One- and two-dimensional NMR relaxation studies of dynamics and structure in bile salt-phosphatidylcholine mixed micelles.

A series of one- and two-dimensional 1H-NMR relaxation measurements has been conducted on simple and mixed micellar aggregates of taurocholate, diphenylvaleroylphosphatidylcholine (diPVPC) and egg yolk phosphatidylcholine (egg PC). The results are interpreted to provide structural and dynamic comparisons between micelles and vesicles, between phospholipids of varying chain length, and between different lipid components within the same micellar aggregate. Both chemical shift changes and two-dimensional nuclear Overhauser effect cross peaks suggest direct interaction of taurocholate and PC chemical sites, although the latter observations may also be accounted for by PC-PC interactions. These experiments demonstrate the promise of NMR relaxation techniques for investigations of molecular organization in model substrate for lipolytic enzymes.