J. (João) Rodrigues

Address: Environment and Energy Section, Instituto Superior Técnico, Lisboa
Phone: (00351) 21 841 94 40
Email: joao.rodrigues@ist.utl.pt
Specialization: Thermodynamics & Ecological Economics
Project: Dynamics of synthesising units

Dynamics of synthesising units

A Synthetizing Unit (SU) is an enzyme whose dynamics generalize classical enzyme kinetics. An SU binds arriving substrate molecules and after a production time it releases product molecules. The most important aspect of the dynamics of the SU is how the production flux relates to the arrival fluxes. Kooijman (1998) and subsequent papers have worked out the dynamics of the SU in a number of important cases, such as: The aim of this project is to generalize as much as possible the previous results and to explore the effects of different parameters in the dynamics of SUs. Hence, once particular goal would be write a closed-form expression for the production flux of an SU, processing an arbitrary number of partially substitutable substrates. Another particular goal would be to charaterize rigorously the role of spatial strucutre in the dynamics of an SU (that is, how an arrival flux to a set of SU's relates to the arrival flux to each SU). The last particular goal would be to write a closed-form expression for the production fluxes of a general network of SUs, where the production fluxes of number of different SUs can be the arrival fluxes of other SUs.

The results of this project would be important in two different contexts of the DEB theory, the ones where SUs appear. One would be in assimilation: how the stock of reserves of an organism responds to the availability of resources. The function that relates the abundance of resources to the change in abundance of an organism is known as functional response. A small set of functional responses is commonly used (Holling type I, II and III with perfect complementary or perfect substitutability). SU dynamics has all these functional responses as a particular case but can give rise to other functional responses, when partial substitutability is considered.

The other context for which the results of the present project might be useful is the mobilization of reserves. According to the DEB theory, this mobilization is a first order process on the density of reserves, but these dynamics are derived axiomatically, hence from phenomenological. It would be an important development for the theory to identify the mechanisms that lead to this dynamics, where mechanisms are the decision rules undertaken by SUs on the basis of local information.