An analysis of flash-induced electrical transients of a BLM containing chloroplast lamella extracts |
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Authors: | H Ti Tien J S Huebner |
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Institution: | (1) Department of Biophysics, Michigan State University, 48823 East Lansing, Michigan;(2) Present address: Natural Sciences Department, University of North Florida, 32216 Jacksonville, Florida |
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Abstract: | Summary The electrical transients produced by chloroplast bilayer lipid membranes (Chl-BLM) from flash excitation are seen to result from three photocurrents and a discharge current. Each of the three photo-initiated charge transports in Chl-BLM (designated as Components A, B and C) exhibits an action spectrum similar to chlorophyll absorption spectra. The fast components (A and B), which are induced by electron acceptors such as Fe+3, have rise-times of 3 sec and 20 msec, and occur in TLM (thin lipid membranes, i.e., colored membranes up to 1 thick) as well as in BLM. Component C is induced by a transmembrane pH difference or applied voltage, has a rise-time of 1 sec, and occurs only in BLM. Component C is associated with exciton dissociation and proton transport. The mobility of the Component A current carriers in TLM is estimated to be about 1×10–2 cm2/volt sec, and are, hence,electronic. The photovoltage waveforms are described by equations developed, which consider Component A as being caused by a direct charge separation proportional to the illumination intensity (within 0.5 sec), and Components B and C being caused by two types of exciton processes which cause charge transport after the illumination period. |
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