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Issue 10, 2015
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Size-dependent tuning of horseradish peroxidase bioreactivity by gold nanoparticles

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Abstract

Molecules with diverse biological functions, such as heme peroxidases, can be useful tools for identifying potential biological effects of gold nanoparticles (AuNPs) at the molecular level. Here, using UV-Vis, circular dichroism, dynamic light scattering, and electron spin resonance spectroscopy, we report tuning of horseradish peroxidase (HRP) bioactivity by reactant-free AuNPs with diameters of 5, 10, 15, 30 and 60 nm (Au-5 nm, Au-10 nm, Au-15 nm, Au-30 nm and Au-60 nm). HRP conjugation to AuNPs was observed with only Au-5 nm and Au-10 nm prominently increasing the α-helicity of the enzyme to extents inversely related to their size. Au-5 nm inhibited both HRP peroxidase activity toward 3,3′,5,5′-tetramethylbenzidine and HRP compound I/II reactivity toward 5,5-dimethyl-1-pyrroline N-oxide. Au-5 nm enhanced the HRP peroxidase activity toward ascorbic acid and the HRP compound I/II reactivity toward redox-active residues in the HRP protein moiety. Further, Au-5 nm also decreased the catalase- and oxidase-like activities of HRP. Au-10 nm showed similar, but weaker effects, while Au-15 nm, Au-30 nm and Au-60 nm had no effect. Results suggest that AuNPs can size-dependently enhance or inhibit HRP bioreactivity toward substrates with different redox potentials via a mechanism involving extension of the HRP substrate access channel and decline in the redox potentials of HRP catalytic intermediates.

Graphical abstract: Size-dependent tuning of horseradish peroxidase bioreactivity by gold nanoparticles

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Publication details

The article was received on 28 Nov 2014, accepted on 30 Jan 2015 and first published on 03 Feb 2015


Article type: Paper
DOI: 10.1039/C4NR07056A
Author version available: Download Author version (PDF)
Citation: Nanoscale, 2015,7, 4505-4513
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    Size-dependent tuning of horseradish peroxidase bioreactivity by gold nanoparticles

    H. Wu, Y. Liu, M. Li, Y. Chong, M. Zeng, Y. M. Lo and J. Yin, Nanoscale, 2015, 7, 4505
    DOI: 10.1039/C4NR07056A

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