Speaker: Jeremy Gunawardena (Harvard University, Cambridge)
Date: 28/11/2024
Time: 10:00 CEST
Host: Rosa Martinez-Corral (Barcelona Collaboratorium & Centre de Regulació Genòmica, Barcelona)
Cellular systems - enzymes, motors, allosteric proteins, genes, ion channels, receptors, etc - are often described by the functional dependence of some output property on the concentrations of input factors, with the system itself described as a Markov process. Such input-output functions are calculated by a variety of methods with apparently few common features. In fact, this typical biological heterogeneity conceals a remarkable underlying mathematical unity. All such input-output functions are rational functions of their inputs, whose coefficients are themselves rational functions of the Markov transition rates. There is a uniform procedure for calculating each function in terms of the linear-framework graph associated to the Markov process. Furthermore, input-output functions exhibit a Hopfield barrier: if the Markov process can reach thermodynamic equilibrium, then the degree of the rational function depends only on the numbers of input binding sites and is otherwise model independent. Hopfield barriers offer a powerful method for assessing energy expenditure in cellular systems, which does not require fitting models to data.
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