Mezei, F ; Russina, M. ; Chen, G. ; Frauenfelder, H. ; Fenimore, P.W. ; Falus, P. ; Farago, B.: Dynamic transition and glassy behaviour in hydrated proteins. Journal of Physics: Conference Series 177 (2009), p. 012011/1-2
10.1088/1742-6596/177/1/012011
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 variation of the mean square displacement of the hydrogen atoms <u2>. The marked kink in the temperature dependence of this quantity around 200 K has been originally observed by Mössbauer spectroscopy and by “elastic window” neutron backscattering spectroscopy and is. This behaviour is referred to as “dynamic transition”, although it is clear that it is a gradual change as opposed to a sharp feature in the temperature dependence. Its origin remained controversial over the past decades. We have extended its exploration 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. This was achieved by the combination of high precision time-of-flight neutron spectroscopy (TOF) and neutron spin echo (NSE) experiments in both H2O and D2O hydrated myoglobin. Around the temperature of the dynamic transition we have observed the onset of a relaxation process spread over several orders of magnitude in time, which reveals all neutron scattering signature properties of the canonical ß relaxation process in the vicinity conventional glass transitions