Interaction of cholesterol with various glycerophospholipids and sphingomyelin

• Published in: Biochemistry (Easton) 1990-11, Vol.29 (47), p.10670-10675
• Main Authors: Sankaram, Mantripragada B, Thompson, Thomas E
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; cholesterol; Cholesterol - metabolism; Cholesterol - physiology; Electron Spin Resonance Spectroscopy; Fundamental and applied biological sciences. Psychology; glycerophospholipids; Interactions. Associations; Intermolecular phenomena; Membrane Fluidity - physiology; Molecular biophysics; Phosphatidic Acids - metabolism; Phosphatidylcholines - metabolism; sphingomyelin; Sphingomyelins - metabolism; Spin Labels
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00499a014

The influence of cholesterol on the phase behavior of glycerophospholipids and sphingomyelins was investigated by spin-label electron spin resonance (ESR) spectroscopy. 4-(4,4-Dimethyl-3-oxy-2-tridecyl-2-oxazolidinyl)butanoic acid (5-SASL) and 1-stearoyl-2-[4-(4,4-dimethyl-3-oxy-2-tridecyl-2-oxazolidinyl)butanoy l]-sn- glycero-3-phosphocholine (5-PCSL) spin-labels were employed for this purpose. The outer hyperfine splitting constants, Amax, measured from the spin-label ESR spectra as a function of temperature were taken as empirical indicators of cholesterol-induced changes in the acyl chain motions in the fluid state. The Amax values of 5-PCSL exhibit a triphasic dependence on the concentration of cholesterol for phosphatidylcholines and bovine brain sphingomyelin. We interpret this dependence as reflecting the existence of liquid-disordered, ld, liquid-ordered, lo, and coexistence regions, ld + lo. The phase boundary between the ld and the two-phase region and the boundary between the lo and the two-phase region in the phosphatidylcholine-cholesterol systems coalesce at temperatures 25-33 degrees C above the main-chain melting transition temperature of the cholesterol-free phosphatidylcholine bilayers. In the case of bovine brain sphingomyelin, the ld-lo phase coalescence occurs about 47 degrees C above the melting temperature of the pure sphingomyelin. The selectivity of interaction of cholesterol with glycerophospholipids of varying headgroup charge was studied by comparing the cholesterol-induced changes in the Amax values of derivatives of phosphatidylcholine, phosphatidic acid, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylserine spin-labeled at the fifth position of the sn-2 chain.