Search

This publication reports a facile and convenient preparation of tri-O-acetyl-glucopyranoses, derived from the corresponding 2-deoxyaminosugar, where the vicinal anomeric and C2 positions are decorated by azido and (thio)ureido groups, respectively. This double functionalization leads to an inherently chiral core incorporating the versatile azido and (thio)ureido linkages prone to further manipulation. The latter also provides a structural element for hydrogen-bonded donor-acceptor (HB-DA) sites, which are of immense value in organocatalytic pursuits. A computation-aided conformational analysis unveils the landscape of available conformers and their relative stability. N-aryl (thio)ureas bearing substituents at ortho positions exist as mixtures of M- and P-atropisomeric conformers. [ABSTRACT FROM AUTHOR]

The LebLea heptasaccharide is a tumor-associated carbohydrate antigen that was isolated from the human colonic adenocarcinoma cell line Colo205 and is a good target for the development of anti-cancer immunotherapeutics. However, it displays on its reducing end the Leb tetrasaccharide: α-l-Fucp-(1→2)-β-d-Galp-(1→3)-[α-l-Fucp-(1→4)]-d-GlcNAcp and the H-type 1 (H-1 antigen) trisaccharide: α-l-Fucp-(1→2)-β-d-Galp-(1→3)-d-GlcNAcp that are also found on noncancerous tissues. To discover analogues or fragments of LebLea that could be used as immunotherapeutics while not triggering immune responses against Leb and the H-1 antigen, we have synthesized the Leb tetrasaccharide hexyl glycoside and the Leb and H-1 antigens aminohexyl glycosides to be used in ELISA experiments. We describe an improved preparation of the 6-O-benzyl-2,3,4-tri-O-acetyl-α-d-galactopyranosyl bromide in neutral conditions and demonstrate the importance of appropriately "matching" the reactivity of acceptors with that of glycosyl donors. Mono- and di-fucosylation of a disaccharide diol acceptor with per-benzylated thioethyl fucoside activated in situ with bromine and under halide ion catalysis is described and our results are compared to literature reports. We observed that our fucosylation reactions required higher equivalents of fucosyl donor and extended reaction times than previously reported. We propose that the protecting groups on the galactosyl unit led to a reduced reactivity of the acceptor. The protected intermediates were converted to 6-azido hexyl glycosides and submitted to dissolving metal conditions to give 6-aminohexyl glycosides. We also prepared the n-hexyl tetrasaccharide glycoside Leb that will be used as a soluble antigen in competitive ELISA experiments. [ABSTRACT FROM AUTHOR]

Proteus mirabilis is a pathogenic Gram‐negative bacterium that causes several kinds of infections in human beings. Herein, we present the first total synthesis of the O‐antigen tetrasaccharide repeating unit of P. mirabilis OC (CCUG 10702) serogroup O75 with an aminoethyl linker appended at the reducing end. The tetrasaccharide comprising D‐glucosamine, L‐rhamnose, D‐galactose and D‐galactosamine with a key (1→4)‐α‐glycosidic linkage between D‐galactose and L‐rhamnose was assembled by three stepwise [1+1+1+1], [1+2+1] and [2+2] assembly approaches and one one‐pot [1+2+1] assembly. The respective routes provided the tetrasaccharide in yields of 23 %, 18 %, 20 %, and 26 % from suitably protected monosaccharide building blocks. [ABSTRACT FROM AUTHOR]

This publication reports a facile and convenient preparation of tri-O-acetyl-glucopyranoses, derived from the corresponding 2-deoxyaminosugar, where the vicinal anomeric and C2 positions are decorated by azido and (thio)ureido groups, respectively. This double functionalization leads to an inherently chiral core incorporating the versatile azido and (thio)ureido linkages prone to further manipulation. The latter also provides a structural element for hydrogen-bonded donor-acceptor (HB-DA) sites, which are of immense value in organocatalytic pursuits. A computation-aided conformational analysis unveils the landscape of available conformers and their relative stability. N-aryl (thio)ureas bearing substituents at ortho positions exist as mixtures of M- and P-atropisomeric conformers.

[Display omitted] • Covalent inhibitors are gaining renewed attention in drug discovery, however, there are very few examples of antifungal covalent drugs. • Aromatic glycoconjugates (AGCs), some with reactive functional groups such as acryloyl and vinyl sulfone moieties, were synthesised. • Their fungicidal efficacy against fungal pathogens of the Candida spp was investigated. • The ability of active galactose derivatives to crosslink nucleophilic side chains was assessed in model reactions. Covalent drugs are becoming increasingly attractive in drug discovery, as they can enhance potency and selectivity for their molecular targets. Covalent inhibitors have been investigated for several therapeutic applications, including anti-cancer and anti-infection agents. However, there are only a few examples of covalent inhibitors targeting fungal pathogens. We have previously reported aromatic glycoconjugates (AGCs) capable of inhibiting the adhesion of Candida albicans to buccal epithelial cells. In this work, we synthesize novel derivatives of the AGCs to which we have added reactive functional groups, such as acryloyl and vinyl sulfones, and investigated their antifungal efficacy against Candida spp. Although the compounds were ineffective at clinically relevant concentrations, we found that some of the galactose derivatives featuring reactive groups were amongst the most active, so their ability to crosslink nucleophilic side chains was assessed in model reactions. [ABSTRACT FROM AUTHOR]

Carbohydrates are structurally complex but functionally important biomolecules. Therefore, they have been challenging but attractive synthetic targets. While substantial progress has been made on advancing chemical glycosylation methods, incorporating enzymes into carbohydrate synthetic schemes has become increasingly practical as more carbohydrate biosynthetic and metabolic enzymes as well as their mutants with synthetic application are identified and expressed for preparative and large-scale synthesis. Chemoenzymatic strategies that integrate the flexibility of chemical derivatization with enzyme-catalyzed reactions have been extremely powerful. Briefly summarized here are our experiences on developing one-pot multienzyme (OPME) systems and representative chemoenzymatic strategies from others using glycosyltransferase-catalyzed reactions for synthesizing diverse structures of oligosaccharides, polysaccharides, and glycoconjugates. These strategies allow the synthesis of complex carbohydrates including those containing naturally occurring carbohydrate postglycosylational modifications (PGMs) and non-natural functional groups. By combining these srategies with facile purification schemes, synthetic access to the diverse space of carbohydrate structures can be automated and will not be limited to specialists.

Cucumber is one of the most widely cultivated greenhouse vegetables, and its quality and yield are threatened by drought stress. Studies have shown that carbon dioxide concentration ([CO2]) enrichment can alleviate drought stress in cucumber seedlings; however the mechanism of this [CO2] enrichment effect on root drought stress is not clear. In this study, the effects of different drought stresses (simulated with 0, 5% and 10% PEG 6000, i.e., no, moderate, and severe drought stress) and [CO2] (400 μmol·mol−1 and 800 ± 40 μmol·mol−1) on the cucumber seedling root proteome were analyzed using the tandem mass tag (TMT) quantitative proteomics method. The results showed that after [CO2] enrichment, 346 differentially accumulating proteins (DAPs) were found only under moderate drought stress, 27 DAPs only under severe drought stress, and 34 DAPs under both moderate and severe drought stress. [CO2] enrichment promoted energy metabolism, amino acid metabolism, and secondary metabolism, induced the expression of proteins related to root cell wall and cytoskeleton metabolism, effectively maintained the balance of protein processing and degradation, and enhanced the cell wall regulation ability. However, the extent to which [CO2] enrichment alleviated drought stress in cucumber seedling roots was limited under severe drought stress, which may be due to excessive damage to the seedlings. [ABSTRACT FROM AUTHOR]

Duckweeds are fast-growing aquatic plants suitable for bioenergy due to fermentable-rich biomass with low lignin and unique cell wall. The plant cell wall is built from pathways of nucleotide sugar genes that culminate in cell wall synthesis and deposition. Therefore, understanding these pathways by mapping the genes involved and their expression would be necessary for developing tools to improve bioenergy production. In this work, the genes associated with the NDP-sugar pathway (de novo and salvage) were mapped and correlated to the chemical characterization of the giant duckweed (Spirodela polyrhiza) cell wall. This plant biomass has been characterized as having 3% starch, 49% soluble sugars, 40% cell wall, and 8% non-measured compounds. The cell walls are synthesized by the NDP-sugar pathway and represent a significant carbon sink. This sink results from the action of proteins encoded by 190 orthologs of the 38 targets of the NDP-sugar pathway, of which 49 are starch and sucrose-related, 54 pectins-related, 65 hemicellulose-related, and 23 cellulose-related. Chemical analysis of the cell wall revealed 49% pectins, 23% hemicellulose, and 10% cellulose. These carbohydrates can potentially provide biorefinery as adjuvants, cosmetics, food additives, stabilizers, gelling agents, and principally as biofuels. [ABSTRACT FROM AUTHOR]

A cationic gold(I)-catalyzed O-glycosylation method involving the use of glycosyl S-3-butynyl thiocarbonate donors has been developed. It was found that glycosyl S-3-butynyl thiocarbonates are orthogonal to regular phenyl thioglycoside donors. The utilization of this method was demonstrated in the synthesis of a trisaccharide. [ABSTRACT FROM AUTHOR]

• L352M alters donor and acceptor subsites, causing a domino effect in the active site. • R69 is confirmed as a key determinant of the transglycosylation/hydrolysis partition. • Active site flexibility contributes to the transglycosylation/hydrolysis equilibrium. • N216W leads to a hydrophobic platform for better acceptor binding. • A complex interplay of mutational effects procures better transglycosylase activity. The use of retaining glycoside hydrolases as synthetic tools for glycochemistry is highly topical and the focus of considerable research. However, due to the incomplete identification of the molecular determinants of the transglycosylation/hydrolysis partition (t/h), rational engineering of retaining glycoside hydrolases to create transglycosylases remains challenging. Therefore, to understand better the factors that underpin transglycosylation in a GH51 retaining α- l -arabinofuranosidase from Thermobacillus xylanilyticus, the investigation of this enzyme's active site was pursued. Specifically, the properties of two mutants, F26L and L352M, located in the vicinity of the active site are described, using kinetic and 3D structural analyses and molecular dynamics simulations. The results reveal that the presence of L352M in the context of a triple mutant (also containing R69H and N216W) generates changes both in the donor and acceptor subsites, the latter being the result of a domino-like effect. Overall, the mutant R69H-N216W-L352M displays excellent transglycosylation activity (70 % yield, 78 % transfer rate and reduced secondary hydrolysis of the product). In the course of this study, the central role played by the conserved R69 residue was also reaffirmed. The mutation R69H affects both the catalytic nucleophile and the acid/base, including their flexibility, and has a determinant effect on the t / h partition. Finally, the results reveal that increased loop flexibility in the acceptor subsites creates new interactions with the acceptor, in particular with a hydrophobic binding platform composed of N216W, W248 and W302. [ABSTRACT FROM AUTHOR]

β-Glucan phosphorylases are carbohydrate-active enzymes that catalyze the reversible degradation of β-linked glucose polymers, with outstanding potential for the biocatalytic bottom-up synthesis of β-glucans as major bioactive compounds. Their preference for sugar phosphates (rather than nucleotide sugars) as donor substrates further underlines their significance for the carbohydrate industry. Presently, they are classified in the glycoside hydrolase families 94, 149, and 161 (www.cazy.org). Since the discovery of β-1,3-oligoglucan phosphorylase in 1963, several other specificities have been reported that differ in linkage type and/or degree of polymerization. Here, we present an overview of the progress that has been made in our understanding of β-glucan and associated β-glucobiose phosphorylases, with a special focus on their application in the synthesis of carbohydrates and related molecules. Key points: • Discovery, characteristics, and applications of β-glucan phosphorylases. • β-Glucan phosphorylases in the production of functional carbohydrates. [ABSTRACT FROM AUTHOR]

Epimerization of sugar nucleotides is central to the structural diversification of monosaccharide building blocks for cellular biosynthesis. Epimerase applicability to carbohydrate synthesis can be limited, however, by the high degree of substrate specificity exhibited by most sugar nucleotide epimerases. Here, we discovered a promiscuous type of CDP-tyvelose 2-epimerase (TyvE)-like enzyme that promotes C-2 epimerization in all nucleotide (CDP, UDP, GDP, ADP, and TDP)-activated forms of d-glucose. This new epimerase, originating from Thermodesulfatator atlanticus, is a functional homodimer that contains one tightly bound NAD+/subunit and shows optimum activity at 70°C and pH 9.5. The enzyme exhibits a kcat with CDP-d-glucose of ∼1.0 min−1 (pH 7.5 and 60°C). To characterize the epimerase kinetically and probe its substrate specificity, we developed chemoenzymatic synthesis for CDP-d-mannose, CDP-6-deoxy-d-glucose, CDP-3-deoxy-d-glucose, and CDP-6-deoxy-d-xylo-hexopyranos-4-ulose. Attempts to obtain CDP-d-paratose and CDP-d-tyvelose were not successful. Using high-resolution carbohydrate analytics and in situ nuclear magnetic resonance (NMR) to monitor the enzymatic conversions (60°C and pH 7.5), we show that the CDP-d-mannose/CDP-d-glucose ratio at equilibrium is 0.67 (±0.1), determined from the kinetic Haldane relationship and directly from the reaction. We further show that deoxygenation at sugar C-6 enhances the enzyme activity 5-fold compared to CDP-d-glucose, whereas deoxygenation at C-3 renders the substrate inactive. Phylogenetic analysis places the T. atlanticus epimerase into a distinct subgroup within the sugar nucleotide epimerase family of SDRs (short-chain dehydrogenases/reductases), for which the current study now provides functional context. Collectively, our results expand an emerging toolbox of epimerase-catalyzed reactions for sugar nucleotide synthesis. IMPORTANCE Epimerases of the sugar nucleotide-modifying class of enzymes have attracted considerable interest in carbohydrate (bio)chemistry for the mechanistic challenges and the opportunities for synthesis involved in the reactions catalyzed. The discovery of new epimerases with an expanded scope of sugar nucleotide substrates used is important to promote mechanistic inquiry and can facilitate the development of new enzyme applications. Here, a CDP-tyvelose 2-epimerase-like enzyme from Thermodesulfatator atlanticus is shown to catalyze sugar C-2 epimerization in CDP-glucose and other nucleotide-activated forms of d-glucose. The reactions are new to nature in the context of enzymatic sugar nucleotide modification. The current study explores the substrate scope of the discovered C-2 epimerase and, based on modeling, suggests structure-function relationships that may be important for specificity and catalysis. [ABSTRACT FROM AUTHOR]

Despite their broad application potential, the widespread use of β-1,3-glucans has been hampered by the high cost and heterogeneity associated with current production methods. To address this challenge, scalable and economically viable processes are needed for the production of β-1,3-glucans with tailorable molecular mass distributions. Glycoside phosphorylases have shown to be promising catalysts for the bottom-up synthesis of β-1,3-(oligo)glucans since they combine strict regioselectivity with a cheap donor substrate (i.e., α-glucose 1-phosphate). However, the need for an expensive priming substrate (e.g., laminaribiose) and the tendency to produce shorter oligosaccharides still form major bottlenecks. Here, we report the discovery and application of a thermostable β-1,3-oligoglucan phosphorylase originating from Anaerolinea thermophila ( At βOGP). This enzyme combines a superior catalytic efficiency toward glucose as a priming substrate, high thermostability, and the ability to synthesize high molecular mass β-1,3-glucans up to DP 75. Coupling of At βOGP with a thermostable variant of Bifidobacterium adolescentis sucrose phosphorylase enabled the efficient production of tailorable β-1,3-(oligo)glucans from sucrose, with a near-complete conversion of >99 mol %. This cost-efficient process for the conversion of renewable bulk sugar into β-1,3-(oligo)glucans should facilitate the widespread application of these versatile functional fibers across various industries.

The (chemo-)enzymatic synthesis of oligosaccharides has been hampered by the lack of appropriate enzymatic tools with requisite regio- and stereo-specificities. Engineering of carbohydrate-active enzymes, in particular targeting the enzyme active site, has notably led to catalysts with altered regioselectivity of the glycosylation reaction thereby enabling to extend the repertoire of enzymes for carbohydrate synthesis. Using a collection of 22 mutants of ΔN123-GBD-CD2 branching sucrase, an enzyme from the Glycoside Hydrolase family 70, containing between one and three mutations in the active site, and a lightly protected chemically synthesized tetrasaccharide as an acceptor substrate, we showed that altered glycosylation product specificities could be achieved compared to the parental enzyme. Six mutants were selected for further characterization as they produce higher amounts of two favored pentasaccharides compared to the parental enzyme and/or new products. The produced pentasaccharides were shown to be of high interest as they are precursors of representative haptens of Shigella flexneri serotypes 3a, 4a and 4b. Furthermore, their synthesis was shown to be controlled by the mutations introduced in the active site, driving the glucosylation toward one extremity or the other of the tetrasaccharide acceptor. To identify the molecular determinants involved in the change of ΔN123-GBD-CD2 regioselectivity, extensive molecular dynamics simulations were carried out in combination with in-depth analyses of amino acid residue networks. Our findings help to understand the inter-relationships between the enzyme structure, conformational flexibility and activity. They also provide new insight to further engineer this class of enzymes for the synthesis of carbohydrate components of bacterial haptens. [ABSTRACT FROM AUTHOR]

[Display omitted] A 9-step synthetic route to a protected form of the C3-epimer of virenose from d -fucose is described. C3- epi -virenose is the carbohydrate unit of the bioactive polyketide elsamicin B and part of the carbohydrate unit of elsamicin A. The developed route enabled preparation of anomerically activated forms of this unique C6-deoxy sugar, including derivatives with 1-acetyl, 1-acetylthio, 1-trichloroacetimidate, 1-bromo, and 1-fluoro substituents. [ABSTRACT FROM AUTHOR]

A novel synthesis of 1,6-anhydro-N-acetylmuramic acid is described, which proceeds in only five steps from the cheap starting material N-acetylglucosamine. This efficient synthesis should enable future studies into the importance of 1,6-anhydromuramic acid in bacterial cell wall recycling processes.

Thiamine is an essential cofactor in several enzymatic reactions for all living organisms. Animals cannot synthesize thiamine and depend on their diet. Enhancing the content of thiamine is one of the most important goals of plant breeding to solve the thiamine deficiency associated with the low-thiamin staple crops. In this study, a Glycinemaxpalegreenleaf 1 (Gmpgl1) mutant was isolated from the EMS mutagenized population of soybean cultivar, Williams 82. Map-based cloning of the GmPGL1 locus revealed a single nucleotide deletion at the 292th nucleotide residue of the first exon of Glyma.10g251500 gene in Gmpgl1 mutant plant, encoding a thiamine thiazole synthase. Total thiamine contents decreased in both seedlings and seeds of the Gmpgl1 mutant. Exogenous application of thiazole restored the pale green leaf phenotype of the mutant. The deficiency of thiamine in Gmpgl1 mutant led to reduced activities of the pyruvate dehydrogenase (PDH) and pyruvate decarboxylase (PDC), and decreased contents of six amino acids as compared to that in the wild type plants. These results revealed that GmPGL1 played an essential role in thiamine thiazole biosynthesis.

Thiamine is an essential cofactor in several enzymatic reactions for all living organisms. Animals cannot synthesize thiamine and depend on their diet. Enhancing the content of thiamine is one of the most important goals of plant breeding to solve the thiamine deficiency associated with the low-thiamin staple crops. In this study, a Glycine max pale green leaf 1 (Gmpgl1) mutant was isolated from the EMS mutagenized population of soybean cultivar, Williams 82. Map-based cloning of the GmPGL1 locus revealed a single nucleotide deletion at the 292th nucleotide residue of the first exon of Glyma.10g251500 gene in Gmpgl1 mutant plant, encoding a thiamine thiazole synthase. Total thiamine contents decreased in both seedlings and seeds of the Gmpgl1 mutant. Exogenous application of thiazole restored the pale green leaf phenotype of the mutant. The deficiency of thiamine in Gmpgl1 mutant led to reduced activities of the pyruvate dehydrogenase (PDH) and pyruvate decarboxylase (PDC), and decreased contents of six amino acids as compared to that in the wild type plants. These results revealed that GmPGL1 played an essential role in thiamine thiazole biosynthesis. [ABSTRACT FROM AUTHOR]

BACKGROUND Readily available feedstock and biocompatibility make carbohydrate‐based hydrogels promising materials for biomedical applications. However, carbohydrate‐based crosslinkers are rather underexplored when compared with crosslinkers derived from fossil resources. In this study, novel fully bio‐based hydrogels derived from enzymatically produced d‐fructose and d‐glucose methacrylate monomers were synthesized with different amounts of d‐fructose dimethacrylate crosslinker. RESULTS: The use of a carbohydrate‐based crosslinker endows hydrogels with high swelling coefficients, up to 2400%, and superior mechanical resistance (compressive modulus up to 9.5 kPa with a maximum stress up to 50 kPa) compared with conventional crosslinkers based on fossil resources. Hydrogels shape and crosslinking density influences hydrogel morphology, swelling behavior and mechanical resistance. Moreover, hydrogels presented cell viability, biodegradability and hydrolysis‐resistance over a wide range of pH. CONCLUSION: The use of a highly hydrophilic crosslinker based on carbohydrate for hydrogels synthesis enables the use of high crosslinker concentration, which improves mechanical properties, however with minor loss of the water swelling capacity, compared with conventional fossil‐based crosslinkers. This is an important advantage over conventional crosslinkers based on fossil resources. Moreover, slab hydrogels hold higher stress under compression–decompression cycles, and present higher resistance to hydrolysis in basic medium due to the thicker pore walls than cylindrical ones. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Functionalized carbohydrates and especially functionalized C -glycosides are useful intermediates for the synthesis of complex carbohydrates of interest. In this paper, we describe the synthesis of C -azidopropylglucopyranosides and give a full account of their regioselective acylation and alkylation. Alkylation of these C -glucosyl compounds containing 1,2- trans -diol, namely 2- and 3-OH were first optimized with benzyl bromide. The reaction has then been extended to various electrophiles thus providing 3- O -substituted C -glucosyl compounds. These results are one of the first examples of regioselective alkylation with functionalized electrophiles on glycosyl compounds featuring a trans -vicinal diol. Furthermore, we describe some results obtained during regioselective deprotection of 4,6- O -benzylidene protecting group. This work opens the way to the synthesis of complex carbohydrate derivatives. Image 1 • Efficient synthesis of C -azidopropylglucopyranosides. • Regioselective alkylation of C -glucopyranosides. • Access to value-added C -glycosyl derivatives. [ABSTRACT FROM AUTHOR]

Naturally colored cotton (Gossypium hirsutum L.) fibers are commercially valuable, but low fiber quality limits their use. This study investigates changes in enzymes' activities and substance contents involved in carbohydrate synthesis to provide a theoretical basis for improving colored cotton fiber quality. Brown cotton Xiangcaimian 2, green cotton Wanmian 39, and white cotton Sumian 9 (control) were used. Fiber cellulose accumulation for Xiangcaimian 2 and Wanmian 39 were lower than the control. Cellulose content was simulated by Richards' equation (R2 > 0.999) and follows an "S" pattern--initial slow accumulation 0-10 d post anthesis (DPA), then rapid 10-40 DPA, then slow 40-50 DPA. Maximum accumulation, the cumulative rate parameter, and maximum cumulative rate for cellulose of colored cotton were all lower for control. Further analysis showed SPAD chlorophyll meter readings, soluble sugar content, leaf sucrose invertase activity, adenosine triphosphatase, sucrose synthase, and uridine diphosphate glucose pyrophosphorylase (UDPG-PPase) activities in colored fiber were lower than control. Results suggest insufficient nutrients for boll and fiber development, resulting in lower fiber quality and boll dry weight in colored cotton. Sucrose synthase and UDPG-PPase activities in colored fiber were significantly correlated with fiber maturation (r = 0.884*, r = 0.914*) and fiber strength (r = 0.895*, r = 0.935*), indicating lower metabolite and enzyme activities in colored cotton reduced fiber quality. Therefore, it appears improving colored cotton fiber quality may require selection efforts to increase photosynthetic capacity in leaves and transportation capacity of carbohydrates in the boll to supply more nutrient during fiber development. [ABSTRACT FROM AUTHOR]

Dystroglycan is a major non‐integrin adhesion complex that connects the cytoskeleton to the surrounding basement membranes, thus providing stability to skeletal muscle. In Vertebrates, hypoglycosylation of α‐dystroglycan has been strongly linked to muscular dystrophy phenotypes, some of which also show variable degrees of cognitive impairments, collectively termed dystroglycanopathies. Only a small number of mutations in the dystroglycan gene, leading to the so called primary dystroglycanopathies, has been described so far, as opposed to the ever‐growing number of identified secondary or tertiary dystroglycanopathies (caused by genetic abnormalities in glycosyltransferases or in enzymes involved in the synthesis of the carbohydrate building blocks). The few mutations found within the autonomous N‐terminal domain of α‐dystroglycan seem to destabilise it to different degrees, without influencing the overall folding and targeting of the dystroglycan complex. On the contrary other mutations, some located at the α/β interface of the dystroglycan complex, seem to be able to interfere with its maturation, thus compromising its stability and eventually leading to the intracellular engulfment and/or partial or even total degradation of the dystroglycan uncleaved precursor. [ABSTRACT FROM AUTHOR]

We recently developed a novel chiral N‐heterocyclic carbene (NHC) catalyzed dynamic kinetic enantioselective acylation (DKEA) and dynamic kinetic diastereoselective acylation (DKDA) of Achmatowicz rearrangement products to generate useful intermediates for the further synthesis of carbohydrates. In this update, we describe a divergent NHC catalytic strategy for the stereoselective preparation of all four isomers starting from a common racemic precursor. The present report provides easy access to diverse optically pure dihydropyranones. [ABSTRACT FROM AUTHOR]

The bleomycins (BLMs) are known antitumor antibiotics composed of the tumoricidal and tumor seeking domains. The peptide structure of BLMs is responsible for the cytotoxicity by selective oxidative cleavage of DNA (and RNA), while the tumor cell selectivity and internalization resides in the disaccharide moiety (i.e. BLM disaccharide). This has prompted researchers to utilize BLM disaccharide and its derivatives as constituents for the selective recognition of tumor cells, which may find further applications as new tumor imaging tools or drug delivery vehicles. In the present study a high yielding synthesis of an alkyne modified BLM disaccharide precursor that may be used as a useful agent for the click conjugation, its conversion to a 18F‐labeled radiotracer, and preliminary in vivo PET imaging studies of the tracer with breast cancer (MCF‐7) xenograft mouse models are described. An alkyne modified bleomycin disaccharide has been synthesized from diacetone‐α‐d‐glucose and converted to a 18F radiotracer. Preliminary in vivo‐PET imaging studies has been described. [ABSTRACT FROM AUTHOR]

Diabetes care during exercise frequently requires interruptions to activity and adds extra challenges particularly for young individuals with type 1 diabetes (T1D). This study investigated the use of a carbohydrate (CHO) intake algorithm based on continuous glucose monitoring (CGM) trends during physical activity. Children with T1D diagnosed for >1 year, ages 8-12 years, with a glycated hemoglobin of <10% were recruited into a randomized crossover study. They attended two similar mornings of fun-based physical activity and adhered to either a CHO intake algorithm based on CGM trends (intervention) or to standard exercise guidelines (consumption of 0.5 g CHO/kg/h when glucose <8 mmol/L) (control). Outcome measures included events such as exercise interruptions, CHO intake, and hypoglycemia events and percentage time spent in different sensor glucose ranges. Fourteen children completed the study. No episodes of significant hypoglycemia (sensor glucose level <3.0 mmol/L) occurred in either arm. Mean CHO intake was the same in both arms, 0.3 ± 0.2 g/kg/h. However, the intervention algorithm resulted in fewer CHO intake events per day: rate [95% confidence interval] 2.4 [1.6-2.3] versus 0.9 [0.4-1.5], P < 0.001, and exercise interruptions: 7.2 [5.9-8.8] versus 1.4 [0.8-2.1], P < 0.001, compared with control. There was no evidence of a difference in percentage time in range (3.9-10 mmol/L) and percentage time spent high between study arms. Both control and intervention protocols prevented significant hypoglycemia. Using a CHO intake algorithm based on CGM trends resulted in fewer CHO intake events and fewer interruptions to exercise. Use of this algorithm may reduce the burden of diabetes management with potential to facilitate activity in young people with T1D. [ABSTRACT FROM AUTHOR]

BACKGROUND The sphingan WL produced by Sphingomonas sp. WG has great application potential in the food, ink and other industries. To discover optimal culture conditions for WL production, a gradual optimization method including one‐factor design, Plackett‐Burman design and response surface methodology was employed. Furthermore, the possible reason for the enhancement in WL production was analysed by detecting the gene expression levels in WL biosynthesis using quantitative real‐time PCR. RESULTS: The results showed that the optimal conditions are as follows: seed age, 15–18 h; incubation time, 72 h; inoculum size, 5%; loading volume, 50 mL of medium in 250‐mL shaking flasks; shaking speed, 175 rpm; initial pH of medium, 7.0; and incubation temperature, 32.5°C. WL production was mainly dependent on the concentration of glucose and yeast extract. The statistically optimized culture medium consisted of 72.40 g L−1 glucose, 3.58 g L−1 yeast extract, 3.00 g L−1 K2HPO4, 0.10 g L−1 MgSO4, and 0.10 g L−1 ZnSO4. Interestingly, a high WL production of 39.95 g L−1, 2.37‐fold the initial production (16.82 g L−1), was obtained, which was due to the higher expression level of WL‐related enzymes under these optimized conditions. CONCLUSIONS: This study provides useful fundamental information for the development of an efficient process for large‐scale WL production. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Xylobiose sequestration in a helical aromatic oligoamide capsule was evidenced by circular dichroism, NMR spectroscopy, and crystallography. The preparation of the 5 kDa oligoamide sequence was made possible by the transient use of acid‐labile dimethoxybenzyl tertiary amide substituents that disrupt helical folding and prevent double helix formation. Binding of other disaccharides was not detected. Crystallographic data revealed a complex composed of a d‐xylobiose α anomer and two water molecules accommodated in the right‐handed helix. The disaccharide was found to adopt an unusual all‐axial compact conformation. A dense network of 18 hydrogen bonds forms between the guest, the cavity wall, and the two water molecules. [ABSTRACT FROM AUTHOR]

Abstract A general and highly selective method for the synthesis of carbohydrate-derived ( Z )-vinyl halides and silanes is described. This reaction takes place through a β-elimination process of sugar-derived α-halomethylcarbinol acetates promoted by samarium diiodide. Starting materials have been easily prepared in two steps consisting in an initial addition of halomethyllithium compounds to the corresponding galactose-derived aldehyde, followed by acetylation. A mechanism that explains both the formation of ( Z )-vinyl derivatives and its selectivity is proposed. Finally, the synthetic usefulness of these compounds has been applied in cross-coupling reactions with ethynyl benzene towards the formation of selected enyne derivatives. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

We have described CsF-catalyzed trifluoromethylation of heteroaromatic aldehydes at room temperature to afford trifluoromethyl group containing alcohols in very good yields. Using catalytic amount of CsF (0.2 eq.) in toluene, trifluoromethylated products were achieved in good yields at rt. The substrate scope has been exemplified by a large number of substrates. As an application, iodo etherification/cyclization has also been demonstrated for the synthesis of trifluoromethyl pyrano[4,3- b ]quinoline from o-alkynyltrifluoro methyl alcohol, in very good yield. [ABSTRACT FROM AUTHOR]

Despite the important advances in chemical and chemoenzymatic synthesis of glycans, access to large quantities of complex natural glycans remains a major impediment to progress in Glycoscience. Here we report a large-scale preparation of N-glycans from a kilogram of commercial soy proteins using oxidative release of natural glycans (ORNG). The high mannose and paucimannose N-glycans were labeled with a fluorescent tag and purified by size exclusion and multidimensional preparative HPLC. Side products are identified and potential mechanisms for the oxidative release of natural N-glycans from glycoproteins are proposed. This study demonstrates the potential for using the ORNG approach as a complementary route to synthetic approaches for the preparation of multi-milligram quantities of biomedically relevant complex glycans. [ABSTRACT FROM AUTHOR]

The biomass production and changes in biochemical composition of a locally isolated microalga ( Chlorella sp.) were investigated in autotrophic, mixotrophic and heterotrophic conditions, using glucose or glycerol as carbon sources and municipal wastewater as the growth medium. Both standard methods and Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) analysis of data acquired by Fourier-transform IR (FTIR) spectrometry showed that autotrophic and mixotrophic conditions promoted carbohydrate accumulation, while heterotrophic conditions with glycerol resulted in the highest lipid content and lowest carbohydrate content. Heterotrophic conditions with glycerol as a carbon source also resulted in high oleic acid (18:1) contents and low linolenic acid (18:3) contents, and thus increasing biodiesel quality. The results also show the utility of MCR-ALS for analyzing changes in microalgal biochemical composition. [ABSTRACT FROM AUTHOR]

A microbioreactor immobilized with a synthase-type mutant enzyme, Endo-M-N175Q (glycosynthase) of endo-β- N -acetylglucosaminidase derived from Mucor hiemalis (Endo-M), was constructed and used for glycoconjugate synthesis. The transglycosylation was performed with a reaction mixture containing an oxazoline derivative of sialo complex-type glycoside (SG), which was prepared from a sialo complex-type glycopeptide SGP derived from hen egg yolk, as a glycosyl donor and N -Fmoc- N -acetylglucosaminyl- l -asparagine [Fmoc-Asn(GlcNAc)-OH] as an acceptor. The reaction mixture was injected into a glycosynthase microbioreactor at a constant flow rate. Highly efficient and nearly stoichiometric transglycosylation occurred in the microbioreactor, and the transglycosylation product was eluted from the other end of the reactor. The glycosynthase microbioreactor was stable and could be used repeatedly for a long time. [ABSTRACT FROM AUTHOR]

The aim is to determine the watersoluble carbohydrates (WSC) content of collections accessions of perennial ryegrass, cocksfoot, tall, meadow and red fescue and to make the selection. During the period 2015-2017 in the IFC-Pleven three collections were studied on leached black soil, rain fed conditions, by block method in 2 repetitions a total of 35 accessions, each of with 50 individual plants: perennial ryegrass - 21 (15 varieties and 6 ecotypes, 11 tetraploids and 10 diploids, from Bulgaria, Belgium, Romania and China); fescue - 8 (3 - tall, 3 - red and 2 meadow, form them 5 varieties and 3 ecotypes, from Bulgaria and Romania); cocksfoot - 6 (3 varieties and 3 ecotypes from Bulgaria and Romania). The WSC content was determined by Ermakov et al. (1987) and average, minimum, maximum values, standard deviations by regrowths and years, and total mean for the collections. According to Frances and Kannenberg (1978) the breeding assеssment was done by genotypes distribution against the collections average values for WSC and coefficient of variation. It was found that WSC content varied according to the plant species, genotype (variety or ecotype, ploidy level, group of maturity) and seasonal differences (regrowths and years), also growing conditions. The highest WSC content was measured in perennial ryegrass, followed by fescues and the lowest in cocksfoot. The perennial ryegrass genotypes: Meltador, Melverde, Meracoli, Melpetra, Harmoniya and Ravnogor with increased WSC content above year average value for the collection during the two years of the study were selected, as the tetrploid varieties had higher WSC content. The cocksfoot genotypes with higher WSC content above collection average were selected: Dabrava and BGR 1120. The WSC content in the fescue occupies an intermediate position between the perennial ryegrass and the cocksfoot and genotypes of reed and red fescue with a higher content than the average annual value for WSC of the collection were selected: Adela, Atoluka и Ravnogor. [ABSTRACT FROM AUTHOR]

Advanced vibrational molecular spectroscopy has been developed as a rapid and non-destructive tool to reveal intrinsic molecular structure conformation of biological tissues. However, this technique has not been used to systematically study flaking induced structure changes at a molecular level. The objective of this study was to use vibrational molecular spectroscopy to reveal association between steam flaking induced CHO molecular structural changes in relation to grain CHO fractionation, predicted CHO biodegradation and biodigestion in ruminant system. The Attenuate Total Reflectance Fourier-transform Vibrational Molecular Spectroscopy (ATR-Ft/VMS) at SRP Key Lab of Molecular Structure and Molecular Nutrition, Ministry of Agriculture Strategic Research Chair Program (SRP, University of Saskatchewan) was applied in this study. The fractionation, predicted biodegradation and biodigestion were evaluated using the Cornell Net Carbohydrate Protein System. The results show that: (1) The steam flaking induced significant changes in CHO subfractions, CHO biodegradation and biodigestion in ruminant system. There were significant differences between non-processed (raw) and steam flaked grain corn ( P < .01); (2) The ATR-Ft/VMS molecular technique was able to detect the processing induced CHO molecular structure changes; (3) Induced CHO molecular structure spectral features are significantly correlated ( P < .05) to CHO subfractions, CHO biodegradation and biodigestion and could be applied to potentially predict CHO biodegradation ( R 2 = 0.87, RSD = 0.74, P < .01) and intestinal digestible undegraded CHO ( R 2 = 0.87, RSD = 0.24, P < .01). In summary, the processing induced molecular CHO structure changes in grain corn could be revealed by the ATR-Ft/VMS vibrational molecular spectroscopy. These molecular structure changes in grain were potentially associated with CHO biodegradation and biodigestion. [ABSTRACT FROM AUTHOR]

The wide use of carbohydrate-based compounds is the pharmaceutical, cosmetic, detergent and food industry has led to the development of efficient synthetic procedures to overcome many drawbacks of conventional synthetic methodologies such as protection/activation/deprotection steps. In this context, due to their high chemo-, regio- and stereoselectivity, enzymes offer very effective and sustainable possibilities, and thus, they are increasingly used in carbohydrate field. In addition, the combination of biocatalysis and the use of green solvents is becoming a real alternative, as many solvents provide interactions with enzymes improving their catalytic behaviour, and they both directly contribute to increase the processes sustainability. This review will provide recent examples of the enzymatic preparation of carbohydrates and glycoconjugates using a combination of hydrolases (lipase and glycosidases) and green solvents. [ABSTRACT FROM AUTHOR]

Ketosamines are an important class of glycoconjugates widely employed in clinical diagnostics and implicated in development of diabetic complications, intestinal infections, or advanced cancer, as well as in food organoleptic and nutritional value. We report on the first preparation and structural characterization of 1-amino-1-deoxy-L-sorbose (L-sorbosamine, L-SorNH2). The monosaccharide was synthesized from L-sorbose following a classic phenylosazone protocol. In aqueous solution, L-SorNH2 assumes an anomeric equilibrium consisting of 89.3% α-pyranose, 3.7% β-pyranose, 3.8% α-furanose, 2.4% β-furanose, and 0.9% acyclic keto tautomer. The α-pyranose anomer in crystalline L-SorNH2 × HCl adopts the 2C5 chair conformation, with bond lengths and valence angles comparing well with related sorbopyranose structures. All hydroxyl oxygen atoms, the ammonium group and chloride ion are involved in an extensive hydrogen bonding network which is formed by infinite chains with fused antidromic R76(14), R54(10), and R43(8) cycles. The Hirshfeld surface analysis suggests a significant contribution of the non-polar intermolecular contacts to the crystal structure, as well. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium spp.) is an imperative economic crop of the globe due to its natural textile fiber. Molecular mechanisms of fiber development have been greatly revealed in allotetraploid cotton but remained unexplored in Gossypium herbaceum. G. herbaceum can withstand the rigors of nature like drought and pests but produce coarse lint. This undesirable characteristic strongly needs the knowledge of fiber development at molecular basis. The present study reported the transcriptome sequence of the developing fiber of G. herbaceum on pyrosequencing and its analysis. About 1.38 million raw and 1.12 million quality trimmed reads were obtained followed by de novo assembly-generated 20,125 unigenes containing 14,882 coding sequences (CDs). BLASTx-based test of homology indicated that A1-derived transcripts shared a high similarity with Gossypium arboreum (A2). Functional annotation of the CDs using the UniProt categorized them into biological processes, cellular components, and molecular function, COG classification showed that a large number of CDs have significant homology in COG database (6215 CDs), and mapping of CDs with Kyoto Encyclopedia of Genes and Genomes (KEGG) database generated 200 pathways ultimately showing predominant engagement in the fiber development process. Transcription factors were predicted by comparison with Plant Transcription Factor Database, and their differential expression between stages exposed their important regulatory role in fiber development. Differential expression analysis based on reads per kilobase of transcript per million mapped reads (RPKM) value revealed activities of specific gene related to carbohydrate and lipid synthesis, carbon metabolism, energy metabolism, signal transduction, etc., at four stages of fiber development, and was validated by qPCR. Overall, this study will help as a valuable foundation for diploid cotton fiber improvement. [ABSTRACT FROM AUTHOR]

A concise synthesis of C-furanosides has been achieved, starting from unprotected D-xylose and D-arabinose. Both sugars reacted with hydroxylamine 6 to give the respective nitrones. These underwent in-situ intramolecular 1,3-dipolar cycloaddition reactions to give, in each case, a pair of diastereomeric derivatives of 7-oxa-1-aza-bicyclo[2.2.1]heptane 7 and 8. The ratio of chromatographically separable diastereoisomers could be changed by carrying out the reaction in the presence of weak Lewis acid. Both D-xylose-derived stereoiso-mers 7a and 8a were converted into D-erythro-C-furanosides by tosylation or mesylation followed by catalytic hydrogenolysis. On the other hand, the formation of D-threo-C-furanosides from D-arabinose derivatives 7b and 8b under similar conditions was accompanied by the formation of minor amounts of polyhydroxyquinolizidines as a result of competitive N-alkylation. The polyhydroxyquinolizidine side-products were useful for the assignment of the configuration of the new compounds. [ABSTRACT FROM AUTHOR]

Laforin catalyses glycogen dephosphorylation. Mutations in its gene result in Lafora disease, a fatal progressive myoclonus epilepsy, the hallmark being water‐insoluble, hyperphosphorylated carbohydrate inclusions called Lafora bodies. Human laforin consists of an N‐terminal carbohydrate‐binding module (CBM) from family CBM20 and a C‐terminal dual‐specificity phosphatase domain. Laforin is conserved in all vertebrates, some basal metazoans and a small group of protozoans. The present in silico study defines the evolutionary relationships among the CBM20s of laforin with an emphasis on newly identified laforin orthologues. The study reveals putative laforin orthologues in Trichinella, a parasitic nematode, and identifies two sequence inserts in the CBM20 of laforin from parasitic coccidia. Finally, we identify that the putative laforin orthologues from some protozoa and algae possess more than one CBM20. [ABSTRACT FROM AUTHOR]

The ability to detect the undeclared addition of a juice of lesser economic value to one of higher value (juice-to-juice debasing) is a particular concern between apple and pear juices due to similarities in their major carbohydrate/polyol profiles. Fingerprint compounds for the detection of this type of adulteration were identified in both commercial apple and pear juices by HPLC-PDA, were isolated chromatographically, and structurally identified by LC-MS/MS. The apple juice fingerprint was identified as 4- O - p -coumarylquinic acid and two pear compounds as isorhamnetin-3- O -rutinoside and abscisic acid. Additionally, the HPLC-PDA profile of pear juices in combination with pear fingerprint compounds including arbutin could be used to identify samples originating from China versus those from other geographical locations. [ABSTRACT FROM AUTHOR]

Bacillus circulans Jordan 32352 was isolated from decaying organic matter in the New Jersey soil in the early 1930s. This soil-dwelling bacterium produced an enzyme capable of degrading the type 3 capsular polysaccharide (Pn3P) of Streptococcus pneumoniae (Spn). Early reports of this enzyme, Pn3Pase, demonstrated its inducibility by, and specificity for Pn3P. We set out to identify and clone this enzyme for its recombinant expression and characterization. We first sequenced the genome of this bacterial species, and reclassified the Pn3Pase producing bacterium as Paenibacillus species 32352. We identified the putative protein of Pn3Pase through mass spectrometry-based proteomics and cloned the gene for recombinant expression. We then characterized the oligosaccharide products generated upon the enzymatic depolymerization of Pn3P. Sequence analysis suggests that this glycoside hydrolase belongs to a new carbohydrate-active enzyme GH family. To our knowledge, this is the only enzyme to demonstrate Pn3P depolymerization activity. [ABSTRACT FROM AUTHOR]