x1 = _5mTHF
x2 = THF
x3 = DHF
x4 = _5_10_CH2THF
x5 = _5_10_CHTHF
x6 = _10fTHF
x7 = Ser
x8 = Gly
x9 = dUMP
x10 = GAR
x11 = AICAR
x12 = HCOOH
x13 = NADPH
x14 = Hcy