Quantifying the π-Stacking Interactions in Nitroarene Binding Sites of Proteins

Area of Science:

• Biochemistry
• Computational Chemistry
• Structural Biology

Background:

• Nitroarenes are prevalent in pharmaceuticals and biological systems.
• Understanding nitroarene-protein interactions is key to drug discovery and toxicology.
• Aromatic amino acids (histidine, phenylalanine, tyrosine, tryptophan) are common in protein binding sites.

Purpose of the Study:

• To investigate the stacking interactions between nitroarenes and aromatic amino acid side chains.
• To quantify the binding energies and analyze the factors influencing these interactions.
• To correlate computational findings with structural data from the Protein Data Bank (PDB).

Main Methods:

• Density Functional Theory (DFT) and ab initio computations were used to model nitroarene-amino acid dimers.
• High-level coupled cluster calculations (CCSD(T)) refined binding energies.
• Analysis of crystal structures from the Protein Data Bank (PDB) identified real-world binding sites.

Main Results:

• Nitroarene interactions with aromatic amino acids are strong, with binding energies up to -14.6 kcal mol(-1).
• The position of nitro groups significantly impacts interaction strength and orientation.
• Interaction strength generally follows the order: Tryptophan > Tyrosine > Phenylalanine ≈ Histidine.
• PDB analysis confirmed frequent π-stacking interactions between nitroarenes and aromatic residues.

Conclusions:

• π-stacking is a significant force in nitroarene-protein binding.
• The non-additive nature of nitro substituents in these interactions is due to direct substituent-amino acid contacts.
• Computational models align with structural observations, providing insights into drug-receptor interactions.