Primary Event in Vision

Ultrafast Photo-Isomerization Mechanism

Technological applications: associative memory devicesR.R. Birge et.al. J. Phys. Chem. B 1999,103, 10746

Femto-second Spectroscopic Measurements

Boundary C-Cof Lys296

ONIOM QM/MM B3LYP/631G*:Amber

QM Layer (red): 54-atoms

MM Layer (red): 5118-atoms

EONIOM =EMM,full+EQM,red -EEMM,red

Reaction Path: negative-rotation

Energy Storage

Reaction Energy Profile: QM/MM ONIOM-EE (B3LYP/6-31G*:Amber)

*Exp Value :

Dihedral angle

11-cis rhodopsin

all-trans bathorhodopsin

Intermediate conformation

11-cis rhodopsin

all-trans bathorhodopsin

Intermediate conformation

Isomerization Process

C12 C11

N

H2O

Glu113

C13

Superposition of Rhodopsin and Bathorhodopsin in the Binding-Pocket:

Storage of Strain-Energy

Charge-Separation Mechanism

Reorientation of Polarized Bonds

HH

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 ExcitationsONIOM-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

60.3 3.2

54.0 3.4

Time-Sliced Simulations of Quantum Processes

Wu,Y.; Batista, V.S. J. Chem. Phys. 118, 6720 (2003)Wu,Y.; Batista, V.S. J. Chem. Phys. 119, 7606 (2003)Wu,Y.; Batista, V.S. J. Chem. Phys. 121, 1676 (2004)Chen, X., Wu,Y.; Batista, V.S. J. Chem. Phys. 122, 64102 (2005)Wu,Y.; Herman, M.F.; Batista, V.S. J. Chem. Phys. 122, 114114 (2005)Wu,Y.; Batista, V.S. J. Chem. Phys. (2006) 124, 224305Chen, X.; Batista, V.S. J. Chem. Phys. (2006) 125, 124313Chen, X.; Batista, V.S. J. Photochem. Photobiol. 190, 274-282 (2007)

MP/SOFT Method

Trotter Expansion

Bichromatic coherent-control(Weak-field limit)

| k >

| j >

Isomerization coordinate, )cc( 1211

Quantum interference of molecular wavepackets associated with indistinguishable pathways to

the same target state

Time dependent wavepacket undergoing nonadiabatic dynamics at the conical intersection of S1/S0 potential energy surfaces

Chen X, Batista VS; J. Photochem. Photobiol. 190, 274-282 (2007)

Ground vibrational state

First Excited Vibrational State

Bichromatic coherent-control

Pul

se R

elat

ive

Pha

ses

Pulse Relative Intensities

Bichromatic coherent-control

Pul

se R

elat

ive

Pha

ses

Pulse Relative Intensities

Bichromatic coherent-control

Pul

se R

elat

ive

Pha

ses

Flores SC and Batista VS, J. Phys. Chem. B (2004) 108: 6745-6749Gascon JA, Batista VS, Biophys. J. (2004) 87:2931-29411Gascon JA, Sproviero EM, Batista VS, J. Chem. Theor. Comput. (2005) 1:674-685Gascon JA, Sproviero EM, Batista VS, Acc. Chem. Res. (2006) 39, 184-193Chen X and Batista VB, J. Photochem. Photobiol. submitted (2007) 190, 274-282, 2007

The Primary Step in Vision cis/trans isomerization in visual rhodopsin

Empirical model (Domcke, Stock)

Time dependent reactant population

Ptrans(S0

)

Pcis(S1)

‡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, )cc( 1211

Quantum interference of molecular wavepackets associated with indistinguishable pathways to

the same target stateFlores 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 >

| xi >

| xf >

CR =

CR=

Bichirped Coherent Control ScenarioFlores SC; Batista VS, J. Phys. Chem. B (2004) 108: 6745-6749

Chirped Pump Pulses (Wigner transformation forms)

Energy

Reaction coordinate (Stretch. Coord.)

S1

NC:

PC:

Impulsive Stimulated Raman Scattering

Excited State S1

Ground State S0

cis trans

Exact Quantum Dynamics Simulations (t=218 fs, CR=212 fs2)

)fs35FWHM(nm500

Positively Chirped Pulse (PC), strong field

Excited State S1

Ground State S0

cis trans

Exact Quantum Dynamics Simulations (t=218 fs, CR=-146 fs2)

)fs35FWHM(nm500

Negatively Chirped Pulse (NC), strong field

Bichirped Coherent Control Maps (1.2 ps)

Pulse Relative Intensities

Pul

se R

elat

ive

Pha

ses

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%.