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RISS 인기검색어
- 검색키워드
- 저자 : Fumio Hamada (검색결과 3 건)
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The rate-determining step in the dark state recovery process in the photocycle of PYP
Sasaki, Jun,Kumauchi, Masato,Hamada, Norio,Tokunaga, Fumio Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
The last step in the photocycle of photoactive yellow protein (PYP) is a spontaneous recovery of the dark state from the active state in which the p-coumaric acid chromophore is thermally isomerized, concomitantly with the deprotona- tion of the chtomophore and the refolding of the protein moicty. For the purpose of understanding the mechanism of the thermal back-isomerization, we have investigated the rate-determining step by analyzing mutant PYPs of Met100, which was previously shown to play a major role in facilitating the reaction (1). The mutation to Lys, Leu, Ala, or Glu decelerated the dark state recovery by 1 to 3 three orders of magnitude. By evaluating temperature-dependence and pH-dependence of the kinetics of the dark state recovery, it was found that the retardation by mutations resulted from elevation of the activation enthalpy ( H$\^$┿/) and that the pKa of the chromophore, which was affected by the mutation, is in a linier correlation with the amplitude of the rate constants. It was, therefore, deduced from the correlation that the free energy for crossing the activated state in the dark recovery process is proportional to the free energy for the deprotonation of the chromophore, identifying the rate-determining step as the deprotonation of the chromophore. (1) Devanathan, S. Genick, U. K. Canestrelli, I. L. Meyer, T. E. Cusanovich, M. A. Getzoff, E. D. Tollin, G., Biochemistry 1998, 37, 11563 - 11568
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The Role of Vibrational Coherency in Ultrafast Reaction Dynamics of PYP
Chosrowjan, Haik,Mataga, Noboru,Taniguchi, Seiji,Shibata, Yutaka,Hamada, Norio,Tokunaga, Fumio,Imamoto, Yasushi,Kataoka, Mikio Korean Society of Photoscience 2002 Journal of Photosciences Vol.9 No.2
Coherent oscillations in is fluorescence dynamics of W.-t. PYP and its site-directed mutants have been observed. Two oscillatory modes coupled with the ultrafast fluorescence due to the twisting of the excited chromophore were identified, a high ftequency mode (∼135 cm$\^$-1/) with ∼550 is damping time and a low frequency overdamped mode (-45 cm$\^$-1/) with ∼250 is damping time, respectively. Both modes disappear in the fluorescence dynamics of denatured PYP emphasizing the important role of the protein nanospace as the environment for photoreaction. The qualitative picture of fluorescence dynamics in site-directed mutants was rather similar to that in W.-t. PYP, i.e., similar oscillatory modes (∼130-140 cm$\^$-1/ and ∼40-70 cm$\^$-1/) have been observed. This indicates that the vibrational modes and electron-vibration couplings do not change dramatically due to the mutation though the damping time of low frequency mode a little decreases as the protein nanospace structure becomes looser and more disordered by mutation. On the other hand, in the case of some PYP analogues, the qualitative picture of fluorescence dynamics changes, showing the familiar picture of solvation effect whereas the oscillations are almost damped. Comparative analyses of these observations are presented.
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Muniyappan Rajiv Gandhi,Manabu Yamada,Yoshihiko Kondo,Atsushi Shibayama,Fumio Hamada 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-
p-Sulfonatothiacalix[6]arene was impregnated onto commercial polymeric resins. The platinum groupmetals sorption experiments were carried and maximum PGM sorption was observed at pH 4 in 180 min. The 1-loaded IRA-400, IRA-411, and XAD-7 showed Pd SCs of 279, 265, and 135 mg/g, respectively. ThePGM SCs of 1-loaded IRA-400, IRA-411 are found to be Pd > Pt > Rh. All the impregnated resins followedFreundlich isotherm and Pd sorption was exothermic. The kinetic studies demonstrate that Pd sorptionfollows pseudo-second order and intraparticle diffusion models. 1-Loaded XAD-7 selectively adsorbs ofPd ions from an automotive catalyst residue leached solution.
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