\frac{dx_{1}}{dt} = \left(1 \cdot \left(1 - x_{4}\right) \cdot \left(k_{1} \cdot x_{2} \cdot \frac{1}{2}^{4} / x_{2} \cdot \frac{1}{2} + k_{7}^{4} + k_{10}\right) \cdot x_{3} + -1 \cdot k_{2} \cdot x_{1} \cdot \frac{1}{100}^{2} / \left(x_{1} \cdot \frac{1}{100}^{2} + k_{8}^{2}\right)\right) / k_{12}\\ \frac{dx_{2}}{dt} = \left(1 \cdot k_{3} \cdot \left(1 - k_{9} / \left(x_{1} \cdot \frac{1}{100} + k_{9}\right) \cdot 1 / \left(1 + k_{11}\right)\right) + -1 \cdot k_{4} \cdot x_{2} \cdot \frac{1}{2}\right) / k_{12}\\ \frac{dx_{3}}{dt} = \left(-1 \cdot \left(1 - x_{4}\right) \cdot \left(k_{1} \cdot x_{2} \cdot \frac{1}{2}^{4} / x_{2} \cdot \frac{1}{2} + k_{7}^{4} + k_{10}\right) \cdot x_{3} + 1 \cdot k_{2} \cdot x_{1} \cdot \frac{1}{100}^{2} / \left(x_{1} \cdot \frac{1}{100}^{2} + k_{8}^{2}\right)\right) / k_{13}\\ \frac{dx_{4}}{dt} = \left(1 \cdot k_{5} \cdot x_{1} \cdot \frac{1}{100}^{4} \cdot \left(1 - x_{4}\right) + -1 \cdot k_{6}\right) / k_{12}