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Molecular motions and hydration of purple membranes and disk membranes studied by neutron scattering |
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| Authors: | J Fitter O P Ernst T Hauß R E Lechner K P Hofmann N A Dencher |
| Institution: | Forschungszentrum Jülich, IBI-2, Biologische Strukturforschung, D-52425 Jülich, Germany e-mail: j.fitter@fz-juelich.de, DE Institut für medizinische Physik und Biophysik, Medinizische Fakult?t, Humboldt-Universit?t, Charité, Ziegelstrasse 5–9, D-10098 Berlin, Germany, DE Hahn-Meitner-Institut, BENSC, Glienicker Strasse 100, D-14109 Berlin, Germany, DE Institut für Biochemie, TU Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany, DE |
| Abstract: | 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 comparison of predominantly stochastic motions occurring in purple membranes and in disk membranes revealed qualitatively similar dynamical behaviour. Models of internal motions within restricted volumes have been shown 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 DM samples compared to PM samples. This indicates a higher internal flexibility of the DM. Because the dynamical behaviour is very sensitive to the hydration of the protein-lipid complex, we also performed neutron diffraction experiments to determine lamellar spacings as a measure of level of hydration and as a function of temperature. From these studies the interaction of solvent molecules with the surface of the protein-lipid complex appears to be qualitatively similar for both types of membranes. Received: 12 February 1998 / Revised version: 18 March 1998 / Accepted: 27 March 1998 |
| Keywords: | Purple membrane Disk membrane Quasielastic incoherent neutron scattering Lamellar structure Diffusive motions |
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