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Science 318 (5851): 757-758

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

A Clock with a Flip Switch

Andy C. Poon and James E. Ferrell Jr.,

The heart of circadian timekeeping in cyanobacteria is a toggle switch that controls the periodic phosphorylation of a key circuit protein.

The authors are in the Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA. E-mail: james.ferrell{at}

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Science Signaling. ISSN 1937-9145 (online), 1945-0877 (print). Pre-2008: Science's STKE. ISSN 1525-8882