TRAPPING MAGNETICALLY ORIENTED CHLOROPLAST THYLAKOID MEMBRANES IN GELS FOR ELECTRIC MEASUREMENTS

Electrochromic absorbance change and light gradient photovoltage measu rements were carried out in chloroplast thylakoid membranes embedded i n different compositions of gels. The goal was to find a system suitab le for determining the dependence of the amplitude of the anomalous li ght gradient photovoltage signal, with opposite sign with respect to t he ordinary signal, on the alignment of membranes. We found that polya crylamide gel drastically increased the permeability of membranes whic h rendered electric measurements impossible in this gel. Agarose gel w as successfully used in electric measurements. We will show that the l ight gradient photovoltage induced by a 580 nm laser flash depends str ongly on the alignment of membranes with respect to the direction of t he excitation beam. With face-aligned membranes the amplitude of the a nomalous (negative) signal was drastically diminished, and the ordinar y (positive) signal became clearly discernible. The observed differenc es in the decay of the two signals are tentatively explained by differ ences in the rates of ionic equilibration between different subcompart ments of the inner aqueous phase of the thylakoid membrane system.