Understanding the impact of halogen functional group (Br, Cl, F, OH) in amprenavir ligand of the HIV protease.

We focused our attention towards the most dreadful disease that threatens the mankind of 20 century - Acquired immunodeficiency syndrome (AIDS), caused through the human immunodeficiency virus (HIV) and a sexually transmitted infection (STI). In this study, our foremost interest was to identify the potency and stability of HIV ligand- Amprenavir (APV) and its modelled functional group (Br, Cl, F, CF, CH, NH) ligands through halogen and hydrogen bond contact, which will have a clear portrait on the structure activity of protein ligand interactions. This will assist chemist in synthesizing novel APV ligands, which are expected to inhibit the activity of HIV-1 protease enzyme. The binding strength of Amprenavir ligand with interacting hinge region amino acid side chains: Isoleucine (ILE 147, 150, 184), Valine (VAL 82), Alanine (ALA 28), Aspartic acid (25, 30, 125, 130) and Glycine (GLY 127, 149) were understood through interaction energy calculations at HF, B3LYP, M02X, MP2 level of theories for different basis set (6-311 G**, LANL2DZ). The present work will reveal an understandable picture about the halogen and hydrogen bond interaction that grip the contact of ligand and amino acids in the hinge region. Overall the Halogen atom (Br, Cl, F) functional groups improved the binding strength of APV in HIV protease; which provide a new novel path for the functional group preference on the ligand that enclose perfectly with the amino acid in the hinge region.Communicated by Ramaswamy H. Sarma.