Action of sodium diethyldithiocarbamate (NaDDC) on the HILL activity and chlorophyll fluorescence in Anacystis nidulans IU 625

Abstract

AbstractEffect of sodium diethyldithiocarbamate (NaDDC) on chlorophyll fluorescence and HILL activity in Anacystis cells exhibited stimulation of both the processes in a concentration‐dependent manner (SINGH et al. 1989). Treatment of cells with sodium dodecyl sulphate (1% w/v) and tris (0.5 M) resulted into further stimulation of NaDDC supported both fluorescence emission and HILL activity. Addition of energy consuming substrates like NaHCO3 (3 mM) and 3‐phosphoglyceric acid (PGA 1 mM) could bring about quenching of NaDDC stimulated fluorescence. However, fluorescence quenching of carbon substrates could be reversed in presence of DCMU (10 mM). Further, the results on cytochrome‐c reduction, fluorescence emission and pigment absorption in the presence of NaDDC exhibited a pH dependence (6–8) of NaDDC on these processes with maximum effect at pH 6. NaDDC‐induced general increase in the absorbance of pigments accompanied by hypsochromic shifts at 680 and 625 nm were indicative of conformational changes in the pigment protein complexes. The results with energy transfer inhibitors showed that uncouplers like FCCP (10 μM), Nigericin (10 μM) and NH4Cl (1 mM) could significantly alter the effect of NaDDC on fluorescence emission and HILL activity, while antimycin (5 μg/ml) and N‐ethylamaleimide (100 mM) had little effect. These results, taken together, suggested that NaDDC‐induced build up of proton gradient might be resulting into cessation of electron transport and stimulation of fluorescence by exerting a back pressure on the charge separation property of membrane.