Cell wall polysaccharides isolated from the fungus <Emphasis Type="Italic">Neotestudina rosatii</Emphasis>, one of the etiologic agents of mycetoma in man

The alkali-extractable water-soluble polysaccharides F1SS isolated from the cell wall of two isolates of the pathogen Neotestudina rosatii and one of Pseudophaeotrichum sudanense, which is now considered as a synonym of the former, have been studied by methylation analysis, GC–MS and NMR spectroscopy. The three polysaccharides differ mainly in their content in galactofuranose, and have the following idealized repeating unit:      

Significant rate accelerated synthesis of glycosyl azides and glycosyl 1,2,3-triazole conjugates

An efficient and significantly rapid access of a series of glycosyl azides and glycosyl 1,2,3-triazole conjugates is reported using modified one-pot reaction conditions. In both cases yields were excellent and single diastereomers were obtained. Figure Rapid preparation of 4-substituted glycosyl 1,2,3-triazole conjugates from glycosyl bromides. CDRI communication no. 7340.     

Concise synthesis of the pentasaccharide O-antigen of Escherichia coli O83:K24:H31 present in the Colinfant vaccine

A block synthetic approach is presented for the synthesis of the pentasaccharide repeating unit of the O-antigen of E. coli O83:K24:H31 strain, present in the “Colifant” vaccine. The target pentasaccharide has been synthesized by coupling a disaccharide with a trisaccharide in excellent yield. Yields are quite satisfactory in all intermediate steps. A concise synthesis of the pentasaccharide repeating unit of the O-antigen of E. coli O83:K24:H31 strain, present in the COLINFANT vaccine is presented. The target pentasaccharide has been synthesized following a block synthetic strategy by coupling a disaccharide with a trisaccharide in excellent yield.     

Concise synthesis of a heptasaccharide antigen found in the cell-wall lipopolysaccharide of Mycobacterium gordonae strain 990

A straight forward synthesis of a heptasaccharide part of the cell-wall lipopolysaccharide of Mycobacterium gordonae strain 990, known to have antigenicity, has been achieved in excellent yield. Judicious choice of protecting groups in the intermediates played a significant role throughout the synthesis. Most of the intermediate steps furnished satisfactory yield. Figure A concise synthesis of an antigenic heptasaccharide motif of the cell-wall glycolipid of Mycobacterium gordonae strain 990 in its preserved natural structure is presented using a general glycosylation condition and judicious protecting group manipulation C.D.R.I. communication number 7377.     

Expedient synthesis of the pentasaccharide repeating unit of the <Emphasis Type="Italic">O</Emphasis>-antigen of <Emphasis Type="Italic">Escherichia coli</Emphasis> O86 and its conformational analysis

Synthesis of the pentasaccharide with a 2-aminoethyl linker attached to the reducing end corresponding to the cell wall O-antigen of Escherichia coli O86 strain is reported. The synthetic strategy involves sequential glycosylation of suitably protected monosaccharide intermediates under similar glycosylation reaction conditions. Thioglycosides have been used as glycosyl donor throughout the synthetic strategy. Conformational analysis of the synthesized pentasaccharide has been carried out using 2D ROESY NMR spectral analysis and all atom explicit molecular dynamics (MD) simulation technique.

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Graphical abstract Facile synthesis of the pentasaccharide with a 2-aminoethyl linker attached to the reducing end corresponding to the cell wall O-antigen of Escherichia coli O86 strain is reported. Conformational analysis of the synthesized pentasaccharide has been carried out using 2D ROESY NMR spectral analysis and all atom explicit molecular dynamics (MD) simulation technique.

     

Structural characterization of the exopolysaccharide PS-EDIV from <Emphasis Type="Italic">Sphingomonas pituitosa</Emphasis> strain DSM 13101

Members of the bacterial genus Sphingomonas are known to produce highly viscous polysaccharides in solution. The exopolysaccharide PS-EDIV was produced by Sphingomonas pituitosa strain DSM 13101, purified using centrifugation, and precipitation and its structure was elucidated by 1D and 2D NMR techniques and chemical microderivatization combined with various mass spectrometric techniques. The following repeating unit of the polysaccharide could be identified: In addition, the polysaccharide also contains acetyl and glyceryl groups whose exact positions were not determined. PS-EDIV is similar in structure to a known exopolysaccharide but differs in being the first bacterial polysaccharide in which two different glucuronic acids are combined. It caused a high viscosity of the culture broth after cultivation for 48 h, although a gelation was not observed.     

Selenylation modification: enhancement of the antioxidant activity of a <Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> polysaccharide

Selenium (Se) is an essential trace element for human beings and many other forms of life. Organic selenium from natural foods has greater bioavailability and is safer than inorganic selenium species. In this article, the structural properties and antioxidant activities of a Glycyrrhiza uralensis polysaccharide (GUP) after selenylation modification were investigated. The GUP was extracted by water decoction and ethanol precipitation and purified via protein elimination using the trichloroacetic acid method and column chromatography. The purified product was subsequently modified by the nitric acid-sodium selenite (HNO₃-Na₂SeO₃) method. The selenized GUP (SeGUP) product was characterized by Fourier transform-infrared (FT-IR) spectroscopy, and its thermal stability, particle size, and antioxidant activities were investigated. FT-IR analysis indicated that the selenium in SeGUP existed mainly as O-Se-O. The thermal stability and particle size of SeGUP differed significantly from those of GUP. Moreover, compared to GUP, SeGUP exhibited greater antioxidant activities in vitro and in vivo. These results indicate that selenylation modification significantly enhances the antioxidant activity of SeGUP, increasing its potential for application as an antioxidant.

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Click inspired synthesis of triazole-linked vanillin glycoconjugates

The 1,3-dipolar cycloaddition of deoxy-azido sugars 1 with alkyne derivatives of p-vanillin, 3-methoxy-4-(prop-2-ynyloxy)benzaldehyde (2) and 2-methoxy-1-(prop-2-ynyloxy)-4-((prop-2-ynyloxy)methyl)benzene) (4) to afford regioselective triazole-linked vanillinglycoconjugates 5 and 6 was investigated in the presence of CuI/DIPEA in dichloromethane. All the developed glycoconjugates were characterized on the basis of IR, NMR, and MS.

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Graphical abstract Triazolyl vanillin glycoconjugates via click chemistry

     

Chemical structure of the cell wall-associated polysaccharide of Bifidobacterium animalis subsp. lactis LKM512

We have demonstrated that Bifidobacterium animalis subsp. lactis LKM512 had some probiotic properties in vivo and in vitro. To further understand their mechanisms, the chemical structure of the extracellular polysaccharide that constructs the cell envelope was determined. The strain was anaerobically cultured in MRS broth at 37 °C for 20 h, then the bacterial cells were harvested by centrifugation and washed. The cell wall-associated polysaccharide (CPS) was prepared from the cell wall component digested by lysozyme. The results of anion exchange and gel filtration chromatography showed that the polysaccharide was negatively charged and had a high molecular mass. The CPS was found to compose of galactopyranosyl, galactofuranosyl, glucopyranosyl and rhamnopyranosyl residues in the molar ratio of 1:1:1:3 by using methylation analysis with GC-MS and HPLC profiling. From the results of the structural characterization by 1 dimensional and 2 dimensional NMR spectroscopy, the polysaccharide was established to be a hexasaccharide repeating unit with the following structure:      

G2, G3, and complete basis set calculations of the thermodynamic properties of cis- and trans-triazene

Following our recent study on triazane, we present a follow-up study on the thermodynamic properties of triazane’s unsaturated analog, triazene. We predict optimized structural parameters, vibrational frequencies, enthalpies of formation, enthalpies of combustion, specific enthalpies of combustion, and proton affinities. Our results indicate that the cis form of triazene has a specific enthalpy of combustion of −15.2 kJ g⁻¹ and the trans form has a specific enthalpy of combustion of −14.7 kJ g⁻¹. Figure Structures of cis- and trans-triazane, N₃H₃     

Adsorption and phase transitions in adsorbed systems: structural properties of CCl<Subscript>4</Subscript> layers adsorbed on a graphite surface

We present the results of simulations of a CCl₄ monolayer adsorbed on a graphite surface. The CCl₄ molecule was represented either by a shapeless superatom or by its atomic sites. The simulations were carried out over a large range of temperatures, from 20 K up to 340 K. We address the following problems: (1) the influence of molecular shape on the structure and stability of phases (particularly at low temperatures), and (2) the influence of the graphite corrugation on layer stability and mechanism of phase transitions. In particular, we discuss the possibility and conditions of the appearance of hexatic phase in the system. Figure Temperature dependence of Φ6 order parameter for CCl₄ monolayer adsorbed onsmooth and corrugated surfaces, in the spherical Lennard Jones (LJ) approximation.For comparison, the order parameter calculated for MacDonald’s five-site potential is also presented     

The platinum-olefin binding energy in series of (PH<Subscript>3</Subscript>)<Subscript>2</Subscript>Pt(olefin) complexes - a theoretical study

Theoretical investigation of Pt(0)-olefin organometallic complexes containing tertiary phosphine ligands was focused on the strength of platinum-olefin electronic interaction. DFT theoretical study of electronic effects in a substantial number of ethylene derivatives was evaluated in terms of the Pt-olefin binding energy using MP2 correlation theory. Organometallics bearing coordinated olefins with general formula (R¹R²C = CR³R⁴)Pt(PH₃)₂ [R = various substituents] had been selected, including olefins containing both electron-donor substituents as well as electron-withdrawing groups. The stability of the corresponding complexes increases with a strengthening electron-withdrawal ability of the olefin substituents. Figure Representation of (CH₂ = CHR)Pt(PPh₃)₂ and the stability chart     

Ab initio and DFT study of the aromaticity of some Fulvalenes derived from Methylidenecyclopropabenzene

Methylidencyclopropabenzene (MCPB) 1 and Fulvalenes 2–4 are molecules of special interest due to the relation between structure and aromaticity. The aim of this work was to analyze this relation and to quantify the aromaticity in 1–4 using different methods. Magnetic properties are directly related with aromaticity; here we studied the magnetic susceptibility and the anisotropy of the magnetic susceptibility. Nucleus indepedent chemical shift (NICS) and the anisotropy of the induced current density (ACID) were also employed. Tools of very different nature, geometric indexes HOMA and Bird, were determinated too for 1–4. All of these measures were found to be in agreement. Figure Both spatial NICS and ACID plot allow to show the aromaticity/antiaromaticity of a ring     

Investigation of the intermolecular proton transfer in the supersystems adenine-methanol/ethanol/i-propanol: MP2 and DFT levels study

Twelve H-bonded supersystems constructed between the adenine tautomers and methanol, ethanol, and i-propanol were studied at the B3LYP and MP2 levels of theory using 6-311G(d,p) and 6-311++G(d,p) basis functions. The thermodynamic parameters of the complex formations were calculated in order to estimate the exact stability of the supersystems. It was proven that the calculated energy barriers of the alcohol-assisted proton transfers are about 60% lower than those of the intramolecular proton transfers in adenine found earlier (Gu and Leszczynski in J Phys Chem A 103:2744–2750, 1999). Figure H-bonded complex between i-propanol and adenine     

G2, G3, and complete basis set calculations on the thermodynamic properties of triazane

As a follow-up study to our study on tetrazane (N₄H₆), we present computed thermodynamic properties of triazane (N₃H₅). Calculated properties include optimized geometries, infrared vibrations, enthalpy of formation, enthalpy of combustion, and proton affinities. We have also mapped the potential energy surface as the molecule is rotated about the N-N bond. We have predicted a specific enthalpy of combustion for triazane of about -20 kJ g⁻¹. Figure Schematic diagram of the dielectric barrier discharge (left) and typical temporal profiles of voltage and current, as obtained from the simulations (right)     

Quantitative trait loci identified for sugar related traits in a sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> spp.) cultivar × <Emphasis Type="Italic">Saccharum officinarum</Emphasis> population

The identification of markers linked to quantitative trait loci (QTLs) for increased sugar accumulation could improve the effectiveness of current breeding strategies in sugarcane. Progeny from a cross between a high sucrose producing cultivar, (denotes Australian plant breeding rights), and a Saccharum officinarum clone, IJ76-514 were grown in two field experiments in different years, and evaluated in the early and mid-season phases of crop maturity, to identify robust QTLs in affecting sucrose content in cane. Using an extensive genetic map constructed for with over 1,000 AFLP and SSR markers, a total of 37 QTLs were identified for brix and pol of which, 16 were detected in both experiments. Of these 37 QTL, 30 were clustered into 12 genomic regions in six of the eight homo(eo)logous groups. Each QTL explained from 3 to 9% of the phenotypic variation observed. Both positive and negative effects were identified and the location of the QTLs on linkage groups belonging to the same homo(eo)logy group suggested that a number of the QTLs were allelic forms of the same genes. Of the 37 QTLs identified, the majority were significant in both early and mature cane, but 8 were identified as early specific QTLs and 9 as mature cane QTLs. In total, 97 interactions were significant (P<10⁻⁵) and these were localised to 32 genomic regions of which 6 were detected with both years’ data. Models including all the QTLs explained from 37 to 66% of the total phenotypic variation, depending on the trait. The results will be subsequently applied in marker assisted breeding. denotes variety covered by Australian plant breeding rights.     

Neighboring group stabilization by σ-holes

We have used density-functional theory to investigate the neighboring-group stabilization of iodine, arsenic, and phosphorus-centered oxyanion moieties in species such as deprotonated 2-iodoxybenzoic acid (IBX) and its analogs. The magnitudes of different stabilizing effects and further candidates for analogous stabilization are analyzed.      

Quantification of sialic acids in red meat by UPLC-FLD using indoxylsialosides as internal standards

Herein we describe a UPLC-FLD-based method for the quantification of the sialic acid content of red meat, using a synthetic neuraminic acid derivative as an internal standard. X-Gal-α-2,6-N-propionylneuraminic acid was synthesized via a chemoenzymatic pathway and its hydrolytic stability was characterized. Known quantities of this compound were incubated with samples of red meat under sialic acid-releasing conditions. The released sialic acids were derivatized, analyzed by UPLC-FLD, and the Neu5Ac/Neu5Gc content of the meat sample was determined by comparison with the internal standard. A number of red meats were analyzed by this method with the following results (Neu5Ac μg/g tissue, Neu5Gc μg/g tissue ± s.d.): pork (68 ± 3, 15.2 ± 0.7), beef (69 ± 8, 36 ± 5), lamb (46 ± 2, 33 ± 1), rabbit (59 ± 2, 0.4 ± 0.4), and hare (50 ± 4, 1 ± 1). We envisage that this methodology will find application in investigating the health effects of dietary Neu5Gc.

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Molecular dynamics study of the initial stages of catalyzed single-wall carbon nanotubes growth: force field development

Effective force fields for Ni-C interactions developed by Yamaguchi and Maruyama for the formation of metallofullerenes are modified to simulate the catalyzed growth of single-wall carbon nanotubes on Ni_n clusters with n >20, and the reactive empirical bond order Brenner potential for C-C interactions is also revised to include the effect of the metal atoms on such interactions. Figure Force field parameters for carbon-metal interactions obtained from DFT calculations in small clusters.