Evidence for the Reversible Acylation of Elastases by Monocyclic g-Lactams

The reaction of a monocyclic gamma-lactam with the serine protease elastase occurs via reversible formation of a hydrolytically labile acyl-enzyme complex; in contrast analogous beta-lactam inhibitors irreversibly react to form a relatively stable acyl-enzyme complex. (C) 1997 Elsevier Science Ltd.</p

Evidence for the Reversible Acylation of Elastases by Monocyclic g-Lactams

The reaction of a monocyclic gamma-lactam with the serine protease elastase occurs via reversible formation of a hydrolytically labile acyl-enzyme complex; in contrast analogous beta-lactam inhibitors irreversibly react to form a relatively stable acyl-enzyme complex. (C) 1997 Elsevier Science Ltd.</p

Climate and environment during the Younger Dryas (GS-1) as reflected by composite stable isotope records of lacustrine carbonates at Torreberga, southern Sweden

Climatic and environmental changes during the Younger Dryas stadial (GS-1) and preceding and following transitions are inferred from stable carbon and oxygen isotope records obtained from the sediments of ancient Lake Torreberga, southern Sweden. Event GS-1 is represented in the sediment sequence by 3.5 m of clay containing lacustrine carbonates of various origins. Comparison of isotopic records obtained on mollusc shells, ostracod valves, and Chara encrustations precipitated during specific seasons of the year supports estimates of relative changes in both lake water and mean annual air temperatures. Variations in soil erosion rates can also be estimated from a simple isotope-mass-balance model to separate allochthonous and autochthonous carbonate contributions to the bulk carbonate content of the sediments. The well-known, rapid climatic shifts characterising the Last Termination in the North Atlantic region are clearly reflected in the isotopic data, as well as longer-term changes within GS-1. Following maximum cooling shortly after the Allerod-Younger Dryas (GI-1-GS-1) transition, a progressive warming and a slight increase in aquatic productivity is indicated. At the Younger Dryas-Preboreal (GS-1-PB) transition mean annual air temperature rapidly increased by more than 5 degrees C and summer lake-water temperature increased by ca. 12 degrees C. The subsequent Preboreal oscillation is characterised by an increase in soil erosion and a slight decrease in mean annual air temperature. These results are in harmony with recent findings about large-scale climate dynamics during the Last Termination. Copyright (C) 1999 John Wiley & Sons, Ltd

Holocene treeline history and climate change across northern Eurasia

Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia), Boreal forest development in this region commenced by 10,000 yr B.P, Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern Russia, Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5 degrees to 7.0 degrees C warmer than modern. The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation, (C) 2000 University of Washington