Postdoc : Energy transfer in nonlinear quantum lattices : application to the vibrational energy flow in alpha-helices

Location: UTINAM Institute UMR-CNRS 6213

Université de Franche-Comté

25030 Besançon, cedex, FRANCE

Length: 9 months, starting as soon as possible considering the time needed by the person retained to get all the administrative papers necessary to work in France.

Financial conditions: The credits obtained allow us to warrant a gross salary of 1839 ? per month, which in reality means 1508 ? per month transferred on the bank account.

Requested profile: To develop these researches, we are looking for a candidate who has a strong background in either quantum non-linear dynamics, non equilibrium statistical mechanics, transport properties, dissipation, energy localization in molecular system or numerical analysis (i.e. ab initio calculations) applied to condensed or soft matter. In any case, the person retained must have completed his/her PHD since less than 2 years and NOT be of French nationality! Therefore, the applicants should enclose in their application, considerations allowing assessing the time they would need to get the authorization to work in France.

Contact : The applicants should send a detailed CV and a publications list to Dr. POUTHIER Vincent at :

vincent.pouthier@univ-fcomte.fr

Summary of the project:

Since the seminal work of Davydov on bioenergy transport in proteins, both theoretical and experimental evidences suggest that vibrational energy flow in alpha-helices may result from a polaron mechanism. The energy is mediated by the amide-I vibration which delocalizes along the peptide leading to the formation of an exciton called vibron. The vibron strongly interacts with the phonons describing the collective dynamics of the H-bond network. Therefore, its creation induces a lattice distortion and the vibron dressed by this distortion forms the so-called small polaron.

In that context, the project concerns the study of the transport properties of polaron or bi-polaron in a lattice of H bonded peptide units by taking into account on the very short lifetime of the amide-I vibration. Indeed, most of the previous works were based on Hamiltonians that conserve the polaron population. However, in proteins, the amide-I energy relaxation is rather fast and recent experiments have clearly shown that the polaron lifetime is typically of about T1=1.5 ps. The relaxation originates from intramolecular energy redistribution due to the anharmonic coupling between each amide-I mode and a set of intramolecular normal modes whose displacements are strongly localized on the C=O groups. Therefore, the Complex Structure Dynamics group of the UTINAM Institute is looking for a candidate able to develop one of the two following topics :

– Developing analytical models/calculations to study the transport properties in a finite site helix within a time convolutionless approach to account on the strong non markovian dynamics that arises from the discrete nature of the phonon energy spectrum.

– Performing ab initio calculations to characterize the detailed relaxation pathways responsible for the energy relaxation of the amide-I mode in a model helix. These calculations will give rise to a theoretical model to represent the bath of intramolecular normal modes responsible for energy relaxation.

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Dr. POUTHIER Vincent

Chargé de Recherche CNRS

Institut UTINAM UMR CNRS 6213

25030 BESANCON cedex

tel. 33 3 81 66 64 77