title: Anharmonic behavior in the multisubunit protein apoferritin as revealed by quasi-elastic neutron scattering.
abstract: 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), sigma = 5.0 kJ x mol (-1)). Our results are likened to those reported for other proteins.
authors.affiliation: ISIS Facility, Science and Technology Facilities Council (STFC), Rutherford Appleton Laboratory, Chilton, OX11 OQX, UK. M.Telling@rl.ac.uk
authors.forename: Mark T F
authors.initials: MT
authors.lastname: Telling
authors.forename: Cameron
authors.initials: C
authors.lastname: Neylon
authors.forename: Susan H
authors.initials: SH
authors.lastname: Kilcoyne
authors.forename: Valeria
authors.initials: V
authors.lastname: Arrighi
mesh_terms: D001052:Apoferritins / Q000737:chemistry*; D004548:Elasticity; D009068:Movement; D033363:Neutron Diffraction; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D001052:Apoferritins