The Journal of Membrane Biology

, Volume 50, Issue 3–4, pp 241–255

Anionic detergents as divalent cation ionophores across black lipid membranes

  • Jonathan J. Abramson
  • Adil E. Shamoo
Article

DOI: 10.1007/BF01868891

Cite this article as:
Abramson, J.J. & Shamoo, A.E. J. Membrain Biol. (1979) 50: 241. doi:10.1007/BF01868891

Summary

Three ionic detergents commonly used in membrane-bound protein isolation and reconstitution experiments, SDS, cholate, and DOC, are shown to act as divalent cation ionophores when incorporated into black lipid membranes made from either oxidized cholesterol or a mixture of phosphatidylcholine and cholesterol (PC/cholesterol=5∶1 mg). At a concentration greater than or equal to 1 μm, SDS shows large selectivity differences between cations and anions and among the different cations tested (Ba2+, Ca2+, Sr2+, Mg2+, and Mn2+). Deoxycholate and cholate at concentrations greater than 4×10−4m and 10−3m, respectively, also act as divalent cation ionophores. The selectivity sequence measured for these two detergents is evidence for a strong ionic interaction between the divalent cation, and the anionic charged groups on the detergent. In the case of cholate, the conductance depends on the third or fourth power of the cholate concentration and shows a linear dependence on CaCl2 concentration. The conductance for deoxycholate depends on the sixth or seventh power of the DOC concentration and is also linearly dependent on the CaCl2 concentration. In an oxidized cholesterol black lipid membrane in the presence of 5mm CaCl2, small concentrations of LaCl3 (<1 μm) inhibit the ionophoric activity of each of the detergents tested. Evidence is presented to show that this inhibitory effect is a nonspecific effect on oxidized cholesterol BLM's, and is not due to a direct effect of La3+ on detergent-mediated transport.

Copyright information

© Springer-Verlag New York Inc 1979

Authors and Affiliations

  • Jonathan J. Abramson
    • 1
  • Adil E. Shamoo
    • 1
  1. 1.Department of Radiation Biology and BiophysicsUniversity of Rochester School of Medicine and DentistryRochester
  2. 2.Department of PhysicsPortland State UniversityPortland
  3. 3.Department of Biological ChemistryUniversity of Maryland School of MedicineBaltimore

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