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Volume 43 (2016)
- Issue 4 Pages 126-
- Issue 3 Pages 91-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 43, Issue 2
Displaying 1-5 of 5 articles from this issue
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Review
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Eiji Ohmae, Yurina Miyashita, Chiaki Kato2016 Volume 43 Issue 2 Pages 59-65
Published: April 25, 2016
Released on J-STAGE: November 20, 2022
JOURNAL FREE ACCESSTo elucidate the molecular adaptation mechanisms of enzymes to the high hydrostatic pressure of deep sea, we compared the structure, stability, and function of dihydrofolate reductase (DHFR) from a deep-sea bacterium, Moritella profunda (mpDHFR), with those from Escherichia coli (ecDHFR). The backbone structure of mpDHFR almost overlapped with that of ecDHFR. However, the structural stability of both DHFRs was quite different: mpDHFR was more thermally stable than ecDHFR but less stable against urea and pressure unfolding. The smaller volume changes due to unfolding suggest that the native structure of mpDHFR involves a smaller amount of cavity and/or an enhanced hydration compared to ecDHFR. The enzymatic activity of the wild-type ecDHFR decreased under high pressure, but mpDHFR showed the maximum activity around 50 MPa, and the D27E mutant of ecDHFR exhibited pressureactivation. The inverted activation volumes of these DHFRs suggest the changes in the cavity and hydration of the transition-state in the rate-determining step of the enzymatic reaction. Since the cavity and hydration depend on the amino acid side chains, DHFR could adapt to the deep-sea environment without altering their backbone structure. The results indicate the importance of cavity and hydration on the molecular adaptation of proteins to the deep-sea environments.View full abstractDownload PDF (958K) -
Kunisato Kuroi, Masahide Terazima2016 Volume 43 Issue 2 Pages 66-71
Published: April 25, 2016
Released on J-STAGE: November 20, 2022
JOURNAL FREE ACCESSThermodynamic parameters are fundamental quantities to characterize chemical reactions. For a long time, these parameters have been measured only under equilibrium conditions. However, our group has developed a novel time-resolved detection method of the thermodynamic parameters using the pulsed laser induced transient grating (TG) technique. This technique has been applied to various photoreceptor proteins and succeeded in determining thermodynamic parameters of transient intermediates during protein reactions, such as enthalpy change, volume change, heat capacity change, and thermal expansion coefficient change. Recently we have developed an instrument to introduce the pressure to this powerful method and expanded its capability toward the time-resolved detection of the ‘isothermal compressibility (βT)’, which directly reflects the structural fluctuation and hence is important in the protein science. The fluctuation of a protein is considered to play an important role for its function and attracts much attention. Hence, βT of reaction intermediates can offer the direct knowledge how the fluctuation is involved in protein reactions. In this article, we briefly review the pressure variable TG method including its principle, a specially designed optical high-pressure cell, and our recent results on the first detection of βT for intermediates of the protein reaction.View full abstractDownload PDF (1313K) -
Yoshiharu Suzuki2016 Volume 43 Issue 2 Pages 72-79
Published: April 25, 2016
Released on J-STAGE: November 20, 2022
JOURNAL FREE ACCESSFrom a viewpoint of water polyamorphism, we examined the states of solvent water in the glassy dilute LiCl-water solutions and in the glassy dilute glycerol-water solutions and studied the effects of the solute on the polyamorphic behaviors of the solvent water. The states of the glassy solvent water are able to be characterized by the states of low- and high-density amorphous ices, LDA and HDA, respectively. The polyamorphic transition of aqueous solution depends on the solute concentration and the solute component. There exists a region in which LDA-like solvent water and HDA-like solvent water coexist in the pressure-temperature-concentration diagram of aqueous solution. The extent of the coexistence region seems to relate to the difference between the solubility of solute in the two kinds of solvent water. The behaviors of glassy aqueous solution are consistent with the water polyamorphism. This result provides insight not only into the relation between the hydration and the two kinds of water but also into the dynamics of macromolecules surrounded by water.View full abstractDownload PDF (1858K) -
Takashi Odagaki2016 Volume 43 Issue 2 Pages 80-84
Published: April 25, 2016
Released on J-STAGE: November 20, 2022
JOURNAL FREE ACCESSI present the free energy landscape (FEL) approach to glass transition which provides a unified understanding of glass transition singularities. For quasi-equilibrium systems, thermodynamic quantities can properly be defined with the use of the probability function of each basin of the FEL. I argue that the specific heat of glassy systems consists of three contributions; the glass specific heat, the configurational specific heat and a term related to the temperature dependence of the probability distribution. The FEL frame work is generalized to handle time-dependent phenomena, where time-dependent quantities such as cooling rate dependence can be investigated. I also discuss the temperature modulation spectroscopy on the basis of the FEL theory. Finally, I emphasize the most attractive merit of the FEL theory, namely it can handle thermodynamic and dynamic effects such as the temperature dependence of the crystallization time in a single theoretical frame work.View full abstractDownload PDF (1050K)
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2016 Volume 43 Issue 2 Pages 85-87
Published: April 25, 2016
Released on J-STAGE: November 20, 2022
JOURNAL FREE ACCESSDownload PDF (655K)
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