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Junior Professor Müge Kasanmascheff and her research team at TU Dortmund University have gained new insights into the structure and properties of the protein ribonucleotide reductase in living cells. Their work could prove especially significant for cancer research. The results were published recently in the renowned journal Angewandte Chemie.
For the functioning of cells in the human body, proteins perform important tasks. Depending on the type of protein they can, for example, transport metabolic products, enable cell movements, protect against infections, or catalyze biochemical reactions. In carrying out all of these tasks, the proteins are in constant exchange with their environment and interact with other proteins as well as with other cell components. To gain a better understanding of the functional mechanisms of cells, therefore, it is of great importance to better understand the structure and properties of particular proteins.
This is where the research of JProf. Kasanmascheff comes in: For her current publication, she and her research team analyzed the protein ribonucleotide reductase (RNR), which is indispensable for the production of DNA building blocks in the cells of nearly all plants and mammals, including humans. What’s special about this project is that all of the experiments were carried out in vivo, that is, in living cells instead of the usual artificial, in vitro environment. “We wanted to find out to what extent the actual structure and function of the RNR in living cells differs from the results of in vitro research,” Kasanmascheff says.
Electron spin resonance spectroscopy makes processes in cells visible
For her investigations, the junior professor uses the method of electron spin resonance spectroscopy (ESR spectroscopy). This works in a way that is similar to magnetic resonance imaging (MRI), which is commonly used in medical diagnostics. In both methods, a magnetic field causes certain particles to be excited and emit signals that can be recorded: In MRI, the spins of atomic nuclei are excited; in contrast, it is the spins of unpaired electrons within molecules that are excited in electron spin resonance spectroscopy. “This method is especially well suited for visualizing the structure and processes inside cells and involving proteins, because such unpaired electrons are the starting point for numerous chemical reactions in the cells and also occur in RNR,” explains JProf. Kasanmascheff. Molecules with unpaired electrons are generally referred to as radicals.
In the structure of RNR, there are two special radicals. They possess a so-called di-iron cofactor that enables the protein’s catalytic activity. Using ESR spectroscopy, the scientists were able to show that the structure and properties of the di-iron cofactor in the RNR of living E. coli bacteria do in fact correspond to those previously observed in vitro. On the basis of the experiments, however, the team also discovered that the regulation of RNR catalysis in living cells is different from what was observed in vitro. In vivo, both radicals of the RNA are not always involved in the catalysis; sometimes it is only a single one. These findings support the thesis that the activity of the RNR protein in living cells is regulated by changes in the concentration of the di-iron cofactor.
The results could also have relevance for cancer research
In another experiment, the Dortmund research team was also the first to succeed in inserting an artificial amino acid in place of the radical in the RNR protein of a living cell and then observing it. Using this artificial amino acid, it is also possible to influence the enzyme’s activity. This could prove to be an important step toward selectively influencing and manipulating the behavior of living cells in the future, Kasanmascheff says. The results are particularly relevant for cancer research, since cells always require RNR when they divide or need to repair damage to the DNA. If it were also possible to influence RNR activity in tumor cells in a targeted manner, the growth of tumors could be slowed down or even stopped completely.
Kasanmascheff and her team have published the results of this research, which was carried out within the framework of the Cluster of Excellence RESOLV, funded by the German Research Foundation (DFG), in the scientific journal Angewandte Chemie. The publication was honored as a “highly important paper,” a distinction awarded to only around ten percent of the papers published in the journal.
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The campus of TU Dortmund University is located close to interstate junction Dortmund West, where the Sauerlandlinie A 45 (Frankfurt-Dortmund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is “Dortmund-Eichlinghofen” (closer to South Campus), and from B 1 / A 40 “Dortmund-Dorstfeld” (closer to North Campus). Signs for the university are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dortmund.
To get from North Campus to South Campus by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at North Campus and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.
TU Dortmund University has its own train station (“Dortmund Universität”). From there, suburban trains (S-Bahn) leave for Dortmund main station (“Dortmund Hauptbahnhof”) and Düsseldorf main station via the “Düsseldorf Airport Train Station” (take S-Bahn number 1, which leaves every 20 or 30 minutes). The university is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.
You can also take the bus or subway train from Dortmund city to the university: From Dortmund main station, you can take any train bound for the Station “Stadtgarten”, usually lines U41, U45, U 47 and U49. At “Stadtgarten” you switch trains and get on line U42 towards “Hombruch”. Look out for the Station “An der Palmweide”. From the bus stop just across the road, busses bound for TU Dortmund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dortmund main station to the stop “Dortmund Kampstraße”. From there, take U43 or U44 to the stop “Dortmund Wittener Straße”. Switch to bus line 447 and get off at “Dortmund Universität S”.
The AirportExpress is a fast and convenient means of transport from Dortmund Airport (DTM) to Dortmund Central Station, taking you there in little more than 20 minutes. From Dortmund Central Station, you can continue to the university campus by interurban railway (S-Bahn). A larger range of international flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the university station.
The H-Bahn is one of the hallmarks of TU Dortmund University. There are two stations on North Campus. One (“Dortmund Universität S”) is directly located at the suburban train stop, which connects the university directly with the city of Dortmund and the rest of the Ruhr Area. Also from this station, there are connections to the “Technologiepark” and (via South Campus) Eichlinghofen. The other station is located at the dining hall at North Campus and offers a direct connection to South Campus every five minutes.
The facilities of TU Dortmund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the university are located in the adjacent “Technologiepark”.