Acta Biochimica et Biophysica 16. (1981)
1981 / 3-4. szám - Proceedings of the Eleventh Conference on Biophysics. Abstracts
Proceedings of the 11th Conference of Biophysics 235 Localization of Hydrogenase in the Photosynthetic Membrane of Thiocapsa roseopersicina Cs. Bagyinka, K. L. Kovács, E. Rak Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences, Szeged and Sinisa Stankovic Biological Center, Beograd, Yugoslavia Thiocapsa roseopersicina, a purple sulphur phototrophic bacterium displays reversible hydrogenase activity in vivo, i.e. it catalyzes the reaction: 2 e~ + 2H+ ^ H2 In the presence of artificial electron donors [methyl-(MV+)- or benzyl-viologen (BV+) reduced by dithionite] the cells produce molecular hydrogen, while H2 consumption takes place in the presence of H2 and oxidized viologens. Protoplasts also show hydrogenase activity of the same magnitude. When protoplasts are disrupted by osmotic shock the activity is found in the sediments of the membrane fraction; therefore, the enzyme is considered to be membrane-bound. The membrane of the bacterium is impermeable for oxidized redox dyes (MV2+, BV2+) while the reduced forms (MV+, BV+) easily penetrate the cells. Exploiting this permeability difference the location of the hydrogenase within the membrane has been determined from H2 uptake measurements. The results confirm that the enzyme is plasma membrane bound, and reveal that its active centre is at the outer surface of the plasma membrane. The Microsecond Delayed Fluorescence of the Second Photochemical System of Photosynthesis G. Laczkó, P. Maróti, A. Ringler, L. Szalay institute of Biophysics, József Attila University, Szeged The delayed fluorescence of dark adapted, intact and chemically treated Chlorella algae was measured at room temperature with a nitrogen laser phosphoroscope in the microsecond time range using photon counting technique and electronically gated photomultiplier. The maximum time resolution and the dead time of the equipment were 4 gs. For chemical treatment 3-(3,4-dichlorophenyl)-1,1-dimethylurea and NH2OH were used. The multiphasic decay of the delayed fluorescence could be explained by Delrieu’s parallel, heterogeneous reaction centre model of the second photochemical system of photosynthesis. Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 16, 1981