alpha 2-8 Sialic acid polymers: size, structure, and compositional analysis

A series of three variable assay procedures is described to provide overlapping information on the size, structure, and composition of the alpha 2-8 linked polysialic acid chains present on a wide variety of critical cell surface glycoproteins. Technical advances in instrumentation have permitted the development of new applications for a methodology involving the sequential use of periodate and borohydride to modify terminal sialic acid residues. The procedures described here provide a rapid and facile assay for (a) the determination of polysialic acid chain length, (b) the simultaneous identification of N-acetylneuraminic acid, N-glycolyneuraminic acid, and KDN (deaminated sialic acid) when present in a single preparation, (c) the ability to distinguish qualitatively between reducing and nonreducing polymers, and (d) the ability to determine the number of chains bound to a glycoprotein of known molecular weight.