Molecular characteristics of amylose and starch in dimethyl sulfoxide.

The aim of this work was the molecular characterization of starch polysaccharides to determine solution structure. Studies of amylose and potato starches of different origins were carried out by the static light scattering, dynamic light scattering, and HPSEC-MALLS methods. Molecular parameters such as Mw, Rg, A2, molar mass distribution, Dz, Rh, the structure-dependent rho-parameter, and osmotic modulus for amylose were determined. The Mw of amylose was found to be in the range from 1 x 10(5) to 1 x 10(6) g mol-1. The Mw of potato starches was much higher, that is, in the range of 23-37 x 10(6) g mol-1. The Rg of the amylose samples was in the range of 24-71 nm, and that of the potato starches was between 130 and 150 nm. The intensity-time correlation function showed one diffusive relaxation motion for amylose as well as for starch. The diffusion coefficients of the amylose prepared from starch by several methods were in the range of 2.7-9.1 x 10(-8) cm2 s-1, and those of the starches were 1 magnitude lower between 4.8 and 6.7 x 10(-9) cm2 s-1. The rho-parameter of amylose was calculated as having values between 1.5 and 2.2, and that of starches was calculated to be an average value of 0.62. The assumed solution behavior of amylose in dimethyl sulfoxide corresponds to that of a flexible chain, while the behavior of starch more closely resembles that of a spherelike structure.

Structure of the enzymatically synthesized fructan inulin.

Construction, purification and characterization of a fusion protein of maltose-binding protein of Escherichia coli and the fructosyltransferase of Streptococcus mutans is described. With the purified protein, in vitro synthesis of inulin was performed. The obtained polysaccharide was characterized by high-performance size-exclusion chromatography (HPSEC) and static light scattering (SLS) in dilute aqueous and dimethyl sulfoxide solution. For all samples very high molecular weights between 60 x 10(6) and 90 x 10(6) g/mol and a remarkable small polydispersity index of 1.1 have been determined. Small root-mean-square radii of gyration point to a compact conformation in dilute solution. No difference between native and enzymatically synthesized inulin was observed by X-ray powder diffraction and thermoanalysis of solid samples.