Document Detail

The effect of hydrostatic pressure on the bilayer structure of phosphatidylcholines containing omega-cyclohexyl fatty acyl chains.
MedLine Citation:
PMID:  2397234     Owner:  NLM     Status:  MEDLINE    
The barotropic behavior of aqueous dispersions of two representative omega-cyclohexyl phosphatidylcholines was investigated by pressure-tuning Fourier transform infrared spectroscopy. In the even-numbered homologue, 1,2-di-14-cyclohexyltetradecanoyl-sn-glycero-3-phosphocholine (14cyPC), the lipid molecules are orientationally disordered until the applied pressure reaches 2.1 kbar. This pressure marks the onset of correlation field splitting of the scissoring and rocking modes of the linear chain methylenes, as well as that of the cyclohexyl ring methylenes. It indicates immobilization of the entire acyl chains, whereby the zig-zag planes of the neighboring straight chain all-trans methylenes are oriented mainly perpendicular to each other. As judged from the magnitude of the correlation field splittings, the interchain interaction is weaker in 14cyPC than that in linear lipids (e.g., DMPC or DPPC). Upon an increase in pressure, up to 20 kbar, the zig-zag methylene planes in 14cyPC undergo a gradual transformation to a parallel orientation. In the odd-numbered homologue, 1,2-di-13-cyclohexyltridecanoyl-sn-glycero-3-phosphocholine (13cyPC), there is no correlation field splitting originating from the straight chain methylenes (up to 21 kbar). The linear, nonbranched segments of the omega-cyclohexyl chains in 13cyPC are closely packed with the all-trans methylene zig-zag planes oriented parallel to each other. There is, however, correlation field splitting of the ring methylenes, indicating interring interactions between the bulky cyclohexyl rings in opposing bilayer leaflets. There are major structural differences between the even- and odd-numbered homologues in the interfacial region, which remain even at high pressures. The ester carbonyl C = O stretching band in 14cyPC is a composite of two discrete bands which do not change considerably in intensity or frequency in the pressure range 2-20 kbar. In contrast, 13cyPC possesses an additional, low-frequency C = O stretching component at low pressures. As the pressure increases, the three component bands coalesce into a single C = O stretching band. Our results suggest equally oriented, fully hydrogen-bonded carbonyl groups in 13cyPC at pressures above approx. 10 kbar.
W Hübner; P T Wong; H H Mantsch
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1027     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1990 Sep 
Date Detail:
Created Date:  1990-10-16     Completed Date:  1990-10-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  229-37     Citation Subset:  IM    
Division of Chemistry, National Research Council, Ottawa, Canada.
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MeSH Terms
Fourier Analysis
Hydrostatic Pressure
Lipid Bilayers / metabolism*
Phosphatidylcholines / metabolism*
Spectrophotometry, Infrared
Structure-Activity Relationship
Reg. No./Substance:
0/Lipid Bilayers; 0/Phosphatidylcholines

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