Silver cluster-amino acid interactions: a quantum-chemical study

Area of Science:

• Computational Chemistry
• Biophysical Chemistry
• Materials Science

Background:

• Silver ions and clusters are increasingly used in biomedical applications.
• Understanding the interaction between silver and biomolecules like amino acids is crucial for designing new silver-based materials and therapies.
• Previous studies have explored silver-amino acid interactions, but detailed computational analysis of silver clusters is less common.

Purpose of the Study:

• To investigate the binding affinities of silver ion (Ag+) and a neutral silver dimer (Ag2) with various amino acids.
• To elucidate the nature of the chemical bonds formed between silver species and amino acids using advanced computational methods.
• To identify specific amino acids that exhibit strong binding with silver clusters for potential applications.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model the interactions.
• Ab initio MP2 (Møller–Plesset perturbation theory) method was utilized for high-level electronic structure calculations.
• Natural Bond Orbital (NBO) analysis was performed to quantify charge transfer and bonding characteristics.
• Atoms-in-Molecules (AIM) theory was applied to characterize the interaction types (electrostatic vs. covalent).

Main Results:

• Deprotonated anionic amino acids demonstrated significantly higher binding energies with the Ag2 cluster compared to protonated forms or interactions with Ag+.
• Cysteine, aspartic acid, and tyrosine, with deprotonated side chains, exhibited the strongest binding energies with Ag2, reaching up to -30.9 kcal mol-1.
• Binding energies for deprotonated cysteine, glutamic acid, tyrosine, and aspartic acid with Ag+ were reported for the first time.
• NBO and AIM analyses indicated that the bonds between amino acids and the Ag2 cluster are predominantly a mix of electrostatic and covalent interactions.

Conclusions:

• The Ag2 cluster forms stronger bonds with deprotonated amino acids than Ag+, suggesting potential for targeted delivery or functionalization.
• Cysteine, aspartic acid, and tyrosine are identified as key amino acids for strong interactions with silver clusters.
• The findings provide valuable insights into the fundamental chemistry of silver-biomolecule interactions, guiding the development of novel silver-based nanomaterials and therapeutic agents.