Document Detail


Quantitative determination of hydrocarbon chain conformational order in bilayers of saturated phosphatidylcholines of various chain lengths by Fourier transform infrared spectroscopy.
MedLine Citation:
PMID:  2386779     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The infrared spectra of aqueous dispersions of a homologous series of symmetric-chain, disaturated phosphatidylcholines, with fatty acyl chain lengths ranging from 12 to 19 carbons, have been measured at comparable reduced temperatures in their liquid-crystalline phases. The infrared spectra of these compounds contain bands that are dependent on the conformation of the fatty acyl chains. In particular, in the 1400-1300-cm-1 spectral region, there are bands due to CH2 wagging which are specific for the different types of gauche conformers. Thus, gauche-trans-gauché sequences (or kinks) give a band at 1367 cm-1, end-gauche conformers a band at 1341 cm-1, and double-gauche conformers a band at 1355 cm-1. The intensities of these bands were determined and normalized to the intensity of the conformation-insensitive band due to symmetric methyl bending at 1378 cm-1. The intensities of the different "gauche" bands yield a "per chain" intensity, which is directly related to the concentration of the different types of conformational defects. We find that, within experimental error, the concentration of end-gauche and double-gauche conformers is relatively low and practically invariant with chain length when a series of homologous phosphatidylcholines are compared at the same reduced temperature. In contrast, the concentration of gauche-trans-gauché sequences (kink defects) is much higher and increases as the chain length increases. For dipalmitoylphosphatidylcholine we find that there are about 1.2 kink, 0.5-0.6 end-gauche, and 0.4 double-gauche conformers per hydrocarbon chain.(ABSTRACT TRUNCATED AT 250 WORDS)
Authors:
H L Casal; R N McElhaney
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochemistry     Volume:  29     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1990 Jun 
Date Detail:
Created Date:  1990-09-27     Completed Date:  1990-09-27     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  5423-7     Citation Subset:  IM    
Affiliation:
Division of Chemistry, National Research Council, Ottawa, Ontario, Canada.
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MeSH Terms
Descriptor/Qualifier:
Fourier Analysis
Lipid Bilayers*
Molecular Conformation
Phosphatidylcholines*
Spectrophotometry, Infrared
Water
Chemical
Reg. No./Substance:
0/Lipid Bilayers; 0/Phosphatidylcholines; 7732-18-5/Water

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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