Elsevier

Biophysical Chemistry

Volume 44, Issue 2, September 1992, Pages 91-97
Biophysical Chemistry

Electro-optical investigation of lipid-depleted purple membranes

https://doi.org/10.1016/0301-4622(92)85041-2Get rights and content

Abstract

The effect of delipidation on the electric surface properties of purple membranes was investigated by electric light scattering and microelectrophoresis. Natural membrane lipids were partially removed (approximately 75% of the phospholipids are extracted) from purple membrane using mild treatment with the zwitterionic bile salt 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate. Partial delipidation of purple membrane fragments causes: (i) a strong reduction of the permanent dipole moment from 6.10 X 10−24 Cm for native to 0.56 X 10−24 Cm for delipidated purple membranes, and (ii) a two-fold decrease in the electric polarizability. The ionic strength effect on the electric surface properties of delipidated purple membranes confirms the electrokinetic nature of a part of the membrane charge asymmetry. The contribution of the native membrane lipids to the electro-optically observed permanent dipole moment, i.e. to the membrane charge asymmetry, of purple membrane is demonstrated.

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