Iodine binding to explore the conformational state of internal chains of amylopectin

• Published in: Carbohydrate polymers Vol. 98; no. 1; pp. 778 - 783
• Main Authors: Shen, Xinyu, Bertoft, Eric, Zhang, Genyi, Hamaker, Bruce R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.10.2013; Elsevier
• Subjects: Amylopectin; Amylopectin - chemistry; Amylose - chemistry; Applied sciences; Carbohydrate Conformation; Exact sciences and technology; Internal chains; Iodine; Iodine - chemistry; Natural polymers; Physicochemistry of polymers; Starch and polysaccharides; Waxes - chemistry; Zea mays - chemistry; β-Amylolysis; Internal chains; Amylopectin; β-Amylolysis; Iodine; Enzyme; Experimental study; Corn starch; Glycosylases; β-Amylase; Glycosidases; Enzymatic digestion; Hydrolases; Oside polymer; Kinetics; Chemical uptake; Aqueous dispersion; Conformation
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.06.050

•Iodine interacts with both external and internal amylopectin chains.•Internal amylopectin chains likely pre-exist in a helical form.•Internal helical structures possibly drive intermolecular interactions that might explain functional properties. Previous studies have found that the proportion of long chains of amylopectin correlates to its functional and nutritional properties. As a possible explanation of this correlation, the iodine binding property of amylopectin internal chains was investigated as an indirect evidence of their ability to form helices for intra- or inter-molecular interactions. Waxy and amylose-extender waxy corn starches were hydrolyzed by β-amylase for varying periods of time to incrementally remove the external chains, and the absorbance and the wavelength of maximum absorbance of iodine binding were examined. Experimental results suggest that iodine can bind with both external and internal chains; a significant amount of absorption comes from the latter, as stepwise removal of external chains only somewhat reduced absorption. Internal amylopectin chains, thus, were concluded to likely pre-exist in helical form, as opposed to a conformational change into helices facilitating iodine binding in the absence of external chains. Such internal chain helical structures possibly drive intermolecular interactions that would explain why amylopectin with high proportion of internal chains form harder gels, create pastes less prone to shear breakdown, and are more slowly digesting.