36 Use of Nuclear Magnetic Resonance Techniques to Study Nonionic Surfactant Micelles and Mixed Micelles with
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Phospholipids EDWARD A. DENNIS and ANTHONY A. RIBEIRO Department of Chemistry, University of California at San Diego, La Jolla, Calif. 92093
Nonionic surfactants of the p,tert-octylphenylpolyoxyethylene ether (OPE) class are widely used as detergents, solubilizers,
and emulsifiers. Triton X-100 (Triton), a commercial product which has an average value of n = 9 to 10, forms micelles in aqueous solution and under certain conditions forms mixed micelles with phospholipids such as 1,2-diacyl-sn-glycero-3-phosphorylcholine (phosphatidylcholine). These mixed micelles are of great current interest in biochemical studies as they are formed when Triton is used in the purification of membrane-bound proteins (1) and also serve as an excellent form for the phospholipid substrate (2) of various lipolytic enzymes such as phospholipase A2 (3) and the membrane-bound enzyme phosphatidylserine decarboxylase (4). 1 13 Over the last few years, we have employed both H and C nuclear magnetic resonance (nmr) techniques to study the structural aspects of OPE micelles, and particularly those of Triton X-100 (5-8). Furthermore, we developed a 1H-nmr technique to follow the formation of mixed micelles with Triton and to determine phase diagrams for the surfactant-phospholipid-water system (9,10). We have also utilized both 1H- and 13C-nmr relaxation techniques to gain information about the structure and mobility of the surfactant and phospholipid in the mixed micelles (6,7, 11). Nmr has been one of the major physical techniques utilized to characterize the physical state of phospholipid in multibilayer (smectic mesophase) and single bilayer (sonicated vesicle)
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Resing and Wade; Magnetic Resonance in Colloid and Interface Science ACS Symposium Series; American Chemical Society: Washington, DC, 1976.
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