Raman spectroscopy of acetylcholine receptor-rich membranes from Torpedo marmorata and of their isolated components

Abstract

not received Acetylcholine receptor Lipid-protein interaction Raman spectroscopy is a particularly powerful technique to explore the three-dimensional organisation of biological molecules. With proteins, this method lead to the detection of differences in conformation affecting both the backbone and the amino acid side chains [l]. In particular, the analysis of the conformationally sensitive Amide I and Amide III regions of the spectra offered new insights and predictions on the secondary folding of the polypeptide chain. Also, the vibrations of the amino acid side chains, in particular those of the aromatic amino acids tyrosine and tryptophan, brought original information on the state of these residues in proteins [2,3]. With simple lipids and model membrane systems the Raman active (C-H) and (C-C) stretching modes have been used to monitor lateral mobility and trans-gauche isomerism [4,5]. Various lipid-protein complexes have also been the object of intense Raman studies [6-81 and the analysis extended to biological membranes from human and rabbit erythrocyte ghosts [9, lo], thymocytes [ 111, sarcoplasmic reticulum [ 121, hamster lymphocytes [13] and human blood platelets [14]. Abbreviations: AcCh, acetylcholine; AcChR, acetylcholine receptor; DDAO, dimethyldodecylamine oxide Published by Elsevier Science Publishers B. V. Within the framework of the vibrational spectroscopic studies on the conformation of acetylcholine (AcCh) and related compounds (rv 50 mM Tris-HCl (pH 7.5), 3 mM EDTA, 1 mM EGTA, 0.1 mM PMSF, 5 units/ml aprotinin, 5 pg/ml pepstatin; see [ 181). The mem00145793/83/$3.00