Anionic detergents as divalent cation ionophores across black lipid membranes
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. At a concentration greater than or equal to 1 ..mu..m, SDS shows large selectivity differences between cations and anions and among the different cations tested. Deoxycholate and cholate at concentrations greater than 4 x 10/sup -4/ m and 10/sup -3/ m, respectively, also act as divalent cation ionophores. The selectivity sequences 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 CaCl/sub 2/ concentration. The conductance for deoxycholate depends on the sixth or seventh power of the DOC concentration and is also linearly dependent on the CaCl/sub 2/ concentration. In an oxidized cholesterol black lipid membrane in the presence of 5 mm CaCl/sub 2/, small concentrations of LaCl/sub 3/ 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 La/sup 3 +/ on detergent-mediated transport.
- Research Organization:
- Univ. of Rochester School of Medicine and Dentistry, NY
- OSTI ID:
- 6357219
- Journal Information:
- J. Membr. Biol.; (United States), Vol. 50
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANIONS
MEMBRANE TRANSPORT
CATIONS
DETERGENTS
BIOLOGICAL EFFECTS
MEMBRANES
ION EXCHANGE
BIOCHEMISTRY
CALCIUM CHLORIDES
CHOLESTEROL
LIPOPROTEINS
QUANTITY RATIO
SENSITIVITY
ADDITIVES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM HALIDES
CHARGED PARTICLES
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
EMULSIFIERS
HALIDES
HALOGEN COMPOUNDS
HYDROXY COMPOUNDS
IONS
LIPIDS
ORGANIC COMPOUNDS
PROTEINS
STEROIDS
STEROLS
SURFACTANTS
WETTING AGENTS
550200* - Biochemistry
550300 - Cytology