Document Detail

A computer investigation of intramolecular bond ordering: unsaturated chains of natural lipids.
MedLine Citation:
PMID:  10987392     Owner:  NLM     Status:  MEDLINE    
Computer simulations (by the Monte Carlo method) of unperturbed linear hydrocarbon chains of 18-22 carbon atoms with methylene-interrupted cis-double bonds (18:0, 20:0, 22:0, 18:1delta11cis, 18:2delta9, 12cis, 18:3delta9, 12, 15cis, 20:3delta5, 8, 11cis, 20:4delta5, 8, 11, 14cis, 20:5delta5, 8, 11, 14, 17cis, 22:6delta4, 7, 10, 13, 16, 19cis), typical components of natural lipids, at a temperature of 298 K have been carried out. The conformations generated with continuous variation of all single C-C bond rotation angles within the (0, 360 degrees) range have been considered. The energy of nonbonded interactions and torsion and electrostatic terms have been taken into account. The intramolecular bond order parameters S(CC) and S(CH) about the axes along inertia tensor eigenvectors and bond orientation distributions rho(theta) with respect to the maximum molecule span axis (theta is the angle between the bond and the axis) have been calculated. The relation of the bond orientation distributions rho(theta) to the order parameters S are analyzed in terms of angles thetamax (a "geometric" factor, rho(thetamax) = max) and widths deltatheta of the distributions (factor of "fluctuations"). The results indicate that fluctuation factors depend on both the segment chemical structure and location in the chain; fluctuations increase from the centre of the chain towards the terminals, all things being equal. The two deltatheta values of C-H bonds flanking the cis-double bond are smaller than that obtained for adjacent CH2 groups by a factor of 1.5-2. Defining these properties is a necessary step to gaining a more complete understanding of polyunsaturated lipid hydrocarbon chains significance. The mean molecule magnitudes of ¿S(CH)¿ decrease when unsaturation increases. The cis-double bond parameters S(CC) are found to be higher than those of adjacent single C-C bonds: the parameter S(CC) odd-even effect in the polyunsaturated molecules of such structure changes the "sign" between double bonds. The order parameter profiles -S(CH) of cis-18:1 and cis-18:2 obtained from the simulations (at the portion which corresponds to the double bonds location) are in qualitative agreement with experimental data on bilayers in the liquid-crystal phase. This has made possible the quantitative prognosis of the ordering properties of experimentally uninvestigated unsaturated lipids.
A L Rabinovich; P O Ripatti
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Membrane & cell biology     Volume:  13     ISSN:  1023-6597     ISO Abbreviation:  Membr Cell Biol     Publication Date:  2000  
Date Detail:
Created Date:  2000-12-11     Completed Date:  2001-02-01     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9517472     Medline TA:  Membr Cell Biol     Country:  SWITZERLAND    
Other Details:
Languages:  eng     Pagination:  697-714     Citation Subset:  IM    
Institute of Biology, Karelian Research Centre, Russian Academy of Sciences, Petrozavodsk.
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MeSH Terms
Computer Simulation*
Fatty Acids, Unsaturated / chemistry*
Models, Statistical
Monte Carlo Method
Reg. No./Substance:
0/Fatty Acids, Unsaturated

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