Faculty Profiles - TAKEOKA, Yukikazu

Papers - TAKEOKA, Yukikazu

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Reversible adsorption of calcium ions by imprinted temperature sensitive gels Reviewed

C Alvarez-Lorenzo, O Guney, T Oya, Y Sakai, M Kobayashi, T Enoki, Y Takeoka, T Ishibashi, K Kuroda, K Tanaka, GQ Wang, AY Grosberg, S Masamune, T Tanaka

JOURNAL OF CHEMICAL PHYSICS Vol. 114 ( 6 ) page： 2812 - 2816 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, copolymer gels of N-isopropylacrylamide (NIPA) and methacrylic (MAA) monomers were prepared. We chose calcium as a target divalent ion. Two MAAs form a complex with a calcium ion, and the NIPA component allows the polymers to swell and shrink reversibly in response to temperature. The adsorbing site develops an affinity to target ions when the adsorbing molecules come into proximity, but when they are separated, the affinity diminishes. To enhance the affinity to calcium, an imprinting technique was applied using Ca2+ and Pb2+ ions as templates in methylsulfoxide and dioxane media, respectively. The adsorption capacity of the imprinted gels was compared with that of the nonimprinted gels, and the effects of the templates, the solvents, and the amount of methacrylic monomers used in the synthesis and the medium temperature over the Ca2+ adsorption capacity of the gels from aqueous solutions were evaluated. The analysis of the adsorption revealed that (a) the adsorption can be described by the Langmuir isotherms; (b) there is an approximately linear relationship between saturation and methacrylic monomer concentration; (c) the affinity depends on the degree of gel swelling or shrinkage that can be switched on and off by temperature; (d) in the shrunken state, the affinity depends approximately linearly on the MAA concentration in the imprinted gels, whereas in the nonimprinted gels it is proportional to the square of MAA concentration; (e) the imprinted gels adsorb more than the nonimprinted gels when MAA concentration is less than that of permanent cross linkers. The success of imprinting of CaMAA(2) and PbMAA(2) complex is evidence for memory of such complex onto the weakly cross-linked gel. (C) 2001 American Institute of Physics.

Web of Science

Reversible adsorption of calcium ions by imprinted temperature sensitive gels Reviewed

Carmen Alvarez-Lorenzo, Orhan Guney, Taro Oya, Yasuzo Sakai, Masatoshi Kobayashi, Takashi Enoki, Yukikazu Takeoka, Toru Ishibashi, Kenichi Kuroda, Kazunori 8Tanaka, Guoqiang Wang, Alexander Yu. Grosberg, Satoru Masamune, and Toyoichi Tanaka

J. Chem. Phys. Vol. 114 ( 6 ) page： 2812-2816 2001

Frustrations in polymer conformation in gels and their minimization through molecular imprinting Reviewed

T Enoki, K Tanaka, T Watanabe, T Oya, T Sakiyama, Y Takeoka, K Ito, GQ Wang, M Annaka, K Hara, R Du, J Chuang, K Wasserman, AY Grosberg, S Masamune, T Tanaka

PHYSICAL REVIEW LETTERS Vol. 85 ( 23 ) page： 5000 - 5003 2000.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMERICAN PHYSICAL SOC

We report an experimental realization of a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers. The gels consist of a thermosensitive major monomer component and two minor components. One minor component is positively charged and will form complexes around negatively charged target molecules placed in solution. The complexes can be imprinted into the gel by then cross-linking the second minor component, which will form cross-links additional to those in the major polymer matrix. The complexes are destroyed and reformed upon swelling and reshrinking of the gels, showing that memorization has been achieved.

Web of Science

Polymer gels that memorize elements of molecular conformation Reviewed

C Alvarez-Lorenzo, O Guney, T Oya, Y Sakai, M Kobayashi, T Enoki, Y Takeoka, T Ishibashi, K Kuroda, K Tanaka, GQ Wang, AY Grosberg, S Masamune, T Tanaka

MACROMOLECULES Vol. 33 ( 23 ) page： 8693 - 8697 2000.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Weakly cross-linked heteropolymer gels that memorize molecular pairs have been designed and synthesized. The polymer consists of a main monomer component responsible for volume phase transition, methacrylic acid that adsorbs one divalent ion as a pair, and cross-links; The memory of pairing of methacrylic acids within the gels was encoded in the primary sequence of main monomers, methacrylic acids and cross-links within the gels, which was achieved by "imprinting", namely, by synthesizing gels while methacrylic monomers were paired prior to polymerization. The control gels, where methacrylic monomers were randomly distributed, showed frustration in forming pairs, whereas such frustration was completely diminished in the imprinted gels allowing the memory of pair formation.

Web of Science

Gel catalysts that switch on and off Reviewed

GQ Wang, K Kuroda, T Enoki, A Grosberg, S Masamune, T Oya, Y Takeoka, T Tanaka

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vol. 97 ( 18 ) page： 9861 - 9864 2000.8

Language：English Publishing type：Research paper (scientific journal) Publisher：NATL ACAD SCIENCES

We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol/water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity, In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics, Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate.

Web of Science

Study of the correlation of the cyclic voltammetric responses of a nonionic surfactant containing an anthraquinone group with the dissolved states Reviewed

Md. Abu Bin Hasan Susan, Mahbuba Begum, Yukikazu Takeoka, Masayoshi Watanabe

Langmuir Vol. 16 ( 7 ) page： 3509 - 3516 2000.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS

Cyclic voltammetric behavior of a nonionic surfactant, α-(anthraquinonyloxyhexyl)-ω-hydroxy-oligo-(ethylene oxide), ACPEG, has been studied in detail in aqueous media with NaCl as the supporting electrolyte. Attempts have been made to correlate the electrochemical responses with the dissolved states of the surfactant. The shapes of the cyclic voltammograms at a glassy carbon electrode have proved to be fairly dependent on the concentration of ACPEG and on the redox state of the anthraquinone group. Below the critical micelle concentration (cmc), the cyclic voltammogram (v = 10 mV/s) corresponds to the surfactant molecules adsorbed onto the electrode surface. The adsorption of ACPEG molecules at the electrode surface is very weak in nature owing to its low surface activity. A high cmc value and weak adsorption allow diffusion of the monomeric species prior to the reduction to contribute to the total current even below the cmc. At concentrations higher than the cmc, the diffusion-controlled waves are superimposed on the surface waves, and far above the cmc, the voltammetric shape is of a typical diffusion-controlled species. Above the cmc, self-association of ACPEG results in the formation of micellar aggregates, which diffuse to the electrode surface to dominate the adsorption wave. The redox process is influenced by the formation of a quinhydrone-like charge transfer complex. The cyclic voltammetrically determined apparent diffusion coefficient of the micellar solutions changes continuously with concentration
with decreasing concentration the apparent diffusion coefficient approaches the monomeric diffusion coefficient while with increasing concentration it approaches the micellar value. This has been interpreted in terms of change in the diffusion species by dissociation of the micelles formed above the cmc to monomers in the concentration gradient in the diffusion layers. The formation and dissociation reaction can be reversibly controlled by a change in the redox state. A CEC mechanism with the electrochemical reaction coupled with the preceding disruption reaction of the micelles (CE) and the following protonation reaction of the reduced state (EC) has been inferred.

DOI： 10.1021/la991033z

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Effect of pH and the extent of micellization on the redox behavior of non-ionic surfactants containing an anthraquinone group Reviewed

MA Susan, M Begum, Y Takeoka, M Watanabe

JOURNAL OF ELECTROANALYTICAL CHEMISTRY Vol. 481 ( 2 ) page： 192 - 199 2000.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Cyclic voltammetry has been employed for the study of aqueous electrochemistry of the surfactants, alpha-(anthraquinonyloxyhexyl)-omega-hydroxy-oligo(ethylene oxide) (ACPEG) and alpha-anthraquinonyl-omega-hydroxy-oilgo (ethylene oxide) (APEG), which have wide differences in surface activity. Potential-pH diagrams have been constructed and the various features of the diagrams have been analyzed in the light of the change in solution equilibria and the difference in the extent of micellization. The redox potentials of the surfactants have been found to exhibit strong pH dependence. The electrode reaction involves two-electron reduction of anthraquinone (AQ) to its dianion (AQ(2-)), which is highly sensitive to the pH of the solution. At controlled pH, potential-pH plots allow the establishment of the values of the ionization constants for dihydroanthraquinone (AQH(2)) and its monoanion (AQH(-)) as pK(a)(1) = 7.83 and pK(a)(2) = 11.38, respectively. Under unbuffered conditions, the effective pH close to the electrode surface controls the potential of the electrode process. The changeover from the H+-available to the H+-depleted electrode process gives rise to a sudden jump in potential. In highly alkaline solutions, AQ forms an adduct with hydroxyl ion, which causes a linear decrease in the potentials with increase in pH. The different extent of micellization results in a difference in the peak current and the half wave potentials (E-1/2) for ACPEG and APEG but causes no significant change in the shapes of the E-1/2-DH diagrams. This has been explained in terms of the disruption reaction of the micelles, preceding the electrochemical reaction. (C) 2000 Elsevier Science S.A. All rights reserved.

Web of Science

A study to correlate the electrochemical responses of a non-ionic surfactant containing an anthraquinine group with the dissolved states Reviewed

Susan, M.A.B.H, Begum, M, Takeoka, Y, Watanabe, M

Langmuir Vol. 16 page： 3509-3516 2000

Frustrations in polymer conformation in gels and their minimization through molecular imprinting Reviewed

Takashi Enoki, Kazunori Tanaka, Tsuyoshi Watanabe, Taro Oya, Takaharu Sakiyama, Yukikazu Takeoka, Kenji Ito, Guoqiang Wang, Masahiko Annaka, Kazuhiro Hara, Rose Du, Jeffrey Chuang, Kevin Wasserman, Alexander Yu. Grosberg, Satoru Masamune, and Toyoichi Tanaka

Phys. Rev. Lett. Vol. 85 page： 5000-5003 2000

A study to correlate the electrochemical responses of a non-ionic surfactant containing an anthraquinine group with the dissolved states Reviewed

Susan, M.A.B.H., Begum, M., Takeoka, Y. and Watanabe, M.

Langmuir Vol. 16 page： 3509-3516 2000

Effect of pH and the extent of micellization on the redox behavior of non-ionic surfactants containing an anthraquinone group Reviewed

Susan, M.A.B.H., Begum, M., Takeoka, Y. and Watanabe, M.

J. Electroanal. Chem. Vol. 481 page： 192-199 2000

Polymer Gels That Memorize Elements of Molecular Conformation Reviewed

Alvarez-Lorenzo, Carmen; Guney, Orhan; Oya, Taro; Sakai, Yasuzo; Kobayashi, Masatoshi; Enoki, Takashi; Takeoka, Yukikazu; Ishibashi, Toru; Kuroda, Kenichi, Alexander Grosberg, and Toyoichi Tanaka

Macromolecules Vol. 33 page： 8693-8697 2000

Gel catalysts that switch on and off Reviewed

Guoqiang Wang, Kenichi Kuroda, Takashi Enoki, Alexander Grosberg, Satoru Masamune, Taro Oya, Yukikazu Takeoka, and Toyoichi Tanaka

Proc. Natl. Acad. Sci. USA Vol. 97 page： 9861-9864 2000

Reversible molecular adsorption based on multiple-point interaction by shrinkable gels Reviewed

T Oya, T Enoki, AY Grosberg, S Masamune, T Sakiyama, Y Takeoka, K Tanaka, GQ Wang, Y Yilmaz, MS Feld, R Dasari, T Tanaka

SCIENCE Vol. 286 ( 5444 ) page： 1543 - 1545 1999.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER ASSOC ADVANCEMENT SCIENCE

A general approach is presented for creating polymer-gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule, Multiple-point interaction is experimentally proven by power Laws found between the affinity and the concentration of the adsorbing monomers within the gels.

Web of Science

First order phase transition and evidence for frustrations in polyampholytic gels Reviewed

Y Takeoka, AN Berker, R Du, T Enoki, A Grosberg, M Kardar, T Oya, K Tanaka, GQ Wang, XH Yu, T Tanaka

PHYSICAL REVIEW LETTERS Vol. 82 ( 24 ) page： 4863 - 4865 1999.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMERICAN PHYSICAL SOC

Polyampholyte gel, frustrated by the conflicting interactions between its positive and negative monomers, c-an undergo a sharp discontinuous phase transition driven by changing either gel composition or solvent quality and/or permeability. This finding completes the investigation of all four major interactions involved in the biomolecular machinery with respect to their role in the behavior of polymer gels, considered here as a model of biopolymer system. The result also sheds light on the possible role of frustrations in biomolecular systems, such as proteins. [S0031-9007(99)09334-5].

Web of Science

First Order Phase Transition and Evidence for Frustrations in Polyampholyte Gels Reviewed

Yukikazu Takeoka, A. Nihat Berker, Rose Du, Takashi Enoki, Alexander Grosberg, Mehran Kardar, Taro Oya, Kazunori Tanaka, Guoqiang Wang, Xiaohong Yu, Toyoichi Tanaka

Phys. Rev. Lett. Vol. 82 page： 4863-4865 1999

Reversible Molecular Adsorption Based on Multiple-Point Interaction by Shrinkable Gels Reviewed

Taro Oya, Takashi Enoki, Alexander Yu. Grosberg, Satoru Masamune, Takaharu Sakiyama, Yukikazu Takeoka, Kazunori Tanaka, Guoqiang Wang, Yasar Yilmaz, Michael S. Feld, Ramachandra Dasari, and Toyoichi Tanaka

Science Vol. 286 page： 1543-1545 1999

Reversible molecular adsorption as a tool to observe freezing and to perform design of heteropolymer gels Reviewed

T Tanaka, T Enoki, AY Grosberg, S Masamune, T Oya, Y Takaoka, K Tanaka, CN Wang, GQ Wang

BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 102 ( 11 ) page： 1529 - 1533 1998.11

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Protein folding is one of the most challenging problems in science. How can polymers memorize and fold into unique conformations? How can they recognize molecules, catalyze chemical reactions, transfer molecular information, and create motions? The principle behind these mechanisms lies in the concept of thermodynamically stable phases of heteropolymers. Recent theories predict that the collapsed phase should be further classified into three phases: freely fluctuating like liquid, frozen in degenerate conformations, and frozen in a unique conformation. This yields a clue on how one can attempt creation artificial polymers capable to mimic some of the protein properties and functions. The reversible adsorption of target molecules is suggested as a primary means to achieve this goal. Target molecules with multiple adsorption sites play a twofold role. First, they mediate specific interactions between monomers and thus serve as "gluons". Second, monitoring the adsorption provides the experimental possibility to test directly on monomer contacts, which is directly related to observation of the order parameter associated with heteropolymer freezing transition. A slight change in the backbone conformation alters the spacial arrangement of the group, allowing for reversible adsorption and release. Polymer gels are developed that can reversibly change their affinity to target molecules by orders of magnitude. The gels are made of copolymers of backbone monomers that can reorganize themselves through thermal volume phase transition and of monomers that can attract the target at multiple contact points. Further the gels "imprinted" with the target showed a marked increase in the affinity, thus mimicing a protein-like ability to memorize and recognize certain target.

Web of Science

Reversible molecular adsorption as a tool to observe freezing and to perform design of heteropolymer gels Reviewed

Tanaka, Toyoichi; Enoki, Takashi; Grosberg, Alexander Y.; Masamune, Satoru; Oya, Taro; Takaoka, Yukikazu; Tanaka, Kazunori; Wang, Changnan; Wang, Guoqiang.

Ber. Bunsen-Ges. Vol. 102 ( 11 ) page： 1529-1533 1998

Effect of supporting electrolyte concentration on the electrochemical reaction of redox-active surfactant micelles in aqueous solutions Reviewed

Yukikazu Takeoka, Takashi Aoki, Kohei Sanui, Naoya Ogata, Masayoshi Watanabe

Journal of Electroanalytical Chemistry Vol. 438 ( 1-2 ) page： 153 - 158 1997.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier

The effect of NaCl concentration on the redox potential of α-ferrocenylundecyl-ω-hydroxy-polyoxyethylene (FPEG) micelles has been studied in aqueous solutions. With increasing NaCl concentration, the anodic half-wave potentials E1/2 of cyclic voltammograms of the aqueous solutions shift to higher potential, and the peak currents of the cyclic voltammograms decrease. The results are discussed in terms of thermodynamics of the micelle formation. An equation which interprets the correlation between the E1/2, the salt concentration, diffusion coefficient of the micelle DM, and the aggregation number m, has been derived. The changes in DM and m with NaCl concentration do not explain the change in the value of E1/2. The decrease in the equilibrium constant for the micelle-disruption Kd with increasing NaCl concentration affects the redox-potential of the FPEG micellar solutions. © 1997 Elsevier Science S.A.

DOI： 10.1016/S0022-0728(97)00128-9

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Papers - TAKEOKA, Yukikazu