Anharmonic Behavior in the Multisubunit Protein Apoferritin as Revealed by Quasi-Elastic Neutron Scattering

Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behavior in lyophilized and hydrated apoferritin, a naturally occurring, multisubunit protein. Whereas analysis of the measured mean squared displacement (msd) parameter reveals a hydration-dependent...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2008-09, Vol.112 (35), p.10873-10878
Main Authors: Telling, Mark. T. F, Neylon, Cameron, Kilcoyne, Susan H, Arrighi, Valeria
Format: Article
Language:English
Subjects:
Apoferritins - chemistry
B: Macromolecules, Soft Matter
Elasticity
Movement
Neutron Diffraction
Temperature
Water - chemistry
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Summary:Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behavior in lyophilized and hydrated apoferritin, a naturally occurring, multisubunit protein. Whereas 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 anharmonic 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 behavior is due to the onset of methyl group rotations which exhibit a broad distribution of activated processes (E a,ave = 12.2 kJ·mol−1, σ = 5.0 kJ·mol−1). Our results are likened to those reported for other proteins.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp801779x