Papers - YAMAMOTO Masahiro
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Prediction of the Standard Gibbs Energy of Transfer of Organic Ions Across the Interface between Two Immiscible Liquids Reviewed
Toshiyuki Osakai, Yasuhiro Naito, Kazuo Eda, Masahiro Yamamoto
Journal of Physical Chemistry B 119 ( 41 ) 13167 - 13176 2015.10
Joint Work
© 2015 American Chemical Society. The non-Bornian solvation model was applied for evaluation of the standard Gibbs energy (δGtr°,W→O) of transfer of organic ions from water (W) to organic solvent (O = nitrobenzene). The solvation energy of an ion in either W or O is basically formulated as the energy required for the formation of a nanosized ion-solvent interface around the ion; however, many organic ions with strongly charged groups (e.g., -SO3-, -CO2-, -NH3+) are preferentially hydrated in O. Here we divided the surface of an ion into hydrated and non-hydrated surfaces and then carried out regression analyses with experimental values of δGtr°,W→O. In the analyses, the local electric field on the surface of an organic ion was evaluated through density functional theory calculation. Good regression results were then obtained with the mean absolute error of 1.9 and 2.4 kJ mol-1 for 34 anions and 63 cations, respectively. These errors correspond to the error of 20 mV in the standard ion-transfer potential (δOWφ°), being only two times larger than the typical experimental error (10 mV) in the voltammetric measurement. This non-Bornian model is promising for theoretical prediction of δGtr°,W→O (or δOWφ°) for organic ions and possibly of the biomembrane permeability for ionic drugs.
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Role of 2-mercaptoethanol in direct electron transfer-type bioelectrocatalysis of fructose dehydrogenase at Au electrodes Reviewed
Yu Sugimoto, Yuki Kitazumi, Osamu Shirai, Masahiro Yamamoto, Kenji Kano
Electrochimica Acta 170 242 - 247 2015.7
Joint Work
Publisher：PERGAMON-ELSEVIER SCIENCE LTD
© 2015 Elsevier Ltd. All rights reserved. Effects of the electrode potential on a direct electron transfer (DET)-type bioelectrocatalysis of fructose dehydrogenase (FDH) at Au electrodes were investigated. Adsorbed FDH showed the highest DET activity at an adsorption potential (E<inf>ad</inf>) around the point of zero charge (E<inf>pzc</inf>). Since FDH stock solution contains 2-mercaptoethanol (ME) for stabilization, ME is partially bound to the Au electrode. However, the DET activity drastically decreased at E<inf>ad</inf> >> E<inf>pzc</inf>. Au oxide layer is formed at the positive potentials to hinder the interfacial electron transfer. In contrast, only slight decrease in the DET activity was observed at sufficiently negative E<inf>ad</inf> (<<E<inf>pzc</inf>), where ME is reductively desorbed from the Au electrode, but co-exists in the solution. In contrast, when FDH and ME were adsorbed on Au electrodes at an open circuit potential and the FDH- and ME-adsorbed Au electrode was held at such a negative hold potential (E<inf>ho</inf>) in the buffer without ME, the DET activity drastically decreased. An addition of ME in the test solution prevented the decrease in the DET activity at the negative E<inf>ho</inf>. These results indicate that ME close to adsorbed FDH plays a significant role in the stabilization of FDH adsorbed on Au electrodes.
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Yuta Otsuka, Masahiro Yamamoto, Hideji Tanaka, Makoto Otsuka
Bio-Medical Materials and Engineering 25 ( 3 ) 223 - 236 2015.6
Joint Work
Publisher：IOS Press
© 2015 - IOS Press and the authors. All rights reserved. BACKGROUND: Theophylline anhydrate (TA) in tablet formulation is transformed into monohydrate (TH) at high humidity and the phase transformation affected dissolution behavior. OBJECTIVE: Near-infrared spectroscopic (NIR) method is applied to predict the change of pharmaceutical properties of TA tablets during storage at high humidity. METHODS: The tablet formulation containing TA, lactose, crystalline cellulose and magnesium stearate was compressed at 4.8 kN. Pharmaceutical properties of TA tables were measured by NIR, X-ray diffraction analysis, dissolution test and tablet hardness. RESULTS: TA tablet was almost 100% transformed into TH after 24 hours at RH 96%. The pharmaceutical properties of TA tablets, such as tablet hardness, 20 min dissolution amount (D20) and increase of tablet weight (TW), changed with the degree of hydration. Calibration models for TW, tablet hardness and D20 to predict the pharmaceutical properties at high-humidity conditions were developed on the basis of the NIR spectra by partial least squares regression analysis. The relationships between predicted and actual measured values for TW, tablet hardness and D20 had straight lines, respectively. CONCLUSIONS: From the results of NIR-chemometrics, it was confirmed that these predicted models had high accuracy to monitor the tablet properties during storage at high humidity.
DOI： 10.3233/BME-151278
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Coextraction of water into nitrobenzene with organic ions Reviewed
Yasuhiro Naito, Wataru Murakami, Kazuo Eda, Masahiro Yamamoto, Toshiyuki Osakai
Journal of Physical Chemistry B 119 ( 19 ) 6010 - 6017 2015.5
Joint Work
© 2015 American Chemical Society. Various organic anions (sulfonates (RSO<inf>3</inf><sup>-</sup>), carboxylates (RCO<inf>2</inf><sup>-</sup>), and phenolates (RO<sup>-</sup>)) and ammonium cations (RNH<inf>3</inf><sup>+</sup>, R<inf>2</inf>NH<inf>2</inf><sup>+</sup>, and R<inf>3</inf>NH<sup>+</sup>) were distributed in the nitrobenzene (NB)-water system by using Crystal Violet and dipicrylaminate, respectively. The number of water molecules (n) being coextracted into NB with an ion was then determined by the Karl Fischer method. The n values determined and those reported previously showed the variation from 0.51 to 3.4, depending on not only the charged groups but also the noncharged R-groups. In this study, we focused our attention to the strong electric field on the charged group and its facilitation effect for binding water molecules in NB. The local electric field (E<inf>i</inf>) on the surface of an organic ion was evaluated by using Gaussian09 program with a subprogram developed in our recent study. It was found that the n values showed a clear dependence on the average value of E<inf>i</inf> on oxygen or hydrogen atoms, respectively, of an anionic or cationic group.
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A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging Reviewed
Haruki Eguchi, Masanari Umemura, Reiko Kurotani, Hidenobu Fukumura, Itaru Sato, Jeong Hwan Kim, Yujiro Hoshino, Jin Lee, Naoyuki Amemiya, Motohiko Sato, Kunio Hirata, David J. Singh, Takatsugu Masuda, Masahiro Yamamoto, Tsutomu Urano, Keiichiro Yoshida, Katsumi Tanigaki, Masaki Yamamoto, Mamoru Sato, Seiichi Inoue, Ichio Aoki, Yoshihiro Ishikawa
Scientific Reports 5 2015.3
Joint Work
Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.
DOI： 10.1038/srep09194
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Electrostatic interaction between an enzyme and electrodes in the electric double layer examined in a view of direct electron transfer-type bioelectrocatalysis Reviewed
Yu Sugimoto, Yuki Kitazumi, Seiya Tsujimura, Osamu Shirai, Masahiro Yamamoto, Kenji Kano
Biosensors and Bioelectronics 63 138 - 144 2015.1
Joint Work
Publisher：ELSEVIER ADVANCED TECHNOLOGY
Effects of the electrode poential on the activity of an adsorbed enzyme has been examined by using copper efflux oxidase (CueO) as a model enzyme and by monitoring direct electron transfer (DET)-type bioelectrocatalysis of oxygen reduction. CueO adsorbed on bare Au electrodes at around the point of zero charge (Epzc) shows the highest DET activity, and the activity decreases as the adsorption potential (Ead; at which the enzyme adsorbs) is far from Epzc. We propose a model to explain the phenomena in which the electrostatic interaction between the enzyme and electrodes in the electric double layer affects the orientation and the stability of the adsorbed enzyme. The self-assembled monolayer of butanethiol on Au electrodes decreases the electric field in the outside of the inner Helmholtz plane and drastically diminishes the Ead dependence of the DET activity of CueO. When CueO is adsorbed on bare Au electrodes under open circuit potential and then is held at hold potentials (Eho) more positive than Epzc, the DET activity of the CueO rapidly decreases with the hold time. The strong electric field with positive surface charge density on the metallic electrode (σM) leads to fatal denaturation of the adsorbed CueO. Such denaturation effect is not so serious at Eho<<Epzc, but the electric field with negative σM induces an orientation inconvenient for the DET reaction during the adsorption process. A positively charged neomycin shows a promoter ability to CueO adsorbed at Ead<<Epzc. The phenomenon is also explained on the proposed model. © 2014 Elsevier B.V.
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Coextraction of Water into Nitrobenzene with Organic Ions Reviewed
Y. Naito et al.
J. Phys. Chem. B 2015
Joint Work
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Electrostatic interaction between an enzyme and electrodes in the electric double layer examined in a view of direct electron transfer-type bioelectrocatalysis Reviewed
Yu Sugimoto et al.
Biosensors and Bioelectronics 2015
Joint Work
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A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging Reviewed
Yoshihiro Ishikawa et al.
Scientific Reports 2015
Joint Work
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Role of 2-mercaptoethanol in direct electron transfer-type bioelectrocatalysis of fructose dehydrogenase at Au electrodes Reviewed
Y. Sugimoto et al.
Electrochimica Acta 2015
Joint Work
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Predictive evaluation of pharmaceutical properties of direct compression tablets containing theophylline anhydrate during storage at high humidity by near-infrared spectroscopy Reviewed
Y. Otsuka et al.
Bio-Medical Materials and Engineering 2015
Joint Work
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Prediction of the Standard Gibbs Energy of Transfer of Organic Ions Across the Interface Between Two Immiscible Liquids Reviewed
Osakai, Toshiyuki et al.
J. Phys. Chem. B 2015
Joint Work
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Characteristics of fast mediated bioelectrocatalytic reaction near microelectrodes Reviewed
Yuki Kitazumi, Tatsuo Noda, Osamu Shirai, Masahiro Yamamoto, Kenji Kano
Physical Chemistry Chemical Physics 16 ( 19 ) 8905 - 8910 2014.5
Joint Work
The pseudo-steady-state current due to a mediated enzymatic reaction on a microelectrode is characterized on the basis of theoretical analysis and numerical simulation. The steady-state current is proportional to substrate concentration when the enzymatic reaction is considerably faster than substrate mass transport via nonlinear diffusion. Under such conditions, the reaction plane, where the mass flow of the substrate is converted to that of the mediator, exists near the electrode surface. The steady-state current increases as the diffusion coefficient of the substrate increases. In contrast, the diffusion coefficient and the concentration of the mediator have minor effects on the current. This difference can be explained on the basis of a change in the reaction plane location. When a sufficient amount of enzyme exists in a system, the system can be used as an amperometric biosensor, the response of which is independent of any change in enzyme activity. This journal is © the Partner Organisations 2014.
DOI： 10.1039/c4cp00141a
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Effects of the density difference between water and oil on stabilization of powdered oil-in-water emulsions Reviewed
Ryo Murakami, Hiroshi Moriyama, Tatsuyuki Noguchi, Masahiro Yamamoto, Bernard P. Binks
Langmuir 30 ( 2 ) 496 - 500 2014.1
Joint Work
A powdered oil-in-water (o/w) emulsion is a dispersed system in which the continuous phase of a particle-stabilized o/w emulsion is dispersed in air by encapsulating the water globules with hydrophobic particles. During their preparation, oil droplets in water globules are forced to move because of high-shear mixing, leading to creaming of the oil droplets and possible wetting of the hydrophobic particles with the oil droplets, which induces destabilization. To prepare powdered o/w emulsions efficiently, the extent of creaming of the oil droplets has to be suppressed. We describe how to achieve this by mixing two oils of different densities and preparing powdered o/w emulsions from oil mixtures exhibiting a decreasing density difference with water. As the extent of creaming is reduced, enhanced stabilization of the powdered emulsions occurs. © 2013 American Chemical Society.
DOI： 10.1021/la4042056
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Characteristics of fast mediated bioelectrocatalytic reaction near microelectrodes Reviewed
Y. Kitazumi et al.
Phys. Chem. Chem. Phys. 2014
Joint Work
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A Non-Bornian Analysis of the Gibbs Energy of Ion Hydration Reviewed
W. Murakami et al.
Bull. Chem. Soc. Jpn. 2014
Joint Work
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Effects of the Density Difference between Water and Oil on Stabilization of Powdered Oil-in-Water Emulsions
R .Murakami et al.
Langmuir 2014
Joint Work
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A non-Bornian analysis of the Gibbs energy of hydration for organic ions Reviewed
R. Murakami et al.
RSC. Adv. 2014
Joint Work
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A non-Bornian analysis of the Gibbs energy of hydration for organic ions
Wataru Murakami, Masahiro Yamamoto, Kazuo Eda, Toshiyuki Osakai
RSC Advances 4 ( 53 ) 27634 - 27641 2014
Joint Work
Recently, a non-Bornian model was successfully applied to evaluate the Gibbs energy of hydration (ΔG°hyd) for spherical ions (mainly inorganic ions). In this model, the long-range, Born-type electrostatic ion-solvent interaction is not explicitly included in the calculation of ΔG°hyd, since its contribution is small, whereas the short-range interaction, including Coulomb, polarization, and charge-transfer interactions, is considered as the dominant factor that determines the ΔG°hyd of ions. The ΔG°hyd scaled by the surface area of an ion can be given by a quadratic function of the surface field strength (E) of the ion. In this study, the non-Bornian model was further applied to organic ions with charged groups. Using the Gaussian 09 program package, the geometries of ions in vacuum were optimized at the B3LYP/6-311++G(2d,p) level, and the partial atomic charges were computed in the Mulliken, Merz-Kollman (MK), natural population analysis (NPA), Hirshfeld, and ChelpG methods. Introducing a new subprogram, we could estimate local electric fields on the ion surface (van der Waals surface or solvent-accessible surface (SAS)). This enabled us to perform regression analyses based on the non-Bornian model, by using the experimental values of ΔG°hyd for 109 ions. When the NPA-SAS combination was chosen, the best regression result was obtained, giving the mean absolute error of 4.3 kcal mol-1. The non-Bornian model would provide a simple and relatively accurate way of determining ΔG°hyd of ions. This journal is © the Partner Organisations 2014.
DOI： 10.1039/c4ra02422b
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A non-bornian analysis of the gibbs energy of ion hydration
Wataru Murakami, Kazuo Eda, Masahiro Yamamoto, Toshiyuki Osakai
Bulletin of the Chemical Society of Japan 87 ( 3 ) 403 - 411 2014
Joint Work
A non-Bornian model for understanding the Gibbs energy of ion hydration (δG°hyd) has been proposed, in which only short-range interactions between an ion and solvent molecules adjacent to the ion are considered, while the longrange electrostatic interaction between the ion and the outer bulk solvent is not explicitly included in the model. As the short-range interactions, Coulomb, polarization, and charge-transfer interactions are taken into account. It has thus been shown that the δG°hyd scaled by the solvent-accessible surface (SAS) area of an ion can be given by a quadratic function of the electric field strength E at the SAS. Regression analyses with the derived analytical equation have been performed for the literature values of δG°hyd for spherical ions, including 85 cations (with the charge number, z = 1 to 4) and 53 anions (with z = 1 and 2); good fitting results have been obtained for either the cations or the anions. An additional regression analysis has been performed for 10 representative cations, using the data set employed by Koehl et al. (J. Phys. Chem. B 2009, 113, 5694). Our non-Bornian model has been found to be one of the highest performance models for the prediction of δG°hyd. © 2013 The Chemical Society of Japan.