IQNS-monitored dynamical transition of a small beta-protein following heatdenaturation

Quasi-elastic neutron scattering experiments performed on neocarzinostatin, a small beta-protein, reveal a drastic change in the fast (picosecond time scale) diffusive internal dynamics when the protein unfolds by heating. Da ta treatment is based on a model that separates contributions arising from global and internal motions. Most of internal dynamic parameters (amplitude of diffusive motions, fraction of "immobile" scatters, mean-square vibrati onal amplitude) undergo abrupt modifications when the temperature is raised above 65 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.