Pyranose Ring Research Articles

Biofilms from Klebsiella pneumoniae: Matrix Polysaccharide Structure and Interactions with Antimicrobial Peptides.

Biofilm matrices of two Klebsiella pneumoniae clinical isolates, KpTs101 and KpTs113, were investigated for their polysaccharide composition and protective effects against antimicrobial peptides. Both strains were good biofilm producers, with KpTs113 forming flocs with very low adhesive properties to supports. Matrix exopolysaccharides were isolated and their monosaccharide composition and glycosidic linkage types were defined. KpTs101 polysaccharide is neutral and composed only of galactose, in both pyranose and furanose ring configurations. Conversely, KpTs113 polysaccharide is anionic due to glucuronic acid units, and also contains glucose and mannose residues. The susceptibility of the two strains to two bovine cathelicidin antimicrobial peptides, BMAP-27 and Bac7(1–35), was assessed using both planktonic cultures and biofilms. Biofilm matrices exerted a relevant protection against both antimicrobials, which act with quite different mechanisms. Similar protection was also detected when antimicrobial peptides were tested against planktonic bacteria in the presence of the polysaccharides extracted from KpTs101 and KpTs113 biofilms, suggesting sequestering adduct formation with antimicrobials. Circular dichroism experiments on BMAP-27 in the presence of increasing amounts of either polysaccharide confirmed their ability to interact with the peptide and induce an α-helical conformation.

Synthesis of the C8'-epimeric thymine pyranosyl amino acid core of amipurimycin.

The C8’-epimeric pyranosyl amino acid core 2 of amipurimycin was synthesized from D-glucose derived alcohol 3 in 13 steps and 14% overall yield. Thus, the Sharpless asymmetric epoxidation of allyl alcohol 7 followed by trimethyl borate mediated regio-selective oxirane ring opening with azide, afforded azido diol 10. The acid-catalyzed 1,2-acetonide ring opening in 10 concomitantly led to the formation of the pyranose ring skeleton to give 2,7-dioxabicyclo[3.2.1]octane 12. Functional group manipulation in 12 gave 21 that on stereoselective β-glycosylation afforded the pyranosyl thymine nucleoside 2 – a core of amipurimycin.

Uncovering the Relationship between Sulphation Patterns and Conformation of Iduronic Acid in Heparan Sulphate.

The L-iduronic acid (IdoA) residue is a critically important structural component in heparan sulphate polysaccharide for the biological functions. The pyranose ring of IdoA is present in 1C4-chair, 2SO-skew boat, and less frequently, in 4C1-chair conformations. Here, we analyzed the conformation of IdoA residue in eight hexasaccharides by NMR. The data demonstrate a correlation between the conformation of IdoA and sulphations in the surrounding saccharide residues. For the 2-O-sulpho IdoA residue, a high degree of sulphation on neighboring residues drives ring dynamics towards the 2SO-skew boat conformer. In contrast, the nonsulphated IdoA residue is pushed towards the 1C4-chair conformer when the neighboring residues are highly sulphated. Our data suggest that the conformation of IdoA is regulated by the sulphation pattern of nearby saccharides that is genetically controlled by the heparan sulphate biosynthetic pathway.

Preparation, characterization and antiglycation activities of the novel polysaccharides from Boletus snicus

Boletus snicus (BS) is one of the commercially important mushroom species. Two polysaccharides (BSP-1b and BSP-2b) were extracted and purified from the body of BS by DEAE-cellulose and Sephadex G-100 column chromatography. The average of molecular weight of BSP-1b and BSP-2b were 59.21kDa and 128.74kDa. BSP-1b is a heteropolysaccharide with a large number of glucose and a small amount of mannose, glucosamine hydrochloride and arabinose. The monosaccharide compositions of BSP-2b contain mannose, glucuronic acid, glucosamine hydrochloride, glucose, galactose, arabinose with the molar ratio of 10.70:6.95:12.05:12.57:1.83:1.00. The FTIR spectra and NMR analysis demonstrated that BSP-1b and BSP-2b existed pyranose ring structure and BSP-2b had high content of uronic acid. The antiglycation activities of BSP-1b and BSP-2b were investigated. The results showed BSP-1b and BSP-2b had high inhibitory effects on glycation and exhibited dose-dependent responses. BSP-2b showed stronger antiglycation activity than BSP-1b. This study indicated that the BSP-2b could effectively inhibit the formation of advanced glycation end-products.

The Dependence of Carbohydrate–Aromatic Interaction Strengths on the Structure of the Carbohydrate

Interactions between proteins and carbohydrates are ubiquitous in biology. Therefore, understanding the factors that determine their affinity and selectivity are correspondingly important. Herein, we have determined the relative strengths of intramolecular interactions between a series of monosaccharides and an aromatic ring close to the glycosylation site in an N-glycoprotein host. We employed the enhanced aromatic sequon, a structural motif found in the reverse turns of some N-glycoproteins, to facilitate face-to-face monosaccharide-aromatic interactions. A protein host was used because the dependence of the folding energetics on the identity of the monosaccharide can be accurately measured to assess the strength of the carbohydrate-aromatic interaction. Our data demonstrate that the carbohydrate-aromatic interaction strengths are moderately affected by changes in the stereochemistry and identity of the substituents on the pyranose rings of the sugars. Galactose seems to make the weakest and allose the strongest sugar-aromatic interactions, with glucose, N-acetylglucosamine (GlcNAc) and mannose in between. The NMR solution structures of several of the monosaccharide-containing N-glycoproteins were solved to further understand the origins of the similarities and differences between the monosaccharide-aromatic interaction energies. Peracetylation of the monosaccharides substantially increases the strength of the sugar-aromatic interaction in the context of our N-glycoprotein host. Finally, we discuss our results in light of recent literature regarding the contribution of electrostatics to CH-π interactions and speculate on what our observations imply about the absolute conservation of GlcNAc as the monosaccharide through which N-linked glycans are attached to glycoproteins in eukaryotes.

Structure and immunomodulatory activity of extracellular polysaccharide from Grifola frondosa

We aimed at analyzing the structure of extracellular polysaccharide A from Grifola frondosa (EXGFP-A) and testing its immunomodulatory activity. Structural analysis shows that EXGFP-A was a contained α-D-glucoside bond and pyranose ring. GC analysis reveals that EXGFP-A was mainly composed of rhamnose, arabinose, xylose, mannose, glucose, galactose, by the molar ratio of 0.28:0.31:0.30:0.06:7.98:0.61. The results of MTT(3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay indicates when EXGFP-A was at a concentration of 80 μg/mL and treatment time of 48 h, RAW264.7 cells proliferation index reached a maximum of 137.5%. Meanwhile, the AO staining showed that EXGFP-A activated RAW264.7 cells and improved the level of intracellular nucleic acid metabolism. In addition, in a certain range of concentration, EXGFP-A was able to increase the release of NO in RAW264.7 cells, and upregulate the mRNA expression of immunological factor TNF-α, IL-1β, IL-6, IL-12, IFN-γ and iNOS of RAW264.7 cells. Our results confirm that EXGFP-A had immunomodulatory activity. Our findings provided scientific basis for the structural analysis and application of Grifola frondosa polysaccharide.

Dynamical study of the water penetration process into a cellulose acetate film studied by coherent anti-Stokes Raman scattering (CARS) microspectroscopy

The penetration process of water into a cellulose acetate film was traced in real time by coherent anti-Stokes Raman scattering (CARS) microspectroscopy. The CO stretch mode was red-shifted due to hydrogen-bond formation. We also found that two Raman bands at 1605cm−1 and 1665cm−1 emerged only in the early stage of the water penetration process. Based on the combined analysis of the experimental and computational studies, these bands at 1605cm−1 and 1665cm−1 were assigned as the OH bend mode due to hydrogen-bonded penetrated water and hydrogen-bonded OH groups in pyranose rings, respectively.

The effect of manganese(II) chloride as a co-catalyst on cellobiose hydrolysis in dilute aqueous sulfuric acid and acidic ionic liquid mediums

The effects of adding MnCl2 as a co-catalyst on cellobiose hydrolysis in 0.016M aqueous H2SO4 and 0.032M 1-(1-propylsulfonic)-3-methylimidazolium chloride acidic ionic liquid mediums were studied at 60–90°C by measuring the glucose yields. The addition of MnCl2 produced enhancements in glucose yields in both aqueous acid mediums. The yield enhancements are highest at 60°C and gradually decrease at higher temperatures, suggesting that a weak interaction of MnCl2 with cellobiose causes the co-catalytic effect. FT-IR studies in the solid-state suggest that MnCl2 interacts with hydroxyl groups of cellobiose without causing significant changes in the pyranose ring conformations.

A Versatile Bioanode with Improved Current Density and the Coulombic Efficiency through a Cascade Reaction

To improve communications between enzymes and electrodes, many different methods were developed including the use of diffusional electron mediators, the “wiring” of enzymes through immobilization in redox polymers, the functionalization of enzymes with electron relays, and the use of nanomaterials. Recently a new promising strategy was reported, in which the glycoprotein glucose oxidase (GOx) was directly electrically contacted with the electrodes after removal of the glycosylating layer. Although a lot of advances in the electrical communication between enzymes and electrodes has made it possible to fabricate new biosensors and biofuel cells, the technologies still face challenging issues, such as development of long-term stable miniaturized implantable amperometric biosensors and biofuel cells. Our approach to the development of a glucose biofuel cell anode is based on the combination of different redox enzymes with complementary oxidation positions thus forming a reaction cascade to oxidize the substrate at more than one position. Improvements in current density and coulombic efficiency of a glucose oxidizing electrode were realized by a combination of pyranose dehydrogenase from Agaricus meleagris (AmPDH) with either glucose dehydrogenase from Glomerella cingulata (GcGDH) or cellobiose dehydrogenase from Myriococcum thermophilum (MtCDH). The mixed enzyme electrode oxidizes glucose in several combinations at the C-1, C-2 and C-3 positions of the pyranose ring. This concerted action of enzymes increases (i) the coulombic efficiency by extracting more than 2 e- per substrate molecule and (ii) the current density of the electrode when the mass-transfer of substrates becomes rate limiting. The electrodes were investigated with flow injection analysis (FIA) using different substrates under physiological conditions (pH 7.4). These investigations showed that the product of one enzyme can be used as substrate for the other enzyme and maximally 6 e- can be gained from the oxidation of one glucose molecule using mixed enzyme electrodes like AmPDHb/GcGDH/Os-polymer 2 or the AmPDHa/MtCDH/Os-polymer 1. We propose a bioanode for use in biofuel cells with an increased current density and coulombic efficiency obtained by a cascade reaction catalyzed by redox enzymes with a different site-specificity for glucose.

Active targeting of asiaglycoprotein receptor using sterically stabilized lipoplexes

The large numbers of hepatic disorders of a genetic origin continues to drive the quest for safe and efficient non‐viral gene delivery systems with the design features suitable for in vivo application. Here, we examine the efficacy of hepatocyte‐specific stealth lipoplexes in the human hepatoma cell line HepG2. Thus cationic liposomes were formulated with the cytofectin N,N‐dimethylaminopropylaminylsuccinylcholesterylformylhydrazide (MS09), the neutral co‐lipid 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine (DOPE) with and without the asialoglycoprotein receptor (ASGP‐R)‐specific ligand cholesteryl‐β‐d‐galactopyranoside (Chol‐β‐Gal), and 1,2‐distearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[methoxy(polyethylene glycol) 2000] (DSPE‐PEG2000) in the 0–5 mol% range. Lipoplexes formed with pCMV‐luc plasmid DNA were characterized by cryo‐transmission electron microscopy (cryo‐TEM), gel retardation, and ethidium displacement assays showed that cargo DNA was compacted and protected from serum nucleases by cationic liposomes. Hydrodynamic diameters were in the 114 ± 6.2–224 ± 5.3 nm size range while particle sizes, polydispersity indices (PDI), and ζ‐potentials decreased with increasing degree of PEGylation. Cell viabilities of >75% were attained by targeted complexes in the ASGP‐R‐negative human embryonal kidney cell line HEK293 and in ASGP‐R‐positive HepG2 cells. Targeted 5% PEGylated lipoplexes at N/P ratio = 3.5 achieved the highest transfection activity in the hepatocyte‐derived cells while competition assays and fluorescence microscopy confirmed that all targeted lipoplexes transfected HepG2 cells largely by ASGP‐R mediation.Practical applications: The findings of this study show that stealth lipoplexes bearing PEG2000 at a density of 5 mol% may be effectively targeted to the ASGP‐R, which is almost exclusively expressed on hepatocytes and hepatocyte‐derived cells, by inclusion of the simple monoantennary cholesteryl‐β‐d‐galactopyranoside at 10 mol% in the parent cationic liposome preparation. The remarkable efficacy of this cholesteryl glycoside ligand, in the presence of serum, shows that a β‐glycosidic link between the cholesteryl membrane anchor moiety and the pyranose ring is sufficient to ensure efficient ASGP‐R recognition of the sugar hexose at clinically relevant PEG grafting densities, by lipoplexes into which it has been incorporated. We conclude that the targeted, PEGylated lipoplexes characterized and evaluated in this study constitute a solid platform for the development of hepatotropic nucleic acid delivery vehicles.This study shows that stealth lipoplexes bearing PEG2000 at a density of 5 mol% may be effectively targeted to the asialoglycoprotein receptor (ASGP‐R), which is almost exclusively expressed on hepatocytes and hepatocyte‐derived cells, by inclusion of the simple monoantennary cholesteryl‐β‐d‐galactopyranoside at 10 mol% in the parent cationic liposome preparation. The remarkable efficacy of this cholesteryl glycoside ligand, in the presence of serum, shows that a β‐glycosidic link between the cholesteryl membrane anchor and the pyranose ring is sufficient to ensure efficient ASGP‐R recognition of the sugar hexose at clinically relevant PEG grafting densities. Targeted, PEGylated lipoplexes characterized and evaluated here, constitute a solid platform for the development of hepatotropic nucleic acid delivery vehicles.

Role of molecular structure of monosaccharides on the viscosity of aqueous nanometric alumina suspensions

The effect of molecular structure of d-galactose, d-mannose, d-glucose, 2-deoxy-d-glucose and 3-O-methyl-d-glucose on the viscosity of aqueous alumina nanoparticle suspensions was investigated by rheological measurements. The viscosity was found to be dependant on the molecular structure of these hexopyranoses. The research reveals that the orientation of primary and quaternary hydroxyl groups in a pyranose ring plays a crucial role in dispersing properties of monosaccharides. Moreover, the most important is the mutual orientation of these hydroxyl groups. Monosaccharides with axial and equatorial orientation of hydroxyl groups at first (C1) and fourth (C4) carbon atom in pyranose ring decrease the viscosity more than monosaccharides with two axial hydroxyl groups in these positions. Due to the differences in molecular structure of saccharides resulting in different shape of molecules and different compatibility to the water structure, the saccharides differ in ability to disturb water layers around alumina particles.

Hollow optical-fiber based infrared spectroscopy for measurement of blood glucose level by using multi-reflection prism.

A mid-infrared attenuated total reflection (ATR) spectroscopy system employing hollow optical fibers and a trapezoidal multi-reflection ATR prism has been developed to measure blood glucose levels. Using a multi-reflection prism brought about higher sensitivity, and the flat and wide contact surface of the prism resulted in higher measurement reproducibility. An analysis of in vivo measurements of human inner lip mucosa revealed clear signatures of glucose in the difference spectra between ones taken during the fasting state and ones taken after ingestion of glucose solutions. A calibration plot based on the absorption peak at 1155 cm(-1) that originates from the pyranose ring structure of glucose gave measurement errors less than 20%.

Kinetic characteristics of conformational changes in the hexopyranose rings

The shape of the hexopyranose ring is an important factor which can influence the properties of carbohydrate molecules and affect their biological activity. Due to a limited availability of the experimental data, the conformational rearrangements (puckering) which occur within the pyranose rings are studied extensively by using various computational approaches. Contrary to the basic structural and energetic features characterizing the process of ring flexing, the kinetic and dynamics properties of puckering remain less recognized. We performed the first, molecular dynamics-based, systematic calculations aimed at description of the kinetic characteristics of the conformational changes in the rings of α-d- and β-d-glucopyranose molecules. The rate constants representing particular molecular events which comprise the chair–chair inversion are determined and analyzed in the context of the available experimental data. Furthermore, several various variables (e.g. transmission coefficients) and issues (e.g. memorylessness of the puckering process) are investigated and discussed. As several different parameter sets were used during the study (GROMOS 56A6CARBO, GLYCAM, GROMOS 53A6GLYC), the results provide the conclusion on the capability of the carbohydrate-dedicated force fields to describe the kinetic properties of pyranose ring flexing.

A Versatile Bioanode with Improved Current Density and the Coulombic Efficiency through a Cascade Reaction

To improve communications between enzymes and electrodes, many different methods were developed including the use of diffusional electron mediators, the “wiring” of enzymes through immobilization in redox polymers, the functionalization of enzymes with electron relays, and the use of nanomaterials. Recently a new promising strategy was reported, in which the glycoprotein glucose oxidase (GOx) was directly electrically contacted with the electrodes after removal of the glycosylating layer. Although a lot of advances in the electrical communication between enzymes and electrodes has made it possible to fabricate new biosensors and biofuel cells, the technologies still face challenging issues, such as development of long-term stable miniaturized implantable amperometric biosensors and biofuel cells. Our approach to the development of a glucose biofuel cell anode is based on the combination of different redox enzymes with complementary oxidation positions thus forming a reaction cascade to oxidize the substrate at more than one position. Improvements in current density and coulombic efficiency of a glucose oxidizing electrode were realized by a combination of pyranose dehydrogenase from Agaricus meleagris (AmPDH) with either glucose dehydrogenase from Glomerella cingulata (GcGDH) or cellobiose dehydrogenase from Myriococcum thermophilum (MtCDH). The mixed enzyme electrode oxidizes glucose in several combinations at the C-1, C-2 and C-3 positions of the pyranose ring. This concerted action of enzymes increases (i) the coulombic efficiency by extracting more than 2 e- per substrate molecule and (ii) the current density of the electrode when the mass-transfer of substrates becomes rate limiting. The electrodes were investigated with flow injection analysis (FIA) using different substrates under physiological conditions (pH 7.4). These investigations showed that the product of one enzyme can be used as substrate for the other enzyme and maximally 6 e- can be gained from the oxidation of one glucose molecule using mixed enzyme electrodes like AmPDHb/GcGDH/Os-polymer 2 or the AmPDHa/MtCDH/Os-polymer 1. We propose a bioanode for use in biofuel cells with an increased current density and coulombic efficiency obtained by a cascade reaction catalyzed by redox enzymes with a different site-specificity for glucose. Key words: Bio-anode, glucose dehydrogenase, Os-polymers, pyranose dehydrogenase, cellobiose dehydrogenase, coulombic efficiency

Cello-oligomer-binding dynamics and directionality in family 4 carbohydrate-binding modules.

Carbohydrate-binding modules (CBMs) play significant roles in modulating the function of cellulases, and understanding the protein-carbohydrate recognition mechanisms by which CBMs selectively bind substrate is critical to development of enhanced biomass conversion technology. CBMs exhibit a limited range of specificity and appear to bind polysaccharides in a directional fashion dictated by the position of the ring oxygen relative to the protein fold. The two family 4 CBMs of Cellulomonas fimi Cel9B (CfCBM4) are reported to preferentially bind cellulosic substrates. However, experimental evidence suggests that these CBMs may not exhibit a thermodynamic preference for a particular orientation. We use molecular dynamics (MD) and free energy calculations to investigate protein-carbohydrate recognition mechanisms in CfCBM4-1 and CfCBM4-2 and to elucidate preferential ligand-binding orientation. We evaluate four cellopentaose orientations including that of the crystal structure and three others suggested by nuclear magnetic resonance (NMR). These four orientations differ based on position of the ligand reducing end (RE) and pyranose ring orientations relative to the protein core. MD simulations indicate that the plausible orientations reduce to two conformations. Calculated ligand-binding free energy discerns each of the orientations is equally favorable. The calculated free energies are in excellent agreement with isothermal titration calorimetry measurements from the literature. MD simulations further reveal the approximate structural symmetry of the oligosaccharides relative to the amino acids along the binding cleft plays a role in the promiscuity of ligand binding. A survey of ligand-bound structures suggests this phenomenon may be characteristic of the broader class of proteins belonging to the β-sandwich fold.

Xylapyrrosides A and B, two rare sugar-morpholine spiroketal pyrrole-derived alkaloids from Xylaria nigripes: isolation, complete structure elucidation, and total syntheses

Two new [named xylapyrrosides A (1) and B (2)] along with two known [pollenopyrrosides A (3) and B (=acortatarin A, 4)] naturally occurring spirocyclic pyrrole alkaloids were isolated and identified as minor components from the EtOH extract of the dried mycelia of the edible medicinal fungus Xylaria nigripes. Their structures were established by a combination of interpretation of spectroscopic data and single-crystal X-ray diffraction analyses. The isolates possess a unique tricyclic skeleton comprising a common bicyclic 2-formyl-pyrrole-fused morpholine, with a variable ketohexoside ring. This class of alkaloids is quite rare from natural sources. In this study, the total syntheses of compounds 1, 2 and 4 were successfully achieved by two alternative strategies, and three new analogs [named xylapyrrosides A1 (1a), A2 (1b) and B1 (2a)] were also produced. Notably, the total synthesis of such spiroketal alkaloids with a pyranose ring (e.g.,1) was accomplished for the first time. The absolute configurations of the new isolates can be thereafter unequivocally secured by the total syntheses. The above isolated and synthesized spiro-alkaloids were found to show moderate antioxidant effects by preventing the oxidative stress-induced cytotoxicity of A7r5 rat vascular smooth muscle cells (VSMCs).

Cellulose-based novel hybrid polymer electrolytes for green and efficient Na-ion batteries

In the present work, a novel pyranose ring laden polymer electrolyte is proposed for all solid Na-ion secondary cells that can operate at moderate temperatures. The prepared fully solid polymer electrolyte film is based on a classic polyethylene oxide (PEO) backbone, homogeneously blended with sodium carboxymethyl cellulose (Na-CMC) and sodium perchlorate. The favourable use of Na-CMC as electrode binder as well as electrolyte additive is evaluated, which would enhance the pathways for forming an optimised electrode/electrolyte interface. The promising prospects of the newly elaborated hybrid electrolyte are investigated by means of galvanostatic charge/discharge cycling in lab-scale cell with TiO2-based or NaFePO4-based working electrodes.

Revealing the Hydrophobicity of Natural Cellulose by Single-Molecule Experiments

Natural cellulose (NC) is the most abundant biomacromolecule. The fact that each pyranose ring of NC has three hydroxyl groups implies that NC should be highly hydrophilic. The paradoxical water insolubility of NC is usually explained by the strong tendency to form the hydrogen-bonding network by the high content of hydroxyl groups. In this study, we present the first experimental evidence that NC is rather hydrophobic, even if the chains are molecularly dispersed. By single-molecule force spectroscopy, the single-chain mechanics of NC has been studied in various liquid environments. In a common nonpolar solvent, octane, NC shows the elastic force–extension (F–E) curve. We find that this kind of F–E curve can be fitted well by the QM-FJC model, in which the single-chain elasticity obtained from quantum mechanical (QM) calculations is integrated into the freely jointed-chain (FJC) model. However, the result of NC obtained in water is different, which shows a long plateau in the F–E curve. Further study shows that the height of the plateau is temperature dependent. However, the plateau disappears when an 8 M urea solution is used as the liquid environment. AFM images obtained in water show that single NC chains exist in a compact globule conformation on the sample surface. According to the molecular structure, methylcellulose (MC) should be more hydrophobic than NC. However, no plateau can be observed from the MC samples in water. On the basis of all the results above, we can draw a conclusion that both of the hydrophobic effect and the crystallization of NC contribute to the plateau in the F–E curve obtained in water. The experimental observation of the hydrophobic nature of NC at the single-chain level provides new insights into the understanding of NC.

High‐temperature molecular dynamics simulation of cellobiose and maltose

Thermochemical conversion of lignocellulosic biomass to renewable fuels and chemicals occurs through high temperature decomposition of the main structural components in plants, including cellulose, hemicellulose, and lignin. Cellulose and hemicellulose comprise mostly carbohydrates. Two disaccharides, maltose and cellobiose, are used as model compounds to explore differences in thermal stability due to the orientation of the glycosidic bond. First principles molecular dynamics and density functional theory have been used to probe the decomposition of these disaccharides during pyrolysis at 700 K. The results suggest that maltose, the α‐disaccharide, is less thermally stable. Dynamic bond length analysis for maltose indicates that several CC bonds and the CO bonds on the pyranose ring demonstrate signs of weakening, whereas no such scissile bonds were identified for cellobiose. The higher stability of the cellobiose is believed to originate from the persistence of low‐energy hydroxymethyl conformers throughout the simulation which enable strong inter‐ring hydrogen bonding. Thermogravimetric and mass spectroscopic experiments corroborate the enhanced thermal stability of cellobiose, wherein the onset of decomposition was observed at higher temperatures for cellobiose than for maltose. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2562–2570, 2015

Opening of the 1,6-anhydro bridge with selective reduction of the acetal moiety in levoglucosenone and its derivatives

Treatment of levoglucosenone and some its derivatives with chloro(trimethyl)silane and sodium iodide in acetonitrile leads to opening of the 1,6-anhydro bridge and simultaneous reduction of the pyranose ring to pyran.