title: Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion.
abstract: We have implemented the recently demonstrated technique of chirped-pulse upconversion of midinfrared femtosecond pulses into the visible in a visible pump-midinfrared probe experiment for high-resolution, high-sensitivity measurements over a broad spectral range. We have succeeded in time-resolving the CO ligand transfer process from the heme Fe to the neighboring Cu(B) atom in the bimetallic active site of mammalian cytochrome c oxidase, which was known to proceed in <1 ps, using the full CO vibrational signature of Fe-CO bond breaking and Cu(B)-CO bond formation. Our differential transmission results show a delayed onset of the appearance of the Cu(B)-bound species (200 fs), followed by a 450-fs exponential rise. Trajectories calculated by using molecular-dynamics simulations with a Morse potential for the Cu(B)-C interaction display a similar behavior. Both experimental and calculated data strongly suggest a ballistic contribution to the transfer process.
authors: Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Centre National de la Recherche Scientifique and Institut National de la Santé et de la Recherche Médicale U696, 91128 Palaiseau, France.
authors: Johanne
authors: J
authors: Treuffet
authors: Kevin J
authors: KJ
authors: Kubarych
authors: Jean-Christophe
authors: JC
authors: Lambry
authors: Eric
authors: E
authors: Pilet
authors: Jean-Baptiste
authors: JB
authors: Masson
authors: Jean-Louis
authors: JL
authors: Martin
authors: Marten H
authors: MH
authors: Vos
authors: Manuel
authors: M
authors: Joffre
authors: Antigoni
authors: A
authors: Alexandrou
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry; D003198:Computer Simulation; D017666:Deuterium Oxide; D004563:Electrochemistry; D003576:Electron Transport Complex IV / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D006860:Hydrogen Bonding; D007700:Kinetics; D008024:Ligands; D011485:Protein Binding; D013055:Spectrophotometry, Infrared
chemical_list: D008024:Ligands; D006418:Heme; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV; D017666:Deuterium Oxide