Probing the MVAI methyltransferase region that interacts with DNA: affinity labeling with the dialdehyde-containing DNA duplexes

Affinity labeling of methyltransferase MvaI by DNA duplexes containing oxidized 2'-O-beta-D-ribofuranosylcytidine or 1-beta-D-galactopyranosyl)thymine residues was performed. Partial chemical hydrolysis of the covalently bound methylase in the conjugates with the dialdehyde-containing DNA allowed us to determine the amino acid region in the C terminus of methylase MvaI that interacts with DNA.     

Intracellular Alginolytic Enzymes of the Marine Bacterium Pseudoalteromonas citrea KMM 3297

The marine bacterium Pseudoalteromonas citrea KMM 3297 is an associate of the holothurian Apostichopus japonicus. When grown in a medium containing glucose, the strain produces two intracellular alginolytic enzymes, AlI and AlII. Fucoidan from the brown alga Fucus evanescens induces synthesis of one more alginolytic enzyme, AlIII. These enzymes were separated using anion-exchange chromatography. The alginate lyase AlI completely retains its activity at 35 degrees C, AlII and AlIII being stable at 45 degrees C. The alginate lyases exhibit maximal activities in the range of pH 7-8. The molecular weights of AlI, AlII, and AlIII determined by gel filtration are 25, 79, and 61 kD, respectively. All the investigated enzymes are endo-type alginate lyases. They catalyze degradation of polyguluronate (poly-G) and polymannuronate (poly-M) yielding oligosaccharides of the polymerization degree of 5 > or = n > or = 3 with the unsaturated bond between the C4 and C5 atoms of the non-reducing terminus. A mixture of these three enzymes exhibits synergism while acting on the polymeric substrate. The Km values of the alginate lyase AlI for poly-G and poly-M are 24 and 34 micro g/ml, respectively. Alginate lyase AlIII exhibits less affinity to poly-M (Km = 130.0 microg/ml) than to poly-G (Km = 40.0 microg/ml). NaCl (0.2 M), MgCl2 and MgSO4 (0.01 M) activate all three enzymes more than twofold. The presence of several alginolytic enzymes of different specificity provides efficient destruction of alginic acids of brown algae by the strain P. citrea KMM 3297.     

Generation of hard X-ray emission by the electron beam in plasma focus facilities

The results of measurements of the temporal characteristics of hard X-ray emission generated at plasma focus (PF) facilities are presented. Mechanisms of electron beam generation in the PF pinch are analyzed. On the basis of the known mechanisms and experimental data on the measured temporal characteristics of hard X-ray pulses, a mechanism of fast electron generation that takes into account both the effect of the anomalous pinch resistance and the current redistribution in the near-pinch region is proposed. The processes occurring in the pinch plasma are simulated on the basis of the proposed mechanism by using the MicroCap code. It is shown that only a small fraction of the discharge current (1–10%) can be transformed into the electron beam current.     

Carbon accumulation in soils of forest and bog ecosystems of southern Valdai in the Holocene

Carbon stocks and accumulation rates in humus and peat horizons of the contiguous soil series of forest and bog ecosystems have been studied in the Central Forest State Biosphere Reserve, Tver Region. Upland soil types (soddy podzolic, brown, and white podzolic) have been compared to paludified (peat-enriched gley podzolic and peaty gley) and bog soils differing in trophic status, including those of upland, transitional, and lowland bogs. The results show that carbon stocks in mineral soils are many times smaller than in waterlogged soils and an order of magnitude smaller than in bog soils. Mineral and bog soils are characterized by similar rates of carbon accumulation averaged over the entire period of their existence. The highest rate of carbon accumulation has been noted for the soils of waterlogged habitats, although this process may be periodically disturbed by fires and other stress influences.     

Near-magnetic-axis geometry of a closely quasi-isodynamic stellarator

It is shown that the condition of stationary second adiabatic invariant at the magnetic axis of a stellarator configuration can be satisfied to good accuracy for all reflected particles.     

Oligodeoxyribonucleosides Containing 1-β-D-Glucopyranosylthymine Synthesis and Substrate Properties

Abstract

Regioselective method for 1-β-D-glucopyranosylthymine incorporation into oligonucleotides has been developed and substrate properties of the latters in DNA synthesis and hydrolysis reactions were investigated.