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The enzyme galacturonate oxidoreductase PcGOR from Penicillium camemberti reduces the C-1 carbon of D-glucuronate and C-4 epimer D-galacturonate to their corresponding aldonic acids, important reactions in both pectin catabolism and ascorbate biosynthesis. PcGOR was active on both glucuronic acid and galacturonic acid, with similar substrate specificities (kcat/Km) using the preferred co-substrate NADPH. Substrate acceptance extended to lactone congeners, and D-glucurono-3,6-lactone was converted to L-gulono-1,4-lactone, an immediate precursor of ascorbate. Reaction with glucuronate showed only minor substrate inhibition, and the product L-gulonate and L-gulono-1,4-lactone were both found to be competitive inhibitors with Ki in the low mM range. In contrast, reaction with C-4 epimer galacturonate displayed marked substrate inhibition. Moreover, the product L-galactonate and L-galactono-1,4-lactone were observed to mitigate substrate inhibition by galacturonate, with the lactone having a greater effect than the acid.

Modern biorefining of cellulose and chitin requires the use of glycoside hydrolases (GHs) and lytic polysaccharide monooxygenases (LPMOs). LPMOs use molecular oxygen and two electrons from an external electron donor to cleave glycosidic bonds, by a mechanism that entails oxidization of the C1-carbon of glucose and N -acetylglucosamine, respectively, to produce δ-lactones. The equilibrium between these δ-lactones and their aldonic acids, which dominate at neutral pH, is of importance, since the former are potential inhibitors of GHs. We have used 13 C NMR to obtain more insight into the properties of the oxidized compounds and have studied the properties of N,N ′ ,N ″-triacetylchitotrionic acid, using 13 C NMR at various pHs and temperatures. Thus, we have determined the p K a of the aldonic acid to be 2.88 ± 0.05. The equilibrium constant for lactone at pH 1.41 was 0.137 ± 0.008 corresponding to a Δ G ° of 4.9 ± 0.2 kJ/mol. Using Van’t Hoff analysis Δ H ° and Δ S ° were determined to be 19.5 ± 1.6 kJ/mol and 49.0 ± 5.4 J/K mol, respectively.

We describe here the identification and characterization of two novel enzymes belonging to the IlvD/EDD protein family, the D-xylonate dehydratase from Caulobacter crescentus, Cc XyDHT, (EC 4.2.1.82), and the L-arabonate dehydratase from Rhizobium leguminosarum bv. trifolii, Rl ArDHT (EC 4.2.1.25), that produce the corresponding 2-keto-3-deoxy-sugar acids. There is only a very limited amount of characterization data available on pentonate dehydratases, even though the enzymes from these oxidative pathways have potential applications with plant biomass pentose sugars. The two bacterial enzymes share 41 % amino acid sequence identity and were expressed and purified from Escherichia coli as homotetrameric proteins. Both dehydratases were shown to accept pentonate and hexonate sugar acids as their substrates and require Mg2+ for their activity. Cc XyDHT displayed the highest activity on D-xylonate and D-gluconate, while Rl ArDHT functioned best on D-fuconate, L-arabonate and D-galactonate. The configuration of the OH groups at C2 and C3 position of the sugar acid were shown to be critical, and the C4 configuration also contributed substantially to the substrate recognition. The two enzymes were also shown to contain an iron-sulphur [Fe-S] cluster. Our phylogenetic analysis and mutagenesis studies demonstrated that the three conserved cysteine residues in the aldonic acid dehydratase group of IlvD/EDD family members, those of C60, C128 and C201 in Cc XyDHT, and of C59, C127 and C200 in Rl ArDHT, are needed for coordination of the [Fe-S] cluster. The iron-sulphur cluster was shown to be crucial for the catalytic activity (k(cat)) but not for the substrate binding (K-m) of the two pentonate dehydratases.

Organic compounds receive from industries as effluents are highly toxic and hazardous for the environment. Conventional oxidation process for the oxidation of organic compounds through use of N-bromophthalimide (NBP) is one of the significant process for conversion of organic compounds into environmental friendly or less harmful substances. The main scenario of this review is oxidation and kinetics of different organic compounds by NBP with different experimental methods—iodometric and potentiometric along with uncatalyzed, and catalyzed system. In addition to this we also summarize synthesis, properties and reactive species of NBP. Oxidation products obtained by oxidation of various organic compounds by NBP were acetic acid, aldehyde, carbon dioxide, ammonia, cyanide, aldonic acid etc. Present review, first time offers all aspects of NBP as an oxidizing agent for oxidation of organic compounds.

Carbonaceous meteorites provide the best glimpse into the solar system’s earliest physical and chemical processes. These ancient objects, ~4.56 billion years old, contain evidence of phenomena ranging from solar system formation to the synthesis of organic compounds by aqueous and (likely) low-temperature photolytic reactions. Collectively, chemical reactions resulted in an insoluble kerogen-like carbon phase and a complex mixture of discrete soluble compounds including amino acids, nucleobases, and monosaccharide (or “sugar”) derivatives. This review presents the documented search for sugars and their derivatives in carbonaceous meteorites. We examine early papers, published in the early 1960s, and note the analytical methods used for meteorite analysis as well as conclusions on the results. We then present the recent finding of sugar derivatives including sugar alcohols and several sugar acids: The latter compounds were found to possess unusual “d” enantiomeric (mirror-image) excesses. After discussions on the possible roles of interstellar grain chemistry and meteorite parent body aqueous activity in the synthesis of sugar derivatives, we present a scenario that suggests that most of Earth’s extraterrestrial sugar alcohols (e.g., glycerol) were synthesized by interstellar irradiation and/or cold grain chemistry and that the early solar disk was the location of the initial enantiomeric excesses in meteoritic sugar derivatives.

Polysaccharide degradation mediated by hydroxyl radicals (HO˙) or lytic monooxygenases (LPMOs) is relevant in various biological and industrial processes. Thereby, the Fenton-induced (H2O2/Fe2+) oxidation of mixed-linkage (1→3,1→4)-β-D-glucan (BG), a cereal dietary fibre with several well-established health promoting properties, shows potential for modulating BG functionality. The precise identification of oxidation products, however, is impeded by their diversity due to the indiscriminate nature of HO˙, the large molecular weight, and the corresponding low frequency of discrete alterations along the polymer chain. In this paper, we studied the Fenton-induced degradation of several constitutionally isomeric glucotetraoses as BG model compounds by hydrophilic interaction UPLC-MS/MS in negative ion, high resolution mode. The influence of the β-(1→3)-linkage on the reaction was investigated with regard to degradation kinetics, formation of products, and MS/MS fragmentation patterns. The position and occurrence of a β-(1→3)-bond had no influence on the degradation kinetics. Classification into primary and secondary acidic oxidation products by monitoring their progress over time is also demonstrated, implying complexation of primary aldonic acid products by the catalytic iron and subsequently facilitated site-specific secondary oxidation, underlining the metal's importance beyond its role as HO˙-generating catalyst. Similarly to oxidations mediated by certain LPMOs, thorough MS/MS-analysis of selected products and comparison with synthesised standards confirmed two types of glycosidic cleavage cascades induced by HO˙-mediated H-atom abstraction at C1 and C3/C4, producing gluconic acids, native oligosaccharides, and oxo-oligomers (carbonyl at non-reducing end). Additionally, systematic study of other oxo-products from the different isomers and rationalisation of MS/MS fragmentation mechanisms allowed for the identification of potentially diagnostic fragment signals for oxidised cereal BG.

Aim of the study was the determination of the influence of the D-gluconic acid and its acetyl derivative (2,3,4,5,6-penta-O-acetyl-D-gluconic acid) on microbiological degradation in aerobic conditions of azo dyes (Schaffer salt and I acid derivatives). The rest of the aldonic acid and its acetylated form in the structure of azo dye play a role of an additional source of carbon for the used microorganisms. To investigations were used fungus: Aspergillus niger, Geotrichum condidum and bacterias: Pseudomonas fluorescens, Streptomyces roseochromogens. From all tested microorganisms only Aspergillus niger and Pseudomonas fluorescens show sufficient ability to decomposition of tested dyes during research carried out in shaken culture.

Lytic polysaccharide monooxygenases are copper-dependent enzymes that perform oxidative cleavage of glycosidic bonds in cellulose and various other polysaccharides. LPMOs acting on cellulose use a reactive oxygen species to abstract a hydrogen from the C1 or C4, followed by hydroxylation of the resulting substrate radical. The resulting hydroxylated species is unstable, resulting in glycoside bond scission and formation of an oxidized new chain end. These oxidized chain ends are spontaneously hydrated at neutral pH, leading to formation of an aldonic acid or a gemdiol, respectively. LPMO activity may be characterized using a variety of analytic tools, the most common of which are high-performance anion exchange chromatography system with pulsed amperometric detection (HPAEC-PAD) and MALDI-TOF mass spectrometry (MALDI-MS). NMR may be used to increase the certainty of product identifications, in particular the site of oxidation. Kinetic studies of LPMOs have several pitfalls and to avoid these, it is important to secure copper saturation, avoid the presence of free transition metals in solution, and control the amount of reductant (i.e., electron supply to the LPMO). Further insight into LPMO properties may be obtained by determining the redox potential and by determining the affinity for copper. In some cases, substrate affinity can be assessed using isothermal titration calorimetry. These methods are described in this chapter.

Carbohydrate is one kind of raw materials available in large scale, and they are also important renewable resources for industry. Their oxidation products have many applications in different fields. In this paper, biotransformation of L-rhamnose using Pseudomonas taetrolens resting cells was investigated, and the product was separated and indentified to be L-rhamnonic acid by high-performance liquid chromatography (HPLC) and NMR. P. taetrolens capable of transforming L-rhamnose to L-rhamnonic acid was reported for the first time. The influence of temperature, cell density and shaker speed on L-rhamnonic acid production from L-rhamnose by P. taetrolens was also investigated, and the final production rate reached 90% when the transformation was carried out for about 48 h under the condition of temperature 37 °C, cell concentration, OD600 = 40 and 180 rpm.

Interest in biomass biorefineries and especially their aldonic acid products has been growing in recent years. However, the analytical methods for aldonic acids have only rarely been explored. In this study, a simple one-step method was developed using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). With this method, five wood monosaccharides and their corresponding aldonic acids, including arabinose, galactose, glucose, xylose, mannose, arabonic acid, galactonic acid, gluconic acid, xylonic acid, and mannonic acid, were simultaneously separated and quantitatively determined. The separation was performed on a CarboPacTM PA-10 column (250 mm × 2 mm) with a gradient elution using NaOH solution as the mobile phase. The calibration curves showed good linearity (R2 ≥ 0.9993) for the five monosaccharides and the corresponding aldonic acids in the range of 0.1 to 10.0 mg/L. The spiked recoveries of the 10 components ranged from 93.92% to 104.15%, wi...

Novel surface plasmon resonance (SPR) sensing surfaces were developed from the perspective of reversible self-assembling of the mixed dextran surfactant polymers onto SPR gold chips. Two comb-like dextran surfactant polymers, which are different in their dextran molecular weight (MW) distribution and the presence of amine functional groups, and their characterization were synthesized. These structurally well-defined surfactant polymers include a bimodal amine dextran surfactant polymer and a monomodal dextran surfactant polymer. The bimodal one consists of poly (vinyl amine) (PVAm) backbone with amine functionalized high MW dextran, non-functionalized low MW dextran and hydrophobic hexyl pendant groups. Allyl high MW dextran aldonic acid and low MW dextran aldonic acid chains with various ratios were sequentially attached to PVAm. The unreacted amine groups on the backbone were further grafted with hexanoic acid and the allyl groups on the high MW dextran were finally converted to amine. The monomodal surfactant polymer, PVAm with non-functionalized low MW dextran and hexyl branches, was synthesized and characterized using similar procedures, except with the absence of allyl high MW dextran aldonic acid and the amine functionalization. The molecular compositions of the surfactant polymers were determined by FTIR and 1H-NMR. Surface active properties at the air-water interface were determined using tensiometer. Reduction in water contact angles was observed on the surfactant treated surfaces. Reversible self-assembling of the synthesized surfactant polymers on SPR gold chip surface was monitored using SPR analysis. Reproducibility of the mixed surfactant assembling process was preliminarily confirmed by a consistent increase in reflectivity change, while no detectable changes in the reflectivity under a 1-h buffer flow indicated stability of the absorbed surfactant layer. Moreover, a simple, quick flow of a basis regeneration solution completely removed the adsorbed surfactant from the surface. Our preliminary investigation also exhibited that the regenerated SPR gold chip was effectively reusable.

Carbohydrates are polyhydroxyaldehydes (aldoses) or polyhydroxyketones (ketoses) composed of C, H, and O. They are classified into monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides can be trioses, tetroses, pentoses, etc. depending on the number of carbon atoms in the molecule. They present optical isomerism due to the presence of an asymmetric or chiral C. In animals, most carbohydrates in humans are d isomers. Glucose is an aldohexose and the most important monosaccharide in humans, used as fuel by cells. Other aldohexoses are galactose and mannose, which form part of complex molecules. Fructose is a ketohexose, while ribose is the most important aldopentose and a component of RNA. These molecules usually form a cyclic structure, which could be pyran or furan and they present isomers α and β. There are monosaccharide derivatives which include the following: (1) glycosides, in which the aldehyde or the ketone group react with other molecule; (2) polyalcohols, which are obtained by reduction of the aldehyde or ketone group; (3) deoxysugars, which are produced by loss of oxygen from the alcohol group of a monosaccharide; (4) aldonic, aldaric, and uronic acids, which result from oxidation of the C1 or C6 of aldoses; (5) phosphate esters, which are produced by phosphorylation and are commonly found as monosaccharide metabolic products; (6) amino sugars, which generally have an amine group attached to C2 (glucosamine and galactosamine). Other nitrogenous derivatives are neuraminic and muramic acids. Disaccharides include maltose, composed of two d-glucoses linked by a α-glycosidic bond from the C1 of one to the OH at C4 of the other glucose (α-1→4 glycosidic bond). Lactose is the milk sugar, formed by d-galactose and d-glucose bound via β glycosidic bound from C1 of galactose to C4 of d-glucose (β-1→4 glycosidic bond). Sucrose, a common sweetener, is formed by d-fructose and α-d-glucose linked through a double glycosidic bond between C1 of α-glucose to C2 of β-fructose⋅ Polysaccharides or glycans are polymeric macromolecules, classified into: homo- and heteropolysaccharides. Homopolysaccharides includes starch, which is the nutrient reserve of plants, composed by amylose and amylopectin. Amylose has 1000–5000 d-glucose units joined linearly by α-1→4 glycosidic bonds. Amylopectin is a polymer of over 600,000 glucose units. It contains the basic structure of amylose plus branches formed by approximately 25 glucose residues inserted on the main chain by α-1→6 bonds. Glycogen is a polymer that serves as energy reserve polymer in animals. It is structurally similar to amylopectin, but with more branches. Dextrins are end products of partial hydrolysis of amylopectin by amylase. Dextrans, are branched d-glucose polymers, like amylopeptin and glycogen, with different glycosidic bonds. Inulin is a polymer of fructose molecules bound via α-2→1. Cellulose, an important structural role in plants; it is a linear polymer of glucose with β-1→4 bonds. Chitin constitutes the exoskeleton of insects and crustaceans and it is a polymer of N-acetyl-d-glucosamine units, linked by β-1→4 bonds. Heteropolysaccharides include glycosaminoglycans (hialuronic acid, chondroitin sulfate, dermatan, heparan and keratan sulfates, and heparin). Heteropolysaccharides bound to other kind of molecules constitute proteoglycans, peptidoglycans, glycolipids (gangliosides), and glycoproteins. Proteoglycans result from the association of glycan chains (chondroitin sulfate, dermatan sulfate, keratan), bound via glycosidic bonds to the hydroxyl of serine or threonine residues (O-glycosidic bond), or to the N of asparagine residues (N-glycosidic bond) of proteins. Peptidoglycans are the main component of bacterial cell walls. They consist of N-acetyl-d-glucosamine and N-acetyl-muramic acid. Glycoproteins are carbohydrates conjugated to proteins by O- or N-glycosidic linkages. Gangliosides and glycoproteins differ from proteoglycans because they have shorter carbohydrate chains. They play important roles in antigen/antibody recognition on the surface of cells.

Background: Lytic polysaccharide monooxygenase (LPMO) is a group of recently identified proteins that catalyze oxidative cleavage of the glycosidic linkages of cellulose and other polysaccharides. By utilizing the oxidative mode of action, LPMOs are able to enhance the efficiency of cellulase in the hydrolysis of cellulose. Particularly, auxiliary activity family 9 (AA9) is a group of fungal LPMOs that show a type-dependent regioselectivity on cellulose in which Types 1, 2, and 3 hydroxylate at C1, C4, and C1 and C4 positions, respectively. In this study, we investigated comparative characteristics of TtAA9E from Thielavia terrestris belonging to Type 1 and TaAA9A from Thermoascus aurantiacus belonging to Type 3 on cellulose and pretreated lignocellulose. Results: From product analysis, TtAA9E dominantly generated oligosaccharides with an aldonic acid form, which is an evidence of C1 oxidation, while TaAA9A generated oligosaccharides with both aldonic acid and 4-ketoaldose forms, which is evidence of C1 and C4 oxidations, respectively. For hydrolysis of cellulose (Avicel) by cellulase, higher synergism was observed for TtAA9E than for TaAA9A. For hydrolysis of pretreated lignocellulose using rice straw, synergistic behaviors of TtAA9E and TaAA9A were different depending on the pretreatment of rice straw. Specifically, on acid-pretreated rice straw, TtAA9E showed a higher synergism than TaAA9A while on alkali-pretreated rice straw, TaAA9A showed a higher synergism than TtAA9E. Conclusions: We show type-dependent action modes of TtAA9E and TaAA9A for cellulose oxidation together with substrate-dependent synergistic hydrolysis of cellulosic substrates. The results obtained from this study indicate the different behaviors of AA9s on cellulose and pretreated lignocellulose, suggesting a selection of AA9 proteins specific to substrates is required for industrial utilization.

The preparation of the δ-heptonolactones, 4- O -benzyl- D - glycero - D - D - gulo -heptono-1,5-lactoneand 4- O -benzyl- D - glycero - D - allo -heptono-1,5-lactone, by Kiliani reactions on 3- O -benzylglucose and 3- O -benzylallose are reported; acetonides of the two lactones are described.

Iodide ion induces a protected 5-formyl-2-iodo-1,5-lactone to undergo a reductive aldol condensation to give a fully substituted cyclopentane derivative in moderate yield; this strategy may provide a general synthesis of such highly functionalised carbocycles as mannostatins and allosamizolines.

The use of readily available sugar lactones in the synthesis of polyhydroxylated pyrrolidines is illustrated by the preparation of the glucosidase inhibitor 1,4-dideoxy-1, 4-imino-D-glucitol from D-galactonolactone and by the conversion of D-gulonolactone into 1,4-dideoxy-l,4-imino-D-allitol, 1,4-dideoxy-l,4-imino-D-ribitol, and (2S,3R,4S)-3,4-dihydroxyproline.

The syntheses of nojirimycin δ-1actam and of deoxynojirimycin from a divergent ido-furanose intermediate are reported.

A method for simultaneous separation and quantitative determination of arabinose, galactose, glucose, xylose, xylonic acid, gluconic acid, galacturonic acid, and glucuronic acid was developed by using high performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The separation was performed on a CarboPacTM PA-10 column (250 mm × 2 mm) with a various gradient elution of NaOH-NaOAc solution as the mobile phase. The calibration curves showed good linearity (R2 ≥ 0.9993) for the monosaccharides, uronic acids, and aldonic acids in the range of 0.1 to 12.5 mg/L. The detection limits (LODs) and the quantification limits (LOQs) were 4.91 to 18.75 μg/L and 16.36 to 62.50 μg/L, respectively. Relative standard deviations (RSDs) of the retention times and peak areas for the seven consecutive determinations of an unknown amount of mixture were 0.15% to 0.44% and 0.22% to 2.31%, respectively. The established method was used to separate and determine four monosaccharides, two uronic acids, and two aldonic acids in the prehydrolysate from dilute acid steam-exploded corn stover within 21 min. The spiked recoveries of monosaccharides, uronic acids, and aldonic acids ranged from 91.25% to 108.81%, with RSDs (n=3) of 0.04% ~ 6.07%. This method was applied to evaluate the quantitative variation of sugar and sugar acid content in biomass prehydrolysates.

The selective oxidation of D-galactose to galactonic acid over Au/Al2O3 was studied isothermally in a semi-batch shaker reactor under pH-controlled conditions at atmospheric pressure. A series of Au/Al2O3 catalysts were prepared and calcined at different temperatures to achieve different gold-particle sizes. The catalytic properties of the gold nanoparticles were affected by the cluster size. A detailed comparison of activity and selectivity of these catalysts was made, which demonstrated that Au/Al2O3 with a mean particle size of 2.6 nm exhibited the highest activity. The influence of the pH value of the reaction medium on the selective oxidation of D-galactose was elucidated. Alkaline conditions were characterized by high catalyst activity and selectivity to aldonic acid. Inhibition of the catalytic activity was observed in the acidic medium. The intermediate species was present at low pH values, and this resulted in low conversion and selectivity to the main product, galactonic acid. The electrochemical potential of the catalyst was correlated to the catalytic activity.

Properties of the phenoloxidase (PO) from adult of Gastrolina depressa Baly (Coleoptera: Chrysomelidae) as well as effects of some metal ions and inhibitors on the activity of PO purified by (NH 4 ) 2 SO 4 were determined. The optimal pH and temperature of the enzyme for the oxidation of catechol were determined to be at pH 7.5 and at 40 °C, respectively. The kinetic parameters for the oxidation of L-DOPA and catechol by the PO were 15.01 and 9.17 mM, respectively. The PO activity was strongly inhibited by Zn 2+ and Cu 2+ , different to Mg 2+ slightly. Both ascorbic acid and cysteine exhibited competitive inhibition and the inhibitory constants ( K i ) were determined to be 2.22 mM and 0.40 mM, respectively.

Analysis of compounds in meteorites revealed a need to simultaneously characterize multiple enantiomers of sugar acids (aldonic acids) present in trace amounts. Analyses by gas chromatography-mass spectrometry demonstrated that all but two of the three-carbon through six-carbon straight-chained sugar acid enantiomer pairs could be resolved using a single derivatization procedure and one set of GC parameters. Compounds were analyzed as their ethyl ester/O-triflouroacetyl, isopropyl ester/O-triflouroacetyl and isopropyl ester/O-pentafluoropropionyl derivatives on a capillary column containing permethylated beta-cyclodextrin (Chirasil-Dex CB) as the stationary phase. Characteristic mass fragments are related to the ester groups while several ions are also common to derivatized monosaccharides.

Dicyclohexylcarbodiimide-promoted self-condensation of 2,3:4,5-di- O -isopropylidene- d -galactonic acid ( 3 ) led to the macrocyclic oligomeric cyclo[(2,3:4,5-di- O -isopropylidene-(1→6)- d -galactonate) 2 ] ( 4 ) and cyclo[(2,3:4,5-di- O -isopropylidene-(1→6)- d -galactonate) 3 ] ( 5 ), having, respectively, 14- and 21-membered rings. The macrocycles 4 and 5 were also synthesized by cyclization of the respective linear dimer 11 and trimer 14 ω-hydroxy acids precursors prepared by stepwise additions of 3 . Compounds 4 and 5 are biomaterials that may be described as macrolactone-cyclodextrins.

An highly stereoselective, flexible and very short synthetic approach to d - ribo -configured ureido monosaccharides of the aldose, aldonic acid and alditol series has been performed starting from the 5-(alditol-1- C -yl)-hydantoin intermediates, obtained via aldol-type addition reaction of hydantoin based building blocks to enantiomerically pure aldehydes. A study to assess the stereoselectivity of this reaction has been undertaken and a very high increase of diastereoselectivity was observed depending on the hydantoin protecting group. The imidazolidinone ring elaboration of 5-(alditol-1- C -yl)-hydantoin intermediates to give ureido sugar derivatives was studied.

This paper deals with comparative studies on the use of copper(II), cobalt(II), nickel(II) and zinc(II) complexes of d-gluconic acid, d-saccharic acid and l-threonic acid as chiral selectors for the enantioseparation of aromatic amino acids and glycyl dipeptides using the principle of ligand-exchange capillary electrophoresis. Although copper(II) is the most frequently used central ion in ligand-exchange capillary electrophoresis, in the case of d-gluconic acid cobalt(II) was shown to be an alternative for the enantioseparation of amino acids. Glycyl dipeptides, however, were resolved only with copper(II) complexes. Zn(II) as a central ion was not effective in all cases and with Ni(II) only some partial separations were achieved.

Eight R2Sn(IV)-D-aldonate complexes [(R = Me, Bu; D-aldonate = D-galactonate2− (Galn), D-Gluconate2− (Glun), D-Gulonate2− (Guln), D-Ribonate2− (Ribn)], five of which are new derivatives, have been synthesized and structurally characterized both in solid and solution state by IR, 119Sn Mossbauer and 1H, 13C, 119Sn NMR spectroscopies, showing that ligands act as dianonic chelating agents. In solution phase, NMR data suggest that the bidentate chelation is attained by the O1 carboxylate and the vicinal O2 alkoxide atoms, which can be dynamically extended to a third binding site (O4) competing with O2. In Me2Sn(IV)-D-gluconate complex the occurrence of a self-association process leading to a dimeric species was also observed. Histopathological studies on different organs of Liza saliens showed that the dibutyltin(IV)-D-aldonate complexes, although preserving the defense immunity system, exhibit a specific toxicity on some target cells and organs. The toxicity of such complexes has been compared with respect to the effects of a previous study with tributyltin(IV) chloride solutions. Copyright © 2008 John Wiley & Sons, Ltd.

4-O-Thiocarbamoylmethyl-Neu5Ac2en 3 has strong inhibitory activity toward human parainfluenza virus type 1 (hPIV-1) sialidase compared with the parent Neu5Ac2en 2. We synthesized analogs having thiocarbamoylethyl- 4 and thiocarbamoylpropyl group 5 at the C-4 position of 2. The inhibition degrees of 4 and 5 were weaker than that of thiocarbamoylmethyl analog 3, indicating a remarkable effect of the carbon chain length in thiocarbamoylalkyl groups at the C-4 position on inhibitory activities against hPIV-1 sialidase.

In this work, the catalytic conversion of monosaccharides, such as d -glucose, d -fructose, d -mannose, d -galactose, and d -xylose, into lactic acid and aldonic acid in an alkaline media using supported noble metal catalysts under flowing air was investigated. Thus far, the conventional chemical conversions of d -glucose into lactic acid, such as alkaline degradations and hot water reactions, involved large amounts of by-products including unidentified compounds. To improve the atom economy for the d -glucose conversion, we examined a one-pot reaction of d -glucose into lactic acid and gluconic acid with the alkaline degradation and the air oxidation using supported metal catalysts. It succeeded in yielding about 45 C-% of lactic acid and about 45 C-% of gluconic acid from d -glucose using Pt/C catalysts with a 1.0 mol L −1 of sodium hydroxide aqueous solution at 353 K under flowing air.

Direct generation of electricity from monosaccharides of lignocellulosic biomass was examined using air cathode microbial fuel cells (MFCs). Electricity was generated from all carbon sources tested, including six hexoses (d-glucose, d-galactose, d(−)-levulose (fructose), l-fucose, lrhamnose, and d-mannose), three pentoses (d-xylose, d(−)-arabinose, and d(−)-ribose), two uronic acids (d-galacturonic acid and d-glucuronic acid) and one aldonic acid (d-gluconic acid). The mixed bacterial culture, which was enriched using acetate as a carbon source, adapted well to all carbon sources tested, although the adaptation times varied from 1 to 70 h. The maximum power density obtained from these carbon sources ranged from 1240 ± 10 to 2770 ± 30 mW m −2 at current density range of 0.76–1.18 mA cm −2 . d-Mannose resulted in the lowest maximum power density, whereas d-glucuronic acid generated the highest one. Coulombic efficiency ranged from 21 to 37%. For all carbon sources tested, the relationship between the maximum voltage output and the substrate concentration appeared to follow saturation kinetics at 120 � external resistance. The estimated maximum voltage output ranged between 0.26 and 0.44 V and half-saturation kinetic constants ranged from 111 to 725 mg L −1 . Chemical oxygen demand (COD) removal was over 80% for all carbon sources tested. Results from this study indicated that lignocellulosic biomass-derived monosaccharides might be a suitable resource for electricity generation using MFC technology. © 2007 Elsevier B.V. All rights reserved.

Synthetic polypeptides containing sugar moieties can find interesting applications as drug-delivery systems or as hydrogels. Only a few studies report on the successful synthesis of sugar-based polypeptides. The aim of this study is to access a range of well-defined polypeptides carrying linear gluconoyl moieties as side-groups, including homo-polypeptides and co-polypeptides with hydrophilic and hydrophobic sequences. The strategy consisted in first preparing the polypeptide via ring-opening polymerization of N-carboxyanhydrides using either an Al-Schiff's base metal complex or a primary amine. The free amino side-groups of the polylysine units are then reacted with gluconolactone, thus leading to a main polypeptide backbone and linear sugar moieties as pendant groups. Sugar moieties have also been attached to statistical and block co-polypeptides bearing hydrophilic and hydrophobic units such as L-lysine and L-leucine, respectively. The anchoring of linear gluconoyl moieties onto poly(L-lysine) and onto...

The lipid A from nitrogen-fixing bacterial species Rhizobium sin-1 is structurally unusual due to lack of phosphates and the presence of a 2-aminogluconolactone and a very long chain fatty acid, 27-hydroxyoctacosanoic acid (27OHC28:0), moiety. This structurally unusual lipid A can antagonize TNF-alpha production by human monocytes induced by Escherichia coli LPS. To establish the relevance of the unusual long chain 27-hydroxyoctacosanoic acid for antagonistic properties, a highly convergent strategy for the synthesis of several derivatives of the lipid A of R. sin-1 has been developed. Compound 1 is a natural R. sin-1 lipid A having a 27-hydroxyoctacosanoic acid at C-2', compound 2 contains an octacosanoic acid moiety at this position, and compound 3 is modified by a short chain tetradecanoic acid. Cellular activation studies with a human monocytic cell line have shown that the octacosanoic acid is important for optimal antagonistic properties. The hydroxyl of the natural 27-hydroxyoctacosanoic moiety does, however, not account for inhibitory activity. The resulting structure-activity relationships are important for the design of compounds for the treatment of septic shock.

The electrocatalytic oxidation of d-glucosamine (2-amino-2-deoxy-d-glucose) in alkaline and neutral solutions was examined using a carbon felt electrode modified with 2 nm core sized gold nanoparticles (Au2 nm nanoparticles) and a gold plate electrode. The electrocatalytic voltammetric oxidation curves of d-glucosamine were obtained in both solutions. The voltammetric responses for the electrocatalytic oxidation at a Au2 nm nanoparticle-modified electrode in both alkaline and neutral solutions were almost the same to those at a gold plate electrode. The oxidized product was identified to be d-glucosaminic acid (2-amino-2-deoxy- d-gluconic acid) generated by the 2-electron oxidation product of d-glucosamine by electrospray ionization time-of-flight mass spectra (ESI TOF-MS). The HPLC results also indicated that the oxidation product was d-glucosaminic acid.The controlled-potential electrolysis of d-glucosamine was performed at the Au2 nm nanoparticle-modified carbon felt electrodes in both alkaline and neutral solutions. In the alkaline solution, at a potential of −0.2 V, d-glucosaminic acid was formed with a current efficiency of 100%. In the neutral solution, electrolysis at 0.4 V on d-glucosaminic acid was obtained with current efficiencies of 70%. Keywords: Electrochemistry, Gold, Oxidation, Glucosamine, Glucosaminic acid, Electrolysis

Experimental conditions for complete separation and quantification of mixtures containing lactobionic acid, sorbitol, lactose and fructose are discussed for the first time. These mixtures appear in the enzymatic bioconversion of fructose and lactose catalyzed by glucose-fructose oxidoreductase (GFOR) and glucono-delta-lactonase (GL) enzymes of Zymomonas mobilis cells. The high-performance liquid chromatography (HPLC) separation was carried out in a strong cation ion exchange resin (hydrogen form) based on a copolymer of styrene divinylbenzene (PS-DVB). A stationary phase of beta-cyclodextrin was also evaluated. An efficient separation was obtained with PS-DVB column eluted with sulfuric acid 0.450 mM solutions (pH 3.0-3.2) at 75 degrees C. The formation of lactones was observed, which is associated with the dissolution of lactobionic acid crystals; however, by dissolving the lactobionic acid crystals on alkaline calcium hydroxyde solution in equimolar ratio a single lactobionic acid chromatographic peak without lactobionolactone is obtained.

The influence of newly synthesized N -alkanoyl- N -methyllactitolamines (decanoyl [C 10 MELA], lauoroyl [C 12 MELA] and miristoyl [C 14 MELA]) on the thermotropic phase transition of phosphatidylcholine bilayer was compared with common sugar-based surfactants N -dodecyl-β- d -glucopyranoside [C12G1] and decanoyl- N -methyl glucamide [MEGA-10]. The results indicate that C n MELA are very active at the membrane surface and disturb the phospholipid bilayer structure less than commercially used MEGA-10 and C12G1.

Background Economical production of fuels and chemicals from plant biomass requires the efficient use of sugars derived from the plant cell wall. Neurospora crassa, a model lignocellulosic degrading fungus, is capable of breaking down the complex structure of the plant cell wall. In addition to cellulases and hemicellulases, N. crassa secretes lytic polysaccharide monooxygenases (LPMOs), which cleave cellulose by generating oxidized sugars—particularly aldonic acids. However, the strategies N. crassa employs to utilize these sugars are unknown. Results We identified an aldonic acid utilization pathway in N. crassa, comprised of an extracellular hydrolase (NCU08755), cellobionic acid transporter (CBT-1, NCU05853) and cellobionic acid phosphorylase (CAP, NCU09425). Extracellular cellobionic acid could be imported directly by CBT-1 or cleaved to gluconic acid and glucose by a β-glucosidase (NCU08755) outside the cells. Intracellular cellobionic acid was further cleaved to glucose 1-phosphate and gluconic acid by CAP. However, it remains unclear how N. crassa utilizes extracellular gluconic acid. The aldonic acid pathway was successfully implemented in Saccharomyces cerevisiae when N. crassa gluconokinase was co-expressed, resulting in cellobionic acid consumption in both aerobic and anaerobic conditions. Conclusions We successfully identified a branched aldonic acid utilization pathway in N. crassa and transferred its essential components into S. cerevisiae, a robust industrial microorganism. Electronic supplementary material The online version of this article (doi:10.1186/s13068-015-0303-2) contains supplementary material, which is available to authorized users.

The microbial oxidative cellulose degradation system is attracting significant research attention after the recent discovery of lytic polysaccharide mono-oxygenases. A primary product of the oxidative and hydrolytic cellulose degradation system is cellobionic acid (CbA), the aldonic acid form of cellobiose. We previously demonstrated that the intracellular enzyme belonging to glycoside hydrolase family 94 from cellulolytic fungus and bacterium is cellobionic acid phosphorylase (CBAP), which catalyzes reversible phosphorolysis of CbA into glucose 1-phosphate and gluconic acid (GlcA). In this report, we describe the biochemical characterization and the three-dimensional structure of CBAP from the marine cellulolytic bacterium Saccharophagus degradans. Structures of ligand-free and complex forms with CbA, GlcA, and a synthetic disaccharide product from glucuronic acid were determined at resolutions of up to 1.6 A. The active site is located near the dimer interface. At subsite +1, the carboxylate group of GlcA and CbA is recognized by Arg-609 and Lys-613. Additionally, one residue from the neighboring protomer (Gln-190) is involved in the carboxylate recognition of GlcA. A mutational analysis indicated that these residues are critical for the binding and catalysis of the aldonic and uronic acid acceptors GlcA and glucuronic acid. Structural and sequence comparisons with other glycoside hydrolase family 94 phosphorylases revealed that CBAPs have a unique subsite +1 with a distinct amino acid residue conservation pattern at this site. This study provides molecular insight into the energetically efficient metabolic pathway of oxidized sugars that links the oxidative cellulolytic pathway to the glycolytic and pentose phosphate pathways in cellulolytic microbes.

Allylamides of gluconic acid were synthesized by the reaction of allylamine with lactones using dimethyl formamide as a solvent. In this reaction, hydroxyl groups were protected by trimethylsilyl groups via three different pathways that connect sugar units onto the polysiloxane chains. A series of well-defined polysiloxanes with pendent sugar units were prepared by hydrosilation of the trimethylsilyl-protected allylamides with hydric polysiloxanes in the presence of the Platinum dioxide as a catalyst. The catalytic activity and selectivity were discussed in detail. All products were characterized by FT-IR, 1 H NMR, and 13 C NMR spectroscopy, respectively. Furthermore, the shapes of molecular aggregates of target polymers in water were studied by transmission electron microscopy, which reveals that the transitions of micelles- morphologies from spheres to vesicles can be controlled by adjusting hydrogen content of primary materials or by changing initial solvents.

Aqueous-core capsules with uniform polymeric shells and diameters ranging from 0.2 to 5 μm were prepared by polymerizing the interfaces of inverse emulsion microspheres. Free-radical polymerization was constrained to the interface of water-in-oil microspheres by the alternating copolymerization of hydrophobic maleate esters and hydrophilic polyhydroxy vinyl ethers, in a manner analogous to classical interfacial polycondensations. In these polymerizations, the kinetics, shell thickness, and release characteristics of the resulting aqueous-core capsules are set by the diffusion-limited alternating reaction of the oil-soluble maleate esters and water-soluble vinyl ethers.

The fungal enzyme pyranose dehydrogenase (PDH) (EC 1.1.99.29) purified to apparent homogeneity from culture media of Agaricus meleagris catalyzed the substrate-dependent C-1, C-2, C-3, C-1,3′ or C-2,3(′) (di)oxidation of a number of mono- and disaccharides with 1,4-benzoquinone as an electron acceptor. d -Ribose, d -allose, d -gulose and d -talose were oxidized to the corresponding aldonic acids. l -Arabinose was converted exclusively to 2-dehydro- l -arabinose ( l -erythro-pentos-2-ulose) whereas d -xylose underwent competing C-2 and C-3 oxidation followed by dioxidation to 2,3-didehydro- d -arabinose ( d -glycero-pentos-2,3-diulose). The major final oxidation products of maltose and cellobiose were the novel compounds 2,3′-didehydromaltose and 2,3′-didehydrocellobiose (α- and β- d -ribo-hexos-3-ulopyranosyl-(1 → 4)- d -arabino-hexos-2-ulose), formed via 2- and 3′-monooxidation intermediates. Minor concomitant (di)oxidation at C-1,(3′) to the corresponding bionic acids also took place. Maltotriose was preferentially oxidized at C-3″ of the terminal glucopyranosyl unit and at C-1 of the reducing moiety. The structures of these sugar oxidation products were established by in situ 1D and 2D NMR spectroscopy and ESI–MS. Based on HPLC analysis, conversions of (glycosyl)aldoses in non-buffered systems were nearly quantitative within 3–24 h, depending on the substrate. As the enzyme allows an easy access to highly reactive di- or tricarbonyl sugars, it might become a useful catalyst in carbohydrate chemistry.

The influence of thallium addition on the catalytic properties of palladium catalysts supported on SiO 2 in the reaction of aldoses (glucose and lactose) oxidation to aldonic acid was studied. It was found that thallium does not have any activity by itself, but acts as “promoter” for the catalytic activity and selectivity of monometallic Pd/SiO 2 catalysts. The XRD studies proved the presence of intermetallic compounds, which probably increases activity and selectivity of bimetallic catalysts in those reactions. The same interaction was found using ToF-SIMS. The TPO studies show that palladium oxidation occurs at much higher temperatures than in the case of thallium. A reaction involving bimetallic catalysts in oxidizing atmosphere at 333 K should not lead to surface oxidation of palladium and thus their deactivation.

The present work attempted to utilize xylose by converting it to an aldonic acid. In the present study, xylose was converted to xylonic acid by using commercial glucose oxidase enzyme, palladium catalysis, and microbial bioconversion. The enzyme conversion was successfully done using a commercial glucose oxidase. The microbial conversion with Gluconobactor oxydans proceeded even with the presence of a large amount of lignosulfonate. Thus obtained xylonic acid products were evaluated as a cement dispersing agent in cement and concrete tests. It was found that xylonic acid is approximately twice as effective as lignosulfonate. Xylonic acid can be effectively utilized in concrete water reducer application.

Hyperbranched poly(ethylenimine) (PEI) with amino groups or carbohydrate terminal groups have been used as support materials for metal nanoparticles (i.e., Cu, Ag, Au, and Pt) in water. Various parameters have been optimized, such as pH, concentration of the polymer in solution, and [metal ions]/[polymer] ratio in order to obtain stable metal nanoparticles with a narrow size distribution. TEM measurements revealed that particles with a diameter as low as 1.4 nm were obtained. An increase of stability was obtained after functionalization of PEI with glycidol, gluconolactone, or lactobionic acid. In the case of Pt the catalytical activity of the corresponding nanoparticles was evidenced.

A convenient method to obtain unknown chiral C2- and C3-functionalized aldono-1,4-lactone derivatives starting from l-ascorbic acid, which would be valuable in the synthesis of derivatives of various pharmacologically active agents for structure-activity studies, is described. The practicality of this approach is demonstrated by the synthesis of a series of 5,6-O-isopropylidene-2-allyl-3-keto-l-galactono-gamma-lactone and 5,6-O-isopropylidene-3-allyl-2-keto-l-galactono-gamma-lactone derivatives using the thermal Claisen rearrangement of the corresponding 3-O- and 2-O-allyl derivatives of 5,6-O-isopropylidene-l-ascorbic acid, respectively, followed by stereospecific reduction to the corresponding alcohols. The synthetic steps are shown to be efficient, and enantiospecific, and they proceed with high yields.

A surface of poly(l-lactic acid) (PLLA) was modified by coating with poly[N-p-vinylbenzyl-4-O-beta-d-galactopyranosyl-d-glucoamide] (PVLA), which was employed to improve the hepatocyte adhesion owing to its amphiphilic property and the presence of a hepatocyte recognition motif. We characterized the surface properties through water contact angle, electron spectroscopy for chemical analysis (ESCA), and scanning probe microscopy (SPM). The effect of PVLA coating on the efficiency of hepatocyte adhesion was evaluated by protein assay and optical microscopy. The surface morphology was under the influence of the concentration of PVLA coating solution and it played a critical role in hepatocyte adhesion. It was confirmed that galactose moieties in PVLA, which can bind to the asialoglycoprotein receptor (ASGPR) on hepatocytes, have a more dominant effect on hepatocyte adhesion than enhanced hydrophilicity. We suggest that the PVLA-PLLA system will be a useful method to improve hepatocyte cell seeding and adhesion onto scaffold matrices.

The indirect cathodic reduction of dispersed vat dyes CI Vat Yellow 1 and CI Vat Blue 5 was investigated by cyclic voltammetry and with batch electrolysis experiments. 0.01molL−1 solutions of the complexes Fe3‰+--gluconate and Ca2‰+-Fe3‰+--gluconate were studied. The addition of dispersed dyestuff to the mediator solution lead to a catalytic current. While the cathodic peak currents of both complexes is comparable, Fe3‰+-DGL shows higher enhancement factors, which are defined as quotient of catalytic peak current and cathodic peak current of the mediator system (Ip)c/(Ip)d. In the presence of 0.5gL−1 of dispersed vat dye enhancement factors of 1.8 were determined at scan rates of 0.005–0.010Vs−1. Galvanostatic batch reduction experiments with use of a laboratory multi-cathode cell confirmed the favourable properties of the Fe3‰+-DGL in comparison to the binuclear Ca2‰+-Fe3‰+-DGL. With use of the Fe3‰+-DGL mediator complete dyestuff reduction could be achieved. The batch reduction process was followed experimentally by photometry and redox potential measurement in the catholyte.

The standard (p∘ = 0.1 MPa) molar energies of combustion in oxygen, at T = 298.15 K, for crystalline d -, l -galactono-1,4-lactone, d -, l -gulono-1,4-lactone and l -mannono-1,4-lactone were measured by static-bomb calorimetry, by using paraffin oil as auxiliary substance and leading to the following results: d -galactono-1,4-lactone l -galactono-1,4-lactone d -gulono-1,4-lactone l -gulono-1,4-lactone l -mannono-1,4-lactone Δ c U m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −2559.09 ± 0.47 −2559.66 ± 0.48 −2561.32 ± 0.51 −2560.91 ± 0.48 −2563.43 ± 0.37 Δ c H m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −2557.85 ± 0.47 −2558.42 ± 0.48 −2560.08 ± 0.51 −2559.67 ± 0.75 −2562.19 ± 0.37 Δ f H m ∘ ( cr , 298.15 K ) / ( kJ · mol - 1 ) −1232.36 ± 0.65 −1231.79 ± 0.65 −1230.13 ± 0.65 −1230.54 ± 0.62 −1228.02 ± 0.65 ΔfusH(Tfus)/(kJ · mol−1) 35.77 ± 0.32 35.98 ± 0.06 40.13 ± 0.60 41.50 ± 0.36 36.13 ± 0.20 Tfus/K 410.32 ± 0.03 409.82 ± 0.03 459.30 ± 0.23 458.96 ± 0.05 426.52 ± 0.06 The values of standard molar enthalpies of formation in solid phase of the lactones were relationed with their molecular structures and hydrogen bonding.

A novel and efficient method for preparing 99mTc-complexes of radiopharmaceuticals has been developed by reacting [99mTc]pertechnetate with a ligand in the presence of borohydride exchange resin (BER) as a reducing agent. The latter is stable over a wide range of pH (2–11) and thus can be used with biologically active compounds without the formation of insoluble 99mTcO2 or SnO2 colloids. Since the radiolabelled complexes are produced with high radiochemical purity and labelling efficiency under milder conditions than those required for the conventional reducing agents, the latter can be replaced. The method is expected to be applicable to the preparation of 99mTc-radiopharmaceuticals. Copyright © 2004 John Wiley & Sons, Ltd.

This paper presents biodegradable polyesters prepared from gluconolactone (G) and citric acid (C) with various molar ratios of G to C, 1/4, 1/3, 1/2, 1/1, 2/1, 3/1, and 4/1. Corresponding polyesters were named as GC14, GC13, GC12, GC11, GC21, GC31, and GC41, respectively. Prepolymers, prepared at 165 °C by a melt polycondensation, were cast from tetrahydrofuran solution and postpolymerized at 180 °C for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The polyesters obtained were characterized by infrared spectroscopy, wide-angle X-ray diffraction analysis, density measurement, differential scanning calorimetry (DSC), dynamic mechanical analysis, thermomechanical analysis (TMA), and tensile test. The degree of reaction was estimated from the ratio between absorbance due to the stretching vibration of the hydroxyl group and that of the methylene group. Enzymatic degradability was performed at 37 °C in a buffer solution with Rhizop...

New saccharide polymers were synthesized via free radical polymerization. The saccharide compounds in copolymerisation reactions were 2,4,6-tri-O-acetyl-3-deoxy-D-erythro-hex-2-enono-1,5-lactone (1), (Ac-GEL 1) and 2,4,6-tri-O-benzoyl-3-deoxy-D-erythro-hex-2-enono-1,5-lactone (2), (Bz-GEL 2). These sugar monomers are easily obtained with high yield in a one step reaction from glucono-δ-lactone. They have a pyranoid structure containing an endocyclic double bond and they are electron acceptor compounds. Copolymerization reactions were carried out in solution an in substance. Copolymers with different sugar contents and low as well as high molecular weights were obtained. The structures and the compositions of the soluble saccharide polymers were established by elemental analysis, polarimetry, FTIR spectroscopy, 1 H an 13 C NMR spectroscopy. Some characteristic properties, e.g., molecular weight, optical rotation and copolymerization parameters are reported.

A stereoseletive synthesis of 2,7-anhydrosialic acid derivative 18 was achieved from d-glucono-delta-lactone. A highly syn-selective addition of Grignard reagent to theN-benzylimine 8 served as a key step.

New carbohydrate-functional siloxanes (CHFS) have successfully been synthesized by acid-catalyzed transacetalation between unprotected methyl gluconyl glycinate (MGG) as a hydrophilic component and...