Fluorescence Analysis of Galactose, Lactose, and Fucose Interaction with the Cholera Toxin B Subunit

Synthesis of Lactose Dendrimers and Multivalency Effects in Binding to the Cholera Toxin B Subunit

“…toxin B subunit was fluorescence spectroscopy, as described for monovalent ligands. [24] CTB contains one tryptophan residue (Trp 88), the fluorescence of which is affected by the binding of carbohydrate ligands. The degree to which this happens is greatly dependent on the nature of the ligand.…”

“…The involvement of cooperativity in CTB binding is a well known phenomenon, observed previously with the GM1 oligosaccharide but not with mono-or disaccharides. [24,33] By use of the same analysis, the K d for the tetravalent 9 was determined to be 99 µ (n ϭ1.4), while the octavalent 10 exhibited the strongest binding, with a K d of 33 µ (n ϭ 1.4) and a relative potency of 545. The binding studies indicate a modest multivalent enhancement on going from 8 to 10.…”

“…[23] We chose to take the widely available disaccharide lactose as our monovalent starting point. Lactose has been shown to bind to CTB in the millimolar range, [24] and an X-ray structure with 5 units of this compound bound to the closely related heat-labile enterotoxin from E. coli [25] (LT, 80% sequence identity with CT) shows a binding mode of the terminal galactose in this structure similar to that of this residue in the structure of the CTB-GM1 pentasaccharide complex. [26] In CTB, all binding sites are on the same face of the molecule, which creates the potential for simultaneous binding of several or even all the binding sites to a single multivalent ligand and suggests that enhanced affinity through the chelate effect should be possible.…”

Screening of Garlic Water Extract for Binding Activity with Cholera Toxin B Pentamer by NMR Spectroscopy – An Old Remedy Giving a New Surprise

“…The observed decrease in CTB fluorescence in the presence of ASw_r_s is similar to those observed for weak-binding monosaccharides. [17] The strong-binding GM1, in contrast, was reported to promote an increase in CTB fluorescence with a blue shift of the fluorescence maximum. [17] The midpoint of the ASw_r_s titration was estimated as 50 µg·mL -1 .…”

“…[17] The strong-binding GM1, in contrast, was reported to promote an increase in CTB fluorescence with a blue shift of the fluorescence maximum. [17] The midpoint of the ASw_r_s titration was estimated as 50 µg·mL -1 . In any case, this qualitative fluorescence data support the NMR results and indicate that the ASw_r_s fraction is the only one enriched in the compound(s) that bind(s) CTB.…”