Deacetylation poly

Chitin and the deacetylated form, chitosan, are attractive linear amino polysaccharides found in the shell of crustaceans. These abundant biopolymers, composed mainly of poly(/T(l,4)-2-acetamido/2-amino-2-deoxy-D-glucopyranose)... 

Kirsh et al. 42) prepared apolar derivatives of poly(4-vinylpyridine) by benzylation. With nitrophenyl acetate as the substrate the benzylated catalyst is 100 times more effective than 4-ethylpyridine. A double-displacement mechanism was observed. The rate constants for deacylation of the acylpoly(vinylpyridine) derivatives were about 4 x 10" /sec. The comparable value for a-chymotrypsin is 8 x 10 /sec. The factor of 20 seems small, but it should be kept in mind that deacetylation of a-chymotrypsin is very slow compared with the deacylation reactions involving the natural substrates of the enzyme. 

Ronkvist M, Lu W, Feder D, Gross R (2009) Cutmase-catalyzed deacetylation of poly(vmyl acetate). Macromolecules 42 6086-6097... 

Another interesting organic material usually used to immobilize enzymes is chitosan [95, 96]. Chitosan is a poly((1 4)-2-amino-2-deoxy-P-D-glucose) (Fig. 9.5), which is a product of deacetylation of chitin, the second polysaccharide ranked by its prevalence in nature, just after cellulose. 

The stabilities are in the order fluoride > chloride > bromide > iodide. The fluorides are extremely stable, and may even be deacetylated without loss of fluorine, to give the corresponding glycosyl fluorides. The iodides, on the other hand, are unstable compounds which, even in favorable cases, decompose at room temperature within two weeks. The bromides show a reasonable balance between reactivity and instability, and have been by far the most widely used halides for synthetic work. Of recent years, the use of poly-O-feenzoylglycosyl bromides has become increasingly popular in studies in this group they are more stable than the acetates but more reactive than poly-O-acetylglycosyl chlorides. 

Amino-2-deoxy-(l,4)-P-D-glucopyranan deacetylated chitin deacetylchitin P-l,4-poly-D-glucosamine poly-D-glucosamine poly-(l,4-P-D-glucopyranosamine). 

Heux et al. (2000) found that after partial deacetylation (<50%), the product of chitin becomes soluble in acidified water. Therefore, chitosan is characterized by its DA, which is the average mole fraction/percentage of A-acetyl-D-glucosaminc units within the macromolecular chain (Desbrieres, 2002). Alternatively, Heux et al. (2000) calculated DA by measuring all carbonyl or methyl groups divided by the integral of all the carbon atoms in the backbones. The DD may be determined by a titration method in which chitosan is dissolved in 0.1% acetic acid to form a 0.01% solution. This is followed by titration with 0.0025 N poly (vinyl sulfate) potassium salt (PVSK) with 1% toluidine blue (TBO) as an indicator. The acetyl content of... 

Kurita, K., Tomita, K., Ishii, S., Nishimura, S., and Shimoda, K. 1993. Squid chitin A potential alternative chitin source Deacetylation behaviour and characteristics properties. J. Poly. Sci. Part A Poly. Chem. 31, 485-491. 

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