Recognition of 2′-hydroxyl groups by Escherichia coli ribonuclease HI

AbstractIn order to investigate the hydrogen-bonding interactions between Escherichia coli ribonuclease HI and the 2′-hydroxyl functions of the substrate, oligonucleotide duplexes containing 2′-amino-2′-deoxyuridine or 2′-fluoro-2′-deoxyuridine at a specific site were used, and their affinities for the enzyme were determined by kinetic analyses. The results indicate that the hydroxyl groups of the nucleoside 3′-adjacent to the cleaved phosphodiester linkage and the second nucleoside 5′ to the cleaved phosphodiester act as both a proton donor and an acceptor and as a proton acceptor, respectively, in the enzyme-substrate complex. A molecular model was constructed using the interactions derived from the results

Tissue-Restricted Expression of Nrf2 and Its Target Genes in Zebrafish with Gene-Specific Variations in the Induction Profiles

The Keap1-Nrf2 system serves as a defense mechanism against oxidative stress and electrophilic toxicants by inducing more than one hundred cytoprotective proteins, including antioxidants and phase 2 detoxifying enzymes. Since induction profiles of Nrf2 target genes have been studied exclusively in cultured cells, and not in animal models, their tissue-specificity has not been well characterized. In this paper, we examined and compared the tissue-specific expression of several Nrf2 target genes in zebrafish larvae by whole-mount in situ hybridization (WISH). Seven zebrafish genes (gstp1, mgst3b, prdx1, frrs1c, fthl, gclc and hmox1a) suitable for WISH analysis were selected from candidates for Nrf2 targets identified by microarray analysis. Tissue-restricted induction was observed in the nose, gill, and/or liver for all seven genes in response to Nrf2-activating compounds, diethylmaleate (DEM) and sulforaphane. The Nrf2 gene itself was dominantly expressed in these three tissues, implying that tissue-restricted induction of Nrf2 target genes is defined by tissue-specific expression of Nrf2. Interestingly, the induction of frrs1c and gclc in liver and nose, respectively, was quite low and that of hmox1a was restricted in the liver. These results indicate the existence of gene-specific variations in the tissue specificity, which can be controlled by factors other than Nrf2

Synthesis of chiral N-trifluoroacetyl-methionine derivatives and applying them as acyl donors for Friedel-Crafts acylation

A chiral N-protected α-amino acid N-hydroxysuccinimide ester (OSu) is a common useful reagent for peptide bond formation. Recently, N-trifluoroacetyl (TFA) α-amino acid OSu esters have been reported as acyl donors for Frieldel–Crafts reactions to synthesize chiral α-amino phenyl ketones retaining the configurations of the starting α-amino acids. There are few reports for chiral TFA protected methionine, which has methylthioethyl structure in the side-chain of the α-amino acid. The detailed synthesis of chiral TFA-Met-OSu and its application as an acyl donor for Friedel–Crafts acylation is reported

Optimization of sucrose 1’-position modification with 3-(trifluoromethyl)diazirinyl benzylbromide derivatives for photoaffinity labeling

Sucrose is well known as naturally occurring sweeteners. Photoreactive sucrose derivative containing 3-(trifluoromethyl) diazirinyl moiety is designed for photoaffinity labeling. As 1'-hydroxyl group of sucrose is well known to be less reactive than other primary alcohols, the optimization of reaction conditions for diazirinyl benzyl bromide derivative at sucrose 1'-postion was examined to elucidate the functional analysis of sweet receptors