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. 1994 May;66(5):1441–1449. doi: 10.1016/S0006-3495(94)80934-8

Molecular response of the lipid headgroup to bilayer hydration monitored by 2H-NMR.

A S Ulrich 1, A Watts 1
PMCID: PMC1275864  PMID: 8061193

Abstract

The effect of hydration on the conformation and dynamics of the phosphatidylcholine headgroup has been investigated by 2H-NMR measurements of liquid crystalline dioleoylphosphatidylcholine in multilamellar liposomes. Deuterium quadrupole splittings (delta nu Q) and spin-lattice relaxation rates (1/T1) were recorded for three selectively labeled headgroup segments (alpha, beta, and gamma) over the range of water/lipid mole ratios from 4 to 100. The smooth changes in delta nu Q and 1/T1 are found to essentially parallel each other and can be described by a single exponential decay function. Progressive hydration thus induces a concerted change in headgroup conformation together with an increase in its rate of motion (detected by delta nu Q and 1/T1, respectively). The enhanced mobility is partially due to a shift in the lipid phase transition temperature (as monitored by differential scanning calorimetry) and is furthermore attributed to an entropic contribution. It is concluded that the choline dipole becomes slightly raised in its average orientation into the aqueous layer and that the rate is increased at which the headgroup is fluctuating and protruding. The observed molecular changes can thus be accommodated within a model where the effective accessible headgroup volume expands with increasing hydration.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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