Branched architecture of fucoidan characterized by dynamic and static light scattering

Branched architecture of fucoidans (sulfated fucose-rich polysaccharides) gained considerable interest in recent years in view of the effect of this branching on fucoidan's biological activity. The aim of this work was to characterize the branching architecture of the pristine and hydrolyzed fucoidan macromolecules of the marine seaweed Fucus vesiculosus. We studied the influence of the duration of acidic hydrolysis on the fucoidan macromolecules. The structure-sensitive ratios of macromolecular radii, obtained by dynamic and static (SLS) light scattering, and capillary viscometry corresponded to spherical form of the macromolecules, indicating their branched architecture. The structure-sensitive ratios were analyzed with respect to the molecular weight distributions obtained by size-exclusion chromatography. The Kratky representation of the angular dependences of SLS intensity provided a spectacular evidence for the fucoidans' branching. For the first time, the fucoidans' branching was characterized quantitatively by fitting the scattering form factor developed for hyperbranched macromolecules. Under acidic hydrolysis, the molecular mass and size of the fucoidan macromolecules decreased, but the globular form of macromolecules remained unchanged. Upon increasing the time of the acidic hydrolysis, the zeta-potential of the fucoidans changed from - 14 to - 27 mV. The hydrolyzed fucoidans, in turn, exhibited pronounced polyelectrolyte expansion in aqueous solutions when compared with the unhydrolyzed one.