Optimal control design of laser pulses for mode specific vibrational excitation in an enzyme–substrate complex

High level combined quantum mechanics/molecular mechanics (QM/MM) methods are used to calculate the potential energy and dipole moment surfaces for the motion of the labile proton in an intermediate in the catalytic cycle of aromatic amine dehydrogenase (AADH). Quantum tunnelling is important in transfer of this tryptamine proton. Optimal control theory is used here to design laser pulses to excite the labile proton from its lowest to selected vibrationally excited states. Such pulses leading to excitation of specific vibrational modes might in future be useful to promote reactivity by enhancing proton tunnelling; we discuss practical difficulties in carrying this out.