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Femtosecond X-ray emission study of the spin cross-over dynamics in haem proteins

Lookup NU author(s): Professor Thomas Penfold



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


In haemoglobin the change from the low-spin (LS) hexacoordinated haem to the high spin (HS, S = 2) pentacoordinated domed deoxy-myoglobin (deoxyMb) form upon ligand detachment from the haem and the reverse process upon ligand binding are what ultimately drives the respiratory function. Here we probe them in the case of Myoglobin-NO (MbNO) using element- and spin-sensitive femtosecond Fe Kα and Kβ X-ray emission spectroscopy at an X-ray free-electron laser (FEL). We find that the change from the LS (S = 1/2) MbNO to the HS haem occurs in ~800 fs, and that it proceeds via an intermediate (S = 1) spin state. We also show that upon NO recombination, the return to the planar MbNO ground state is an electronic relaxation from HS to LS taking place in ~30ps. Thus, the entire ligand dissociation-recombination cycle in MbNO is a spin cross-over followed by a reverse spin cross-over process.

Publication metadata

Author(s): Kinschel D, Bacellar C, Cannelli O, Sorokin B, Katayama T, Mancini G, Rouxel J, Obara Y, Nishitani J, Ito H, Ito T, Kurahashi N, Higashimura C, Kudo S, Keane T, Lima F, Gawelda W, Zalden P, Schulz S, Budarz J, Khakhulin D, Galler A, Bressler C, Milne C, Penfold T, Yabashi M, Suzuki T, Misawa K, Chergui M

Publication type: Article

Publication status: Published

Journal: Nature Communications

Year: 2020

Volume: 11

Print publication date: 20/08/2020

Online publication date: 18/08/2020

Acceptance date: 21/07/2020

Date deposited: 20/08/2020

ISSN (electronic): 2041-1723

Publisher: Nature Publishing Group


DOI: 10.1038/s41467-020-17923-w


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Funder referenceFunder name
RPG-2016-103Leverhulme Trust, The