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Molecular mechanics simulation studies of dienoic hydrocarbons: From alkenes to 1‐Palmitoyl‐2‐linoleoyl‐phosphatidylcholines
Author(s) -
Li Shusen,
Huang ChingHsien
Publication year - 1996
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(199606)17:8<1013::aid-jcc10>3.0.co;2-f
Subject(s) - chemistry , bilayer , steric effects , crystallography , chain (unit) , force field (fiction) , double bond , lipid bilayer , stereochemistry , phosphatidylcholine , organic chemistry , physics , membrane , phospholipid , biochemistry , quantum mechanics , astronomy
Although no crystal structures of mixed‐chain phosphatidylcholines with unsaturated sn ‐2 acyl chains exist, the force field method in conjunction with the experimentally determined structure of saturated identical‐chain phosphatidylcholine can be applied to simulate molecular structure for mixed‐chain phosphatidylcholines. In this study, the packing models of mixed‐chain 1‐palmitoyl‐2‐linoleoyl‐phosphatidylcholines in bilayers at temperatures below the gel‐liquid crystalline phase transition temperature or T < T m are simulated by using Allinger's MM3(92) force field. Our results indicate that the unsaturated sn ‐2 acyl chains of the mixed‐chain lipid can fold into two energy‐minimized topologies: the crankshaftlike and the U‐shaped motifs. The folded region in the crankshiftlike sn ‐2 acyl chain is characterized by a sequence s − Δ s + s + Δ s − , and the U‐shaped chain arises from the characteristic sequence s − Δ s + s − Δ s + , where s ± denotes the ± skew conformation and Δ the cis carbon‐carbon double bond. These modeled structures of 1‐palmitoyl‐2‐linoleoyl‐phosphatidylcholines in the bilayer at T < T m should not be regarded as highly rigid structures, since torsion angles of carbon‐carbon bonds associated with sequences s Δ s + s + Δ s and s Δ s + s − Δ s + can fluctuate somewhat without appreciably affecting the steric energy of the corresponding lipid bilayer. © 1996 by John Wiley & Sons, Inc.