Selective spin-labelling of an N-acetylneuraminic acid residue in the Fab-region oligosaccharide of immunoglobulin M.

A method is proposed for spin-labelling using 2,2,6,6-tetramethyl-4-aminopiperidine-1-oxyl, the N-acetylneuraminic acid residue within the Fab-region oligosaccharide of immunoglobulin M (IgM). The selectivity of spin-labelling was achieved by the controlled periodate oxidation of the oligosaccharide groups of the IgM prior to the spin-labelling. The spin-labelled IgM prepared in this way may be useful for the studies of dynamics of the IgM structure, particularly upon antigen binding.