1. Spin cascade and doming in ferric hemes: Femtosecond X-ray absorption and X-ray emission studies
- Author
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Georgios Pamfilidis, Dmitry Khakhulin, Christian Bressler, Gregor Knopp, Claudio Cirelli, Jakub Szlachetko, Jérémy R. Rouxel, Mykola Biednov, Frederico A. Lima, Rebecca A. Ingle, Philip J. M. Johnson, Camila Bacellar, Christopher Arrell, Angel Rodriguez-Fernandez, Wojciech Gawelda, Oliviero Cannelli, Majed Chergui, Samuel Menzi, Dominik Kinschel, Katharina Kubicek, Giulia F. Mancini, and Christopher J. Milne
- Subjects
inorganic chemicals ,ferric hemoproteins ,spectroscopy ,Hemeprotein ,ultrafast ,Iron ,Doming ,x-ray spectroscopy ,spin states ,Photochemistry ,nitric-oxide-binding ,cytochrome-c ,Ferrous ,chemistry.chemical_compound ,Protein Domains ,medicine ,Humans ,Respiratory function ,Heme ,doming ,Multidisciplinary ,biology ,vibrational-relaxation ,Chemistry ,Nitric oxide binding ,Cytochrome c ,carbon-monoxide ,resolved resonance raman ,low-temperature ,Cytochromes c ,Spectrometry, X-Ray Emission ,dynamics ,electron-transfer ,Kinetics ,X-Ray Absorption Spectroscopy ,myoglobin recombination ,biology.protein ,Commentary ,Ferric ,medicine.drug - 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 K-alpha and K-beta 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.
- Published
- 2020