cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Showing results for 
Search instead for 
Did you mean: 

Community Tip - When posting, your subject should be specific and summarize your question. Here are some additional tips on asking a great question. X

Constraints in Odesolve to solve Enzymatic Reaction ODEs

fields54
4-Participant

Constraints in Odesolve to solve Enzymatic Reaction ODEs

I'm modeling glucose conversion to ethanol through solving a series of ODEs of enzymatic reactions. How do I set the constraint that all concentrations are >= 0 and the total mass of all compounds in the pathway are constant over time. Any help would be greatly appreciated!

8 REPLIES 8

1. I think you have an error in the formulas, if you get a negative concentration.
2. I recommend that you go to Mathcad Prime - where differential equations are solved with units
3. I recommend the book Chemical Kinetics with Mathcad and Maple
4. Do you design moonshine?

 

Your reaction rates are extremely fast!  The value of Glu drops to zero within a value of x of about 6.5*10^-4, yet you are looking for results over values of x out to 200.  The ODE solvers can't cope with this!

 

I suggest:

1.  Solve Glu on its own (as it is independent of the others) to x around 6.5*10^-4; Then set it to zero beyond this.

2.  Solve the others to the same limited time (distance?), then use their results at this time as initial conditions for subsequent solutions.  

I didn't check the time constants of anything other than that for Glu, so you might have to repeat step 2 if the end time is still too large for the ODE solvers to cope.

 

Alan

 

-MFra-
21-Topaz II
(To:AlanStevens)

Hi,

In fact the first equation (First order, Type II: y = f (y ')) can be solved in parametric form:

Glu.jpg

-MFra-
21-Topaz II
(To:-MFra-)

Obviously the result coincides with that obtained using "odesolve" for the single differential equation y '= f (y) with the necessary initial conditions. The result is then used by the system of differential equations without the previous equation. But there are still negative concentrations.

Hi,

Are you sure you have the conversion of hour and seconds the right way round?

 

Capture.PNG

-MFra-
21-Topaz II
(To:fields54)

Glu2.jpg

-MFra-
21-Topaz II
(To:fields54)

Hi,

I did a simulation with initial constants chosen by me and similar values between them:

Glu4.jpg

Top Tags