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Was life as we know it today preceded by a world based on RNA as a universal building block and only later replaced by DNA? An interdisciplinary research team from Dortmund and Munich is investigating the role that ribonucleic acid (RNA) might have played in the origins of life. The work shows how, under realistic geological conditions, physical non-equilibrium processes could have encouraged processes that might have been significant for the origins of life. Their findings were published recently in the prestigious journal Nature Chemistry.
While in today’s life forms deoxyribonucleic acid (DNA) contains the blueprint of proteins, the nanomachines of life, in the hypothesis of the RNA world its sister polymer plays a central role. The hypothesis assumes that life developed out of self-replicating RNA molecules which existed before the evolution of DNA and proteins. RNA can be both – an information store and a nanomachine. This makes it particularly interesting as a candidate for the first biopolymer of life because in principle it can, as a consequence, copy the sequence of other RNA strands and thus could have triggered the process of Darwinian evolution.
To be able to fulfill its task as a nanomachine, RNA must, however, fold into a correct and thus active form (similarly to proteins) – a process for which it places specific demands on its environment. In particular, it requires a relatively high concentration of doubly charged magnesium ions and a concentration of singly charged sodium ions which is as low as possible because the latter can lead to misfolding of the RNA strands. To date, however, it was unclear how such beneficial conditions could be produced through prebiotically plausible processes.
Research collaboration between biophysics, geosciences, and chemical biology
In an interdisciplinary research approach, scientists from LMU Munich and TU Dortmund University working in biophysics, geosciences, and chemical biology have now succeeded in showing how the correct ratio of magnesium and sodium ions for RNA folding could be achieved by natural processes from basalt, widely available then as it is today, and simple heat flows.
For this purpose, first of all the geosciences group led by Don Dingwell and Bettina Scheu (LMU) synthesized basalt samples in different physical states, i.e., rock or glass. Basaltic glass is obtained through the rapid cooling of molten basalt, a natural process that has taken place continuously on Earth since the oceans first existed. In a second step, the biophysicists in the working group led by Dieter Braun and Christof Mast (LMU) studied the quantities of magnesium and sodium ions that could be precipitated under a wide range of parameters, such as temperature or grain size of the geomaterial. The results showed that in all cases significantly more sodium ends up in the water than magnesium – the latter in far lower concentrations than needed for RNA nanomachines.
However, if we now look at the full picture with heat flows, which were most likely present due to the high level of geological activity, the situation changes considerably. In the fine channels, like are easy to find in basaltic glass, such a heat flow leads to the simultaneous convection of the water and a drift of the salt ions against the heat flow. This effect, known as thermophoresis, is greatly dependent on the valency and size of the ions. In combination, convection and thermophoresis ultimately lead to a higher local accumulation of magnesium ions than of sodium ions. The researchers were able to show that the different degrees of concentration of the salts increase with the size of the overall system.
The working group led by Hannes Mutschler (TU Dortmund University) provided the corresponding test systems in the form of catalytically active RNA strands (ribozymes). In particular, the team was able to show that thermophoretic conditions vastly improve a model ribozyme’s self-replication. They also observed the same effect for another ribozyme which, influenced by thermophoresis, was able to link several short RNA strands and thus produce very long RNA molecules. Through the separation of the sodium and magnesium ions, as occurs in thermophoretic systems, these two fundamental biological activities were also far more effective. Even very large quantities of excess sodium in the range of 1000:1 compared to magnesium, which are assumed in some prebiotic scenarios and incompatible with RNA catalysis, can be balanced out through the scenario presented in the paper, thus allowing the ribozymes to do their job nonetheless.
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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 15 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”.