ONE-DIMENSIONAL AND 2-DIMENSIONAL H-1-NMR STUDIES OF PRESSURE AND TETRACAINE EFFECTS ON SONICATED PHOSPHOLIPID-VESICLES

One and two dimensional H-1-NMR experiments have been performed to stu dy the molecular order and dynamics of 1,2-dipalmitoyl-sn-glycero-3-ph osphocholine (DPPC) unilamellar vesicles under the influence of high p ressure and the local anesthetic, tetracaine (TTC), which can also be considered as a model-charged amphiphile. The TTC molecules have an or dering effect on the headgroups but a disordering effect on the acyl c hains, whereas, pressure has an ordering effect on the acyl chains. Th e results from 2D NOESY experiments on pure DPPC vesicles show that th e intensities of NMe(3)/CH3, NMe(3)/(CH2)(n) and CH3/(CH2)(n) cross-pe aks increase with increasing pressure in the liquid-crystalline phase but decrease with pressure in the gel phase, further suggesting that t he appearance of the cross-peaks between the two extremes of the DPPC molecules is due to spin-diffusion. For the DPPC/TTC vesicles, the 2D NOESY experiments confirm that charged TTC molecules are located in th e headgroup region of the DPPC bilayers and, in the gel phase, also su ggest the formation of an interdigitated gel phase.