Chalcogenidobis(ene-1,2-dithiolate)molybdenum(IV) complexes (chalcogenide E = O, S, Se): probing Mo≡E and ene-1,2-dithiolate substituent effects on geometric and electronic structure

New square-pyramidal bis(ene-1,2-dithiolate)MoSe complexes, [Mo(IV)Se(L)(2)](2-), have been synthesised along with their terminal sulfido analogues, [Mo(IV)S(L)(2)](2-), using alkyl (L(C(4)H(8))), phenyl (L(Ph)) and methyl carboxylate (L(COOMe)) substituted dithiolene ligands (L). These complexes now complete three sets of Mo(IV)O, Mo(IV)S and Mo(IV)Se species that are coordinated with identical ene-1,2-dithiolate ligands. The [alkyl substituted Mo(S/Se)(L(C(4)H(8)))(2)](2-) complexes were reported in prior investigations (H. Sugimoto, T. Sakurai, H. Miyake, K. Tanaka and H. Tsukube, Inorg. Chem. 2005, 44, 6927, H. Tano, R. Tajima, H. Miyake, S. Itoh and H. Sugimoto, Inorg. Chem. 2008, 47, 7465). The new series of complexes enable a systematic investigation of terminal chalcogenido and supporting ene-1,2-dithiolate ligand effects on geometric structure, electronic structure, and spectroscopic properties. X-ray crystallographic analysis of these (Et(4)N)(2)[MoEL(2)] (E = terminal chalocogenide) complexes reveals an isostructural Mo centre that adopts a distorted square pyramidal geometry. The M≡E bond distances observed in the crystal structures and the ν(M≡E) vibrational frequencies indicate that these bonds are weakened with an increase in L→Mo electron donation (L(COOMe) < L(Ph) < L(C(4)H(8))), and this order is confirmed by an electrochemical study of the complexes. The (77)Se NMR resonances in MoSeL complexes appear at lower magnetic fields as the selenido ion became less basic from MoSeL(C(4)H(8)), MoSeL(Ph) and MoSeL(COOMe). Electronic absorption and resonance Raman spectroscopies have been used to assign key ligand-field, MLCT, LMCT and intraligand CT bands in complexes that possess the L(COOMe) ligand. The presence of low-energy intraligand CT transition in these MoEL(COOMe) compounds directly probes the electron withdrawing nature of the -COOMe substituents, and this underscores the complex electronic structure of square pyramidal bis(ene-1,2-dithiolate)-Mo(IV) complexes that possess extended dithiolene conjugation.

In Situ Generation of Oxo−sulfidobis(dithiolene)tungsten(VI) Complexes: Active-Site Models for the Aldehyde Ferredoxin Oxidoreductase Family of Tungsten Enzymes

Oxo-sulfidobis(dithiolene)tungsten(VI) complexes were prepared in situ by the reaction of oxobis(dithiolene)tungsten(V) precursors with hydrosulfide (SH-). The complexes, characterized by UV-vis, electrospray ionization mass spectrometry, IR, and resonance Raman spectroscopies, model the proposed coordination environment and observed hydrolytic reactions of members of the aldehyde ferredoxin oxidoreductase family of tungsten enzymes.

Development of real-time detection direct test for hepatitis B virus and comparison with two commercial tests using the WHO international standard

AIMS

A highly reproducible and sensitive hepatitis B virus real-time detection direct (HBV RTD-direct) test using DNA extraction by magnetic beads coated with polyclonal anti-HBsAg, followed by the real-time detection polymerase chain reaction (PCR) method, was developed for the detection of HBV DNA.

METHODS

The HBV DNA could be extracted from the HBsAg positive viral particles without resulting in viral DNA fragmentation. The HBV RTD-direct test was validated using a serial dilution panel of the WHO standard HBV DNA 97/746 I.

RESULTS

The test had a dynamic range of 0.7-8.0 log10 international units (IU) per mL and the results were shown to be comparable to those obtained with two commercially available tests: the HBV DNA transcription-mediated amplification-hybridization protection assay and the Amplicor HBV Monitor test. In addition, the HBV RTD-direct test, based on magnetic extraction, successfully eliminated PCR inhibitors in clinical specimens.

CONCLUSION

We conclude that the HBV RTD-direct test is an excellent alternative for monitoring patients undergoing antiviral treatment or for screening various clinical specimens.

Prior enrichment of human immunodeficiency virus DNA with probe DNA particles for efficient PCR diagnosis

We report here a novel method by which one can recover human immunodeficiency virus (HIV) DNA in a small volume (approximately 50 microliters) of solution from 8 ml of crude cell lysate which contains as few as several HIV DNA copies. The method uses the specific binding of HIV DNA to HIV probe DNA particles. The HIV DNA thus concentrated on the particles can be subjected to the PCR assay. The method also enables the examination of 100 individual blood specimens in a combined form.

[Prior enrichment of HIV-DNA with probe-DNA particles for an efficient PCR diagnosis]

PCR mediated detection of HIV-DNA has been widely used. However, compared with traditional immunological diagnoses, the extraction of DNA is a laborious and time consuming step. We have developed a procedure for the efficient isolation and concentration of HIV-DNA from cell lysates. We report here a novel method by one can recover HIV-DNA in a small volume (approximately 50 microliters) of solution from a large volume of crude cell lysate which contains as few as several copies. The method uses the specific hybridization of HIV-DNA to HIV probe-DNA particles. This prior enrichment augmented the sensitivity in the detection of HIV-DNA by PCR, and allows us to make a diagnosis even if the specimen contained an extremely low copy number of HIV-DNA molecules in a large volume, which would have otherwise resulted in false-negative data with the conventional extraction method. The method also enables the examination of 100 individual blood specimens in a combined form. Thus, the application of the present enrichment procedure with HIV probe-DNA particles should reduce the labor and cost of HIV diagnosis, since the HIV positive samples represent a very minor group of people among specimens subjected to clinical laboratory tests, and particularly, among blood samples voluntarily donated to be used for transfusions.

Application of the RLGS method to large-size genomes using a restriction trapper

We developed a method for producing restriction landmark genomic scanning (RLGS) profiles of large-size genomes, such as those of higher plants or amphibians using a restriction trapper. Use of the conventional RLGS method is limited to genomes smaller than 3 x 10(9) bp, because the larger genomic DNAs, especially those of more than 1 x 10(10) bp, produce high background due to incorporation of radioactivity at non-specifically damaged sites. Our new method reduces the background levels by reducing genome complexity to 1/200-1/300 using a purification step to enrich DNA fragments carrying specific restriction landmarks at their ends using a restriction trapper. This step makes it possible to obtain RLGS patterns of larger genomes. Our paper describes the practical application for the RLGS method using a restriction trapper with the pine tree genome (3 x 10(10) bp/haploid genome; Pinus koraiensis Sieb. et Zucc.) as an example.

The genes in the thermophilic cyanobacterium Synechococcus vulcanus encoding cytochrome-c oxidase

It is still controversial whether cyanobacteria (blue-green algae) contain an aa3-type cytochrome-c oxidase. We have approached this problem using DNA analysis. Using a DNA probe coding for the most conserved part of subunit I of the Bacillus enzymes, structural genes for the oxidase of a thermophilic cyanobacterium Synechococcus vulcanus were cloned and sequenced. We found genes for subunits II, I, III and IV of this order like those of the Bacillus enzymes, and a terminator structure after the gene for subunit IV. The deduced protein sequences for the subunits II, I and III showed consensus amino-acid residues atevery important portion, suggesting that these genes are operating. However, the S. vulcanus oxidase lacked a cytochrome-c-moiety fused to subunit II, the 13th and 14th hydrophobic segments of subunit I which are lacking in the Paracoccus enzyme, and the 1st and 2nd ones of subunit III which are lacking in the Bacillus enzyme, were not found. A gene homologous to ctaB gene, which locates at the 5'-upstream region of the gene for subunit II and co-transcribed in Bacillus subtilis, was not found. Comparison of protein sequences showed that S. vulcanus cytochrome oxidase is closer to Bacillus cytochrome oxidases than the mitochondrial and Paracoccus enzymes, or quinol oxidases from B. subtilis and Escherichia coli.

Heat shock promoter of thermophilic chaperonin operon

The translation of a heat shock protein (HSP), TGroEL, of thermophilic bacterium PS3 increased within 10 minutes when the culture temperature was raised from 60 degrees C to 70 degrees C. In contrast to hyperthermophilic HSPs such as Pyrodictium ATPase, TGroEL is homologous to GroEL of E. coli (Tamada et al. (1991) Biochem. Biophys. Res. Commun. 197, 565-571). The promoter of the thermophilic heat shock gene (tgrE) was sequenced to analyze the heat shock response. The sequences of the promoter were CCTACTTGCA (-35 region) and GTTCATTAATA (-10 region), which are more heat labile than those of the sigma 32 recognition sites of GroEL. The expression of this homologous tgrE in E. coli may be lethal to the cells. The ATPase alpha subunit of this thermophile is also homologous to TGroEL.

The cytochrome C oxidase genes in blue-green algae and characteristics of the deduced protein sequence for subunit II of the thermophilic cyanobacterium Synechococcus vulcanus

Blue-green algae (cyanobacteria) contain both primitive photosynthetic and respiratory systems in their membranes. The controversial genes coding for an alpha alpha 3-type cytochrome oxidase in cyanobacteria were examined. The DNA probe coding for the most conserved part of subunit I hybridized with DNA fragments from four cyanobacterial species. We have cloned the genes coding for subunits I and II from the genomic library of the thermophilic cyanobacterium Synechococcus vulcanus and determined the nucleotide sequence of the subunit II gene. The deduced protein sequence (327 amino acid residues) indicates that there are two hydrophobic segments near the N-terminus and a hydrophilic intermembrane domain containing ligands for CuA (the ESR-active Copper) similar to other subunit IIs. The S. vulcanus subunit II does not contain the cytochrome c moiety that is present in bacilli and thermophiles.