Synthesis of 2,3-O-benzyl-ribose and xylose and their equilibration

The preparation and NMR analysis of 2,3-di-O-benzyl d-ribose and 2,3-di-O-d-xylose are described. In DMSO-d₆ the sugars adopt a conformation in which the hydroxyl groups are in an equatorial position. In CDCl₃ and CD₂Cl₂ the sugars adopts a conformation in which intramolecular hydrogen bonding plays an important role in determining the equilibrium composition. These findings were also confirmed by DFT studies and, in the solid phase, by X-ray single crystal diffraction.     

A site-specific and multi-element isotopic approach to origin inference of sugars in foods and beverages

A strategy is presented for the characterization of sugars according to their botanical origin. The samples fermented in standardized conditions can be described in the multi-dimensional space of the overall carbon isotope ratio of ethanol measured by isotope ratio mass spectrometry (IRMS) and of the specific hydrogen isotope parameters of the methyl and methylene sites derived from nuclear magnetic resonance investigation of site-specific natural isotope fractionation (SNIF-NMR method). In the comparison of natural juices, the deuterium and oxygen-18 parameters of water extracted from the juice and from the end fermentation medium also contain information on the origin of the product. The isotopic effects of the concentration processes leading to concentrated juices, musts and syrups can be estimated and taken into account in interpreting the data.The classification power of this multi-element and multi-site approach is illustrated by discriminant analyses involving selected isotopic variables associated with pineapple, apple and barley sugars, compared to beet and cane sugars which are common sources of enrichment. The ability of the method to detect adulteration by exogeneous sugars is improved when environmental conditions can be taken into account.     

Preparation of starch and soluble sugars of plant material for the analysis of carbon isotope composition: a comparison of methods

Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO₂ fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO₂ flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements. We here report on the comparison and evaluation of existing methods (acid and enzymatic hydrolysis for starch; ion‐exchange purification and compound‐specific analysis for sugars). The selectivity and reproducibility of the methods were tested using three approaches: (i) an artificial leaf composed of a mixture of isotopically defined compounds, (ii) a C₄ leaf spiked with C₃ starch, and (iii) two natural plant samples (root, leaf). Starch preparation methods based on enzymatic or acid hydrolysis did not yield similar results and exhibited contaminations by non‐starch compounds. The specificity of the acidic hydrolysis method was especially low, and we therefore suggest terming these preparations as HCl‐hydrolysable carbon, rather than starch. Despite being more specific, enzyme‐based methods to isolate starch also need to be further optimized to increase specificity. The analysis of sugars by ion‐exchange methods (bulk preparations) was fast but produced more variable isotope compositions than compound‐specific methods. Compound‐specific approaches did not in all cases correctly reproduce the target values, mainly due to unsatisfactory separation of sugars and background contamination. Our study demonstrates that, despite their wide application, methods for the preparation of starch and soluble sugars for the analysis of carbon isotope composition are not (yet) reliable enough to be routinely applied and further research is urgently needed to resolve the identified problems. Copyright © 2009 John Wiley & Sons, Ltd.     

Separation of oligo- and polysaccharides by capillary supercritical fluid chromatography

Direct analysis of polar solutes by supercritical fluid chromatography (SFC) has been somewhat limited because the mobile phases in common use are all relatively nonpolar. Derivatization is demonstrated as a viable means for facilitating the SFC separation of sugars. Oligo- and polysaccharides containing up to 18 glucose units are completely resolved by capillary SFC.     

稀有糖的合成方法研究

稀有糖广泛存在于天然产物及药物分子中, 并发挥着重要的生物作用. 药物分子的糖基多样化修饰使得稀有糖的合成受到越来越多的关注. 从以普通糖为原料合成稀有糖和以非糖化合物为原料合成稀有糖两个方面综述了近年来的稀有糖合成进展.     

Determination of mono- and disaccharides by capillary electrophoresis with contactless conductivity detection

The separation and detection of common mono- and disaccharides by capillary electrophoresis (CE) with contactless conductivity detection (CCD) is presented. At high values of pH, the sugars are converted to anionic species that can be separated by CE and indirectly detected by CCD. The main anionic species present in the running electrolytes are hydroxide and phosphate, which have greater mobility than the ionized sugars, and, thus, the indirect detection is possible. The method was applied to analysis of glucose, fructose, and sucrose in soft drinks, isotonic beverages, fruit juice, and sugarcane spirits. Galactose was used as internal standard in all cases. Plate numbers range from ca. 70,700 to 168,200 and the limits of detection from 13 to 31 microM.     

Synthesis of Novel 1-(substituted phenyl)-2-phospholene 1-Oxide Derivatives

Several novel 1-(substituted phenyl)-2-phospholene 1-oxide derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen of normal sugars, were synthesized from the corresponding 2-phospholenes as the starting materials. Structures of all the synthesized compounds were unequivocally confirmed by IR, 1 H, 13 C, and 31 P NMR spectral, elemental, and X-ray crystallographic analyses.     

Rapid estimation of global sugars by UV photodegradation and UV spectrophotometry

The UV/UV method developed for the measurement of specific wastewater pollution parameters (ammonium, Kjeldahl nitrogen, total phosphorus) is adapted to the determination of sugars in fruit juices and soft drinks. The procedure is based on the UV spectrophotometric detection of by-products of UV photodegradation of carbohydrates. Time of analysis is greatly reduced by using specific pH conditions and diluted samples.     

Determination of oligofructose, a soluble dietary fiber, by high-temperature capillary gas chromatography

A high-temperature capillary gas chromatographic method was developed for the quantitative determination of oligofructose in foods and food products. Sample preparation involves oxymation and silylation of the extracted sugars. The oximetrimethylsilyl derivatives are analyzed on an apolar capillary column, with detection by flame ionization. The method is accurate, with recovery of spiked samples at >96%. Repeatability was excellent; RSD values of 1.1% were obtained. Other common oligosaccharides, such as malto-, isomalto-, and galactooligosaccharides, and levan do not interfere, making the method specific and reliable.     

X-ray ionization and fragmentation for use with time-of-flight mass spectrometry

In this paper, we introduce laser desorption X-ray ionization for producing ions from the previously undetected neutral species present during laser desorption mass spectrometry. Studies involving the laser desorption of simple sugars were conducted to illustrate the differences between spectra with and without the X-ray source. Ionization was made possible by placing a 200 mCi Am X-ray source directly into the ionization chamber of a time-of-flight mass spectrometer.     

Trace analysis of sugars by HPLC and post-column derivatization

Summary A HPLC system with post-column derivatization for the quantitative analysis of sugars in complex matrices is described. As reagent a 0.2% solution of thymol in concentrated sulfuric acid has been used. The reaction is sensitive with reducing as well as non reducing sugars whereas sugar alcohols are discriminated. With this reagent and separation of sugars at high pH values with an anion exchange column it is possible to detect sugars in the ng range. Hence, it is possible to characterize wines not only by their fructose and glucose content but also by differences in the distribution of the other not fermentable sugars like trehalose, arabinose, galacturonic and glucuronic acid.     

Carbohydrate profiling of bacteria by gas chromatography-mass spectrometry and their trace detection in complex matrices by gas chromatography-tandem mass spectrometry.

Bacterial cellular polysaccharides are composed of a variety of sugar monomers. These sugars serve as chemical markers to identify specific species or genera or to determine their physiological status. Some of these markers can also be used for trace detection of bacteria or their constituents in complex clinical or environmental matrices. Analyses are performed, in our hands, employing hydrolysis followed by the alditol acetate derivatization procedure. Substantial improvements have been made to sample preparation including simplification and computer-controlled automation. For characterization of whole cell bacterial hydrolysates, sugars are analyzed by gas chromatography-mass spectrometry (GC-MS). Simple chromatograms are generated using selected ion monitoring (SIM). Using total ion GC-MS, sugars can be readily identified. In more complex clinical and environmental samples, markers for bacteria are present at sufficiently low concentrations that more advanced instrumentation, gas chromatography-tandem mass spectrometry (GC-MS-MS), is preferred for optimal analysis. Using multiple reaction monitoring, MS-MS is used (replacing more conventional SIM) to ignore extraneous chromatographic peaks. Triple quadrupole and ion trap GC-MS-MS instruments have both been used successfully. Absolute chemical identification of sugar markers at trace levels is achieved, using MS-MS, by the product spectrum.     

Ag+生物吸附的谱学研究

我们曾经研究了地衣芽孢杆菌R08和啤酒酵母废菌体吸附Pd2+以及巨大芽孢杆菌D01吸附Au3+过程的作用机理。有关乳酸杆菌A09吸附Ag+1的作用特点已有报道。本文在此基础上，进一步用谱学技术研究A09菌体吸附还原Ag+的作用机理。     

Innershell absorption spectroscopy of amino acids at all relevant absorption edges

The C, N, and O K-edge near-edge X-ray absorption fine structure spectra of the 22 most common proteinogenic alpha-amino acids in the zwitterionic form collected from solvent-free polycrystalline powder films in the partial electron yield mode are reported. Spectral features common to all amino acids, as well as distinctive fingerprints of specific subgroups of these compounds, are presented and discussed.     

Phenylboronic acid functionalized SBA-15 for sugar capture

The synthesis and characterization of organic-inorganic hybrid materials that selectively capture sugars from model biomass hydrolysis mixtures are reported. 3-Aminophenylboronic acid (PBA) groups that can reversibly form cyclic esters with 1,2-diols, and 1,3-diols including sugars are attached to mesoporous SBA-15 via different synthetic protocols. In the first route, a coupling agent is used to link PBA and SBA-15, while in the second route poly(acrylic acid) brushes are first grafted from the surface of SBA-15 by surface-initiated atom transfer radical polymerization and PBA is then immobilized. The changes in pore structure, porosity, and pore size due to the loading of organic content are measured by powder X-ray diffraction and nitrogen porosimetry. The increase in organic content after each synthesis step is monitored by thermal gravimetric analysis. Fourier transform infrared spectroscopy and elemental analysis are used to characterize the chemical compositions of the hybrid materials synthesized. D-(+)-Glucose and D-(+)-xylose, being the most commonly present sugars in biomass, are chosen to evaluate the sugar adsorption capacity of the hybrid materials. It is found that the sugar adsorption capacity is determined by the loading of boronic acid groups on the hybrid materials, and the hybrid material synthesized via route two is much better than that through route one for sugar adsorption. Mathematical modeling of the adsorption data indicates that the Langmuir model best describes the sugar adsorption behavior of the hybrid material synthesized through route one, while the Freundlich model fits the data most satisfactorily for the hybrid material prepared via route two. The adsorption kinetics, reusability, and selectivity toward some typical chemicals in cellulose acidic hydrolysis mixtures are also investigated.     

Novel Synthesis and Structure of Phosphanyl Sugar Derivatives 1

Abstract

Some phosphanyl sugar derivatives, which are analogs of sugars having a phosphorus atom in place of the ring oxygen, were synthesized from 2- and 3-phospholenes as starting materials. Catalytic cis-dihydroxylation of 2-phospholene or 3-phospholene 1-oxide derivatives with osmium(VIII) oxide in the presence of a cooxidant afforded 3-deoxy- or 1-deoxy-tetrofuranose-type phosphanyl sugar derivatives, respectively. cis- Dihydroxylation of 4-acyloxy-2-phospholene 1-oxide derivatives gave tetrofuranose type phosphanyl sugar derivatives. Some of these derivatives of phosphanyl sugars were subjected to structural analyses using ¹H NMR and X-ray crystallography.

     

Indirect fluorescence detection of amino sugars with the use of copper complexes of tryptophan and its analogues following high-performance liquid chromatographic separation

A simple, indirect fluorescence detection method has been developed for detecting specific mono-amino sugars (D-glucosamine, D-galactosamine, D-mannosamine) following chromatographic separation. The eluting amino sugars release L-tryptophan (L-Trp) from a copper-tryptophan complex which is introduced postcolumn. Analyte detection is based on measuring the increase in L-Trp fluorescence, which is quenched when complexed with copper. Two tryptophan analogues, 5-hydroxy-L-tryptophan (5-HTP) and DL-5-methoxytryptophan (5-MTP), were also evaluated as postcolumn reagents. 5-MTP was found to be a suitable alternative to L-Trp for the detection of these mono-amino sugars. Detection limits for D-glucosamine, D-galactosamine, and D-mannosamine are in the range of 0.15-0.30 nmol injected.     

AFM observation of ultrathin microfibrils in fruit tissues

Polysaccharide microfibrils in fruit tissue of higher plants (strawberry, peach, and rambutan) were examined by atomic force microscopy (AFM). For preserving native cellulose microfibrils, a combination of 2% NaClO₂ and 4% NaOH extraction was applied to the materials. This corresponds to mild alkali extractin of holocellulose, and denoted here as weak alkali-resistant polysaccharide, WARP. The amount of neutral sugars corresponded to 53–95% of that of WARP. Glucose was the most abundant in the neutral sugars, being 74–87%. AFM examination of microfibrils dispersed on mica substrate allowed accurate determination of fibril widths as 1.0–2.0 nm. Their straight fibrillar shape and the results of X-ray diffraction and infrared spectroscopy indicate that these fibrils are cellulose. These results constitute direct evidence for existence of ultrafine cellulose microfibrils hitherto assumed from X-ray diffraction and NMR analyses.     

巨大芽孢杆菌D01吸附金(AU3+)的谱学表征

对休眠的巨大芽孢杆菌(Bacillus megatherium)D01菌体吸附Au^3 的作用过程进行了谱学表征．运用AAS考察了pH、时间和温度对D01菌体吸附Au^3 过程的化学动力学和热力学相关参数的影响．D01菌粉中硫元素含量的EDX分析说明该菌体中对Au^3 具有还原作用的L-半胱氨酸和蛋氨酸的含量极少;D01菌体水解后葡萄糖含量的UV-vis测定说明该菌体水解产物中含有一定量的还原糖,空白的和吸附Au^3 的D01菌体的FFIR检测表明该菌体细胞壁肽聚糖层糖类化合物的羟基和肽链侧链氨基酸残基离子化羧基为吸附Au^3 的活性基团;肽聚糖层部分多糖的水解产物低聚糖、二糖及单糖等还原糖的半缩醛羟基游离态醛基为电子供体,将Au^3 原位还原成Au^0．葡萄糖和Au^3 相互作用的XRD和FFIR表征证明Au^3 是在还原糖的醛基上直接被还原成Au^0．     

Advances in identification of plant gums in cultural heritage by thermally assisted hydrolysis and methylation

Plant gums are present in works of art as binding media for watercolours and adhesives for cellulosic substrates. Thermally assisted hydrolysis and methylation (THM) in combination with analytical pyrolysis coupled to GC/MS has been applied to the characterisation of plant gums typically used in artworks. THM products from standard samples of arabic gum, tragacanth gum and cherry gum were characterised. The main products identified are permethylated and partially methylated aldonic acids, characteristic of specific epimeric sugars. Aldonic acids were formed by alkaline hydrolysis of free reducing sugars and of reducing polysaccharide terminal groups, while methylation occurs during pyrolysis. The presence of these characteristic markers allows gum identification. A systematic analysis of all the parameters that can affect the marker yields was performed. In particular, the influence of pyrolysis temperature, reagent concentration and contact time between tetramethylammonium hydroxide and sample were studied, and different kinds of sample preparation procedures were tested. Some analyses on real watercolours were performed, and gum binders were classified using the peak area ratio of the main monosaccharide markers.