Computational study of dacarbazine-amino acid interactions

This theoretical study examines the interaction between dacarbazine (DTIC) and a select group of amino acids-lysine (Lys), histidine (His), threonine (Thr), and isoleucine (Ile)-utilizing density functional theory (DFT) calculations. The research offers a comprehensive analysis of the noncovalent interactions that dictate the stability of DTIC-amino acid complexes, including hydrogen bonding, electrostatic forces, and hydrophobic contacts. The findings indicate that hydrogen bonding plays a crucial role in stabilizing these complexes, with the DTIC-His interaction demonstrating the highest stability energy of -19.89 kcal/mol. Natural bond orbital (NBO) calculations further substantiate this observation, revealing a significant second-order perturbation energy of 34.55 kcal/mol, highlighting the strong electronic interactions between DTIC and histidine. Additional insights from the Quantum Theory of Atoms in Molecules (QTAIM) and global reactivity descriptors affirm the presence of robust hydrogen bonds, particularly in the DTIC-His complex. The study also investigates the optical properties of these complexes through UV-vis calculations, identifying distinct characteristic wavelengths. Notably, the DTIC-His complex absorbs at 321.36 nm, while DTIC-Ile exhibits absorption at 329.61 nm. This research underscores the critical role of histidine in binding to dacarbazine, providing quantitative insights into the binding affinities and electronic properties of these interactions. These findings enhance the understanding of the molecular mechanisms underlying DTIC-amino acid complexes, with potential implications for drug design and biochemical applications.