Biophysical Journal 66: 1515-1521 (1994)
© 1994 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ge, M Articles by Freed, J H Search for Related Content PubMed PubMed Citation Articles by Ge, M Articles by Freed, J H

An electron spin resonance study of interactions between phosphatidylcholine and phosphatidylserine in oriented membranes.

Baker Laboratory of Chemistry, Cornell University, Ithaca, New York 14853.

ABSTRACT

A detailed electron spin resonance (ESR) study of mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and phosphatidylserine (POPS) in oriented multilayers in the liquid crystalline phase is reported with the purpose of characterizing the effects of headgroup mixing on the structural and dynamical properties of the acyl chains. These studies were performed over a range of blends of POPC and POPS and temperatures, utilizing the spin-labeled lipids 16-phosphatidylcholine and 5-phosphatidylcholine as well as cholestane (CSL). The ESR spectra were analyzed by nonlinear least-squares fitting using detailed spectral simulations. Whereas CSL shows almost no variation in ordering and rotational dynamics versus mole fraction POPS, (i.e. XPS), and 5-PC shows small effects, the weakly ordered end-chain labeled 16-PC shows large relative effects, such that the orientational order parameter, S is at a minimum for XPS = 0.5 where it is about one-third the value observed for XPS = 0 and 1. This is directly reflected in the ESR spectrum as a substantial variation in the hyperfine splitting with XPS. The least-squares analysis also shows a reduction in rotational diffusion coefficient, R perpendicular by a fractor of 2 for XPS = 0.5 and permits the estimation of S2, the ordering parameter representing deviations from cylindrically symmetric alignment. These results are contrasted with 2H NMR studies which were insensitive to effects of mixing headgroups on the acyl chains. The ESR results are consistent with a somewhat increased disorder in the end-chain region as well as a small amount of chain tilting upon mixing POPC and POPS.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				K. Jacobsen, S. Oga, W. L. Hubbell, and T. Risse Determination of the Orientation of T4 Lysozyme Vectorially Bound to a Planar-Supported Lipid Bilayer Using Site-Directed Spin Labeling Biophys. J., June 1, 2005; 88(6): 4351 - 4365. [Abstract] [Full Text] [PDF]

				Y.-W. Chiang, Y. Shimoyama, G. W. Feigenson, and J. H. Freed Dynamic Molecular Structure of DPPC-DLPC-Cholesterol Ternary Lipid System by Spin-Label Electron Spin Resonance Biophys. J., October 1, 2004; 87(4): 2483 - 2496. [Abstract] [Full Text] [PDF]

				M. Ge, A. Gidwani, H. A. Brown, D. Holowka, B. Baird, and J. H. Freed Ordered and Disordered Phases Coexist in Plasma Membrane Vesicles of RBL-2H3 Mast Cells. An ESR Study Biophys. J., August 1, 2003; 85(2): 1278 - 1288. [Abstract] [Full Text] [PDF]