Superposition of Rhodopsin and Bathorhodopsin in the Binding-Pocket: Storage of Strain-Energy
Charge-Separation Mechanism Reorientation of Polarized Bonds H H
Energy Storage[QM/MM ONIOM-EE (B3LYP/6-31G*:Amber)] Energy Storage[QM/MM ONIOM-ME(B3LYP/6-31G*:Amber)] - Electrostatic Contribution of Individual Residues Electrostatic Contribution to the Total Energy Storage 62%
TD-DFT Electronic Excitations ONIOM-EE (TD-B3LYP/6-31G*:Amber) E rhod. E TD-B3LYP//B3LYP/6-31G*:Amber CASPT2//CASSCF/6-31G*:Amber E batho. Experimental Values in kcal/mol 63.5 64.1 57.4 60.33.2 54.03.4
Time dependent reactant population P trans (S 0 ) P cis (S 1 ) Chen X, Batista VS; J. Photochem. Photobiol. submitted (2007) * Flores SC and Batista VS, J. Phys. Chem. B (2004) 108: 6745-6749 MP/SOFT TDSCF * Time, fs 0.67
| k > | j > Isomerization coordinate, Quantum interference of molecular wavepackets associated with indistinguishable pathways to the same target state Flores SC; Batista VS, J. Phys. Chem. B 108: 6745-6749 (2004) Batista VS; Brumer P, Phys. Rev. Lett. 89, 143201 (2002)
Quantum interference of indistinguishable pathways to the same target state x O. Nairz, M. Arndt and A. Zeilinger Am. J. Phys. 71, 319 (2003) | j > | k > | x i > | x f >
CR = Bichirped Coherent Control Scenario Flores SC; Batista VS, J. Phys. Chem. B (2004) 108: 6745-6749 Chirped Pump Pulses (Wigner transformation forms)
Energy Reaction coordinate (Stretch. Coord.) S1S1 NC : PC : Impulsive Stimulated Raman Scattering
Excited State S1 Ground State S0 cistrans Exact Quantum Dynamics Simulations (t=218 fs, CR=212 fs 2 )
Conclusions We have shown that the photoisomerization of rhodopsin can be controlled by changing the coherence properties of the initial state in accord with a coherent control scenario that entails two femtosecond chirped pulses. We have shown that the underlying physics involves controlling the dynamics of a subcomponent of the system (the photoinduced rotation along the C11-C12 bond) in the presence of intrinsic decoherence induced by the vibronic activity. Control over 5-10% product yields should be possible, despite the ultrafast intrinsic decoherence phenomena, providing results of broad theoretical and experimental interest.
Conclusions We have shown that the ONIOM-EE (B3LYP/6-31G*:Amber) level of theory, in conjunction with high-resolution structural data, predicts the energy storage through isomerization, in agreement with experiments. We have shown that structural distortions account for 40% of the energy stored, while the remaining 60 % is electrostatic energy due to stretching of the salt-bridge between the protonated Schiff-base and the Glu113 counterion. We have shown that the salt-bridge stretching mechanism involves reorientation of polarized bonds due to torsion of the polyene chain at the linkage to Lys296, without displacing the linkage relative to Glu113 or redistributing charges within the chromophore
Conclusions (cont.) We have demonstrated that a hydrogen-bonded water molecule, consistently found by X-ray crystallographic studies, can assist the salt- bridge stretching process by stabilizing the reorientation of polarized bonds. We have shown that the absence of Wat2b, however, does not alter the overall structural rearrangements and increases the total energy storage in 1 kcal/mol. We have demonstrated that the predominant electrostatic contributions to the total energy storage result from the interaction of the protonated Schiff-based retinyl chromophore with four surrounding polar residues and a hydrogen bonded water molecule. We have shown that the ONIOM-EE (TD-B3LYP/6- 31G*:Amber//B3LYP/6-31G:Amber) level of theory, predicts vertical excitation energy shifts in quantitative agreement with experiments, while the individual excitations of rhodopsin and bathorhodopsin are overestimated by 10%.