Telling, M, Neylon, C, Arrighi, V and Kilcoyne, SH 2008, 'An-harmonic behaviour in the multi-subunit protein apoferritin as revealed by quasi-elastic neutron scattering' , Journal of Physical Chemistry B, 112 (35) , pp. 10873-10878.

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Abstract

Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behaviour in lyophilized and hydrated apoferritin; a naturally occurring, multisubunit protein. While analysis of the measured mean squared displacement (msd) parameter reveals a hydration-dependent inflection above 240 K, characteristic of diffusive motion, a hydration-independent inflection is observed at 100 K. The mechanism responsible for this low temperature an-harmonic response is further investigated, via analysis of the elastic incoherent neutron scattering intensity, by applying models developed to describe side group motion in glassy polymers. Our results suggest that the deviation from harmonic behaviour is due of the onset of methyl group rotations which exhibit a broad distribution of activated processes (Ea,ave =12.2 kJ.mol-1, � = 5.0 kJ.mol�1). Our results are likened to those reported for other proteins.

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