{ diff(x1, t) = 0,
  diff(x2, t) = (1*k27*k19*k17/k18*(k28/k8)^k2/(1 + (k28/k8)^k2) + (-1)*k27*k20*k17/k18*(x3/k9)^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10))/((x3/k9)^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10)) + (1 + (x4/k12)^k14)/(1 + k13^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10))*(x4/k12)^k14)))/k27,
  diff(x4, t) = (1*k27*k20*k17/k18*(x3/k9)^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10))/((x3/k9)^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10)) + (1 + (x4/k12)^k14)/(1 + k13^(k15 - (k15 - k16)*x4/k10/(1 + x4/k10))*(x4/k12)^k14)) + (-1)*k27*k21*k17/k18*(x4/k10 - x5*x6/(k23*k24*k25))/(1 + x4/k10 + x6/k24 + x5*x6/(k23*k24)))/k27,
  diff(x7, t) = (2*k27*k21*k17/k18*(x4/k10 - x5*x6/(k23*k24*k25))/(1 + x4/k10 + x6/k24 + x5*x6/(k23*k24)) + (-1)*k27*k22*k17/k18*x5/(k11 + x5))/k27 }