Fig. 2.

ST assay using sheep erythrocytes as sialyl residue acceptors. A complete reaction mixture consisting of sialidase-treated SRBCs, purified α2,6-ST, and CMP-5FITC-NEU was added at the concentrations described in Materials and Methods and incubated for 2 h at 37ºC. The complete mixture gave a strong signal [solid peaks, A–C; mean fluorescence intensity (MFI)=637]. Omission of the CMP-5-FITC-NEU (light peak, A; MFI=72) or ST (light peak, B; MFI=219) or heat inactivation (100ºC for 30 min) of ST (light peak, C; MFI=205) reduced the fluorescence of the SRBCs. No signal was evident when the SRBC acceptor was omitted.