Interactions between xenon and phospholipid bicelles studied by 2H/129Xe/131Xe NMR and optical pumping of nuclear spins

The interactions between xenon and DMPC/DHPC bicelles (q = 3.5%, 7.5% w/v) were studied via 2H, 129Xe, 131Xe, and optically enhanced 129Xe NMR. The chemical shifts, linewidths, and quadrupolar couplings of the xenon/bicelle NMR signals were correlated with different regions of the bicellar phase diagram. The addition of xenon (<70 mM) was observed to reduce the temperature-onset of bicelle alignment by several degrees, in quantitative agreement with effects previously observed with chloroform; however, the stable liquid-crystalline range was not significantly reduced. Preliminary laser-polarized xenon/bicelle studies yielded 129Xe T1 values of ∼120 s, long enough to permit a variety of planned experiments.