Influence of stray capacitance and sample resistance on the kinetics of fast photovoltages from oriented purple membranes

H. W. Trissl, A. Der, P. Ormos, L. Keszthelyi

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Flash-induced photovoltages were measured with metal electrodes in two experimental systems of purple membranes oriented by an electric field. One system consisted of a suspension of purple membranes cooled to 80 K. The photovoltage evoked by a xenon flash lamp displayed a single phase with a fast rise and a slow RC-decay. The signal shape is consistent with a fast charge separation occurring before the decay of the K-intermediate. The other system consisted of purple membranes embedded and stabilized in polyacrylamide gel. At room temperature, the photovoltage, evoked by a 10 ns laser flash, displayed a negative phase in the submicrosecond range and a slower positive one. The shape of the signals were altered in a complex manner by the stray capacitance and the ionic strength. The rise-time of the negative phase was approx. 14 and approx. 40 ns at ionic strengths of 10 and 1 mM, respectively. The initial peak amplitudes of the photovoltage from both experimental systems depended on the external capacitance in an inverse manner, indicating that both experimental systems were not impedance-matched. The evaluation of kinetic data of molecular reactions from measurements of the photovoltage is discussed.

Original languageEnglish
Pages (from-to)288-294
Number of pages7
JournalBBA - Bioenergetics
Issue number3
Publication statusPublished - Jun 26 1984



  • Bacteriorhodopsin
  • Charge separation
  • Membrane orientation
  • Photovoltage
  • Purple membrane

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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