2H- and 31P-NMR studies of bilayers composed of 1-acyllysophosphatidylcholine and fatty acids |
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Authors: | Peter R Allegrini Guus van Scharrenburg Gerard H De Haas Joachim Seelig |
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Institution: | 1. Biocenter of the University of Basel, Klingelbergstrasse 70, CH -4056 Basel Switzerland;2. Department of Biochemistry, The State University of Utrecht, Transitorium 3, Padualaan 8, 3508 TB Utrecht The Netherlands |
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Abstract: | 1-Palmitoyllysophosphatidylcholine has been mixed in equimolar amounts with specifically deuterated palmitic acid and the structural properties of the lipid/water phase have been studied by 2H- and 31P-nuclear magnetic resonance. The order profile of the free palmitic acid is very similar to that of the parent compound at temperatures above the gel-to-liquid crystal phase transition. The bending of the chain which is typical for diacyl lipids is not observed for the free palmitic acid. The mixture of lysolipid and palmitic acid exhibits well-defined quadrupole splittings even at temperatures below the gel-to-liquid crystal phase transition. Hence it is possible for the first time to establish an order profile in the gel-state of the lipid bilayer phase. Between carbon atoms 5 to 12 the palmitic acid chain is found to assume the extended all-trans conformation with a very small contribution from gauche defects. Towards the methyl terminal a distinct increase in the gauche probability can be noted. The motion of the phosphocholine headgroup was also studied by 2H- and 31P-NMR using selectively deuterated 1-palmitoyllysophosphatidylcholine. The headgroup has a considerably larger motional freedom in the mixture of lysolipid and palmitic acid than in . In addition, the average headgroup conformations are also different in the two systems. |
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Keywords: | Phosphatidylcholine Palmitic acid (Lipid bilayer) |
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