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Spin cascade and doming in ferric hemes: Femtosecond X-ray absorption and X-ray emission studies

Bacellar, C; Kinschel, D; Mancini, GF; Ingle, RA; Rouxel, J; Cannelli, O; Cirelli, C; ... Chergui, M; + view all (2020) Spin cascade and doming in ferric hemes: Femtosecond X-ray absorption and X-ray emission studies. Proceedings of the National Academy of Sciences of the United States of America (PNAS) 10.1073/pnas.2009490117. Green open access

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Abstract

The structure-function relationship is at the heart of biology, and major protein deformations are correlated to specific functions. For ferrous heme proteins, doming is associated with the respiratory function in hemoglobin and myoglobins. Cytochrome c (Cyt c) has evolved to become an important electron-transfer protein in humans. In its ferrous form, it undergoes ligand release and doming upon photoexcitation, but its ferric form does not release the distal ligand, while the return to the ground state has been attributed to thermal relaxation. Here, by combining femtosecond Fe Kα and Kβ X-ray emission spectroscopy (XES) with Fe K-edge X-ray absorption near-edge structure (XANES), we demonstrate that the photocycle of ferric Cyt c is entirely due to a cascade among excited spin states of the iron ion, causing the ferric heme to undergo doming, which we identify. We also argue that this pattern is common to a wide diversity of ferric heme proteins, raising the question of the biological relevance of doming in such proteins.

Type: Article
Title: Spin cascade and doming in ferric hemes: Femtosecond X-ray absorption and X-ray emission studies
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1073/pnas.2009490117
Publisher version: https://doi.org/10.1073/pnas.2009490117
Language: English
Additional information: This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Keywords: X-ray spectroscopy, doming, ferric hemoproteins, spin states, ultrafast
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10109185
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