Constraints in Odesolve to solve Enzymatic Reaction ODEs

Forum|Forum|7 years ago
April 5, 2019
7 replies
3563 views

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!

1_Glucose-to-Ethanol-Enzymeatic-Reaction.zip

V

ValeryOchkov

24-Ruby IV

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?

A

AlanStevens

19-Tanzanite

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

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-MFra-

21-Topaz II

Hi,

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

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-MFra-

21-Topaz II

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.

T

terryhendicott