Laboratoire Francis PERRIN
URA CNRS-CEA 2453
This website is no more mainteined. See LIDYL or NIMBE
The GOUTTELIUM setup : an IR spectroscopy in a cold environment
Last Update: 29 July 2014

Etude du photorécepteur "Photoactive Yellow Protein" par dichroïsme circulaire femtoseconde
Last Update: 21 February 2016

L'interaction médicament-protéine étudié par spectroscopie de fluorescence résolue en temps
Last Update: 9 December 2013

"Cœur silicium - coquille carbone" pour batteries Li-Ion
Last Update: 6 October 2015

Dynamic of peptids in gas phase and photostability of proteins

Many complex molecular systems absorb light in the UV spectral range, including those of paramount biological importance, like DNA bases or proteins. The excited states created by UV absorption are endowed with mechanisms of deactivation which are of major importance for the photochemical stability of these species. The majority of these processes are ultrafast and provide a rapid and efficient way to dissipate the electronic energy into vibration, thus avoiding photochemical reactions.

In proteins, for instance, absorption in the near UV range is mainly due to the aromatic side chain of the tryptophan, tyrosine and phenylalanine amino acids and both spectroscopic and dynamic properties of these chromophores generally depend on their immediate environment, i.e., on the local conformation of the protein. In this context, synergetic theoretical/experimental studies of gas phase model peptides as proteins building blocks should lead to better understanding the photophysical phenomena involved in the relaxation mechanisms of proteins. Such an approach has been developed by a collaboration between the SBM team of LFP (CEA-CNRS URA2453), a theoretical team of the Ruđer Bošković Institut (Zagreb, Croatia) and two experimentalists  of  CLUPS (Paris Sud University, Orsay) in order to characterize the excited states of the stable conformers of a model peptide and establish the nonradiative relaxation mechanisms.1

 

Sophisticated laser spectroscopic gas phase techniques developed recently in the SBM team and at CLUPS combining laser-desorption,  supersonic expansion and IR-UV double resonance and UV-UV pump-probe techniques can provide conformation-selective data with a great deal of resolution; in particular the structure of each conformer thanks to their IR spectra, their transitions adiabatic energies, the lifetimes of their first excited state. In this spirit, dynamics relaxation of the first excited state of a capped peptide containing the phenylalanine amino acid, the N-acetylphenylalaninylamide (NAPA) which present three stable conformers (A, B and C) in the ground state2 have been investigated in the nanosecond regime at CEA and in the picosecond regime at CLUPS.

The measured lifetimes of the first excited state of the three conformers vary from 1 to 70 ns and depend strongly on the conformation of the peptide. In addition, the isotopic substitution of the hydrogen atoms of the NH and NH2 groups gives supplementary information on their involvement in the relaxation processes. Owing to the size of the system, their flexibility, the existence of non-covalent interactions which governs structures and the nature of the first excited states (locally excited as well as charge transfer states), the theoretical investigation of the relaxation mechanisms of the first excited states requires the use of sophisticated models.

 

A double-step approach has been developed: (i) exploration of the potential energy surfaces of the first excited states of the conformers with a non-adiabatic dynamic using the time dependent density functional theory (NA-TDDFT) in order to identify the coordinates involved in the relaxation mechanisms and localize conical intersections, (ii) calculations of the energy profiles at a more refined level using the Coupled Cluster at second order (RI-CC2) and different strategies of optimization. The measured  lifetime (1.5ns) of the first excited state pp* of the folded form (NAPA B), 50 times shorter than that of the extended form (NAPA A), are attributable to mechanisms involving an excitation transfer to a np* state induced by a distortion of the peptide bond.

Others mechanisms have been proposed to explain the very different behavior of the two other conformers (NAPA A and C). These first encouraging results thus open the way for a whole new field of research on the nonradiative deactivations which are ubiquitous in proteins. Synergetic theoretical/experimental studies are under progress in the SBM team in order to precise the impact of microsolvatation or the number of residues on these mechanisms. Conformer-selective measurements in the femtosecond regime are now targeted by the project DIRCOS gathering teams from SPAM and ISMO and funded by the LabEx PALM.

 

References :

1Unravelling the Mechanisms of Radiationless Deactivation in Model Peptides Following Photoexcitation of a Phenylalanine Residue.  Malis, M., Ljubjic, I., Doslic, N., Loquais; Y., Gloaguen, E., Tardivel, B., Broquier, M., Jouvet, C., Brenner, V., Mons, M., 2013, J. Am. Chem. Soc, 134, 20340.

2Probing the competition between secondary structures and local preferences in gas phase isolated peptide backbones. W. Chin ; F. Piuzzi, I. Dimicoli and M. Mons, 2006,  Phys. Chem. Chem. Phys. 8, 1033.

 

Contacts :

 

 

A method to observe the complete vibrational spectrum of ionized molecules
Last Update: 21 May 2013

The strength of the NHamide---Smethionine revealed by spectroscopy of small peptides
Last Update: 21 May 2013

Imagerie photochimique du champ proche optique de nanocubes d’or
Last Update: 15 March 2012

Des tapis de nanotubes alignés, en grande surface !
Last Update: 31 January 2012

Nouvelles lumières sur l’interaction entre les rayons UVA et l’ADN
Last Update: 3 February 2014

Synergy btetween experiment and theory for the simulation of protein folding
Last Update: 21 September 2010

Un nouveau composé aux propriétés intéressantes d'absorption optique dans le domaine visible : TiO
Last Update: 17 June 2010

Synthèse de nanotubes marqués au carbone 14 pour des études de biodistribution
Last Update: 13 January 2011

A surprising dynamic of cluster fragmentation
Last Update: 13 November 2007

Chirality and folding of peptide chains
Last Update: 23 March 2007

Recent results in physicochemistry with the very new laser PLFA
Last Update: 16 March 2007

Effets coopératifs dans l'absorption du rayonnement UV par les bases de l'ADN
Last Update: 3 February 2014

Repliement de chaînes peptides en détente supersonique
Last Update: 3 February 2014

Formation of carbon nanotube multi-layers and identification of their growth mode
Last Update: 5 January 2010

Participation d'un état de Rydberg à la redistribution ultrarapide de l'énergie électronique du TDMAE [tetrakis(diméthylamino)éthylene]
Last Update: 3 February 2014