title: How input noise limits biochemical sensing in ultrasensitive systems.
abstract: Many biological processes are regulated by molecular devices that respond in an ultrasensitive fashion to upstream signals. An important question is whether such ultrasensitivity improves or limits its ability to read out the (noisy) input stimuli. Here, we develop a simple model to study the statistical properties of ultrasensitive signaling systems. We demonstrate that the output sensory noise is always bounded, in contrast to earlier theories using the small noise approximation, which tends to overestimate the impact of noise in ultrasensitive pathways. Our analysis also shows that the apparent sensitivity of the system is ultimately constrained by the input signal-to-noise ratio. Thus, ultrasensitivity can improve the precision of biochemical sensing only to a finite extent. This corresponds to a new limit for ultrasensitive signaling systems, which is strictly tighter than the Berg-Purcell limit.
authors.affiliation: IBM T.J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Hu
authors.affiliation: Center for Theoretical Biological Physics, University of California San Diego, La Jolla, California 92093-0319, USA.
authors.forename: Wouter-Jan
authors.initials: WJ
authors.lastname: Rappel
authors.affiliation: Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA.
authors.forename: Herbert
authors.initials: H
authors.lastname: Levine
mesh_terms: D001669:Biochemical Phenomena; D008954:Models, Biological; D016012:Poisson Distribution; D059629:Signal-To-Noise Ratio