Spin-labelling of sialic acid in soluble and cell-surface glycoproteins

A new, mild method is described for spin-labelling sialic acid residues in situ. The procedure involves the formation of C-1 sialamides and has been applied to a serum glycoprotein, a mucin, tissue sections from human colon, and erythrocyte membrane components. The selectivity of the method and its possible applicability to other types of labelling are discussed.