Deuteron and sodium—23 NMR studies of lecithin mesophases

The deuteron quadrupole splitting of lamellar mesophase samples containing lecithin and heavy water depends strongly on sample composition and temperature. Broadening effects due to cholesterol may arise from deuteron exchange between water and cholesterol. In samples composed of lecithin, cholesterol, alkali chloride and heavy water, or of lecithin, alkali cholate and heavy water, the degree of water orientation is lower with K + ions than with the other alkali ions. 23Na NMR experiments show K + ions to interact more strongly with the amphiphilic molecules than other alkali ions. A decrease in 23Na line width on cholesterol addition is ascribed to a partial release of sodium ions from the lamellae. The 23Na quadrupole splitting increases with increasing cholesterol content and this may be due to a reduced motional freedom of the polar end of the lecithin molecule.