PMR relaxation times of micelles of the nonionic surfactant triton X-100 and mixed micelles with phospholipids

Abstract

Previous pmr studies at 220 MHz have led to the suggestion that phosphatidylcholine and the nonionic surfactant Triton X-100 form mixed micellar structures at high molar ratios of Triton to phospholipid. These mixed micelles provide one form of the phospholipid which the enzyme phospholipase A 2 can utilize as substrate. Spin-lattice relaxation times (T 1) and spin-spin relaxation times (T 2) obtained from line widths for resolvable protons in Triton X-100 micelles and mixed micelles with egg phosphatidylcholine and dipalmitoyl phosphatidylcholine are reported. They suggest that the structure of the mixed micelles is generally similar to that of pure Triton X-100 micelles. The T 1 values for the phospholipid in the mixed micelles are found to be similar to those reported for phospholipid in sonicated vesicle preparations which are used as membrane models, but the lines are somewhat sharper suggesting the possibility of less anisotropic motion in the mixed micelles than in the vesicles.