The model contains one compartment called "compartment". There are two species named S1 and S2 and two parameters named k1 and k2. The model contains two reactions defined as:

Reaction Rate
S1 → S2 k1 · S1 · compartment
S2 → S1 k2 · S2 · compartment

The rate constants are identical in both directions, leading to a system where the species concentrations remain the same.

The initial conditions are as follows:

Value Units
Initial amount of S1 1.5 × 10−3 mole
Initial amount of S2 1.5 × 10−3 mole
Value of parameter k1 0.5 second-1
Value of parameter k2 0.5 second-1
Volume of compartment "compartment" 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) their symbols represent their values in concentration units where they appear in expressions.

Stochastic simulations will show fluctuations in the amounts of the species substances, but the total amount should not vary nor should the average concentration vary significantly over time.

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