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arXiv · 1909.08227

Deep UV plasmonic enhancement of single protein autofluorescence in zero-mode waveguides

Aleksandr Barulin·Jean-Benoît Claude·Satyajit Patra·Nicolas Bonod·Jérôme Wenger
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Abstract

Single molecule detection provides detailed information about molecular structures and functions, but it generally requires the presence of a fluorescent marker which can interfere with the activity of the target molecule or complicate the sample production. Detecting a single protein with its natural UV autofluorescence is an attractive approach to avoid all the issues related to fluorescence labelling. However, the UV autofluorescence signal from a single protein is generally extremely weak. Here, we use aluminum plasmonics to enhance the tryptophan autofluorescence emission of single proteins in the UV range. Zero-mode waveguides nanoapertures enable observing the UV fluorescence of single label-free beta-galactosidase proteins with increased brightness, microsecond transit times and operation at micromolar concentrations. We demonstrate quantitative measurements of the local concentration, diffusion coefficient and hydrodynamic radius of the label-free protein over a broad range of zero-mode waveguide diameters. While the plasmonic fluorescence enhancement has generated a tremendous interest in the visible and near-infrared parts of the spectrum, this work pushes further the limits of plasmonic-enhanced single molecule detection into the UV range and constitutes a major step forward in our ability to interrogate single proteins in their native state at physiological concentrations.

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Aleksandr Barulin, Jean-Benoît Claude, Satyajit Patra, Nicolas Bonod, Jérôme Wenger. 2019-09-18. Deep UV plasmonic enhancement of single protein autofluorescence in zero-mode waveguides. https://doi.org/10.1021/acs.nanolett.9b03137

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