ABSTRACT
Polysialic acid (PSA) was discovered as a major carbohydrate component of vertebrate brains largely on the basis of its unusual composition and size (Finne, 1982). As a linear homopolymer (n=8 to over 100) of alpha-2,8-linked sialic, PSA is a remarkably simple yet unique structure (Figure 1) (Finne and Makela, 1985; Livingston et al., 1988). This unique conformation allows for two very specific tools in the study of PSA, monoclonal antibodies (Acheson et al., 1991; Frosch et al., 198 5) and a fortuitous bacteriophagederived enzyme, endoneuraminidase (endo N) (Vimr et al., 1984). The value of this enzyme lies in the fact that it does not alter any other known sialic acid-containing structure (Hallenbeck et al., 1987) and is suitable for both in vitro and in vivo studies (Rutishauser et al., 1985).
