Structural and molecular properties of dialdehyde starch

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• 作者：Maciej Fiedorowicz and Andrzej Para
• 关键词：Dialdehyde starch ; Size exclusion chromatography ; Molecular weight
• 刊名：Carbohydrate Polymers
• 出版年：2006
• 出版时间：3 March 2006
• 年：2006
• 卷：63
• 期：3
• 页码：360-366
• 全文大小：354 K

文摘

Dialdehyde starch (DAS) of degree of oxidation (DO) of 1.5 % (DAS1-5), 5 % (DAS5), 15 % (DAS15) and 25 % (DAS25) was prepared from potato starch in the periodate oxidation reaction with electrochemical recovery of the oxidant. Molecular weights (M_w) and radii of gyration (R_g) of polysaccharide chains of native and oxidized starches were measured by means of a high-performance size exclusion chromatography coupled with multiangle laser light scattering and refractive index detectors. The weight average molecular weight (M_w) and radius of gyration (R_g), calculated for the whole complicated peak of the eluate of native starch were 30.0×10⁶ and 119.6 nm, respectively. The oxidation induced instant degradation of starch polysaccharide chains.

M_w value of the chains of the polysaccharide molecules eluted from the sample of DO 1.5 % (DAS1-5, 2.2×10⁶) was by one order lower than the average molecular weight of native starch molecules (30×10⁶). Even more significant decrease in molecular weight up to 6.4×10⁴ was observed for the DAS5 sample. The chain length distribution of amylopectin structural units of native and DAS was characterized by the hydrolysis with isoamylase followed by treatment with β-amylase. Chain distribution profiles of completely debranched samples were available from a high-pressure size exclusion chromatography with multiangle laser light scattering and refractometric index detectors. The oxidation slightly changed the average molecular weight (M_w) of the A-type chains although it evoked changes in the mass ratio of the A-type chains. The weight average molecular weight M_w and mass ratio of B-type chains significantly differed depending on DO of the sample. X-ray diffraction patterns indicated that crystallinity of DAS1-5 and DAS5 decreased in relation to native starch. Oxidised starches of the highest DO were fully amorphous.