Characterization of the interactions of a bifunctional inhibitor with alpha-thrombin by molecular modelling and peptide synthesis.

A potent thrombin inhibitor, [D-Phe45, Arg47] hirudin 45-65, that contains an active site-directed sequence D-Phe-Pro-Arg-Pro, an exosite specific fragment hirudin 55-65 (H55-65) and a linker portion hirudin 49-54, was designed based on the hirudin sequence [DiMaio et al. (1990) J. Biol. Chem., 265, 21698-21798]. A three-dimensional model of the complex between the B-chain of human thrombin and the inhibitor [D-Phe45, Arg47] hirudin 45-65 was constructed using molecular modelling starting from the X-ray C alpha coordinates of the thrombin-hirudin complex and the NMR-derived structure of the thrombin-bound hirudin 55-65. The contribution of the H49-54 fragment to the thrombin-inhibitor interaction was deduced by examining a series of analogs containing single glycine substitution and analogs with reduced number of residues within the linker. The results were consistent with the molecular modelling observations i.e. the H49-54 fragment serves the role of a spacer in the binding interaction and could be replaced by four glycine residues. The studies on the interaction of the exosite-directed portion of the inhibitor with thrombin using a series of synthetic H55-65 analogs demonstrated that residues AspH55 to ProH60 play a major role in binding to human thrombin where the side chains of PheH56, IleH59 and GluH57 showed critical contributions. Molecular modelling suggested that these side chains may contribute to inter- and intramolecular hydrophobic and electrostatic interactions, respectively.     

Association between COMT SNP variation and timidity in Golden and Labrador Retrievers

Timidity in dogs is a trait with high heritability. However, the relevant genetic factors and markers associated with this condition are largely unknown. The function of the catechol‐O‐methyl transferase (COMT) gene has been found to be associated with human fearful or anxious emotions, and the COMT:p.Val158Met polymorphism locus is significantly related to anxious behavior. In the present study, the correlation between timidity and four single nucleotide polymorphism (SNP) variations (C.‐1666C>G c.39A>G, c.216G>A, c.482G>A) of the COMT gene was investigated in dogs. The evaluation was based on the dog courage assessment assay and a genotype and haplotype analysis in Labrador Retrievers (LR) and Golden Retrievers (GR). The principal components analysis factor structure of the courage phenotype was invariant between LR and GR. Sex, breed and age had no statistically significant effect on the timidity of the dogs. All SNP loci detected were in Hardy–Weinberg equilibrium. The c.39A>G locus was removed in the subsequent association analysis due to the significant difference between LR and GR in genotype distributions. Intriguingly, the genotypes and haplotypes of the COMT gene were significantly and highly correlated with the timidity of LR and GR. The A alleles of the COMT:c.216G>A and c.482G>A loci appeared to play a dominant role in the timid behavior of the dogs. This result supports and broadens the warrior/worrier hypothesis and will have important implications for the understanding of the evolution of temperament in dogs. Additionally, the results provide predictive genetic markers for temperament in dogs.     

Plasma control of the directional pattern of a multislot waveguide antenna

The possibility of controlling the directional pattern of a multislot waveguide antenna with the help of a gas-discharge tube placed inside the waveguide was studied experimentally. Since the dielectric parameters of the waveguide depend on the plasma density in the discharge column, they can be controlled by varying the discharge current. The high efficiency of such plasma control was demonstrated experimentally: as the discharge current was varied from 0 to 200 mA, the antenna directional pattern turned by ～17°.     

Transformation of Microbial Complexes in Components of Soil Constructions of Different Origin (Soil,Peat, Sand) during Freezing-thawing Processes

Microbiology - In a model experiment, the transformation of microbial complexes of cultivated saprotrophic bacteria and yeasts during freezing-thawing was studied in various natural substrates that...     

FBXO44 promotes DNA replication-coupled repetitive element silencing in cancer cells

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Naphthazarin derivatives (II): formation of glutathione conjugate, inhibition of DNA topoisomerase-I and cytotoxicity.

6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones, expressing a higher reactivity in conjugation with glutathione, showed a greater potency in the inhibition of DNA topoisomerase-I and the cytotoxicity against L1210 cells than 2-(1-hydroxyalkyl)-DMNQ derivatives, implying the participation of electrophilic arylation in the bioactivities. In further study 6-(1-Hydroxyalkyl)-5,8-dimethoxy-1,4-naphthoquinones with an alkyl group of shorter chain length (C2-C6) exerted a greater bioactivities than those with longer chain length(>C6).     

Tropane alkaloid production by Agrobacterium rhizogenes transformed hairy root cultures of Atropa baetica Willk. (Solanaceae)

Atropa baetica hairy root cultures were induced after infecting stem segments with Agrobacterium rhizogenes strain ATCC 15834. Accumulation of the tropane alkaloids atropine and scopolamine by hairy roots cultured in half- and full-strength Murashige and Skoog (MS) medium was high, although this was not growth associated. These alkaloids were also released into both liquid media. Higher tropane alkaloids present both in hairy roots and liquid medium occurred in half MS medium, showing a clear relationship between slow growth of cultures and higher product accumulation. The pH of both nutrient media varied as culture progressed, and seemed to be associated with the release of scopolamine. GC-MS analyses showed the presence of a new compound, namely tigloylpseudotropine; moreover, 3α-isobutyryloxytropane, formerly found only in plant leaf tissue, was also identified in the hairy roots. Received: 18 August 1997 / Revision received: 30 November 1997 / Accepted: 20 January 1998