Temperature-dependent Dynamics of Dry and Hydrated β-Casein Studied by Quasielastic Neutron Scattering

Published

August 21, 2014

Author(s)

Gurpreet K. Dhindsa, Madhu Sudan Tyagi, Xiang-Qiang Chu

Abstract

β-Casein is a component of Casein micelle with amphillic nature and is recognized as a ¿natively disordered¿ protein which lacks secondary structures. In this study, the temperature and hydration effects on the dynamics of β-Casein are explored by Quasielastic Neutron Scattering (QENS). An upturn in the mean square displacement (MSD) of hydrated β-Casein indicates an increase of protein flexibility at temperature 225 K. Another increase in MSD at 100 K observed in both dry and hydrated β-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 (β-relaxation time) in the dynamics of hydrated β-Casein. This dynamical behavior has been observed in hydrated globular and oligomeric proteins and is considered as a universal behavior for protein dynamics. Our temperature dependent QENS experiments provide evidence that lack of secondary structure in β-Casein results in higher flexibility in its dynamics and easier reversible thermal unfolding compared to other rigid biomolecules.

Citation

Journal of Physical Chemistry B

Volume

8

Pub Type

Journals

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Keywords

protein, neutron scattering, dynamics

Citation

Dhindsa, G. , Tyagi, M. and Chu, X. (2014), Temperature-dependent Dynamics of Dry and Hydrated β-Casein Studied by Quasielastic Neutron Scattering, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=916225 (Accessed May 17, 2024)