To ensure protein positivity (i.e. $p > 0$), you must check positivity for $f$.
Indeed, $p = \mu \rho f \odot \tau(f)$ (see Dourado et al. 2023).
In all your models, reactions are irreversible and necessarily $f > 0$. So the only problem you should have is $f$ values getting close to zero or being slightly negative.
Can you create a small notebook to show me how you get negative protein values?
To ensure protein positivity (i.e. $p > 0$), you must check positivity for $f$. Indeed, $p = \mu \rho f \odot \tau(f)$ (see Dourado et al. 2023).
In all your models, reactions are irreversible and necessarily $f > 0$. So the only problem you should have is $f$ values getting close to zero or being slightly negative.
Can you create a small notebook to show me how you get negative protein values?