Incorporation of phosphonic acid diesters into lipid model membranes Part I. Influence of the esters on the phase behaviour of egg yolk lecithin water systems and their orientational behaviour at low water content as seen by 2H- and 31P-NMR
✍ Scribed by G. Klose; A. Möps; K. Haage
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 774 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0009-3084
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✦ Synopsis
Mixtures of egg yolk lecithin and phosphonic acid diethyl or dibutyl esters of the general type RP(O) (OR'): with R = hexane or dodecane were studied at low water concentration using 3~p. and :H-NMR. (1) The esters cause a phase transition Lo--H H at room temperature. This cannot be observed in pure egg yolk lecithin/water mixtures on decreasing the water content. (2) A redistribution of the esters at the phase transition takes place. The esters are excluded from the more ordered glycerol backbone and are forced into the less ordered hydrocarbon chain region of the lipids. Hexyl phosphonic dibutylester shows some peculiarities. A certain redistribution of these esters already takes place in the L phase. (3) The angle between the phosphoryl group and the molecular symmetry axis increases in the sequence hexyl dibutyl, hexyl diethyl, dodecyl diethyl ester. It increases also with decreasing water concentration. (4) The molecular order parameter increases in the sequence hexyl dibutyl, hexyl diethyl, dodecyl diethyl ester. It increases significantly in dodecyl ester but not in the others with decreasing water concentration. The results obtained are qualitatively explained by the interplay of different forces.