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Transfert de ligands étudié par spectroscopie infrarouge

 
The binding of diatomic ligands to heme proteins is an integral part of many biological functions such as storage and ligand transport, enzymatic catalysis, and ligand detection. A thorough knowledge of the mechanisms underlying ligand transfer from the heme binding site to the protein exterior is essential for understanding how these proteins accomplish their function : discriminate between ligands, shuttle them from the solvent to the heme pocket or vice versa, and react to external signals. We apply new spectroscopic approaches in the field of infrared femtosecond pulses to the study of internal protein dynamics and, in particular, to ligand transfer dynamics in the active site.

In the case of heme proteins, we explore the vibrational frequency modifications of different ligands (diatomic molecules : CO, NO, O2) in order to probe the ligand evolution during its photo-initiated transfer from one site inside the heme pocket to another. The ligand vibrational frequency depends on its binding site and the associated electron exchange, on the local electric field due to the surrounding amino acids, on the formation of hydrogen bonds with its environment.

Strong Ligand-Protein interactions revealed by ultrafast infrared spectroscopy of CO in the heme pocket of the oxygen sensor FixL 

P. Nuernberger, K. Lee, A. Bonvalet, L. Bouzhir-Sima, J-C Lambry, U. Liebl, M. Joffre, and M. Vos
J. Am. Chem. Soc 2011, 133, 17110-17113 PDF

Direct observation of ligand transfer and bond formation in cytochrome c oxidase using mid-infrared chirped-pulse upconversion
J. Treuffet, K.J. Kubarych, J.-C. Lambry, E. Pilet, J.-B. Masson, J.-L. Martin, M.H. Vos, M. Joffre, A. Alexandrou
Proc. Natl. Acad. Sc. (USA) 104, 15705 (2007) PDF

CO vibration as a probe of ligand dissociation and transfer in myoglobin
T. Polack, J. P. Ogilvie, S. Franzen, M.H. Vos, M. Joffre, J.-L. Martin, A. Alexandrou
Phys. Rev. Lett. 93, 018102(2004) PDF