Global conformation analysis of irradiated xyloglucans

Xyloglucan isolated and purified from tamarind seed was subjected to various degrees of gamma-irradiation treatments, from 10 to 70 kGy, monitored for radiation damage and then studied using a new combined hydrodynamic approach with regards to conformation and flexibility. Radiation products were analysed with regard to molecular weight (weight average) M-W from size exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLs), intrinsic viscosity [eta] and sedimentation coefficient S-20.w(o). Sedimentation coefficient distributions and elution profiles from SEC-MALLs confirmed the unimodal nature of the molecular weight distribution for each sample in solution. The chain flexibility was then investigated in terms of the persistence length, L-P of the equivalent worm-like chain model. The traditional Bushin-Bohdanecky (intrinsic viscosity) and Yamakawa-Fujii (sedimentation coefficient) relations were used separately then combined together by minimisation of a target function according to a recently published procedure [Ortega, A., & Garcia de la Torre, J. (2007). Equivalent radii and ratios of radii from solution properties as indicators of macromolecular conformation, shape, and flexibility. Biomacro-molecules, 8, 2464-2475 [see also Ortega, A. Metodologias computacionales para propiedades en disolucion de macromoleculas rigidas y flexibles. Ph.D. Dissertation, Universidad de Murcia, 2005]] and yielded an estimate for Lp in the range 4-9 nm using floated and fixed mass per unit length analysis protocols and point global analysis: irradiated xyloglucans behave as flexible structures in common with pressure/heat treated materials. (C) 2008 Elsevier Ltd. All rights reserved.