Electric field-induced lateral mobility of photosystem I in the photosynthetic membrane

Abstract

Electrophoretic movement of photosystem I (PS I) along the photosynthetic membrane of hypotonically swollen thylakoid vesicles was studied by analyzing the electric field-stimulated delayed luminescence (electrophotoluminescence) emitted from PS I. The electrophoretic mobility was inferred from the differences in electrophotoluminescence (EPL) of the photosynthetic vesicles in presence and absence of trains of low amplitude (<80 V/cm) prepulses of 1 ms duration at 4 ms spacing. The average apparent electric mobility, determined from the time course of EPL increase on one hemisphere or its decrease on the other one, as function of prepulse length and intensity was of the order of 3 . 10(-5) cm(2)V(-1)s(-1). The assymetric distribution of the PS I reached a steady state when the diffusional, electrostatic, and elastic forces balanced the electrophoretic driving force. A lateral diffusion coefficient of approximately 5 . 10(-9) cm(2)s(-1) was found for the PS I complex from the diffusional relaxation after cessation of the electric field pulse train. Experimental conditions such as concentration, temperature, and viscosity of the aqueous solution were not critical for the effect. Between 23 and 150 electron charges per moving particle were estimated from the measured electrophoretic mobility.

Electroendocytosis: Exposure of Cells to Pulsed Low Electric Fields Enhances Adsorption and Uptake of Macromolecules

“…where E u will induce electrophoretic mobility toward the anodic or cathodic sides of the cell, either by direct electrophoretic mobility of the negatively charged components or by electroosmosis, respectively (McLaughlin and Poo, 1981). Though most studies of lateral electrophoretic segregation of charged membrane components have been carried out on adherent cells employing low DC electric fields (e.g., Poo, 1981;Wang et al, 2003), it was shown that a similar segregation phenomenon could be induced in photosynthetic membrane vesicles of a size comparable to that of cells (Brumfeld et al, 1989;Miller et al, 1994), when exposed in suspension to a train of unipolar pulsed electric fields of duration much shorter than the rotational time of the vesicles. Under these conditions the membrane vesicle can be considered to be in a rotational stationary state, at which time the lateral electrophoretic displacement takes place.…”

Thermodynamical and structural information on photosynthetic systems obtained from electroluminescence kinetics

“…Since its discovery in 1971 by Arnold and Azzi (6), electroluminescence has been mostly used as a quantitative probe for precursor concentrations (9-1 1) as a qualitative indicator of electro-genicity (6,10) and as a probe of the electric and diffusion properties of the membrane (12)(13)(14). The temporal and spatial distribution of local fields in the systems used is reflected in the electroluminescence kinetics and polarization and therefore the quantitative interpretation of these properties in terms of electrogenic and thermodynamic parameters is not straightforward and has not been attempted to date.…”

Electroluminescence

“…the bleb inside corresponding to the thylakoid lumen (de Grooth et al 1980b). The asymmetric distribution of the patches explains why orientation effects can occur by gravity (unpublished observations) and by an electric field, as indicated by a field-induced polarization of light scattering (de Grooth et al 1980a), which may provide a more likely explanation for the EL data of Brumfeld et al (1989) than the proposed electrophoretic movement of PSI complexes from one half of the bleb to the other. de Grooth et al 1980a).…”