Interactions of Coinage Metal Clusters with Histidine and Their Effects on Histidine Acidity; Theoretical Investigation

Nano cluster coinage metals and compounds have attracted lots of attention in medicine, catalysis fabrication of nano devices, and other applications according to their unique physical and chemical properties. The strength and reversibility of the inter-particle zwitterion-type electrostatic interactions between amino acid groups are evidenced by the slow disassembly upon increasing pH at ambient temperatures and its acceleration at elevated temperature. These findings provide new insight into the precise control of interfacial interactions and reactivities between amino acids anchored to nanoparticles and have broad implications in the development of colorimetric nanoprobes for amino acids. Histidine is one of the ۲۰ naturally occurring Į-amino acids that belongs to the group of aromatic and heterocyclic amino acids. It operates as a precursor of hormone histamine, and adjusts the amount of metal. It can bind a proton to the nonbonded electron pair of its ring nitrogen to become a weak acid at low pH. Histidine is the only amino acid that has a functional group that titrates in the physiological pH range. Histidine may be coordinated to metal atoms via amino groups, carboxyl groups, or the nitrogen atoms of the imidazole ring, thus acting as a mono-, bi-, or tridentate ligand. Gas-phase acidity (GPA) of organic compounds has been extensively investigated because it eliminates the effects of solvent and thus lets us study the intrinsic factors which influence the acidity of an organic compound. The reaction between metal clusters and organic molecules in the gas phase is an ideal environment in which the complexation mechanisms, the binding energies, the enthalpies, and the reactivity of the metal ions can be obtained in the absence of any complicating solvent effects.