Bacteriorhodopsin and rhodopsin studied by incoherent neutron scattering: dynamical properties of ground states and light activated intermediates

Quasielastic incoherent neutron scattering as a tool to study picosecond eq uilibrium fluctuations was used to investigate the dynamical properties of two retinal proteins, rhodopsin and bacteriorhodopsin. Upon absorption of a photon by the retinal chromophore both proteins undergo a sequence of diff erent intermediate states. As known from numerous studies the intermediate states (Metarhodopsin II and M-2, respectively) differ from the ground stat e with respect to the protein structure. Therefore, this work was focussed on the relationship between the light-induced structural changes and possib le alterations of much faster picosecond fluctuations of the protein struct ure. In a time range from a few picoseconds to a few femtoseconds no change s of the fast internal motions have been observed between the ground states and the corresponding intermediate states. (C) 1999 Elsevier Science B.V. All rights reserved.