Selective Oxidation of 2′-Deoxyguanosine to Imidazolone by the Chemical Nuclease MnTMPyP Associated to KHSO5 or Sulfite/O2.

Abstract

Mn TMPyP in the presence of sulfite/O₂ catalyses the oxidation of dG into dIz as selectively but slower and less efficiently than in the presence of KHSO_5.     

Synthetic approaches to 6-substituted 9-(3-azido-3,4-dideoxy-β-d,l-erythro-pentopyranosyl)purines

Methyl 3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranoside (6) was synthesized through two routes in five steps from methyl 2,3-anhydro-4-deoxy-β-dl-erythro-pentopyranoside (1). The first route proceeded via selective azide displacement of the 3-tosyloxy group of methyl 4-deoxy-2,3-di-O-tosyl-α-dl-threo-pentopyranoside, followed by detosylation and benzoylation. The second route consisted, with a better overall yield, in the azide displacement of the mesyloxy group of methyl O-benzoyl-4-deoxy-3-O-methylsulfonyl-α-dl-threo-pentopyranoside (10), obtained by benzylate opening of 1, followed by benzoylation, debenzylation, and mesylation. Compound 6 was transformed into its glycosyl chloride, further treated by 6-chloropurine to give the nucleoside 9-(3-azido-2-O-benzoyl-3,4-dideoxy-β-dl-erythro-pentopyranosyl)-6-chloropurine (13). When treated with propanolic ammonia, 13 yielded 9-(3-azido-3,4-dideoxy-β-dl-erythro-pentopyranosyl)adenine.     

Specificity towards oligomannoside and hybrid type glycans of the endo-β-N-acetylglucosaminidase B from the basidiomy ceteSporotrichum dimorphosporum

We have previously shown that an endo--N-acetylglucosaminidase (EC 3.2.1.96) named Endo B, isolated from culture filtrates of the basidiomyceteSporotrichum dimorphosporum cleaves asialo-, and to some extent, monosialylated bi-antennary glycans of theN-acetyllactosamine type linked to the asparagine residue of peptide or protein moieties [Bouquelet S, Strecker G, Montreuil J, Spik G (1980) Biochimie 62:43–49]. In the present paper, the substrate specificity of the enzyme towards oligomannoside and hybrid type glycans has been analyzed. The results obtained indicate that ovalbumin glycopeptides containing four to seven mannose residues and bovine lactotransferrin glycopeptides containing four to nine mannose residues were completely hydrolyzed by the enzyme. The degree of cleavage was variable among hybrid type structures, since glycopeptides containing the following glycans: (Gal)₁(GlcNAc)₃(Man)₅(GlcNAc)₂; (GlcNAc)₃(Man)₅(GlcNAc)₂; (GlcNAc)₃(Man)₄(GlcNAc)₂ were not hydrolyzed by the enzyme while the percentage of hydrolysis of a glycopeptide containing (GlcNAc)₂(Man)₅(GlcNAc)₂ glycan reached 90%. The bovine lactotransferrin was partially deglycosylated (40%) in the absence of non-ionic detergent while native ovalbumin glycoprotein was not hydrolyzed by the enzyme.The oligomannoside-and theN-acetyllactosamine-type degrading activities present in the culture filtrates were not separated at any step of the purification procedure. Both activities were eluted as a single component with an apparent molecular mass of 89 kDa suggesting that they are located on the same enzyme molecule.Endo B represents a powerful tool for removing oligomannoside-andN-acetyllactosamine-type glycans fromN-glycopeptides andN-glycoproteins. Moreover, advantages in the use of Endo B in a soluble form as well as in an immobilized form result in its high activity and in its stability to heat denaturation and storage.Abbreviations Gal d-galactose - Man d-mannose - GlcNAc N-acetyl-d-glucosamine - Con A concanavalin A - Asn asparagine - GLC gas liquid chromatography - TLC thin layer chromatography - Endo endo--N-acetylglucosaminidase - Endo B endo--N-acetylglucosaminidase isolated fromSporotrichum dimorphosporum - PBE polybuffer exchanger - SDS-PAGE sodium dodecylsulfate-polyacrylamide gel electrophoresis     

Extrachromosomal circular DNAs in Drosophila melanogaster: Comparison between embryos and Kc0% cells

We established the size distribution of extrachromosomal covalently closed circular DNA molecules from embryos of various Drosophila melanogaster strains and from Kc0% tissue culture cells. In embryos, more than 80% of the circular DNA molecules are smaller than 2.5 kb and all the distributions show a peak of molecules of between 200 and 400 bp. The Kc0% cell distribution differs mainly from that of embryos in that 48% of the molecules have a size between 4 and 8 kb. Correlating with this, circular molecules homologous to copia, 412 and 297 were detected only in Kc0% cells. The three tandemly repeated families containing the 5S genes, the histone genes and the 240 bp repeat of the ribosomal DNA intergenic spacer, which had previously been identified in circular DNAs from embryos, were also found in cultured cells. A fourth tandemly repeated family corresponding to the 1.688 g/cm³ satellite DNA was detected, both in embryos and Kc0% cells. It consists of circular multimeric molecules containing multiple copies of the 359 bp repeated unit. No circular DNA molecules homologous to the actin genes, the type I ribosomal DNA insertion, or the F and I transposable elements were found in embryos or Kc0% cells. Thus it appears that the extrachromosomal circular DNA molecules from embryos and from tissue culture cells differ mainly in the presence of circular copies of the copia-like transposable elements.     

Callus formation and induction of a cell suspension culture from Acacia senegal

Cell proliferation has been induced from the cambial zone of a branch of Acacia senegal, kept on the basal Knop and Ball medium in the presence of auxin. Transferred on the more complete nutrient medium of Schenk and Hildebrandt, the colonies gave rise to several cell lines. One of the friable lines, consisting of aggregates of parenchymatous cells, gave a cell suspension culture in an agitated liquid medium which is maintained as a strain of illimited growth. The heterogeneous suspension did not undergo noticeable changes after eight transfers. Aggregates collected on a 1000-m nylon seive were able to grow on a solid medium and gave back a friable callus similar to the initial colonies.     

Pseudophillipsia azzouzi nov. sp. Trilobite griffithididé Permien du Djebel Tebaga (Tunisie)

Pseudophillipsia azzouzi nov. sp., found by L. Memmi and J. David in the Dolomies superieures Series of the Djebel Tebaga, takes part of the Ps. sumatrensis-Group. Its stratigraphical position in the Kazanian-Pamirian boundary is in accordance with the global distribution of that Group. The tunisian species, characterized by its ornamentation (particularly of the pygidium), is also remarkable by its large size, twice that of the type-species.     

Antipeptide antibodies to the 141-1141-1141-1receptor confirm the extracellular orientation of the amino-terminus and the putative first extracellular loop

Summary We developed site-directed rabbit antisera against synthetic peptides selected from the deduced amino acid sequence of the hamster lung ₂-adrenergic receptor (amino acids 16–31 and 174–189, respectively). All antisera directed against peptide 1 (four of four rabbits) as well as two antisera directed against peptide 2 (two of four rabbits) recognized the purified ₂-adrenergic receptor in immunoblot conditions when used at a dilution of 1500. Antisera directed against peptide 1 as well as peptide 2 were able to immunoprecipitate iodinated as well as¹²⁵I-cyanopindolol tabeled ₂-adrenergic receptor. This last result implies that the recognized epitopes do not contain the¹²⁵I-cyanopindolol binding domain of the ₂-adrenergic receptor. Immunoblot experiments performed on membrane fractions from hamster lung tissue showed that immunoreactive bands at 64,000, 57,000, 47,000, 44,000 and 38,000 daltons were specifically detected. When purified ₂-adrenergic receptor was iodinated and submitted to glycolytic and/or tryptic treatments, species with similar molecular weights could be recovered. Then, the immunoreactive bands probably correspond to native ₂-adrenergic receptor and to degradative or nonglycosylated species of this molecule. The antisera were also able to detect immunoreactive molecules in murine and human cell lines, suggesting conservation of the probed sequences between these species. Enzymatic linked immunosorbent assay tests on intact cells and immunofluorescence studies confirmed that the amino-terminus and putative first extracellular loop are extracellularly located. Immunofluorescence studies on mouse brain primary cultures showed that cells expressing ₂-adrenergic receptor-like molecules exhibited a neuronal phenotype.