Interactions of Ag+ ions and Ag-nanoparticles with protein. A comparative and multi spectroscopic investigation

UV-visible and florescence spectroscopic methods have been applied to analyze the binding capabilities of Ag+ ions and AgNPs with bovine serum albumin (BSA). UV-visible studies revealed that BSA acted as a ligand towards both Ag+ and AgNPs, and provides potential site for coordination. BSA fluorescence was quenched significantly by the quenchers (Ag+ and AgNPs). The binding constant, quenching constant, quantum yield, and coordination sites were evaluated. The Ag+ ions has strong binding and quenching efficiency towards BSA than that of AgNPs. The distance between the tryptophan and acceptor decreases from 127 angstrom to 72 angstrom with Ag+ ions from 0.6 to 20.0 x 10(-5) mol/L. The energy transfer from BSA to ligand (Ag+ ions and AgNPs) follows a surface energy transfer process with a 1/d(4) distance dependence. This is found to be according to strong coordinating affinity of metal ions with structural unit of protein, which helps to understand the mechanism of bacterial cell death in presence of metal ions and/or metal NPs. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

UV-visible and fluorescence spectroscopic methods were used to study the binding capabilities of Ag+ ions and AgNPs with bovine serum albumin (BSA), revealing that BSA acted as a ligand for both and showing significant fluorescence quenching. It was found that Ag+ ions had stronger binding and quenching efficiency towards BSA compared to AgNPs, with the distance between tryptophan and acceptor affecting the energy transfer process.