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Science 317 (5845): 1732-1736

Copyright © 2007 by the American Association for the Advancement of Science

Free-Solution, Label-Free Molecular Interactions Studied by Back-Scattering Interferometry

Darryl J. Bornhop,1* Joey C. Latham,2 Amanda Kussrow,1 Dmitry A. Markov,3 Richard D. Jones,1 Henrik S. Sørensen4

Abstract: Free-solution, label-free molecular interactions were investigated with back-scattering interferometry in a simple optical train composed of a helium-neon laser, a microfluidic channel, and a position sensor. Molecular binding interactions between proteins, ions and protein, and small molecules and protein, were determined with high dynamic range dissociation constants (Kd spanning six decades) and unmatched sensitivity (picomolar Kd's and detection limits of 10,000s of molecules). With this technique, equilibrium dissociation constants were quantified for protein A and immunoglobulin G, interleukin-2 with its monoclonal antibody, and calmodulin with calcium ion Ca2+, a small molecule inhibitor, the protein calcineurin, and the M13 peptide. The high sensitivity of back-scattering interferometry and small volumes of microfluidics allowed the entire calmodulin assay to be performed with 200 picomoles of solute.

1 Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, VU Station B 351822, Nashville, TN 37235–1822, USA.
2 Department of Biochemistry, Vanderbilt University School of Medicine, 465 21st Avenue South, Suite 9160 MRBIII, Nashville, TN 37232, USA.
3 Department of Biomedical Engineering and Vanderbilt Institute for Integrative Biosystems Research and Education (VIIBRE), Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37235, USA.
4 Optics and Plasma Research Department, Risø National Laboratory, Technical University of Denmark, Building 128, Frederiksborgvej 399–DK-4000-Roskilde, Denmark.

* To whom correspondence should be addressed. E-mail: darryl.bornhop{at}

The effect of hybridization-induced secondary structure alterations on RNA detection using backscattering interferometry.
N. M. Adams, I. R. Olmsted, F. R. Haselton, D. J. Bornhop, and D. W. Wright (2013)
Nucleic Acids Res. 41, e103
   Abstract »    Full Text »    PDF »
Backscattering Interferometry for Low Sample Consumption Molecular Interaction Screening.
A. Kussrow, C. S. Enders, E. F. Morcos, and D. J. Bornhop (2009)
Journal of Laboratory Automation 14, 341-347
   Abstract »    Full Text »    PDF »

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