Vesicle membrane-water partition coefficients determined from Fourier transform pulsed-gradient spin-echo NMR based self-diffusion data. Application to anesthetic binding in tetracaine-phosphatidylcholine-water systems |
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| Authors: | Peter Stilbs Gösta Arvidson Göran Lindblom |
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| Affiliation: | 1. Institute of Physical Chemistry, Uppsala University, Box 532, S-75121 Uppsala Sweden;2. Department of Medical and Physiological Chemistry, Uppsala University, Biomedical Center, Box 575, S-75123 Uppsala Sweden;3. Department of Physical Chemistry, Umeå University, S-90187 Umeå Sweden |
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| Abstract: | Multicomponent self-diffusion data on dioleoyl(DOL)- and dipalmitoyllecithin (DPL) vesicle-water systems have been determined using a Fourier transform NMR technique. The self-diffusion of vesicles is characterized by diffusion coefficients two magnitudes lower than that of small molecules in solution. Consequently, the degree of binding of small molecules is strongly reflected in their time-averaged self-diffusion coefficient in vesicle-water systems. This provides a new basis for the determination of vesicle-water partition equilibria. The feasibility of the technique has been investigated in one anesthetic-lipid system and is found to be very good. The binding of the hydrochloride form of tetracaine to DOL vesicles at pH 3 and 7 (Kp = 30–50) is found to be very much lower than that of the neutral molecule at pH 9 (Kp = 800–900). No significant difference in the tetracaine binding characteristics was found between DOL, DOL-cholesterol and DPL systems. |
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| Keywords: | vesicles anesthetics tetracaine NMR partition coefficients self-diffusion |
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