To determine the binding constants of IPO to Me-Man, Me-Glc and Me-Gal, 1 mM IPO solution was titrated with 25 mM carbohydrate solution. The interaction of IPO and carbohydrate was an exothermal reaction. The optimal curves and thermodynamics parameters could be fitting and calculated by Microcal Origin 7.0. The K A of IPO to Me-Man was the highest, 7.04610 3 M 21 . The K A values for Me-Gal and Me-Glc were 4.09610 3 M 21 and 2.01610 3 M 21 , respectively (Table 2 and Figure 5 ).