Netsu Sokutei

Effect of Hydration on the Thermal Stability of the Collagen Triple Helical Structure

Yoshinori Nishi, Susumu Uchiyama, Yuji Kobayashi

2007 Volume 34 Issue 4 Pages 152-158
Published: August 31, 2007
Released on J-STAGE: September 07, 2009

DOIhttps://doi.org/10.11311/jscta1974.34.152

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4(R)-Hydroxyproline (Hyp^R) is often found in natural collagen in spite of being a rare amino acid in proteins overall. It has been known that Hyp^R residue contributes to the thermal stability of the collagen triple helical structure. Intensive studies to investigate the stabilizing mechanism of the collagen triple helical structure have been performed by using a series of polytripeptides (X-Y-Gly)₁₀ [X, Y: Pro, Hyp^R, or 4-fluoroproline (fPro)], The thermodynamic parameters determined by DSC analyses of these model peptides indicate that the enthalpy term contributes predominantly to the thermal stability of (Pro-Hyp^R-Gly)₁₀, whereas the entropy term is primarily responsible for the enhanced stabilities of (Pro-fPro^R-Gly)₁₀ and (fPro^S-Pro-Gly)₁₀. Based on the comparison of molecular volumes observed in solution with intrinsic ones from the crystal structure, the difference comes from the difference of hydration on these peptides.

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Structure and Phase Transitions of Intercellular Lipid Assembly in Stratum Corneum

Ichiro Hatta, Kana Nakanishi, Noboru Ohta

2007 Volume 34 Issue 4 Pages 159-166
Published: August 31, 2007
Released on J-STAGE: September 07, 2009

DOIhttps://doi.org/10.11311/jscta1974.34.159

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Stratum corneum which is composed of corneocytes and intercellular lipid matrix plays an important role in barrier function and maintenance of water in skin. The intercellular lipid matrix bears the main part in the function. Therefore, it is important to make clear the structure formed by the intercellular lipids. It is well-known from X-ray diffraction, electron diffraction, neutron scattering, etc. that the structure consists of long and short lamellar structures and in the orthogonal direction hexagonal and orthorhombic hydrocarbon-chain packings. However, until now the relation between each lamellar structure and each hydrocarbon-chain packing has been unresolved. From the thermal analysis and the temperature scanning small- and wide-angle X-ray diffraction analysis in stratum corneum, we revealed that there are two domains: One is the long lamellar structure with the hexagonal hydrocarbon-chain packing and the other the short lamellar structure with the orthorhombic hydrocarbon-chain packing. Based upon the structural evidence we can further study the functional mechanism of cosmetics, the drug penetration mechanism, etc.

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Construction of Phase Diagrams by Differential Thermal Analysis for IIaIII₂VI₄ Phosphors and their Crystal Growth

Chiharu Hidaka, Hiroaki Matsushita, Takeo Takizawa

2007 Volume 34 Issue 4 Pages 167-174
Published: August 31, 2007
Released on J-STAGE: September 07, 2009

DOIhttps://doi.org/10.11311/jscta1974.34.167

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Differential thermal analysis (DTA) has been performed in order to grow or synthesize the alkaline earth thiogallate compounds that are currently known as useful and attractive phosphors. A big exothermic heat generated at the chemical reaction during synthesis and the pressure hereby produced sometimes prevents the compounds from being synthesized. The DTA measurements give us information to diminish the heat of reaction and hence the pressure due to sulfur. The phase diagrams of the pseudo-binary system for the compounds above have also been constructed from the results of DTA and powder X-ray diffraction. Based on these diagrams, alkaline earth thiogallates and their kindred can be grown form melts. Some compounds are abruptly solidified with supercooling, resulting in fragile polycrystals. Improvement of the shape of a crucible helps a crystalline seed to grow, leading to a single crystal with good quality.

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Phase Transition and Relaxor Behavior of Lead Free Perovskite Oxides BaTi_1-xZr_xO₃

Motoi Nagasawa, Hitoshi Kawaji, Takeo Tojo, Tooru Atake

2007 Volume 34 Issue 4 Pages 175-181
Published: August 31, 2007
Released on J-STAGE: September 07, 2009

DOIhttps://doi.org/10.11311/jscta1974.34.175

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The heat capacity and dielectric constant were measured from liquid helium temperature to 420K on BaTi_1-xZr_xO₃ synthesized by a conventional solid state reaction method for x=0∼0.90. In the samples of x≤0.3, typical ferroelectric phase transition was observed in the heat capacity and dielectric constant. The heat capacity anomaly became smaller with increasing x, and disappeared for the samples of x≥0.35, where relaxor-like behavior was observed in the dielectric constant. This result indicates that the mechanism of the relaxor behavior in BaTi_1-xZr_xO₃ systems is different from that of PMN, in which the order-disorder type phase transition may be frozen in a glassy state at low temperatures. The relaxor behavior of BaTi_1-xZr_xO₃ systems may be attributed to the freezing of displacive-type phase transition.

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[title in Japanese]

2007 Volume 34 Issue 4 Pages 182-184
Published: August 31, 2007
Released on J-STAGE: September 07, 2009

DOIhttps://doi.org/10.11311/jscta1974.34.182

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