Open AccessImmobilized lipid in acetylcholine receptor-rich membranes from Torpedo marmorata.
Author(s) -
Derek Marsh,
Francisco J. Barrantes
Publication year - 1978
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.75.9.4329
Subject(s) - membrane , spin label , chemistry , torpedo , spin probe , electron paramagnetic resonance , lipid bilayer , biophysics , acetylcholine receptor , quenching (fluorescence) , bilayer , acetylcholine , crystallography , analytical chemistry (journal) , biochemistry , nuclear magnetic resonance , receptor , fluorescence , chromatography , biology , physics , quantum mechanics , endocrinology
The lipid environment of acetylcholine receptor-rich membranes from Torpedo marmorata has been studied with spin labels. The electron spin resonance spectra of both stearic acid and steroid probes in the membranes revealed an immobilized lipid component, in addition to the fluid component which is found in aqueous bilayer dispersions of the extracted lipids. The spin labels also cause a differential paramagnetic quenching of the intrinsic protein fluorescence of the membranes, which is sensitive to the action of cholinergic ligands and follows a modified Stern-Volmer law. Electron spin resonance difference spectroscopy shows that the protein-associated lipid is immobilized with respect to rotation both around and perpendicular to the long molecular axis, with correlation times : formula: (see text) approximately 50-70 ns. The proportion of lipid in the immobilized component is greater than calculated for a single boundary layer around the protein and corresponds more closely to the total interstitial lipid occupying the area between densely packed protein units in acetylcholine receptor-rich membranes.