Effects of carboxylation of the side chains on the order-disorder transition in aqueous solution of schizophyllan, a triple helical polysaccharide

Autor: Hiroyuki Oku, Takahiro Sato, Satoka Okamoto, Toshiaki Dobashi, Kazuto Yoshiba, Bjørn E. Christensen
Rok vydání: 2017
Předmět:
Zdroj: Carbohydrate Polymers
ISSN: 0144-8617
Popis: Schizophyllan and scleroglucan are water-soluble polysaccharides having repeating units consisting of three β-1,3-linked glucose residues in the main chain and a single β-1,6-linked glucose residue as the side chain. This polysaccharide dissolves as a triple helix in an aqueous solution and shows a cooperative order-disorder transition between the side chain and solvent molecules while retaining the triple helical conformation. Periodate and subsequent chlorite oxidations selectively modify the side chain glucose to provide the corresponding dicarboxylate units. Optical rotation measurements and differential scanning calorimetry were performed on carboxylated schizophyllan/scleroglucan (‘sclerox’) samples to investigate the effects of the degree of carboxylation on the order-disorder transition in deuterium oxide with 0.1 M NaCl. The transition curves for the sclerox samples are strongly dependent on the degree of carboxylation. The modified side chains cannot take the ordered structure, resulting in a reduction of the transition enthalpy. The transition temperature for carboxylated schizophyllan becomes lowered and the transition curve broadens with increasing the degree of carboxylation. The permanent disordered units are included in a trimer by the carboxylation to inhibit a long sequence of the ordered units. © 2017. This is the authors’ accepted and refereed manuscript to the article. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Databáze: OpenAIRE
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