Portland State University. Department of Physics.
Date of Award
Doctor of Philosophy (Ph.D.) in Environmental Sciences and Resources: Physics
Environmental Science and Management
3, xx, 221 leaves: ill., charts 28 cm.
Biophysics, Biological transport, Protons, Lipid membranes
This dissertation represents an attempt to understand the mechanism of the action of pesticides derived from chlorinated phenols (pentachlorophenol, pentachlorobenzenethiol, and 2,4,5-trichlorophenol) in lipid membranes; specifically, the kinetics of pesticide induced hydrogen ion transfer in lecithin-cholesterol membranes and its relationship to uncoupling activity in energy transducing membranes. Information on pesticide induced charge transport in membranes was obtained from the measurements of steady state and transient membrane conductance and membrane potentials as a function of the composition of the aqueous phase surrounding the membrane and of membrane composition. In addition, a systematic theoretical study of a series of membrane transport models was performed in order to elucidate the various aspects of membrane transport kinetics and to make predictions relevant to the interpretation of experimental results. Based on the theoretical results, two kinetic schemes of membrane transport were proposed to explain the experimental results; one for pentachlorophenol and 2,4,5-trichlorophenol, and another for pentachlorobenzenthiol. The schemes differ in the proposed mechanism of charge transfer across membrane water interface. Some conclusions regarding the rate limiting step in the charge transport process are drawn. Measurements of membrane surface potentials based on the microelectrophoretic method reveal that the density of ionized pentachlorophenol at the membrane surface can be predicted from the Langmuir adsorption model, provided that electrostatic repulsion between pentachlorophenol ions adsorbed at the membrane and free ions in the aqueous phase is taken into account. The fact that the adsorption of positively charged tetraphenylarsonium ions and negatively charged salicylate ions modify the membrane charge transport induced by 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The 2,4,5-trichlorophenol, can be explained by electrostatic arguments. The ability of pentachlorobenzenethiol and of chlorinated phenols to induce proton transport in membranes is regarded as the origin for both the membrane electrical conductivity and their toxic action in energy transducing membranes. We have found similarities between the pH dependence of pentachlorobenzenethiol induced membrane conductance and the pH dependence of the pentachlorobenzenethiol uncoupling activity found in mitochondria, as reported in the literature. We have also found that the level of pentachlorophenol concentration at which the membrane conductance increases above the background level corresponds to the onset of reduction of carbon uptake by algae.
Jayaweera, Ananda Ranjith, "Kinetics of proton transport in lipid membranes induced by some chlorinated phenols" (1982). Dissertations and Theses. Paper 215.