The model contains one compartment called C. There are three species called S1, S2 and S3 and three parameters called k1, k2 and p1. Species S1 is labeled as an SBML boundary species. The model contains two reactions defined as:

Reaction Rate
S1 + S2 → S3 k1 · S1 · S2 · C
S3 → S1 + S2 k2 · S3 · C

The model contains one initialAssignment:

Variable Formula
S1 p1 · 2

Note: SBML's InitialAssignment construct override any declared initial values. In this case the initial value declared for species S1 is inconsistent with the value returned by the InitialAssignment.

The initial conditions are as follows:

Value Units
Initial amount of S1 1.0 × 10−3 mole
Initial amount of S2 2.0 × 10−3 mole
Initial amount of S3 1.0 × 10−3 mole
Value of parameter k1 0.75 litre mole-1 second-1
Value of parameter k2 0.25 second-1
Value of parameter p1 1.25 × 10−4 mole
Volume of compartment C 1 litre

The species values are given as amounts of substance to make it easier to use the model in a discrete stochastic simulator, but (as per usual SBML principles) they must be treated as concentrations where they appear in expressions.

Note: The test data for this model was generated from an analytical solution of the system of equations.