The hydrodynamic characterization of waxy maize amylopectin in 90% dimethyl sulfoxide–water by analytical ultracentrifugation, dynamic, and static light scattering

• Published in: Carbohydrate polymers Vol. 39; no. 4; pp. 315 - 320
• Main Authors: Millard, M.M, Wolf, W.J, Dintzis, F.R, Willett, J.L
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1999; Elsevier Science
• Subjects: amylopectin; Amylopectin waxy maize; Applied sciences; corn; Exact sciences and technology; Hydrodynamic characterization; hydrodynamic properties; hydrodynamics; molecular weight; Natural polymers; Physicochemistry of polymers; sedimentation; sedimentation coefficient; starch; Starch and polysaccharides; Static light scattering; ultracentrifugation; Static light scattering; Hydrodynamic characterization; Amylopectin waxy maize; Hydrodynamic radius; Amylopectin; Molecular weight determination; Light scattering; Corn; Radius of gyration; Experimental study; Sedimentation coefficient; Hydrodynamic properties; Translational diffusion; Methyl sulfoxide; Mixed solvent; Dynamical scattering; Concentration effect; Oside polymer; Aqueous solution
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/S0144-8617(99)00021-1

Static light scattering of high amylopectin waxy maize starch gently dispersed in 90% dimethyl sulfoxide–water yielded a weight average molecular weight M w and radius of gyration R g of 560×10 6 g/mol and 342 nm, respectively. To obtain an independent hydrodynamic characterization of these solutions, we measured the sedimentation coefficient for the main component in an analytical ultracentrifuge. The value of s 0, the infinite dilution sedimentation coefficient, was 199 S. The translational diffusion coefficient D 0 in very dilute solutions was measured by dynamic light scattering at 90° and found to be 2.33×10 −9 cm 2/s. An effective hydrodynamic radius R h was calculated from this diffusion constant using the Stokes–Einstein equation and found to be 348 nm. The structure-related parameter ρ= R g/ R h was calculated to be 0.98. The weight average molecular weight calculated from the Svedberg equation using the values measured for s 0 and D 0 was 593×10 6 g/mol. This result is in reasonable agreement with the light scattering results. As light scattering results are subject to experimental errors due to the possibility of dust contamination, the presence of microgel or aggregates, and the questionable applicability of light scattering theory to interpret results for macromolecular sizes approaching the wave length of light used as a source for scattering, it is advisable to have corroborating hydrodynamic data when possible to further validate light scattering results in this very high molecular weight range.