Characterization of polysaccharide–protein complexes by size-exclusion chromatography combined with three detectors

Two water-soluble samples (TM1 and TM2) were extracted from Pleurotus tuber-regium using 0.9% aqueous NaCl at 20 and 80 °C to obtain relatively low molecular mass fractions. The chemical structure of TM1 was analyzed to be a branched heteropolysaccharide–protein complex, and the sugar moiety was mainly β-(1→6)-, β-(1→4)-, and β-(1→3)-linked glucan containing galactose and mannose. TM2 was a branched polysaccharide–protein complex, and the sugar moiety was mainly β-(1→6)-, β-(1→4)-, and β-(1→3)-linked glucan. Preparative size-exclusion chromatography (SEC) and analytical SEC combined with three detectors were used to detect the TM1 and TM2 samples, confirming that the proteins were bonded to the polysaccharides. Furthermore, analytical SEC combined with online laser light scattering, differential refractive index detector, and UV to determine the components, weight-average molecular mass (Mw) and chain conformation of the samples. The relatively low exponent values (ν  ) of 〈S2〉z1/2=kνMwν for the samples in 0.15 M aqueous NaCl at 25 °C suggested that TM1 and TM2 existed in compact sphere conformation in the aqueous solution. This work provided valuable information on the structure and chain conformation characterization of the polysaccharide–protein complex having relatively low Mw.

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