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Published July 15, 2006 | public
Journal Article

A Fluctuation Method to Quantify In Vivo Fluorescence Data


Quantitative in vivo measurements are essential for developing a predictive understanding of cellular behavior. Here we present a technique that converts observed fluorescence intensities into numbers of molecules. By transiently expressing a fluorescently tagged protein and then following its dilution during growth and division, we observe asymmetric partitioning of fluorescence between daughter cells at each division. Such partition asymmetries are set by the actual numbers of proteins present, and thus provide a means to quantify fluorescence levels. We present a Bayesian algorithm that infers from such data both the fluorescence conversion factor and an estimate of the measurement error. Our algorithm works for arbitrarily sized data sets and handles consistently any missing measurements. We verify the algorithm with extensive simulation and demonstrate its application to experimental data from Escherichia coli. Our technique should provide a quantitative internal calibration to systems biology studies of both synthetic and endogenous cellular networks.

Additional Information

© 2006 The Biophysical Society. Published by Elsevier Inc. Received 22 August 2005, Accepted 19 April 2006, Available online 6 January 2009. We thank Derek Bowie, Robert Sidney Cox III, Jon Young, and the anonymous referees for useful comments. M.B.E. acknowledges a CASI award from the Burroughs Wellcome Fund and the Searle Scholars Program. U.A. and M.B.E. are supported by the Human Frontiers Science Program. P.S.S. is supported by the National Sciences and Engineering Research Council (Canada) and by a Tier II Canada Research Chair.

Additional details

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