Estimations of energy of noncovalent bonding from integrals over interatomic zero-flux surfaces: Correlation trends and beyond.

Bonding energies of 50 associates composed by neutral molecules (atoms) and bounded by various weak noncovalent interactions are calculated within the DFT framework using the PBE0/aug-cc-pVTZ combination. The electronic virial and electron density values at bond critical points together with their integrals over interatomic surfaces are tested to check their ability to estimate bonding energies. Two correlations schemes dealing with integrals over interatomic surface are suggested to estimate bonding energy of any noncovalent interaction.

Novel Mannich bases of α- and γ-mangostins: Synthesis and evaluation of antioxidant and membrane-protective activity.

A series of new C-4- and C-4/C-5-aminomethyl derivatives were synthesized on the basis of α- and γ-mangostins. A comparative evaluation of their chelating ability, radical scavenging activity and hemolytic activity, as well as antioxidant and membrane-protective properties, was carried out on the model of HO-induced hemolysis of mammalian red blood cells. It was shown that γ-mangostin and its C-4/C-5-derivatives were superior to α-mangostin and its derivatives in all the investigated parameters characterizing the antioxidant activity in the test systems used.

Structure and gene cluster of the O-antigen of Escherichia coli O54.

Mild acid hydrolysis of the lipopolysaccharide of Escherichia coli O54 afforded an O-polysaccharide, which was studied by sugar analysis, solvolysis with anhydrous trifluoroacetic acid, and H and C NMR spectroscopy. Solvolysis cleaved predominantly the linkage of β-d-Ribf and, to a lesser extent, that of β-d-GlcpNAc, whereas the other linkages, including the linkage of α-l-Rhap, were stable under selected conditions (40 °C, 5 h). The following structure of the O-polysaccharide was established: →4)-α-d-GalpA-(1 → 2)-α-l-Rhap-(1 → 2)-β-d-Ribf-(1 → 4)-β-d-Galp-(1 → 3)-β-d-GlcpNAc-(1→ The O-antigen gene cluster of E.

Studies on the O-polysaccharide of Escherichia albertii O2 characterized by non-stoichiometric O-acetylation and non-stoichiometric side-chain l-fucosylation.

An O-polysaccharide was isolated from the lipopolysaccharide of Escherichia albertii O2 and studied by chemical methods and 1D and 2D H and C NMR spectroscopy. The following structure of the O-polysaccharide was established: . The O-polysaccharide is characterized by masked regularity owing to a non-stoichiometric O-acetylation of an l-fucose residue in the main chain and a non-stoichiometric side-chain l-fucosylation of a β-GlcNAc residue.

A rhodium-catalyzed transannulation of N-(per)fluoroalkyl-1,2,3-triazoles under microwave conditions - a general route to N-(per)fluoroalkyl-substituted five-membered heterocycles.

A rhodium-catalyzed transannulation via ring-opening of N-(per)fluoroalkyl-substituted 1,2,3-triazoles followed by cycloaddition with different nitriles, enol ethers, isocyanates and silyl ketene acetals under microwave heating provided a highly efficient route to previously unreported N-(per)fluoroalkyl-substituted imidazoles, pyrroles, imidazolones and pyrrolones, respectively. These reactions were found to be applicable to the synthesis of a variety of 5-membered heterocycles bearing different (per)fluoroalkyl substituents as well as both electron-donating and electron-withdrawing groups attached to the heterocyclic core.

Ozone-Free Synthesis of Ozonides: Assembling Bicyclic Structures from 1,5-Diketones and Hydrogen Peroxide.

Reactions of 1,5-diketones with HO open an ozone-free approach to ozonides. Bridged ozonides are formed readily at room temperature in the presence of strong Brønsted or Lewis acids such as HSO, p-TsOH, HBF, or BF·EtO. The expected bridged tetraoxanes, the products of double HO addition, were not detected.

Structure and genetics of a glycerol 2-phosphate-containing O-specific polysaccharide of Escherichia coli O33.

An O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Escherichia coli O33 followed by gel-permeation chromatography on Sephadex G-50. The polysaccharide was found to contain glycerol 2-phosphate (Gro-2-P), and the following structure of its tetrasaccharide repeat was established by sugar analysis, dephosphorylation, and 1D and 2D H and C NMR spectroscopy: The O33-antigen gene cluster was analyzed and found to be essentially consistent with the O-polysaccharide structure.

Novel Peroxides as Promising Anticancer Agents with Unexpected Depressed Antimalarial Activity.

Twenty six peroxides belonging to bridged 1,2,4,5-tetraoxanes, bridged 1,2,4-trioxolanes (ozonides), and tricyclic monoperoxides were evaluated for their in vitro antimalarial activity against Plasmodium falciparum (3D7) and for their cytotoxic activities against immortalized human normal fibroblast (CCD19Lu), liver (LO ), and lung (BEAS-2B) cell lines as well as human liver (HepG2) and lung (A549) cancer-cell lines. Synthetic ozonides were shown to have the highest cytotoxicity on HepG2 (IC =0.19-0.

THE ROLE OF DNA-METHYLTRANSFERASES IN THE LIFE CYCLE OF HEPATITIS B VIRUS AND PATHOGENESIS OF CHRONIC HEPATITIS B.

Chronic hepatitis B is caused by a persistent form of hepatitis B virus, covalently closed circular DNA (cccDNA). Stability of cccDNA is associated with intracellular localization of cccDNA and formation of minichromosome, regulated by epigenetic mechanisms. One of the key mechanisms in epigenetics is methylation of DNA on CpG islands.

Regioselective synthesis of 3,4-diaryl-5-unsubstituted isoxazoles, analogues of natural cytostatic combretastatin A4.

4,5-Diarylisoxazoles are potent antiproliferative tubulin-targeting agents. Their isomeric 3,4-diaryl-5-unsubstituted isoxazoles are hardly accessible. The synthesis of 3,4-diaryl-5-unsubstituted isoxazoles 13 was designed based on a condensation of arylbenzaldehydes, arylnitromethanes, and ethoxycarbonylmethylpyridinium bromide followed by a selective one-step transformation of intermediate 3,4-diaryl-5-ethoxycarbonyl-4,5-dihydroisoxazole 2-oxides 8.

Interrupted Baeyer-Villiger Rearrangement: Building A Stereoelectronic Trap for the Criegee Intermediate.

The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer-Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2-alkyl shift. Stable cyclic Criegee intermediates constrained within a five-membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β-hydroperoxy-β-peroxylactones) which were formed in high yields in reaction of β-ketoesters with BF ⋅Et O/H O .

Structure elucidation of the O-specific polysaccharide by NMR spectroscopy and selective cleavage and genetic characterization of the O-antigen of Escherichia albertii O5.

The O-specific polysaccharide (O-antigen) was obtained by mild acid degradation of the lipopolysaccharide of Escherichia albertii O5 (strain T150248) and studied by sugar analysis, selective cleavages of glycosidic linkages, and 1D and 2D H and C NMR spectroscopy. Partial solvolysis with anh (anhydrous) CFCOH and hydrolysis with 0.05 M CFCOH cleaved predominantly the glycosidic linkage of β-GalpNAc or β-Galf, respectively, whereas the linkages of α-GlcpNAc and β-Galp were stable.

Acinetobacter baumannii isolate BAL_212 from Vietnam produces the K57 capsular polysaccharide containing a rarely occurring amino sugar N-acetylviosamine.

The structures of capsular polysaccharides (CPSs) produced by different Acinetobacter baumannii strains have proven to be invaluable in confirming the role of specific genes in the synthesis of rare sugars through the correlation of genetic content at the CPS biosynthesis locus with sugars found in corresponding CPS structures. A module of four genes (rmlA, rmlB, vioA and vioB) was identified in the KL57 capsule biosynthesis gene cluster of A. baumannii isolate BAL_212 from Vietnam.

[Overexpression of DNA-methyltransferases in persistency of cccDNA pool in chronic hepatitis B].

Aim: To define the role of DNA-methyltransferases of type 1 and type 3A in hepatitis B viral cycle.

Material And Methods: Human hepatoma cells HepG2 with stable expression of 1.1-mer HBV genome were transfected with vectors encoding DNA-methyltransferase 1 (DNMT1), DNA-methyltransferase 3A (DNMT3A) or were co-transfected with these vectors.

Lipopolysaccharides of Pantoea agglomerans 7604 and 8674 with structurally related O-polysaccharide chains: Chemical identification and biological properties.

Structurally related O-specific polysaccharide (O-antigen) and lipid A components were obtained by mild acid degradation of the lipopolysaccharides (LPSs) of two strains of bacteria Pantoea agglomerans, 7604 and 8674. Studies by sugar analysis along with 1D and 2D H and C NMR spectroscopy enabled elucidation of the following structures of the O-polysaccharides, which differ only in the linkage configuration of a side-chain glucose residue: R=α-d-Glcp in strain 7604 or β-d-Glcp in strain 8674 Lipid A samples were studied by GC-MS and high-resolution ESI-MS and found to be represented by penta- and tetra-acyl species; lipid A of strain 8674 also included hexaacyl species. A peculiar feature of lipid A of both strains is the presence of the major cis-9-hexadecenoic (palmitoleic) acid, which has not been found in P.

Regio-isomeric effects in tandem mass spectra of sulfonium cations generated from thiacyclane based sulfonium salts under soft ionization conditions.

The influence of regio-isomerism of even-electron sulfonium ions on tandem electrospray and matrix-assisted laser desorption/ionization mass spectra recorded by using collision-induced dissociation was investigated. The initial organic sulfides belonged to isomeric thiabicyclane series (substituted 7- and 8-thiabicyclo[4.3.

Pore-forming activity of new conjugate antibiotics based on amphotericin B.

A series of amides of the antifungal antibiotic amphotericin B (AmB) and its conjugates with benzoxaboroles was tested to determine whether they form pores in lipid bilayers and to compare their channel characteristics. The tested derivatives produced pores of larger amplitude and shorter lifetime than those of the parent antibiotic. The pore conductance was related to changes in the partial charge of the hydrogens of the hydroxyl groups in the lactone ring that determined the anion coordination in the channel.

Acinetobacter baumannii K13 and K73 capsular polysaccharides differ only in K-unit side branches of novel non-2-ulosonic acids: di-N-acetylated forms of either acinetaminic acid or 8-epiacinetaminic acid.

Structures of capsular polysaccharides of Acinetobacter baumannii isolates carrying KL13 and KL73 gene clusters were established. The closely related KL73 and KL13 gene clusters differ only by one gene in the module responsible for synthesis of the non-2-ulosonic acids. The K13 and K73 polysaccharides differ only in a single side-chain sugar, which is either 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-altro- or -d-glycero-l-altro-non-2-ulosonic acid [di-N-acetylated forms of acinetaminic acid (Aci5Ac7Ac) or 8-epiacinetaminic acid (8eAci5Ac7Ac), respectively].

Peroxides with Anthelmintic, Antiprotozoal, Fungicidal and Antiviral Bioactivity: Properties, Synthesis and Reactions.

The biological activity of organic peroxides is usually associated with the antimalarial properties of artemisinin and its derivatives. However, the analysis of published data indicates that organic peroxides exhibit a variety of biological activity, which is still being given insufficient attention. In the present review, we deal with natural, semi-synthetic and synthetic peroxides exhibiting anthelmintic, antiprotozoal, fungicidal, antiviral and other activities that have not been described in detail earlier.

Structures and gene clusters of the O-antigens of Escherichia albertii O3, O4, O6, and O7.

The O-specific polysaccharides (OPSs) called O-antigens were obtained by mild acid degradation of the lipopolysaccharides of Escherichia albertii serotypes O3, O4, O6, and O7 and studied by sugar analysis along with 1D and 2D H and C NMR spectroscopy. The following structure was established for the OPS of E. albertii O4, which, to our knowledge, is unique among known bacterial polysaccharide structures: →2)-α-l-Rhap-(1 → 2)-α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 3)-α-d-GalpNAc-(1 → 3)-β-d-GlcpNAc-(1→ The OPS structure of the strain of E.

Structure and gene cluster of the O-antigen of Escherichia albertii O1 resembling the O-antigen of Pseudomonas aeruginosa O5.

The O-specific polysaccharide (O-antigen) was obtained by mild acid degradation of the lipopolysaccharide of Escherichia albertii serotype O1 strain SP20140089 and studied by sugar analysis along with 1D and 2D H and C NMR spectroscopy. The following structure was established for the trisaccharide repeating unit of the O-polysaccharide: →4)-β-d-ManpNAc3NAcA-(1 → 4)-β-d-GlcpNAm3NAcA-(1 → 3)-α-d-GlcpNAc-(1→ where ManNAc3NAcA and GlcNAm3NAcA indicate 2,3-diacetamido-2,3-dideoxymannuronic acid and 2-acetimidoylamino-3-acetamido-2,3-dideoxyglucuronic acid, respectively. While showing some similarity with O-polysaccharide structures of a group of Pseudomonas aeruginosa serotypes (O2, O5, O16, O18, and O20), that of E.

Radical Nitration-Debromination of α-Bromo-α-fluoroalkenes as a Stereoselective Route to Aromatic α-Fluoronitroalkenes-Functionalized Fluorinated Building Blocks for Organic Synthesis.

A new highly efficient method for the synthesis of 2-fluoro-2-nitrostyrenes was described. Radical nitration of readily available 2-bromo-2-fluorostyrenes with Fe(NO)·9HO resulted in the formation of the corresponding α-fluoro-nitroalkenes in isolated yields up to 92%. The reaction proceeded as a nitration-debromination sequence to highly stereoselectively give α-fluoro-nitroalkenes as Z-isomers only.

Verification of oligomycin A structure: synthesis and biological evaluation of 33-dehydrooligomycin A.

Although, the structure of oligomycin A (1) was confirmed by spectroscopic and chemical evaluations, some crystallographic data cast doubt on the originally adopted structure of the side 2-hydroxypropyl moiety of this antibiotic. It was suggested that the side chain of the oligomycin is enol-related (2-hydroxy-1-propenyl). To clarify this matter we synthesized and evaluated 33-dehydrooligomycin A (2) prepared by the Kornblum oxidation of 33-O-mesyloligomycin A (3) by dimethyl sulfoxide.

Stereoelectronic Control in the Ozone-Free Synthesis of Ozonides.

The value of stereoelectronic guidelines is illustrated by the discovery of a convenient, ozone-free synthesis of bridged secondary ozonides from 1,5-dicarbonyl compounds and H O . The tetraoxane products generally formed in reactions of carbonyl and dicarbonyl compounds with H O were not detected because the structural distortions imposed on the tetraoxacyclohexane subunit in [3.2.

The KL24 gene cluster and a genomic island encoding a Wzy polymerase contribute genes needed for synthesis of the K24 capsular polysaccharide by the multiply antibiotic resistant Acinetobacter baumannii isolate RCH51.

The whole-genome sequence of the multiply antibiotic resistant Acinetobacter baumannii isolate RCH51 belonging to sequence type ST103 (Institut Pasteur scheme) revealed that the set of genes at the capsule locus, KL24, includes four genes predicted to direct the synthesis of 3-acetamido-3,6-dideoxy-d-galactose (d-Fuc3NAc), and this sugar was found in the capsular polysaccharide (CPS). One of these genes, fdtE, encodes a novel bifunctional protein with an N-terminal FdtA 3,4-ketoisomerase domain and a C-terminal acetyltransferase domain. KL24 lacks a gene encoding a Wzy polymerase to link the oligosaccharide K units to form the CPS found associated with isolate RCH51, and a wzy gene was found in a small genomic island (GI) near the cpn60 gene.