{ diff(x1, t) = (1*k16*k1*x1 + (-1)*k16*(k2*x2*x1 + k3*x1*x1))/k16,
  diff(x2, t) = (1*k16*(k4 + k6*x2*x1) + (-1)*k16*(k5*x2 + k7*k2*x2*x1 + k15*k14*x5*x2))/k16,
  diff(x3, t) = (1*k16*k8*x1 + (-1)*k16*k9*x3)/k16,
  diff(x4, t) = (1*k16*k10 + (-1)*k16*k11*x4)/k16,
  diff(x5, t) = (1*k16*k12*x4 + (-1)*k16*(k13*x5 + k14*x5*x2))/k16 }