Structural characterization of #beta#-D-(1->3,1->6)-linked glucans using NMR spectroscopy

摘要

Nondestructive structrual analysis of a series of #beta#-D-(1->3,1->6)-linked glucans(laminaran,curdlan,yeast glucan,scleroglucan,etc.)was performed using two-dimensional NMR spectroscopy.The relative ratios of H-1 at different AGUs provided the information about Dpnand DB.The#alpha#-,and #beta#-anomeric protons on reducing terminals were assigned at 5.02approx 5.03 ppm (J3.6approx3.7HZ),and 4.42approx4.43ppm(J7.6approx7.9Hz),respectively,whereas the H-1 protons of internal AGUs and #beta#-(1->6)-branched AGUs appeared at 4.56approx4.59 ppm (J 7.6approx7.8 Hz),and 4.26approx 4.28 (J7.6approx 10.6Hz),respectively,in a mixed solvent of 6:1 Me_2SO-d_6-D_2Oat 80deg C.In the solvent,the OH peaks were eliminated from the spectra allowing th4e H-1 protons to appear clearly.In addition,teh nonreducing terminal H-1 and H-1 at the the AGU next to reducing terminal could be assigned at 4.45approx4.46 ppm(J7.8approxJ7.9Hzs),and 4.51approx4.53 ppm (J7.8hZ),respectively.The DP_n of the laminaran was 33 (polydispersity 1.12)and the DB was 0.07.The number of glucosyl units in the side chain of laminaran is more than one.The DP_n and DB of the water-insoluble yeast glucan were 228 and 0.003,respectively.However the DP_n of water soluble yeast glucan phaosphate and curdlan was changed upon the number of freeze-drying processes and the content of water in the mixed solvent,respectively.And the DB of those were calculated as 0.02 and 0,respectively.The DB of scleroglucan was precisely calculated as 0.33,compared with the previously reported data. The H-1s at different AGUs of the various #beta#-D-(1->3,1->6)-linked glucans having different DB can be effectively used to determine the DP and DB of polysaccharides in a simple and non-destructive manner.