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Science 334 (6054): 321-322

Copyright © 2011 by the American Association for the Advancement of Science

Every Bit Counts

Peter J. Thomas

The term "signal transduction" has been in use for over 40 years, originating in biological studies of cellular photoreceptors and chemotaxis, and elaborated through discoveries of signaling systems such as the protein kinases (1). In engineering, "signaling" has a precise meaning that defines the notion of "information" (2), and quantifies the capabilities of a signaling system in terms of its channel capacity, measured in bits (3). Despite the attractive analogy, a number of obstacles have thwarted attempts to apply information theory quantitatively to cellular signal transduction networks. On page 354 of this issue, Cheong et al. (4) succeed in doing so, making rigorous and quantitative measurements of information capacities in a biochemical signaling system.

Departments of Mathematics, Biology, and Cognitive Science, Case Western Reserve University, Cleveland, OH 44106, USA.

E-mail: pjthomas{at}

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