Sialylation of lactosyl lipids in membrane microdomains by T. cruzi trans-sialidaseElectronic supplementary information (ESI) available: Experimental details; spectra and CACs of novel lipids; measurements of E/M ratios and flip-flop rates; conditions and representative HPLC traces for enzymatic reactions. See DOI: 10.1039/c4ob01852d

A synthetic perfluoroalkyl-tagged lactosyl glycolipid has been shown to form lipid microdomains in fluid phospholipid bilayers. When embedded in the membranes of phospholipid vesicles, this glycolipid was trans -sialylated by soluble T. cruzi trans -sialidase (TcTS) to give a perfluoroalkyl-tagged glycolipid that displayed the ganglioside GM 3 epitope, with up to 35% trans -sialylation from fetuin after 18 h. Following sialylation, vesicles bearing this Neu5Ac(α2-3)Gal(β1-4)Glc sequence in their "glycocalyx" were recognised and agglomerated by the lectin M. amurensis leukoagglutinin. Monitoring TcTS-mediated trans -sialylation by HPLC over the first 6 h revealed that enzymatic transformation of bilayer-embedded substrate was much slower than that of a soluble lactosyl substrate. Furthermore, clustering of the lactose-capped glycolipid into "acceptor" microdomains did not increase the rate of sialic acid transfer from fetuin by soluble TcTS, instead producing slight inhibition. Soluble T. cruzi trans -sialidase transformed a synthetic lactosyl glycolipid in microdomains more slowly than the same substrate dispersed across the bilayer surface, producing phospholipid vesicles with a Neu5Ac(α2-3)Gal(β1-4)Glc "glycocalyx".