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Gielen F, Butz M, Rees EJ, Erdelyi M, Moschetti T, Hyvönen M, Edel JB, Kaminski CF, Hollfelder F. Quantitative Affinity Determination by Fluorescence Anisotropy Measurements of Individual Nanoliter Droplets. Anal Chem 2017; 89:1092-1101. [PMID: 28192993 PMCID: PMC5287478 DOI: 10.1021/acs.analchem.6b02528] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Fluorescence anisotropy measurements of reagents compartmentalized into individual nanoliter droplets are shown to yield high-resolution binding curves from which precise dissociation constants (Kd) for protein-peptide interactions can be inferred. With the current platform, four titrations can be obtained per minute (based on ∼100 data points each), with stoichiometries spanning more than 2 orders of magnitude and requiring only tens of microliters of reagents. In addition to affinity measurements with purified components, Kd values for unpurified proteins in crude cell lysates can be obtained without prior knowledge of the concentration of the expressed protein, so that protein purification can be avoided. Finally, we show how a competition assay can be set up to perform focused library screens, so that compound labeling is not required anymore. These data demonstrate the utility of droplet compartments for the quantitative characterization of biomolecular interactions and establish fluorescence anisotropy imaging as a quantitative technique in a miniaturized droplet format, which is shown to be as reliable as its macroscopic test tube equivalent.
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Affiliation(s)
- Fabrice Gielen
- Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom.,Living Systems Institute, University of Exeter , Stocker Road, Exeter, EX4 4QD, United Kingdom
| | - Maren Butz
- Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Eric J Rees
- Department of Chemical Engineering and Biotechnology, New Museums Site , Pembroke Street, Cambridge, CB2 3RA, United Kingdom
| | - Miklos Erdelyi
- Department of Chemical Engineering and Biotechnology, New Museums Site , Pembroke Street, Cambridge, CB2 3RA, United Kingdom.,Department of Optics and Quantum Electronics, University of Szeged , Dom ter 9, Szeged, Hungary
| | - Tommaso Moschetti
- Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Marko Hyvönen
- Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
| | - Joshua B Edel
- Department of Chemistry, Imperial College London , South Kensington, London, SW7 2AZ, United Kingdom
| | - Clemens F Kaminski
- Department of Chemical Engineering and Biotechnology, New Museums Site , Pembroke Street, Cambridge, CB2 3RA, United Kingdom
| | - Florian Hollfelder
- Department of Biochemistry, University of Cambridge , 80 Tennis Court Road, Cambridge, CB2 1GA, United Kingdom
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