Förster resonance energy transfer (FRET) is a powerful tool for elucidating both structural and dynamic properties of unfolded or disordered biomolecules, especially in single-molecule experiments. However, the key observables, namely, the mean transfer efficiency and fluorescence lifetimes of the donor and acceptor chromophores, are averaged over a broad distribution of donor-acceptor distances. The inferred average properties of the ensemble therefore depend on the form of the model distribution chosen to describe the distance, as has been widely recognized. In addition, while the distribution for one type of polymer model may be appropriate for a chain under a given set of physico-chemical conditions, it may not be suitable for the same chain in a different environment so that even an apparently consistent application of the same model over all conditions may distort the apparent changes in chain dimensions with variation of temperature or solution composition. Here, we present an alternative and straightforward approach to determining ensemble properties from FRET data, in which the polymer scaling exponent is allowed to vary with solution conditions. In its simplest form, it requires either the mean FRET efficiency or fluorescence lifetime information. In order to test the accuracy of the method, we have utilized both synthetic FRET data from implicit and explicit solvent simulations for 30 different protein sequences, and experimental single-molecule FRET data for an intrinsically disordered and a denatured protein. In all cases, we find that the inferred radii of gyration are within 10% of the true values, thus providing higher accuracy than simpler polymer models. In addition, the scaling exponents obtained by our procedure are in good agreement with those determined directly from the molecular ensemble. Our approach can in principle be generalized to treating other ensemble-averaged functions of intramolecular distances from experimental data.
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Inferring properties of disordered chains from FRET transfer efficiencies
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28 March 2018
Research Article|
February 14 2018
Inferring properties of disordered chains from FRET transfer efficiencies

Wenwei Zheng;
Wenwei Zheng
1
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health
, Bethesda, Maryland 20892-0520, USA
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Gül H. Zerze;
Gül H. Zerze
2
Department of Chemical and Biomolecular Engineering
, Bethlehem, Pennsylvania 18015, USA
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Alessandro Borgia;
Alessandro Borgia
3
Department of Biochemistry, University of Zurich
, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Jeetain Mittal
;
Jeetain Mittal
2
Department of Chemical and Biomolecular Engineering
, Bethlehem, Pennsylvania 18015, USA
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Benjamin Schuler
;
Benjamin Schuler
a)
3
Department of Biochemistry, University of Zurich
, Winterthurerstrasse 190, 8057 Zurich, Switzerland
4
Department of Physics, University of Zurich
, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Robert B. Best
Robert B. Best
a)
1
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health
, Bethesda, Maryland 20892-0520, USA
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a)
Electronic addresses: wenweizheng@asu.edu; schuler@bioc.uzh.ch; and robertbe@helix.nih.gov.
b)
Current address: College of Integrative Sciences and Arts, Arizona State University, Mesa, Arizona 85212, USA.
J. Chem. Phys. 148, 123329 (2018)
Article history
Received:
September 28 2017
Accepted:
January 10 2018
Connected Content
A companion article has been published:
Protein distance and dynamics characteristics inferred from single-molecule FRET experiment
Citation
Wenwei Zheng, Gül H. Zerze, Alessandro Borgia, Jeetain Mittal, Benjamin Schuler, Robert B. Best; Inferring properties of disordered chains from FRET transfer efficiencies. J. Chem. Phys. 28 March 2018; 148 (12): 123329. https://doi.org/10.1063/1.5006954
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