NMR local range investigations in amorphous starchy substrates: II-Dynamical heterogeneity probed by H-1/C-13 magnetization transfer and 2D WISE solid state NMR

In the preceding paper, we have investigated the structural heterogeneous c haracter of a series of amorphous samples prepared from various starchy sub strates (native potato starch, amylopectin and amylose) following different techniques of preparation (casting, freeze drying and solvent exchange). S pectral decompositions of the C1 resonances of the C-13 CP-MAS (Cross Polar ization and Magic Angle Spinning) spectra under H-1 decoupling have shown t he existence of five main types of alpha (1-4) link-ages. In this part, 2D solid state NMR WISE experiments and the C-13/H-1 magnetization transfer in CP as a local probe for both structures and dynamics were used. The C-13 C P magnetization curves versus contact time of each C1 component in each rec orded spectrum were fitted with an analytic function taking into account tw o H-1 reservoirs. Interpretation of the characteristic times derived from f itting yields some improvements on the knowledge of the heterogeneity of th e samples and on the water Molecules distribution. (C) 2001 Elsevier Scienc e B.V. All rights reserved.