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 CuB-CO bond formation. Our differential transmission results show a delayed onset of the appearance of the CuB-bound species (200 fs), followed by a 450-fs exponential rise. Trajectories calculated by using molecular-dynamics simulations with a Morse potential for the CuB-C interaction display a similar behavior. Both experimental and calculated data strongly suggest a ballistic contribution to the transfer process. Cop. 2007 by The National Academy of Sciences of the USA.
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Johanne Treuffet, Kevin Kubarych, Jean-Christophe Lambry, Eric Pilet, Jean-Baptiste Masson, et al.. Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion. Proceedings of the National Academy of Sciences of the United States of America , National Academy of Sciences, 2007, 104 (40), pp.15705. ⟨10.1073/pnas.0703279104⟩. ⟨hal-00821499⟩

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