HYDROPHOBIZING EFFECT OF CATIONS ON ACIDIC PHOSPHOLIPID MEMBRANES |
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| Authors: | M. Mirza Y. Guo K. Arnold C.J.van Oss S. Ohki |
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| Affiliation: | 1. Department of Physiology and Biophysics , State University of New York at Buffalo , Buffalo, NY, 14214, U.S.A.;2. Department of Chemical Engineering , State University of New York at Buffalo , Buffalo, NY, 14214, U.S.A.;3. Medical Faculty, University of Leipzig , D-04103 Leipzig, Germany;4. Department of Microbiology , State University of New York at Buffalo , Buffalo, NY, 14214, U.S.A.;5. Department of Chemical Engineering , State University of New York at Buffalo , Buffalo, NY, 14214, U.S.A.;6. Department of Geology , State University of New York at Buffalo , Buffalo, NY, 14214, U.S.A. |
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| Abstract: | By means of contact angle measurements with water and aqueous salt solutions, it is shown that plurivalent cations increase the hydrophobicity of negatively charged phospholipid vesicle membranes (consisting of phosphatidic acid, PA, or of phosphatidylserine, PS), but does not influence the hydrophobicity of neutral phospholipid membranes, (e.g., phosphatidylcholine, PC, at up to 200 mM of CaCl2). The hydrophobizing action of cations on PA and PS membranes is concomitant with the reduction in (negative) zeta potential with increasing cation concentrations. Trivalent cations, La3+, showed more effective in hydrophobizing negatively charged phospholipid membranes than divalent and monovalent cations. Except for hydrogen ions, monovalent cations do not show any appreciable hydrophobizing effect on lipid vesicle membranes at concentrations less than 1 M. The hydrophobizing effect on phospholipid membranes can also be used to explain the induction of lateral phase separation into patches of different phospholipids as well as cell fusion. |
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