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Small Angle Neutron Scattering Study on the Structural Variation of Lysozyme in Bioprotectants
Shota Koda,Haruki Takayama,Tomohiko Shibata,Tatsuya Mori,Seiji Kojima,In-Sung Park,Tae-Gyu Shin 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9
The thermal denaturation and subsequent structural variation of lysozyme in various bioprotectant candidate solutions such as trehalose and choline acetate have been investigated by using small angle neutron scattering and differential scanning calorimetry. The gyration radius shows little change with the addition of additives in a native state at room temperature. On heating the lysozyme solution, a remarkable increase in the gyration radius is observed at temperatures above the denaturation temperature without any bioprotectants. Such an increase is suppressed by the additives owing to the intermolecular interactions between the lysozyme molecules and the bioprotectants of trehalose and choline acetate. The fractal dimension of lysozyme varies slightly with the addition of the bioprotectant solutions, and shows a remarkable drop in the vicinity of the denaturation temperature for all the solutions.
Relaxation dynamics and fragility during liquideglass transitions of poly(propylene glycol)s
Shota Koda,Tomohiko Shibata,박인성,Seiji Kojima 한국물리학회 2015 Current Applied Physics Vol.15 No.7
The acoustic and thermal properties of the liquideglass transitions of propylene glycol and its oligomers, poly (propylene glycol)s, were studied by temperature modulated DSC and Brillouin scattering. The fragility indices were determined from Angell plots using the observed modulation frequency dependence of the complex heat capacity. The variation in the glass transition temperatures is discussed on the basis of the free volume theory. The relaxation time of the structural relaxation obeys the VogeleFulcher law, and its high frequency end is in good agreement with the result of the dielectric measurement in the literature. The correlation between the observed thermal expansion coefficients and the glass transition temperature is discussed based on the free volume theory. The sound velocity and attenuation were accurately determined as a function of the temperature by Brillouin scattering by combination with the refractive index measurement. The relaxation dynamics were discussed by considering the relaxation from segmental motions. All of these physical properties were discussed based on the third-order anharmonicity and the Grüneisen parameter.