Modification of cell surfaces by enzymatic introduction of special sialic acid analogues.

Taking advantage of the defined acceptor specificity of rat liver alpha 2,6-sialyltransferase, N-linked Gal beta 1,4GlcNAc-sequences of glycoconjugates at the plasma membrane of viable human erythrocytes and lymphoblastic IM-9 cells were modified to terminate in three NeuAc analogues endowed with special biochemical properties: sialidase-resistant 9-amino-NeuAc, O-acetylesterase-resistant 9-acetamido-NeuAc and photolabile 9-azido-NeuAc. Incorporation of the latter analogues and of parent NeuAc proceeded to similar values, whereas 9-amino-NeuAc yielded slightly reduced values.