A Mechanistic and Kinetic Study of the Formation of Metal Nanoparticles by Using Synthetic Tyrosine‐Based Oligopeptides

Abstract

Synthetic oligopeptides containing redox-active tyrosine residues have been employed to prepare gold and silver nanoparticles. In this reduction process an electron from the tyrosinate ion of the peptide is transferred to the metal ion at basic pH through the formation of a tyrosyl radical, which is eventually converted to its dityrosine form during the reaction. This reaction mechanism was confirmed from UV-visible, fluorescence, and EPR spectroscopy and was found to be pH-dependent. Transmission electron microscopy measurement shows that the average size and the monodispersity of gold nanoparticles increase as the number of tyrosine residues in the peptide increases. The kinetic study, based on spectrophotometric measurements of the surface plasmon resonance optical property, shows that the rate of formation of gold nanoparticles was much faster at higher pH than at lower pH and was also dependent on the number of tyrosine residues present in the peptide. The dityrosine form of the peptide was found to retain reducing properties like those of tyrosine in basic medium.

On the selection and design of proteins and peptide derivatives for the production of photoluminescent, red-emitting gold quantum clusters

“…However, a strong fluorescence band was observed at 400 nm, which indicated the formation of dityrosine [47][48][49] as a result of a redox reaction between Au III and tyrosine (dityrosine was not detected if HAuCl 4 was not added to the amino acid mixtures). One can find this intriguing since cysteine and methionine can form highly stable complexes with gold, limiting the reducibility of Au III in the case of tryptophan [26].…”

Trypsin-Stabilized Fluorescent Gold Nanocluster for Sensitive and Selective Hg2+ Detection

“…This is probably because the reduction ability of tyrosine in trypsin is activated with the alkaline pH. 22,27 Recently, Tan et al have also investigated the amino-acid sequence in peptides for the synthesis of peptide-stabilized Au NPs. 34 It was found that tyrosine and tryptophan showed fairly gold reduction ability of AuCl4 -when present in the peptide sequence.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Recently, there has been increasing interest in the development of biological synthesis for Au NPs because of the need for an environmentally acceptable solvent system and eco-friendly reducing and capping agents. [26][27][28] Xie et al first demonstrated the synthesis of highly fluorescent protein-stabilized Au NCs using a bovine-serum alubumin (BSA)-templated method. 22 The as-prepared Au NCs consisted of 25 gold atoms (Au25) with a red emission at 640 nm.…”

Silver nanoparticle engineering via oligovaline organogels

“…This is unlike earlier examples where the peptides are mostly oxidized during particle formation and could therefore not be reused. 11,13,45 Here, the peptide can be separated from the colloidal silver by dissolution of the composite in methanol. After centrifugation and solvent evaporation, the peptide can be recovered.…”