Escape-time electrometry is a recently developed experimental technique that offers the ability to measure the effective electrical charge of a single biomolecule in solution with sub-elementary charge precision. The approach relies on measuring the average escape-time of a single charged macromolecule or molecular species transiently confined in an electrostatic fluidic trap. Comparing the experiments with the predictions of a mean-field model of molecular electrostatics, we have found that the measured effective charge even reports on molecular conformation, e.g., folded or disordered state, and non-uniform charge distribution in disordered proteins or polyelectrolytes. Here we demonstrate the ability to use the spectral dimension to distinguish minute differences in electrical charge between individual molecules or molecular species in a single simultaneous measurement, under identical experimental conditions. Using one spectral channel for referenced measurement, this kind of photophysical distinguishability essentially eliminates the need for accurate knowledge of key experimental parameters, otherwise obtained through intensive characterization of the experimental setup. As examples, we demonstrate the ability to detect small differences (∼5%) in the length of double-stranded DNA fragments as well as single amino acid exchange in an intrinsically disordered protein, prothymosin α.
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Spectrally resolved single-molecule electrometry
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28 March 2018
Research Article|
December 13 2017
Spectrally resolved single-molecule electrometry
F. Ruggeri;
F. Ruggeri
1
Department of Chemistry, University of Zürich
, Winterthurerstrasse 190, CH 8057 Zürich, Switzerland
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M. Krishnan
M. Krishnan
a)
1
Department of Chemistry, University of Zürich
, Winterthurerstrasse 190, CH 8057 Zürich, Switzerland
2
Department of Physics, University of Zürich
, Winterthurerstrasse 190, CH 8057 Zürich, Switzerland
Search for other works by this author on:
a)
Electronic mail: [email protected]
J. Chem. Phys. 148, 123307 (2018)
Article history
Received:
October 11 2017
Accepted:
November 20 2017
Citation
F. Ruggeri, M. Krishnan; Spectrally resolved single-molecule electrometry. J. Chem. Phys. 28 March 2018; 148 (12): 123307. https://doi.org/10.1063/1.5008936
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