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Title: Internal conversion of the anionic GFP chromophore: in and out of the I-twisted S 1 /S 0 conical intersection seam

Abstract

The functional diversity of the green fluorescent protein (GFP) family is intimately connected to the interplay between competing photo-induced transformations of the chromophore motif, anionic p-hydroxybenzylidene-2,3-dimethylimidazolinone (HBDI-). Its ability to undergo Z/E-isomerization is of particular importance for super-resolution microscopy and emerging opportunities in optogenetics. Yet, key dynamical features of the underlying internal conversion process in the native HBDI- chromophore remain largely elusive. We investigate the intrinsic excited-state behavior of isolated HBDI- to resolve competing decay pathways and map out the factors governing efficiency and the stereochemical outcome of photoisomerization. Based on non-adiabatic dynamics simulations, we demonstrate that non-selective progress along the two bridge-torsional (i.e., phenolate, P, or imidazolinone, I) pathways accounts for the three decay constants reported experimentally, leading to competing ultrafast relaxation primarily along the I-twisted pathway and S1 trapping along the P-torsion. The majority of the population (~70%) is transferred to S0 in the vicinity of two approximately enantiomeric minima on the I-twisted intersection seam (MECI-Is). Despite their sloped, reactant-biased topographies (suggesting low photoproduct yields), we find that decay through these intersections leads to products with a surprisingly high quantum yield of ~30%. This demonstrates that E-isomer generation results at least in part from direct isomerization on themore » excited state. A photoisomerization committor analysis reveals a difference in intrinsic photoreactivity of the two MECI-Is and that the observed photoisomerization is the combined result of two effects: early, non-statistical dynamics around the less reactive intersection followed by later, near-statistical behavior around the more reactive MECI-I. Our work offers new insight into internal conversion of HBDI- that both establishes the intrinsic properties of the chromophore and enlightens principles for the design of chromophore derivatives and protein variants with improved photoswitching properties.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Department of Chemistry and the PULSE Institute, Stanford University, Stanford, CA 94305, USA, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
Publication Date:
Research Org.:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Villum Foundation
OSTI Identifier:
1834650
Alternate Identifier(s):
OSTI ID: 1838671
Grant/Contract Number:  
AC02-76SF00515; VKR023371
Resource Type:
Published Article
Journal Name:
Chemical Science
Additional Journal Information:
Journal Name: Chemical Science Journal Volume: 13 Journal Issue: 2; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry (RSC)
Country of Publication:
United Kingdom
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

List, Nanna H., Jones, Chey M., and Martínez, Todd J. Internal conversion of the anionic GFP chromophore: in and out of the I-twisted S 1 /S 0 conical intersection seam. United Kingdom: N. p., 2022. Web. doi:10.1039/D1SC05849E.
List, Nanna H., Jones, Chey M., & Martínez, Todd J. Internal conversion of the anionic GFP chromophore: in and out of the I-twisted S 1 /S 0 conical intersection seam. United Kingdom. https://doi.org/10.1039/D1SC05849E
List, Nanna H., Jones, Chey M., and Martínez, Todd J. Wed . "Internal conversion of the anionic GFP chromophore: in and out of the I-twisted S 1 /S 0 conical intersection seam". United Kingdom. https://doi.org/10.1039/D1SC05849E.
@article{osti_1834650,
title = {Internal conversion of the anionic GFP chromophore: in and out of the I-twisted S 1 /S 0 conical intersection seam},
author = {List, Nanna H. and Jones, Chey M. and Martínez, Todd J.},
abstractNote = {The functional diversity of the green fluorescent protein (GFP) family is intimately connected to the interplay between competing photo-induced transformations of the chromophore motif, anionic p-hydroxybenzylidene-2,3-dimethylimidazolinone (HBDI-). Its ability to undergo Z/E-isomerization is of particular importance for super-resolution microscopy and emerging opportunities in optogenetics. Yet, key dynamical features of the underlying internal conversion process in the native HBDI- chromophore remain largely elusive. We investigate the intrinsic excited-state behavior of isolated HBDI- to resolve competing decay pathways and map out the factors governing efficiency and the stereochemical outcome of photoisomerization. Based on non-adiabatic dynamics simulations, we demonstrate that non-selective progress along the two bridge-torsional (i.e., phenolate, P, or imidazolinone, I) pathways accounts for the three decay constants reported experimentally, leading to competing ultrafast relaxation primarily along the I-twisted pathway and S1 trapping along the P-torsion. The majority of the population (~70%) is transferred to S0 in the vicinity of two approximately enantiomeric minima on the I-twisted intersection seam (MECI-Is). Despite their sloped, reactant-biased topographies (suggesting low photoproduct yields), we find that decay through these intersections leads to products with a surprisingly high quantum yield of ~30%. This demonstrates that E-isomer generation results at least in part from direct isomerization on the excited state. A photoisomerization committor analysis reveals a difference in intrinsic photoreactivity of the two MECI-Is and that the observed photoisomerization is the combined result of two effects: early, non-statistical dynamics around the less reactive intersection followed by later, near-statistical behavior around the more reactive MECI-I. Our work offers new insight into internal conversion of HBDI- that both establishes the intrinsic properties of the chromophore and enlightens principles for the design of chromophore derivatives and protein variants with improved photoswitching properties.},
doi = {10.1039/D1SC05849E},
journal = {Chemical Science},
number = 2,
volume = 13,
place = {United Kingdom},
year = {Wed Jan 05 00:00:00 EST 2022},
month = {Wed Jan 05 00:00:00 EST 2022}
}

Journal Article:
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https://doi.org/10.1039/D1SC05849E

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