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Buffered mixtures of the detergent 3-(cholamidopropyl)dimethylammonio-2-hydroxy-1-propanesulfonate (CHAPSO) and dimyristoylphosphatidylcholine (DMPC) orient in the presence of a strong magnetic field over a wide range of water contents (at least 65–85%) and CHAPSO:DMPC molar ratios (typically 1:10–1:3). 31P NMR studies show that the phospholipid in such mixtures is oriented with its director axis perpendicular to the magnetic field. 31P and 2H NMR results also suggest that the structure and dynamics of the DMPC molecules are similar to that of pure phospholipids existing in the liquid crystalline (L alpha) bilayer phase. The ability of 1:5 CHAPSO:DMPC samples to orient is highly tolerant of large changes in temperature, pH, and ionic strength, as well as to the addition of substantial amounts of charged amphiphiles or soluble protein. However, 2H NMR studies of deuterated beta-dodecyl melibiose …