### Switches and clocks in molecular cell biology

9 November 2007

John Tyson

Department of Biology

Virginia Polytechnic Institute & State University

#### Abstract

Molecular switches and clocks play major roles in cellular control systems, such as cell growth and division, programmed cell death, signalling networks, development and motility. Switches and clocks derive from positive and negative feedback in molecular reaction networks. Because the behavior of complex networks of switches and clocks can be difficult to understand or predict by intuition alone, some systems biologists have tried to model these networks with nonlinear differential equations (reaction kinetic equations). I will describe some thorny issues that arise in this arena. What is an appropriate level of detail for a kinetic model? How should one convert deterministic models to stochastic models? What are the origins of bistability and oscillations in nonlinear dynamical systems? Can we reduce the complexity of mathematical models without sacrificing accuracy or expressive power?

#### References

A Ciliberto, F Capuani, J J Tyson, *"Modeling networks of coupled enzymatic reactions using the total quasi-steady state approximation"*, PLoS Comput Biol 3:e45 2007. doi:10.1371/journal.pcbi.0030045

M Sabouri-Ghomi, A Ciliberto, S Kar, B Nowak, J J Tyson, *"Antagonism and bistability in protein interaction networks"*, J Theor Biol, in press, doi:10.1016/j.jtbi.2007.09.001

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