Ultrastructural modulations of cell surface determinants in pathological processes.

A novel approach for the ultrastructural localization of surface sialic acids is presented. Membrane-bound sialyl residues are chemically modified in situ by the covalent attachment of biotinyl residues, the latter of which are subsequently localized by ferritin-conjugated avidin. In contrast to previous methods, which have been based on electrostatic interactions, the above method does not affect cell surface charge.