Origins of the pH-Responsive Photoluminescence of Peptide-Functionalized Au Nanoclusters

Ultrasmall peptide-protected gold nanoclusters are a promising class of bioresponsive material exhibiting pH-sensitive photoluminescence. We present a theoretical insight into the effect peptide-ligand environment has on pH-responsive fluorescence, with the aim of enhancing the rational design of go...

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Bibliographic Details
Published in:ACS nano 2022-12, Vol.16 (12), p.20129-20140
Main Authors: Zanetti-Polzi, Laura, Charchar, Patrick, Yarovsky, Irene, Corni, Stefano
Format: Article
Language:English
Subjects:
Amines
Gold - chemistry
Hydrogen-Ion Concentration
Metal Nanoparticles - chemistry
Peptides
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Summary:Ultrasmall peptide-protected gold nanoclusters are a promising class of bioresponsive material exhibiting pH-sensitive photoluminescence. We present a theoretical insight into the effect peptide-ligand environment has on pH-responsive fluorescence, with the aim of enhancing the rational design of gold nanoclusters for bioapplications. Employing a hybrid quantum/classical computational methodology, we systematically calculate deprotonation free energies of N-terminal cysteine amine groups in proximity to the inherently fluorescent core of Au25(Peptide)18 nanoclusters. We find that subtle changes in hexapeptide sequence alter the electrostatic environment and significantly shift the conventional N-terminal amine pK a expected for amino acids free-in-solution. Our findings provide an insight into how the deprotonation equilibrium of N-terminal amine and side chain carboxyl groups cooperatively respond to solution pH changes, explaining the experimentally observed, yet elusive, pH-responsive fluorescence of peptide-functionalized Au25 clusters.
ISSN:1936-0851
1936-086X
DOI:10.1021/acsnano.2c04335