On the sum of chemical reactions

Abstract

It is standard in chemistry to represent a sequence of reactions by a single overall reaction, often called a complex reaction in contrast to an elementary reaction. Photosynthesis $6 \text{CO}_2+6 \text{H}_2\text{O} \longrightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6 \text{O}_2$ is an example of such complex reaction. We introduce a mathematical operation that corresponds to summing two chemical reactions. Specifically, we define an associative and non-communicative operation on the product space ${\mathbb{N}}_0^n\times {\mathbb{N}}_0^n$ (representing the reactant and the product of a chemical reaction, respectively). The operation models the overall effect of two reactions happening in succession, one after the other. We study the algebraic properties of the operation and apply the results to stochastic reaction networks (RNs), in particular to reachability of states, and to reduction of RNs.

Maintenance of steady-state mRNA levels by a microRNA-based feed forward loop in the presence of stochastic gene expression noise

“…Usually, studies concerning the distribution of a protein/RNA treat the amount of molecules as a discrete quantity [6,23,48], yet it can be treated as a continuous variable [11,14]. We will use a hybrid model, which allows to study the IFFL as a process with random production jumps and deterministic decay [24,25,35].…”