Indicate species boundary condition
BoundaryCondition property indicates
whether a species object has a boundary condition.
BoundaryCondition of a species is
the species quantity is modified by reactions, rules, events, and
doses. If the
the species quantity is modified by rules, events, and doses, but
not by reactions.
you want the species to participate in a reaction, but do not want
any reactions to modify its quantity.
All SimBiology® species are state variables regardless of
Consider the following two use cases of boundary conditions:
Modeling receptor-ligand interactions that affect
the rate of change of the receptor but not the ligand. For example,
in response to hormone, steroid receptors such as the glucocorticoid
receptor (GR) translocate from the cytoplasm (
to the nucleus (
nuc). The hsp90/ hsp70 chaperone
complex directs this nuclear translocation [Pratt 2004]. The natural ligand for GR is
cortisol; the synthetic hormone dexamethasone (
is used in place of cortisol in experimental systems. In this system
dexamethasone participates in the reaction but the quantity of dexamethasone
in the cell is regulated using a rule. To simply model translocation
of GR you could use the following reactions:
Formation of the chaperone-receptor complex,
Hsp90_complex + GR_cyt -> Hsp90_complex:GR_cyt
In response to the synthetic hormone dexamethasone (
GR moves from the cytoplasm to the nucleus.
Hsp90_complex:GR_cyt + dex -> Hsp90_complex + GR_nuc + dex
BoundaryCondition = true; ConstantAmount = false
dexis modeled as a boundary condition with a rule to regulate the rate of change of
dexin the system. Here, the quantity of
dexis not determined by the rate of the second reaction but by a rate rule such as
ddex/dt = 0.001
dex = 0.001
Modeling the role of nucleotides (for example, GTP, ATP, cAMP) and cofactors (for example, Ca++, NAD+, coenzyme A). Consider the role of GTP in the activation of Ras by receptor tyrosine kinases.
Ras-GDP + GTP -> Ras-GTP + GDP
For GTP, BoundaryCondition = true; ConstantAmount = true
Model GTP and GDP with boundary conditions, thus making them boundary
species. In addition, you can set the
of these species to
true to indicate that their
quantity does not vary during a simulation.
|Applies to||Object: species|
This example illustrates how to use the
of a species so that the species amount is not modified by the reaction
it participates in, but by a user-defined dose object.
Load a sample project.
A SimBiology model named
m1 is loaded to
the MATLAB Workspace. The model is a simple radioactive decay model
in which two species (
are modified by the following reaction.
SimBiology Reaction Array Index: Reaction: 1 x -> z
Simulate the model and view results before adding any boundary conditions.
[t,x,names] = sbiosimulate(m1); plot(t,x); legend(names) xlabel('Time'); ylabel('Amount');
RepeatDose object to the model
and specify the species to be dosed, dose amount, dose schedule, and
d1 = adddose(m1,'d1','repeat'); set(d1,'TargetName','z','Amount',100.0,'Interval',1.0,'RepeatCount',8); set(d1,'TimeUnits','second','AmountUnits','molecule');
BoundaryCondition of species
be true so that the species will be modified by the dose object
but not by the reaction.
Simulate the model by applying the dose object.
[t2,x2,names] = sbiosimulate(m1,d1);
Plot the results. Notice that the amount of species
now modified by the repeated dose object, but not by the reaction.
[t2,x2,names] = sbiosimulate(m1,d1); plot(t2,x2); legend(names); xlabel('Time'); ylabel('Amount');
Pratt, W.B., Galigniana, M.D., Morishima, Y., Murphy, P.J. (2004), Role of molecular chaperones in steroid receptor action, Essays Biochem, 40:41-58.