Small-angle neutron scattering of aqueous dispersions of lipids and lipid mixtures. A contrast variation study

Small-angle neutron scattering data for lipid bilayers in excess water are presented. The method of solvent contrast variation was applied. The variation of scattering intensity with the scattering angle could be analyzed in terms of the model of scattering by quasi-2-dimensional systems of O. Kratky and G. Porod (1948). From this, the bilayer thickness of unilamellar vesicles of dimyristoyllecithin was detd. to be 41 .ANG. at 310 K. Several typical mixts. of different lecithins with varying chain lengths and of lecithin with phosphatidic acid were studied. By deuteration of 1 lipid component, a very large contrast between segregated phases could be achieved. It was thus possible to distinguish clearly between homogeneous mixts. and mixts. which exhibit a heterogeneous lipid organization. In the latter case, no intensity matching on solvent contrast variation was possible. Phase boundaries were detd. very accurately by performing contrast variation expts. with at most 2 mixts. of different initial compn. The main advantage of the present method was that lateral phase sepn. could also be clearly studied in fluid states of the bilayer. From the av. scattering-length ds., the d. of the lipid layers, and thus the excess vols. of the mixts. could be detd. For lecithin mixts., pos. excess vols. were obsd., whereas for the lecithin-phosphatidic acid mixt., the excess vol. was neg. [on SciFinder (R)

Structural-changes of F1ATPase detected by neutron-ray and x-ray small-angle scattering

Static structural changes of bacterial F1ATPase, a protein complex of the biological energy metabolism, have been detected. Those structural changes are related to the variation of the temperature, the dissociation of the (inhibitory) delta/gamma-subunit and the binding of the irreversible inhibitor sodium azide to the enzyme. Structural changes of the enzyme in solution were detected by neutron and x-ray small angle scattering (with synchrotron radiation)

Steady-state Spin Contrast Created by Dynamic Nuclear Polarisation

URL: http://www-spht.cea.fr/articles/S03/010Rapport PSI. Scientific Report p. 191 (march 2003)