Solid state H-1 NMR studies of cell wall materials of potatoes

Cell wall materials from potatoes (Solanum tuberosum) prepared by two diffe rent methods have been studied using NMR proton relaxation times. Spin latt ice relaxation in both the rotating and laboratory frames as well as transv erse relaxation have been measured over a range of temperatures and hydrati on levels. It was observed that the sample prepared using a DMSO extraction showed anomalous behaviour of spin lattice relaxation in the laboratory fr ame probably due to residual solvent in the sample. Spin lattice relaxation in the laboratory frame is the result of hydroxymethyl rotation and anothe r unidentified high frequency motion. In the rotating frame relaxation is a dequately explained by hydroxymethyl rotation alone. In neither experiment is methyl group rotation observed, calculation suggests that this is due to the low density of methyl groups in the sample. Non-freezing water in pota to cell walls, a-cellulose and pectin was found about 0.2, 0.04 and 0.18 g per gram dry matter, indicating preferable hydration of pectin compared to cellulose. The effects of hydration are most noticeable in the measurements that reflect low frequency motions, particularly transverse relaxation, wh ere both second moments and the relative intensity of signals arising from immobile material are reduced by hydration. (C) 1999 Elsevier Science B.V. All rights reserved.