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Ground state isomerization of a model green fluorescent protein chromophore
Author(s) -
He Xiang,
Bell Alasdair F.,
Tonge Peter J.
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)00761-0
Subject(s) - isomerization , protonation , chromophore , cationic polymerization , chemistry , photochemistry , fluorescence , ground state , population , catalysis , organic chemistry , physics , atomic physics , ion , demography , quantum mechanics , sociology
The relationship between ground state cis – trans isomerization and protonation state is explored for a model green fluorescent protein chromophore, 4‐hydroxybenzylidene‐1,2‐dimethylimidazolinone (HBDI). We find that the protonation state has only a modest effect on the free energy differences between cis and trans isomers and on the activation energies for isomerization. Specifically, the experimental free energy differences are 3.3, 8.8, and 9.6 kJ/mol for cationic, neutral, and anionic forms of HBDI, respectively, and the activation energies are 48.9, 54.8, and 54.8 kJ/mol for cationic, neutral, and anionic forms, respectively. Furthermore, these activation energies are much smaller than might be expected based on comparison with similar systems. These results suggest that there may be a sub‐population of the chromophore, which is nearly equally accessible to all three protonation states, through which thermal isomerization may proceed.