title: NO binding kinetics in myoglobin investigated by picosecond Fe K-edge absorption spectroscopy.
abstract: Diatomic ligands in hemoproteins and the way they bind to the active center are central to the protein's function. Using picosecond Fe K-edge X-ray absorption spectroscopy, we probe the NO-heme recombination kinetics with direct sensitivity to the Fe-NO binding after 532-nm photoexcitation of nitrosylmyoglobin (MbNO) in physiological solutions. The transients at 70 and 300 ps are identical, but they deviate from the difference between the static spectra of deoxymyoglobin and MbNO, showing the formation of an intermediate species. We propose the latter to be a six-coordinated domed species that is populated on a timescale of ∼ 200 ps by recombination with NO ligands. This work shows the feasibility of ultrafast pump-probe X-ray spectroscopic studies of proteins in physiological media, delivering insight into the electronic and geometric structure of the active center.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland;
authors.forename: Mahsa
authors.initials: M
authors.lastname: Silatani
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland;
authors.forename: Frederico A
authors.initials: FA
authors.lastname: Lima
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland; SwissFEL, Paul Scherrer Institut, CH-5232 Villigen, Switzerland;
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Penfold
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland;
authors.forename: Jochen
authors.initials: J
authors.lastname: Rittmann
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland;
authors.forename: Marco E
authors.initials: ME
authors.lastname: Reinhard
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland;
authors.forename: Hannelore M
authors.initials: HM
authors.lastname: Rittmann-Frank
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
authors.forename: Camelia
authors.initials: C
authors.lastname: Borca
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Grolimund
authors.affiliation: SwissFEL, Paul Scherrer Institut, CH-5232 Villigen, Switzerland;
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Milne
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide and Lausanne Centre for Ultrafast Science (LACUS), Institut des Sciences et Ingeniérie Chimiques (ISIC), CH-1015 Lausanne, Switzerland; majed.chergui@epfl.ch.
authors.forename: Majed
authors.initials: M
authors.lastname: Chergui
mesh_terms: D007700:Kinetics; D008024:Ligands; D009211:Myoglobin / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D008024:Ligands; D009211:Myoglobin; C031560:myoglobin nitroxide; D009569:Nitric Oxide
keywords: X-ray absorption; ligand binding; nitrosylmyoglobin; picosecond; pump–probe