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Tag: University of Cologne

  • Astrophysics: Scientists observe high-speed star formation

    Astrophysics: Scientists observe high-speed star formation

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    Newswise — Gas clouds in the Cygnus X Region, a region where stars form, are composed of a dense core of molecular hydrogen (H2) and an atomic shell. These ensembles of clouds interact with each other dynamically in order to quickly form new stars. That is the result of observations conducted by an international team led by scientists at the University of Cologne’s Institute of Astrophysics and at the University of Maryland. Until now, it was unclear how this process precisely unfolds. The Cygnus X region is a vast luminous cloud of gas and dust approximately 5,000 light years from Earth. Using observations of spectral lines of ionized carbon (CII), the scientists showed that the clouds have formed there over several million years, which is a fast process by astronomical standards. The results of the study ‘Ionized carbon as a tracer for the assembly of interstellar clouds’ will appear in the next issue of Nature Astronomy. The paper is already accessible online.

    The observations were carried out in an international project led by Dr Nicola Schneider at the University of Cologne and Prof Alexander Tielens at the University of Maryland as part of the FEEDBACK programme on board the flying observatory SOFIA (Stratospheric Observatory for Infrared Astronomy). The new findings modify previous perceptions that this specific process of star formation is quasi-static and quite slow. The dynamic formation process now observed would also explain the formation of particularly massive stars.

    By comparing the distribution of ionized carbon, molecular carbon monoxide and atomic hydrogen, the team found that the shells of interstellar gas clouds are made of hydrogen and collide with each other at speeds of up to twenty kilometres per second. “This high speed compresses the gas into denser molecular regions where new, mainly massive stars form. We needed the CII observations to detect this otherwise ‘dark’ gas,” said Dr Schneider. The observations show for the first time the faint CII radiation from the periphery of the clouds, which could not be observed before. Only SOFIA and its sensitive instruments were capable of detecting this radiation.

    SOFIA was operated by NASA and the German Aerospace Center (DLR) until September 2022. The observatory consisted of a converted Boeing 747 with a built-in 2.7-metre telescope. It was coordinated by the German SOFIA Institute (DSI) and the Universities Space Research Association (USRA). SOFIA observed the sky from the stratosphere (above 13 kilometres) and covered the infrared region of the electromagnetic spectrum, just beyond what humans can see. The Boeing thus flew above most of the water vapour in the Earth’s atmosphere, which otherwise blocks out infrared light. This allowed the scientists to observe a wavelength range that is not accessible from Earth. For the current results, the team used the upGREAT receiver installed on SOFIA in 2015 by the Max Planck Institute for Radio Astronomy in Bonn and the University of Cologne.

    Even though SOFIA is no longer in operation, the data collected so far are essential for basic astronomical research because there is no longer an instrument that extensively maps the sky in this wavelength range (typically 60 to 200 micrometres). The now active James Webb Space Telescope observes in the infrared at shorter wavelengths and focuses on spatially small areas. Therefore, the analysis of the data collected by SOFIA is ongoing and continues to provide important insights – also regarding other star-forming regions: “In the list of FEEDBACK sources, there are other gas clouds in different stages of evolution, where we are now looking for the weak CII radiation at the peripheries of the clouds to detect similar interactions as in the Cygnus X region,” Schneider concluded.

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  • A quality-conscious protein

    A quality-conscious protein

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    Newswise — An interdisciplinary team of scientists from Cologne, Heidelberg and Munich have discovered a new function of a well-known enzyme: The signal peptidase complex in the endoplasmic reticulum cleaves faulty membrane proteins to initiate their degradation. In our cells, the endoplasmic reticulum is responsible for producing and controlling proteins that get secreted from the cell. The signal peptidase complex cuts these polypeptide chains to remove signal peptides that allow proteins to reach the endoplasmic reticulum in the first place, so that the mature proteins can fulfil their specific functions. A research team led by Matthias Feige, Professor for Cellular Protein Biochemistry at the Technical University of Munich (TUM), and Marius Lemberg, Professor for Biochemistry at the University of Cologne, has now discovered that the signal peptidase complex has a hitherto unknown function in another key process in cell biology: the quality control of membrane proteins. Their findings have now been published in Science under the title ‘The Human Signal Peptidase Complex Acts as a Quality Control Enzyme for Membrane Proteins’.

    Each cell is surrounded by a lipid bilayer, which protects the interior of the cell, but also demands for regulated transport of molecules and signals across this insulating layer to enable a plethora of cellular functions. Membrane proteins are integrated into this lipid bilayer and perform these functions. They are essential for cell survival and serve as the most important drug targets. To function properly, membrane proteins need to adopt a well-defined three-dimensional structure at the atomic level. Failures in this process can result in faulty proteins, which in turn gives rise to numerous diseases, including cancer as well as metabolic and neurodegenerative disorders.

    The team explored several disease-associated membrane proteins of our nervous system in order to better understand how our cells avoid that those faulty proteins damage them an and cause disease. During the course of their research, they observed that a protease – an enzyme that cleaves other proteins – initiates the degradation of the faulty mutant proteins. This degradation is essential to maintaining cellular function. However, they were unable to identify the protease involved. ‘All known candidates and commonly used inhibitors did not help us in our quest for the underlying molecular mechanism,’ said Feige.

    The breakthrough came after the researchers identified potential cleavage sites for the signal peptidase complex. ‘According to established textbooks, the signal peptidase complex cleaves off signal peptides during the maturation of secretory proteins and so far, this was mostly believed to be its sole function,’ Lemberg added. However, the researchers identified the signal peptidase complex as the protease they were searching for, revealing that it plays an essential role in membrane protein quality control.

    Subsequently, the interdisciplinary team of researchers identified several additional proteins that get cleaved and how this unexpected function might be regulated by the signal peptidase subunit SPCS1. ‘Since this factor is not essential for the initially described role in protein maturation, we realized that we were dealing with a previously unrecognized function,’ Feige explained.

    ‘Interestingly, SPCS1 is one of the only three genes that are down-regulated in all brain regions of Alzheimer’s disease patients, suggesting that our findings may have important implications for our understanding of human biology and age-associated disorders,’ Lemberg added. In Alzheimer’s disease, faulty proteins accumulate, which is thought to impair neuronal function. Feige concluded: ‘Our findings will help us to better understand how cells control the molecular shape of their proteins and lays the foundation for many future studies to come.’

    The research was funded by the German Federal Ministry of Education and Research (BMBF), the German Science foundation (DFG), and the Fritz Thyssen Foundation.

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