Cellulose methylation analysis

What products would you expect from cellulose as a result of methylation analysis Periodate oxidation The Smith degradation The action of an alpha amylase ... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

Particulate membrane fractions prepared from the tight aggregate stage (10 h) onward are active in cellulose synthesis [162], The product made from UDP[ C]glucose was shown to be cellulose by its solubility properties, periodate oxidation and methylation analysis pattern. Cellulose can also be made in monolayer cultures by cells induced with cAMP and DIF, a potent inducer of stalk cell properties specific genes [2-4,163]. 

P. Mischnick, M. Lange, M. Gohdes, A. Stein, and K. Petzold, Trialkylsilyl derivatives of eyelomaltoheptaose, cellulose, and amylose Rearrangement during methylation analysis, Carbohydr. Res., Ill (1995) 179-187. 

M. Gohdes, P. Mischnick, and W. Wagenknecht, Methylation analysis of cellulose sulphates, Carbohydr. Polym., 33 (1997) 163-168. 

Mischnik P, Lange M., Gohdes M., Stein A., Petzold K., Trialkylsilyl derivatives of cyclomaltoheptaose, cellulose, tmd amylose Rearrangement during methylation analysis, Carbohyd. Res., 277, 1995, 179—187. 

It provides a direct structural characterization of the in vitro product, as opposed to biochemical techniques that rely on the use of radioactive substrate and a subsequent hydrolysis of the polysaccharides with specific hydrolases. In the case of P-glucans, Hquid C-NMR analysis allows distinction between (1—>3) and (1 4) linkages for products that are soluble in DMSO. For high molecular weight polymers that are insoluble in solvents commonly used for liquid C-NMR analysis, such as cellulose, solid-state NMR spectroscopy can be used for structural characterization. In addition, solid-state NMR spectroscopy provides information on the conformation of the glucan chains in a given preparation as well as structural details that cannot be obtained with Hquid NMR spectroscopy and methylation analysis. For instance, in the case of cellulose, solid-state NMR spectroscopy allows the determination of the proportions of the I and Ip allomorphs in the sample (Atalla and VanderHart 1984). 

Figure 8-4. Methylation analysis of in vitro P-D-glucans. (a) Gas chromatography of the permethyl-ated alditol acetate obtained from methylation analysis of the cellulose synthesized in vitro by the enzyme from blackberry. Peak 1, derivative characteristic of (1 4) linked glucosyl units. Peak 2, internal standard (mj o-inositol). The derivative characteristic of (1 3) linked glucosyl units usually elutes 1 min before the major derivative visible in the chromatogram (not shown see Bulone et al. 1995). (b) Structural characterization by electron impact mass spectrometry of the 1,4,5-tri-0-acetyl-2,3,6-tri-0-methyl-D-glucitol derivative corresponding to peak 1 in A and characteristic of (1 4) linked glucosyl units.

Methylation analysis and n.m.r. spectroscopy have indicated that a gelforming jS-D-glucan from Pleurotus ostreatus consists of a (1 -> 3)-linked chain, to which side-chains of cx-(l 4)-D-gIucosyl residues are attached. A multiple-strand helix is considered to be the most likely conformation of this -D-glucan. Chemical analysis and studies of the ultrastructure of Pythium debaryanum have indicated that the cell wall is constructed of cellulosic microfibrils, which exist both as a framework and as a finer network.The microfibrils are covered by matrix material composed of a mixture of amorphous (1 -> 3)- and (1 -> 6)-linked, branched jS-o-glucans. 

Cellulose is insoluble in most solvents. It can be dissolved in solutions of zinc chloride [53] or by treating with Cadoxen, a solution of 5% (w/v) of cadmium oxide in 28% (v/v) of ethylenediamine in water [54-56a]. It can be dissolved in Hakamori Reagent for methylation analysis [56b]. 

C. Schwarzinger, I. Tanczos and H. Schmidt, Pyrolysis gas chromatography/mass spectrometry and thermally assisted hydrolysis and methylation (THM) analysis of various cellulose esters, J. Anal. Appl. Pyrol., 58 59, 513 523 (2001). 

Haworth methylation of methyl /3-D-glucopyranoside and its 4-benzyl and 4-(tetrahydropyran-2-yl) ethers was investigated in connection with partial-methylation studies on cellulose.267 For the unsubstituted glycoside, the ratios of relative rate-constants k2 k3 k4 k were estimated to be 8 2 1 8, and, for the 4-ethers, it was found that ke> k2> k3 best agreements between calculated and experimental yields were found with the assumption that the rate constant for reaction at HO-3 is doubled when HO-2 is substituted. Later methylation studies,268 performed to low degrees of substitution, with analysis by gas-liquid chromatography, gave k2> k4> k3 for the reactivity... 

Carrington et al. [1.124] usd thermomechanical analysis (TMA) to study the ice-crystallization temperature of 30 % (w/w) fructose, sucrose and glucose with and without sodium carboxy methyl cellulose (CMC). TMA has been used to measure the expansion of... 

The particular array of chemical shifts found for the nuclei of a given polymer depends, of course, on such factors as bond orientation, substituent effects, the nature of nearby functional groups, solvation influences, etc. As a specific example, derivatives of the carbohydrate hydroxyl moieties may give rise to chemical shifts widely different from those of the unmodified compound, a fact that has been utilized, e.g., in studies (l ) on commercially-important ethers of cellulose. Hence, as illustrated in Fig, 2, the introduction of an 0-methyl function causes (lU,15) a large downfield displacement for the substituted carbon. This change allows for a convenient, direct, analysis of the distribution of ether groups in the polymer. Analogously, carboxymethyl, hydroxyethyl and other derivatives may be characterized as well... 

Lipids can be identified and quantified using thin-layer chromatography (TEC) and gas chromatography (GC) (Galliard, 1968). Extraction of lipids is achieved by homogenizing potato tubers with isopropanol in a blender, followed by a series of filtrations and extractions with chloroform-methanol (2 1). Chloroform is removed by rotary evaporation and the residue is redissolved in benzene-ethanol (4 1). This extract is passed through a DEAE-cellulose column, and the fractions collected are subjected to TEC on 250 p,m layers of silica gel G, using three solvent systems. Fatty acid methyl esters for GC analysis are prepared by transmethylation of the parent lipids, or by diazomethane treatment of the free fatty acids released by acid... 

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