(a) The monomer of ristocetin-A. The aglycon is in blue and the sugars are in orange. (b) The dimer of the asymmetric unit. The local twofold axis building the dimer is vertical in the plane of the figure. The four hydrogen bonds of the short β-sheet are represented by red dotted lines. Acetone and water molecules are not reported for clarity. (c) Electron density (omit-map, contouring 3.5σ above mean value) of one of the two tetrasaccharide groups connected to residue 4.