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Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore.
J Am Chem Soc. 2011 Mar 09; 133(9):2932-43.JA

Abstract

Initiated by excited-state intramolecular proton transfer (ESIPT) reaction, an overall reaction cycle of 4-(2-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (o-HBDI), an analogue of the core chromophore of the green fluorescent protein (GFP), has been investigated. In contrast to the native GFP core, 4-(4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (p-HBDI), which requires hydrogen-bonding relay to accomplish proton transfer in vivo, o-HBDI possesses a seven-membered-ring intramolecular hydrogen bond and thus provides an ideal system for mimicking an intrinsic proton-transfer reaction. Upon excitation, ESIPT takes place in o-HBDI, resulting in a ∼600 nm proton-transfer tautomer emission. The o-HBDI tautomer emission, resolved by fluorescence upconversion, is comprised of an instantaneous rise to a few hundred femtosecond oscillation in the early relaxation stage. Frequency analysis derived from ultrashort pulse gives two low-frequency vibrations at 115 and 236 cm(-1), corresponding to skeletal deformation motions associated with the hydrogen bond. The results further conclude that ESIPT in o-HBDI is essentially triggered by low-frequency motions and may be barrierless along the reaction coordinate. Femtosecond UV/vis transient absorption spectra also provide supplementary evidence for the structural evolution during the reaction. In CH(3)CN, an instant rise of a 530 nm transient is resolved, which then undergoes 7.8 ps decay, accompanied by the growth of a rather long-lived 580 nm transient species. It is thus concluded that following ESIPT the cis-proton transfer isomer undergoes cis-trans-isomerization. The results of viscosity-dependent dynamics are in favor of the one-bond-flip mechanism, which is in contrast to the volume-conserving isomerization behavior for cis-stilbene and p-HBDI. Further confirmation is given by the picosecond-femtosecond transient IR absorption spectra, where several new and long-lived IR bands in the range of 1400-1500 cm(-1) are assigned to the phenyl in-plane breathing motions of the trans-proton transfer tautomer. Monitored by the nanosecond transient absorption, the 580 nm transient undergoes a ∼7.7 μs decay constant, accompanied by the growth of a new ∼500 nm band. The latter is assigned to a deprotonated tautomer species, which then undergoes the ground-state reverse proton recombination to the original o-HBDI in ∼50 μs, achieving an overall, reversible proton transfer cycle. This assignment is unambiguously supported by pump-probe laser induced fluorescence studies. On these standpoints, a comparison of photophysical properties among o-HBDI, p-HBDI, and wild-type GFP is discussed in detail.

Authors+Show Affiliations

Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan, R.O.C.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21323314

Citation

Hsieh, Cheng-Chih, et al. "Comprehensive Studies On an Overall Proton Transfer Cycle of the Ortho-green Fluorescent Protein Chromophore." Journal of the American Chemical Society, vol. 133, no. 9, 2011, pp. 2932-43.
Hsieh CC, Chou PT, Shih CW, et al. Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore. J Am Chem Soc. 2011;133(9):2932-43.
Hsieh, C. C., Chou, P. T., Shih, C. W., Chuang, W. T., Chung, M. W., Lee, J., & Joo, T. (2011). Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore. Journal of the American Chemical Society, 133(9), 2932-43. https://doi.org/10.1021/ja107945m
Hsieh CC, et al. Comprehensive Studies On an Overall Proton Transfer Cycle of the Ortho-green Fluorescent Protein Chromophore. J Am Chem Soc. 2011 Mar 9;133(9):2932-43. PubMed PMID: 21323314.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Comprehensive studies on an overall proton transfer cycle of the ortho-green fluorescent protein chromophore. AU - Hsieh,Cheng-Chih, AU - Chou,Pi-Tai, AU - Shih,Chun-Wei, AU - Chuang,Wei-Ti, AU - Chung,Min-Wen, AU - Lee,Junghwa, AU - Joo,Taiha, Y1 - 2011/02/16/ PY - 2011/2/18/entrez PY - 2011/2/18/pubmed PY - 2011/6/18/medline SP - 2932 EP - 43 JF - Journal of the American Chemical Society JO - J. Am. Chem. Soc. VL - 133 IS - 9 N2 - Initiated by excited-state intramolecular proton transfer (ESIPT) reaction, an overall reaction cycle of 4-(2-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (o-HBDI), an analogue of the core chromophore of the green fluorescent protein (GFP), has been investigated. In contrast to the native GFP core, 4-(4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one (p-HBDI), which requires hydrogen-bonding relay to accomplish proton transfer in vivo, o-HBDI possesses a seven-membered-ring intramolecular hydrogen bond and thus provides an ideal system for mimicking an intrinsic proton-transfer reaction. Upon excitation, ESIPT takes place in o-HBDI, resulting in a ∼600 nm proton-transfer tautomer emission. The o-HBDI tautomer emission, resolved by fluorescence upconversion, is comprised of an instantaneous rise to a few hundred femtosecond oscillation in the early relaxation stage. Frequency analysis derived from ultrashort pulse gives two low-frequency vibrations at 115 and 236 cm(-1), corresponding to skeletal deformation motions associated with the hydrogen bond. The results further conclude that ESIPT in o-HBDI is essentially triggered by low-frequency motions and may be barrierless along the reaction coordinate. Femtosecond UV/vis transient absorption spectra also provide supplementary evidence for the structural evolution during the reaction. In CH(3)CN, an instant rise of a 530 nm transient is resolved, which then undergoes 7.8 ps decay, accompanied by the growth of a rather long-lived 580 nm transient species. It is thus concluded that following ESIPT the cis-proton transfer isomer undergoes cis-trans-isomerization. The results of viscosity-dependent dynamics are in favor of the one-bond-flip mechanism, which is in contrast to the volume-conserving isomerization behavior for cis-stilbene and p-HBDI. Further confirmation is given by the picosecond-femtosecond transient IR absorption spectra, where several new and long-lived IR bands in the range of 1400-1500 cm(-1) are assigned to the phenyl in-plane breathing motions of the trans-proton transfer tautomer. Monitored by the nanosecond transient absorption, the 580 nm transient undergoes a ∼7.7 μs decay constant, accompanied by the growth of a new ∼500 nm band. The latter is assigned to a deprotonated tautomer species, which then undergoes the ground-state reverse proton recombination to the original o-HBDI in ∼50 μs, achieving an overall, reversible proton transfer cycle. This assignment is unambiguously supported by pump-probe laser induced fluorescence studies. On these standpoints, a comparison of photophysical properties among o-HBDI, p-HBDI, and wild-type GFP is discussed in detail. SN - 1520-5126 UR - https://www.unboundmedicine.com/medline/citation/21323314/Comprehensive_studies_on_an_overall_proton_transfer_cycle_of_the_ortho_green_fluorescent_protein_chromophore_ L2 - https://dx.doi.org/10.1021/ja107945m DB - PRIME DP - Unbound Medicine ER -