial growth factor ,chemistry.chemical_compound ,chemistry ,biology ,Angiogenesis ,VEGF receptors ,Anti angiogenic ,Edible plants ,biology.protein ,General Chemistry ,Pharmacology - Abstract
Department of Pharmacology, College of Medicine, Yonsei University, Seoul 120-752, KoreaReceived March 14, 2012, Accepted June 4, 2012Key Words : Hydroxychalcones, Vascular endothelial growth factor (VEGF), Angiogenesis, Chick chorioal-lantoic membrane (CAM)IntroductionChalcones (1,3-diphenyl propenone), the precursors offlavonoids and isoflavonoids, are abundant in edible plants.
- Published
- 2012
34. Coherent Nuclear Wave Packets Generated by Ultrafast Intramolecular Charge-Transfer Reaction
- Author
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Myeongkee Park, Taiha Joo, Kyoung Chul Ko, So Young Kim, Chul Hoon Kim, and Jin Yong Lee
- Subjects
Chemistry ,Wave packet ,Analytical chemistry ,Fluorescence ,Molecular physics ,Reaction rate ,chemistry.chemical_compound ,Modulation ,Intramolecular force ,parasitic diseases ,General Materials Science ,Physical and Theoretical Chemistry ,Time-resolved spectroscopy ,Laurdan ,Ultrashort pulse - Abstract
Intramolecular charge-transfer (ICT) dynamics, including reaction coordinates, structural changes, and reaction rate, has been noted experimentally and theoretically. Here we report the ICT dynamics of laurdan investigated by time-resolved fluorescence at extreme time resolution of 30 fs. A single high-frequency coherent nuclear wave-packet motion on the product potential surface is observed through the modulation of the fluorescence intensity in time. Theory and experiment show that this vibrational mode involves large displacement of the carbon atoms in the naphthalene backbone, which indicates that the naphthalene backbone coordinates are strongly coupled to the ICT reaction of laurdan, not the twisting or planarization of the dimethylamino group.
- Published
- 2012
35. Electron Transfer within Self-Assembling Cyclic Tetramers Using Chlorophyll-Based Donor–Acceptor Building Blocks
- Author
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Chul Hoon Kim, Michael R. Wasielewski, Victoria L. Gunderson, Dick T. Co, and Amanda L. Smeigh
- Subjects
Chlorophyll ,Models, Molecular ,Absorption spectroscopy ,macromolecular substances ,Naphthalenes ,Photochemistry ,Biochemistry ,Catalysis ,Electron Transport ,chemistry.chemical_compound ,Electron transfer ,Colloid and Surface Chemistry ,Pyridine ,Electrochemistry ,Organometallic Compounds ,polycyclic compounds ,Molecular Structure ,Chemistry ,food and beverages ,General Chemistry ,Electron transport chain ,Acceptor ,Monomer ,Cyclization ,Covalent bond ,Intramolecular force - Abstract
The synthesis and photoinduced charge transfer properties of a series of Chl-based donor-acceptor triad building blocks that self-assemble into cyclic tetramers are reported. Chlorophyll a was converted into zinc methyl 3-ethylpyrochlorophyllide a (Chl) and then further modified at its 20-position to covalently attach a pyromellitimide (PI) acceptor bearing a pyridine ligand and one or two naphthalene-1,8:4,5-bis(dicarboximide) (NDI) secondary electron acceptors to give Chl-PI-NDI and Chl-PI-NDI(2). The pyridine ligand within each ambident triad enables intermolecular Chl metal-ligand coordination in dry toluene, which results in the formation of cyclic tetramers in solution, as determined using small- and wide-angle X-ray scattering at a synchrotron source. Femtosecond and nanosecond transient absorption spectroscopy of the monomers in toluene-1% pyridine and the cyclic tetramers in toluene shows that the selective photoexcitation of Chl results in intramolecular electron transfer from (1*)Chl to PI to form Chl(+•)-PI(-•)-NDI and Chl(+•)-PI(-•)-NDI(2). This initial charge separation is followed by a rapid charge shift from PI(-•) to NDI and subsequent charge recombination of Chl(+•)-PI-NDI(-•) and Chl(+•)-PI-(NDI)NDI(-•) on a 5-30 ns time scale. Charge recombination in the Chl-PI-NDI(2) cyclic tetramer (τ(CR) = 30 ± 1 ns in toluene) is slower by a factor of 3 relative to the monomeric building blocks (τ(CR) = 10 ± 1 ns in toluene-1% pyridine). This indicates that the self-assembly of these building blocks into the cyclic tetramers alters their structures in a way that lengthens their charge separation lifetimes, which is an advantageous strategy for artificial photosynthetic systems.
- Published
- 2012
36. A Solid-state NMR Study of the Kinetics of the Activity of an Antimicrobial Peptide, PG-1 on Lipid Membranes
- Author
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Chul Hoon Kim and Sungsool Wi
- Subjects
chemistry.chemical_classification ,Whole membrane ,Chromatography ,Kinetics ,technology, industry, and agriculture ,Peptide binding ,Biological membrane ,Peptide ,General Chemistry ,chemistry.chemical_compound ,Membrane ,chemistry ,Biophysics ,lipids (amino acids, peptides, and proteins) ,Lipid bilayer ,POPC - Abstract
The activity of an antimicrobial peptide, protegrin-1 (PG-1), on lipid membranes was investigated using solidstate NMR and a new sampling method that employed mechanically aligned bilayers between thin glass plates. At 95% hydration and full hydration, the peptide respectively disrupted 25% and 86% of the aligned 1palmitoyl-2-oleoyl-sn-glycero-3-phosphotidylcholine (POPC) bilayers at a P/L (peptide-to-lipid) ratio of 1/20 under the new experimental conditions. The kinetics of the POPC bilayers disruption appeared to be diffusioncontrolled. The presence of cholesterol at 95% hydration and full hydration reduced the peptide disruption of the aligned POPC bilayers to less than 10% and 35%, respectively. A comparison of the equilibrium states of heterogeneously and homogeneously mixed peptides and lipids demonstrated the importance of peptide binding to the biomembrane for whole membrane disruption.
- Published
- 2012
37. A Two-Photon Turn-On Probe for Lipid Rafts with Minimum Internalization
- Author
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Jun Han Lee, Chang Su Lim, Hwan Myung Kim, Chul Hoon Kim, Hyung Joong Kim, Taiha Joo, Bong Rae Cho, and Yu Shun Tian
- Subjects
Alkanesulfonates ,Biochemistry ,Cell Line ,chemistry.chemical_compound ,Membrane Microdomains ,Two-photon excitation microscopy ,2-Naphthylamine ,Fluorescence microscope ,Humans ,Molecular Biology ,Lipid raft ,Fluorescent Dyes ,Photons ,Vesicle ,Organic Chemistry ,Sarcosine ,Raft ,Fluorescence ,Sphingomyelins ,Cell biology ,Cholesterol ,Microscopy, Fluorescence ,chemistry ,Phosphatidylcholines ,Biophysics ,Molecular Medicine ,Sphingomyelin ,Laurdan - Abstract
The lo domains, also called lipid rafts, are believed to serve as a platform to support various cellular processes such as signal transduction, membrane trafficking, pathogen invasion, cholesterol homeostasis, neurodegenerative diseases, and angiogenesis. The existence of lipid rafts has been demonstrated in mammalian cells and in model membranes by using various techniques such as atomic force microscopy, fluorescence microscopy, and coherent anti-Stokes Raman scattering microscopy. To understand their roles in cell biology, it is crucial to visualize such domains in the live cells and tissues. An ideal tool for this purpose is two-photon microscopy (TPM) that utilizes two near-infrared photons for excitation. The advantages of TPM include the capability of visualizing the real-time activities of the biological targets in live cells and intact tissues at >100 mm depth with minimum interference due to the tissue preparation artifacts that can extend ~70 mm from the tissue surface. For maximum utilization of TPM, many TP probes for specific applications are needed. However, TP probes for such applications are rare. Earlier, we reported a membrane TP polarity probe, CL, which showed several advantages over laurdan including greater sensitivity to the solvent polarity, brighter TPM image, and more precise reflection of the cell environment. We also developed a TP turn-on probe, CL2, which showed larger TP action cross-section and higher sensitivity to the polarity of the environment than CL. This allowed selective detection of the lipid rafts in live cells and tissues by TPM. Unfortunately, CL2 had one shortcoming; it internalized into the cytoplasm upon prolonged incubation with cells, causing a blurred TPM image. To overcome this problem, we have designed a new TP turn-on (off-on) probe (SL2) that has sodium sulfonate in the head group and exclusively stains the plasma membrane. Herein, we report that SL2 can detect the lipid rafts in the live cells and intact tissues without internalization problems by simply collecting the TP excited fluorescence (TPEF) by using TPM. The preparation of SL2 is given in the Supporting Information. The solubility of SL2 in water was 7 mm, which is sufficient to stain the cells (Figure S1 in the Supporting Information). The change of the head group from a carboxylic acid (CL2, 4 mm) to a sulfonate increased the water solubility by ~ twofold. The absorption and emission spectra of SL2 showed gradual bathochromic shifts with increasing solvent polarity (Figure 1A and Table S1) indicating the charge-transfer character of the emitting state. The shifts were larger for the emission than for the absorption spectra (21 vs. 126 nm). Moreover, the fluorescence quantum yield (F) increased by 22-fold as the solvent was changed from EtOH/H2O (F=0.04) to THF (F=0.88). CL2 showed similar behavior except that fluorescence enhancement factor (FEF) was lower [FEF(CL2)=16 versus FEF(SL2)= 22] (Table S1). Hence, the fluorescence of SL2 is more sensitive to the polarity of the environment than that of CL2. The fluorescence intensity of SL2 showed similar decrease with the hydrophilicity of the large unilamellar vesicles (LUVs) in the order, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/cholesterol (DPPC/CHL (40 mol%), lo)>DOPC/sphingomyelin/CHL (1:1:1, raft mixture)>1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC, ld ; Figure S2). The relative fluorescence intensities of SL2 in DPPC/CHL/raft mixture/DOPC in the 420–520 nm range are 7.0/4.8/1.0, respectively; SL2 emits sevenfold stronger fluorescence in the lo than in the ld domain. The slightly weaker fluorescence in the raft mixture than in DPPC/CHL can be explained if SL2 exists in 63/37 ratio in the lo/ld domains of the raft mixture with 7/1 intensity ratio (vide supra). A similar result was reported for CL2 (lo/ld=86:14). [12] This indicates high preference of these probes to reside in the lo domain, which can be attributed to the more favorable hydrophobic interactions with sphingomyelin when compared to DOPC. The sensitivity of the laurdan derivatives on the polarity of the environment originates from the intramolecular charge [a] C. S. Lim, J. H. Lee, Dr. Y. S. Tian, Prof. B. R. Cho Department of Chemistry, Korea University 1-Anamdong, Seoul, 136-701 (Korea) Fax: (+82)2-3290-3544 E-mail : chobr@korea.ac.kr [b] H. J. Kim, Prof. H. M. Kim Division of Energy Systems Research, Ajou University Suwon, 443-749 (Korea) E-mail : kimhm@ajou.ac.kr [c] Dr. C. H. Kim, Prof. T. Joo Department of Chemistry, Pohang University of Science and Technology Pohang, 790-784 (Korea) E-mail : thjoo@postech.ac.kr Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cbic.201000609.
- Published
- 2010
38. Excited State Intramolecular Proton Transfer and Charge Transfer Dynamics of a 2-(2′-Hydroxyphenyl)benzoxazole Derivative in Solution
- Author
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Jaehun Park, Chul Hoon Kim, Jangwon Seo, Taiha Joo, and Soo Young Park
- Subjects
Benzoxazole ,Dihedral angle ,Photochemistry ,Enol ,chemistry.chemical_compound ,Electron transfer ,symbols.namesake ,chemistry ,Intramolecular force ,Stokes shift ,symbols ,Physical and Theoretical Chemistry ,Ground state ,Derivative (chemistry) - Abstract
Excited state intramolecular proton transfer (ESIPT) and subsequent intramolecular charge transfer (ICT) dynamics of a 2-(2'-hydroxyphenyl)benzoxazole derivative conjugated with an electron withdrawing group (HBOCE) in solutions and a polymer film has been investigated by femtosecond time-resolved fluorescence (TRF) and TRF spectra measurements without the conventional spectral reconstruction method. TRF with high enough resolution (100 fs) reveals that the ESIPT dynamics of HBOCE in liquids proceeds by at least two time constants of approximately 250 fs and approximately 1.2 ps. The relative amplitude of the slower picosecond component is smaller in the polymer film than that in solution. Conformational heterogeneity in the ground state originating from the dispersion of the dihedral angle between the phenolic and benzoxazole groups is invoked to account for the dispersive ESIPT dynamics in liquids. From the TRF spectra of both the enol and keto isomers, we have identified the ICT reaction of the keto isomer occurring subsequent to the ESIPT. The ICT proceeds also by two time constants of near instantaneous and 2.7 ps. Since the ICT dynamics of HBOCE is rather close to the polar solvation dynamics, we argue that the ICT is barrierless and determined mostly by the solvent fluctuation.
- Published
- 2010
39. Remarkably Efficient Photocurrent Generation Based on a [60]Fullerene-Triosmium Cluster/Zn-Porphyrin/Boron-Dipyrrin Triad SAM
- Author
-
Chul Hoon Kim, Jihee Park, Jaehoon Jung, Wonyong Choi, Joon T. Park, Taiha Joo, Young-Kyu Han, Bo Keun Park, Chang Yeon Lee, and Jae Kwon Jang
- Subjects
Absorption spectroscopy ,Organic Chemistry ,Quantum yield ,General Chemistry ,Photochemistry ,Ascorbic acid ,Porphyrin ,Catalysis ,Photoinduced electron transfer ,chemistry.chemical_compound ,Electron transfer ,chemistry ,BODIPY ,Cyclic voltammetry - Abstract
A new artificial photosynthetic triad array, a [60]fullerene-triosmium cluster/zinc-porphyrin/boron-dipyrrin complex (1, Os(3)C(60)/ZnP/Bodipy), has been prepared by decarbonylation of Os(3)(CO)(8)(CN(CH(2))(3)Si(OEt)(3))(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6) with Me(3)NO/MeCN and subsequent reaction with the isocyanide ligand CNZnP/Bodipy (5) containing zinc porphyrin (ZnP) and boron dipyrrin (Bodipy) moieties. Triad 1 has been characterized by various spectroscopic methods (MS, NMR, IR, UV/Vis, photoluminescence, and transient absorption spectroscopy). The electrochemical properties of 1 in chlorobenzene (CB) have been examined by cyclic voltammetry; the general feature of the cyclic voltammogram of 1 is nine reversible one-electron redox couples, that is, the sum of those of 5 and 6. DFT has been applied to study the molecular and electronic structures of 1. On the basis of fluorescence-lifetime measurements and transient absorption spectroscopic data, 1 undergoes an efficient energy transfer from Bodipy to ZnP and a fast electron transfer from ZnP to C(60); the detailed kinetics involved in both events have been elucidated. The SAM of triad 1 (1/ITO; ITO=indium-tin oxide) has been prepared by immersion of an ITO electrode in a CB solution of 1 and diazabicyclo-octane (2:1 equiv), and characterized by UV/Vis absorption spectroscopy, water contact angle, X-ray photoelectron spectroscopy, and cyclic voltammetry. The photoelectrochemical properties of 1/ITO have been investigated by a standard three-electrode system in the presence of an ascorbic acid sacrificial electron donor. The quantum yield of the photoelectrochemical cell has been estimated to be 29 % based on the number of photons absorbed by the chromophores. Our triad 1 is unique when compared to previously reported photoinduced electron-transfer arrays, in that C(60) is linked by pi bonding with little perturbation of the C(60) electron delocalization.
- Published
- 2010
40. An NMR Study on the Phase Change of Lipid Membranes by an Antimicrobial Peptide, Protegrin-1
- Author
-
Chul Hoon Kim
- Subjects
chemistry.chemical_classification ,Bilayer ,technology, industry, and agriculture ,Peptide ,General Chemistry ,Crystallography ,chemistry.chemical_compound ,Phase change ,Membrane ,Nuclear magnetic resonance ,chemistry ,Phase (matter) ,Protegrin ,lipids (amino acids, peptides, and proteins) ,POPC - Abstract
2H solid-state nuclear magnetic resonance (SSNMR) spectra of 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC_ d31) in the mixture of PG-1 and POPC_d31 lipids deposited on thin cover-glass plates. The experimental line shapes of anisotropic 2 H SSNMR spectra measured at various peptide-to-lipid (P/L) ratios were simulated reasonably by assuming the mosaic spread of bilayers containing pore structures or the coexistence of the mosaic spread of bilayers and a fast-tumbling isotropic phase. Within a few days of incubation in the hydration chamber, the pores were formed by the peptide in the POPC_d31 and POPC_d31/cholesterol membranes. However, the formation of the pores was not clear in the POPC_d31/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG) membrane. Over a hundred days after hydration, a rapidly rotating isotropic phase increased in the POPC_d31 and the POPC_d31/cholesterol membranes with the higher P/L ratios, but no isotropic phase appeared in the POPC_d31/POPG membrane. Cholesterol added in the POPC bilayer acted as a stabilizer of the pore structure and suppressed the formation of a fast-tumbling isotropic phase.
- Published
- 2010
41. The Effects of Kaempferol-Inhibited Autophagy on Osteoclast Formation
- Author
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Bok-Joo Kim, Sang-Hun Shin, In-Ryoung Kim, Hae-Mi Kang, Bong-Soo Park, Jung-Han Kim, Chul-Hoon Kim, and Chang-Ju Kim
- Subjects
0301 basic medicine ,autophagy ,Cellular differentiation ,Osteoclasts ,Apoptosis ,Article ,Catalysis ,Inorganic Chemistry ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,Western blot ,Osteogenesis ,Osteoclast ,Sequestosome-1 Protein ,medicine ,Animals ,MTT assay ,RNA, Messenger ,Bone Resorption ,Kaempferols ,Physical and Theoretical Chemistry ,Molecular Biology ,bone remodeling ,Spectroscopy ,osteoclast differentiation ,medicine.diagnostic_test ,biology ,Chemistry ,RANK Ligand ,Organic Chemistry ,Autophagy ,Acid phosphatase ,bisphosphonate-related osteonecrosis of the jaw (BRONJ) ,Cell Differentiation ,osteoporosis ,flavonoids ,General Medicine ,Computer Science Applications ,Cell biology ,RAW 264.7 Cells ,030104 developmental biology ,medicine.anatomical_structure ,Gene Expression Regulation ,Proteolysis ,biology.protein ,Kaempferol - Abstract
Kaempferol, a flavonoid compound, is derived from the rhizome of Kaempferia galanga L., which is used in traditional medicine in Asia. Autophagy has pleiotropic functions that are involved in cell growth, survival, nutrient supply under starvation, defense against pathogens, and antigen presentation. There are many studies dealing with the inhibitory effects of natural flavonoids in bone resorption. However, no studies have explained the relationship between the autophagic and inhibitory processes of osteoclastogenesis by natural flavonoids. The present study was undertaken to investigate the inhibitory effects of osteoclastogenesis through the autophagy inhibition process stimulated by kaempferol in murin macrophage (RAW 264.7) cells. The cytotoxic effect of Kaempferol was investigated by MTT assay. The osteoclast differentiation and autophagic process were confirmed via tartrate-resistant acid phosphatase (TRAP) staining, pit formation assay, western blot, and real-time PCR. Kaempferol controlled the expression of autophagy-related factors and in particular, it strongly inhibited the expression of p62/SQSTM1. In the western blot and real time-PCR analysis, when autophagy was suppressed with the application of 3-Methyladenine (3-MA) only, osteoclast and apoptosis related factors were not significantly affected. However, we found that after cells were treated with kaempferol, these factors inhibited autophagy and activated apoptosis. Therefore, we presume that kaempferol-inhibited autophagy activated apoptosis by degradation of p62/SQSTM1. Further study of the p62/SQSTM1 gene as a target in the autophagy mechanism, may help to delineate the potential role of kaempferol in the treatment of bone metabolism disorders.
- Published
- 2018
42. LiSc(BH4)4 as a Hydrogen Storage Material: Multinuclear High-Resolution Solid-State NMR and First-Principles Density Functional Theory Studies
- Author
-
Eric H. Majzoub, Houria Kabbour, Son-Jong Hwang, James G. Kulleck, Vidvuds Ozolins, Joseph W. Reiter, Chul Hoon Kim, Jason A. Zan, and Robert C. Bowman
- Subjects
Hydrogen ,Hydride ,chemistry.chemical_element ,Borohydride ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Hydrogen storage ,Crystallography ,chemistry.chemical_compound ,General Energy ,Solid-state nuclear magnetic resonance ,chemistry ,Lithium ,Density functional theory ,Scandium ,Physical and Theoretical Chemistry - Abstract
A lithium salt of anionic scandium tetraborohydride complex, LiSc(BH_4)_4, was studied both experimentally and theoretically as a potential hydrogen storage medium. Ball milling mixtures of LiBH_4 and ScCl_3 produced LiCl and a unique crystalline hydride, which has been unequivocally identified via multinuclear solid-state nuclear magnetic resonance (NMR) to be LiSc(BH_4)_4. Under the present reaction conditions, there was no evidence for the formation of binary Sc(BH_4)_3. These observations are in agreement with our first-principles calculations of the relative stabilities of these phases. A tetragonal structure in space group I (#82) is predicted to be the lowest energy state for LiSc(BH_4)_4, which does not correspond to structures obtained to date on the crystalline ternary borohydride phases made by ball milling. Perhaps reaction conditions are resulting in formation of other polymorphs, which should be investigated in future studies via neutron scattering on deuterides. Hydrogen desorption while heating these Li−Sc−B−H materials up to 400 °C yielded only amorphous phases (besides the virtually unchanged LiCl) that were determined by NMR to be primarily ScB_2 and [B_(12)H_(12)]^(−2) anion containing (e.g., Li_2B_(12)H_(12)) along with residual LiBH_4. Reaction of a desorbed LiSc(BH_4)_4 + 4LiCl mixture (from 4LiBH_4/ScCl_3 sample) with hydrogen gas at 70 bar resulted only in an increase in the contents of Li_2B_(12)H_(12) and LiBH_4. Full reversibility to reform the LiSc(BH_4)_4 was not found. Overall, the Li−Sc−B−H system is not a favorable candidate for hydrogen storage applications.
- Published
- 2009
43. Two-Photon Fluorescent Probes for Biomembrane Imaging: Effect of Chain Length
- Author
-
Bong-Woo Kim, Seung Joon Jeon, Hwan Myung Kim, Bong Rae Cho, Chul Hoon Kim, Hyo-Jung Choo, Taiha Joo, and Young Gyu Ko
- Subjects
Fluorophore ,Analytical chemistry ,Fluorescence Polarization ,Biochemistry ,Cell Line ,Membrane Lipids ,Structure-Activity Relationship ,chemistry.chemical_compound ,Membrane Microdomains ,Two-photon excitation microscopy ,Humans ,Solubility ,Molecular Biology ,Fluorescent Dyes ,Photons ,Aqueous solution ,Molecular Structure ,Chemistry ,Organic Chemistry ,Biological membrane ,Fluorescence ,Microscopy, Fluorescence, Multiphoton ,Membrane ,Biophysics ,Molecular Medicine ,Fluorescence anisotropy - Abstract
Two-photon fluorescent probes for the cellular membrane, derived from 6-acyl-2-aminonaphthalene as the fluorophore and hexanoyl (CH), lauryl (CL), and stearyl (CS) groups as the receptor, have been synthesized. Their photophysical properties and utility as membrane probes were also studied. Whereas CH cannot be used as a membrane probe due to its high water solubility, CL and CS are useful two-photon probes for membrane lateral heterogeneity, as they can easily stain cells, emit fluorescence with high sensitivity to the environment polarity, and are capable of imaging the membrane lateral heterogeneity in live cells. Moreover, CS is more likely to be located in the plasma membrane due to its negligible water solubility. Our results show that the liquid ordered-like domain covers 31-35% of the cellular surface.
- Published
- 2008
44. Lithospermic acid B ameliorates the development of diabetic nephropathy in OLETF rats
- Author
-
Kyu Yeon Hur, Mankil Jung, Seung Jin Han, Hyun Chul Lee, Bong Soo Cha, Gi Ho Seo, Hunjoo Ha, Chul Woo Ahn, Young Soo Ahn, Chul Hoon Kim, Geun Taek Lee, Eun Seok Kang, and Beom Seok Kim
- Subjects
Blood Glucose ,Male ,medicine.medical_specialty ,Rats, Inbred OLETF ,Renal cortex ,Administration, Oral ,Blood Pressure ,Salvia miltiorrhiza ,Type 2 diabetes ,medicine.disease_cause ,Depsides ,Nephropathy ,Lipid peroxidation ,Diabetic nephropathy ,chemistry.chemical_compound ,Aldehyde Reductase ,Internal medicine ,Animals ,Medicine ,Diabetic Nephropathies ,Rats, Long-Evans ,Chemokine CCL2 ,Benzofurans ,Pharmacology ,business.industry ,medicine.disease ,Rats ,Oxidative Stress ,Endocrinology ,medicine.anatomical_structure ,Diabetes Mellitus, Type 2 ,Gene Expression Regulation ,chemistry ,Albuminuria ,medicine.symptom ,business ,Oxidative stress ,Kidney disease - Abstract
Lithospermic acid B (LAB), an active component isolated from Salvia miltiorrhizae, has been reported to have renoprotective effects in type 1 diabetic animal models. In the present study we investigated the effects of LAB on the prevention of diabetic nephropathy in type 2 diabetic Otsuka Long-Evans-Tokushima Fatty (OLETF) rats. LAB (20 mg/kg) was given orally once daily to 10-week-old male OLETF rats for 28 weeks. Treatment of OLETF rats with LAB had little effects on body weight and blood glucose levels. Treatment with LAB resulted in significant reduction in blood pressure. LAB markedly attenuated albuminuria and significantly lowered levels of lipid peroxidation, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-β (TGF-β1) expression in renal tissues of OLETF rats. In addition, LAB inhibited the progression of glomerular hypertrophy, mesangial expansion, and expansion of the extracellular matrix in the renal cortex. Collectively, these results suggest that LAB has beneficial effects on the diabetic nephropathy in OLETF rats by decreasing blood pressure, oxidative stress, and MCP-1 expression. Our results suggest that LAB might be a new therapeutic agent for the prevention of nephropathy in type 2 diabetes.
- Published
- 2008
45. Ultrafast Time-Resolved Laser Spectroscopic Studies of trans-Bis(ferrocene-carboxylato)(tetraphenyl-porphyrinato)tin(IV): Intramolecular Electron-Transfer Dynamics
- Author
-
Minjoong Yoon, Dae Won Cho, Hee Jung Kim, Joon Hee Jang, Taiha Joo, Hee-Joon Kim, and Chul Hoon Kim
- Subjects
chemistry.chemical_compound ,Electron transfer ,Ferrocene ,chemistry ,Excited state ,Intramolecular force ,Ultrafast laser spectroscopy ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Tin ,Porphyrin ,Photoinduced electron transfer - Abstract
Photophysical properties of a newly-synthesized porphyrin derivative, trans-bis(ferrocene carboxylato)-(5,10,15,20-tetraphenylporphyrinato)tin(IV) [Sn(TPP)(FcCOO) 2 ] were investigated by means of steady-state and fs-time resolved laser spectroscopic techniques, and compared with those of a standard molecule, trans-dichloro(5,10,15,20-tetraphenyl-porphrinato)tin(IV) [Sn(TPP)Cl 2 ]. The fluorescence spectrum of Sn(TPP)-(FcCOO) 2 was observed to exhibit dual emission bands originating from the S 2 -state and the S 1 -state, which was greatly quenched as compared to those of Sn(TPP)Cl 2 . The fs-time resolved fluorescence and transient absorption spectroscopic measurements revealed that the fluorescence quenching is due to formation of the long-lived charge transfer state by intramolecular electron transfer from ferrocene to the S 2 -excited SnTPP in addition to the enhanced non-radiative deactivation processes.
- Published
- 2007
46. Perturbation of Electronic States and Energy Relaxation Dynamics in a Series of Phenylene Bridged ZnII Porphyrin Dimers
- Author
-
Min Chul Yoon, Atsuhiro Osuka, Chul Hoon Kim, Naoki Aratani, Dongho Kim, Sung Cho, Goro Mori, and Taiha Joo
- Subjects
chemistry.chemical_compound ,General Energy ,Zinc tetraphenylporphyrin ,Chemistry ,Phenylene ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Physical and Theoretical Chemistry ,Photochemistry ,Porphyrin ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Electronic states - Abstract
We have investigated the perturbed electronic states and energy relaxation dynamics of a series of phenylene bridged ZnII porphyrin dimers to reveal the effects of phenylene bridges by using computational and time-resolved spectroscopic methods. The electronic states of ZnII porphyrin dimers are largely perturbed by the interchromophore interactions that can be controlled by the phenylene bridges; linking position and number of phenyl rings. On the basis of our observations, we can gain further insight into the dipole−dipole interactions and through-bond/through-space electronic exchange interactions between the neighboring porphyrin moieties, which provides a firm basis for further understanding the modification of photophysical properties caused by the phenylene bridge in multiporphyrin assemblies as artificial light-harvesting apparatus.
- Published
- 2007
47. A Two-Photon Fluorescent Probe for Lipid Raft Imaging: C-Laurdan
- Author
-
Young Gyu Ko, Hyo-Jung Choo, Taiha Joo, Bong Rae Cho, Won Hwa Park, Hwan Myung Kim, Chul Hoon Kim, Soonyoung Jung, and Seung Joon Jeon
- Subjects
medicine.disease_cause ,Biochemistry ,chemistry.chemical_compound ,Membrane Microdomains ,Two-photon excitation microscopy ,2-Naphthylamine ,Cell Line, Tumor ,Protein targeting ,Membrane fluidity ,medicine ,Humans ,Molecular Biology ,Lipid raft ,Fluorescent Dyes ,Microscopy ,Photons ,Chemistry ,Vesicle ,Cell Membrane ,Organic Chemistry ,technology, industry, and agriculture ,Water ,Hydrogen-Ion Concentration ,Membrane transport ,Lipids ,Cell biology ,Membrane ,Microscopy, Fluorescence ,Models, Chemical ,Spectrophotometry ,Calibration ,Molecular Medicine ,lipids (amino acids, peptides, and proteins) ,Laurdan ,Laurates - Abstract
The lipid-rafts hypothesis proposes that naturally occurring lipid aggregates exist in the plane of membrane that are involved in signal transduction, protein sorting, and membrane transport. To understand their roles in cell biology, a direct visualization of such domains in living cells is essential. For this purpose, 6-dodecanoyl-2-(dimethylamino)naphthalene (laurdan), a membrane probe that is sensitive to the polarity of the membrane, has often been used. We have synthesized and characterized 6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (C-laurdan), which has the advantages of greater sensitivity to the membrane polarity, a brighter two-photon fluorescence image, and reflecting the cell environment more accurately than laurdan. Lipid rafts can be visualized by two-photon microscopy by using C-laurdan as a probe. Our results show that the lipid rafts cover 38 % of the cell surface.
- Published
- 2007
48. Post-assembly atomic layer deposition of ultrathin metal-oxide coatings enhances the performance of an organic dye-sensitized solar cell by suppressing dye aggregation
- Author
-
Ho-Jin Son, Omar K. Farha, Nak Cheon Jeong, Michael R. Wasielewski, Chaiya Prasittichai, Joseph T. Hupp, Langli Luo, Jinsong Wu, Chul Hoon Kim, and Dong Wook Kim
- Subjects
Materials science ,Energy conversion efficiency ,Oxide ,Photochemistry ,law.invention ,Metal ,chemistry.chemical_compound ,Atomic layer deposition ,chemistry ,law ,visual_art ,Solar cell ,visual_art.visual_art_medium ,Energy transformation ,General Materials Science ,Spectroscopy ,Acrylic acid - Abstract
Dye aggregation and concomitant reduction of dye excited-state lifetimes and electron-injection yields constitute a significant mechanism for diminution of light-to-electrical energy conversion efficiencies in many dye-sensitized solar cells (DSCs). For TiO2-based DSCs prepared with an archetypal donor-acceptor organic dye, (E)-2-cyano-3-(5'-(5''-(p-(diphenylamino)phenyl)-thiophen-2''-yl)thiophen-2'-yl)acrylic acid (OrgD), we find, in part via ultrafast spectroscopy measurements, that postdye-adsorption atomic layer deposition (ALD) of ultrathin layers of either TiO2 or Al2O3 effectively reverses residual aggregation. Notably, the ALD treatment is significantly more effective than the widely used aggregation-inhibiting coadsorbent, chenodeoxycholic acid. Primarily because of reversal of OrgD aggregation, and resulting improved injection yields, ALD post-treatment engenders a 30+% increase in overall energy conversion efficiency. A secondary contributor to increased currents and efficiencies is an ALD-induced attenuation of the rate of interception of injected electrons, resulting in slightly more efficient charge collection.
- Published
- 2015
49. A Study on the Effect of Neighboring Protons in Proton-Coupled Spin-Lattice Relaxation of Methylene Carbon-13 in n-Undecane
- Author
-
Jo Woong Lee and Chul Hoon Kim
- Subjects
chemistry.chemical_compound ,Crystallography ,Nuclear magnetic resonance ,chemistry ,Proton ,Carbon-13 ,Spin–lattice relaxation ,Relaxation (physics) ,Moiety ,General Chemistry ,Methylene ,Undecane ,Vicinal - Abstract
Proton coupled carbon-13 relaxation experiment was performed to investigate the effect of vicinal protons on spin-lattice relaxation of methylene carbon-13 in n-undecane. A BIRD type pulse sequence was employed as a way to check the validity of describing the 1 3 CH 2 moiety as an isolated AX 2 spin system. The results show that the presence of vicinal protons exerts substantial influence on the relaxation of methylene carbon-13, indicating that it is not a very good approximation to treat a methylene moiety as an isolated AX 2 spin system.
- Published
- 2002
50. Human hepatocellular carcinoma cells resist to TRAIL-induced apoptosis, and the resistance is abolished by cisplatin
- Author
-
Eui-Cheol Shin, Seung Suh Hong, Chul Hoon Kim, Young Soo Ahn, Hoguen Kim, Se Jong Kim, Jeon Han Park, Kunhong Kim, and Young Rim Seong
- Subjects
Carcinoma, Hepatocellular ,Clinical Biochemistry ,CASP8 and FADD-Like Apoptosis Regulating Protein ,Apoptosis ,Cycloheximide ,Biochemistry ,Receptors, Tumor Necrosis Factor ,Cell Line ,TNF-Related Apoptosis-Inducing Ligand ,chemistry.chemical_compound ,medicine ,Humans ,Decoy receptors ,Receptor ,Molecular Biology ,Sensitization ,Cisplatin ,Membrane Glycoproteins ,Tumor Necrosis Factor-alpha ,Chemistry ,Intracellular Signaling Peptides and Proteins ,NF-kappa B ,medicine.disease ,Cell biology ,medicine.anatomical_structure ,Cell culture ,Hepatocellular carcinoma ,Cancer research ,Molecular Medicine ,Apoptosis Regulatory Proteins ,Carrier Proteins ,Peptides ,medicine.drug - Abstract
TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF family, selectively induce apoptosis in various transformed cell lines but not in almost-normal tissues. It is regulated by 2 death receptors, TRAIL receptor 1 (TRAIL-R1) and TRAIL-R2 and 2 decoy receptors, TRAIL-R3 and TRAIL-R4. However, the determining factors of the sensitivity to TRAIL-induced apoptosis are not clearly understood. Herein, we investigated the expression of TRAIL-R, c-FLIP, FADD-like interleukin-1beta-converting enzyme inhibitory protein, and TRAIL-induced apoptosis in human hepatocellular carcinoma (HCC) cell lines. Seven of ten HCC cell lines showed resistance to TRAIL-induced apoptosis and five of seven TRAIL-resistant cell lines became sensitive to TRAIL by co-treatment with cycloheximide. In HCC cell lines, their TRAIL resistance did not correlate with the basal expression level of TRAIL receptors or c-FLIP, however, in human tissues, TRAIL-R1 and TRAIL-R2 expressions were notably decreased compared to normal counterpart. Cisplatin showed synergistic effect on TRAIL-induced apoptosis in most HCC cell lines regardless of their p53 status and TRAIL-R1 was induced by cisplatin treatment in certain cell lines. Inhibition of nuclear factor K B (NF-kappaB) by SN50, a peptide inhibitor of NF-KB activity, had no effect on TRAIL-induced apoptosis in HCC cells. These results suggest that (a) the majority of human HCC cell lines are resistant to TRAIL-induced apoptosis and cycloheximide-sensitive short-lived antiapoptotic molecule(s) is responsible for this resistance, (b) the expression of TRAIL-R1 and TRAIL-R2 is reduced in HCC tissues, and the increased expression of TRAIL-R1 may be a mechanism of cisplatininduced sensitization to TRAIL-induced apoptosis in some HCC cells, and (c) the activation of NF-kappaB may not be involved in the TRAIL resistance of HCC cells
- Published
- 2002
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