Quantitation of lateral stress in lipid layer containing nonbilayer phase preferring lipids by frequency-domain fluorescence spectroscopy

• Published in: Biochemistry (Easton) Vol. 31; no. 15; pp. 3759 - 3768
• Main Authors: Chen, Sun Yung, Cheng, Kwan Hon, Van der Meer, B. Wieb
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.1992
• Subjects: Artificial membranes and reconstituted systems; Biological and medical sciences; Diffusion; dioleoylphosphatidyl ethanolamine; fluorescence; Fluorescence Polarization; Fundamental and applied biological sciences. Psychology; Lipid Bilayers; Mathematics; Membrane physicochemistry; Molecular biophysics; Phosphatidylcholines - chemistry; Phosphatidylethanolamines - chemistry; quantitation; stress; Temperature; Molecular arrangement; Temperature; Molecular dynamics; Phospholipid; Lipids; Artificial membrane; Phase transitions
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00130a005

Frequency-resolved fluorescence measurements have been performed to quantitate the lateral stress of the lipid layer containing nonbilayer phase preferring dioleoylphosphatidylethanolamine (DOPE). On the basis of a new rotational diffusion model, the wobbling diffusion constant (Dw), the curvature-related hopping diffusion constant (DH), and the two local orientational order parameters ([P2] and [P4]) of 1-palmitoyl-2-[[2-[4-(6-phenyl-trans-1,3,5-hexatrienyl)phenyl]ethyl] carbonyl]-3-sn-phosphatidylcholine (DPH-PC) in fully hydrated DOPE and DOPE/dioleoylphosphatidylcholine (DOPC) mixtures were calculated from the frequency-domain anisotropy data. The values of [P2], [P4], and DH for DOPE were found to increase significantly at approximately 12 degrees C, the known lamellar liquid crystalline (L alpha) to inverted hexagonal (HII) phase transition temperature of DOPE. Similar features as well as a decline of Dw were detected in the DOPE/DOPC mixtures as the DOPE content was increased from 85% to 90% at 23 degrees C, corresponding to the known lyotropic phase transition of the DOPE/DOPC. In contrast, for DOPC (0-40 degrees C) and DOPE/DOPC (0-100% DOPE at 3 degrees C), which remained in the L alpha phase, these changes were not detected. The most probable local orientation of DPH-PC in the DOPE/DOPC mixtures shifted progressively toward the normal of the lipid/water interface as the content of DOPE increased. We concluded that the curvature-related lateral stress in the lipid layer increases with the content of the nonbilayer phase preferring lipids.