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Nucleic acid chemistry is a rapidly evolving field, and the need for novel nucleotide modifications and artificial nucleotide building blocks for diagnostic and therapeutic use, material science or for studying cellular processes continues unabated. This review focusses on the development and application of unnatural base pairs as part of an expanded genetic alphabet. Not only recent developments in "nature-like" artificial base pairs are presented, but also current synthetic methods to get access to C-glycosidic nucleotides. Wide-ranging viability in synthesis is a prerequisite for the successful use of unnatural base pairs in a broader spectrum and will be discussed. [ABSTRACT FROM AUTHOR]

Hydrolytic enzymes are essential components in second-generation biofuel technology and food fermentation processes. Nanozymes show promise for large-scale industrial applications as replacements for natural enzymes due to their distinct advantages. However, there remains a research gap concerning glycosidase nanozymes. In this study, a Zn-based single-atom nanozyme (ZnN 4 -900) is developed for efficient glycosidic bond hydrolysis in an aqueous solution. The planar structure of the class-porphyrin N 4 material approximatively mimicked the catalytic centers of natural enzymes, facilitating oxidase-like (OXD-like) activity and promoting glycosidic bond cleavage. Theoretical calculations show that the Zn site can act as Lewis acids, attacking the C─O bond in glycosidic bonds. Additionally, ZnN 4 -900 has the ability to degrade starch and produce reducing sugars that increased yeast cell biomass by 32.86% and ethanol production by 14.56%. This catalyst held promising potential for enhancing processes in ethanol brewing and starch degradation industries., (© 2024 Wiley‐VCH GmbH.)

[Display omitted] • Microwave heating promotes transglycosylation under mild temperature. • Microwave disrupts the hydrogen bonding networks within biomass structure. • Microwave activates the glycosidic bonds, thereby facilitating its cleavage. • Processes integrated with microwave are energy-saving and cost-effective. Depolymerization of carbohydrate biomass using a long-chain alcohol (transglycosylation) to produce alkyl glycoside-based bio-surfactants has been gaining industrial interest. This study introduces microwave-assisted transglycosylation in transforming wheat bran, a substantial agricultural side stream, into these valuable compounds. Compared to traditional heating, microwave-assisted processing significantly enhances the product yield by 53 % while reducing the reaction time by 72 %, achieving a yield of 29 % within 5 h. This enhancement results from the microwave's capacity to activate intermolecular hydrogen and glycosidic bonds, thereby facilitating transglycosylation. Life-cycle assessment and techno-economic analysis demonstrate the benefits of microwave heating in reducing energy consumption by 42 %, CO 2 emissions by 56 %, and equipment, operational and production costs by 44 %, 35 % and 30 %, respectively. The study suggests that microwave heating is a promising approach for efficiently producing bio-surfactants from agricultural wastes, with potential cost reductions and environmental benefits that could enhance industrial biomass conversion processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polarization of the water environment reduces double-ionization energies and facilitates the hole transfer. • Double ionization in solutions is independent of the counterion. • The environment screens the contribution of the phosphate group. • The barrier height of bond break suggests that the scission of the glycosidic bond could be a potential damaged pathway. Computations were carried out to investigate the mechanism of double-ionization damage for deoxyguanosine nucleotide. The results reveal that the polarization of the water environment reduces double-ionization energies and facilitates the hole transfer. Double ionization in solutions is independent of the counterion. The environment screens the contribution of the phosphate group. After double ionization, cleavage of the C-N glycosidic bond is a barrierless process in the gas phase. The barrier height of bond break is ∼ 4.0 kcal/mol in solutions. The C-N scission could be a potential damaged pathway. The counterion has a minor effect on the bond rupture. [ABSTRACT FROM AUTHOR]

Pyrolysis of cellulose has been widely investigated based on experiments and density functional theory (DFT) calculations, whereas the role of glycosidic bonds remains unclear. In this work, the machine learning based method has been employed in cellulose pyrolysis mechanism study, with β-d-glucose and methyl β-d-glucoside as model compounds. The initial pyrolysis reactions are automatically determined through potential energy surface (PES) searching based on the combined methodology of stochastic surface walking and neural network potential (SSW-NN). 229 and 43 reaction pairs with reliable transition states have been obtained in the reaction space of β-d-glucose and methyl β-d-glucoside, respectively, and 33 elementary reactions in the initial pyrolysis stage have been found among these reaction pairs. Besides the well-known reactions, new and feasible reactions are identified by the SSW-NN method. Particularly, it is newly found that the ring-opening and glycosidic bond breaking involve multiple hydrogen transfer processes, where the hydrogen transfer is assisted by 3-OH and/or 6-OH. Hence, these reactions have relatively low energy barriers. The reactions involving the participation of the C1 group are significantly influenced by the glycosidic bond. On the contrary, other reactions without involving the C1 group are almost not affected by the glycosidic bond. Such results should be ascribed to the distinction of electrostatic potentials of the C1 free hydroxyl and the glycosidic bond. This study can provide new insight into the cellulose pyrolysis mechanism based on the SSW-NN method.

[Display omitted] • High regioselectivity and hydrolysis ability to ginsenosides by snailase were found. • Ginsenoside Ro was transformed to Chikusetsusaponin Ⅳa in vitro for the first time. • Ginsenoside Ro was transformed to Glucosyl oleanilate in vitro for the first time. • Ginsenoside Ro was transformed to Zingibroside R1 in vitro for the first time. • Ginsenoside Ro was transformed to Silphioside F in vitro for the first time. Minor ginsenosides display higher physiological activities than those of major ginsenosides, but their low abundance limits their clinical application. In this study, snailase was employed to transform protopanaxadiol-type (PPD) ginsenosides, protopanaxatriol-type (PPT) ginsenosides, and Ro to minor ginsenosides. The results showed that snailase hydrolyzed the saccharide chains at the C-3 position of Rb1, Rc, Rb2 Rg3 and Ro and the saccharide chains at the C-28 position of Ro efficiently. The end glucosyl unit of the saccharide chain at the C-6 position of Rf was hydrolyzed entirely. However, the rhamnosyl of Re was intact. The end glucosyl unit of the ginsenoside Rb1 was hydrolyzed entirely, but both arabinopyranosyl of Rb2 and arabinofuranosyl of Rc were not hydrolyzed. So snailase is selective for glycoside bond locations and saccharide types of ginsenoside, and it can be used to produce Rg3, CK, Rh1 and so on. [ABSTRACT FROM AUTHOR]

Exploiting new solvents on efficiently dissolving cellulose is imperative to promote the utilization of cellulosic resources. The process of cellulose dissolution typically necessitates extreme conditions, such as high-temperature treatment, utilization of potent acidic or basic solvents, or the catalytic action of Lewis acids. As a result, the structure of the cellulose is invariably compromised, subsequently obstructing the creation of high-performance materials. In this study, we address this challenge through a simple process, introducing polyethylene glycol (PEG) as glycosidic bond protecting agent, to preserve the polymerization degree of cellulose during its room-temperature dissolution in ZnCl 2 -phosporic acid eutectic solvent. The PEG units preferentially coordinate with Zn2+ to weaken the hydrolysis of glycosidic bond of cellulose through ether bond competition. The polymerization degree of regenerated cellulose is thus greatly improved, reaching up to seven times that of unprotected cellulose. Overall, this study offers an easy and cost-effective approach to develop cellulose solvents and provides a significant drive towards the fabrication of practical materials through cellulose dissolution. [Display omitted] • A multi-site competition strategy to protect the degree of polymerization of cellulose was proposed. • PEG units preferentially coordinate with Zn2+ to weaken the hydrolysis of glycosidic bond of cellulose. • The solvent possesses suitability for dissolving various cellulose feedstocks with high molecular weights and crystallinity. [ABSTRACT FROM AUTHOR]

Prebiotic oligosaccharides are naturally occurring nondigestible carbohydrates with demonstrated health benefits. They are also a chemically diverse class of nutrients, offering an opportunity to investigate the impact of molecular structure on oligosaccharide taste perception. Accordingly, a relevant question is whether these compounds are detected by the human gustatory system, and if so, whether they elicit sweet or "starchy" taste. Here, in 3 psychophysical experiments, we investigated the taste perception of 3 commercially popular prebiotics [fructooligosaccharides (FOS), galactooligosaccharides (GOS), xylooligosaccharides (XOS)] in highly pure form. Each of these classes of prebiotics differs in the type of glycosyl residue, and position and type of bond between those residues. In experiments I and II, participants were asked to discriminate a total of 9 stimuli [FOS, GOS, XOS; degree of polymerization (DP) of 2, 3, 4] prepared at 75 mM in the presence and absence of lactisole, a sweet receptor antagonist. We found that all 9 compounds were detectable (P < 0.05). We also found that GOS and XOS DP 4 were discriminable even with lactisole, suggesting that their detection was not via the canonical sweet receptor. Accordingly, in experiment III, the taste of GOS and XOS DP 4 were directly compared with that of MOS (maltooligosaccharides) DP 4-6, which has been reported to elicit "starchy" taste. We found that GOS and MOS were perceived similarly although narrowly discriminable, while XOS was easily discriminable from both GOS and MOS. The current findings suggest that the molecular structure of oligosaccharides impacts their taste perception in humans., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The reactivity of a range of Keggin and Wells–Dawson type heteropolyacids (HPAs): H3PW12O40 H4SiW12O40, H3PMo12O40, K6P2W18O62, and NaH2W12O4, towards the heavily glycosylated α‐1‐acid glycoprotein (AGP) is reported. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) and high‐performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) show that after incubation of the protein with HPAs at 80 °C and pH 2.8 complete hydrolysis of terminal glycosidic bond has been achieved, resulting in the removal of sialic acids with no observed destruction of the protein core or the residual glycan chains. The 1H NMR spectroscopy confirmed that the released sialic acids preserve intact structure upon their excision from the protein, which makes the reported method suitable for the analysis of sialic acid modifications which play an important role in numerous biological processes. The presence of other sugars was not detected by 1H NMR and HPAEC‐PAD, suggesting that HPAs hydrolyze only the terminal glycosidic bond in the glycoprotein, resulting in the selective release of sialic acid from AGP. The kinetic results have shown that under equal temperature and pH conditions, the hydrolysis of the terminal glucosidic bond occurred faster in the presence of HPAs compared to conventional mineral acids. The observed rate constants were in the range 6,7×10−2 −11,9×10−2 min−1 and the complete and selective excision of sialic acids could be achieved within 60 min of incubation. The Trp fluorescence and CD spectroscopy show that non‐covalent interaction between HPA and protein takes place in solution which could lead to stabilization of the sialosyl cation that is formed during the glycosidic bond hydrolysis by anionic HPA cluster. [ABSTRACT FROM AUTHOR]

Bacterial and fungal exopolysaccharides (EPSs) are extracellular metabolites of living organisms (plants, animals, algae, bacteria and fungi) associated with adaptation, survival and functionalities. The EPSs also afford humans multiple value-adding applications across different spheres of endeavors. The variable chemical and biochemical architecture that characterizes an EPS presets its biological functionality and potential biotechnological benefits. Suffices to say that it is amenable to genetic, biotechnological and biochemical maneuverability for desired bioactivity or application during their production and extraction. EPSs have been shown to have, antioxidant, anti-tumor and antiviral activities; enhance soil aridity and nutritional value of food consumed by humans. Their innocuous domestic and commercial versatility and biotechnological relevance is a reliable confirmation of the recent attention accorded EPSs by the global research community. This is especially with respect to their biosynthesis, composition, production, structure, characterization, sources, functional properties and applications. It is also responsible for the development of newer strategies for their extraction. EPSs’ relative prospects, perspectives and orientation in the African context are seldom reported in recognized scientific literature data bases. A random preliminary study showed that EPS applications, biotechnological and research orientations are still developing, and influenced by preponderant vegetation, level of industrialization, political will and culture. Africa is endowed with untapped bioresources (biomaterials), bioproducts and bioequivalents that can mediate several global foods, industrial and technological challenges for which EPS may be a potential remedy.

In green species, sucrose can help antagonize abiotic stress. Sucrose phosphate synthase (SPS) is a well-known rate-limiting enzyme in the synthesis of sucrose. To date, however, there is no known crystal structure of SPS from plant or cyanobacteria. In this study, we report the first co-crystal structure of SPS from Thermosynechococcus elongatus with UDP and sucrose-6-phosphate (S6P). Within the catalytic site, the side chains of His158 and Glu331, along with two phosphate groups from UDP, form hydrogen bonds with the four hydroxyl groups of the glucose moiety in S6P. This association causes these four hydroxyl groups to become partially negatively charged, thus promoting formation of the C1 oxocarbenium ion. Breakage of the hydrogen bond between His158 and one of the hydroxyl groups may trigger covalent bond formation between the C1 oxocarbenium ion and the C2 hydroxyl of fructose-6-phosphate. Consistent with our structural model, we observed that two SPS mutants, H158A and E331A, lost all catalytic activity. Moreover, electron density of residues from two loops (loop1 and loop2) in the SPS A-domain was not observed, suggest their dynamic nature. B-factor analysis and molecular dynamics stimulations of the full-length enzyme and A-domain indicate that both loops are crucial for binding and release of substrate and product. In addition, temperature gradient analysis shows that SPS exhibits its highest activity at 70°C, suggesting that this enzyme has the potential of being used in industrial production of S6P.

In green species, sucrose can help antagonize abiotic stress. Sucrose phosphate synthase (SPS) is a well-known rate-limiting enzyme in the synthesis of sucrose. To date, however, there is no known crystal structure of SPS from plant or cyanobacteria. In this study, we report the first co-crystal structure of SPS from Thermosynechococcus elongatus with UDP and sucrose-6-phosphate (S6P). Within the catalytic site, the side chains of His158 and Glu331, along with two phosphate groups from UDP, form hydrogen bonds with the four hydroxyl groups of the glucose moiety in S6P. This association causes these four hydroxyl groups to become partially negatively charged, thus promoting formation of the C1 oxocarbenium ion. Breakage of the hydrogen bond between His158 and one of the hydroxyl groups may trigger covalent bond formation between the C1 oxocarbenium ion and the C2 hydroxyl of fructose-6-phosphate. Consistent with our structural model, we observed that two SPS mutants, H158A and E331A, lost all catalytic activity. Moreover, electron density of residues from two loops (loop1 and loop2) in the SPS A-domain was not observed, suggest their dynamic nature. B-factor analysis and molecular dynamics stimulations of the full-length enzyme and A-domain indicate that both loops are crucial for binding and release of substrate and product. In addition, temperature gradient analysis shows that SPS exhibits its highest activity at 70°C, suggesting that this enzyme has the potential of being used in industrial production of S6P. [ABSTRACT FROM AUTHOR]

The data on the structure of O-specific polysaccharides (O-antigens) of all nine known molecular types (potential O-serotypes) of a new type of enterobacteria Escherichia albertii, causative agents of intestinal infections in humans and birds, are presented. The advantages and limitations of structural analysis methods used to determine the structure of E. albertii polysaccharides are discussed. The annotation of genes in gene clusters of biosynthesis of O-antigens of E. albertii was carried out by comparison with the sequences in the available databases. Structural and genetic relationships between O-antigens of E. albertii and closely related species of E. coli are discussed. It was found that, in addition to the O-antigen, E. albertii O9 expresses a mannan of the same structure as the mannan of E. coli O8. [ABSTRACT FROM AUTHOR]

Water based solutions of κ-Carrageenan (1.5% weight concentration), a high molecular weight polysaccharide, were subjected to acid-catalyzed hydrolysis under controlled pH (≈3) and temperature (from 40 to 70 °C). The hydrolysis process involves selective attack of the Carrageenan glycosidic bonds α(1–3) and β(1–4), determining changes in the weight average molecular weight of the macromolecule and, as a consequence, on the gelling behavior. In this study we used transient rheological tests to monitor the hydrolysis reaction and its consequences on both the sol-gel transition and the final gel properties. Hydrolysis reaction has been modelled using a bi-exponential kinetics. To this end, a rotational rheometer was equipped with a batch reactor configuration, consisting of a cylindrical vessel and a double helix mixing tool. Both viscous and viscoelastic properties of the samples were measured quantitatively and related to the biopolymer molecular weight, replacing more complex molecular weight determinations by an easier methodology. By using the above experimental approach, kinetic constants and activation energies for the κ-Carrageenan hydrolysis were obtained as a function of the hydrolysis temperature. The latter, along with the hydrolysis reaction time, was also shown to be a relevant parameter in determining the possibility of gel formation and of the gel mechanical strength (in the range 10–600 Pa). [Display omitted] • Acid-catalyzed hydrolysis of κ−Carrageenan was monitored using a batch rheo-mixing reactor, at controlled PH and temperature. • Trough viscosity measuring of the κ−Carrageenan during hydrolysis it was possible to determine the kinetics parameters of the hydrolysis reaction. • Tuning the gel properties by changing accordingly temperature and exposure time of the κ−Carrageenan to the acid environment. • In-process optimization of the κ-C properties to provide the specific functionality required for a given application. [ABSTRACT FROM AUTHOR]

Chitosan–based biomaterials with a low molecular weight (LMW) have been drawn attention due to the promising applications in the pharmaceutical and food fields. For this reason, the aim of this work was to study the effect of two distinct depolymerization pathways on the chitosan physicochemical properties. Chitosan was submitted to depolymerization reaction to obtain chitosan with low molecular weight (LMW), using the oxidative pathway (H 2 O 2) and the acid pathway (HCl). The molecular weight reduction was investigated by kinetic study and chain scission mechanism. Chitosan characterization was performed according to its viscosimetric average molecular weight and deacetylation degree, respectively, through the viscosimetric method and proton nuclear magnetic resonance spectroscopy (1H NMR). The structural integrity was evaluated by Fourier transform infrared (FTIR) and energy dispersive spectroscopy (EDS). The crystalline and thermal properties were investigated, respectively, by X–ray diffraction (XRD) spectroscopy and thermogravimetric (TGA)/ differential thermal (DTA)/ differential scanning calorimetry (DSC) analysis. The water–chitosan interaction study was used to estimate the chitosan solubility. The results pointed out that both pathways resulted in chitosan with low molecular weight (<50 kDa). Moreover, the structural integrity of chitosan polymeric chains was preserved after depolymerization by oxidative pathway, while the acid pathway modified the polymer chain arrangement. Therefore, the chemical pathways resulted in two distinct low molecular weight chitosans, which allows different applications in food science. Unlabelled Image • Acidic and oxidative treatments reduced the molecular weight of chitosan (<50 kDa). • Both depolymerization reactions followed a mixed order reaction. • The depolymerization reactions reduced the crystalline domains. • The oxidative pathway induced minor structural changes. • The acid pathway induced structural alterations by formation of –NH3+Cl− salts. [ABSTRACT FROM AUTHOR]

Abstract The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nano-scale edges can act as 'nano-knives', which are able to cut the long chain of carboxymethyl cellulose (CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules (41,000 Da) were decomposed into a series of smaller molecules (460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution (2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared (FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional group β-1-4-glycosidic bond (wavenumber 1062 cm− 1) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of β-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Oil-tea camellia fruit shell (CFS) is a very abundant waste lignocellulosic resource. The current treatments of CFS, i.e. composting and burning, pose a severe threat on environment. Up to 50 % of the dry mass of CFS is composed of hemicelluloses. However, chemical structures of the hemicelluloses in CFS have not been extensively studied, which limits their high-value utilization. In this study, different types of hemicelluloses were isolated from CFS through alkali fractionation with the assistance of Ba(OH) 2 and H 3 BO 3. Xylan, galacto-glucomannan and xyloglucan were found to be the major hemicelluloses in CFS. Through methylation, HSQC and HMBC analyses, we have found that the xylan in CFS is composed of →4)-β-D-Xyl p -(1→ and →3,4)-β-D-Xyl p -(1→ linked by (1→4)-β glycosidic bond as the main chain; the side chains are α-L-Fuc p -(1→, →5)-α-L-Ara f -(1→, β-D-Xyl p -(1→, α-L-Rha p -(1→ and 4-O-Me-α-D-Glc p A-(1→, connected to the main chain through (1→3) glycosidic bond. The main chain of galacto-glucomannan in CFS consists of →6)-β-D-Glc p -(1→, →4)-β-D-Glc p -(1→, →4,6)-β-D-Glc p -(1→ and →4)-β-D-Man p -(1→; the side chains are β-D-Glc p -(1→, →2)-β-D-Gal p -(1→, β-D-Man p -(1→ and →6)-β-D-Gal p -(1→ connected to the main chain through (1→6) glycosidic bonds. Moreover, galactose residues are connected by α-L-Fuc p -(1→. The main chain of xyloglucan is composed of →4)-β-D-Glc p -(1→, →4,6)-β-D-Glc p -(1→ and →6)-β-D-Glc p -(1→; the side groups, i.e. β-D-Xyl p -(1→ and →4)-β-D-Xyl p -(1→, are connected to the main chain by (1→6) glycosidic bond; →2)-β-D-Gal p -(1→ and α-L-Fuc p -(1→ can also connect to →4)-β-D-Xyl p -(1→ forming di- or trisaccharide side chains. [ABSTRACT FROM AUTHOR]

High cellulose solubility is an essential to successful production of regenerated cellulose, from which hydrogels can be produced. Additionally, some pretreatment usually facilitates cellulose solubility. Bleached cellulose pulp from kenaf core (BK), consisting of lignin (0.3%), hemicellulose (5.2%) and ash (0%), was treated with an electron beam irradiation (EBI) at 10, 30, 50 and 70 kGy. The BK and irradiated bleached cellulose pulp (IK) were then dissolved in either sodium hydroxide/urea or lithium hydroxide/urea solvents which subsequently crosslinked with epichlorohydrin (ECH) solution to stabilize the formation of regenerated cellulose hydrogels. The amount of α-cellulose component in IK samples decreased as much as 38% and caused the viscosity average molecular weight (Mv) and degree of polymerization of IK samples to be reduced significantly by 84 and 87%, respectively. This resulted in an increase in cellulose solubility (up to 30%) for the IK samples in both solvent systems. However, this treatment resulted in a reduction in the overall cellulose fibre strength. X-ray diffraction of the hydrogels showed a transformation from cellulose I to amorphous cellulose. These hydrogels exhibited a higher degree of swelling, transparency and porosity compared to hydrogels prepared from non-irradiated pulp. [ABSTRACT FROM AUTHOR]

In this paper is presented a novel and simple synthetic pathway for obtaining new protected and unprotected N-glucosyl amino acids from 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl amine and Fmoc-l-amino acids. Three methodologies were evaluated, using the coupling reagents: N,N,N′,N′-Tetramethyl-O-(benzotriazol-1-yl)uronium tetrafluoroborate, diisopropylcarbodiimide and propylphosphonic acid cyclic anhydride. The obtained products using propylphosphonic acid cyclic anhydride showed less undesired species, easy purification and higher yields than the other two methodologies. Deprotection strategies widely used in solid phase peptide synthesis were applied to develop the synthetic pathway reported and achieve the final products. The protected and unprotected N-glucosyl amino acids were purified using solid phase extraction chromatography and characterized by high performance liquid Chromatography and nuclear magnetic resonance spectroscopy. Different amino acids (Fmoc-l-Asp(OtBu)OH, Fmoc-l-Phe(OH) and Fmoc-l-Lys(Boc)-OH) have been employed to demonstrate the simple and reproducible coupling methodology using propylphosphonic acid cyclic anhydride. The results showed that new protected and unprotected N-glucosyl amino acids can be obtained with high purity and the methodology could be used with any Fmoc-amino acid. The methodology developed could be considered as a synthetic tool for obtaining building blocks for glycopeptide synthesis and potential drugs candidates based on glycoconjugates. [ABSTRACT FROM AUTHOR]

We used matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) to analyze sucrose with a charcoal matrix and different cationization agents: Li+, Na+, K+, Rb+, Ag+, and Cs+. We observed a higher cation‐adducted sucrose peak with significantly reduced interference when analyzing sucrose with a charcoal matrix rather than 2,5‐dihydroxybenzoic acid (DHB) or α‐cyano‐4‐hydroxycinnamic acid (CHCA). However, the charcoal matrix caused glycosidic bond cleavage, resulting in sucrose fragment peaks. These could not be removed, even when we reduced the laser intensity. The degree of sucrose fragmentation was inversely related to the size of the cation additive. More sucrose fragmentation occurred when we used small cationization agents (Li+, Na+, or Ag+), while little fragmentation occurred when we used relatively large cationization agents (K+, Rb+, or Cs+). Charcoal has a higher energy transfer efficiency than DHB or CHCA as a matrix in MALDI‐MS. This may explain the increase in sucrose peaks and fragmented peaks observed when sucrose was analyzed with a charcoal matrix. The energy transfer efficiency was inversely proportional to the size of the cationization agent. [ABSTRACT FROM AUTHOR]

In chemical glycosylation reactions, a glycosyl donor couples with a glycosyl acceptor through glycosidic linkage. Most of the products end up with a mixture due to the formation of a stereogenic center at the anomeric carbon. Activation with a suitable Lewis acid and introduction of the non‐participating protecting group on donor and acceptor results in a selective product. Herein, we used a suitably protected donor and acceptor which produced an orthogonally protected building block with α‐selectivity. We used also a donor for the synthesis of modified phosphoribosylated amino acid. The formation of glycoside products can be used to synthesize complex biologically important organic molecules. [ABSTRACT FROM AUTHOR]

This work describes the possibility to hydrolyze rutin (quercetin-3- O -rutinoside) to quercetin using carbon dioxide (CO 2 ) and water without the addition of acids or enzymes. Eight hours of CO 2 -intensified hydrolysis of aqueous rutin-solutions were carried out to investigate temperature (373.15 K–433.15 K) and pressure dependence (4–150 bar). Both temperature and CO 2 -pressure dependence are studied. The parameter combination of 413.15 K and 150 bar gave a complete (100 %) conversion of rutin to quercetin. Temperature and pressure dependence were modelled. Models achieved correlation coefficients between R 2 = 0.85 and 0.99. Influence of H + ions was described by implementing the »H + -factor« to explain the hydrolysis effect of CO 2 -pressure in more detail. The results of this work demonstrate that CO 2 -intensified hydrolysis is possible at moderate temperatures and pressures. [ABSTRACT FROM AUTHOR]

[Display omitted] Employing the microhydration model that involves two to five explicit water molecules, two plausible dissociative hydrolysis pathways of 2′,3′-didehydro-2′,3′-dideoxyuridine (d4U), α-path with configuration-inversion and β-path with configuration-retention, have been investigated by M06-2X(CPCM)/6–31++G(d,p) method. Using this model, inclusion of three explicit water molecules (n = 3) is shown to be the smallest system that gives the minimal activation free energy for α-path and β-path. Our results suggest that the glycoside cleavage is the RDS, and α-path is more favorable kinetically than β-path. Whereas β-path with exergonic formation of β-dihydrofuran-like sugar with keto pyrimidine complex possesses thermodynamic preference over α-path, where the formation of α-dihydrofuran-like sugar with enol pyrimidine complex is endergonic. The free energy barriers of RDSs for d4U (25.8 kcal mol−1) and d4T (27.3 kcal mol−1) suggest that the glycosidic bond in d4T is more stable than that in d4U. The relative lower stability of d4U is probably an important factor for less antiviral activity of d4U. The small free energy barrier differences of ∼ 1 kcal mol−1 for β-path over α-path, and the reaction free energy differences of ∼ -12 kcal mol−1 for β-path lower than α-path in d4T and d4U suggest a competitive β-path in pyrimidine d4Ns. The higher free energy barriers of RDSs in ddU (27.6 kcal mol−1) and ddT (29.0 kcal mol−1) indicate that the saturated sugar moiety increases the stability of glycosidic bond in contrast to the unsaturated counter parts in d4U and d4T. NBO analysis also shows the kinetic preference of α-path over β-path. Our results provide an exploration for the less antiviral activity of d4U and the influence of saturated ribose on the glycosidic bond stability of pyrimidine d4Ns. [ABSTRACT FROM AUTHOR]

Aim To specifically investigate the effect of endodontic irrigants at their clinical concentration on matrix polysaccharides of cultured biofilms. Methodology Saccharolytic effects of 3% H2O2, 2% chlorhexidine ( CHX), 17% EDTA, 5% Na OCl and 0.9% saline (control) were tested using agarose (α 1-3 and β 1-4 glycosidic bonds) blocks ( n = 3) in a weight assay. The irrigants were also applied to three-species biofilms ( Streptococcus mutans UAB 159 , Streptococcus oralis OMZ 607 and Actinomyces oris OMZ 745) grown anaerobically on hydroxyapatite discs ( n = 6). Glycoconjugates in the matrix and total bacterial cell volumes were determined using combined Concanavalin A-/Syto 59-staining and confocal laser-scanning microscopy. Volumes of each scanned area (triplicates/sample) were calculated using Imaris software. Data were compared between groups using one-way anova/Tukey HSD, α = 0.05. Results The weight assay revealed that Na OCl was the only irrigant under investigation capable of dissolving the agarose blocks. Na OCl eradicated stainable matrix and bacteria in cultured biofilms after 1 min of exposure ( P < 0.05 compared to all groups, volumes in means ± standard deviation, 10−3 mm3 per 0.6 mm2 disc; Na OCl matrix: 0.10 ± 0.08, bacteria: 0.03 ± 0.06; saline control matrix: 4.01 ± 1.14, bacteria: 11.56 ± 3.02). EDTA also appeared to have some effect on the biofilm matrix ( EDTA matrix: 1.90 ± 0.33, bacteria: 9.26 ± 2.21), whilst H2O2 and CHX merely reduced bacterial cell volumes. Conclusion Sodium hypochlorite can break glycosidic bonds. It dissolves glycoconjugates in the biofilm matrix. It also lyses bacterial cells. [ABSTRACT FROM AUTHOR]

Short chain fatty acids (SCFA) are the major products of carbohydrate fermentation by gut bacteria. Different carbohydrates are associated with characteristic SCFA profiles although the mechanisms are unclear. The individual SCFA profile may determine any resultant health benefits. Understanding determinants of individual SCFA production would enable substrate choice to be tailored for colonic SCFA manipulation. To test the hypothesis that the orientation and position of the glycosidic bond is a determinant of SCFA production profile, a miniaturized in vitro human colonic batch fermentation model was used to study a range of isomeric glucose disaccharides. Diglucose α(1-1) fermentation led to significantly higher butyrate production (p < 0.01) and a lower proportion of acetate (p < 0.01) compared with other α bonded diglucoses. Diglucose β (1-4) also led to significantly higher butyrate production (p < 0.05) and significantly increased the proportions of propionate and butyrate compared with diglucose α (1-4) (p < 0.05). There was no significant effect of glycosidic bond configuration on absolute propionate production. Despite some differences in the SCFA production of different glucose disaccharides, there was no clear relationship between SCFA production and bond configuration, suggesting that other factors may be responsible for promoting selective SCFA production by the gut microbiota from different carbohydrates. [ABSTRACT FROM AUTHOR]

The presence of latent activities in enzymes is posited to underlie the natural evolution of new catalytic functions. However, the prevalence and extent of such substrate and catalytic ambiguity in evolved enzymes is difficult to address experimentally given the order-of-magnitude difference in the activities for native and, sometimes, promiscuous substrate/s. Further, such latent functions are of special interest when the activities concerned do not fall into the domain of substrate promiscuity. In the present study, we show a special case of such latent enzyme activity by demonstrating the presence of two mechanistically distinct reactions catalysed by the catalytic domain of receptor protein tyrosine phosphatase isoform δ (PTPRδ). The primary catalytic activity involves the hydrolysis of a phosphomonoester bond (C—O—P) with high catalytic efficiency, whereas the secondary activity is the hydrolysis of a glycosidic bond (C—O—C) with poorer catalytic efficiency. This enzyme also displays substrate promiscuity by hydrolysing diester bonds while being highly discriminative for its monoester substrates. To confirm these activities, we also demonstrated their presence on the catalytic domain of protein tyrosine phosphatase Ω (PTPRΩ), a homologue of PTPRδ. Studies on the rate, metal-ion dependence, pH dependence and inhibition of the respective activities showed that they are markedly different. This is the first study that demonstrates a novel sugar hydrolase and diesterase activity for the phosphatase domain (PD) of PTPRδ and PTPRΩ. This work has significant implications for both understanding the evolution of enzymatic activity and the possible physiological role of this new chemistry. Our findings suggest that the genome might harbour a wealth of such alternative latent enzyme activities in the same protein domain that renders our knowledge of metabolic networks incomplete. [ABSTRACT FROM AUTHOR]