Detailed experimental data for conductivity and membrane potentials are presented for lecithin/cholesterol/decane bilayers in the presence of the uncoupler carbonylcyanidem-chlorophenylhydrazone (CCCP). These compare favorably with a theoretical model derived to explain the mechanism of action of uncouplers on bilayers. The model assumes that the weak acid uncoupler HA and its anion A(-) are the sole species which permeate the membrane. Its key feature is the recognition of the existence of unstirred aqueous layers on either side of the membrane. The model accounts for, among other things, a maximum in the transmembrane conductivity at a pH to the alkaline side of the uncoupler pK a and saturating current-voltage characteristics at high pH, both phenomena being found for CCCP. From a quantitative fit of model to data, values of 2.0×10(-3) and 11 cm/sec are deduced for the permeability coefficients of the CCCP anion and the undissociated CCCP molecule, respectively.
P:eviou~ I?obility measurements indicate that the band approximation can be used to describe the be-havIOr of l~lected holes and electrons in anthracene, and the present theoretical investigation appears to c?nfi.rm this. -:r:he s~ructu~.es of ~he bands ~pp~opriate to a hole or electron are calculated with the tight bm?mg apI;>roXlmation. Huckellmear combmatlOns of Slater-type atomic orbitals are used for the molecular baSls functIOns. Both ban~s. are highly anisotropic and each is found to be approximately 0.56 kT wide ~t roon;t tempera.ture. Mob1lity tensors are derived using a simplified treatment of scattering which assumes 1sotrop1C scatt~nng parameters: The calculated m?bilities exhibit roughly the anisotropy that has been o.bserved expenmentally. Magmtudes of the scattenng parameters are estimated from the observed mobilities, and these are found to be reasonable (e.g., free path> lattice distances).
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