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Proximate composition, selected mineral (Zn, Fe, Cd, As, Hg, Pb, Ni, Cu) content and fatty acid profiles were determined in some widely consumed fish species obtained from the Black Sea. All fish species analysed individually were fairly high in protein (14·1–25·1%) and lipid (7·4–18·4%). Moisture and ash content varied within a narrow range. The mineral content was highly variable. The most abundant microelements in fish were Zn and Fe followed by Cu, and the remaining elements were present in amounts below toxic levels. Eight fatty acids (16: 0, 16:1, n‐7, 18: 0, 18:1 n‐9, 18: 2 n‐6, 20:1 n‐9, 20: 5 n‐3, 22: 6 n‐3) represented more than 60% of the fatty acid content. Saturated fatty acids ranged from 25·8 to 45·1%. Anchovy and whiting contained almost 35% of polyunsaturated fatty acids. The percentage of docosahexaenoic acid (DHA) exceeded that of eicosapentaenoic acid (EPA) in almost all the fish species examined, and the actual content of these acids has shown that sprat, whiting, garfish, red mullet, shad and sea bream provide the recommended daily intake of 1 g of EPA+DHA with reasonable amounts of fillet. These results indicate that biological differences existing in fish species can influence the values to be set for the standards and composition. © 1998 Society of Chemical Industry.

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Novel homodinuclear Cu(II) (K1), heterodinuclear Cu(II)-Mn(II) (K2) and homotrinuclear Cu(II) (K3) complexes with a novel oxime-type ligand have been prepared and their nucleolytic activities on pCYTEXP were established by neutral agarose gel electrophoresis. The analyses of the cleavage products obtained electrophoretically indicate that although the examined complexes induces very similar conformational changes on supercoiled DNA by converting supercoiled form to nicked form than linear form in a sequential manner as the complex concentration or reaction period is increased, K3 is less effective than the two others. The oxime complexes were nucleolytically active at physiological pH values but the activities of Kl or K2 were diminished by increasing the pH of the reaction mixture. In contrast, K3 makes dominantly single strand nicking by producing nicked circles on DNA at almost all the applied pH values. Metal complex induced DNA cleavage was also tested for inhibition by various radical scavengers as superoxide dismutase (SOD), azide, thiourea and potassium iodide. The antioxidants inhibited the nucleolytic acitivities of the oxime complexes but SOD afforded no protection indicating that the nucleolytic mechanism involves of copper and/or manganese complex-mediated reactive oxygen species such as hydroxyl radicals being responsible for the oxidative DNA cleavage.

The rates of electron transfer from a ubiquinol analogue to cytochrome c2 catalyzed by the cytochrome bc1 complexes of Rhodobacter capsulatus and Rhodopseudomonas viridis were measured as a function of ionic strength. The effects of ionic strength on the kinetic parameters for the reactions are consistent with a role for electrostatic complex formation between cytochrome c2 and the cytochrome bc1 complex in the electron-transfer pathways in both photosynthetic purple non-sulfur bacteria. Additional support for a docking model in which positively charged lysines on cytochrome c2 interact with negatively charged groups on the Rb. capsulatus cytochrome bc1 complex was obtained from kinetic experiments using Rb. capsulatus cytochrome c2 and equine cytochrome c in which specific lysine residues were altered by site-directed mutagenesis and chemical modification, respectively. Equine cytochrome c, which is a poor electron donor to the reaction center of Rps. viridis, is an effective electron acceptor for the Rps. viridis cytochrome bc1 complex. Chemical modification of lysine residues on Rps. viridis cytochrome c2 has a substantially greater effect on the reduction of the Rps. viridis reaction center by ferrocytochrome c2 than on the oxidation of the Rps. viridis cytochrome bc1 complex by ferricytochrome c2. These data suggest that the docking site for Rps. viridis cytochrome c2 on the Rps. viridis reaction center tetraheme subunit differs in structure from the docking site for the cytochrome on the Rps. viridis cytochrome bc1 complex to a significant extent. In this respect, Rps. viridis differs from photosynthetic purple non-sulfur bacteria in which the reaction center does not contain a tetraheme subunit, where the binding sites for cytochrome c2 on the reaction center and the cytochrome bc1 complex appear to be quite similar.