 Wing I is usually a heteroaromatic ring and wing II is a phenyl or allyl substituent.Wing I has a functional group at one side of the ring which is capable of accepting and/or donating hydrogen bonds with the main chain of the amino acids Lys-101 and Lys-103.Wing II interacts through π-π interactions with a hydrophobic pocket, formed in most part by the side chains of aromatic amino acids.