Cellobiose analysis

The torsion angles predicted by conformational analysis agree closely with those of crystalline cellobiose as measured by X-ray diffraction, the conformation of which is restricted by two chain-stabilising intramolecular hydrogen bonds between 0(3 )-H and 0(5) and also between 0(2 )-H and 0(6) (Figure 4.3). These are also found in cellulose and they assist in maintaining the highly extended conformation which allows it to function as a structural polymer. 

LO=25 Values below this are erroneous for MMP2(85), cellobiose PRINT "Energy analysis utility for MM2 output, SURFER input. PRINT "MAPREP V. 2.0 - March 2, 1989". PRINT PRINT... 

TGA analysis shows that polymer degradation starts at about 235°C which corresponds to the temperature of decomposition of the cellobiose monomer (m.p. 239°C with decom.). Torsion Braid analysis and differential scanning calorimetry measurements show that this polymer is very rigid and does not exhibit any transition in the range of -100 to +250 C, e.g. the polymer decomposition occurs below any transition temperature. This result is expected since both of the monomers, cellobiose and MDI, have rigid molecules and because cellobiose units of the polymer form intermolecular hydrogen bondings. Cellobiose polyurethanes based on aliphatic diisocyanates, e.g. HMDI, are expected to be more flexible. 

Mass Spectrometric Analysis of Volatiles during Photolysis. Samples investigated were cellulose triacetate, cellobiose octaacetate, glucose pentaacetate, cellobiose, and glucose. 

Cellobiose Octaacetate and Glucose Pentaacetate. The results on both compounds were similar. Samples irradiated at 253.7 and 313 mfi, both in the presence of oxygen and in vacuum, were saponified. Infrared analysis of the saponified residues showed that all samples had carbonyl absorption at 5.76 to 5.78 microns, owing to lactones, ketones,... 

Figure 7. Production of glucose and cellobiose from Avicel. The reaction mixture contained 1% Avicel PH-101, 1% Trichoderma reesei QM 9123 cellulose protein produced in a pH 3.6 culture medium, and 0.05M sodium acetate buffer, pH 5.0. Incubation conditions and analysis are...

Fig, 5. Conformation of cellobiose from X-ray crystal structure analysis as a space filling stereo plot. The reducing end is to the right... 

Cellobiose octaacetate and 1,6-Anhydro-p-cellobiose hexaacetate are compared with respect to their glycosidic conformation [93, 94], For cellobiose octaacetate it was concluded that the conformation in solution is close to that one determined by X-ray crystal structure analysis to cp = 45° and i / = 16° (Fig. 5) whereas the 1,6-anhydro derivative is demonstrated by use of NOEs, relaxation data, and coupling constants 3JC>H to adopt torsional angles of = 25° and ]c = 45° respectively. 

From the analysis of 13C NMR chemical shifts the / angle in chitobiose should exhibit a value of approximately 10° more positive than that of cellobiose and thus resulting in r = 0° [136],... 

B. Bernet and A. Vasella, Intra- and intermolecular H-bonds of alcohols in DMSO. H-NMR analysis of inter-residue H-bonds in selected oligosaccharides Cellobiose, lactose, N,N"-di-acetylchitobiose, maltose, sucrose, agarose, and hyaluronates, Help. Chim. Acta, 83 (2000) 2055-2071. 

The combined data provide a ready means by which to compare and select appropriate assays for application in cellulase-catalyzed cellulose saccharification experiments. Products in such experiments are expected to include glucose cellobiose and, potentially, some cellooligosaccharides. Optimum reducing sugar assays would have equivalent molar color yields for these soluble products. As shown in Table 3, this optimum situation only applies to the two copper-based assays (Nelson, BCA). Because of their importance with respect to the analysis of insoluble cellulose (discussed next), calibration curves reflecting the molar color yields for the DNS and BCA assays are presented in Fig. 1. 

FPU/CBU). (3-Glucosidase was added to avoid end-product inhibition owing to cellobiose accumulation. Batch hydrolysis experiments were conducted at 2% consistency of cellulose in 50 mM acetate buffer, pH 4.8, with 4 mg of tetracycline/100 mL of buffer as antibiotic. The hydrolysis incubation was performed at 45°C on a rotary shaker at 150 rpm. Samples of the supernatants were taken at assigned intervals for sugar analysis. All hydrolysis experiments were performed in duplicate, and the averages were reported. 

The crystalline structure of cellulose has been characterized by X-ray diffraction analysis and by methods based on the absorption of polarized infrared radiation. The unit cell of native cellulose (cellulose I) consists of four glucose residues (Figs. 3-6 and 3-7). In the chain direction (c), the repeating unit is a cellobiose residue (1.03 nm), and every glucose residue is accordingly displaced 180° with respect to its neighbors, giving cellulose a... 

---