Molecular weight and chain conformation of amylopectin from rice starch |
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Authors: | Zhaocheng Ma Siming Zhao Ke Cheng Xufeng Zhang Xiaojuan Xu Lina Zhang |
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Affiliation: | 1. Department of Chemistry, Wuhan University, Wuhan 430072, China;2. Food Science and Technology Department, Hua Zhong Agricultural University, Wuhan 430072, China |
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Abstract: | By using laser light scattering (LS) and size exclusion chromatography combined LS, we have investigated the molecular weight and chain conformation of amylopectin from rice of India (II‐b), japonica (IJ‐b), and glutinous (IG‐b) in dimethyl sulfoxide (DMSO) solution. The weight‐average molecular weight (Mw) and radius of gyration (〈S2〉½) of amylopectin were determined to be 4.06 × 107 and 128.5 nm for India rice, 7.41 × 107 and 169.6 nm for japonica rice, 2.72 × 108 and 252.3 nm for glutinous rice, respectively. The 〈S2〉½ values were much lower than that of normal polymers, indicating a small molecular volume of amylopectin, as a result of highly branched structure. Ignoring the difference of degree of branching, approximated dependences of 〈S2〉½ and intrinsic viscosity ([η]) on Mw for amylopectin in DMSO at 25°C were estimated to be 〈S2〉½ = 0.30Mw0.35 (nm) and [η] = 0.331Mw0.41 (mL g?1) in the Mw range studied. Moreover, from the 〈S2〉½ values of numberless fractions obtained from many experimental points in the SEC chromatogram detected with LS, the dependence of 〈S2〉½ on Mw for the II‐b sample was estimated also to be 〈S2〉½ = 0.34 Mw0.347, coinciding with the above results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 |
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Keywords: | amylopectin conformation light scattering molecular weight SEC |
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