High-pressure1H NMR on model biomembranes: a study of the local anaesthetic tetracaine incorporated into POPC lipid bilayers

Abstract

One- and two-dimensional 1H NMR experiments were performed at ambient and elevated pressures to study structural and conformational properties of the local anaesthetic tetracaine (TTC) incorporated into 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) lipid bilayers, and also the lipid– tetracaine interaction. For this purpose, a 400 MHz high-pressure, high-resolution NMR probe was developed, operating in the pressure range 1– 3000 bar at temperatures up to 80 °C. We obtained a linewidth better than 2.5 Hz for a 5 mm sample of 10% CHCl3 in CDCl3 in the high-pressure environment. The results from two-dimensional 1H,1H NOESY experiments show that the charged form of TTC is not expelled from unilamellar POPC vesicles at pressures up to about 2 kbar. Intramolecular cross peaks indicate that TTC is incorporated in a bent conformation, located in the headgroup region at ambient pressure, but embedded deeper in the membrane interior at higher pressures. Copyright © 2000 John Wiley & Sons, Ltd.