Abstract
Nuclear magnetic relaxation rates for water protons in aqueous palmitoyloleoylphosphatidylcholine vesicle suspensions containing different nitroxide free radical spin labels are reported as a function of magnetic field strength corresponding to proton Larmor frequencies from 10 kHz to 30 MHz. Under these conditions the water proton relaxation rate is determined by the magnetic coupling between the water protons and the paramagnetic nitroxide fixed on the phospholipid. This coupling is made time-dependent by the relative translational motion of the water proton spins past the nitroxide radical. Using theories developed by Freed and others, we interpret the NMR relaxation data in terms of localized water translational motion and find that the translational diffusion constant for water within approximately 10 A of the phospholipid surface is 6 x 10(-10) m2 s(-1) at 298 K. Similar results are obtained for three different nitroxide labels positioned at different points on the lipid. The diffusion is a thermally activated process with an activation energy only slightly higher than that for bulk water.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Hansen R. L., Harris J. M. Lateral diffusion of molecules partitioned into C-18 ligands on silica surfaces. Anal Chem. 1995 Feb 1;67(3):492–498. doi: 10.1021/ac00099a003. [DOI] [PubMed] [Google Scholar]
- Huang Z., Pearce K. H., Thompson N. L. Translational diffusion of bovine prothrombin fragment 1 weakly bound to supported planar membranes: measurement by total internal reflection with fluorescence pattern photobleaching recovery. Biophys J. 1994 Oct;67(4):1754–1766. doi: 10.1016/S0006-3495(94)80650-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Smith B. A., McConnell H. M. Determination of molecular motion in membranes using periodic pattern photobleaching. Proc Natl Acad Sci U S A. 1978 Jun;75(6):2759–2763. doi: 10.1073/pnas.75.6.2759. [DOI] [PMC free article] [PubMed] [Google Scholar]