Lipid polymorphism of mixtures of dioleoylphosphatidylethanolamine and saturated and monounsaturated phosphatidylcholines of various chain lengths

Journal Article · Tue Jan 13 04:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00375a031· OSTI ID:6520116

Tate, M W; Gruner, S M

The L/sub ..cap alpha../-H/sub II/ phase transition behavior of many lipid-water liquid crystals is dominated by the competition between the tendency to curl the lipid layers to an intrinsic radius of curvature and opposing hydrocarbon packing constraints. In particular, packing constraints can increase the free energy of the inverted hexagonal (H/sub II/) phase as compared to that of the lamellar (L/sub ..cap alpha../) phase. This is especially true where the lipid molecule is not long enough to reach into the corners of the lattice in large hexagonal structures necessitated by a large radius of curvature.In this paper it is shown that the addition of a minor fraction long-chain lipid to a system of otherwise uniform chain composition can also relax packing constraints, thereby lowering the lamellar to hexagonal transition temperature. For the specific systems used, dioleoylphosphatidylethanolamine (di-18:1/sub c/-PE) with minor fractions of 1,2-diacyl-sn-glycero-3-phosphocholines (di-n:1/sub c/-PC (n = 14, 18, 22, and 24)), the observed H/sub II/lattices systematically increased in size with increasing chain length suggesting that the chain length also may affect the intrinsic curvature of the mixture. These experiments demonstrate that the lipid shape concept, which is a qualitative expression of the concept quantitatively described by the intrinsic radius of curvature, is insufficient to understand the L/sub ..cap alpha../-H/sub II/ transition. It is necessary to, at least, consider the competition between curvature and packing.

• Research Organization: Princeton Univ., NJ
• DOE Contract Number: AC02-76EV03120
• OSTI ID: 6520116
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:1; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

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59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
CHEMISTRY
COHERENT SCATTERING
DIFFRACTION
ESTERS
LIPIDS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
PHYSICAL CHEMISTRY
SCATTERING
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION