36 results on '"Keiichiro Shiraga"'
Search Results
2. Hydrogen-Bond Configurations of Hydration Water around Glycerol Investigated by HOH Bending and OH Stretching Analysis
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Miho Morita, Fumiki Matsumura, Toshiyuki Shikata, Yuichi Ogawa, Naoshi Kondo, and Keiichiro Shiraga
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Glycerol ,Materials Chemistry ,Water ,Hydrogen Bonding ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Hydrogen - Abstract
Toward a comprehensive understanding of the mechanism of glycerol as a moisturizer, studies on the hydrogen-bond (HB) structure of hydration water, which is known to be disordered by glycerol, are insufficient. To this aim, we evaluated the HB configurations based on the HOH bending and OH stretching spectra of the hydration water from those of glycerol/water mixtures by subtracting the contributions of bulk water and glycerol using dielectric relaxation spectroscopy. Analysis of the HOH bending band showed that hydration water-donating HBs lose the intermolecular bending coupling with increasing glycerol by replacing the water-water HBs with water-glycerol HBs. The OH stretching band provided more detailed insight into the HB configuration, indicating that the double-donor double-acceptor and double-donor single-acceptor configurations in bulk water change to a predominantly double-donor single-acceptor configuration in hydration water around glycerol. The formation of more donor HBs than acceptor HBs may be due to the steric constrains by glycerol and/or differences in the partial charge on the oxygen atom between water and glycerol. more...
- Published
- 2022
Catalog
3. Dielectrophoresis-assisted 65-GHz LC-oscillator array CMOS chips for label-free and sensitive detection of microorganism cells
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Siyao Chen, Yoshihisa Yamashige, Takeshi Mitsunaka, Naoshi Kondo, Keiichiro Shiraga, and Yuichi Ogawa
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Metals and Alloys ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Instrumentation ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2023
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4. Potentiality of Terahertz Wave in Egg and Poultry Research
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Alin Khaliduzzaman, Keiichiro Shiraga, and Naoshi Kondo
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- 2022
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5. Quantification of starch content in germinating mung bean seedlings by terahertz spectroscopy
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Tetsuhito Suzuki, Shusaku Nakajima, Naoshi Kondo, Keiichiro Shiraga, and Yuichi Ogawa
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Terahertz Spectroscopy ,Absorption (pharmacology) ,Mung bean ,biology ,Starch ,Hydrolysis ,Vigna ,food and beverages ,Germination ,General Medicine ,Analytical Chemistry ,Terahertz spectroscopy and technology ,chemistry.chemical_compound ,Glucose ,chemistry ,Seedlings ,Reagent ,biology.protein ,Food science ,Amylase ,alpha-Amylases ,Food Science - Abstract
To investigate the potential of terahertz spectroscopy to monitor and quantify starch in plants, terahertz spectra (3.0–13.5 THz) of mung bean plants 1–7 days after germination were examined and compared to those of starch and its constituent saccharides (standard reagents). Day 1 seedlings showed similar spectral features with standard starch, and absorption peaks gradually disappeared in the subsequent 6 day growth period. To interpret this result and identify useful peaks for starch quantification, standard starch and day 1 seedlings were hydrolyzed by α-amylase in vitro. Since both standard starch and seedlings showed that absorption peak at 9.0 THz disappeared after amylase hydrolysis, this peak is sensitive to changes in starch. Additionally, intensity of this peak was correlated with starch content as quantified by chemical analysis (r = 0.98). Our results indicate terahertz spectra of seedlings can provide an identifiable peak that is attributed to starch and not affected by the constituent saccharides. more...
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- 2019
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6. 3D in vivo imaging of the keratin filament network in the mouse stratum granulosum reveals profilaggrin-dependent regulation of keratin bundling
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Masayuki Amagai, Takeshi Matsui, Keiko Usui, Takashi Saitou, Kiminori Toyooka, Hiroomi Tamura, Yuki Furuichi, Keiichiro Shiraga, Akiharu Kubo, Hiroshi Kawasaki, and Nanako Kadono
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Keratinocytes ,Male ,Intravital Microscopy ,Green Fluorescent Proteins ,Primary Cell Culture ,Stratum granulosum ,Intermediate Filaments ,Dermatology ,Filaggrin Proteins ,Biochemistry ,Mice ,Imaging, Three-Dimensional ,Intermediate Filament Proteins ,Genes, Reporter ,Keratin ,medicine ,Animals ,Humans ,Molecular Biology ,Mice, Knockout ,chemistry.chemical_classification ,Mice, Hairless ,Microscopy, Confocal ,Keratin Filament ,Chemistry ,S100 Proteins ,Cell biology ,Luminescent Proteins ,Microscopy, Electron ,medicine.anatomical_structure ,Keratins ,Epidermis ,Preclinical imaging ,HeLa Cells - Published
- 2019
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7. Japanese dace (Tribolodon hakonensis) fish freshness estimation using front-face fluorescence spectroscopy coupled with chemometric analysis
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Ken Abamba Omwange, Yoshito Saito, Dimas Firmanda Al Riza, Huang Zichen, Makoto Kuramoto, Keiichiro Shiraga, Yuichi Ogawa, Naoshi Kondo, and Tetsuhito Suzuki
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Spectrometry, Fluorescence ,Japan ,Cyprinidae ,Animals ,Chemometrics ,Least-Squares Analysis ,Instrumentation ,Spectroscopy ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry - Abstract
Although fish and its related products are good sources of protein and unsaturated fatty acids, like omega-3 in the human diet, their shelf-life is limited by biochemical and microbial changes. In this study, a front-face fluorescence spectroscopy technique was used to acquire Excitation-emission matrices (EEM) to monitor Japanese dace (Tribolodon hakonensis) fish freshness degradation during storage. EEM of Japanese dace fish parts (intact eyeball and surface-containing scales), excitation from 220 to 585 nm and emissions from 250 to 600 nm, were measured at different times during storage. To simplify the acquired complex spectra datasets from each fish part, the variables were reduced to those that were only significant/important (those with higher positive or negative correlation) for K value prediction, and as an index of freshness. Partial least square regression (PLSR) results demonstrated that combining the fluorescence EEM of the eyeball and surface-containing scales the best monitoring of fish freshness; excitation at 280 and 350 nm for both the eyeball and surface-containing scales, with 2.84 and 0.96 as RMSE and R more...
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- 2022
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8. Estimation of refractive index of eggshell in intact egg using terahertz time-domain spectroscopy
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Alin Khaliduzzaman, Naoshi Kondo, Keiichiro Shiraga, and Yuichi Ogawa
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Optics ,Materials science ,business.industry ,Terahertz radiation ,Frequency domain ,Eggshell ,business ,Terahertz time-domain spectroscopy ,Absorption (electromagnetic radiation) ,Spectroscopy ,Refractive index ,Terahertz spectroscopy and technology - Abstract
Terahertz is a relatively new, and yet to be explored that how it interacts with many biological objects like avian eggshell. Eggshell protects internal contents of egg from contaminants and ultraviolet radiation. It also acts as a major mineral source for embryonic development. The refractive index indicating eggshell compactness could be a potential quality criterion of shell for both table and hatching egg. But a little is known about refractive index of eggshell. However, the available information is only based on destructive method which is not suitable to use in many cases due to loss of eggshell integrity. Therefore, we aim to develop a non-destructive protocol of eggshell refractive index measurement using terahertz timedomain spectroscopy (THz-TDS) which can directly derive refractive index in the terahertz region from the temporal pulses. In order to get rid of intense terahertz absorption by egg albumen, we used THz-TDS to measure reflectance of intact eggshell in the 0.2-1.2 THz. THz wave`s frequency domain interferences signal contains the information of both thickness and refractive index of the eggshell. The results revealed that this proposed method can be used in estimation of refractive index of intact eggshell with co-efficient of determination (R2) of 0.49. This non-destructive protocol could not only be used in industrial grading of eggs but also in many applied research fields such as applied optics, ornithology, evolutionary biology in the future. more...
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- 2021
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9. Dynamical Collectivity and Nuclear Quantum Effects on the Intermolecular Stretching Mode of Liquid Water
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Koichiro Tanaka, Akitoshi Koreeda, Keiichiro Shiraga, Takashi Arikawa, Yasuhiro Fujii, and Yuichi Ogawa
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Materials science ,010304 chemical physics ,Liquid water ,Terahertz radiation ,Intermolecular force ,Mode (statistics) ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,symbols.namesake ,Chemical physics ,0103 physical sciences ,Broadband ,Materials Chemistry ,symbols ,Physical and Theoretical Chemistry ,Raman spectroscopy - Abstract
This study investigated the broadband terahertz and low-frequency Raman spectroscopy of liquid water (H2O, D2O, and H218O) over 2 decades of frequency to address long-standing challenges regarding ... more...
- Published
- 2021
10. Near-field sensor array with 65-GHz CMOS oscillators for rapid detection of viable Escherichia coli
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Keiichiro Shiraga, Yoshihisa Yamashige, Yuichi Ogawa, Shojiro Kikuchi, and Takeshi Mitsunaka
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Permittivity ,Materials science ,Biomedical Engineering ,Biophysics ,Near and far field ,02 engineering and technology ,Dielectric ,Biosensing Techniques ,medicine.disease_cause ,Electric Capacitance ,01 natural sciences ,Resonator ,Sensor array ,Electrochemistry ,medicine ,Escherichia coli ,Electronic oscillator ,business.industry ,010401 analytical chemistry ,Oxides ,General Medicine ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,CMOS ,Semiconductors ,Optoelectronics ,0210 nano-technology ,business ,Biotechnology - Abstract
In this study, the growth of Escherichia coli was monitored using a complementary metal-oxide-semiconductor (CMOS) near-field sensor array. Each of the 1488 integrated elements, arranged in a 3 mm square, has a resonator that oscillates at 65 GHz. The effective capacitance of the resonator is altered by changes in the dielectric properties of the sensor surface, which shifts the resonance frequency. Growth curves of E. coli at different initial concentrations (OD600 = 0.01, 0.03, and 0.05) were monitored. A suspension with initial turbidity of OD600 = 0.05 was cultured in a medium, and the sensor successfully distinguished between viable E. coli and heat-treated dead E. coli in 20 min. Moreover, the apparent suppression of growth was observed in the presence of 500 μg/mL streptomycin. As the sensor is composed of arrayed elements, and the area of sensitivity distribution of the element is larger than the size of one bacteria, the variation in the output value of each element may reflect the number and movement of bacteria. This study revealed that the presence of viable E. coli could be rapidly confirmed by using the change in permittivity caused by the displacement of media by E. coli near the sensor surface. more...
- Published
- 2020
11. Highly precise characterization of the hydration state upon thermal denaturation of human serum albumin using a 65 GHz dielectric sensor
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Yuichi Ogawa, Takeshi Matsui, Shojiro Kikuchi, Mako Urabe, and Keiichiro Shiraga
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Protein Denaturation ,Materials science ,Hot Temperature ,Oscillation ,Hydrogen bond ,General Physics and Astronomy ,Water ,Hydrogen Bonding ,Serum Albumin, Human ,Dielectric ,Electrochemical Techniques ,Human serum albumin ,Solvation shell ,Protein structure ,Chemical physics ,Phase (matter) ,Native state ,medicine ,Humans ,Physical and Theoretical Chemistry ,Algorithms ,medicine.drug - Abstract
The biological functions of proteins depend on harmonization with hydration water surrounding them. Indeed, the dynamical transition of proteins, such as thermal denaturation, is dependent on the changes in the mobility of hydration water. However, the role of hydration water during dynamical transition is yet to be fully understood due to technical limitations in precisely characterizing the amount of hydration water. A state-of-the-art CMOS dielectric sensor consisting of 65 GHz LC resonators addressed this issue by utilizing the feature that oscillation frequency sensitively shifts in response to the complex dielectric constant at 65 GHz with extremely high precision. This study aimed to establish an analytical algorithm to derive the hydration number from the measured frequency shift and to demonstrate the transition of hydration number upon the thermal denaturation of human serum albumin. The determined hydration number in the native state drew a “global” hydration picture beyond the first solvation shell, with substantially reduced uncertainty of the hydration number (about ±1%). This allowed the detection of a rapid increase in the hydration number at about 55 °C during the heating process, which was in excellent phase with the irreversible rupture of the α-helical structure into solvent-exposed extended chains, whereas the hydration number did not trace the forward path in the subsequent cooling process. Our result indicates that the weakening of water hydrogen bonds trigger the unfolding of the protein structure first, followed by the changes in the number of hydration water as a consequence of thermal denaturation. more...
- Published
- 2020
12. Coexistence of Kosmotropic and Chaotropic Impacts of Urea on Water As Revealed by Terahertz Spectroscopy
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Katsuhiro Ajito, Masahito Nakamura, Koichiro Tanaka, Takuro Tajima, Takashi Arikawa, Keiichiro Shiraga, Yuichi Ogawa, and Naotaka Yoshikawa
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Kosmotropic ,Aqueous solution ,010304 chemical physics ,Hydrogen bond ,Relaxation (NMR) ,Analytical chemistry ,010402 general chemistry ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Surfaces, Coatings and Films ,Terahertz spectroscopy and technology ,chemistry.chemical_compound ,Chaotropic agent ,chemistry ,0103 physical sciences ,Materials Chemistry ,Urea ,Physical and Theoretical Chemistry - Abstract
Whether urea can serve as a kosmotrope or chaotrope has long been a topic of debate. In this study, broad-band THz spectroscopy (0.2-12 THz) of aqueous solutions of urea was used to characterize the hydration state and the hydrogen bond structure of water around urea. Three low-frequency vibration modes of urea were found around 2, 4, and above 12 THz. After eliminating the contribution of these modes, the "urea-vibration-free" complex dielectric constant was decomposed into the relaxation modes of bulk water and the oscillation modes of water. When hydration water is defined to be reorientationally retarded relative to bulk, our analysis revealed that the hydration number is 1.9 independent of urea concentrations up to 5 M, and this number is in close agreement with that of water constrained by strong acceptor hydrogen bonds of urea oxygen. Regarding the hydrogen bond structure, it was found that the tetrahedral-like water structure is mostly preserved (though the hydrogen bond lifetime is significantly shortened) but the population of non-hydrogen-bonded water molecules fragmented from the network is markedly increased, presumably due to urea's NH more...
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- 2018
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13. Reconsideration of the relaxational and vibrational line shapes of liquid water based on ultrabroadband dielectric spectroscopy
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Koichiro Tanaka, Keiichiro Shiraga, Yuichi Ogawa, Takashi Arikawa, and Shinji Saito
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Physics ,Intermolecular force ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Dielectric spectroscopy ,symbols.namesake ,Modulation ,Libration ,symbols ,Relaxation (physics) ,Debye function ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy ,Frequency modulation - Abstract
The Debye relaxation function is widely used to describe the large dielectric dispersion of ambient water around 20 GHz. However, from a theoretical point of view, this function is supposed to give incorrect predictions at high frequencies owing to the inappropriate assumption that inertial effects and intermolecular interactions do not affect the relaxation dynamics. Our ultrabroadband spectroscopy investigation of liquid water ranging from 500 MHz to 400 THz did demonstrate that the Debye function is inaccurate far above the microwave region. As an alternative, we tried a stochastic frequency modulation (SFM) model assuming instantaneous modification of the line shapes by the correlation with the surrounding system. The SFM relaxation model reproduced the experimental dielectric spectra up to 400 THz, showing that the hydrogen-bond dynamics are associated with the inertial effect that causes the non-exponential relaxation behaviour in a very short time (typically 25 fs). Within the framework of this relaxation model, the hindered translation modes are able to be approximated as fast modulation (homogeneous) line shapes because the interaction time with frequency modulation is too short. Compared with them, the libation mode is found to have a relatively slow modulation (inhomogeneous) origin, where disturbance of water hydrogen bonds induced by the hindered translations leads to fluctuations in the libration frequency. more...
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- 2018
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14. 097 An important role of TRPV3 in the temporal control of intracellular acidification in corneoptosis, a unique cell death process of keratinocytes
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Azusa Ishida, Hiroyuki Sasaki, Sonoko Takahashi, Masayuki Amagai, Atsushi Miyawaki, Takaharu Okada, Yuki Furuichi, Keiichiro Shiraga, J. Sharif, Takeshi Matsui, Yasuhiro Suzuki, N. Kadono-Maekubo, K. Toyooka, and Makoto Tominaga more...
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TRPV3 ,Chemistry ,Cell Death Process ,Cell Biology ,Dermatology ,Intracellular acidification ,Molecular Biology ,Biochemistry ,Cell biology - Published
- 2021
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15. Chlorophyll, Carotenoid and Anthocyanin Accumulation in Mung Bean Seedling Under Clinorotation
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Tetsuhito Suzuki, Keiichiro Shiraga, Yuichi Ogawa, Naoshi Kondo, and Shusaku Nakajima
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0106 biological sciences ,General Physics and Astronomy ,01 natural sciences ,010305 fluids & plasmas ,Vigna ,Pigment ,chemistry.chemical_compound ,0103 physical sciences ,Carotenoid ,chemistry.chemical_classification ,Biological pigment ,biology ,Applied Mathematics ,fungi ,General Engineering ,food and beverages ,biology.organism_classification ,carbohydrates (lipids) ,Horticulture ,chemistry ,Seedling ,Modeling and Simulation ,visual_art ,Chlorophyll ,Anthocyanin ,visual_art.visual_art_medium ,Clinostat ,010606 plant biology & botany - Abstract
The accumulation of plant pigments in mung bean (Vigna radiata L.) seedlings was measured after clinorotation (2 rpm for 2-4 days), and compared to a stationary control. The pigments measured included chlorophyll and carotenoid in primary leaves, and the anthocyanin in seedlings. While significant changes in chlorophyll and carotenoid accumulation were not observed during the initial 2 to 4 days of cultivation, by day 4 the seedlings grown on the clinostat had lower levels of anthocyanin, compared to those in the control seedlings. To further detail the cause for the observed reduction in anthocyanin accumulation under altered gravity conditions, seedlings were grown in the presence of silver nitrate, a known ethylene inhibitor, for 4 days, since it is known ethylene has a negative impact on anthocyanin accumulation. Silver nitrate promoted anthocyanin accumulation in the clinostat seedlings, and as a result there was no significant difference between the control and clinostat seedlings in anthocyanin accumulation. The results suggest that slow clinorotation negatively impacts anthocyanin pigmentation in mung bean seedlings, with endogenous ethylene suspected to be involved in this. more...
- Published
- 2017
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16. Characterization of the hydrogen-bond network of water around sucrose and trehalose: H-O-H bending analysis
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Keiichiro Shiraga, Yuichi Ogawa, and Aya Adachi
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Sucrose ,Chemistry ,Hydrogen bond ,Disaccharide ,General Physics and Astronomy ,02 engineering and technology ,Dielectric ,Bending ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Trehalose ,0104 chemical sciences ,Characterization (materials science) ,chemistry.chemical_compound ,Crystallography ,Organic chemistry ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The bioprotective properties of disaccharides have been linked to destructuring effect on the hydrogen-bond structure of the interfacial water around the disaccharide solute, but its detailed mechanisms are yet to be provided. In this study, we characterized the destructuring effect based on the complex dielectric constants of interfacial water around sucrose and trehalose in the H-O-H bending region. Our analysis showed that the destructuring effect around disaccharides involves substantial disordering of the hydrogen-bond structure and formation of strong disaccharide-water hydrogen-bond. Such a destructuring effect caused by disaccharides is totally distinct from what happens with temperature increases of neat water. more...
- Published
- 2017
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17. Potential of front face fluorescence spectroscopy and fluorescence imaging in discriminating adulterated extra-virgin olive oil with virgin olive oil
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Ferruccio Giametta, Dimas Firmanda Al Riza, Keiichiro Shiraga, Tetsuhito Suzuki, Naoshi Kondo, Yuichi Ogawa, Ken Abamba Omwange, and Yoshito Saito
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Excitation emission matrix ,Fluorescence-lifetime imaging microscopy ,Lower grade ,Chromatography ,Chemistry ,Extra-virgin olive oil ,010401 analytical chemistry ,04 agricultural and veterinary sciences ,Health benefits ,Adulteration, Extra-virgin olive oil, Virgin olive oil, Fluorescence imaging ,040401 food science ,01 natural sciences ,Fluorescence imaging ,Fluorescence spectroscopy ,0104 chemical sciences ,Adulteration ,0404 agricultural biotechnology ,Virgin olive oil ,Partial least squares regression ,Food Science ,Biotechnology ,Olive oil - Abstract
Due to the health benefits of extra virgin olive oil (EVOO) and its increasing consumption patterns, adulteration of these oils using lower grade olive oils like virgin olive oil (VOO) and then later sold as EVOO to unsuspecting consumers has become a concern in the industry. There is a need for quick, reliable and inexpensive detection techniques to unmask such vice in order to realize its benefits. In this study, adulteration of EVOO is made using VOO at different proportions; their Excitation Emission Matrices (EEM) were examined using Front-face fluorescence spectroscopy and their corresponding fluorescence images captured using 365 nm ultra-violet (UV) LED for analysis. Specific regions for both the EEM and imaging were explored using Support Vector Machine (SVM) classification analysis and their sensitivities evaluated using Partial Least Squares Regression (PLSR) analysis. It was found that EEM excitation 230–500 and emission 260–620 nm could easily discriminate between different samples as EVOO mixed (at different ratios) and VOO. The significant fluorescence peaks for the discrimination forms a combination of Tocopherols, Tocotrienols, Phenolic compounds, Oxidation products and Vitamin E. The results show that Front-face fluorescence spectroscopy and UV-induced fluorescence imaging can potentially discriminate between pure EVOO and adulterated olive oils. more...
- Published
- 2021
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18. Hydrogen Bond Network of Water around Protein Investigated with Terahertz and Infrared Spectroscopy
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Naoshi Kondo, Yuichi Ogawa, and Keiichiro Shiraga
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Properties of water ,Spectrophotometry, Infrared ,Population ,Biophysics ,Infrared spectroscopy ,02 engineering and technology ,Dielectric ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Humans ,Molecule ,education ,Serum Albumin ,education.field_of_study ,Aqueous solution ,Chemistry ,Hydrogen bond ,Proteins ,Water ,Hydrogen Bonding ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Crystallography ,Chemical physics ,Intramolecular force ,0210 nano-technology - Abstract
The dynamical and structural properties of water at protein interfaces were characterized on the basis of the broadband complex dielectric constant (0.25 to 400 THz) of albumin aqueous solutions. Our analysis of the dielectric responses between 0.25 and 12 THz first revealed hydration water with retarded reorientational dynamics extending ∼8.5 A (corresponding to three to four layers) out from the albumin surface. Second, the number of nonhydrogen-bonded water was decreased in the presence of the albumin solute, indicating protein inhibits the fragmentation of the water hydrogen-bond network. Finally, water molecules at the albumin interface were found to form a distorted hydrogen-bond structure due to topological and energetic disorder of the protein surface. In addition, the intramolecular O-H stretching vibration of water (∼100 THz), which is sensitive to hydrogen-bond environment, pointed to a trend that hydration water has a larger population of strongly hydrogen-bonded water molecules compared with that of bulk water. From these experimental results, we concluded that the "strengthened" water hydrogen bonds at the protein interface dynamically slow down the reorientational motion of water and form the less-defective hydrogen-bond network by inhibiting the fragmentation of water-water hydrogen bonds. Nevertheless, such a strengthened water hydrogen-bond network is composed of heterogeneous hydrogen-bond distances and angles, and thus characterized as structurally "distorted." more...
- Published
- 2016
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19. Hydration and Hydrogen Bond Network of Water during the Coil-to-Globule Transition in Poly(N-isopropylacrylamide) Aqueous Solution at Cloud Point Temperature
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Naoshi Kondo, Keiichiro Shiraga, Yuichi Ogawa, Hirotaka Naito, and Tetsuhito Suzuki
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Models, Molecular ,Cloud point ,Aqueous solution ,Hydrogen bond ,Intermolecular force ,Inorganic chemistry ,Acrylic Resins ,Molecular Conformation ,Water ,Hydrogen Bonding ,Dielectric ,Surfaces, Coatings and Films ,Solutions ,Hydrophobic effect ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Electric Impedance ,Materials Chemistry ,Poly(N-isopropylacrylamide) ,Transition Temperature ,Molecule ,Physical and Theoretical Chemistry ,Hydrogen - Abstract
Aqueous solutions of poly(N-isopropylacrylamide), P-NIPAAm, exhibit a noticeable temperature responsive change in molecular conformation at a cloud point temperature (Tcp). As the temperature rises above Tcp, the extended coil-like P-NIPAAm structure changes into a swollen globule-like conformation as hydration levels decrease and hydrophobic interactions increase. Though water plays an important role in this coil-to-globule transition of P-NIPAAm, the behavior of water molecules and the associated hydrogen-bond (HB) network of the surrounding bulk water are still veiled in uncertainty. In this study, we elucidate changes in the hydration state and the dynamical structure of the water HB network of P-NIPAAm aqueous solutions during the coil-to-globule transition by analyzing the complex dielectric constant in the terahertz region (0.25-12 THz), where bulk water reorientations and intermolecular vibrations of water can be selectively probed. The structural properties of the water HB network were examined in terms of the population of the non-HB water molecules (not directly engaged in the HB network or hydrated to P-NIPAAm) and the tetrahedral coordination of the water molecules engaged in the HB network. We found the hydration number below Tcp (≈10) was decreased to approximately 6.5 as temperature increased, in line with previous studies. The HB network of bulk water becomes more structured as the coil-to-globule phase transition takes place, via decreases in non-HB water and reduction in the orderliness of the tetrahedral HB architecture. Together these results indicate that the coil-to-globule transition is associated with a shift to hydrophobic-dominated interactions that drive thermoresponsive structural changes in the surrounding water molecules. more...
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- 2015
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20. Electric and Electrochemical Properties of Fine Bubble Water and Analysis of the Correlation with Applied Research
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Keiichiro Shiraga, Yoshikatsu Ueda, Yomei Tokuda, Yuichi Ogawa, Akifumi Sugiyama, and Naoto Nihei
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Materials science ,Electrical resistivity and conductivity ,Bubble ,Nanotechnology ,Electrochemistry ,Purified water - Published
- 2015
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21. The Effect of Lactoferrin and Pepsin-Treated Lactoferrin on IEC-6 Cell Damage Induced by Clostridium Difficile Toxin B
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Takayuki Irahara, Hiroyuki Yokota, Takahiro K. Fujiwara, Kosuke Otake, Keiichiro Shiraga, Norio Sato, Yuichi Ogawa, Ayako Kitaguchi, Satoru Murata, and Kaoru Koike
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0301 basic medicine ,030106 microbiology ,Cell ,Bacterial Toxins ,Clostridium difficile toxin B ,Critical Care and Intensive Care Medicine ,Occludin ,medicine.disease_cause ,Microbiology ,Cell Line ,Tight Junctions ,03 medical and health sciences ,Feces ,Bacterial Proteins ,medicine ,Animals ,Intestinal Mucosa ,Cytotoxicity ,Cell damage ,biology ,Lactoferrin ,Toxin ,medicine.disease ,Pepsin A ,Rats ,030104 developmental biology ,medicine.anatomical_structure ,Cell culture ,Emergency Medicine ,biology.protein ,Zonula Occludens-1 Protein - Abstract
Clostridium difficile infections (CDI) have recently increased worldwide. Some CDI progress to fulminant and recurrent CDI and are associated with high mortality and morbidity. CD produces toxins A and B, which cause intestinal mucosal damage, although toxin B exhibits greater cytotoxicity. Pepsin-treated lactoferrin (PLF) is the decomposed product of lactoferrin (LF), a multifunctional glycoprotein with anti-inflammatory properties. Here, we investigate the effects of LF and PLF in toxin B-stimulated rat intestinal epithelial (IEC-6) cells. Different toxin B concentrations were added to IEC-6 cells with or without LF or PLF. Mitochondrial function and cell cytotoxicity were assessed by measuring WST-1 and LDH levels, respectively. WST-1 levels were higher in IEC-6 cells treated with toxin B and LF or PLF, than in the toxin B-only control (P more...
- Published
- 2017
22. Characterization of the hydrogen-bond network of water around sucrose and trehalose: Microwave and terahertz spectroscopic study
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Masahito Nakamura, Keiichiro Shiraga, Yuichi Ogawa, Takuro Tajima, Katsuhiro Ajito, and Aya Adachi
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Sucrose ,Chemical substance ,General Physics and Astronomy ,Nanotechnology ,Cooperativity ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Physical and Theoretical Chemistry ,Sugar ,Microwaves ,Terahertz Spectroscopy ,Aqueous solution ,Hydrogen bond ,Chemistry ,Trehalose ,Water ,Hydrogen Bonding ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Terahertz spectroscopy and technology ,Chaotropic agent ,Chemical physics ,0210 nano-technology - Abstract
Modification of the water hydrogen bond network imposed by disaccharides is known to serve as a bioprotective agent in living organisms, though its comprehensive understanding is still yet to be reached. In this study, aiming to characterize the dynamical slowing down and destructuring effect of disaccharides, we performed broadband dielectric spectroscopy, ranging from 0.5 GHz to 12 THz, of sucrose and trehalose aqueous solutions. The destructuring effect was examined in two ways (the hydrogen bond fragmentation and disordering) and our result showed that both sucrose and trehalose exhibit an obvious destructuring effect with a similar strength, by fragmenting hydrogen bonds and distorting the tetrahedral-like structure of water. This observation strongly supports a chaotropic (structure-breaking) aspect of disaccharides on the water structure. At the same time, hydration water was found to exhibit slower dynamics and a greater reorientational cooperativity than bulk water because of the strengthened hydrogen bonds. These results lead to the conclusion that strong disaccharide-water hydrogen bonds structurally incompatible with native water-water bonds lead to the rigid but destructured hydrogen bond network around disaccharides. Another important finding in this study is that the greater dynamical slowing down of trehalose was found compared with that of sucrose, at variance with the destructuring effect where no solute dependent difference was observed. This discovery suggests that the exceptionally greater bioprotective impact especially of trehalose among disaccharides is mainly associated with the dynamical slowing down (rather than the destructuring effect). more...
- Published
- 2017
23. Applicability of effective medium theory to wood density measurements using terahertz time-domain spectroscopy
- Author
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Keiichiro Shiraga, Yoshihisa Fujii, Soichi Tanaka, Shogo Okumura, and Yuichi Ogawa
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Materials science ,Terahertz radiation ,business.industry ,Mie scattering ,Analytical chemistry ,Relative permittivity ,Computational physics ,Biomaterials ,Wavelength ,Nondestructive testing ,Dielectric loss ,Terahertz time-domain spectroscopy ,business ,Spectroscopy - Abstract
The use of an effective medium theory is important when accurately measuring wood density using millimeter and terahertz wave techniques. To confirm the applicability of this theory to the evaluation of wood density, the relative permittivity and dielectric loss of oven-dry flat-sawn specimens of 11 different wood species were measured in a frequency range of 0.15–1.2 THz using a transmission measurement system for terahertz time-domain spectroscopy. A mixture model based on the effective medium theory well explained the density dependence of relative permittivity over the entire frequency range, while it did not fully explain that of dielectric loss, especially for higher frequencies. This indicates that wood scatters the terahertz wave with a wavelength close to the transverse sectional dimensions of the pores in wood in the same way as Mie scattering. It was found from the dielectric loss spectrum of wood substance that the frequency around 0.23 THz was preferable for the nondestructive evaluation of wood. more...
- Published
- 2014
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24. Highly Sensitive Terahertz Sensing of Glycerol-Water Mixtures with Metamaterials
- Author
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K. Hattori, Mitsuo Wada Takeda, Fumiaki Miyamaru, Yuichi Ogawa, Tsubasa Nishida, S. Suga, Keiichiro Shiraga, and S. Kawashima
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Imagination ,Radiation ,Materials science ,business.industry ,Terahertz radiation ,media_common.quotation_subject ,Metamaterial ,Resonance ,Condensed Matter Physics ,Optics ,Q factor ,Reflection (physics) ,Metamaterial absorber ,Optoelectronics ,Electrical and Electronic Engineering ,Science, technology and society ,business ,Instrumentation ,media_common - Abstract
We demonstrate the highly sensitive terahertz (THz) sensing of a water-glycerol mixture poured on a metamaterial surface using reflection-based THz time domain spectroscopy. The reflectance at the resonant dip frequency changes significantly with glycerol concentration. The detection sensitivity is about 8 times higher than that compared to the case without a metamaterial structure. We also investigate how sensitivity depends on the Q factor of the metamaterial resonance for highly absorptive media, such as a water solution in the THz region. more...
- Published
- 2013
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25. Evaluation of Cell Viability Using Terahertz Attenuated Total Reflection Spectroscopy
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Hirotaka Naito, Naoshi Kondo, Tetsuhito Suzuki, Sakura Tomita, Keiichiro Shiraga, and Yuichi Ogawa
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Materials science ,business.industry ,Terahertz radiation ,Attenuated total reflection ,Optoelectronics ,Viability assay ,business ,Spectroscopy ,Thz spectroscopy - Published
- 2013
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26. Double-beam CW THz system with photonic phase modulator for sub-THz glucose hydration sensing
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Yuichi Ogawa, Takuro Tajima, Katsuhiro Ajito, Keiichiro Shiraga, Hiroshi Koizumi, and Masahito Nakamura
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Materials science ,business.industry ,Terahertz radiation ,Phase (waves) ,Physics::Optics ,02 engineering and technology ,Dielectric ,Signal ,Dielectric spectroscopy ,law.invention ,020210 optoelectronics & photonics ,Optics ,law ,0202 electrical engineering, electronic engineering, information engineering ,Photonics ,business ,Phase modulation ,Beam splitter - Abstract
We present a double-beam dielectric spectroscopic system using an integrated photonic phase modulator for glucose hydration sensing from 0.25 to 1.0 THz. Compact phase modulators with a photonic circuit and a double-beam scheme using a broadband beam splitter enable us to improve signal stability in sub-THz generation and detection. Using the system, we carried out fast vector measurement on glucose solutions with effective signal stabilization. By incorporating a simple calibration procedure for the extraction of dielectric properties, the Fabry-Perot effect in liquid cell window was mitigated. The system demonstrated accurate detection of glucose dielectric spectra for hydration analysis of glucose-water interaction in sub-THz region. more...
- Published
- 2016
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27. Quantitative characterization of hydration state and destructuring effect of monosaccharides and disaccharides on water hydrogen bond network
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N. Kondo, Keiichiro Shiraga, Tetsuhito Suzuki, Yuichi Ogawa, and J. De Baerdemaeker
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chemistry.chemical_classification ,Sucrose ,Hydrogen bond ,Organic Chemistry ,Inorganic chemistry ,Monosaccharides ,Disaccharide ,Water ,Fructose ,Hydrogen Bonding ,General Medicine ,Molecular Dynamics Simulation ,Disaccharides ,Biochemistry ,Trehalose ,Analytical Chemistry ,Solutions ,chemistry.chemical_compound ,chemistry ,Attenuated total reflection ,Organic chemistry ,Molecule ,Monosaccharide - Abstract
Terahertz time-domain attenuated total reflection measurements of monosaccharide (glucose and fructose) and disaccharide (sucrose and trehalose) solutions from 0.146 M to 1.462 M were performed to evaluate (1) the hydration state and (2) the destructuring effect of saccharide solutes on the hydrogen bond (HB) network. Firstly, the extent of hydration water was determined by the decreased amount of bulk water with picosecond relaxation time that was replaced by that with much longer orientational relaxation time. As a result, we found glucose and trehalose exhibits stronger hydration capacity than fructose and sucrose, respectively, despite of the same number of the hydroxyl groups. For each saccharide, the hydration number tended to decrease with solute concentration. Secondly, the destructuring effect of these saccharide solutes on the HB network of the surrounding bulk water was discussed from the perspective of the fraction of non-hydrogen-bonded (NHB) water isolated from the HB network. We found the fraction of NHB water molecules that are not engaged in the HB network monotonously increased with saccharide concentration, indicating saccharide solutes promote the disruption of the water HB network. However, no noticeable differences were confirmed in the fraction of NHB water between glucose and fructose or between sucrose and trehalose. In contrast to hydration number, the number of NHB water produced by a single saccharide solute was less dependent on solute concentration, and three monosaccharide/disaccharide solutes were found to produce one/two NHB water molecules. more...
- Published
- 2014
28. Evaluation of the bulk water dynamics inside HeLa cells using terahertz time-domain attenuated total reflection spectroscopy
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Naoshi Kondo, Keiichiro Shiraga, and Yuichi Ogawa
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Materials science ,Nuclear magnetic resonance ,Hydrogen bond ,Chemical physics ,Terahertz radiation ,Attenuated total reflection ,Picosecond ,Relaxation (NMR) ,Intermolecular force ,Monolayer ,Dielectric - Abstract
In spite of intensive efforts to elucidate the cellular functions and activities of biological macromolecules, such as DNA and proteins, the intermediary role of intracellular water in these activities is still cloaked in mystery. This is because bulk water dynamics, which occur on sub-picosecond and picosecond timescales, cannot be directly probed by conventional experimental techniques. With a periodic electric field on a sub-picosecond or picosecond timescale, terahertz waves are selectively sensitive to the dynamics of the hydrogen bond network associated with the bulk water. We use THz TD-ATR measurements, combined with a two-interface model, to determine the complex dielectric constant of a living cell monolayer, and thus characterize their intracellular water dynamics. Further interrogation was undertaken by decomposing the complex dielectric constant into its slow relaxation, fast relaxation and intermolecular stretching vibration components. The results indicated that intracellular water has a fragile hydrogen bond network, releasing water molecules from the network. Additionally, tetrahedrally coordinated water in the cell interior is structurally disordered compared to the extracellular water. more...
- Published
- 2014
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29. Sensing living cells using a terahertz split-ring resonator with reflection spectroscopy
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Keiichiro Shiraga, Kenta Hattori, Yuichi Ogawa, and Naoshi Kondo
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Materials science ,business.industry ,Terahertz radiation ,Dielectric ,Dielectric spectroscopy ,Absorbance ,Split-ring resonator ,Optics ,Monolayer ,Optoelectronics ,sense organs ,business ,Absorption (electromagnetic radiation) ,Biosensor - Abstract
Studies with THz split ring resonators (THz-SRRs) have revealed the possibility of using them as sensors to monitor changes in the complex dielectric constant of samples. In this regard, THz reflection spectroscopy in combination with a SRR could be used to measure even target samples in aqueous solution since the interference of water's excessive absorption is minimized with this technique. In this letter, we demonstrate that reflectance intensity at the resonant frequency is more sensitive than frequency shift to changes in the imaginary part of the dielectric constant associated with the absorbance of the sample. Moreover, we distinguished significant changes in reflectance between a cell monolayer in a medium cultured directly onto the SRR and the SRR with medium alone. We confirmed that THz-SRR can be a highly sensitive biosensor to monitor changes in the complex dielectric constant of dielectric samples, such as living cells where abundant extracellular water is present. more...
- Published
- 2014
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30. Evaluation of intracellular water dynamics in the picosecond timescales investigated by terahertz spectroscopy
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Keiichiro Shiraga, Motoki Imamura, Tetsuhito Suzuki, Akiyoshi Irisawa, Yuichi Ogawa, and Naoshi Kondo
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Nuclear magnetic resonance ,Hydrogen bond ,Terahertz radiation ,Chemical physics ,Chemistry ,Picosecond ,Molecular biophysics ,Molecule ,Dielectric ,Intracellular ,Terahertz spectroscopy and technology - Abstract
The complex dielectric constant of human cultured cell, HeLa, is determined in the terahertz region. Since they are sensitive to picosecond motions, intracellular water dynamics mediated by hydrogen bonds are discussed. As a result, it is suggested that about 25 % of water molecules are slightly perturbed and hydrogen bonds are more “unstructured” in the cellular milieu, indicating 6 % of total intracellular water molecules are isolated from hydrogen bond network of water. more...
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- 2013
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31. Relation between anisotropic relative permittivity and density of wood evaluated using THz time domain transmission spectroscopy
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Yoshihisa Fujii, S. Tanaka, Keiichiro Shiraga, and Yuichi Ogawa
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Permittivity ,Materials science ,Nuclear magnetic resonance ,business.industry ,Terahertz radiation ,Nondestructive testing ,Relative permittivity ,Fiber ,Time domain ,Composite material ,Anisotropy ,business ,Terahertz spectroscopy and technology - Abstract
To confirm the feasibility of applying THz time domain spectroscopy (TDS) technique to nondestructive evaluation (NDE) of wood, the relation of relative permittivity to density for specimens of 12 wood species was investigated using THz-TDS transmission measurement system. The dielectric anisotropy, the difference in the relative permittivity in the fiber and transverse direction of wood, was also examined. The relative permittivity increased with wood density. The relation between the anisotropy and density was concave downward. These findings indicate that THz-TDS technique can be applied to NDE of wood density and grain direction. more...
- Published
- 2013
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32. Metamaterial application in sensing for living cells
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Akiyoshi Irisawa, Motoki Imamura, Tetsuhito Suzuki, Keiichiro Shiraga, Naoshi Kondo, K. Hattori, and Yuichi Ogawa
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Permittivity ,Materials science ,business.industry ,Terahertz radiation ,Physics::Optics ,Metamaterial ,Dielectric ,Terahertz spectroscopy and technology ,Split-ring resonator ,Optics ,Attenuated total reflection ,Optoelectronics ,Spectroscopy ,business - Abstract
We demonstrated reflection spectroscopy of human cancer cell, DLD-1, cultured in the liquid medium on the metamaterial. Based on the complex dielectric constant of distilled water and DLD-1 monolayer determined by terahertz time-domain attenuated total reflection spectroscopy, we found weakened resonance inherent in the metamaterial in the terahertz frequencies reflects dielectric properties within the field of depth “sampled” (several micrometers from the metamaterial surface in the above case), which is defined by the architecture of the metamaterial. This finding suggests that optimization of a frequency-tunable metamaterial can be used to develop a novel, sensitive, cellular sensor that measures whole cell changes; a result that cannot be realized by conventional approaches. more...
- Published
- 2013
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33. Evaluation of the hydration state of saccharides using terahertz time-domain attenuated total reflection spectroscopy
- Author
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Keiichiro Shiraga, Akiyoshi Irisawa, Yuichi Ogawa, Naoshi Kondo, and Motoki Imamura
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Steric effects ,Models, Molecular ,Terahertz Spectroscopy ,Chemistry ,Terahertz radiation ,Analytical chemistry ,Carbohydrates ,Water ,General Medicine ,Analytical Chemistry ,Chemical physics ,Picosecond ,Attenuated total reflection ,Molecule ,Time domain ,Spectroscopy ,Refractive index ,Hydrophobic and Hydrophilic Interactions ,Food Science - Abstract
Despite intensive studies regarding the hydration state, experimental investigations have not fully explained the global hydration state. Terahertz (THz) spectroscopy is an emerging technology that has the potential to evaluate global hydration. This is because THz waves are very sensitive to picosecond water dynamics and, as such, effectively measures the state of water that is weakly bound to solute molecules by observing slowed down water dynamics. THz time-domain attenuated total reflection (THz TD-ATR) spectroscopy allowed to determine the complex refractive index of saccharide solutions and to experimentally characterize the global hydration state. Our result indicates the global hydration state is closely related to the number of hydrophilic groups and steric configuration of hydroxyl groups in saccharide molecules. This new tool to investigate the global hydration state will provide new knowledge about water dynamics around solutes that couldn’t have been elucidated with the conventional techniques. more...
- Published
- 2012
34. Hydration state inside HeLa cell monolayer investigated with terahertz spectroscopy
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Naoshi Kondo, Keiichiro Shiraga, Yuichi Ogawa, Tetsuhito Suzuki, and Koichiro Tanaka
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chemistry.chemical_classification ,Physics and Astronomy (miscellaneous) ,biology ,Chemistry ,Biomolecule ,Relaxation (NMR) ,biology.organism_classification ,Terahertz spectroscopy and technology ,HeLa ,Crystallography ,Attenuated total reflection ,Monolayer ,Biophysics ,Spectroscopy ,Intracellular - Abstract
The hydration state in living cells is believed to be associated with various cellular activities. Nevertheless, in vivo characterization of intracellular hydration state under physiological condition has not been well documented to date. In this study, the hydration state of an intact HeLa cell monolayer was investigated by terahertz time-domain attenuated total reflection spectroscopy. Combined with the extended theory of Onsager, we found 23.8 ± 7.4% of HeLa intracellular water was hydrated to biomolecules (corresponding to 1.25 g H[2]O/g solute); exhibiting slower relaxation dynamics than bulk water. more...
- Published
- 2015
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35. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy
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Yuichi Ogawa, Keiichiro Shiraga, Naoshi Kondo, and Tetsuhito Suzuki
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Terahertz Spectroscopy ,chemistry.chemical_classification ,Surface Properties ,Hydrogen bond ,Stereochemistry ,Solvation ,Water ,General Physics and Astronomy ,Hydrogen Bonding ,Dielectric ,Amino acid ,Hydrophobic effect ,chemistry.chemical_compound ,Crystallography ,chemistry ,Side chain ,Molecule ,Amino Acids ,Physical and Theoretical Chemistry ,Methylene ,Hydrophobic and Hydrophilic Interactions - Abstract
Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network. more...
- Published
- 2014
- Full Text
- View/download PDF
36. Determination of the complex dielectric constant of an epithelial cell monolayer in the terahertz region
- Author
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Yuichi Ogawa, Akiyoshi Irisawa, Keiichiro Shiraga, Naoshi Kondo, Motoki Imamura, and Tetsuhito Suzuki
- Subjects
Permittivity ,Physics and Astronomy (miscellaneous) ,Chemistry ,Chemical physics ,Terahertz radiation ,Attenuated total reflection ,Relaxation (NMR) ,Monolayer ,Analytical chemistry ,Dielectric ,Absorption (chemistry) ,Terahertz spectroscopy and technology - Abstract
We present a method to determine the complex dielectric constant of a cell monolayer using terahertz time-domain attenuated total reflection spectroscopy combined with a two-interface model. The imaginary part of the dielectric constant of the cell monolayer shows a lower absorption of slow relaxation mode than that of the liquid medium. This result allows us to estimate the intracellular water dynamics on a picosecond time scale, and the existence of weakly hydrated water molecules inside the cell monolayer was indicated. This method will provide a perspective to investigate the intracellular water dynamics in detail. more...
- Published
- 2013
- Full Text
- View/download PDF
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