Ground-state heterogeneity and vibrational energy redistribution in bacterial phytochrome observed with femtosecond 2D IR spectroscopy

Manoop Chenchiliyan, Joachim Kübel, Saik Ann Ooi, Giacomo Salvadori, Benedetta Mennucci, Sebastian Westenhoff, Michał Maj

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Phytochromes belong to a group of photoreceptor proteins containing a covalently bound biliverdin chromophore that inter-converts between two isomeric forms upon photoexcitation. The existence and stability of the photocycle products are largely determined by the protein sequence and the presence of conserved hydrogen-bonding interactions in the vicinity of the chromophore. The vibrational signatures of biliverdin, however, are often weak and obscured under more intense protein bands, limiting spectroscopic studies of its non-transient signals. In this study, we apply isotope-labeling techniques to isolate the vibrational bands from the protein-bound chromophore of the bacterial phytochrome from Deinococcus radiodurans. We elucidate the structure and ultrafast dynamics of the chromophore with 2D infra-red (IR) spectroscopy and molecular dynamics simulations. The carbonyl stretch vibrations of the pyrrole rings show the heterogeneous distribution of hydrogen-bonding structures, which exhibit distinct ultrafast relaxation dynamics. Moreover, we resolve a previously undetected 1678 cm-1 band that is strongly coupled to the A- and D-ring of biliverdin and demonstrate the presence of complex vibrational redistribution pathways between the biliverdin modes with relaxation-assisted measurements of 2D IR cross peaks. In summary, we expect 2D IR spectroscopy to be useful in explaining how point mutations in the protein sequence affect the hydrogen-bonding structure around the chromophore and consequently its ability to photoisomerize to the light-activated states.

Original languageEnglish
Article number085103
JournalJournal of Chemical Physics
Volume158
Issue number8
DOIs
StatePublished - 28 Feb 2023
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2023 Author(s).

Fingerprint

Dive into the research topics of 'Ground-state heterogeneity and vibrational energy redistribution in bacterial phytochrome observed with femtosecond 2D IR spectroscopy'. Together they form a unique fingerprint.

Cite this