Primary Event in Vision. Ultrafast Photo-Isomerization Mechanism.
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Transcript of Primary Event in Vision. Ultrafast Photo-Isomerization Mechanism.
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Primary Event in Vision
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Ultrafast Photo-Isomerization Mechanism
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Technological applications: associative memory devicesR.R. Birge et.al. J. Phys. Chem. B 1999,103, 10746
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Femto-second Spectroscopic Measurements
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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
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Reaction Path: negative-rotation
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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
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11-cis rhodopsin
all-trans bathorhodopsin
Intermediate conformation
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Isomerization Process
C12 C11
N
H2O
Glu113
C13
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Superposition of Rhodopsin and Bathorhodopsin in the Binding-Pocket:
Storage of Strain-Energy
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Charge-Separation Mechanism
Reorientation of Polarized Bonds
HH
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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%
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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
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Time-Sliced Simulations of Quantum Processes
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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
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Bichromatic coherent-control(Weak-field limit)
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| k >
| j >
Isomerization coordinate, )cc( 1211
Quantum interference of molecular wavepackets associated with indistinguishable pathways to
the same target state
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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)
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Ground vibrational state
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First Excited Vibrational State
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Bichromatic coherent-control
Pul
se R
elat
ive
Pha
ses
Pulse Relative Intensities
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Bichromatic coherent-control
Pul
se R
elat
ive
Pha
ses
Pulse Relative Intensities
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Bichromatic coherent-control
Pul
se R
elat
ive
Pha
ses
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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
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Empirical model (Domcke, Stock)
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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
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| 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)
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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 >
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CR =
CR=
Bichirped Coherent Control ScenarioFlores SC; Batista VS, J. Phys. Chem. B (2004) 108: 6745-6749
Chirped Pump Pulses (Wigner transformation forms)
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Energy
Reaction coordinate (Stretch. Coord.)
S1
NC:
PC:
Impulsive Stimulated Raman Scattering
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Excited State S1
Ground State S0
cis trans
Exact Quantum Dynamics Simulations (t=218 fs, CR=212 fs2)
)fs35FWHM(nm500
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Positively Chirped Pulse (PC), strong field
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Excited State S1
Ground State S0
cis trans
Exact Quantum Dynamics Simulations (t=218 fs, CR=-146 fs2)
)fs35FWHM(nm500
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Negatively Chirped Pulse (NC), strong field
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Bichirped Coherent Control Maps (1.2 ps)
Pulse Relative Intensities
Pul
se R
elat
ive
Pha
ses
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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.
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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
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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%.