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Sujet de stage / Master 2 Internship

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High energy chemistry

Contact: RENAULT Jean-Philippe, , jean-philippe.renault@cea.fr, +33 1 69 08 15 50
Summary:
The goal of these Masters internships is to set up methodologies to study the most energetic events that can occur in molecule, the ionizations of inner electronic shells It will be done using soft" X-ray radiation (100 - 2 keV) to trigger them selectively around the different ionization thresholds of the constituents of the biological material (such as carbon, oxygen, nitrogen or various metals also present in certain proteins).
Possibility of continuation in PhD: Oui
Deadline for application:18/04/2018

Full description:
The effect of ionizing radiation has been studied for more than hundred years, with regards to the degradation of biological material for radiobiology, but also for its many implications in nuclear industry fields. The events of simple ionizations by Ultra-Violet, corresponding in deposition of energy of a few eV (electron Volt) per molecules, are quite well known. The ionization effects of the outer electronic shells (involving electrons playing a role in the chemical bonds) by high-energy particles are also known (deposition of a few tens of eV, leading in particular to breakage of the OH and CH bonds). But the effects of the most energetic events that can be envisaged in chemistry - the ionizations of inner electronic shells (involving electrons with an atomic character and not playing a role in the chemical bonds) leading to a deposition of energies of several hundred eV on the scale of an atom - are still poorly understood in the condensed phase. Even if they remain rare events, when a medium is exposed to high energy particles, their effects on biomolecules, proteins and DNA could be very significant [1], and in particular could be a limiting factor for structural studies, X-ray microscopy and high-energy free-electron lasers (XFEL) [2,3].
The goal of these Masters internships is to set up methodologies to study these rare events using "soft" X-ray radiation (100 - 2 keV) to trigger them selectively around the different ionization thresholds of the constituents of the biological material (such as carbon, oxygen, nitrogen or various metals also present in certain proteins).

Within this broad topic, we propose different internships.

I1
During the Masters internship, the trainee will perform measurements around the carbon and oxygen edges using an irradiation cell with ultrafine windows (150 nm silicon nitride windows). These measures will give access to degradation products at long times (up to microseconds).. The trainee will initially put in place the analytical methods [4] making it possible to distinguish the products of inner shell ionization from the radiolytic background. These studies will be developed on small molecules of biological interest. (peptides, sugars, DNA base models).

I2 :
During the Masters internship, the trainee will work on the PLEIADES beamline at the SOLEIL Synchrotron, to improve the technique of a vacuum liquid jet (system that has just been successfully tested on the beamline). This technique makes it possible to perform electron spectroscopy on a solution. The energies transfer, after an inner shell excitation or an ionization, between the organic molecule and the solvent will be studied. Moreover, the structural changes of the biomolecule after different irradiation doses could also be investigated.
Technics/methods used during the internship:
Microfluidic, irradiation, radiolysis

Laboratory
Tutor of the internship

 

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