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Mid-infrared picosecond pump-dump-probe and pump-repump-probe experiments to resolve a ground-state intermediate in cyanobacterial phytochrome Cph1.
J Phys Chem B. 2009 Dec 24; 113(51):16354-64.JP

Abstract

Multipulse picosecond mid-infrared spectroscopy has been used to study photochemical reactions of the cyanobacterial phytochrome photoreceptor Cph1. Different photophysical schemes have been discussed in the literature to describe the pathways after photoexcitation, particularly, to identify reaction phases that are linked to photoisomerisation and electronic decay in the 1566-1772 cm(-1) region that probes C=C and C=O stretching modes of the tetrapyrrole chromophore. Here, multipulse spectroscopy is employed, where, compared to conventional visible pump-mid-infrared probe spectroscopy, an additional visible pulse is incorporated that interacts with populations that are evolving on the excited- and ground-state potential energy surfaces. The time delays between the pump and the dump pulse are chosen such that the dump pulse interacts with different phases in the reaction process. The pump and dump pulses are at the same wavelength, 640 nm, and are resonant with the Pr ground state as well as with the excited state and intermediates. Because the dump pulse additionally pumps the remaining, partially recovered, and partially oriented ground-state population, theory is developed for estimating the fraction of excited-state molecules. The calculations take into account the model-dependent ground-state recovery fraction, the angular dependence of the population transfer resulting from the finite bleach that occurs with linearly polarized intense femtosecond optical excitation, and the partially oriented population for the dump field. Distinct differences between the results from the experiments that use a 1 or a 14 ps dump time favor a branching evolution from S1 to an excited state or reconfigured chromophore and to a newly identified ground-state intermediate (GSI). Optical dumping at 1 ps shows the instantaneous induced absorption of a delocalized C=C stretching mode at 1608 cm(-1), where the increased cross section is associated with the electronic ground-state structure of the ZZZ configuration of the linear tetrapyrrole chromophore. The dump-induced absorption decays with time constants of 5 and 19 ps to the Pr ground state. Employing a dump pulse at 14 ps results in an instantaneous decrease of the absorption of the 1608 cm(-1) band, indicating repumping of the GSI. The dump-induced absorption recovers back to the GSI with a 6 ps lifetime. A spectral similarity is observed between the 6 ps phase in the dump experiment and the 3 ps component found in the two-pulse pump-probe measurement. Combined with the dominance of ground-state absorption bands in the dump-induced spectrum, this indicates the presence of a GSI, which is additionally characterized by previously unidentified induced absorption at 1710 and 1570-80 cm(-1). The metastable photoproduct Lumi-R, which is in the electronic ground state and populated at 500 ps after excitation of Pr, is highly efficiently repumped into the Pr ground state with the power density used. After repumping, Lumi-R is not recovered on the 500 ps time scale of the experiment and is distinct from the GSI of Pr since it is not associated with its characteristic induced absorption at 1710 and 1570-80 cm(-1).

Authors+Show Affiliations

Division of Molecular Biosciences, Faculty of Natural Sciences, South Kensington Campus, Imperial College London, London SW7 2AZ, UK.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

19950906

Citation

van Wilderen, Luuk J G W., et al. "Mid-infrared Picosecond Pump-dump-probe and Pump-repump-probe Experiments to Resolve a Ground-state Intermediate in Cyanobacterial Phytochrome Cph1." The Journal of Physical Chemistry. B, vol. 113, no. 51, 2009, pp. 16354-64.
van Wilderen LJ, Clark IP, Towrie M, et al. Mid-infrared picosecond pump-dump-probe and pump-repump-probe experiments to resolve a ground-state intermediate in cyanobacterial phytochrome Cph1. J Phys Chem B. 2009;113(51):16354-64.
van Wilderen, L. J., Clark, I. P., Towrie, M., & van Thor, J. J. (2009). Mid-infrared picosecond pump-dump-probe and pump-repump-probe experiments to resolve a ground-state intermediate in cyanobacterial phytochrome Cph1. The Journal of Physical Chemistry. B, 113(51), 16354-64. https://doi.org/10.1021/jp9038539
van Wilderen LJ, et al. Mid-infrared Picosecond Pump-dump-probe and Pump-repump-probe Experiments to Resolve a Ground-state Intermediate in Cyanobacterial Phytochrome Cph1. J Phys Chem B. 2009 Dec 24;113(51):16354-64. PubMed PMID: 19950906.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Mid-infrared picosecond pump-dump-probe and pump-repump-probe experiments to resolve a ground-state intermediate in cyanobacterial phytochrome Cph1. AU - van Wilderen,Luuk J G W, AU - Clark,Ian P, AU - Towrie,Michael, AU - van Thor,Jasper J, PY - 2009/12/3/entrez PY - 2009/12/3/pubmed PY - 2010/2/19/medline SP - 16354 EP - 64 JF - The journal of physical chemistry. B JO - J Phys Chem B VL - 113 IS - 51 N2 - Multipulse picosecond mid-infrared spectroscopy has been used to study photochemical reactions of the cyanobacterial phytochrome photoreceptor Cph1. Different photophysical schemes have been discussed in the literature to describe the pathways after photoexcitation, particularly, to identify reaction phases that are linked to photoisomerisation and electronic decay in the 1566-1772 cm(-1) region that probes C=C and C=O stretching modes of the tetrapyrrole chromophore. Here, multipulse spectroscopy is employed, where, compared to conventional visible pump-mid-infrared probe spectroscopy, an additional visible pulse is incorporated that interacts with populations that are evolving on the excited- and ground-state potential energy surfaces. The time delays between the pump and the dump pulse are chosen such that the dump pulse interacts with different phases in the reaction process. The pump and dump pulses are at the same wavelength, 640 nm, and are resonant with the Pr ground state as well as with the excited state and intermediates. Because the dump pulse additionally pumps the remaining, partially recovered, and partially oriented ground-state population, theory is developed for estimating the fraction of excited-state molecules. The calculations take into account the model-dependent ground-state recovery fraction, the angular dependence of the population transfer resulting from the finite bleach that occurs with linearly polarized intense femtosecond optical excitation, and the partially oriented population for the dump field. Distinct differences between the results from the experiments that use a 1 or a 14 ps dump time favor a branching evolution from S1 to an excited state or reconfigured chromophore and to a newly identified ground-state intermediate (GSI). Optical dumping at 1 ps shows the instantaneous induced absorption of a delocalized C=C stretching mode at 1608 cm(-1), where the increased cross section is associated with the electronic ground-state structure of the ZZZ configuration of the linear tetrapyrrole chromophore. The dump-induced absorption decays with time constants of 5 and 19 ps to the Pr ground state. Employing a dump pulse at 14 ps results in an instantaneous decrease of the absorption of the 1608 cm(-1) band, indicating repumping of the GSI. The dump-induced absorption recovers back to the GSI with a 6 ps lifetime. A spectral similarity is observed between the 6 ps phase in the dump experiment and the 3 ps component found in the two-pulse pump-probe measurement. Combined with the dominance of ground-state absorption bands in the dump-induced spectrum, this indicates the presence of a GSI, which is additionally characterized by previously unidentified induced absorption at 1710 and 1570-80 cm(-1). The metastable photoproduct Lumi-R, which is in the electronic ground state and populated at 500 ps after excitation of Pr, is highly efficiently repumped into the Pr ground state with the power density used. After repumping, Lumi-R is not recovered on the 500 ps time scale of the experiment and is distinct from the GSI of Pr since it is not associated with its characteristic induced absorption at 1710 and 1570-80 cm(-1). SN - 1520-5207 UR - https://www.unboundmedicine.com/medline/citation/19950906/Mid_infrared_picosecond_pump_dump_probe_and_pump_repump_probe_experiments_to_resolve_a_ground_state_intermediate_in_cyanobacterial_phytochrome_Cph1_ L2 - https://doi.org/10.1021/jp9038539 DB - PRIME DP - Unbound Medicine ER -