Electrochromism of chlorophylls and carotenoids in multilayers and in chloroplasts

Electrical evidence for the field indicating absorption change in bioenergetic membranes

“…(i) the kinetics of the potential changes perpendicular to bioenergetic membranes can be measured under the outlined conditions electrically by electrodes; (ii) the agreement with the kinetics of the 'field indicating absorption changes' provides further support that these changes are indicating electrical potentials; (iii) the proportionality between the electrical signal and the electrochromic changes confirms our earlier conclusion that A¢ is indicated linearly by the optical changes [7]. (iv) Because the electrodes respond only to potentials perpendicular to the membrane the agreement excludes the possibility that the field indicating absorption changes respond to fields adjusted only in the plane of the membrane.…”

“…The generation of an electrical field across the membrane of bioenergetic systems as in green plants and bacteria has beerL demonstrated since 1967 by the shift of absorption bands of membrane pigments in the field (electrochromism) [1][2][3][4][5][6][7][8]. Such shifts cause absorption changes of all the bulk pigments incorporated in the membrane (chlorophyll-a, -b and carotenoids) [4,7,8].…”

“…Such shifts cause absorption changes of all the bulk pigments incorporated in the membrane (chlorophyll-a, -b and carotenoids) [4,7,8]. The rise of these so-called 'field indicating absorption changes' takes place in < 20 nsec [5].…”

“…(b) The spectra of the field indicating absorption changes of chloroplasts and bacteria correspond to the spectrum of electrochromic changes of multilayers of chlorophyll-a, -b and carotenoids which have been exposed between two electrodes to field up to 106V/cm [7,8].…”

Location of field‐sensitive carotenoid molecules in the chloroplast membrane. Arguments from low‐temperature studies

“…One of them, whose duration is in the millisecond time range, has been well characterized and attributed to a light-induced electric field acting on the photosynthetic pigments [ 1,2]. It has been proposed that the main part of the absorption change at 520 nm is due to an electrochromic effect on carotenoid molecules [3] , an hypothesis which is well supported by theoretical evaluations [4]. Schiephake et al showed that both System-l and System-2 photoreactions contribute equally to the carotenoid shift, in chloroplasts at physiological temperatures [5].…”