Determination of the Bioactive Conformation of the Carbohydrate Ligand in the E‐Selectin/Sialyl Lewis^X Complex

A mixture of different conformers of the flexible tetrasaccharide sialyl Lewis^x is presented in solution to the E‐selectin receptor, which binds only one conformation, as shown by NMR spectroscopy. The experimentally determined transfer NOEs can be used to derive proton–proton distance restrictions, which together with the confomer ensemble obtained by Metropolis Monte Carlo simulations, can be used to determine the conformation of sialyl Lewis^x in the complexed state. (Figure Presented.)