Press releases – October 2020

 

Oct 16 2020
10:06

​Physicists from Frankfurt, Hamburg and Berlin track the propagation of light in a molecule

Zeptoseconds: New world record in short time measurement

In the global race to measure ever shorter time spans, physicists from Goethe University Frankfurt have now taken the lead: together with colleagues at the accelerator facility DESY in Hamburg and the Fritz-Haber-Institute in Berlin, they have measured a process that lies within the realm of zeptoseconds for the first time: the propagation of light within a molecule. A zeptosecond is a trillionth of a billionth of a second (10-21 seconds).

FRANKFURT. In 1999, the Egyptian chemist Ahmed Zewail received the Nobel Prize for measuring the speed at which molecules change their shape. He founded femtochemistry using ultrashort laser flashes: the formation and breakup of chemical bonds occurs in the realm of femtoseconds. A femtosecond equals 0.000000000000001 seconds, or 10-15 seconds.

Now atomic physicists at Goethe University in Professor Reinhard Dörner's team have for the first time studied a process that is shorter than femtoseconds by magnitudes. They measured how long it takes for a photon to cross a hydrogen molecule: about 247 zeptoseconds for the average bond length of the molecule. This is the shortest timespan that has been successfully measured to date.

The scientists carried out the time measurement on a hydrogen molecule (H2) which they irradiated with X-rays from the synchrotron lightsource PETRA III at the Hamburg accelerator centre DESY. The researchers set the energy of the X-rays so that one photon was sufficient to eject both electrons out of the hydrogen molecule.

Electrons behave like particles and waves simultaneously, and therefore the ejection of the first electron resulted in electron waves launched first in the one, and then in the second hydrogen molecule atom in quick succession, with the waves merging.

The photon behaved here much like a flat pebble that is skimmed twice across the water: when a  wave trough meets a wave crest, the waves of the first and second water contact cancel each other, resulting in what is called an interference pattern.

The scientists measured the interference pattern of the first ejected electron using the COLTRIMS reaction microscope, an apparatus that Dörner helped develop and which makes ultrafast reaction processes in atoms and molecules visible. Simultaneously with the interference pattern, the COLTRIMS reactions microscope also allowed the determination of the orientation of the hydrogen molecule. The researchers here took advantage of the fact that the second electron also left the hydrogen molecule, so that the remaining hydrogen nuclei flew apart and were detected.
 
“Since we knew the spatial orientation of the hydrogen molecule, we used the interference of the two electron waves to precisely calculate when the photon reached the first and when it reached the second hydrogen atom," explains Sven Grundmann whose doctoral dissertation forms the basis of the scientific article in Science. “And this is up to 247 zeptoseconds, depending on how far apart in the molecule the two atoms were from the perspective of light."

Professor Reinhard Dörner adds: “We observed for the first time that the electron shell in a molecule does not react to light everywhere at the same time. The time delay occurs because information within the molecule only spreads at the speed of light. With this finding we have extended our COLTRIMS technology to another application."


Publication: Sven Grundmann, Daniel Trabert, Kilian Fehre, Nico Strenger, Andreas Pier, Leon Kaiser, Max Kircher, Miriam Weller, Sebastian Eckart, Lothar Ph. H. Schmidt, Florian Trinter, Till Jahnke, Markus S. Schöffler, Reinhard Dörner: Zeptosecond Birth Time Delay in Molecular Photoionization. Science https://science.sciencemag.org/cgi/doi/10.1126/science.abb9318

Image download: http://www.uni-frankfurt.de/93157222

Caption: Schematic representation of zeptosecond measurement. The photon (yellow, coming from the left) produces electron waves out of the electron cloud (grey) of the hydrogen molecule (red: nucleus), which interfere with each other (interference pattern: violet-white). The interference pattern is slightly skewed to the right, allowing the calculation of how long the photon required to get from one atom to the next. Photo: Sven Grundmann, Goethe University Frankfurt

Further information:
Prof. Dr. Reinhard Dörner
Institute for Atomic Physics
Telephone +49 69 798 47003
doerner@atom.uni-frankfurt.de
http://www.atom.uni-frankfurt.de

 

Oct 14 2020
14:16

Three-year German-American project studies biology of LRRK2 

Goethe University partner in US$ 7.2 million research project on Parkinson’s disease

FRANKFURT. About ten percent of Parkinson's cases can be ascribed to mutations in the LRRK2 gene. Five research teams from the University of California in San Diego, Goethe University Frankfurt and the University of Konstanz want to explain in the next few years how mutations in the LRRK2 gene trigger Parkinson's disease and what possible targets there are for drugs. The US-American initiative “Aligning Science Across Parkinson's" has made the equivalent of € 6.1 million available for this project.

In the early 2000s, it was discovered that in many Parkinson's patients a certain enzyme called LRRK2 mutates and evidently plays a significant role in five to ten percent of hereditary Morbus Parkinson and between one and five percent of the spontaneous form. LRRK2 is an enzyme that attaches phosphate groups to other proteins in the human cell and is far more active than normal in the brain cells of Parkinson's patients, leading it to block transport processes in the cell. Many inhibitors against the LRRK2 enzyme have already been tested in the past, but they are not sufficiently effective or their side-effects are too severe.

The five teams from USA and Germany want now to elucidate in detail the enzyme's structure and how it works in the cell and thus create a basis for the targeted production of inhibitors. A first three-dimensional structure of the LRRK2 protein was recently published by the research team in the journal Nature. The initiative “Aligning Science Across Parkinson's", which is backed by The Michael J. Fox Foundation for Parkinson's Research, is supporting the project financially.

Co-Project Manager Stefan Knapp, Professor for Pharmaceutical Chemistry at Goethe University, explains: “By comparing LRRK2 mutations in Parkinson's patients with normal LRRK2, we want to find out which tasks LRRK2 assumes in the cell, how the enzyme moves three-dimensionally, and how the mutated LRRK2 contributes to nerve cells dying off. While the expertise of our colleagues in the USA lies in various imaging methods, here in Frankfurt we'll develop chemical probes to localize and study LRRK2 in cells and we will produce recombinant LRRK2 variants that will help us to understand their three-dimensional structure."

Co-Project Manager Florian Stengel, Professor for Cellular Proteostasis at the University of Konstanz, says: “In the framework of this project, we here in Konstanz want to identify the cellular interaction partners of LRRK2. In this way, we'll be able to complete our picture of its cellular role and thus make it possible to develop a drug against LRRK2 mutated Morbus Parkinson."

Article on the first three-dimensional structure of the LKKR2 protein: C K Deniston, J Salogiannis, S Mathea, D M Snead, I Lahiri, M Matyszewski, O Donosa, R Watanabe, J Böhning, A K Shiau, S Knapp, E Villa, S L Reck-Peterson, A E Leschziner. Structure of LRRK2 in Parkinson's disease and model for microtubule interaction. Nature. 2020 Aug 19 https://pubmed.ncbi.nlm.nih.gov/32814344/


Pictures to download: www.uni-frankfurt.de/92946466

Caption: Professor Stefan Knapp, Institute of Pharmaceutical Chemistry, Goethe University, Frankfurt (Foto: Uwe Dettmar)

Further information:
Professor Stefan Knapp
Institute of Pharmaceutical Chemistry
Goethe University Frankfurt
Phone: +49 69 798-29871
knapp@pharmchem.uni-frankfurt.de

Professor Florian Stengel
Department of Biology / Laboratory of Cellular Proteostasis and Mass Spectrometry
University of Konstanz
Phone: +49 7531 88-5172
florian.stengel@uni-konstanz.de

 

Oct 6 2020
14:45

​Study by Goethe University shows: Particulate matter is also reduced – ventilation remains necessary because of CO2

Risk of infection: Air purifiers remove 90 percent of aerosols in school classrooms

FRANKFURT. Atmospheric researchers from Goethe University have demonstrated that air purifiers with a class H13 filter (HEPA) can lower aerosol concentration in a classroom by 90 percent within 30 minutes. Because this significantly reduces the risk of airborne infection with SARS-CoV-2, the scientists recommend placing such air purifiers in classrooms. In most cases, students and teachers did not find the noise made by the purifier disturbing. The study is now available as a preprint, prior to appearing in a scientific journal. (https://doi.org/10.1101/2020.10.02.20205633)

The most dangerous route to an infection with SARS-CoV-2 is via the air: For example, when infected persons sneeze or cough, they catapult relatively large droplets which, however, sink to the ground within a radius of two metres. Important are also aerosols, much smaller droplets, which we emit when speaking or breathing. Studies show that infectious SARS-CoV-2 pathogens can still be detected in such aerosols over three hours after emission and several metres away from an infected person. The fluid in such aerosol particles evaporates quickly, making them smaller and able to disperse in a room within a few minutes.

Together with his team, Joachim Curtius, Professor for Experimental Atmospheric Research at Goethe University, tested four air purifiers in a classroom with 27 students and their teachers over a period of a week. The purifiers had a simple prefilter for coarse dust particles and fluff as well as HEPA and active carbon filters. Together, the filters processed between 760 and 1,460 m3 of air per hour. Apart from aerosol load, the researchers also measured the volume of fine dust particles and CO2 concentration and analysed the noise levels caused by the device. The result: Half an hour after switching it on, the air purifiers had removed 90 percent of the aerosols from the air.

Professor Curtius explains: “On the basis of our measurement data, we've calculated a model that allows the following estimate: An air purifier lowers the amount of aerosols to such a considerable degree that the risk of being infected by a highly contagious person, a superspreader, is greatly reduced. That's why we're recommending that schools use HEPA air purifiers this winter with a sufficiently high air flow rate."

Noise measurements and a survey among students and teachers revealed that in most cases the noise made by the air purifier was not considered disturbing, provided that the appliance was not running at the highest level.

The researchers also measured that the air purifier – apart from lowering the risk of infection –additionally reduced allergens and fine dust particles (PM10). Joachim Curtius: “An air filter does not, however, replace opening the window at regular intervals, which is important for decreasing CO2 concentration in the room. Our measurements in the classrooms showed that levels often exceeded the recommended limits. Here, we recommend installing CO2 sensors so that students and teachers can monitor this themselves."


Publication: Joachim Curtius, Manuel Granzin, Jann Schrod: Testing mobile air purifiers in a school classroom: Reducing the airborne transmission risk for SARS‐CoV‐2. Preprint: medRxiv 2020.10.02.20205633; doi: https://doi.org/10.1101/2020.10.02.20205633

Further information:

Professor Dr. Joachim Curtius
Institute for Atmospheric and Environmental Sciences
Goethe University
Tel.: +49 69 798-40258
curtius@iau.uni-frankfurt.de