ISSN:
0192-8651
Keywords:
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Computer Science
Notes:
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 〈 Tm 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- Δs+s+Δs-, and the U-shaped chain arises from the characteristic sequence s-Δs+s-Δs+, 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 〈 Tm should not be regarded as highly rigid structures, since torsion angles of carbon-carbon bonds associated with sequences s Δs+s+Δs and s Δs+s-Δ s+ can fluctuate somewhat without appreciably affecting the steric energy of the corresponding lipid bilayer. © 1996 by John Wiley & Sons, Inc.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
