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Interaction of electric dipoles with phospholipid head groups : a 2H and 31P NMR study of phloretin and phloretin analogues in phosphatidylcholine membranes

Bechinger, B. and Seelig, J.. (1991) Interaction of electric dipoles with phospholipid head groups : a 2H and 31P NMR study of phloretin and phloretin analogues in phosphatidylcholine membranes. Biochemistry, Vol. 30, H. 16. S. 3923-3929.

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Official URL: http://edoc.unibas.ch/dok/A5257462

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Abstract

Phloretin, 4-hydroxyvalerophenone, and 2-hydroxy-omega-phenylpropiophenone are lipophilic dipolar substances that modify ionic conductances of bilayer membranes. The structural changes at the level of the head groups and the hydrocarbon chains as induced by the incorporation of phloretin and its analogues were investigated with deuterium and phosphorus nuclear magnetic resonance. Membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were selectively deuterated at the choline head group and at the hydrocarbon chains, and 2H and 31P NMR spectra were recorded with varying concentrations of dipolar agents. Incorporation of phloretin leaves the bilayer structure intact, induces only a small disordering of the hydrocarbon chains, and has no significant effect on the head-group dynamics. On the other hand, quite distinct structural changes are observed for the phosphocholine head group. While the -P-N+ dipole is oriented approximately parallel to the membrane surface for pure POPC bilayers, addition of phloretin, and to a lesser extent 4-hydroxyvalerophenone and 2-hydroxy-omega-phenylpropiophenone, rotates the N+ end of the -P-N+ dipole closer to the hydrocarbon layer. The resulting normal component of the -P-N+ dipole partly compensates the electric field of the dipolar agents. In addition to this structural change, phloretin also modifies the hydration layer at the lipid-water interface. Much less 2H2O is adsorbed to the membrane surface when the bilayer contains phloretin, 4-hydroxyvalerophenone, or 2-hydroxy-omega-phenylpropiophenone. Moreover, a rather large change in the residual phosphorus chemical shielding anisotropy argues in favor of hydrogen-bond formation between the phosphate segment and the phloretin hydroxyl groups.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig J)
UniBasel Contributors:Seelig, Joachim
Item Type:Article, refereed
Bibsysno:Link to catalogue
Publisher:American Chemical Society
ISSN:0006-2960
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:19
Deposited On:22 Mar 2012 13:18

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