J. Fitter et al., MOLECULAR MOTIONS AND HYDRATION OF PURPLE MEMBRANES AND DISK MEMBRANES STUDIED BY NEUTRON-SCATTERING, European biophysics journal, 27(6), 1998, pp. 638-645
Fast stochastic equilibrium fluctuations (time scale: 10(-10)-10(-13)
seconds) In purple membranes (PM) and in disk membranes (DM) have been
measured with quasielastic incoherent neutron scattering. The compari
son of predominantly stochastic motions occurring in purple membranes
and in disk membranes revealed qualitatively similar dynamical behavio
ur. Models of internal motions within restricted volumes have been sho
wn to be useful to fit the spectra from both samples. From fits using
these models we found ''amplitudes'' 15 to 20% larger for motions in D
M samples compared to PM samples. This indicates a higher internal fle
xibility of the DM. Because the dynamical behaviour is very sensitive
to the hydration of the protein-lipid complex, we also performed neutr
on diffraction experiments to determine lamellar spacings as a measure
of level of hydration and as a function of temperature. From these st
udies the interaction of solvent molecules with the surface of the pro
tein-lipid complex appears to be qualitatively similar for both types
of membranes.