Glucans analysis

Several factors are critical for the accuracy and reproducibility of (3-glucan determination. As with any other analysis, some of these factors relate to the skills of the analyst. Parameters critical for (3-glucan analysis include the following discussed below sample homogeneity, particle size, enzyme purity, glucose standard, pipetting technique, and absorbance measurement. 

A new method of D-glucan analysis involves reductive cleavage of permethylated compounds with triethylsilane and trimethylsilyl triflate or boron trifluoride-etherate as catalyst, followed by acetylation, which yields a series of acetylated, methylated 1,5-anhydro-glucitols. A number of isomeric substituted 1,5-anhydro-glucitols were synthesized as references. /3-Glycosyl-... 

Leemhuis, H., Pijning, T., Dobruchowska, J.M., et al. (2013) Glucansucrases Three-dimensional structures, reactions, mechanism, a-glucan analysis and their implications in biotechnology and food applications. J Biotechnol 163, 250-272. 

Fractionation of a suspected to be nb/lcb glucan sample for detailed analysis... 

Analysis of nb/lcb glucan fractions obtained from a preparative S-200/S-1000 system... 

FIGURE 16.12 Enzymatically synthesized amylose"-type nb/lcb glucans ( ) with a significant amount of the substrate glucose-1-PO4 separated on Sephacryl S-SOO/S-IOOO (60 + 9S x 1.6 cm) 3-ml fractions were collected for further analysis normalized (area = 1.0) eluogram profiles (ev) constructed from an off-line determined mass of carbohydrates for each of the pooled fractions flow rate 0.42 ml/ min V,xd = 126 ml, V , = 273 ml eluent O.OOS M NaOH. 

Analysis of the products which become water-soluble after extrusioncooking showed that feroylated heteroxylans and glucans were solubilised from wheat bran (10), arabinans, heteroxyalans and pectins from pea hulls (11,12), and pectins from the other sources (13,14). 

Cellulase-Negative Xylanase-Positive Mutants. There are two reports concerning the selection of such mutants from filamentous fungi, one on Pofyporus adm-tus (32) and the other cmi Trichoderma reesei (Durand, H. et al. Society CAYLA, Toulouse, France, unpublished results). An analysis of the eliminated cellulase genes has not been done, so it is not known if the mutants negative in endo(l- 4)-p-glucan-ase were deficient also in cellobiohydrolases. 

Our original approach to polysaccharide C-13 n.m.r. spectral analysis consisted of making a minimum number of hypotheses about expected structure-to-spectra relationships (8). By then comparing spectra to known structure for a series of D-glucans, we attempted to establish the validity of these hypotheses and to establish how diverse a structural difference could be accommodated The hypotheses were as follows. Firstly, that each polymer could be considered as an assembly of independent saccharide monomers. Secondly, that these hypothetical saccharide monomers would be 0 alkylated (0 -methylated) in the same positions as the actual saccharide linked residues (it had previously been established that 0-methylation of any a-D-glucopyranosyl carbon atom position resulted in a down-field displacement of vlO p.p.m. for the associated resonance). Thirdly, that each differently substituted residue would have a completely different set of chemical shift values for each carbon atom position (different from the unsubstituted saccharide) but that only the carbon atom positions involved in inter-saccharide linkages would have A6 greater that 1 p.p.m. And, fourthly, that the hypothetical 0-alkylated residues would contribute resonances to the total spectrum proportional to their mole ratio in the polymers. 

Figure 3 shows the structure of the hemicellulosic polysaccharides obtained from the bran cell wall preparations. These structures were deduced from the results of the methylation analysis of purified fractions (13). In contrast to the endosperm cell wall, no / -l,3-,l,4-glucan was obtained from... 

N 141 "Conformational Analysis of Polysaccharides. Part IV. Long-range Contacts in Some p-Glucans by Model Building in the Computer and the Influence of... 

In an earlier article1 on the application of enzymic techniques to the analysis of the structure of polysaccharides, the -d- and /3-D-glucans were discussed, as well as more-general aspects of the preparation and use of catabolic enzymes in such analyses. The present article describes enzymic contributions to knowledge of the structures of other polysaccharides, but an account of subsequent research on a- and jS-D-glucans is also included. 

The observation47 that the stability of the secondary-ordered structure of xanthan (and as a consequence, its susceptibility to hydrolysis by cellulase) is a function of temperature, pH, and ionic strength has allowed the application of enzymic techniques to structural analysis. Xanthan is hydrolyzed in salt-free, aqueous solutions at elevated temperatures that is, hydrolysis occurs if the chain is unordered. It was proposed that, at lower temperatures and in the presence of salt, the small side-chains organize around the (1 ->4)-/3-D-glucan backbone and protect it from hydrolysis. 

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