Preparation And Characterization Of Curdlan With Unique Single-Helical Conformation And Its Assembly With Congo Red

Elucidating the structure-activity relationship of curdlan is hampered by a lack of characterization with unique specific conformations (i.e., single- or triple-helix). In this study, single-helical curdlan is generated in dilute NaOH solutions at 35-50 ?C, and characterized with NMR, SAXS, and GPC. The conformational transition from coil to single-helix and the intramolecular hydrogen bond interaction are explored using NMR. It is found that the two aforementioned types of curdlan interact with Congo Red in very different ways. Single-helical curdlan can encapsulate Congo Red to form a stable, supramolecular dye assembly, which is demonstrated by the shortest distance between the H3 of curdlan and the phenyl groups of Congo Red, and also the same self-diffusion coefficients of Congo Red and curdlan. In contrast, random-coil curdlan interacts weakly with Congo Red and cannot enwrap it. This study offers insight into the specific structure-activity relationship of beta-(1,3)-glucans.