Figure 5
From: Theoretical study on the polar hydrogen-π (Hp-π) interactions between protein side chains
The Hp-π interaction structures and HOMOs of three amino acid interaction pairs. (A) Structure of Hp-π interaction pair CH3NH2-C6H6. The two polar hydrogen atoms of CH3NH2 point to the benzene ring perpendicularly. (B) The HOMO of Hp-π interaction pair CH3NH2-C6H6. The polar hydrogen atoms are in close touching with the π-orbital of C6H6. (C) Structure of Hp-π interaction pair C6H5OH-C6H6. The polar hydrogen atom of C6H5OH points to the center of C6H6. (D) The HOMO of Hp-π interaction pair C6H5OH-C6H6. (E) Structure of Hp-π interaction pair imidazole-C6H6. The polar hydrogen atom of imidazole points to the center of C6H6 perpendicularly. (F) The HOMO of Hp-π interaction pair imidazole-C6H6.