ANTS (8-aminonaphthalene-1,3,6-trisulfonic acid, disodium salt) is a highly negatively charged dye with an amino group that can be coupled to an aldehyde or ketone group to form an unstable Schiff base. The Schiff base is usually chemically reduced by sodium borohydride (NaBH4) or sodium cyanoborohydride (NaB(CN)H3) to form a stable linkage (1).