Acetamido Group Research Articles

Total Syntheses of Conjugation-Ready Repeating Units of Acinetobacter baumannii AB5075 for Glycoconjugate Vaccine Development.

Acinetobacter baumannii is an opportunistic pathogen that causes serious nosocomial infections. One of the multidrug‐resistant strains, AB5075, can result in bacteremia, pneumonia and wound infections associated with high morbidity and mortality. The structurally unique glycans on the surface of these bacteria are attractive targets for the development of glycoconjugate vaccines. Here, we report the first total synthesis of the densely functionalized trisaccharide repeating unit of A. baumannii AB5075 as well as two analogues. The construction of 1,2‐cis linkages between the rare sugars relies on a double‐serial inversion strategy. The judicious selection of building blocks and reaction conditions allowed for stereoselective glycosylations, the installation of acetamido groups and the (S)‐3‐hydroxybutanoyl chain.

Study on the thermal and electrical properties of novel poly[propyl acrylate-co-phenyl methacrylate] containing acetamido group

Study on the thermal and electrical properties of novel poly[propyl acrylate-co-phenyl methacrylate] containing acetamido group

Removal of Toxic Dyestuffs from Aqueous Solution by Amphoteric Bioadsorbent

Background: Color effluents generated from the production industry of dyes and pigments and their use in different applications, such as textile, paper, leather tanning, and food industries, are high in color and contaminants that damage the aquatic life. It is estimated that about 105 of various commercial dyes and pigments amounted to 7×105 tons are produced annually worldwide. Ultimately, about 10-15% is wasted into the effluents of the textile industry. Chitin is abundant in nature, and it is a linear biopolymer containing acetamido and hydroxyl groups amenable to render it atmospheric by introducing amino and carboxyl groups, hence able to remove different classes of toxic organic dyes from colored effluents. Methods: Chitin was chemically modified to render it amphoteric via the introduction of carboxyl and amino groups. The amphoteric chitin has fully been characterized by FTIR, TGA-DTG, elemental analysis, SEM, and point of zero charges. Adsorption optimization for both anionic and cationic dyes was made by batch adsorption method, and the conditions obtained were used for studying the kinetics and thermodynamics of adsorption. Results: The results of dye removal proved that the adsorbent was proven effective in removing both anionic and cationic dyes (Acid Red 1 and methylene blue (MB)), at their respective optimum pHs (2 for acid and 8 for cationic dye). The equilibrium isotherm at room temperature fitted the Freundlich model for MB, and the maximum adsorption capacity was 98.2 mg/g using 50 mg/l of MB, whereas the equilibrium isotherm fitted the Freundlich and Langmuir model for AR1 and the maximum adsorption capacity was 128.2 mg/g. Kinetic results indicate that the adsorption is a two-step diffusion process for both dyes as indicated by the values of the initial adsorption factor (Ri) and follows the pseudo-second-order kinetics. Also, thermodynamic calculations suggest that the adsorption of AR1 on the amphoteric chitin is an endothermic process from 294 to 303 K. The result indicated that the mechanism of adsorption is chemisorption via an ion-exchange process. Also, recycling of the adsorbent was easy, and its reuse for dye removal was effective. Conclusion: New amphoteric chitin has successfully been synthesized and characterized. This resin material, which contains amino and carboxyl groups, is novel as such chemical modification of chitin hasn’t been reported. The amphoteric chitin has proven effective in decolorizing aqueous solution from anionic and cationic dyes. The adsorption behavior of amphoteric chitin is believed to follow chemical adsorption with an ion-exchange process. The recycling process for few cycles indicated that the loaded adsorbent could be regenerated by simple treatment and retested for removing anionic and cationic dyes without any loss in the adsorbability. Therefore, the study introduces a new and easy approach for the development of amphoteric adsorbent for application in the removal of different dyes from aqueous solutions.

Fluorescent Amphiphilic Quaternized β-Chitin: Antibacterial Mechanism and Cell Imaging.

Fluorescent materials span multiple applications from biological probes and chemical sensing to optoelectronic systems. Although great efforts have been made toward developing classes of fluorescent materials, 100,000+ traditional fluorescent dyes still suffer from the obstacle of aggregation-caused quenching (ACQ). Thus, designing fluorescent materials with excellent optical performance from ACQ luminogens remains challenging. In this work, we prepared fluorescent amphiphilic quaternized β-chitin (QC-F) via nucleophilic addition between the amino groups of QC and isothiocyanate groups of fluorescein isothiocyanate (FITC). Due to the covalent anchoring of the QC backbone, steric hindrance of the bulky acetamido groups, electrostatic repulsion of the quaternary ammonium groups, and homogeneous distribution of FITC units, the FITC units were spatially and electronically isolated, and the QC-F series exhibited unique fluorescent behaviors. The QC-F series could be used to observe their interactions with microbial cells through fluorescence imaging to gain insights into the QC antibacterial mechanism. Moreover, with their favorable cytocompatibility, the QC-F series are also suitable for cell imaging. Thus, the present work will broaden the applications of chitin and conventional ACQ luminogens.

TiO2/Polyethersulphone films for photocatalytic degradation of acetaminophen in aqueous solution

In this study, TiO2-polyethersulfone films with different TiO2 loadings, prepared by the phase inversion method were tested as photocatalysts for degradation of acetaminophen in aqueous solution. The prepared films were characterized by XRD, SEM-EDX, AFM, and XPS. The successful incorporation of the titanium dioxide nanoparticles was confirmed by the XRD and SEM-EDX. SEM images revealed a much smoother surface for the pristine PES as compared to the TiO2-PES films, while EDX result confirmed the immobilization of titanium, as increasing amounts of titania were detected with increased loading of titanium dioxide. The SEM cross sectional images also show that the prepared films transformed into porous structures with tear-like pores and the porosity increased from 0.06%, for pristine PES, to 0.35% for the (14 wt%) TiO2-PES, and then dropped slightly to 0.32% in (17 wt%) TiO2-PES due to the onset of aggregation. The TiO2-PES photocatalyst film with 14 wt% content of TiO2 exhibited 51% degradation efficiency for a film surface area of 80 cm2, and a maximum efficiency of 80% at 320 cm2 film surface area. However, an increased TiO2 loading up to 17 wt% led to a decline in efficiency which is attributed to agglomeration and possible defective pore structure of the films. The reactivity of the acetaminophen molecule, modelled using the density functional theory (DFT), enabled identification of the acetamido group and the aromatic ring as the regions most prone to electrophilic and radical attack, respectively.

Лектин, специфічний до N-ацетилнейрамінової кислоти, з червоної водорості Gracilaria canaliculata Sonder та його антибактеріальна активність

A new lectin from the marine red alga Gracilaria canaliculata (GCL) was isolated by a combination of aqueous ethanol extraction, ethanol precipitation, ion exchange and filtration chromatography. Lectin gave a single band with molecular mass of 22,000 Da in both non-reducing and reducing SDS-PAGE conditions, indicating that GCL is a monomeric protein. The hemagglutination activities of GCL were stable over a wide range of pH from 3 to 10, temperature up 60 oC and not affected by either the presence of EDTA or addition of divalent cations. Lectin GCL had high affinity for N-acetylneuraminic acid through interacting with the acetamido group at equatorial C2 position of these sugar residues, suggesting that GCL is specific for N-acetylneuraminic acid. Furthermore, GCL inhibited the growth of human and shrimp pathogenic bacteria, Staphylococcus aureus and Vibrio alginolyticus, although it did not affect the growth of Escherichia coli, Enterobacter cloace, Vibrio parahaemolyticus and V. harveyi. The red alga G. canaliculata may promise to be a source of valuable lectins for application as antibacterial agents.

Styrylbenzene organogels and how the cyano groups tune the aggregation-induced emission

Fluorescence switching of π-gelators has emerged as a field of great interest because of their promising applications. In this work we present two families of luminogens based on bis(styrylbenzene) and bis(α-cyanostyryl)benzene that incorporate acetamido groups and hydrocarbon chains to induce gelation. The presence of cyano groups in the molecular skeleton produces Aggregation Induced Emission (AIE) from solution to the gel while their absence gives the Aggregation Caused Quenching (ACQ) effect. Density Functional Theory calculations were performed in order to shed light on the origin of these opposite phenomena. The bis(styrylbenzene) compound showed a high quantum yield in solution and nearly planar structure was theoretically predicted. A significant drop in the quantum yield was observed after gelation, probably due to the π-π intermolecular interactions favoured by the planar scaffold. In contrast, the more twisted structure predicted for the cyano compounds could prevent such π-π intermolecular interactions and this would favour fluorescence emission. In addition, the twisted molecular structure predicted for the cyano derivative could induce Z/E photosiomerisation that suppresses the emission in solution. However, the framework of intermolecular contacts that arises during the gelation process could restrict torsional motions to the detriment of photoisomerization, thus resulting in AIE-active compounds. Furthermore, the reorganisation energy and Huang–Rhys factors associated with the non-radiative relaxation were calculated. The highest values were found for some vibrational modes in the low energy region in the case of the cyano compound and these could contribute to the non-radiative relaxation in solution. These intramolecular motions could be blocked in the gel, thus increasing the fluorescence emission. The introduction of cyano groups in the carbon scaffold could therefore provide a strategy for the rational design of new active AIE organogels.

Alternating copolymerization of bio-based N-acetylhomocysteine thiolactone and epoxides

The anionic ring-opening polymerizations (AROP) of bio-based N-acetyl homocysteine thiolactone (NHTL) and different epoxides were carried out using benzyl alcohol and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) as initiating system. This polymerization is a rare example of AROP in the presence of an acidic moiety (acetamido group). Well-defined alternating poly(ester-alt-sulfide)s are obtained with number-average molar masses Mn ranging from 1.7 to 13.0 kg mol−1 and dispersities as low as 1.14. The presence of one acetamido function in the lateral group on each repeating unit of the copolymers derived from NHTL results in very significant increases (up to 94 °C) of the glass transition temperature Tg compared to similar poly(ester-alt-sulfide) derived from petro-based γ-butyrothiolactone (BTL). These functional poly(NHTL-alt-epoxide)s are valuable structures with numerous potential applications due to the presence in each repeating unit of one cleavable ester group and one redox-sensitive thioether group.

Gram-Scale, Seven-Step Total Synthesis of (-)-Colchicine.

Herein we report a streamlined, gram-scale total synthesis of (-)-colchicine that takes only 7 easy steps, with an overall yield of 27-36%. To warrant the synthetic efficiency and practicality of (-)-colchicine, we tactically utilized a modified version of a powerful Ir-catalyzed amidation reported by Carreira to install the key chiral C-7 acetamido group, Suzuki and biomimetic phenol oxidative coupling, and Banwell-inspired cyclopropane ring cleavage to construct (-)-colchicine precisely and rapidly. Remarkably, a described strategy also can shorten the synthesis of allocolchicinoid to 4 steps.

N-Acetylneuraminic Acid Specific Lectin and Antibacterial Activity from the Red Alga Gracilaria canaliculata Sonder

A new lectin from the marine red alga Gracilaria canaliculata (GCL) was isolated by a combination of aqueous ethanol extraction, ethanol precipitation, ion exchange and filtration chromatography. Lectin gave a single band with molecular mass of 22,000 Da in both non-reducing and reducing SDS-PAGE conditions, indicating that GCL is a monomeric protein. The hemagglutination activities of GCL were stable over a wide range of pH from 3 to 10, the temperature rose by 60 °C and it was not affected by either the presence of EDTA or addition of divalent cations. Lectin GCL had high affinity for N-acetylneuraminic acid through interacting with the acetamido group at equatorial C2 position of these sugar residues, suggesting that GCL is specific for N-acetyl-neuraminic acid. Furthermore, GCL inhibited the growth of human and shrimp pathogenic bacteria, Staphylococcus aureus, and Vibrio alginolyticus, although it did not affect the growth of Escherichia coli, Enterobacter cloace, Vibrio parahaemolyticus, and V. harveyi. The red alga G. canaliculata may promise to be a source of valuable lectins for application as antibacterial agents.

Enhanced Chitin Deacetylase Production Ability of Rhodococcus equi CGMCC14861 by Co-culture Fermentation With Staphylococcus sp. MC7.

Chitin deacetylase (CDA) can hydrolyze the acetamido group of chitin polymers and its deacetylated derivatives to produce chitosan, an industrially important biopolymer. Compared with traditional chemical methods, biocatalysis by CDA is more environment-friendly and easy to control. However, most reported CDA-producing microbial strains show low CDA producing capabilities. Thus, the enhancement of CDA production has always been a challenge. In this study, we report co-culture fermentation to significantly promote the CDA production of Rhodococcus equi CGMCC14861 chitin deacetylase (ReCDA). Due to co-culture fermentation with Staphylococcus sp. MC7, ReCDA yield increased to 21.74 times that of pure culture of R. equi. Additionally, the enhancement was demonstrated to be cell-independent by adding cell-free extracts and the filtrate obtained by 10 kDa ultrafiltration of Staphylococcus sp. MC7. By preliminary characterization, we found extracellular, thermosensitive signal substances produced by Staphylococcus that were less than 10 kDa. We investigated the mechanism of promotion of ReCDA production by transcriptomic analysis. The data showed that 328 genes were upregulated and 1,258 genes were downregulated. The transcription level of the gene encoding ReCDA increased 2.3-fold. These findings provide new insights into the research of co-culture fermentation for the production of CDA and quorum sensing regulation.

Mechanistic Insights into the Hydrolysis of O-GlcNAcylation Catalyzed by Human O-GlcNAcase.

O-GlcNAc glycosylation occurs on specific serine/threonine residues of intracellular proteins, which is widely related to various diseases, including type II diabetes, cancer, and Alzheimer's disease. Human O-GlcNAcase (hOGA) is responsible for the removal of O-GlcNAc modification and thus serves as the main target for inhibitor design. In this work, we systematically investigated the mechanism catalyzed by hOGA using the quantum mechanical/molecular mechanical method. Based on calculated free energy profiles, two essential steps named cyclization (Cyc) step and ring opening step are required to generate the final hemiacetal product. The Cyc of the 2-acetamido group, the rate-limiting step, leads to the generation of the intermediate of a bicyclic oxazolinium ion (EI1). Next, the oxazoline ring could be broken via the nucleophilic attack of a water molecule at the C1 position, which generates the final product. Along with this, our simulations clearly suggest the existence of an oxazoline intermediate (EI2), which is produced via proton transfer (PT) from the 2-acetamido group (EI1) to D174. This PT step features a reversible process with a low energy barrier, which could be attributed to a low barrier hydrogen bond between the donor and acceptor. The stabilizing effect of the low barrier hydrogen bond on EI1 is proposed to be very important for accelerating the overall reaction. In fact, the site-directed mutagenesis simulations of D174A and D175A strongly indicate that the catalytic residues mainly affect the observed reaction rate by affecting the stability of the intermediate.

Recognition of Dimeric Lewis X by Anti-Dimeric Lex Antibody SH2.

The carbohydrate antigen dimeric Lewis X (DimLex), which accumulates in colonic and liver adenocarcinomas, is a valuable target to develop anti-cancer therapeutics. Using the native DimLex antigen as a vaccine would elicit an autoimmune response against the Lex antigen found on normal, healthy cells. Thus, we aim to study the immunogenic potential of DimLex and search internal epitopes displayed by DimLex that remain to be recognized by anti-DimLex monoclonal antibodies (mAbs) but no longer possess epitopes recognized by anti-Lex mAbs. In this context, we attempted to map the epitope recognized by anti-DimLex mAb SH2 by titrations and competitive inhibition experiments using oligosaccharide fragments of DimLex as well as Lex analogues. We compare our results with that reported for anti-Lex mAb SH1 and anti-polymeric Lex mAbs 1G5F6 and 291-2G3-A. While SH1 recognizes an epitope localized to the non-reducing end Lex trisaccharide, SH2, 1G5F6, and 291-2G3-A have greater affinity for DimLex conjugates than for Lex conjugates. We show, however, that the Lex trisaccharide is still an important recognition element for SH2, which (like 1G5F6 and 291-2G3-A) makes contacts with all three sugar units of Lex. In contrast to mAb SH1, anti-polymeric Lex mAbs make contact with the GlcNAc acetamido group, suggesting that epitopes extend further from the non-reducing end Lex. Results with SH2 show that this epitope is only recognized when DimLex is presented by glycoconjugates. We have reported that DimLex adopts two conformations around the β-d-GlcNAc-(1→3)-d-Gal bond connecting the Lex trisaccharides. We propose that only one of these conformations is recognized by SH2 and that this conformation is favored when the hexasaccharide is presented as part of a glycoconjugate such as DimLex-bovine serum albumin (DimLex-BSA). Proper presentation of the oligosaccharide candidate via conjugation to a protein or lipid is essential for the design of an anti-cancer vaccine or immunotherapeutic based on DimLex.

Characterization of O-glycan binding lectin from the red alga Hydropuntia eucheumatoides

The red alga, Hydropuntia eucheumatoides is one of the algal genera from which agar is commercially extracted, and is the main source of agar in the world. The lectin HEL from the red alga H. eucheumatoides was isolated by a combination of aqueous ethanol extraction, ethanol precipitation, ion exchange and filtration chromatography. Lectin gave a single band with molecular mass of 17,000 Da in both non-reducing and reducing SDS-PAGE conditions, therefore lectin exists in monomeric form. The hemagglutination activities of HEL were stable over a wide range of pH from 3 to 10, temperature up 60 oC and not affected by either the presence of EDTA or addition of divalent cations, indicating that lectin requires no metal for biological activity. The hemagglutination activities of HEL were not inhibited by monosaccharides and glycoproteins, D-glucose, D-mannose, D-galactose, D-xylose, N-acety-D-mannosamine, transferin, fetuin and yeast mannan, but strongly inhibited by monosaccharides containing acetamido groups at equatorial C2 position, such as N-acetyl-galactosamine, N-acetyl-glucosamine, N-acetyl-neuraminic acid and glycoprotein porcine stomach mucin bearing O-glycans. Thus, lectin is specific for O-glycans and may recognize the sequences GalNAcαSer/Thr, GalNAc(α1-3)[Fuc(α1-2)]Gal(β1-4)GlcNAc(β1-3)GalNAc- and GluNAc(α1-4)Gal- under interacting with the acetamido groups at equatorial C2 position of the terminal sugar residues in oligosaccharide structures of O-glycans. The red alga H. eucheumatoides could promise to be a source of valuable lectins for application in biochemistry and biomedicine.

Fluorescent 2-phenyl-2H-benzotriazole dyes with intramolecular N–H···N hydrogen bonding: Synthesis and modulation of fluorescence properties by proton-donating substituents

A series of 2-(2-phenyl)benzotriazole derivatives having amino, N-methyl amino, and acetamido groups on the ortho position of the phenyl group were synthesized to elucidate the effects of amino/amido substitutions on the molecular structures and photophysical properties. 1H NMR spectra and DFT calculations of the present dyes revealed the formation of N–H∙∙∙N intramolecular hydrogen bonds between benzotriazole and amino/amide groups in the ground state. Amino-functionalized dyes showed absorption bands that were assigned to HOMO-LUMO transition with a partial charge-transfer feature. The dye with an acetoamido group in which the acidity of NH proton was increased by the effect of electron-withdrawing acetyl groups exhibited absorption bands attributable to intramolecular hydrogen-bonded “closed” conformers in CHCl3 and non-hydrogen-bonded “open” conformers in DMSO. In comparison to 2-phenylbenzotriazole, which had no acidic proton involved in intramolecular hydrogen bonding, the present derivatives exhibited weak fluorescence emissions with quite low quantum yields, suggesting that non-radiative deactivation of ESIPT states also operated in the N–H∙∙∙N hydrogen bonded 2-phenylbenzotriazoles just as in O–H∙∙∙N intramolecular hydrogen-bonded 2-hydroxyphenylbenzotriazoles, which are known as UV absorbers. Taking a closer look at the fluorescence spectra, dyes with amino and N-methylamino groups showed faint but dual emissions from charge-transfer excited states in CHCl3 and blue-shifted single emission in DMSO. Fluorescence emissions of the acetamido-functionalized dye were unimodal in each solvent and stronger than those of amino-functionalized dyes. Thus, the fluorescence properties of these dyes depended on substitutions at amino groups. The luminescence of these derivatives was enhanced in the polymer matrix in which conformation changes and molecular motions were suppressed. Dye-doped polymer films have absorption bands in the UV range (360–400 nm) and emitted at the visible region (450–510 nm), and thus could be used as organic materials for light conversion films that convert UV light into visible light.

Novel carbohydrate-recognition mode of the invertebrate C-type lectin SPL-1 from Saxidomus purpuratus revealed by the GlcNAc-complex crystal in the presence of Ca2.

The C-type lectins SPL-1 and SPL-2 from the bivalve Saxidomus purpuratus are composed of A and B chains and of two B chains, respectively. They bind specific carbohydrates containing acetamido groups, such as N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc), in a Ca2+-independent manner. Unlike ordinary C-type lectins, which require Ca2+ ions for carbohydrate recognition, these lectins recognize specific carbohydrates mainly through interactions with the acetamido group without Ca2+ ions, even though Ca2+ enhances the binding affinity of these lectins, especially SPL-1. In the present study, the crystal structure of the SPL-1-GlcNAc complex in the presence of Ca2+ revealed that the binding of SPL-1 to GlcNAc is stabilized by hydrogen bonds to the water molecule(s) coordinating Ca2+, whereas in ordinary C-type lectins Ca2+ directly forms coordinate bonds to the hydroxy groups of carbohydrates. These differences may also allow SPL-1 and SPL-2 to recognize both GlcNAc and GalNAc, which have different orientations of the 4-hydroxy group.

An Epoxide Intermediate in Glycosidase Catalysis.

Retaining glycoside hydrolases cleave their substrates through stereochemical retention at the anomeric position. Typically, this involves two-step mechanisms using either an enzymatic nucleophile via a covalent glycosyl enzyme intermediate or neighboring-group participation by a substrate-borne 2-acetamido neighboring group via an oxazoline intermediate; no enzymatic mechanism with participation of the sugar 2-hydroxyl has been reported. Here, we detail structural, computational, and kinetic evidence for neighboring-group participation by a mannose 2-hydroxyl in glycoside hydrolase family 99 endo-α-1,2-mannanases. We present a series of crystallographic snapshots of key species along the reaction coordinate: a Michaelis complex with a tetrasaccharide substrate; complexes with intermediate mimics, a sugar-shaped cyclitol β-1,2-aziridine and β-1,2-epoxide; and a product complex. The 1,2-epoxide intermediate mimic displayed hydrolytic and transfer reactivity analogous to that expected for the 1,2-anhydro sugar intermediate supporting its catalytic equivalence. Quantum mechanics/molecular mechanics modeling of the reaction coordinate predicted a reaction pathway through a 1,2-anhydro sugar via a transition state in an unusual flattened, envelope (E3) conformation. Kinetic isotope effects (kcat/KM) for anomeric-2H and anomeric-13C support an oxocarbenium ion-like transition state, and that for C2-18O (1.052 ± 0.006) directly implicates nucleophilic participation by the C2-hydroxyl. Collectively, these data substantiate this unprecedented and long-imagined enzymatic mechanism.

β-N-Acetylhexosaminidases for Carbohydrate Synthesis via Trans-Glycosylation

β-N-acetylhexosaminidases (EC 3.2.1.52) are retaining hydrolases of glycoside hydrolase family 20 (GH20). These enzymes catalyze hydrolysis of terminal, non-reducing N-acetylhexosamine residues, notably N-acetylglucosamine or N-acetylgalactosamine, in N-acetyl-β-D-hexosaminides. In nature, bacterial β-N-acetylhexosaminidases are mainly involved in cell wall peptidoglycan synthesis, analogously, fungal β-N-acetylhexosaminidases act on cell wall chitin. The enzymes work via a distinct substrate-assisted mechanism that utilizes the 2-acetamido group as nucleophile. Curiously, the β-N-acetylhexosaminidases possess an inherent trans-glycosylation ability which is potentially useful for biocatalytic synthesis of functional carbohydrates, including biomimetic synthesis of human milk oligosaccharides and other glycan-functionalized compounds. In this review, we summarize the reaction engineering approaches (donor substrate activation, additives, and reaction conditions) that have proven useful for enhancing trans-glycosylation activity of GH20 β-N-acetylhexosaminidases. We provide comprehensive overviews of reported synthesis reactions with GH20 enzymes, including tables that list the specific enzyme used, donor and acceptor substrates, reaction conditions, and details of the products and yields obtained. We also describe the active site traits and mutations that appear to favor trans-glycosylation activity of GH20 β-N-acetylhexosaminidases. Finally, we discuss novel protein engineering strategies and suggest potential “hotspots” for mutations to promote trans-glycosylation activity in GH20 for efficient synthesis of specific functional carbohydrates and other glyco-engineered products.

Direct Synthesis of para-Nitrophenyl Glycosides from Reducing Sugars in Water

Reducing sugars may be directly converted into the corresponding para-nitrophenyl (pNP) glycosides using 2-chloro-1,3-dimethylimidazolinium chloride (DMC), para-nitrophenol, and a suitable base in aqueous solution. The reaction is stereoselective for sugars with either a hydroxyl or an acetamido group at position 2, yielding the 1,2-trans pNP glycosides. A judicious choice of base allows extension to di- and oligosaccharide substrates, including a complex N-glycan oligosaccharide isolated from natural sources, without the requirement of any protecting group manipulations.

Isolation, characterisation, and genome sequencing of Rhodococcus equi: a novel strain producing chitin deacetylase

Chitin deacetylase (CDA) can hydrolyse the acetamido group of chitin polymers to produce chitosans, which are used in various fields including the biomedical and pharmaceutical industries, food production, agriculture, and water treatment. CDA represents a more environmentally-friendly and easier to control alternative to the chemical methods currently utilised to produce chitosans from chitin; however, the majority of identified CDAs display activity toward low-molecular-weight oligomers and are essentially inactive toward polymeric chitin or chitosans. Therefore, it is important to identify novel CDAs with activity toward polymeric chitin and chitosans. In this study, we isolated the bacterium Rhodococcus equi F6 from a soil sample and showed that it expresses a novel CDA (ReCDA), whose activity toward 4-nitroacetanilide reached 19.20 U/mL/h during fermentation and was able to deacetylate polymeric chitin, colloidal chitin, glycol-chitin, and chitosan. Whole genome sequencing revealed that ReCDA is unique to the R. equi F6 genome, while phylogenetic analysis indicated that ReCDA is evolutionarily distant from other CDAs. In conclusion, ReCDA isolated from the R. equi F6 strain expands the known repertoire of CDAs and could be used to deacetylate polymeric chitosans and chitin in industrial applications.