Membrane potential light, effect

Biological membranes fluidity order parameters lipid-protein interactions translational diffusion site accessibility structural changes membrane potentials complexes and binding energy-linked and light-induced changes effects of additives location of proteins lateral organization and dynamics... 

This first observation of photofiexoelectricity in a biomimetic system allows us to speculate upon its possible existence in natural (e.g. photosynthetic) membranes as well. The existence of a converse effect (i.e., a photopotential-induced membrane curvature on illumination) also seems highly probable. The connectivity between membrane shape (curvature), light intensity and the membrane potential could be related to the mechanism responsible for phototaxis and other photoadaptive phenomena at the cell membrane level. 

It is a very interesting to know the role of electrical potential under conditions in which ApH across the thylakoid membrane is removed and electrical potential is not damaged, so as to eliminate the enhancement of iipH induced by a decline of electrical potential. Such a condition was obtained by the addition of Nig. or NHi Cl. The result was shown in Fig.5. Nigericin, at such concentration that electron transport is uncoupled from phosphorylation, enhanced the light-induced swelling of thylakoid membrane significantly. This effect was inhibited by Val. It could be deduced that in addition to the H accumulated inside the thylakoid membranes enhanced by decline of electrical potential, electrostatic repulsion between membranes... 

FIGURE 2. Effect of light and dark on the time dependent accumulation of TPMP (+TPB ) and Rb by wheat protoplasts (a) and their effect on mitochondrial and chloroplast membrane potentials, derived from Equation 1 (b). 

Similarly, addition of TNBT in the absence of O2 has no effect on the light-induced carotenoTd band shift (compare traces IC and the control experiment IB), a direct measure of the membrane potential (C. Wraight et al., 1978). Only, if TNBT addition is done in presence of O2, a marked difference in the shape of the light-induced change is observed, even if the sample has been made anaerobic afterwards (IE). 

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