Glucose from dextran

The selective separation range of the S-500/S 1000-system for glucans is shown for hybrid starch Triticale T22. This mixture of scb and nb/lcb glucans contains components in the range between approximately dp 50-300,000 glucose monomers (Fig. 16.11). The degree of polymerization distribution obtained from dextran-based calibration was computed as well in terms of... 

FIGURE 16.13 Degree of polymerization distribution (m dpD d) for synthesized amylose -type nb/lcb glucans calculated from dextran-calibrated — amylose-converted calibration of S-SOO/S-IOOO dp. = SSI [glucose units]. 

Figure 11.5 Left Steady-state fluorescence from Dextran-SWNT versus Con A concentration. Picture 1 shows no visible nanotube aggregates before Con A is added, while a large nanotube aggregate is clearly visible in picture 2 (taken after 15 lM Con A). Right Steady-state fluorescence of the sensor plotted versus glucose concentration. Picture 3 inset was taken after 20 mM glucose was added and clearly shows no visible aggregation. Adapted with permission from Ref. 29.

The initial overall reaction rate (sucrose consumption rate) decreases considerably with higher initial glucose concentration (Fig. 2), whereas the isomaltose formation rate increases up to 300 g L 1 glucose, which reflects the shift from dextran formation (substrate reaction) to the acceptor reaction (Fig. 3). However, with increasing glucose concentration, the maximal reaction rate shifts towards higher initial sucrose concentrations. However sucrose concentrations >0.5 M inhibit the reaction (Fig. 3). 

Some other bacteria, e.g., Leuconostoc mesenteraides, make 1,6-linked poly-o-glucose or dextrans. These always contain some a-l,3-linked branches and may also have a-1,4 and a-1,2 linkages, the structures varying from species to species. Dextrans formed by bacteria such as Streptococcus mutans growing on the surfaces of teeth are an important component of dental plaque. Bacterial... 

In the carbohydrate field it has been found possible to separate mixtures of oligosaccharides differing in size by only one glucose unit. Dextrans of low molecular weight have been separated by gel filtration." Partial resolution of a number of starch dextrins on Sephadex columns has been reported." Thus amylodextrin can be separuled completely from amylose. The method is particularly useful for polysaccharides because they show only small differences in their properties and usually differ only in maleuiilur size. 

D-galactose and L-rhamnose. Evidence for the presence of isomaltose residues in SXVIII accrued also from cross-reactions of various polysaccharides in anti-Pn XVIII. Polysaccharides which contained o-d-(1—>6)-linked D-glucose residues (dextrans, glycogen, -amylase limit dextrin) precipitated horse anti-Pn XVIII and, in general, the degree of reaction was related to the proportion of this linkage in the structure. 

A dextran-dextranase system has been used to examine the synergistic effect of exo- and cndo-enzymes acting jointly on polymeric substrates. An endo-dextranase (from Penicillium funiculosum) and an cxo-dextranase (from Streptococcus mitis) produced D-glucose more rapidly from dextrans than the summed effects of the individual enzymes. 

Figure 3.19 El mass spectra of (a) peracetylated mannitol (mol wt = 434), (b) glycerol-tris-TMS (mol wt = 308), (c) 2-hydroxyethyl glucose-pentakis-TMS (mol wt = 584), and (d) partially methylated alditol acetate of 1,4-linked 2-hydroxyethylated glucose (mol wt = 394). (e) El mass spectrum of partially methylated alditol acetate of l,6-linked glucose (mol wt = 350) derived from dextran.

Briefly summarized, S-1000 shows better resolution in the high dp range, whereas the CL 2B system resolves low dp components better. Due to these differences in separation performance, the degree of polymerization distribution and degree of polymerization average values for the same sample obtained from broad scb— nb/lcb-transformed dextran calibration yielded dp = 29,900 glucose units for the S-1000 system and dp = 21,100 glucose units for the CL 2B system (Fig. 16.18). 

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