x1 = ERKc
x2 = pERKc
x3 = ppERKc
x4 = ERK_ppMEKc
x5 = pERK_ppMEKc
x6 = DUSPc
x7 = pERK_DUSPc
x8 = ppERK_DUSPc
x9 = ERKn
x10 = pERKn
x11 = ppERKn
x12 = pERK_DUSPn
x13 = ppERK_DUSPn
x14 = STYXn
x15 = ERK_STYXn
x16 = pERK_STYXn
x17 = ppERK_STYXn
x18 = duspn
x19 = DUSPn
x20 = u_ppMEKc_tot
x21 = ppMEKc_tot
x22 = ERKc_obs
x23 = pERKc_obs
x24 = ppERKc_obs
x25 = ERK_ppMEKc_obs