Table 4. Comparison of the Polar (Hydrogen Bonds) and Nonpolar Interactions (Hydrophobic, van der Waals Contacts) of Blumeatin and Quercetin (Natural Ligand) with the Residues from the Active Site of XO.

ligand	conventional hydrogen bonds, bond lengths (in Å in parentheses), and typesa	residues in van der Waals contact or hydrophobic interaction
blumeatin	via O atom of Thr1010: 2.70:C=O and 3.26:O–H; via N atom of Thr1010: 2.93:C=O and 2.97:O–H; Val1011 (3.08:C=O); Arg880 (2.03:O–H); Phe914 (3.48:π–π and 4.04:(O–H) π–σ); Phe1009 (π–π); Ala1078 (3.58:O–H and 5.22:π–alkyl); Ala1079 (3.96:π–σ); Leu1014 (3.47:π–σ); Leu873 (4.74:π–alkyl), Leu648 (5.05:π–alkyl), Ala910 (4.37:π–alkyl)	Glu802, Asn768, Ser1008, Glu1261, Phe1013, Phe1150, Ser876, Lys771, Thr803
quercetin	Arg880, Thr1010, Glu802, Phe914, Ala1079, Phe1009, Leu873, Leu1014, Leu648, Val1011	Ser1008, Phe1150, Ser876, Phe1013, Lys771, Pro1076, Ala1078

^aBold text denotes mutual residues that are in interaction with both blumeatin and quercetin.