199 results on '"Koo Shin"'
Search Results
2. Label-free measurement of the yeast short chain TAG lipase activity by ESI-MS after one-step esterification
- Author
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Hye Jin Ham, Jongcheol Seo, Hye-Joo Yoon, and Seung Koo Shin
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chemical derivatization ,triacylglycerol ,lipolysis ,specific activity ,electrospray ionization-mass spectrometry ,Biochemistry ,QD415-436 - Abstract
Triacylglycerol (TAG) lipases hydrolyze ester bonds in TAG and release diacylglycerol (DAG), monoacylglycerol (MAG), and FA. We present a one-step chemical derivatization method for label-free quantification of a mixture of TAG, DAG, and MAG following lipase assay by ESI-MS. Because the ionization efficiencies of TAG, DAG, and MAG are not identical, lipase reaction products, DAG and MAG, are derivatized to TAG species by esterifying their hydroxyl groups using acyl chloride, whose acyl chain contains one less (or one more) –CH2 group than that of substrate TAG. This resulted in three TAG species that were separated by 14 Da from one another and exhibited similar ion responses representing their molar amounts in the mass spectra. A good linear correlation was observed between peak intensity ratios and molar ratios in calibration curve. This method enables simultaneous quantification of TAG, DAG, and MAG in lipase assay and, in turn, allows stoichiometric determination of the concentrations of FAs released from TAG and DAG separately. By applying this strategy to measure both TAG and DAG lipolytic activities of the yeast Tgl2 lipase, we demonstrated its usefulness in studying enzymatic catalysis, as lipase enzymes often show dissimilar activities toward these lipids.
- Published
- 2017
- Full Text
- View/download PDF
3. In Situ-Forming Collagen/poly-γ-glutamic Acid Hydrogel System with Mesenchymal Stem Cells and Bone Morphogenetic Protein-2 for Bone Tissue Regeneration in a Mouse Calvarial Bone Defect Model
- Author
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Sun-Hee Cho, Keun Koo Shin, Sun-Young Kim, Mi Young Cho, Doo-Byoung Oh, and Yong Taik Lim
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Bone Regeneration ,Biomedical Engineering ,Glutamic Acid ,Medicine (miscellaneous) ,Hydrogels ,Mesenchymal Stem Cells ,X-Ray Microtomography ,Acridine Orange ,Mice ,Polyglutamic Acid ,Osteogenesis ,Animals ,Original Article ,Collagen ,Propidium - Abstract
BACKGROUND: Bone marrow-derived mesenchymal stem cells (BMSCs) and bone morphogenetic protein-2 (BMP-2) have been studied for bone repair because they have regenerative potential to differentiate into osteoblasts. The development of injectable and in situ three-dimensional (3D) scaffolds to proliferate and differentiate BMSCs and deliver BMP-2 is a crucial technology in BMSC-based tissue engineering. METHODS: The proliferation of mouse BMSCs (mBMSCs) in collagen/poly-γ-glutamic acid (Col/γ-PGA) hydrogel was evaluated using LIVE/DEAD and acridine orange and propidium iodide assays. In vitro osteogenic differentiation and the gene expression level of Col/γ-PGA(mBMSC/BMP-2) were assessed by alizarin red S staining and quantitative reverse-transcription polymerase chain reaction. The bone regeneration effect of Col/γ-PGA(mBMSC/BMP-2) was evaluated in a mouse calvarial bone defect model. The cranial bones of the mice were monitored by micro-computed tomography and histological analysis. RESULTS: The developed Col/γ-PGA hydrogel showed low viscosity below ambient temperature, while it provided a high elastic modulus and viscous modulus at body temperature. After gelation, the Col/γ-PGA hydrogel showed a 3D and interconnected porous structure, which helped the effective proliferation of BMSCs with BMP-2. The Col/γ-PGA (mBMSC/BMP-2) expressed more osteogenic genes and showed effective orthotopic bone formation in a mouse model with a critical-sized bone defect in only 3–4 weeks. CONCLUSION: The Col/γ-PGA(mBMSC/BMP-2) hydrogel was suggested to be a promising platform by combining collagen as a major component of the extracellular matrix and γ-PGA as a viscosity reducer for easy handling at room temperature in BMSC-based bone tissue engineering scaffolds. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13770-022-00454-4.
- Published
- 2022
4. miR-137 Controls Proliferation and Differentiation of Human Adipose Tissue Stromal Cells
- Author
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Keun Koo Shin, Young Suk Kim, Jee Young Kim, Yong Chan Bae, and Jin Sup Jung
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miR-137 ,Adipogenic differentiation ,Proliferation ,MicroRNA ,hADSC ,Physiology ,QP1-981 ,Biochemistry ,QD415-436 - Abstract
Background/Aims: Demonstrating the molecular mechanisms of human adipose tissue-derived mesenchymal stem cells (hADSCs) differentiation and proliferation could develop hADSCs-based cell therapy. Methods: The microRNA-137 (miR-137) and cell division control protein 42 homolog (CDC42) levels were regulated by oligonucleotides transfection. The adipogenic differentiation was induced for 10 days in an adipogenic medium and assessed by using an Oil Red O stain. The regulation of miR-137 on CDC42 expression was determined by western blot, real-time PCR and luciferase reporter assay. Results: We confirmed the roles of miR-137 on hADSCs proliferation and adipogenic differentiation. We showed that overexpression of miR-137 inhibited both hADSCs proliferation and adipogenic differentiation. Overexpression of miR-137 also downregulated protein and mRNA levels of CDC42, a predicted target of miR-137. In contrast, inhibition of miR-137 with 2'-O-methyl antisense RNA increased proliferation and adipogenic differentiation in hADSCs. Luciferase reporter activity in the miR-137 target site within the CDC42 3'UTR was lower in miR-137-transfected hADSCs than in control miRNA-transfected hADSCs. RNA interference-mediated downregulation of CDC42 in hADSCs inhibited their proliferation and adipogenic differentiation. Conclusion: Our results indicate that miR-137 regulates hADSCs adipogenic differentiation and proliferation by directly targeting CDC42. These findings improve our knowledge of the molecular mechanisms governing hADSCs differentiation and proliferation.
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- 2014
- Full Text
- View/download PDF
5. Antibody-secreting macrophages generated using CpG-free plasmid eliminate tumor cells through antibody-dependent cellular phagocytosis
- Author
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Doo-Byoung Oh, Keun Koo Shin, Jin-Ho Seo, and Eun Bi Cha
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Male ,Transgene ,Mice, Nude ,Transfection ,Biochemistry ,Article ,Mice ,03 medical and health sciences ,Plasmid ,Antibody-secreting macrophage ,Cell Line, Tumor ,Neoplasms ,Antibody-dependent cellular phagocytosis ,Animals ,Humans ,Viability assay ,Vector (molecular biology) ,Molecular Biology ,Gene ,CpG-free plasmid ,0303 health sciences ,biology ,Chemistry ,Macrophages ,030302 biochemistry & molecular biology ,Genes, erbB-1 ,General Medicine ,Xenograft Model Antitumor Assays ,Cell biology ,ErbB Receptors ,RAW 264.7 Cells ,CpG site ,Cytophagocytosis ,Nonviral gene delivery ,biology.protein ,Heterografts ,CpG Islands ,Antibody ,Plasmids ,Single-Chain Antibodies - Abstract
The non-viral delivery of genes into macrophages, known as hard-to-transfect cells, is a challenge. In this study, the microporation of a CpG-free and small plasmid (pCGfd-GFP) showed high transfection efficiency, sustainable transgene expression, and good cell viability in the transfections of Raw 264.7 and primary bone marrow-derived macrophages. The non-viral method using the pCGfd vector encoding anti-EGFR single-chain Fv fused with Fc (scFv-Fc) generated the macrophages secreting anti-EGFR scFv-Fc. These macrophages effectively phagocytized tumor cells expressing EGFR through the antibody-dependent mechanism, as was proved by experiments using EGFR-knockout tumor cells. Finally, peri-tumoral injections of anti-EGFR scFv-Fc-secreting macrophages were shown to inhibit tumor growth in the xenograft mouse model. [BMB Reports 2020; 53(8): 442-447].
- Published
- 2020
6. Phytic Acid-Doped Cross-linked Polyaniline Nanofibers for Electrochemical Supercapacitor Electrode Applications
- Author
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Hyeong Jin Kim, Hu Young Jeong, Koo Shin, Young Joon Hong, Won G. Hong, Kyungjung Kwon, and Sungjin Im
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010302 applied physics ,Supercapacitor ,Materials science ,Polyaniline nanofibers ,Doping ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,chemistry.chemical_compound ,Chemical engineering ,Polymerization ,chemistry ,Nanofiber ,0103 physical sciences ,Electrode ,Polyaniline ,0210 nano-technology - Abstract
Electrochemical energy storage characteristics of chlorine- and phytic acid-doped polyaniline nanofibers (Cl- and Ph-PAni NFs), which were synthesized via radical polymerization in a hydrochloric acid and a Ph solution, respectively, were comparatively investigated. The Ph-PAni NFs showed a specific capacitance of 227 F g−1, which was two times higher than the value of 105 F g−1 for Cl-PAni NFs at 30 A g−1, due to the enhanced electrical conductivity caused by Ph doping. Moreover, the Ph-PAni NFs presented superior supercapacitor electrode performances in terms of charge-discharge cycle life, specific power, and electrochemical impedance. Diverse spectroscopic analyses revealed that the Ph doping contributed to formation of crosslinks between PAni backbones, which eventually provided many effective electrical conducting paths in the NFs. Thus, the high conductivity is responsible for the high electrochemical activity of Ph-PAni NFs. This approach to increase the electrochemical performances is expected to be applied to other conducting polymeric supercapacitor electrodes for more practical device applications.
- Published
- 2019
7. Effects of intramolecular hydrogen bonds on the collision-induced dissociation of tryptic peptide ions
- Author
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Seung Koo Shin, Hye-Joo Yoon, and Jongcheol Seo
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Collision-induced dissociation ,Hydrogen bond ,Stereochemistry ,Electrospray ionization ,010401 analytical chemistry ,010402 general chemistry ,Condensed Matter Physics ,Mass spectrometry ,01 natural sciences ,Dissociation (chemistry) ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Amide ,Intramolecular force ,Side chain ,Physical and Theoretical Chemistry ,Instrumentation ,Spectroscopy - Abstract
The protonated basic side chains in tryptic peptide ions can form intramolecular hydrogen bonds with backbone amide carbonyls, which inhibit the backbone cleavage and hinder the peptide sequencing using mass spectrometry. To study the strength of intramolecular hydrogen bonds and its effect on the backbone cleavage, we carried out the energy-dependent collision-induced dissociation (CID) of tryptic peptides and their modified ones. The N-acylation of lysine-terminated peptides was used to convert the primary amines at both lysine and the N-terminus into amides in order to block the primary protonation sites. The guanidination was employed to transform lysine into homoarginine in order to imitate arginine-terminated peptides. Then, N-acylation was applied to the guanidinated peptides to prepare N-acylated, homoarginine-terminated peptides. Singly charged peptide ions were generated by electrospray ionization in a Q-TOF instrument and their CID spectra were obtained as a function of collision energy under nearly single-collision conditions with Xe as the target gas. The energy-dependent survival yield of the precursor ion provided information on the change in dissociation energy of peptides after chemical modifications. We also identified possible sites and numbers of hydrogen bonds that stabilized a charge-solvated structure by comparing the variation in product yields with the location of backbone cleavage. By taking these data together, we estimated the relative strength of intramolecular hydrogen bonds formed in lysine- and homoarginine-terminated peptides before and after N-acylation. Our results demonstrate that N-acylation lowers the dissociation energy of tryptic peptides and facilitates the backbone cleavage by preventing the formation of intramolecular hydrogen bonds, enabling accurate identification of peptides.
- Published
- 2019
8. Recyclable aqueous metal adsorbent: Synthesis and Cu(II) sorption characteristics of ternary nanocomposites of Fe
- Author
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Hyeong Jin, Kim, Hyuk, Choi, Abhishek Kumar, Sharma, Won G, Hong, Koo, Shin, Hocheol, Song, Hyun You, Kim, and Young Joon, Hong
- Abstract
Metal pollutant adsorbents are an essential material platform for sustainable environmental remediation, but the adsorbents are typically disposable after sorption, which secondarily contaminates the environment. We report on recyclable Cu(II) adsorbent of deprotonated poly-N-phenylglycine nanofibers (d-PPG NFs)-grafted reduced graphene oxide (rGO) sheets intercalated with Fe
- Published
- 2020
9. Charge–dipole interactions in G-quadruplex thrombin-binding aptamer
- Author
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Hyun Woo Kim, Seung Koo Shin, and Young Min Rhee
- Subjects
0301 basic medicine ,Cation binding ,Guanine ,Static Electricity ,Stacking ,General Physics and Astronomy ,Molecular Dynamics Simulation ,010402 general chemistry ,G-quadruplex ,01 natural sciences ,Ion ,03 medical and health sciences ,Non-covalent interactions ,Molecule ,Physical and Theoretical Chemistry ,chemistry.chemical_classification ,Ionic radius ,Molecular Structure ,Chemistry ,Hydrogen bond ,Hydrogen Bonding ,Aptamers, Nucleotide ,0104 chemical sciences ,G-Quadruplexes ,Crystallography ,030104 developmental biology ,Strontium ,Potassium ,Quantum Theory ,Thermodynamics - Abstract
DNAs form various structures through hydrogen-bonding, base-stacking and electrostatic interactions. Although these noncovalent interactions are known to be cooperative in stabilizing a G-quadruplex (G4) structure of DNA, we find from all-atom molecular dynamics simulations that the electrostatic charge-dipole interaction is competitive with both hydrogen-bonding and base-stacking interactions. For the thrombin-binding aptamer (TBA) forming a chair-type antiparallel G4 structure, we have examined effects of an intercalating metal ion [K+, Sr2+, Mn+: an ion having a charge of n+ (n = 1-4) with the ionic radius of K+] on structural properties and noncovalent interactions. When K+ in the TBA·K+ complex is replaced with Sr2+, guanine dipoles in the two G-tetrads are realigned toward the central metal ion, thereby distorting the planar G4 geometry. Replacing K+ with Sr2+ significantly enhances the charge-dipole interaction but substantially reduces the number of hydrogen bonds in the G-tetrads. In the case of TBA·Mn+ complexes, as the charge n increases, the charge-dipole interaction increases but both of the hydrogen-bonding and base-stacking interactions decrease. These results suggest that the charge-dipole interaction realigning guanine dipoles in the G-tetrads is not cooperative but competitive with both hydrogen-bonding and base-stacking interactions favoring the planar G-tetrad geometry. Obviously, the charge state of an intercalating metal ion is as important as the ionic radius in forming a stable G4 structure. Thus, a delicate balance between these competing noncovalent interactions makes the chair-type antiparallel G4 structure of TBA selective for intercalating metal ions.
- Published
- 2018
10. Optical properties of colloidal semiconductor quantum dots in dielectric media: A natural potential well approach
- Author
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Seung Koo Shin and Hwajun Jeong
- Subjects
Materials science ,Condensed matter physics ,Condensed Matter::Other ,business.industry ,Physics::Optics ,General Physics and Astronomy ,Heterojunction ,02 engineering and technology ,Dielectric ,Interaction energy ,Electron ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Kinetic energy ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Semiconductor ,Quantum dot ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Quantum - Abstract
Colloidal quantum dots exhibit size-dependent optical properties due to quantum and dielectric confinements at the semiconductor/solvent boundary. To consider both confinement effects, we take a natural potential well approach that assumes separate potential wells for electron and hole which are surrounded by dielectric media. The potential well depths for electron and hole are set by the band offsets at the semiconductor/solvent heterojunction. The kinetic energy is calculated using an effective mass approximation and the electron-hole interaction energy is obtained by taking image charges into account. For cadmium chalcogenides, resulting transition energies agree well with size-dependent optical bandgaps from experiments.
- Published
- 2018
11. Crucial role of three-center hydrogen bonding in a challenging chiral molecular recognition
- Author
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Sung-Gon Kim, Kyung-Hyun Kim, Young Kook Kim, Seung Koo Shin, and Kyo Han Ahn
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Ammonium chloride -- Analysis ,Ammonium paratungstate -- Analysis ,Ammonium compounds -- Analysis ,Chirality -- Analysis ,Hydrogen bonding -- Usage ,Chemistry - Abstract
The role of the three-center (bifurcated) hydrogen bonding in chiral molecular recognition is studied with special emphasize on the enantio-discrimination of the beta-chiral primary ammonium ions using a rational approach. Results show that the bifurcated hydrogen bonding plays a very important role in the chiral discrimination.
- Published
- 2003
12. Self-assembled monolayer of L-Cysteine on Au(111): hydrogen exchange between zwitterionic L-cysteine and physisorbed water
- Author
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Taeho Shin, Keun-Nam Kim, Chang-Woo Lee, Seung Koo Shin, and Heon Kang
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Gold -- Research ,Gold -- Chemical properties ,Monomolecular films -- Research ,Monomolecular films -- Chemical properties ,Monomolecular films -- Magnetic properties ,Chemicals, plastics and rubber industries - Abstract
A self-assembled monolayer (SAM) of L-cysteine was prepared on Au (111) surface by vapor deposition in ultrahigh vacuum and was characterized by techniques of temperature-programmed desorption (TDP). Analysis indicates that L-cysteine molecules existed in the zwitterionic form.
- Published
- 2003
13. Phytic Acid Doped Polyaniline Nanofibers for Enhanced Aqueous Copper(II) Adsorption Capability
- Author
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Young Joon Hong, Hyeong Jin Kim, Hu Young Jeong, Sungjin Im, Won G. Hong, Koo Shin, and Jong Chan Kim
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Phytic acid ,Aqueous solution ,Polyaniline nanofibers ,Renewable Energy, Sustainability and the Environment ,General Chemical Engineering ,Inorganic chemistry ,Radical polymerization ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Adsorption ,Deprotonation ,chemistry ,Polyaniline ,Environmental Chemistry ,0210 nano-technology ,Bimetallic strip ,Nuclear chemistry - Abstract
This study demonstrates the enhanced Cu2+ adsorption capability of polyaniline nanofibers (PAni NFs) by doping of phytic acid. The PAni NFs were synthesized by radical polymerization process using acidic solutions of hydrochloric and phytic acid, yielding chlorinated (Cl-) and phytic acid-doped (Ph-) PAni NFs. The Ph-PAni NFs showed remarkably higher Cu2+-adsorption efficiency than Cl-PAni NFs, presumably owing to high capacity and/or high ionic affinity of the doped phytic acid in Ph-PAni NFs. The pH-dependent adsorption capability exhibited increasing Cu2+ adsorption trend as increasing aqueous pH because of spontaneous deprotonation of the doped phytic acid in a basic environment. Furthermore, Ph-PAni NFs showed stable, high Cu2+ adsorption capability, irrespective of Co2+ concentration in the bimetallic Cu and Co aqueous solution. Surface morphologies of PAni NFs were investigated using electron microscopy, and molecular structures were identified using X-ray photoemission and Fourier transform infrar...
- Published
- 2017
14. Abolishment of N-glycan mannosylphosphorylation in glyco-engineered Saccharomyces cerevisiae by double disruption of MNN4 and MNN14 genes
- Author
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Ji-Yeon Kang, Jeong-Yoon Kim, Yeong Hun Kim, Ohsuk Kwon, Doo-Byoung Oh, Sang-Yoon Kim, Keun Koo Shin, Jin Young Gil, and Hyun Ah Kang
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0301 basic medicine ,Glycan ,Saccharomyces cerevisiae Proteins ,Saccharomyces cerevisiae ,Mutant ,Biology ,Mannosyltransferases ,Applied Microbiology and Biotechnology ,03 medical and health sciences ,Cell Wall ,Polysaccharides ,Humans ,Phosphorylation ,Gene ,chemistry.chemical_classification ,Mannosephosphates ,Membrane Glycoproteins ,030102 biochemistry & molecular biology ,Membrane Proteins ,General Medicine ,biology.organism_classification ,Recombinant Proteins ,Yeast ,carbohydrates (lipids) ,Membrane glycoproteins ,030104 developmental biology ,Metabolic Engineering ,Membrane protein ,Biochemistry ,chemistry ,biology.protein ,Glycoprotein ,Mannose ,Biotechnology - Abstract
Mannosylphosphorylated glycans are found only in fungi, including yeast, and the elimination of mannosylphosphates from glycans is a prerequisite for yeast glyco-engineering to produce human-compatible glycoproteins. In Saccharomyces cerevisiae, MNN4 and MNN6 genes are known to play roles in mannosylphosphorylation, but disruption of these genes does not completely remove the mannosylphosphates in N-glycans. This study was performed to find unknown key gene(s) involved in N-glycan mannosylphosphorylation in S. cerevisiae. For this purpose, each of one MNN4 and five MNN6 homologous genes were deleted from the och1Δmnn1Δmnn4Δmnn6Δ strain, which lacks yeast-specific hyper-mannosylation and the immunogenic α(1,3)-mannose structure. N-glycan profile analysis of cell wall mannoproteins and a secretory recombinant protein produced in mutants showed that the MNN14 gene, an MNN4 paralog with unknown function, is essential for N-glycan mannosylphosphorylation. Double disruption of MNN4 and MNN14 genes was enough to eliminate N-glycan mannosylphosphorylation. Our results suggest that the S. cerevisiae och1Δmnn1Δmnn4Δmnn14Δ strain, in which all yeast-specific N-glycan structures including mannosylphosphorylation are abolished, may have promise as a useful platform for glyco-engineering to produce therapeutic glycoproteins with human-compatible N-glycans.
- Published
- 2017
15. Halogen−π Interactions between Benzene and X2/CX4 (X = Cl, Br): Assessment of Various Density Functionals with Respect to CCSD(T)
- Author
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Joonho Lee, Michael Filatov, Jenica Marie L. Madridejos, Il Seung Youn, Maciej Kołaski, Chunggi Baig, Seung Koo Shin, Han Myoung Lee, Dong Yeon Kim, Woo Jong Cho, and Kwang S. Kim
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Halogen bond ,010304 chemical physics ,Chemistry ,Supramolecular chemistry ,Aromaticity ,Interaction energy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Crystallography ,Computational chemistry ,0103 physical sciences ,Halogen ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,Conformational isomerism - Abstract
Various types of interactions between halogen (X) and π moiety (X−π interaction) including halogen bonding play important roles in forming the structures of biological, supramolecular, and nanomaterial systems containing halogens and aromatic rings. Furthermore, halogen molecules such as X2 and CX4 (X = Cl/Br) can be intercalated in graphite and bilayer graphene for doping and graphene functionalization/modification. Due to the X−π interactions, though recently highly studied, their structures are still hardly predictable. Here, using the coupled-cluster with single, double, and noniterative triple excitations (CCSD(T)), the Moller–Plesset second-order perturbation theory (MP2), and various flavors of density functional theory (DFT) methods, we study complexes of benzene (Bz) with halogen-containing molecules X2 and CX4 (X = Cl/Br) and analyze various components of the interaction energy using symmetry adapted perturbation theory (SAPT). As for the lowest energy conformers (S1), X2–Bz is found to have the...
- Published
- 2016
16. A Clinical case study about the Effects of Oryeong-san Gamibang on Case of Functional diarrhea
- Author
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Min-koo Shin, Young-su Lee, and Eui-su Kim
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Bowel sounds ,medicine.medical_specialty ,business.industry ,Internal medicine ,Medicine ,Functional diarrhea ,Clinical case ,business ,Intensive care medicine ,Gastroenterology - Published
- 2016
17. Enhanced adsorption of aqueous copper(II) ions using dedoped poly-N-phenylglycine nanofibers
- Author
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Koo Shin, Young Joon Hong, Rana Faryad Ali, Ji Hyun Kim, Ji Hoon Doh, and Hyeong Jin Kim
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chemistry.chemical_classification ,Aqueous solution ,Chemistry ,General Chemical Engineering ,Carboxylic acid ,Inorganic chemistry ,Radical polymerization ,General Chemistry ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,Deprotonation ,Adsorption ,Basic solution ,Environmental Chemistry ,Surface modification ,Carboxylate - Abstract
We report on adsorption of aqueous Cu2+ using poly N-phenylglycine (PPG) nanofibers (NFs) prepared by radical polymerization process. The carboxylic acid groups of pristine PPG NFs were deprotonated to form carboxylate groups, resulting in hydrogen-dedoped PPG NFs. The Cu2+-adsorption capability of PPG NFs was markedly increased after the deprotonation, presumably due to high ionic attraction feature of carboxylate in dedoped PPG. We further investigated the pH-dependent adsorption capability of PPG NFs and found much higher Cu2+ adsorption capacity under high pH conditions, owing to spontaneous deprotonation by the basic solution. X-ray photoemission confirmed the adsorption of Cu2+ on PPG NFs, and Fourier transform infrared spectroscopic analyses confirmed the reduced density of carboxylic acid by deprotonation. The ability of pristine and dedoped PPG NFs to capture aqueous Cu2+ is discussed. Our method to improve the adsorption capability using surface modification could be readily applied to many other polymeric or organic nanostructures for metal removal.
- Published
- 2015
18. A Photoetching‐After‐Growth Approach for the Synthesis of Nanocrystal Heterostructures Exhibiting Tunable Dual‐Band Emission
- Author
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Wonjung Kim, Seung Koo Shin, and Sung Jun Lim
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Materials science ,Nanocrystal ,Mechanics of Materials ,business.industry ,Mechanical Engineering ,Optoelectronics ,Heterojunction ,Multi-band device ,business - Published
- 2019
19. Lysosomal Targeting Enhancement by Conjugation of Glycopeptides Containing Mannose-6-phosphate Glycans Derived from Glyco-engineered Yeast
- Author
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Ji-Yeon Kang, Ohsuk Kwon, Jeong-Ki Min, Ha Hyung Kim, Doo-Byoung Oh, Jin Young Kim, Eun Sun Ji, and Keun Koo Shin
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0301 basic medicine ,Glycan ,Glycosylation ,lcsh:Medicine ,Mannose ,Saccharomyces cerevisiae ,Pronase ,Mannose 6-phosphate ,Article ,03 medical and health sciences ,chemistry.chemical_compound ,Lysosome ,medicine ,Humans ,lcsh:Science ,chemistry.chemical_classification ,Mannosephosphates ,Multidisciplinary ,biology ,lcsh:R ,Glycopeptides ,alpha-Glucosidases ,Recombinant Proteins ,Yeast ,030104 developmental biology ,Enzyme ,medicine.anatomical_structure ,Metabolic Engineering ,chemistry ,Biochemistry ,biology.protein ,lcsh:Q ,Microorganisms, Genetically-Modified ,Lysosomes - Abstract
Many therapeutic enzymes for lysosomal storage diseases require a high content of mannose-6-phosphate (M6P) glycan, which is important for cellular uptake and lysosomal targeting. We constructed glyco-engineered yeast harboring a high content of mannosylphosphorylated glycans, which can be converted to M6P glycans by uncapping of the outer mannose residue. In this study, the cell wall of this yeast was employed as a natural M6P glycan source for conjugation to therapeutic enzymes. The extracted cell wall mannoproteins were digested by pronase to generate short glycopeptides, which were further elaborated by uncapping and α(1,2)-mannosidase digestion steps. The resulting glycopeptides containing M6P glycans (M6PgPs) showed proper cellular uptake and lysosome targeting. The purified M6PgPs were successfully conjugated to a recombinant acid α-glucosidase (rGAA), used for the treatment of Pompe disease, by two-step reactions using two hetero-bifunctional crosslinkers. First, rGAA and M6PgPs were modified with crosslinkers containing azide and dibenzocyclooctyne, respectively. In the second reaction using copper-free click chemistry, the azide-functionalized rGAA was conjugated with dibenzocyclooctyne-functionalized M6PgPs without the loss of enzyme activity. The M6PgP-conjugated rGAA had a 16-fold higher content of M6P glycan than rGAA, which resulted in greatly increased cellular uptake and efficient digestion of glycogen accumulated in Pompe disease patient fibroblasts.
- Published
- 2018
20. Solution-processed quantum dot light-emitting diodes with PANI:PSS hole-transport interlayers
- Author
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Koo Shin, Young-Soo Seo, Ji Hoon Doh, Soo Young Kim, Yunseok Kim, Young Ran Park, Young Joon Hong, and Won Kook Choi
- Subjects
Materials science ,business.industry ,General Chemistry ,Electroluminescence ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,chemistry.chemical_compound ,chemistry ,PEDOT:PSS ,Quantum dot ,law ,Polyaniline ,Materials Chemistry ,Optoelectronics ,Work function ,Electrical and Electronic Engineering ,business ,Solution process ,Ultraviolet photoelectron spectroscopy ,Light-emitting diode - Abstract
For solution-processed quantum dot light-emitting devices (QD-LEDs), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/poly(N-vinylcarbozole) (PEDOT:PSS/PVK) bilayers have been widely used as the hole injection/transport layer. The high work function of the hole transport layer is crucial for high electroluminescence efficiency with balanced electron/hole charge injection. Herein, we report improvement of the performance of QD-LEDs by inserting a polyaniline (PANI)-poly (p-styrenesulfonic acid) (PSS) (PANI:PSS) hole-transport layer between the PVK and PEDOT:PSS layers. The insertion of the PANI:PSS layer significantly shifted the electronic energy levels of the PVK layers to lower values, which reduced the energy barrier of holes traveling to the QD layer by 0.22 eV. The QD-LEDs with PANI:PSS interlayer exhibited superior electric and electroluminescent characteristics. The hole-only devices with PANI:PSS interlayer also presented high hole injection and transport capability. Ultraviolet photoelectron spectroscopy (UPS) was used to investigate the electronic energy level alignment of the QD-LEDs with/without the PANI:PSS interlayer. The device performance results of QD-LEDs and hole-only devices indicated enhanced electric and electroluminescent characteristics for the PANI:PSS-inserted QD-LEDs with high hole conduction capability, in agreement with UPS findings.
- Published
- 2015
21. Label-free measurement of the yeast short chain TAG lipase activity by ESI-MS after one-step esterification[S]
- Author
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Seung Koo Shin, Hye Jin Ham, Hye-Joo Yoon, and Jongcheol Seo
- Subjects
0301 basic medicine ,Electrospray ionization ,QD415-436 ,Saccharomyces cerevisiae ,Biochemistry ,Catalysis ,Enzyme catalysis ,Diglycerides ,03 medical and health sciences ,chemistry.chemical_compound ,Endocrinology ,Acyl chloride ,Methods ,Lipase ,Derivatization ,Triglycerides ,Diacylglycerol kinase ,Chromatography ,biology ,Esterification ,urogenital system ,Hydrolysis ,Substrate (chemistry) ,Cell Biology ,specific activity ,Lipids ,Monoacylglycerol lipase ,030104 developmental biology ,chemistry ,electrospray ionization-mass spectrometry ,biology.protein ,lipolysis ,Monoglycerides ,chemical derivatization ,lipids (amino acids, peptides, and proteins) ,triacylglycerol - Abstract
Triacylglycerol (TAG) lipases hydrolyze ester bonds in TAG and release diacylglycerol (DAG), monoacylglycerol (MAG), and FA. We present a one-step chemical derivatization method for label-free quantification of a mixture of TAG, DAG, and MAG following lipase assay by ESI-MS. Because the ionization efficiencies of TAG, DAG, and MAG are not identical, lipase reaction products, DAG and MAG, are derivatized to TAG species by esterifying their hydroxyl groups using acyl chloride, whose acyl chain contains one less (or one more) -CH2 group than that of substrate TAG. This resulted in three TAG species that were separated by 14 Da from one another and exhibited similar ion responses representing their molar amounts in the mass spectra. A good linear correlation was observed between peak intensity ratios and molar ratios in calibration curve. This method enables simultaneous quantification of TAG, DAG, and MAG in lipase assay and, in turn, allows stoichiometric determination of the concentrations of FAs released from TAG and DAG separately. By applying this strategy to measure both TAG and DAG lipolytic activities of the yeast Tgl2 lipase, we demonstrated its usefulness in studying enzymatic catalysis, as lipase enzymes often show dissimilar activities toward these lipids.
- Published
- 2017
22. Probing nanoparticles and nanoparticle‐conjugated biomolecules using time‐of‐flight secondary ion mass spectrometry
- Author
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Young-Pil Kim, Seung Koo Shin, Hyun Kyong Shon, and Tae Geol Lee
- Subjects
chemistry.chemical_classification ,Immunoconjugates ,Biomolecule ,Metal Nanoparticles ,Spectrometry, Mass, Secondary Ion ,Nanoparticle ,Nanotechnology ,Conjugated system ,Condensed Matter Physics ,Antibodies ,Ferrosoferric Oxide ,General Biochemistry, Genetics and Molecular Biology ,Analytical Chemistry ,Characterization (materials science) ,Secondary ion mass spectrometry ,Time of flight ,chemistry ,CD4 Antigens ,Quantum Dots ,Humans ,Surface modification ,Nanomedicine ,Gold ,Peptides ,Spectroscopy - Abstract
Bio-conjugated nanoparticles have emerged as novel molecular probes in nano-biotechnology and nanomedicine and chemical analyses of their surfaces have become challenges. The time-of-flight (TOF) secondary ion mass spectrometry (SIMS) has been one of the most powerful surface characterization techniques for both nanoparticles and biomolecules. When combined with various nanoparticle-based signal enhancing strategies, TOF-SIMS can probe the functionalization of nanoparticles as well as their locations and interactions in biological systems. Especially, nanoparticle-based SIMS is an attractive approach for label-free drug screening because signal-enhancing nanoparticles can be designed to directly measure the enzyme activity. The chemical-specific imaging analysis using SIMS is also well suited to screen nanoparticles and nanoparticle–biomolecule conjugates in complex environments. This review presents some recent applications of nanoparticle-based TOF-SIMS to the chemical analysis of complex biological systems. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 34: 237–247, 2015.
- Published
- 2014
23. Energy- and Time-Dependent Branching to Competing Paths in Coupled Unimolecular Dissociations of Chlorotoluene Radical Cations
- Author
-
Jongcheol Seo, Seung Koo Shin, and Seung Joon Kim
- Subjects
Reaction rate constant ,Internal energy ,Chlorotoluene ,Chemistry ,Branching fraction ,Chemical physics ,Computational chemistry ,Kinetics ,General Chemistry ,Branching (polymer chemistry) ,Dissociation (chemistry) ,Ion - Abstract
The energy- and time-dependent branching to the competing dissociation paths are studied by theory for coupled unimolecular dissociations of the o-, m-, and p-chlorotoluene radical cations to C7H7 + (benzylium and tropylium). There are four different paths to C7H7 + , three to the benzylium ion and one to the tropylium ion, and all of them are coupled together. The branching to the multiple paths leads to the multiexponential decay of reactant with the branching ratio depending on both internal energy and time. To gain insights into the multipath branching, we study the detailed kinetics as a function of time and internal energy on the basis of ab inito/RRKM calculations. The number of reaction steps to C7H7 + is counted for each path. Of the three isomers, the meta mostly goes through the coupling, whereas the para proceeds with little or no coupling. In the beginning, some reactants with high internal energy decay fast to the benzylium ion without any coupling and others rearrange to the other isomers. Later on all three isomers dissociate to the products via long-lived intermediates. Thus, the reactant shows a multiexponential decay and the branching ratio varies with time as the average internal energy decreases with time. The reciprocal of the effective lifetime is taken as the rate constant. The resulting rate-energy curves are in line with experiments. The present results suggest that the coupling between the stable isomers is thermodynamically controlled, whereas the branching to the product is kinetically controlled.
- Published
- 2014
24. Halogen-π Interactions between Benzene and X
- Author
-
Il Seung, Youn, Dong Yeon, Kim, Woo Jong, Cho, Jenica Marie L, Madridejos, Han Myoung, Lee, Maciej, Kołaski, Joonho, Lee, Chunggi, Baig, Seung Koo, Shin, Michael, Filatov, and Kwang S, Kim
- Abstract
Various types of interactions between halogen (X) and π moiety (X-π interaction) including halogen bonding play important roles in forming the structures of biological, supramolecular, and nanomaterial systems containing halogens and aromatic rings. Furthermore, halogen molecules such as X
- Published
- 2016
25. Direct Synthesis of Multilayer Sheets of Reduced Graphene Oxide Over Cu-Foil
- Author
-
Koo Shin, Jonghwa Eom, Vivek Singh, M. W. Iqbal, Arun Kumar Singh, and Ju-Rang Yeon
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Graphene ,law ,Graphene foam ,Oxide ,Nanotechnology ,FOIL method ,law.invention ,Graphene oxide paper - Published
- 2013
26. A Simple Green Synthesis Route for the Reduction of Graphene Oxide and Its Application to Cu2+ Removal
- Author
-
Koo Shin, Ji Hyun Kim, Seung H. Han, Vivek Kumar Singh, and Ju-Rang Yeon
- Subjects
Reduction (complexity) ,chemistry.chemical_compound ,Materials science ,chemistry ,Chemical engineering ,Graphene ,law ,Simple (abstract algebra) ,Inorganic chemistry ,Oxide ,General Materials Science ,law.invention - Published
- 2013
27. Preparation andIn VitroandIn VivoPerformance of Magnesium Ion Substituted Biphasic Calcium Phosphate Spherical Microscaffolds as Human Adipose Tissue-Derived Mesenchymal Stem Cell Microcarriers
- Author
-
Hong-Chae Park, Jong Kook Lee, Kyu-Hong Hwang, Ju Dong Lee, Seog-Young Yoon, Tae-Wan Kim, Jin Sup Jung, Dong-Hyun Kim, and Keun-Koo Shin
- Subjects
Materials science ,Article Subject ,Biocompatibility ,Adipose tissue ,Microcarrier ,Balanced salt solution ,Bioceramic ,Tissue engineering ,In vivo ,lcsh:Technology (General) ,parasitic diseases ,Biophysics ,lcsh:T1-995 ,General Materials Science ,Magnesium ion - Abstract
Magnesium ion substituted biphasic calcium phosphate (Mg-BCP) bioceramic microscaffolds with spherical and porous morphology were successfully prepared usingin situcoprecipitation and rotary spray drying atomization process for application of tissue engineering combined with human adipose tissue-derived mesenchymal stem cells (hAT-MSCs). After 4 weeks of immersion in Hanks’ balanced salt solution (HBSS), Mg-BCP micro-scaffolds showed the enhanced biodegradation and bioactivity due to the substituted Mg2+ion present in the BCP structure. In this study, it was observed that hAT-MSCs have clearly attached on the surface of Mg-BCP micro-scaffolds. In addition, Mg-BCP micro-scaffolds exhibited the improved biocompatibility and osteoconductivity viain vitroandin vivobiological tests with hAT-MSCs. Therefore, these bioceramic micro-scaffolds had potential to be used as hAT-MSCs microcarriers for biomedical applications.
- Published
- 2013
28. Specific and nonspecific bindings of alkaline-earth metal ions to guanine-quadruplex thrombin-binding aptamer DNA
- Author
-
Seung Koo Shin, Hye-Joo Yoon, Eun Sun Hong, and Jongcheol Seo
- Subjects
inorganic chemicals ,Circular dichroism ,Guanine ,Electrospray ionization ,Metal ions in aqueous solution ,Analytical chemistry ,Condensed Matter Physics ,Binding constant ,Metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,visual_art.visual_art_medium ,Titration ,Physical and Theoretical Chemistry ,Instrumentation ,Spectroscopy ,DNA - Abstract
Specific and nonspecific bindings of alkaline-earth metal ions to the thrombin-binding aptamer (TBA) DNA d(GGTTGGTGTGGTTGG) were studied using electrospray ionization (ESI) mass spectrometry (MS). A single-stranded DNA d(AATTAATGTAATTAA) was used as a control for nonspecific binding. Both 1:1 and 2:1 metal–DNA complexes formed in 3:1 water/isopropanol were detected with ESI-MS and their binding constants were determined by the titration method. The 1:1 binding constant (K1) of Sr2+ or Ba2+ for TBA was three orders of magnitude greater than their K1 for the control DNA, whereas K1 of Mg2+ or Ca2+ for TBA was comparable to their K1 for the control DNA. To the contrary, the second binding constant (K2) was nearly the same independent of the metal ion and DNA. To see if addition of metal ion led to a structural change in DNA, the circular dichroism (CD) spectra of DNA in ESI solvent were obtained in the presence and absence of metal ion. TBA showed characteristic bands of the chair-type guanine-quadruplex (G4) structure. Significantly, addition of Sr2+ or Ba2+ enhanced the G4 bands of TBA, but neither Mg2+ nor Ca2+ induced a change, indicating that Sr2+ and Ba2+ interact strongly with G4 TBA and stabilize it. Control DNA showed no special motif and none of the four metal ions affected its CD spectra. Binding constants and CD results suggest that only the first binding of Sr2+ and Ba2+ to G4 TBA is specific and the first binding of Mg2+ and Ca2+ as well as the second binding of all four metal ions are nonspecific. The specific and nonspecific bindings of alkaline-earth metal ions to G4 TBA are further rationalized in terms of ionic radius, coordination number, and Gibbs free energy of dehydration of the metal ion.
- Published
- 2012
29. Noncovalent binding between fullerenes and protonated porphyrins in the gas phase
- Author
-
Sunghan Jung, Jongcheol Seo, and Seung Koo Shin
- Subjects
Porphyrins -- Chemical properties ,Hartree-Fock approximation -- Analysis ,Chemicals, plastics and rubber industries - Published
- 2010
30. Minicircle microporation-based non-viral gene delivery improved the targeting of mesenchymal stem cells to an injury site
- Author
-
Ji-Young Mun, Keun Koo Shin, Doo-Byoung Oh, Ohsuk Kwon, and Yong Taik Lim
- Subjects
0301 basic medicine ,Male ,Receptors, CXCR4 ,viruses ,Transgene ,Biophysics ,Bioengineering ,Gene delivery ,Biology ,Minicircle ,Transfection ,Cell Line ,Biomaterials ,03 medical and health sciences ,Cell Movement ,Bioluminescence imaging ,Animals ,Humans ,Cationic liposome ,Transgenes ,Mice, Inbred BALB C ,Wound Healing ,Electroporation ,Mesenchymal stem cell ,Optical Imaging ,Mesenchymal Stem Cells ,Molecular biology ,Cell biology ,030104 developmental biology ,Mechanics of Materials ,Luminescent Measurements ,Ceramics and Composites ,Plasmids - Abstract
Genetic engineering approaches to improve the therapeutic potential of mesenchymal stem cells (MSCs) have been made by viral and non-viral gene delivery methods. Viral methods have severe limitations in clinical application because of potential oncogenic, pathogenic, and immunogenic risks, while non-viral methods have suffered from low transfection efficiency and transient weak expression as MSCs are hard-to-transfect cells. In this study, minicircle, which is a minimal expression vector free of bacterial sequences, was employed for MSC transfection as a non-viral gene delivery method. The conventional cationic liposome method was not effective for MSC transfection as it resulted in very low transfection efficiency (less than 5%). Microporation, a new electroporation method, greatly improved the transfection efficiency of minicircles by up to 66% in MSCs without any significant loss of cell viability. Furthermore, minicircle microporation generated much stronger and prolonged transgene expression compared with plasmid microporation. When MSCs microporated with minicircle harboring firefly luciferase gene were subcutaneously injected to mice, the bioluminescence continued for more than a week, whereas the bioluminescence of the MSCs induced by plasmid microporation rapidly decreased and disappeared in mice within three days. By minicircle microporation as a non-viral gene delivery, MSCs engineered to overexpress CXCR4 showed greatly increased homing ability toward an injury site as confirmed through in vivo bioluminescence imaging in mice. In summary, the engineering of MSCs through minicircle microporation is expected to enhance the therapeutic potential of MSCs in clinical applications.
- Published
- 2016
31. miR-486-5p Induces Replicative Senescence of Human Adipose Tissue-Derived Mesenchymal Stem Cells and Its Expression Is Controlled by High Glucose
- Author
-
Sun-Young Lee, Yeon Jeong Kim, Hyun Hwa Cho, Keun Koo Shin, Yong Chan Bae, Jin Sup Jung, and Soo Hyun Hwang
- Subjects
Senescence ,Abdominal Fat ,Adipose tissue ,Endogeny ,Biology ,environment and public health ,Sirtuin 1 ,Downregulation and upregulation ,parasitic diseases ,Humans ,RNA, Messenger ,3' Untranslated Regions ,Cells, Cultured ,Cellular Senescence ,Oligonucleotide Array Sequence Analysis ,Regulation of gene expression ,Gene Expression Profiling ,Mesenchymal stem cell ,Mesenchymal Stem Cells ,Cell Biology ,Hematology ,beta-Galactosidase ,Cell biology ,MicroRNAs ,enzymes and coenzymes (carbohydrates) ,Glucose ,Gene Expression Regulation ,RNA Interference ,Developmental Biology ,Adult stem cell ,Deacetylase activity - Abstract
The reduction of adult stem cell self-renewal can be an important mechanism of aging. MicroRNAs have been reported to be involved in aging processes. Through a microarray approach, we have identified miR-486-5p, the expression of which is progressively expressed in human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) with aging. Overexpression of miR-486-5p induces a premature senescence-like phenotype and inhibits proliferation of hAT-MSCs and inhibits adipogenic and osteogenic differentiation, whereas inhibition of miR-486-5p has the opposite effects. miR-486-5p regulates the expression of silent information regulator 1 (SIRT1), a major regulator of longevity and metabolic disorders. Decrease of SIRT1 deacetylase activity in hAT-MSCs is correlated with their passage number. miR-486-5p inhibits SIRT1 expression through a miR-486-5p binding site within the 3'-untranslated region of SIRT1. Overexpression of miR-486-5p inhibits SIRT1 deacetylase activity in hAT-MSCs, and transfection of miR-486-5p inhibitor shows the opposite effect. Downregulation of SIRT1 in hAT-MSCs induces senescence and inhibits cell proliferation. Exposure to high glucose increases miR-486-5p expression and inhibits SIRT1 expression in hAT-MSCs. Our data pinpoint miR-486-5p as an endogenous inhibitor of SIRT1 that promotes hAT-MSCs senescence and is potentially applicable to therapeutic manipulation of hAT-MSCs dysfunction in metabolic disorders.
- Published
- 2012
32. Surface-Dependent, Ligand-Mediated Photochemical Etching of CdSe Nanoplatelets
- Author
-
Wonjung Kim, Seung Koo Shin, and Sung Jun Lim
- Subjects
Absorption spectroscopy ,Chemistry ,Exciton ,General Chemistry ,Photochemistry ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Nanocrystal ,Transmission electron microscopy ,Oleylamine ,Quantum dot ,Octadecene ,Wurtzite crystal structure - Abstract
Photochemical etching of CdSe nanoplatelets was studied to establish a relationship between the nanocrystal surface and the photochemical activity of an exciton. Nanoplatelets were synthesized in a mixture of octylamine and oleylamine for the wurtzite (W) lattice or in octadecene containing oleic acid for the zinc-blende (ZB) lattice. For photochemical etching, nanoplatelets were dispersed in chloroform containing oleylamine and tributylphosphine in the absence or presence of oleic acid and then irradiated with light at the band-edge absorption maxima. Etching phenomena were characterized using UV-vis absorption spectroscopy and transmission electron microscopy. The absorption spectra of both W and ZB CdSe nanoplatelets showed that the exciton was confined in one dimension along the thickness. However, the two nanoplatelets presented different etching kinetics and erosion patterns. The rate of etching for W CdSe nanoplatelets was much faster than that for ZB nanoplatelets. Small holes were uniformly perforated on the planar surface of W nanoplatelets, whereas the corners and edges of ZB nanoplatelets were massively eroded without a significant perforation on the planar surface. This suggests that the amine-passivated surface of trivalent cadmium atoms on CdSe nanoplatelets is photochemically active, but the carboxylate-passivated surface of divalent cadmium atoms is not. Hence, the ligand, which induces the growth of W or ZB CdSe nanoplatelets, mediates the surface-dependent photochemical etching. This result implies that an electron-hole pair can be extracted from the planar surface of amine-passivated W nanoplatelets but from the corners and edges of carboxylate-passivated ZB nanoplatelets.
- Published
- 2012
33. In situ formation of biphasic calcium phosphates and their biological performance in vivo
- Author
-
Young Min Park, Jin Sup Jung, Hong-Chae Park, Hyeong-Ho Jin, Seog-Young Yoon, Tae-Wan Kim, Keun-Koo Shin, and Dong-Hyun Kim
- Subjects
Materials science ,Biocompatibility ,Coprecipitation ,Process Chemistry and Technology ,chemistry.chemical_element ,Balanced salt solution ,Calcium ,Phosphate ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Biochemistry ,In vivo ,Materials Chemistry ,Ceramics and Composites ,MTT assay ,Bone regeneration ,Nuclear chemistry - Abstract
The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). After annealing at 900 °C for 24 h, hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) were obtained as a single phase at 1.67 and 1.5 Ca/P ratios, respectively. Between these two extremes, a whole range of BCP preparations could be synthesized by using this technique with an accurate control of starting reactants. The biological performance of BCP granulates with a specific content of 62% HAp and 38% β-TCP was investigated. After immersion in Hanks’ balanced salt solution (HBSS) for 1 week, a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that BCP granulates have no cytotoxic effects on MG-63 cells, and that they have good biocompatibility. An implantation experiment in mouse skulls revealed that BCP granulate provides a strong positive effect on bone formation in vivo in mice.
- Published
- 2012
34. The kinetics of competing multiple-barrier unimolecular dissociations of o-, m-, and p-chlorotoluene radical cations
- Author
-
Jongcheol Seo, Hyun-Il Seo, Seung-Joon Kim, and Seung Koo Shin
- Subjects
Radicals (Chemistry) -- Research ,Benzene -- Chemical properties ,Benzene -- Structure ,Chemicals, plastics and rubber industries - Abstract
Several ab initio/Rice-Ramsperger-Kassel-Marcus (RRKM) calculations are conducted to explain the kinetics of competing multiple-barrier unimolecular dissociations of o-, m-, and p-chlorotoluene radical cations to benzyl and tropylium ions. The benzyl channel in the system is shown to be kinetically favored.
- Published
- 2008
35. Anisotropic Etching of Semiconductor Nanocrystals
- Author
-
Sung Jun Lim, Sunghan Jung, Wonjung Kim, Seung Koo Shin, and Jongcheol Seo
- Subjects
Materials science ,General Chemical Engineering ,Chloromethane ,fungi ,Inorganic chemistry ,technology, industry, and agriculture ,Nanowire ,macromolecular substances ,General Chemistry ,Chloride ,Isotropic etching ,chemistry.chemical_compound ,stomatognathic system ,X-ray photoelectron spectroscopy ,Chemical engineering ,chemistry ,Etching (microfabrication) ,Materials Chemistry ,medicine ,Nanorod ,Reactive-ion etching ,medicine.drug - Abstract
The size and shape of CdSe nanorods, CdSe tetrapods, and CdS nanowires were tailored by chemical and photochemical etchings in chloromethane solvents. Nanocrystals were synthesized by colloidal growth, and their sizes and shapes were visualized by transmission electron microscopy before and after etching. Crystal structures were confirmed by X-ray diffraction, and optical properties were monitored during etching. Chemical etching with tributylphosphine preferentially shortens the length of nanocrystals, whereas photochemical etching with both primary alkylamine and tributylphosphine reduces the diameter more than the length. The surface of etched nanocrystals was characterized by X-ray photoelectron spectroscopy, and the etching products dissolved in solvent were analyzed by matrix-free laser desorption ionization mass spectrometry. Spectroscopic results suggest that the chloride ion is the active species: Chloride ions are generated either by chemical activation of chloromethane solvents with tributylpho...
- Published
- 2011
36. Electrical and Thermal Conductivities of Stycast 1266 Epoxy/Graphite Composites
- Author
-
Koo Shin, D. Hoang Tien, Joonkyu Park, Sang A Han, Yongho Seo, and Muneer Ahmad
- Subjects
Nanocomposite ,Graphene ,General Physics and Astronomy ,Percolation threshold ,Epoxy ,Conductivity ,law.invention ,Thermal conductivity ,Electrical resistivity and conductivity ,law ,Percolation ,visual_art ,visual_art.visual_art_medium ,Composite material - Abstract
Nanocomposites composed of graphene flakes and epoxy resin (Stycast 1266) were produced with different concentrations of graphene in the range of 0 to 15 wt.%. The direct-current conductivity of the composites complied with percolation behavior. The percolation threshold concentration pc from the conductivity measurement was estimated as 8 wt.%, and the critical exponent as t = 1.85 {+-} 0.23. The alternating-current conductivity of the composite increased monotonically as the frequency was increased in the range from 1 to 10 MHz. The thermal conductivity k also exhibited a similar percolation behavior, with highest value of k = 0.73 W/m{center_dot}K for the 12-wt.% composite, which corresponds to a 350% enhancement of the thermal conductivity.
- Published
- 2011
37. Mass spectrometric studies of competitive binding of C60and C70to mesosubstituted porphyrins
- Author
-
Seung Koo Shin and Sunghan Jung
- Subjects
Fullerene ,biology ,Chemistry ,Electrospray ionization ,Analytical chemistry ,Mole fraction ,biology.organism_classification ,Mass spectrometry ,Binding constant ,Porphyrin ,chemistry.chemical_compound ,Crystallography ,Mass spectrum ,Tetra - Abstract
Competitive binding of and to meso-substituted porphyrins was studied by mass spectrometry (MS). Electrospray ionization MS was employed to acquire the mass spectra of 1 : 1 porphyrin-fullerene complexes formed in a mixture of mesosubstituted porphyrin and fullerite to determine the ratio of complexes between and . Matrix-free laser desorption ionization MS was used to obtain the mass spectra of fullerite to measure the mole fraction of and . The binding constant ratio (/) was determined from the mass spectral data. The difference in standard Gibbs free energy change, , for the competitive binding of and was calculated from /. Of the five porphyrins, tetraphenyl, tetra(4-pyridyl), tetra(4-carboxyphenyl), tetra(3,5-di-tert-butylphenyl), and tetra(pentafluorophenyl) porphyrins, the first three non-bulky porphyrins yield negative values of , whereas the other two bulky porphyrins result in positive values of . This result indicates that binding to porphyrin is thermodynamically favored over binding in non-bulky porphyrins, but disfavored in bulky ones. It also suggests that the binding mode of is different between non-bulky and bulky porphyrins, which is in line with previous experimental findings of the "side-on" binding to non-bulky porphyrins and the -like "end-on" binding to bulky porphyrins.
- Published
- 2011
38. Mass spectrometric studies of competitive binding of C60 and C70 to mesosubstituted porphyrins
- Author
-
Sunghan Jung and Seung Koo Shin
- Subjects
lcsh:QD71-142 ,Fullerene ,Protonated porphyrin ,Porphyrin−fullerene complex ,Binding constant ,lcsh:Analytical chemistry - Abstract
Competitive binding of C60 and C70 to meso-substituted porphyrins was studied by mass spectrometry (MS). Electrosprayionization MS was employed to acquire the mass spectra of 1 : 1 porphyrin–fullerene complexes formed in a mixture of mesosubstitutedporphyrin and fullerite to determine the ratio of complexes between C60 and C70. Matrix-free laser desorption ionizationMS was used to obtain the mass spectra of fullerite to measure the mole fraction of C60 and C70. The binding constant ratio (K70/K60)was determined from the mass spectral data. The difference in standard Gibbs free energy change, Δ(ΔGo)70–60, for the competitivebinding of C60 and C70 was calculated from K70/K60. Of the five porphyrins, tetraphenyl, tetra(4-pyridyl), tetra(4-carboxyphenyl),tetra(3,5-di-tert-butylphenyl), and tetra(pentafluorophenyl) porphyrins, the first three non-bulky porphyrins yield negative valuesof Δ(ΔGo)70−60, whereas the other two bulky porphyrins result in positive values of Δ(ΔGo)70−60. This result indicates that C70binding to porphyrin is thermodynamically favored over C60 binding in non-bulky porphyrins, but disfavored in bulky ones. Italso suggests that the binding mode of C70 is different between non-bulky and bulky porphyrins, which is in line with previousexperimental findings of the “side-on” binding to non-bulky porphyrins and the C60-like “end-on” binding to bulky porphyrins.
- Published
- 2011
39. A Study of the Trait of Shamanic Culture in Taean
- Author
-
Sang-Koo Shin
- Subjects
Evolutionary biology ,Trait ,General Medicine ,Biology - Published
- 2011
40. A Room Temperature Conductometric Hydrogen Sensor with Polyaniline/WO3 Nanocomposite
- Author
-
Wojtek Wlodarski, Laith Al-Mashat, Seung-Hyun Han, Dae-Sik Ahn, and Koo Shin
- Subjects
Nanocomposite ,Materials science ,Hydrogen ,Polyaniline nanofibers ,Scanning electron microscope ,Analytical chemistry ,chemistry.chemical_element ,Hydrogen sensor ,Atomic and Molecular Physics, and Optics ,chemistry.chemical_compound ,chemistry ,Operating temperature ,Polyaniline ,Electrical and Electronic Engineering ,Fourier transform infrared spectroscopy - Abstract
Polyaniline/W03 nanocomposite with high volume of W03 compared to polyaniline has been synthesized through a template-free synthetic route. Characterization of the developed nanomaterial was conducted through Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). A conductometric transducer was fabricated and used to measure the resistance of polyaniline/W03 nanofiber films during interaction with different concentrations of hydrogen gas at room temperature. The concentration of aniline monomer to W03 was 1 to 8 on the solution. It was observed that the sensor has a stable baseline of 33.2 KO under synthetic air. A decrease in the sensitive film resistance of i .4 K!l was noticed during the Interaction with 1% H2 with 90% response time of 60 seconds. Due to the high operating temperature of ali metal oxides based gas sensors, this sensor offers low power consumption because of its room temperature operation.
- Published
- 2011
41. Layered Surface Acoustic Wave Hydrogen Sensor with Nanoporous Polyaniline as the Active Layer
- Author
-
Wojtek Wlodarski, W Hong, K Kalantar Zadeh, C Yoon, Laith Al-Mashat, Koo Shin, S Han, and D Ahn
- Subjects
Generativity ,media_common.quotation_subject ,Engineering ethics ,Prison ,Sociology ,Electrical and Electronic Engineering ,Social psychology ,Atomic and Molecular Physics, and Optics ,Young male ,Generative grammar ,media_common - Abstract
In recent years, a small but critically informed literature has emerged which points to the link between opportunities to engage in generative acts and desistance from crime. This paper outlines the nature and limits of generative moments (conceived as the philosophy or practice of caring in non-violent and durable ways for self, other and future) with regard to the incarceration of a group of young males interviewed since 2003. Specifically, it poses the question of who or what it has been possible for these young men to care about within and beyond custody and highlights some of the factors which undermine generative concerns and actions. In concluding, the paper offers several ideas for enhancing generative opportunities within custodial environments.
- Published
- 2011
42. Polyaniline/MWCNT Nanocomposite Based Hydrogen Sensor Operating at Room Temperature
- Author
-
D Ahn, Koo Shin, Wojtek Wlodarski, J Song, Laith Al-Mashat, B Yoo, S Han, and K Kalantar Zadeh
- Subjects
Materials science ,Nanocomposite ,Hydrogen ,Scanning electron microscope ,chemistry.chemical_element ,Carbon nanotube ,Hydrogen sensor ,Atomic and Molecular Physics, and Optics ,Nanomaterials ,law.invention ,chemistry.chemical_compound ,chemistry ,Transmission electron microscopy ,law ,Polyaniline ,Electrical and Electronic Engineering ,Composite material - Abstract
A nanocornposite of polyaniline (PANI) and multiwall carbon nanotubes (MWCNT) has been synthesized and investigated as a sensing material for hydrogen gas at room temperature. The PANI/MWCNT nanocomposite was prepared by in situ chemical polymerization. The nanomaterial characterization was conducted through Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). From these data it was concluded that the PANI formed conformal layer with thickness of approximately 7 nm aligned to the outer layer of the MWCNT. A hydrogen sensor was developed by airbrushing the solution over the surface of heated conductometric transducer. The sensor was tested towards different concentrations of hydrogen gas at room temperature. At 1% of H(2) an increase in the sensing film resistance of 112 Omega was observed. The sensor maintained its stable baseline and repeatability during the testing period which makes it useful for commercialization purposes.
- Published
- 2011
43. Ditopic Binding of Alkali Halide Ions to Trimethylboroxine
- Author
-
Seung Koo Shin and Kyung Hwan Jeong
- Subjects
lcsh:QD71-142 ,Chemistry ,Ditopic Ion-Pair Binding ,Inorganic chemistry ,lcsh:Analytical chemistry ,chemistry.chemical_element ,Halide ,Alkali metal ,Ring (chemistry) ,Fourier transform ion cyclotron resonance ,Lithium Fluoride ,Ion ,Crystallography ,Trimethylboroxine ,Density functional theory ,Boron ,Spectroscopy ,Ion-Molecule Association - Abstract
Trimethylboroxine (TMB) is a six-membered ring compound containing Lewis acidic boron and Lewis basic oxygen atoms that can bind halide anion and alkali metal cation, respectively. We employed Fourier transform ion cyclotron resonance spectroscopy to study the gas-phase binding of LiBrLi + and F � (KF)2 to TMB. TMB forms association complexes with both LiBrLi + and F - (KF)2 at room temperature, providing direct evidence for the ditopic binding. Interestingly, the TMB·F � (KF)2 anion complex is formed 33 times faster than the TMB·Li + BrLi cation complex. To gain insight into the ditopic binding of an ion pair, we examined the structures and energetics of TMB·Li + , TMB·F - , TMB·LiF (the contact ion pair), and Li + ·TMB·F - (the sep- arated ion pair) using Hartree-Fock and density functional theory. Theory suggests that F - binds more strongly to TMB than Li + and the contact ion-pair binding (TMB·LiF) is more stable than the separated ion-pair binding (Li + ·TMB·F - ).
- Published
- 2010
44. Graphene/Polyaniline Nanocomposite for Hydrogen Sensing
- Author
-
Robert W. Kojima, Kourosh Kalantar-zadeh, Xinglong Gou, Samuel J. Ippolito, Laith Al-Mashat, Wojtek Wlodarski, Koo Shin, Richard B. Kaner, Seung H. Han, Johan du Plessis, and Dan Li
- Subjects
Nanocomposite ,Materials science ,Polyaniline nanofibers ,Scanning electron microscope ,Graphene ,Nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,symbols.namesake ,General Energy ,chemistry ,law ,Nanofiber ,Polyaniline ,symbols ,Ammonium persulfate ,Physical and Theoretical Chemistry ,Raman spectroscopy - Abstract
Here we report on the synthesis of a graphene/polyaniline (PANI) nanocomposite and its application in the development of a hydrogen (H2) gas sensor. Using a chemical synthetic route, graphene was prepared and ultrasonicated with a mixture of aniline monomer and ammonium persulfate to form PANI on its surface. The developed material was characterized by scanning electron microscopy (SEM), transmission electron microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy. The SEM study revealed that the PANI in the composite has a nanofibrillar morphology. We investigated the H2 gas sensing performance of this material and compare it with that of the sensors based on only graphene sheets and PANI nanofibers. We found that the graphene/PANI nanocomposite-based device sensitivity is 16.57% toward 1% of H2 gas, which is much larger than the sensitivities of sensors based on only graphene sheets and PANI nanofibers.
- Published
- 2010
45. Focused Electrospray Deposition for Matrix-assisted Laser Desorption/Ionization Mass Spectrometry
- Author
-
Jongcheol Seo, Kyung Hwan Jeong, Hye-Joo Yoon, and Seung Koo Shin
- Subjects
Electrospray ,Matrix-assisted laser desorption/ionization ,Desorption electrospray ionization ,Matrix-assisted laser desorption electrospray ionization ,Chemistry ,Analytical chemistry ,Mass spectrum ,General Chemistry ,Mass spectrometry ,Angiotensin II ,Ambient ionization - Abstract
Focused electrospray (FES) deposition method is presented for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. FES ion optics consists of two cylindrical focusing electrodes capped with a truncated conical electrode through which an electrospray emitter passes along the cylindrical axis. A spray of charged droplets is focused onto a sample well on a MALDI target plate under atmospheric pressure. The shape and size distributions of matrix crystals are visualized by scanning electron microscope and the mass spectra are obtained by time-of-flight mass spectrometry. Angiotensin II, bradykinin, and substance P are used as test samples, while α-cyano-4-hydroxycinnamic acid and dihydroxybenzoic acid are employed as matrices. FES of a sample/matrix mixture produces fine crystal grains on a 1‒3 mm spot and reproducibly yields the mass spectra with little shot-to-shot and spot-to-spot variations. Although FES greatly stabilizes the signals, the space charge due to matrix ions limits the detection sensitivity of peptides. To avoid the space charge problem, we adopted a dual FES/FES mode, which separately deposits matrix and sample by FES in sequence. The dual FES/FES mode reaches the detection sensitivity of 0.88 amol, enabling ultrasensitive detection of peptides by homogeneously depositing matrix and sample under atmospheric pressure.
- Published
- 2010
46. Bioconjugation of Hydroxylated Semiconductor Nanocrystals and Background-Free Biomolecule Detection
- Author
-
Hye-Joo Yoon, Wonjung Kim, Yongwook Kim, and Seung Koo Shin
- Subjects
Photoluminescence ,Propanols ,Carbonates ,Biomedical Engineering ,Biotin ,Succinimides ,Pharmaceutical Science ,Bioengineering ,Nanotechnology ,Sulfides ,Conjugated system ,Hydroxylation ,Cadmium Compounds ,Molecule ,Sulfhydryl Compounds ,Selenium Compounds ,Fluorescent Dyes ,Pharmacology ,chemistry.chemical_classification ,Bioconjugation ,Molecular Structure ,Biomolecule ,Organic Chemistry ,DNA ,Combinatorial chemistry ,Fluorescence ,Nanostructures ,Zinc ,Semiconductors ,Solubility ,Nanocrystal ,chemistry ,Zinc Compounds ,Covalent bond ,Peptides ,Biotechnology - Abstract
Semiconductor nanocrystals emerge as fluorescent bioprobes for long-term imaging and multiplexed assays; however, there is a challenge of making nanocrystals biocompatible without nonspecific bindings to background molecules. Here, we report the bioconjugation of small-sized, hydroxylated nanocrystals, enabling highly sensitive detection of various biomolecules with little or no nonspecific binding. Zinc-blende CdSe/ZnS nanocrystals were passivated with 3-mercapto-1-propanol (MPO) and activated to amine-reactive succinimidyl carbonate derivatives and then covalently linked to amine-functionalized biomolecules, such as biotin, DNA, and hemagglutinin peptide, by forming a carbamate linkage. Tris(3-hydroxypropyl)phosphine was added to stabilize the zinc-thiolate linkage on nanocrystals. For comparison, CdSe/ZnS nanocrystals were passivated with 3-mercaptopropionic acid (MPA) and conjugated with aminated biomolecules. Photoluminescence properties of organic, water-soluble, and bioconjugated nanocrystals were characterized. Significantly, the bioconjugates of hydroxylated (CdSe/ZnS-MPO) nanocrystals exhibited brighter photoluminescence with longer lifetimes than those of carboxylated (CdSe/ZnS-MPA) nanocrystals. Specific and nonspecific interactions between nanocrystals and biomolecules were examined by incubating nanocrystal-bioconjugates with avidin-agarose beads, anti-hemagglutinin affinity matrix, DNA glass slide, or avidin glass slide. CdSe/ZnS-MPO nanocrystals showed little or no nonspecific binding to both agarose beads and glass slides, whereas CdSe/ZnS-MPA nanocrystals exhibited significant nonspecific binding due to the carboxyl-amine interactions. Notably, CdSe/ZnS-MPO bioconjugates yield about 20 times brighter images than CdSe/ZnS-MPA bioconjugates in both DNA hybridization and biotin-streptavidin binding. Hydroxylated nanocrystals stabilized by hydroxyphosphine are small, bright, and photostable in physiological conditions, and their bioconjugates afford background-free detection of specific biomolecular interactions, positioning them for an ideal fluorescent probe to biological settings.
- Published
- 2010
47. Preparation and Physical Properties of Red-photoluminescent Graphene/Europium(III)/Picolinate
- Author
-
Hye Jin Kim, Yunghee Oh, Yun-Sik Yu, Jang Yong Kim, Koo Shin, and Jin Bong Lee
- Subjects
Materials science ,Photoluminescence ,Graphene ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,law.invention ,Ion ,Metal ,chemistry.chemical_compound ,chemistry ,law ,visual_art ,Excited state ,visual_art.visual_art_medium ,Carboxylate ,Luminescence ,Europium - Abstract
Novel photoluminescent graphene, graphene/europium/picolinate, was made from the reaction of the graphene carboxylate, europium(III) and α-pyridoin anion in methanol solution. There was evidence on IR spectroscopic data that europium metal was coordinated by graphene carboxylate. The graphene/europium/picolinate materials emitted the red luminescence with main peaks at 609 and 695 nm, when solid sample was excited by an UV light at the wavelength of 254 nm. The surface morphology and physical properties of the graphene/europium/picolinate product have been investigated by IR, PL, SEM, TEM and TGA measurements.
- Published
- 2010
48. A Study on the Artistic Handcrafts of Cutting Paper of Shamans in Tae-an
- Author
-
Sang-Koo Shin
- Subjects
General Medicine - Published
- 2010
49. Binary Amine−Phosphine Passivation of Surface Traps on CdSe Nanocrystals
- Author
-
Seung Koo Shin, Sunghan Jung, Wonjung Kim, and Sung Jun Lim
- Subjects
Materials science ,Photoluminescence ,Passivation ,Nanotechnology ,Propylamine ,Photochemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Nanocrystal ,Quantum efficiency ,Tributylphosphine ,Physical and Theoretical Chemistry ,Absorption (chemistry) ,Luminescence - Abstract
Surface traps, such as electron and hole traps, quench the photoluminescence (PL) of semiconductor nanocrystals. We find a binary ligand system that effectively passivates those surface traps on bare CdSe nanocrystals, thereby making the nanocrystals highly luminescent. Zinc-blende CdSe nanocrystals are prepared by colloidal synthesis, and their optical properties are monitored by varying the amounts of propylamine (PA) and tributylphosphine (TBP) in chloroform at room temperature. The starting CdSe nanocrystals that are mostly covered with fatty acid carboxylates show very low quantum efficiency with a multiexponential PL decay. Addition of excess PA induces blueshifts in both absorption and emission spectra with a slight increase in quantum efficiency and PL lifetime, whereas that of TBP reduces the PL intensity. Surprisingly, addition of both PA and TBP makes nanocrystals emit light with an ∼50% quantum efficiency and a nearly single-exponential PL decay, regardless of the sequence of ligand addition. ...
- Published
- 2010
50. The TGL2 Gene of Saccharomyces cerevisiae Encodes an Active Acylglycerol Lipase Located in the Mitochondria
- Author
-
Hyun Joo Rho, Hye Jin Ham, Seung Koo Shin, and Hye-Joo Yoon
- Subjects
Mutant ,Saccharomyces cerevisiae ,Triacylglycerol lipase ,Mitosis ,Lipids and Lipoproteins: Metabolism, Regulation, and Signaling ,Biochemistry ,Substrate Specificity ,Fungal Proteins ,chemistry.chemical_compound ,Serine ,Lipase ,Molecular Biology ,Fatty acid synthesis ,Alanine ,biology ,Hydrolysis ,Fatty Acids ,Cell Biology ,Acylglycerol lipase ,biology.organism_classification ,Lipids ,Cerulenin ,Yeast ,Mitochondria ,Phosphotransferases (Alcohol Group Acceptor) ,Phenotype ,chemistry ,Mutation ,biology.protein ,Oleic Acid - Abstract
The Saccharomyces cerevisiae Tgl2 protein shows sequence homology to Pseudomonas triacylglycerol (TAG) lipases, but its role in the yeast lipid metabolism is not known. Using hemagglutinin-tagged Tgl2p purified from yeast, we report that this protein carries a significant lipolytic activity toward long-chain TAG. Importantly, mutant hemagglutinin-Tgl2p(S144A), which contains alanine 144 in place of serine 144 in the lipase consensus sequence (G/A)XSXG exhibits no such activity. Although cellular TAG hydrolysis is reduced in the tgl2 deletion mutant, overproduction of Tgl2p in this mutant leads to an increase in TAG degradation in the presence of fatty acid synthesis inhibitor cerulenin, but that of Tgl2p(S144A) does not. This result demonstrates the lipolytic function of Tgl2p in yeast. Although other yeast TAG lipases are localized to lipid particles, Tgl2p is enriched in the mitochondria. The mitochondrial fraction purified from the TGL2-overexpressing yeast shows a strong lipolytic activity, which was absent in the tgl2 deletion mutant. Therefore, we conclude that Tgl2p is a functional lipase of the yeast mitochondria. By analyzing phenotypic effects of TGL2-deficient yeast, we also find that lipolysis-competent Tgl2p is required for the viability of cells treated with antimitotic drug. The addition of oleic acid, the product of Tgl2p-catalyzed lipolysis, fully complements the antimitotic drug sensitivity of the tgl2 null mutation. Thus, we propose that the mitochondrial Tgl2p-dependent lipolysis is crucial for the survival of cells under antimitotic drug treatment.
- Published
- 2010
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