IPO-Me-Gal belongs to an orthorhombic space group P2 1 2 1 2 1 . The Matthews coefficient and solvent content were 2.25 Å 3 /Da and 45.2%, respectively, for 4 molecules in an asymmetric unit. The 4 IPO-Me-Gal molecules shown in Figure 1D form the same tetrameric association as that of IPO-Me-Glc. On the basis of crystal packings of apo IPO and IPO-carbohydrate complexes, IPO would form a tetrameric association.