Observing heme doming in myoglobin with femtosecond X-ray absorption spectroscopya)

M. Levantino (1) , H. T. Lemke (2) , Giorgio Schirò (3) , M. Glownia (2) , A. Cupane (1) , Marco Cammarata (4)

1 Department of Physics - University of Palermo
2 SLAC - SLAC National Accelerator Laboratory
3 IBS - UMR 5075 - Institut de biologie structurale
4 IPR - Institut de Physique de Rennes

We report time-resolved X-ray absorption measurements after photolysis of carbonmonoxy myoglobin performed at the LCLS X-ray free electron laser with nearly 100 fs (FWHM) time resolution. Data at the Fe K-edge reveal that the photoinduced structural changes at the heme occur in two steps, with a faster (∼70 fs) relaxation preceding a slower (∼400 fs) one. We tentatively attribute the first relaxation to a structural rearrangement induced by photolysis involving essentially only the heme chromophore and the second relaxation to a residual Fe motion out of the heme plane that is coupled to the displacement of myoglobin F-helix

Keywords: Photodissociation; Time resolved spectroscopy; X-ray absorption near edge structure; X-ray absorption spectra; X-ray optics

Domains: Physics [physics]; Life Sciences [q-bio]; Biochemistry, Molecular Biology; Structural Biology [q-bio.BM]

M. Levantino, H. T. Lemke, Giorgio Schirò, M. Glownia, A. Cupane, et al.. Observing heme doming in myoglobin with femtosecond X-ray absorption spectroscopya). Structural Dynamics, 2015, 2 (4), pp.041713. ⟨10.1063/1.4921907⟩. ⟨hal-01168333⟩