Effects of benzyl alcohol on phosphatidylcholine lamellar phase with different water contents

Effects of benzyl alcohol (BA) on the bilayer thickness dl and the fluidity of egg phosphatidylcholine (PC) lamellar phase with various water contents have been studied by X-ray diffraction and the proton spin-lattice relaxation rate. At lower water contents, BA causes dl to decrease and the rate of molecular motions to increase. By contrast, with increasing BA at excess water, dl remains nearly unchanged, though the rate of motions increases. Hydration experiment for egg phosphatidylcholine lamellae with BA at a 1 : 1 molar ratio shows that in the range from 15% to 30% water, dl decreases to the value of the fully hydrated sample without BA and is nearly constant above 30% water. The value at full hydration is suggested to be a lower limit of the bilayer thickness, the chain is in the unperturbed state. It is in an extended structure at lower water contents. This leads to the difference in the effect of BA on the bilayer thickness at different water contents.