In addition to determining monosaccharides with the methyl group, we used monosaccharides without a methyl group, such as mannose (Man), glucose (Glc), and galactose (Gal), to determine their binding constant to IPO. Since the lower binding affinity of IPO titrated with Man, Glc or Gal couldn't get the best fitting for the titration curves, the n value was consequently fixed at 1.0 for fitting the curves ( [36] . The results show no differences with or without the methyl group of monosaccharides for binding properties in Artocarpin and Banlec possibly because of no aromatic side chain of residues in Artocarpin and Banlec like the residue Trp142 in IPO ( Figure 7A and 7B) . Interestingly, IPO shared similar binding properties to Jacalin for its Tyr122, which [37] . To examine the binding mode of Me-Man for Artocarpin, Banlec, Jacalin, and IPO, the binding position of Me-Man with IPO showed a distant binding site as compared with that for Artocarpin, Banlec, and Jacalin ( Figure 7D ). DN10IPO could be recovered as the mannose/glucose specific lectin if DN10IPO represented the monomeric IPO and wild-type IPO represented the tetrameric IPO. The monomeric IPO showed 5 times and 6 times binding affinity to Me-Man and Me-Glc, respectively, as compared with those of tetrameric IPO. Therefore, the N terminus of IPO is involved in the carbohydrate recognition, which results in the carbohydrate binding polyspecificity of tetrameric IPO. From the tetrameric IPO structure, the residue Leu5 and His8 in the N terminus of monomer B (chain B) forms 3 hydrogen bonds with the residue Asn19 in the loop between b3 and b4 of monomer A (chain A) (Figure 8 ). The hydrogen bonds might pull out the loop of b3-b4 and form a larger binding cavity for different carbohydrates in monomer A. However, in DN10IPO, the hydrogen bonds would disappear and might relocate the b3-b4 loop to cause a smaller binding cavity. The axial O4 of Me-Gal would not easily enter into the smaller binding cavity. The results might be confirmed by the crystal structure of DN10IPO-Me-Man in further study.