Sulfate assimilation in higher plants. Characterization of a stable intermediate in the adenosine 5′-phosphosulfate reductase reaction

The enzyme catalysing the reduction of adenosine 5′-phosphosulfate (AdoPS) to sulfite in higher plants, AdoPS reductase, is considered to be the key enzyme of assimilatory sulfate reduction. In order to address its reaction mechanism, the APR2 isoform of this enzyme from Arabidopsis thaliana was overexpressed in Escherichia coli and purified to homogeneity. Incubation of the enzyme with [35S]AdoPS at 4 °C resulted in radioactive labelling of the protein. Analysis of APR2 tryptic peptides revealed 35SO2–3 bound to Cys248, the only Cys conserved between AdoPS and prokaryotic phosphoadenosine 5′-phosphosulfate reductases. Consistent with this result, radioactivity could be released from the protein by incubation with thiols, inorganic sulfide and sulfite. The intermediate remained stable, however, after incubation with sulfate, oxidized glutathione or AdoPS. Because truncated APR2, missing the thioredoxin-like C-terminal part, could be labelled even at 37 °C, and because this intermediate was more stable than the complete protein, we conclude that the thioredoxin-like domain was required to release the bound SO2–3 from the intermediate. Taken together, these results demonstrate for the first time the binding of 35SO2–3 from [35S]AdoPS to AdoPS reductase and its subsequent release, and thus contribute to our understanding of the molecular mechanism of AdoPS reduction in plants.

(Table 1) Sea-surface temperatures, intermediate-water temperatures, and latitudinal gradient at three time slices at the end of the Cretaceous

Climatic and oceanographic variations during the last 2 m.y. of the Maastrichtian inferred from high-resolution (10 k.y.) stable isotope analysis of the mid-latitude South Atlantic Deep Sea Drilling Project Site 525 reveal a major warm pulse followed by rapid cooling prior to the Cretaceous-Tertiary boundary. Between 66.85 and 65.52 Ma, cool but fluctuating temperatures average 9.9 and 15.4°C in intermediate and surface waters, respectively. This interval is followed by an abrupt short-term warming between 65.45 and 65.11 Ma, which increased temperatures by 2-3°C in intermediate waters, and decreased the vertical thermal gradient to an average of 2.7°C. This warm pulse may be linked to increased atmospheric pCO2, increased poleward heat transport, and the switch of an intermediate water source from high to low-middle latitudes. During the last 100 k.y. of the Maastrichtian, intermediate and surface temperatures decreased by an average of 2.1 and 1.4°C, respectively, compared to the maximum temperature between 65.32 and 65.24 Ma.

Composition of particulate lipids in the intermediate zone between the Kara and Laptev Seas

Chemical group composition of particulate lipids from the intermediate zone between the Kara and Laptev Seas is studied by thin-layer chromatography with flame ionization detection (IATROSCAN TH-10). Hydrocarbons and complex polar lipids similar to those found in the previously studied southeastern area of the Kara Sea are basic components of particulate lipids. High content of triglycerides in the upper layers of the water mass north of the Severnaya Zemlya Islands is a characteristic feature of group composition of particulate lipids. Distribution of triglycerides correlates with localization of the ice cover boundary and complies with process of phytoplankton blooming in the ice edge zone. Distribution of lipid concentration depends on water stratification in the intermediate zone between the Kara and Laptev Seas.

Table 6 Generalised properties of Utsira caprocks, based on analysis of cuttings (page 79)

Executive Summary: Carbon dioxide capture and storage (CCS) is one option for mitigating atmospheric emissions of carbon dioxide and thereby contributes in actions for stabilization of atmospheric greenhouse gas concentrations. The Bellona Foundation is striving to achieve wide implementation of carbon dioxide (CO2) capture and storage both in Norway and internationally. Bellona considers CCS as the only viable large scale option to close the gap between energy production and demand in an environmentally sound way, thereby ensuring that climate changes and acidification of the oceans due to increased CO2 concentrations in the atmosphere will be stabilised. ff