Trapping magnetically oriented chloroplast thylacoid membranes
in gels for electric measurements

Szabolcs Osvath, Geza Meszena, V. Barzda and Gyozo Garab

J. Photochem. Photobiol. B, 26: 287-292 (1994)

Abstract

Electrochromic absorbance change and light gradient photovoltage measurements
were carried out in chloroplast thylacoid membranes embedded in different
compositons of gels. The goal was to find a system suitable for determining
the dependence of the amplitude of the anomalous light gradient photovoltage
signal, with opposite sign with respect to the ordinary signal, on the
alignment of membranes. We found that poliacrylamide gel drastically increased
the permeability of membranes which rendered electric measurements impossible
in gel.  Agarose gel was succesfully used in electric measurements. We will
show that the light gradient photovoltage induced by a 580 nm laser flash
depends strongly on the alignment of membranes with respect to the direction of
the exciting beam. With face-aligned membranes the amplitude of the anomalous
(negative) signal was drastically diminished, and the ordinary (positive)
signal become clearly discernible. The observed differences in the decay of
the two signals are tentatively explained by differences in the rates of ionic
equilibration between different subcompartments of the inner aqueous phase of
the thylakoid membrane system.