PMID- 31621314
OWN - NLM
STAT- MEDLINE
DCOM- 20201027
LR  - 20201027
IS  - 1520-5126 (Electronic)
IS  - 0002-7863 (Linking)
VI  - 141
IP  - 45
DP  - 2019 Nov 13
TI  - First-Principles Characterization of the Elusive I Fluorescent State and the 
      Structural Evolution of Retinal Protonated Schiff Base in Bacteriorhodopsin.
PG  - 18193-18203
LID - 10.1021/jacs.9b08941 [doi]
AB  - The conversion of light energy into work is essential to life on earth. 
      Bacteriorhodopsin (bR), a light-activated proton pump in Archae, has served for 
      many years as a model system for the study of this process in photoactive 
      proteins. Upon absorption of a photon, its chromophore, the retinal protonated 
      Schiff base (RPSB), isomerizes from its native all-trans form to a 13-cis form 
      and pumps a proton out of the cell in a process that is coupled to eventual ATP 
      synthesis. Despite numerous time-resolved spectroscopic studies over the years, 
      the details of the photodynamics of bR on the excited state, particularly the 
      characterization of the I fluorescent state, the time-resolved reaction 
      mechanism, and the role of the counterion cluster of RPSB, remain uncertain. 
      Here, we use ab initio multiple spawning (AIMS) with spin-restricted ensemble 
      Kohn-Sham (REKS) theory to simulate the nonadiabatic dynamics of the ultrafast 
      photoreaction in bR. The excited state dynamics can be partitioned into three 
      distinct phases: (1) relaxation away from the Franck-Condon region dominated by 
      changes in retinal bond length alternation, (2) dwell time on the excited state 
      in the I fluorescent state featuring an untwisted, bond length inverted RPSB, and 
      (3) rapid torsional evolution to the conical intersection after overcoming a 
      small excited state barrier. We fully characterize the I fluorescent state and 
      the excited state barrier that hinders direct evolution to the conical 
      intersection following photoexcitation. We also find that photoisomerization is 
      accompanied by weakening of the interaction between RPSB and its counterion 
      cluster. However, in contradiction with a recent time-resolved X-ray experiment, 
      hydrogen bond cleavage is not necessary to reproduce the observed 
      photoisomerization dynamics.
FAU - Yu, Jimmy K
AU  - Yu JK
AD  - Department of Chemistry and The PULSE Institute , Stanford University , Stanford 
      , California 94305 , United States.
AD  - Biophysics Program , Stanford University , Stanford , California 94305 , United 
      States.
AD  - SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , 
      California 94025 , United States.
FAU - Liang, Ruibin
AU  - Liang R
AUID- ORCID: 0000-0001-8741-1520
AD  - Department of Chemistry and The PULSE Institute , Stanford University , Stanford 
      , California 94305 , United States.
AD  - SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , 
      California 94025 , United States.
FAU - Liu, Fang
AU  - Liu F
AUID- ORCID: 0000-0003-1322-4997
AD  - Department of Chemical Engineering , Massachusetts Institute of Technology , 
      Cambridge , Massachusetts 02138 , United States.
FAU - Martinez, Todd J
AU  - Martinez TJ
AUID- ORCID: 0000-0002-4798-8947
AD  - Department of Chemistry and The PULSE Institute , Stanford University , Stanford 
      , California 94305 , United States.
AD  - Biophysics Program , Stanford University , Stanford , California 94305 , United 
      States.
AD  - SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , 
      California 94025 , United States.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
DEP - 20191104
PL  - United States
TA  - J Am Chem Soc
JT  - Journal of the American Chemical Society
JID - 7503056
RN  - 0 (Schiff Bases)
RN  - 53026-44-1 (Bacteriorhodopsins)
RN  - RR725D715M (Retinaldehyde)
SB  - IM
MH  - Bacteriorhodopsins/*chemistry/radiation effects
MH  - Density Functional Theory
MH  - Fluorescence
MH  - Halobacterium salinarum/chemistry
MH  - Light
MH  - Models, Chemical
MH  - Models, Molecular
MH  - Retinaldehyde/*analogs & derivatives/radiation effects
MH  - Schiff Bases/*chemistry/radiation effects
EDAT- 2019/10/18 06:00
MHDA- 2020/10/28 06:00
CRDT- 2019/10/18 06:00
PHST- 2019/10/18 06:00 [pubmed]
PHST- 2020/10/28 06:00 [medline]
PHST- 2019/10/18 06:00 [entrez]
AID - 10.1021/jacs.9b08941 [doi]
PST - ppublish
SO  - J Am Chem Soc. 2019 Nov 13;141(45):18193-18203. doi: 10.1021/jacs.9b08941. Epub 
      2019 Nov 4.