Abstract
The translational diffusion coefficient and the partition coefficient of a spin-labeled solute, di-t-butyl nitroxide, in an aqueous suspension of dipalmitoyl lecithin vesicles have been studied by electron spin resonance spectroscopy. When the lecithin is cooled through its phase transition temperature near 41°C, some solute is “frozen out” of the bilayer, and the standard partial molar enthalpy and entropy of partition go more positive by a factor of 8 and 6, respectively. However, the apparent diffusion constant in the lecithin phase is only slightly smaller than that in water, both above and below the transition temperature. The fraction of bilayer volume within which solute is distributed may increase with temperature, contributing to the positive enthalpy of partition. Comparison of time constants suggests that there is a permeability barrier to this solute in the periphery of the bilayer.
Keywords: electron spin resonance, permeability, liposomes, phospholipid, biological membranes
Full text
PDF![474](https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5568/388029/8f64e9efb46d/pnas00055-0236.png)
![475](https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5568/388029/8828009ccc4c/pnas00055-0237.png)
![476](https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5568/388029/954a3c3bdcbc/pnas00055-0238.png)
![477](https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5568/388029/3231597b4405/pnas00055-0239.png)
![478](https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5568/388029/d097097e7617/pnas00055-0240.png)
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Barratt M. D., Green D. K., Chapman D. E.S.R. studies of nitroxide probes in lecithin-water systems. Chem Phys Lipids. 1969 Apr;3(2):140–144. doi: 10.1016/0009-3084(69)90004-8. [DOI] [PubMed] [Google Scholar]
- Diamond J. M., Wright E. M. Biological membranes: the physical basis of ion and nonelectrolyte selectivity. Annu Rev Physiol. 1969;31:581–646. doi: 10.1146/annurev.ph.31.030169.003053. [DOI] [PubMed] [Google Scholar]
- Hubbell W. L., McConnell H. M. Molecular motion in spin-labeled phospholipids and membranes. J Am Chem Soc. 1971 Jan 27;93(2):314–326. doi: 10.1021/ja00731a005. [DOI] [PubMed] [Google Scholar]
- Hubbell W. L., McConnell H. M. Spin-label studies of the excitable membranes of nerve and muscle. Proc Natl Acad Sci U S A. 1968 Sep;61(1):12–16. doi: 10.1073/pnas.61.1.12. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lecuyer H., Dervichian D. G. Structure of aqueous mixtures of lecithin and cholesterol. J Mol Biol. 1969 Oct 14;45(1):39–57. doi: 10.1016/0022-2836(69)90208-3. [DOI] [PubMed] [Google Scholar]
- McConnell H. M., McFarland B. G. Physics and chemistry of spin labels. Q Rev Biophys. 1970 Feb;3(1):91–136. doi: 10.1017/s003358350000442x. [DOI] [PubMed] [Google Scholar]
- Roth S., Seeman P. The membrane concentrations of neutral and positive anesthetics (alcohols, chlorpromazine, morphine) fit the Meyer-Overton rule of anesthesia; negative narcotics do not. Biochim Biophys Acta. 1972 Jan 17;255(1):207–219. doi: 10.1016/0005-2736(72)90023-5. [DOI] [PubMed] [Google Scholar]
- Stark G., Ketterer B., Benz R., Läuger P. The rate constants of valinomycin-mediated ion transport through thin lipid membranes. Biophys J. 1971 Dec;11(12):981–994. doi: 10.1016/S0006-3495(71)86272-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Szabo G., Eisenman G., McLaughlin S. G., Krasne S. Ionic probes of membrane structures. Ann N Y Acad Sci. 1972 Jun 20;195:273–290. [PubMed] [Google Scholar]
- Waggoner A. S., Griffith O. H., Christensen C. R. Magnetic resonance of nitroxide probes in micelle-containing solutions. Proc Natl Acad Sci U S A. 1967 May;57(5):1198–1205. doi: 10.1073/pnas.57.5.1198. [DOI] [PMC free article] [PubMed] [Google Scholar]