Complexation of aluminum with DNA.

The extent of complexation of aluminum(III) with DNA (Calf thymus, Sigma type I) was estimated by means of two experimental techniques: potentiometric titration with a fluoride selective indicator electrode and dialysis followed by aluminum determination by graphite furnace AAS. Both types of experiments indicate that aluminum(III) is bound to DNA. The data are treated by assuming an ion exchange reaction with the phosphate diester groups. Using Rt to denote the concentration of these groups the values of log [AlMn-3R]/(Rt-3[AlMn-3R])[Al3+] decrease from approx. 7.6 to 5.6 when the concentration of sodium chloride is increased from 1 to 100 mM. In the pH range 4.5-5.5 the ion exchange constant increases approximately 0.5 log units. Dialysis gives lower values for the complex formation constant than potentiometry

The effect of the Siberian tundra on the environment of the shelf seas and the Arctic Ocean

The Tundra Ecology -94 expedition investigated inflow of inorganic and organic carbon to the shelf seas by river runoff, and its transformation by biochemical processes in seawater and sediment. In addition, anthropogenic radionuclides, 137Cs, 90Sr, and 239,240Pu, were studied in water and sediments. The distribution of dissolved inorganic carbon indicates that the majority of the Ob and Yenisey discharges flow into the Laptev Sea before entering the central Arctic Ocean. The sediment study shows that there is a marked difference in benthic oxygen uptake, efflux of dissolved inorganic carbon and nutrients between localities. 137Cs activity from the Chernobyl accident is 30% in the Barents, Kara, and Laptev Seas. 137Cs increased from 5-8 Bq m-3 in Barents Sea, 5-13 Bq m-3 in the Kara Sea to 8-15 Bq m-3 in the Laptev Sea, but with locally low concentrations at the river mouths. Corresponding values for 90Sr were 2.5, 3, and 4 Bq m-3, respectively