Arbuscular mycorrhizal fungi modify nutrient allocation and composition in wheat (Triticum aestivum L.) subjected to heat-stress

Plant and Soil - Livestock grazing is a widely practiced land-use regime that can impose lingering effects on global biogeochemical cycles. However, elucidating the mechanisms of related...     

The steric effect of the leaving group in the α-chymotrypsin-catalyzed hydrolysis of acetyl-l-phenylalanine p-alkoxycarbonyl anilides

The relative rate of the α-chymotrypsin-catalyzed hydrolysis of acetyl-l-phenylalanine p-alkoxycarbonyl anilides tends to a maximum with the increase of the leaving group bulkiness. This rate enhancement specificity appears to be entropy controlled: the bulky p-alkoxycarbonyl groups increase both enthalpy and entropy of activation. These kinetic and thermodynamic data are interpreted in terms of the stereoelectronic theory for the formation and cleavage of the tetrahedral intermediate in acyl-transfer reactions; the bulky p-alkoxycarbonyl groups favor the formation of a reactive conformation of the enzyme tetrahedral intermediate.     

Modifications on the heterocyclic base of ganciclovir,penciclovir, acyclovir - syntheses and antiviral properties

АBSTRACT

Esters of the antiherpetic drugs ganciclovir, penciclovir with the bile acids (cholic, chenodeoxycholic and deoxycholic) and amino acid esters of acyclovir were generated and evaluated for their in vitro antiviral activity against herpes simplex viruses type 1 and type 2 (HSV-1, HSV-2). The antiviral assays demonstrated that modified analogs of ACV and PCV are less active compared to the initial substances against HSV-1and HSV-2. CC50 for ganciclovir-deoxycholate corresponded to the CC50 of the other analogs and its activity is lower than ganciclovir. Obtained results show that tested modification do not improve bioavailability of nucleoside analogs in cells.     

Syntheses of some purine nucleosides by the fusion method,by the condensation of acetylated chlorides,and from 1-acetates in the presence of titanium tetrachloride: a comparison

9-(2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-d-glucopyranosyl)-6-benzamidopurine (9) and 6-benzamido-9-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)purine (11) have been prepared by three synthetic routes: (a) the fusion procedure, (b) direct condensation of 6-benzamido(chloromercuri)purine with the acetylated chloride, or (c) with the chloride formed in situ from the 1-acetate in the presence of titanium tetrachloride. The results obtained are briefly discussed; the direct condensation of the mercuri salt with chlorides proved to be the most convenient.Whereas, in the condensation with acetylated chlorides, only products having the β-d anomeric configuration were isolated, the chloride protected with non-participating groups (benzyl) afforded both anomers. The removal of the benzyl groups should be preceded by hydrolytic cleavage of the benzamido group. A simple procedure for fractionation, on small columns of silica gel, of reaction mixtures obtained in the fusion reactions is described.     

Persistence and in vivo effects of Yersinia enterocolitica 0:3 endotoxin in rats

In vivo effects of Yersinia enterocolitica 0:3 lipopolysaccharide (prepared from bacteria grown at 25 degrees C and 37 degrees C) were investigated after intraperitoneal (i.p.) and intraarticular (i.a.) injection in rats during 30 days of examination. The persistence of endotoxin in the peritoneal and the synovial cavities was demonstrated by the immunofluorescence technique. Peritoneal and synovial exudative cell infiltration, as well as changes in some parameters (glycolytic and acid phosphatase activity, and killing ability of peritoneal cells; lactate dehydrogenase concentration in synovial fluid) were studied. The results indicated that endotoxin could persist longer in the synovial than in the peritoneal cavity.     

Earthquakes site effects modeling by hybrid MS-BIEM: the case study of Sofia, Bulgaria

The study solves 2D elastodynamic model for seismic in-plane wave propagation in laterally inhomogeneous geological profiles situated in a vertically inhomogeneous half-space with a seismic source. For the aim, an efficient hybrid Modal Summation-Boundary Integral Equation Method (MSM-BIEM) is applied. The MSM is used as a tool for the simulation of wave propagation from the source position to the local multilayered laterally inhomogeneous geological profile, where the BIEM is applied. The BIEM is based on the frequency-dependent fundamental solution of the governing equation in elastodynamics and the hybrid method works in the frequency domain. The inverse FFT solution is applied to obtain time histories. The hybrid tool is applied to several models for the investigation of local site effects due to: (a) the impedance contrasts between soil layers, (b) surface topography and lateral inhomogeneity, (c) the seismic source properties and (d) the existence of water saturation in soils. The application of the modeling tool is a contribution to the seismic risk analysis of Sofia city.