Dynamic transition and glassy behaviour in hydrated proteins

Abstract

The temperature dependence of functional kinetics of hydrated proteins has been related to changes in dynamic behaviour on the microscopic level, as reflected by the transition like variation of the mean square displacement 〈u2〉 of the hydrogen atoms. We have extended these explorations by a detailed study of the whole quasielastic and inelastic neutron scattering spectra over the broad energy transfer domain of 50 neV to 20 meV by the combination of high precision time-of-flight neutron spectroscopy (TOF) and neutron spin echo (NSE) experiments in H2O and D2O hydrated myoglobin. This allowed us to identify the basic character of the dynamic processes behind the observed un-harmonic variation of 〈u2〉. We have found that these processes are fully compatible with the extensively studied glassy type β fluctuations, which enter with increasing temperature the 0.2 ps - 10 ns combined TOF - NSE time window of the present study. © 2009 IOP Publishing Ltd.