title: Observing heme doming in myoglobin with femtosecond X-ray absorption spectroscopy.
abstract: 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.
authors.affiliation: Department of Physics and Chemistry, University of Palermo , Viale delle Scienze, 90128 Palermo, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Levantino
authors.affiliation: LCLS, SLAC National Accelerator Laboratory , Menlo Park, California 94025, USA.
authors.forename: H T
authors.initials: HT
authors.lastname: Lemke
authors.affiliation: CNRS - Institut de Biologie Structurale , Grenoble 38044, France.
authors.forename: G
authors.initials: G
authors.lastname: Schirò
authors.affiliation: LCLS, SLAC National Accelerator Laboratory , Menlo Park, California 94025, USA.
authors.forename: M
authors.initials: M
authors.lastname: Glownia
authors.affiliation: Department of Physics and Chemistry, University of Palermo , Viale delle Scienze, 90128 Palermo, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Cupane
authors.affiliation: Department of Physics , UMR UR1-CNRS 6251, University of Rennes 1 , Rennes, France.
authors.forename: M
authors.initials: M
authors.lastname: Cammarata