engleski

Computational modelling of the interface between metallic nanoparticles and cysteine

Introduction The emergence of metallic nanoparticles (NPs) for biomedical uses prompted the need for detailed evaluation of their safety, interactions and fate in biological media. The interactions of NPs with biomolecules may result in biotransformations of both species, with unforeseen consequences for the human body.(1) Metallic NPs are particularly prone to reacting with thiols, due to the high affinity of sulphur for metals.(2) Here, we examine the binding and oxidative dimerization of cysteine, a model biothiol, during the formation and incubation of silver and gold NPs in cysteine-rich environment. The interaction is modelled using in silico methods and the reaction mechanism is proposed. Results The mechanistic insight into the nano-bio interface is offered by means of computational methods: quantum chemistry and molecular dynamics. The quantum chemical approach, conducted with Gaussian software, yielded the optimized complexes of cysteine monomers and dimers with Agn and Aun (n=2, 4) clusters and the transition states of the dimerization reaction. The optimized complexes confirmed the tendency of cysteine to interact with Ag and Au through the thiol and carboxyl groups, and the transition states allowed for the calculation of energy barriers of the dimerization reaction. Molecular dynamics calculations, conducted with Amber software, demonstrated stable attachment of cysteine monomers and dimers on the Ag or Au surface and provided the binding energies. Conclusions The lowering of energy barriers for dimerization is observed in the presence of metal clusters, therefore the mechanism of mechanism of cysteine dimerization catalysed by NPs is proposed. The dimerization is followed by binding to NP surface, which is shown to be spontaneous for both cysteine species.

nanoparticles, silver, gold, cysteine, computational

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