Temperature-Dependent Dynamics of Dry and Hydrated 尾-Casein Studied by Quasielastic Neutron Scattering

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• 作者：Gurpreet K Dhindsa ; Madhusudan Tyagi ; Xiang-qiang Chu
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：September 18, 2014
• 年：2014
• 卷：118
• 期：37
• 页码：10821-10829
• 全文大小：524K
• ISSN：1520-5207

文摘

尾-Casein is a component of casein micelle with amphillic nature and is recognized as a 鈥渘atively disordered鈥?protein that lacks secondary structures. In this study, the temperature and hydration effects on the dynamics of 尾-casein are explored by quasielastic neutron scattering (QENS). An upturn in the mean square displacement (MSD) of hydrated 尾-casein indicates an increase of protein flexibility at a temperature of 鈭?25 K. Another increase in MSD at 鈭?00 K, observed in both dry and hydrated 尾-casein, is ascribed to the methyl group rotations, which are not sensitive to hydration. QENS analysis in the energy domain reveals that the fraction of hydrogen atoms participating in motion in a sphere of diffusion is highly hydration dependent and increases with temperature. In the time domain analysis, a logarithmic-like decay is observed in the range of picosecond to nanosecond (尾-relaxation time) in the dynamics of hydrated 尾-casein. This dynamical behavior has been observed in hydrated globular and oligomeric proteins. Our temperature-dependent QENS experiments provide evidence that lack of a secondary structure in 尾-casein results in higher flexibility in its dynamics and easier reversible thermal unfolding compared to other rigid biomolecules.