期刊
CHEMICAL SCIENCE
卷 13, 期 2, 页码 373-385出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/d1sc05849e
关键词
-
资金
- AMOS program of the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, and Biosciences Division
- Villum Foundation [VKR023371]
- NSF
The study investigates the inherent excited-state behavior of the HBDI- chromophore, resolving competitive decay pathways and factors influencing efficiency and stereochemical outcomes. The research offers new insights into the internal conversion of HBDI- and provides principles for designing chromophore derivatives with improved photoswitching properties.
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 S-1 trapping along the P-torsion. The majority of the population (similar to 70%) is transferred to S-0 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 similar to 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.
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