Semiclassical approach for all-atom
nonadiabatic simulations of excitation
energy transfer processes in
photosynthetic complexes
Young Min Rhee
Department of Chemistry
POSTECH
(Pohang University of Science and Technology)
Quantum coherence in photosynthesis
Debates, debates, debates, …
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Detailed look?
Theoretical approaches!
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Classes of theoretical approaches

Class I

constant H
+ abstract
model bath
Class II
more realistic
H, but ground
state-like bath

Class III
bath relaxation
upon electronic
changes
H.W. Kim; A. Kelly; J.W. Park; YMR, JACS 134, 11640 (2012)
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Importance of the model consistency

What if the potential is switched for
better accuracy?
 Potential exaggeration in l

One potential model should be adopted all the
time
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Classes of theoretical approaches

Class I
constant H
+ abstract
model bath
http://singlet.postech.ac.kr

Class II
more realistic
H but ground
state-like bath

Class III
bath relaxation
upon electronic
changes
Young Min Rhee, 2013
Classes of theoretical approaches

Class I
constant H
+ abstract
model bath
http://singlet.postech.ac.kr

Class II
more realistic
H but ground
state-like bath

Class III
bath relaxation
upon electronic
changes
Young Min Rhee, 2013
Modeling for the chromophore complex
Diagonals: force-field approach
 Off-diagonals: transition charge electrostatic
potential (TrESP) [Madjet et al. JPCB 110, 17268 (2006)]
 Fluctuations with all-atom interaction

http://singlet.postech.ac.kr
Young Min Rhee, 2013
Modeling for the chromophore complex

Electronic structure theory
 Direct passage toward studying dynamics
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Can this be reliable?
 Decent to good agreement!
http://singlet.postech.ac.kr
Young Min Rhee, 2013
All atom  Semiclassical approach
H. Kim; A. Nassimi; R. Kapral, JCP 129, 084102 (2008)
A. Kelly; YMR, JPCL 2, 808 (2011)
Partial
Wigner transform
mapping formalism
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Semiclassical approach: PBME

Mapping approach: N quantum states
 N fictitious harmonic oscillator
 Dynamics of electronic states
: Dynamics of (r, p)
with Hamiltonian
Modeling
efforts
(Classical-looking)
Newton-like mechanics toward multiple
surface dynamics!
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Confinement versus electrostatics

Mutation study
Wild type
ALA-mutant
Electrostatic mutant
H.W. Kim; A. Kelly; J.W. Park; YMR, JACS 134, 11640 (2012)

Confinement dominates over electrostatics
for FMO
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Nature of initial state

When started
from
non-oscillatory
initial state
Still becomes
oscillatory
after ~20 fs
http://singlet.postech.ac.kr
Fluctuation “kicks”
stationary into
oscillatory
Young Min Rhee, 2013
Vibrational effects?
With silenced
chromophore vibration
With active
chromophore vibration
No coherence???
Classical nature: exaggeration of vibrational effect
(faster decoherence)
H.W. Kim; A. Kelly; J.W. Park; YMR, JACS 134, 11640 (2012)
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Ensemble versus single molecules

Each is
coherent in
its own
manner
Coherent even
with classical
vibrations
http://singlet.postech.ac.kr
“Rigid”
protein keeps
coherence
Young Min Rhee, 2013
Future prospects

Better QCLE than PBME?





Semi-classical but yet classical
Zero-point energy leaking
Currently, horrible when states are largely
separated
Better potential for more reliable
modeling?
Different systems with QM effects?
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Conclusions


All-atom level insight: POSSIBLE!!!
Rigid nature of protein




Chromophore alignment maintenance
Coherent coupling
Fidelity in photosynthesis?
Flexible nature of protein


Coupling fluctuation
Diversity?
H.W. Kim; A. Kelly; J.W. Park; YMR, JACS 134, 11640 (2012)
http://singlet.postech.ac.kr
Young Min Rhee, 2013
Acknowledgements






Aaron Kelly: PBME
Hyun Woo Kim: MD interface
Jae Woo Park: IM/MM
Sun Mi Choi
Weon-Gyu Lee
Chang Woo Kim

Postech (equipment)
KOSEF / KRF / IBS (\$)
KISTI (CPU time)
Q-Chem

And YOU!!!



http://singlet.postech.ac.kr
Young Min Rhee, 2013