Polymerization amylose

The glycogen phosphorolysis of phosphorylase can be reverted, which makes it possible to enzymatically polymerize amylose as well as hybrid structures with amylose as outlined in the following section. 

The fact that glycogen phosphorylase can be used to polymerize amylose was first demonstrated by Schaffner and Specht [110] in 1938 using yeast phosphorylase. Shortly after, the same behavior was also observed for other phosphorylases from yeast by Kiessling [111, 112], muscles by Cori et al. [113], pea seeds [114] and potatoes by Hanes [115], and preparations from liver by Ostern and Holmes [116], Cori et al. [117] and Ostern et al. [118]. These results opened up the field of enzymatic polymerizations of amylose using glucose-1-phosphate as monomer, and can be considered the first experiments ever to synthesize biological macromolecules in vitro. 

Various linear block copolymers of the AB, ABA and ABC type with enzymatically polymerized amylose blocks were reported. Ziegast and Pfannemuller converted the hydroxyl end groups of poly(ethylene oxide) into amino groups via tosylation and further reaction with 2-aminoalkylthiolate. To the resulting mono- and di-amino functionalized poly(ethylene oxide) maltooligosaccharide lactones were attached and subsequently elongated to amylose via enzymatic polymerization. Pfannemuller et al. performed a very detailed study on the solution properties of the synthesized A-B-A triblock... 

The results reviewed above clearly show that the combination of enzymatically polymerized amylose with surfaces of inorganic materials and... 

Kadokawa J, Kaneko Y, Nagase S, Takahashi T, Tagaya H (2(X)2) Vine-twining polymerization amylose twines around polyethers to form amylose-polyether inclusion complexes. Chem Eur J 8 3321-3326... 

Cellulose and amylose are comprised of the same glucose subunits as the cyclodexttins. In the case of cellulose, the glucose units are attached through 1,4-P-linkages resulting ia a linear polymer. In the case of amylose, the 1,4-a-linkages, as are found ia the cyclodexttins, are thought to confer heUcity to the polymeric chain. 

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 16.19 Degree of polymerization distribution (m dpD d) of wild-type potatoe starch ( ), a nb/lcb fraction ( amylose -type A)- s b fraction ( amylopectin"-type ) of the native starch ... 

An interesting procedure has been proposed for the synthesis of amylose-b-PS block copolymers through the combination of anionic and enzymatic polymerization [131]. PS end-functionalized with primary amine or dimethylsilyl, -SiMe2H groups were prepared by anionic polymerization techniques, as shown in Scheme 56. The PS chains represented by the curved lines in Scheme 56 were further functionalized with maltoheptaose oligomer either through reductive amination (Scheme 57) or hydrosilyla-tion reactions (Scheme 58). In the first case sodium cyanoborohydride was used to couple the saccharide moiety with the PS primary amine group. 

For the hydrosilylation reaction various rhodium, platinum, and cobalt catalysts were employed. For the further chain extension the OH-functionalities were deprotected by KCN in methanol. The final step involved the enzymatic polymerization from the maltoheptaose-modified polystyrene using a-D-glucose-l-phosphalc dipotassium salt dihydrate in a citrate buffer (pH = 6.2) and potato phosphorylase (Scheme 59). The characterization of the block copolymers was problematic in the case of high amylose contents, due to the insolubility of the copolymers in THF. 

The effect of chain length on the ability of degraded amylose to form complexes was studied by Whistler and associates.63 When amylose is hydrolyzed to a degree of polymerization of 20 to 40, it no longer forms insoluble complexes with nitrobenzene, n-pentyl acetate and 2-heptanone, although it still does with 1-butanol and 2-nitropropane. 

Fraction 1 (number) Yield in percent of amylose Reducing value as percent glucose Average molecular weights Average degrees of polymerization... 

Enzymatic Polymerization of Amylose with Glycogen Phosphorylase... 

Recently Kuriki and coworkers succeeded in producing glucose-1-phosphate in situ during the enzymatic polymerization of amylose. By using sucrose phosphorylase or cellobiose phosphorylase, the monomer was produced during the polymerization from inorganic phosphate and sucrose or cellobiose, respectively [119-121]. 

The first surface-initiated enzymatic polymerization reported was the synthesis of amylose brushes on planar and spherical surfaces [145]. For this, silica or silicone surfaces were modified with self-assembled monolayers of (3 amino-propyl)trimethoxysilane or chlorodimethylsilane, respectively. To these functionalities, oligosaccharides were added via (a) reductive amidation of the oligosaccharides to surface-bound amines, (b) conversion of the oiigosaccharide to the according aldonic acid lactone and reaction with surface bound amines, and (c) incorporation... 

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