Skip to main content

Steering attosecond electron dynamics in biomolecules with UV-XUV LIGHT pulses

Periodic Reporting for period 4 - STARLIGHT (Steering attosecond electron dynamics in biomolecules with UV-XUV LIGHT pulses)

Reporting period: 2019-09-01 to 2020-12-31

The main goal of the project is to study the electron dynamics resulting from the interaction of biomolecules with light. Ultrafast mechanisms activated by the light-molecule interaction have been demonstrated to be at the basis of more complex chemical and biological processes such as photosyntesis, energy transfer, vision, DNA damage and repair. By using the shortest light pulses currently available (attosecond pulses) we can capture the electronic motion in biomolecules. Ultimately, we would like to understand the role of this ultrafast dynamics in the photophysics of the biomolecule. Particular attention is devoted to DNA building blocks with the aim of tracking the UV-induced electronic charge redistribution potentially leading to structural changes and damage. With this research we foreseen the possibility to follow and control the ultrafast electronic charge flow in our own biomolecules and obtain the full elucidation of the role of the electron dynamics in the possibility to prevent/favor subsequent structural changes leading to damage.
This research has the ambition to have impact in different fields including photo-chemistry and photo-biology with tremendous prospects in phototherapy and for the engineering of new drugs.
At the end of this action, we have been able to demonstrate that - by taking advantage of the purely electronic response of a DNA nucleobase (adenine) - it is possible to change the photoreactivity of the molecule and to stabilize the molecule against radiation damage. This encouraging result opens new important perspectives in the possibility of exploring new photoprotection mechanisms. Additionally, we have been conducting preliminary experiments of UV-excited chiral molecules and obtained an ultrafast control knob over the chiral response. Since drugs vary in their interactions with the chiral environment of the body (such as enzymes, proteins, receptors), we could foresee the application of light fields to mediate this interaction and achieve new functionalities.
The action officially started on April 1st, 2015. Since 09/16, the Principal Investigator (PI) has been employed as leading scientist at DESY and a consortium of the former (CNR-IFN) and present (DESY) Host Institutions has been created. Until 12/17 the activities have been carried out in the attosecond laboratory of CNR-IFN, afterwards they have been moved to the CFEL-ATTO lab at DESY directed by the PI. The PI was in parental leave from 09/19 until 10/20.
The start-up phase of the project consisted in the following steps:
• Project management and coordination;
• People recruitment: two Post Docs (M. C. Castrovilli, E. Månsson), one PhD student (M. Galli), one visiting PhD (V. Wanie – payed by external funding);
• Acquisition of equipment;
• Acquisition, design and realization of specific components for the construction of the high-energy attosecond beamline, the UV source and the biomolecular source;
• Creation of STARLIGHT logo and facebook webpage (https://www.facebook.com/erc.starlight/)
• Creation of STARLIGHT webpage (https://atto.cfel.de/research/research_projects/starlight/)
After the start-up phase one additional PhD student has been recruited (K. Saraswathula), additionally one in-kind PhD student (L. Colaizzi) and one in-kind scientist (A. Trabattoni) joined the STARLIGHT team. The work has been carried according to the project objectives as described in the following:
Obj. 1 Development of a UV pump – XUV attosecond probe beam-line with high photon-flux.
A new attosecond beamline has been designed and successfully commissioned. XUV attosecond pulses have been synchronized with sub-4 fs IR pulses for preliminary XUV pump - IR probe experiments. Broadband UV pulses (210-310 nm), with energy up to 80 nJ, have been generated and synchronized with both the IR and XUV pulses. Additionally, we developed a novel XUV spectrometer based on a cylindrical mirror. This intermediate milestone has been successfully reached.
Obj. 2 Development of a few-cycle UV source for UV pump - UV probe experiments.
Sub-2fs, 200nJ pulses have been successfully generated and characterized. A UV-pump UV-probe setup has been designed and constructed. This intermediate milestone has been successfully reached.
Obj. 3 Study of the electron dynamics in biomolecular subunits.
Time resolved measurements in adenine and thymine have been performed using the XUV-pump IR-probe approach. In adenine, we have identified a new stabilization mechanism based on a purely electronic mechanism. We have subsequently performed a UV-pump IR-probe experiment in chiral molecules (e.g. methyl lactate) and proved that the UV-induced electronic excitation leads to a modulation of the chiral response. A double spectrometer for covariance mapping has been designed and commissioned. UV-pump UV-probe and UV-pump XUV-probe experiments are still ongoing. This intermediate milestone has been almost completely reached.
Obj. 4 Control of the electron dynamics in cyclic biomolecules.
To reach this final milestone, we are working jointly with the group of Prof. Jochen Küpper (DESY, world expert in controlled molecular beams). By combining his molecular sources with our light sources, we will be able to drive ring currents in cyclic molecules. Experiments, originally planned for 2020 and delayed due to COVID-19, will be performed at the CFEL-ATTO lab at DESY as soon as possible.
Obj. 5 Study of the electron dynamics in DNA double helix.
For reaching this final milestone, we are currently working in collaboration with the group of Dr. Sadia Bari (DESY, Hamburg, long-standing expertise in electrospray ionization (ESI)). As a preliminary step, we investigated proton migration in peptides following IR excitation with XUV probing at the sulphur K-edge during a beamtime at the free electron laser FLASH in Hamburg (manuscript in preparation). During this beamtime, the STARLIGHT team has acquired familiarity with the ESI source that will be transferred to the STARLIGHT beamline for the attosecond time resolved measurements in DNA.Experiments originally planned for 2020 and delayed due to COVID-19, will be performed at the CFEL-ATTO lab at DESY as soon as possible.
We have developed
i) beyond state-of-the-art attosecond technology, combining XUV attosecond pulses with sub-4 fs IR pulses and sub-2 fs UV pulses;
ii) an ultrafast (<2fs) UV light source (world record for the shortest UV pulse ever generated in 2019);
iii) multiple target sources including biomolecular subunits in gas phase, nanoparticles and droplets have been combined with this light technology for extreme time resolved measurements;
iv) a double spectrometer for the simultaneous detection of electrons and ions has been implemented in the beamline and advanced measurements have been performed.
The developed technologies have allowed for attosecond time resolved measurements in biomolecular subunits (including DNA nucleobases), chiral molecules, nanoparticles and nanodroplets. Within this action we have demonstrated that electron dynamics can be successfully investigated in very complex molecules and a certain degree of control of the photo-induced dynamics can be achieved on a few-femtosecond time scale. Although the COVID-19 pandemic did not allow for achieving all the goals, we consider a great success to have been able to develop beyond state-of-the-art light sources and to have used them to conduct pioneering experiments in complex molecules.
Picture of laser light in the attosecond beamline
Picture of STARLIGHT team working on the attosecond beamline
STARLIGHT logo
Picture of laser light in the attosecond beamline
Picture of laser light in the attosecond beamline
Picture of laser light in the attosecond beamline
Picture of STARLIGHT team working on the attosecond beamline
Picture of STARLIGHT team working on the attosecond beamline