Synthesis and Biological Activity of Sugar-Fluorinated 2′,3′-dideoxy-4′-thioribofuranosyl Nucleosides

Abstract

The efficient DAST fluorination of deoxy-4′-thiopyrimidine nucleosides is reported. The cytidine analogue 3b was marginally effective against HIV.     

Genome sequence of the clover-nodulating Rhizobium leguminosarum bv. trifolii strain TA1

Rhizobium leguminosarum bv. trifolii strain TA1 is an aerobic, motile, Gram-negative, non-spore-forming rod that is an effective nitrogen fixing microsymbiont on the perennial clovers originating from Europe and the Mediterranean basin. TA1 however is ineffective with many annual and perennial clovers originating from Africa and America. Here we describe the features of R. leguminosarum bv. trifolii strain TA1, together with genome sequence information and annotation. The 8,618,824 bp high-quality-draft genome is arranged in a 6 scaffold of 32 contigs, contains 8,493 protein-coding genes and 83 RNA-only encoding genes, and is one of 20 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Community Sequencing Program.     

Genome Analysis and Physiological Comparison of Alicycliphilus denitrificans Strains BC and K601T

The genomes of the Betaproteobacteria Alicycliphilus denitrificans strains BC and K601^T have been sequenced to get insight into the physiology of the two strains. Strain BC degrades benzene with chlorate as electron acceptor. The cyclohexanol-degrading denitrifying strain K601^T is not able to use chlorate as electron acceptor, while strain BC cannot degrade cyclohexanol. The 16S rRNA sequences of strains BC and K601^T are identical and the fatty acid methyl ester patterns of the strains are similar. Basic Local Alignment Search Tool (BLAST) analysis of predicted open reading frames of both strains showed most hits with Acidovorax sp. JS42, a bacterium that degrades nitro-aromatics. The genomes include strain-specific plasmids (pAlide201 in strain K601^T and pAlide01 and pAlide02 in strain BC). Key genes of chlorate reduction in strain BC were located on a 120 kb megaplasmid (pAlide01), which was absent in strain K601^T. Genes involved in cyclohexanol degradation were only found in strain K601^T. Benzene and toluene are degraded via oxygenase-mediated pathways in both strains. Genes involved in the meta-cleavage pathway of catechol are present in the genomes of both strains. Strain BC also contains all genes of the ortho-cleavage pathway. The large number of mono- and dioxygenase genes in the genomes suggests that the two strains have a broader substrate range than known thus far.     

Sexual Dimorphism in Juvenile Hormone Synthesis by Corpora Allata and in Juvenile Hormone Acid Methyltransferase Activity in Corpora Allata and Accessory Sex Glands of Some Lepidoptera

Summary

The kinetic profiles of vitellin accumulation in the oyster ovary during oocyte growth and the effects in vivo and in vitro of estradiol-17β (E₂) on vitellin formation were examined in this study. The relative vitellin content measured by an enzyme-linked immunosorbent assay (ELISA) shows an apparent increase as the oocyte develops. Immunoblotting of the vitellin using anti-vitellin indicated that two main bands (179 and 110 kD), which begin to accumulate at an early stage of maturation, become pronounced during oocyte growth. Meanwhile, the major peak of the intact form of vitellin (530 kD) in gel filtration also enlarges with oocyte growth, supporting the results of immunoblot analysis and vitellin determination. E₂ treatment in vivo causes significant increases in oocyte diameter and vitellin content in the female oyster. A similar trend was observed in ovarian tissues cultured in the presence of E₂. It is concluded that E₂ is one of the major factors which control the vitellogenesis in the oyster and that the ovary is undoubtedly the site of synthesis of vitellin.     

Pollution in mediterranean-climate rivers

This review examines information generated over the past decade on the pollution of rivers in regions with a mediterranean-type climate (med-climate). Pollution has clearly increased in the last 100 years and is correlated with the development of industry, agriculture and human population. Important efforts have been made in some med-climate countries in order to characterise the chemical status of rivers. In addition, the number of chemical substances detectable in mediterranean-climate rivers (med-rivers), as well as the limits of detection, have improved from the development of better analytical methods. New substances detected in rivers are gaining attention. We discuss available knowledge regarding real and potential effects of pollutants on the biota and ecosystems in med-rivers, taking into account natural environmental characteristics of these rivers. The extreme seasonal conditions in med-rivers add to the potential risk because these characteristics can enhance pollutant effects. Efforts and policies to prevent or reduce pollution effects on med-rivers are linked to the knowledge about pollution pressures associated with the degree of economic development. Aquatic communities in med-rivers are more sensitive to pollutants because they are exposed to strong natural and human stressors.     

Evaluation of Animal Genetic and Physiological Factors That Affect the Prevalence of Escherichia coli O157 in Cattle

Controlling the prevalence of Escherichia coli O157 in cattle at the pre-harvest level is critical to reduce outbreaks of this pathogen in humans. Multilayers of factors including the environmental and bacterial factors modulate the colonization and persistence of E. coli O157 in cattle that serve as a reservoir of this pathogen. Here, we report animal factors contributing to the prevalence of E. coli O157 in cattle. We observe the lowest number of E. coli O157 in Brahman breed when compared with other crosses in an Angus-Brahman multibreed herd, and bulls excrete more E. coli O157 than steers in the pens where cattle were housed together. The presence of super-shedders, cattle excreting >10⁵ CFU/rectal anal swab, increases the concentration of E. coli O157 in the pens; thereby super-shedders enhance transmission of this pathogen among cattle. Molecular subtyping analysis reveal only one subtype of E. coli O157 in the multibreed herd, indicating the variance in the levels of E. coli O157 in cattle is influenced by animal factors. Furthermore, strain tracking after relocation of the cattle to a commercial feedlot reveals farm-to-farm transmission of E. coli O157, likely via super-shedders. Our results reveal high risk factors in the prevalence of E. coli O157 in cattle whereby animal genetic and physiological factors influence whether this pathogen can persist in cattle at high concentration, providing insights to intervene this pathogen at the pre-harvest level.     

Enzymatic properties of the lactate dehydrogenase enzyme from Plasmodium falciparum

The lactate dehydrogenase enzyme from Plasmodium falciparum (PfLDH) is a target for antimalarial compounds owing to structural and functional differences from the human isozymes. The plasmodial enzyme possesses a five-residue insertion in the substrate-specificity loop and exhibits less marked substrate inhibition than its mammalian counterparts. Here we provide a comprehensive kinetic analysis of the enzyme by steady-state and transient kinetic methods. The mechanism deduced by product inhibition studies proves that PfLDH shares a common mechanism with the human LDHs, that of an ordered sequential bireactant system with coenzyme binding first. Transient kinetic analysis reveals that the major rate-limiting step is the closure of the substrate-specificity loop prior to hydride transfer, in line with other LDHs. The five-residue insertion in this loop markedly increases substrate specificity compared with the human muscle and heart isoforms.     

A survey of the year 2003 literature on applications of isothermal titration calorimetry

Over the last decade isothermal titration calorimetry (ITC) has developed from a specialist method which was largely restricted in its use to dedicated experts, to a major, commercially available tool in the arsenal directed at understanding molecular interactions. The number of those proficient in this field has multiplied dramatically, as has the range of experiments to which this method has been applied. This has led to an overwhelming amount of new data and novel applications to be assessed. With the increasing number of publications in this field comes a need to highlight works of interest and impact. In this overview of the literature we have attempted to draw attention to papers and issues for which both the experienced calorimetrist and the interested dilettante hopefully will share our enthusiasm.