Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Volume 43, Issue 4
Displaying 1-5 of 5 articles from this issue
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Review
  • Thermodynamic Studies on Protein Structural Dynamics and Its Correlation with Function
    Satomi Inaba, Masayuki Oda
    2016 Volume 43 Issue 4 Pages 126-130
    Published: October 25, 2016
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.43.4_126
    JOURNAL FREE ACCESS
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    Protein structural dynamics in solution closely correlate with its function. Although a great number of protein structures have been determined at atomic resolution, most of them are static or averaged structures and information is lacking on their structural dynamics. We have studied the thermodynamic properties of a DNA-binding protein, c-Myb R2R3, and their correlation with protein structure-function relationships using biophysical methods. The analysis of pH-dependent conformational stability showed that the α-helical content correlated with the enthalpy change. Under physiological pH conditions, c-Myb R2R3 exists in an enthalpically unstable but entropically stable state. The temperature-dependent NMR measurements showed that some signals were broadened with an increase in temperature even below 37ºC, indicating that extensive conformational fluctuations within the folded manifold are activated at a physiological temperature. We also analyzed the effects on the stability and function of different conformational states induced by the mutations. The thermodynamic analysis using DSC and ITC showed that the increased conformational fluctuation in the native state of protein results in a decreased entropy change for either unfolding or DNA-binding. The effects of the increased fluctuation could be detected not only by the binding but also by the folding thermodynamics, both of which well correlated.
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  • Chemical Modification and Conformation of Schizophyllan, a Triple-Helical Polysaccharide
    Kazuto Yoshiba, Takahiro Sato
    2016 Volume 43 Issue 4 Pages 131-136
    Published: October 25, 2016
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.43.4_131
    JOURNAL FREE ACCESS
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    The chemical modification is important to improve the solubility to various solvents, physical properties, and immunological functions in polysaccharide chemistry. Oxidation is one of the familiar methods in the chemical modification of polysaccharides not only for industrial applications but also in fundamental studies, such as the structural determination, the first step of the functionalization, and so on. We focus a triple helical polysaccharide, schizophyllan, to study the effects of the carboxylation on the ordered structure of the polysaccharide. The oxidation of schizophyllan side chains is performed by two-step oxidation using periodate and chlorite in aqueous solutions to obtain the carboxylated sample, showing the polyelectrolyte character. The carboxylation of schizophyllan affects the triple helical conformation and the order-disorder transition with respect to the schizophyllan side chain in aqueous solutions, and solution properties governed by the conformation of this polysaccharide. The triple helical conformation was investigated mainly using the size-exclusion chromatography with a multi-angle light scattering detector, and the order-disorder transition with respect to the schizophyllan side chain was studied by differential scanning calorimetry and optical rotation.
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  • Thermal Conductivity of a Thin Film Based on Bismuth Telluride
    Koji Miyazaki
    2016 Volume 43 Issue 4 Pages 137-141
    Published: October 25, 2016
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.43.4_137
    JOURNAL FREE ACCESS
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    Thermal conductivities of bismuth telluride thin films were measured by using 3ω method. The measured thermal conductivities depend on the grain size of the film controlled by post annealing. Spectral phonon model is considered to evaluate the thermal conductivities of nanocrystalline bismuth telluride thin films. The decreasing thermal conductivity with decreasing grain size was roughly explained although the spectral model includes some assumptions for simplicity. The phonon mean free path calculated by the spectral phonon model is relatively long, and much longer than the mean free path of electron. Bismuth telluride porous thin films were fabricated to cut the ballistic phonon transport with long mean free path as well as keeping diffusive electron with short mean free path. The measured thermal conductivity of porous thin film was extremely low, and the non-dimensional figure of merit was enhanced by sub-micron structures.
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Applied Research of Thermal Analysis
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