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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
17
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pubmed:dateCreated |
1990-8-6
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pubmed:abstractText |
The structural and thermotropic properties of the hydrated mixed-chain phosphatidylcholines (PCs), C(8):C(18)-PC and C(10):C(18)-PC, have been studied by X-ray diffraction and differential scanning calorimetry. For fully hydrated C(8):C(18)-PC, the reversible chain melting transition is observed at 9.9 degrees C (delta H = 7.3 kcal/mol). X-ray diffraction at 0 degrees C (below the chain melting transition) shows a small bilayer repeat distance, d = 51.0 A, and a sharp, symmetric wide-angle reflection at 4.1 A, characteristic of a mixed interdigitated bilayer gel phase [see McIntosh, T. J., Simon, S. A., Ellington, J. C., Jr., & Porter, N. A. (1984) Biochemistry 23, 4038-4044; Hui, S. W., Mason, J. T., & Huang, C. (1984) Biochemistry 23, 5570-5577]. At 30 degrees C (above the chain melting transition), a diffuse band is observed at 4.5 A characteristic of an L alpha phase but with an increased bilayer periodicity, d = 61 A. Both the calculated lipid bilayer thickness (d1) and that determined directly from electron density profiles (dp-p) show unusual increases as a consequence of chain melting. In contrast, fully hydrated C(10):C(18)-PC shows an asymmetric endothermic transition at 11.8 degrees C. Below the chain melting transition, two lamellar phases are present, corresponding to coexisting interdigitated (d = 52.3 A) and noninterdigitated (d = 62.5 A) bilayer gel phases. The relative amounts of these phases depend upon the low-temperature incubation and/or hydration conditions, suggesting conversions, albeit kinetically complex, between metastable, and stable phases. The different behavior of C(8):C(18)-PC and C(10):C(18)-PC, as well as their positional isomers, is rationalized in terms of the molecular conformation of PC.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical | |
pubmed:status |
MEDLINE
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pubmed:month |
May
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pubmed:issn |
0006-2960
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
1
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pubmed:volume |
29
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
4254-62
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pubmed:dateRevised |
2007-11-14
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pubmed:meshHeading |
pubmed-meshheading:2361142-Calorimetry, Differential Scanning,
pubmed-meshheading:2361142-Lipid Bilayers,
pubmed-meshheading:2361142-Molecular Conformation,
pubmed-meshheading:2361142-Phosphatidylcholines,
pubmed-meshheading:2361142-Structure-Activity Relationship,
pubmed-meshheading:2361142-Thermodynamics,
pubmed-meshheading:2361142-Water,
pubmed-meshheading:2361142-X-Ray Diffraction
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pubmed:year |
1990
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pubmed:articleTitle |
Structure and properties of mixed-chain phosphatidylcholine bilayers.
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pubmed:affiliation |
Department of Biophysics, Boston University School of Medicine, Housman Medical Research Center, Massachusetts 02118.
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pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.
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