A C-13 CP MAS NMR spectroscopy and AFM study of the structure of Glucagel (TM), a gelling beta-glucan from barley

The structure of Glucagel(TM), a mixed-linked (1 --> 3), (1 --> 4)-beta-D-g lucan extracted from barley, was examined using C-13 CP/MAS NMR spectroscop y and atomic force microscopy (AFM). Results from C-13 CP/MAS NMR spectrosc opy showed that Glucagel(TM) contained regions with two distinct conformati ons. In some of the regions the beta-glucan chains associated to form a uni que conformation, the A-conformation, while in the other regions the beta-g lucan chains were in an amorphous conformation. Dilute solutions of Glucage l(TM) were prepared for imaging by dissolving Glucagel(TM) in water at 90 d egrees C. If the dilute solution was immediately deposited onto mica and th e surface dried, then no fine detail was seen in the AFM image. However, wh en dilute solutions of Glucagel(TM) were left for several days before being deposited onto the mica surface, individual fibres could be clearly imaged . These results suggested that in gels formed from Glucagel(TM), junction z ones occur because of the interaction of two beta-glucan chains in the A-co nformation. (C) 1999 Elsevier Science Ltd. All rights reserved.