Poly a-glucoses

Some antigens, such as type 3 pneumococcal polysaccharide, EPS and other polymeric substances such as dextrans (poly-D-glucose) and levan (poly-D-fructose) can induce antibody synthesis without the assistance of TH cells. These are known as T-independent (Ti) antigens. Only one class of immunoglobulin (IgM) is synthesized and there is a weak memory response. 

With the development of enzymatic polymerization in solution, also first accounts for SIP appeared. Loos et al. [350] reported on enzymatic surface polymerization of glucose-l-phosphate with potato phosphorylase as the catalyst resulting in oligo- or poly-(a,l- 4)-D-glucopyranose. As initiator sites, immobilized malto-heptaose was used. Enzymatic grafting of hexyloxyphenol onto chitosan is reported by Payne and coworkers [351]. 

An early example of an MIP-QCM sensor was a glucose monitoring system by Malitesta et al. (1999). A glucose imprinted poly(o-phenylenediamine) polymer was electrosynthesized on the sensor surface. This QCM sensor showed selectivity for glucose over other compounds such as ascorbic acid, paracetamol, cysteine, and fructose at physiologically relevant millimolar concentrations. A unique QCM sensor for detection of yeast was reported by Dickert and coworkers (Dickert et al. 2001 Dickert and Hayden 2002). Yeast cells were imprinted in a sol-gel matrix on the surface of the transducer. The MIP-coated sensor was able to measure yeast cell concentrations in situ and in complex media. A QCM sensor coated with a thin permeable MIP film was developed for the determination of L-menthol in the liquid phase (Percival et al. 2001). The MIP-QCM sensor displayed good selectivity and good sensitivity with a detection limit of 200 ppb (Fig. 15.7). The sensor also displayed excellent enantioselectivity and was able to easily differentiate the l- and D-enantiomers of menthol. 

Dextrans are bacterial and yeast polysaccharides made up of (a 1—>6)-linked poly-D-glucose all have (al—>3) branches, and some also have (al—>2) or (al—>4) branches. Dental plaque, formed by bacteria growing on the surface of teeth, is rich in dextrans. Synthetic dextrans are used in several commercial products (for example, Sephadex) that serve in the fractionation of proteins by size-exclusion chromatography (see Fig. 3-18b). The dextrans in these products are chemically cross-linked to form insoluble materials of various porosities, admitting macromolecules of various sizes. 

Kitano, S., Koyama, Y., Kataoka, K., et al. A novel drug delivery system utilizing a glucose responsive polymer complex between poly (vinyl alcohol) and poly( V-vinyl-2-pyrrolidone) with a phenylboronic acid moiety. J. Contr. Rel. 19 161—170, 1992. 

Starch (Figure 12.20) is a polymer of glucose that we can digest. Starch is poly [l<->4] a-glucose. The glycoside bonds in starch are alpha. This configuration puts a bend in the chain. In fact, starch adopts a helical conformation. 

Penidllium luteum Zukal. A neutral polysaccharide, luteose, is produced by the mild alkaline hydrolysis of the malonyl residues from luteic acid, a metabolic product of this mould. Luteose was shown to be a poly-D-glucose in which the hexose units were joined by /3-1,6-glycosidic... 

Structurally, the O-polysaccharide chains of H. pylori clinical isolates have a poly-A-acetyl-lactosamine (-LacNAc) chain decorated with multiple lateral a-L-fucose residues forming internal Lex determinants with terminal Lex or Ley units (Fig. 10.4) or, in some strains with additional, D-glucose or D-galactose residues (Moran 2001 a,b, 2008 Monteiro, 2001). Moreover, Lea, Leb, sialyl-Lex, and H-1 antigens have been structurally described in other strains, as well as the related blood groups A and B (Fig. 10.4), but occur in association with Lex and LacNAc chains (Monteiro et al., 2000a,b Heneghan et al., 2000). 

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... 

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