Time course of RNA calculated by our developed model for (A) T7 RNAP concentrations varying from 0.05 to 0.8 μM, (B) NTP concentrations varying from 0.4 to 4.0 mM, and (C) Mg(OAc)2 concentrations varying from 1 to 20 mM. Unless otherwise stated, the initial values of other concentrations were [RNA] = 0, [PPi4−] = 0, [ATP4−] = 0.8 mM, [GTP4−] = 0.8 mM, [CTP4−] = 0.8 mM, [UTP4−] = 0.8 mM, [H+] = 25 mM, [T7 RNAP] = 0.1 μM, and [Mg2+] = 8 mM.