Deutsches Elektronen-Synchrotron DESY
Notkestraße 85
22607 Hamburg

Georg-August-Universität Göttingen
Wilhelmsplatz 1
37073 Göttingen

Electrospray ionization (ESI) is a gentle, state-of-the-art technique to introduce biomolecular ions from solution into the gas phase and into vacuum, providing a solvent- and substrate- free environment. This allows studying the molecule in a well-defined, isolated state, where only intramolecular interactions have to be considered for describing structure and dynamics. The combination of an ESI source with advanced light sources such as synchrotrons, free- electron lasers and high harmonic generation sources allows for a novel and unique way to investigate structure and dynamics of gas-phase biomolecules. In particular, synchrotron and free-electron laser sources have the great advantage of superior photon brilliance, a wide photon energy range as well as polarization tunability. This enables systematic studies of energy and polarization dependent effects of ionization and dissociation processes. The following fundamental scientific complexes will be targeted within this project:

(i) Circular dichroism: Homochiral molecules have different absorption efficiencies for right or left circularly polarized light, the so-called circular dichroism (CD). Many CD studies aimed at discovering structural information on amino acids, proteins and DNA (building blocks) have been performed in the ultra-violet (UV) spectral region, but only a few CD studies enter the X-ray spectral range, where despite a very localized excitation, strong CD was observed. This local, site-selective probing with an X-ray pulse does not average the signal over the whole molecule, as is the case in the UV-visible absorption, and hence is a more selective tool to investigate structure-dependent dynamics in the molecule.

(ii) Radiation damage: Radiation therapy relies on ionizing radiation, yet, there is no consistent knowledge of the exact cascade of processes leading to radiation damage in a cell on atomic length and time scales. It is important to understand the details in the mechanisms of radiosensitizers, to increase the impact on tumors and to find non-toxic alternatives. To study the ultrafast processes of radiation damage on the molecular level, photoionization and photodissociation experiments will be performed on gas-phase nucleobases, amino acids and small oligonucleotides. These molecules will be explored in the pure as well as nanosolvated form. Moreover, metal ligands as well as radiosensitizers like cisplatin attached to oligonucleotides will be studied.

(iii) Ultrafast charge migration: Ultrafast charge transfer is believed to play an important role in biological energy conversion processes, such as light harvesting processes in plants. Pump-probe experiments of peptides will be performed to understand the fast charge migration processes in detail in terms of size, structure and time.

Leader of the Young Investigators Group of Helmholtz:

Dr. Sadia Bari
Deutsches Elektronen-Synchrotron DESY
Notkestr. 85
22607 Hamburg

Phone: +49 40 8998-5093
Email: sadia.bari@desy.de

Partner university:

Prof. Dr. Simone Techert
Georg-August-Universität Göttingen
Wilhelmsplatz 1
37073 Göttingen

Weiterführende Links:

Sachbericht 2016 (14KB)

 

Sachbericht 2017 (14KB)

 

Sachbericht 2018 (338KB)

 

Sachbericht 2019 (1.5 MB)