Locating the nucleation sites for protein encapsulated gold nanoclusters: a molecular dynamics and fluorescence study

Fluorescent gold nanoclusters encapsulated by proteins have attracted considerable attention in recent years for their unique properties as new fluorescence probes for biological sensing and imaging. However, fundamental questions, such as the nucleation sites of gold nanoclusters within proteins an...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2015-01, Vol.17 (34), p.21935-21941
Main Authors: Russell, B A, Kubiak-Ossowska, K, Mulheran, P A, Birch, D J S, Chen, Y
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Capsules
Cattle
Clusters
Encapsulation
Fluorescence
Fluorescence Resonance Energy Transfer
Gold
Gold - chemistry
Humans
Hydrogen-Ion Concentration
Metal Nanoparticles - chemistry
Molecular dynamics
Molecular Dynamics Simulation
Nanostructure
Nucleation
Protein Structure, Tertiary
Proteins
Tryptophan - chemistry
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Summary:Fluorescent gold nanoclusters encapsulated by proteins have attracted considerable attention in recent years for their unique properties as new fluorescence probes for biological sensing and imaging. However, fundamental questions, such as the nucleation sites of gold nanoclusters within proteins and the fluorescence mechanism remain unsolved. Here we present a study of the location of gold nanoclusters within bovine serum albumin (BSA) combining both fully atomistic molecular dynamic (MD) simulations and fluorescence spectroscopic studies. The MD simulations show gold clusters growing close to a number of cysteine sites across all three domains of BSA, although just two major sites in domains IIB and IA were found to accommodate large clusters comprising more than 12 atoms. The dependence of the fluorescence on pH is found to be compatible with possible nucleation sites in domains IIB and IA. Furthermore, the energy transfer between tryptophan and gold nanoclusters reveals a separation of 29.7 Å, further indicating that gold nanoclusters were most likely located in the major nucleation site in domain IIB. The disclosure of the precise location of the gold nanoclusters and their surrounding amino acid residues should help better understanding of their fluorescence mechanism and aid their optimization as fluorescent nanoprobes.
ISSN:1463-9076
1463-9084
DOI:10.1039/c5cp02380g