Highlights

 

Kupferhydroxid-Nanopartikel schützen vor toxischen Sauerstoffradikalen im Zigarettenrauch

Abwehrmechanismus der Natur mithilfe von Nanopartikeln nachgeahmt / Giftige Wirkung von Rauch wird verringert

Chemiker der Johannes Gutenberg-Universität Mainz (JGU) haben eine Methode entwickelt, um die giftige Wirkung kommerzieller Zigaretten zu senken. Obwohl laut Weltgesundheitsorganisation WHO jedes Jahr etwa 6 Millionen Menschen an den Folgen des Tabakkonsums sterben, wächst die Zahl der Raucher weltweit. Die Zahl der Todesfälle durch Tabakkonsum entspricht einem Wert, als würde stündlich ein Passagierflugzeug abstürzen. Im Jahr 2016 konnte die Tabakindustrie, laut Zahlen des Statistischen Bundesamtes, allein in Deutschland mit dem Verkauf von Zigaretten einen Umsatz von rund 20,5 Milliarden Euro erzielen.

Tabakrauch enthält nahezu 12.000 verschiedene Bestandteile, darunter neben narkotoxischen Komponenten wie zum Beispiel Nikotin und bluttoxischen Bestandteilen wie Blausäure oder Kohlenstoffmonoxid auch krebserregende Substanzen. Zu diesen gehören freie Sauerstoffradikale, sogenannte reaktive Sauerstoffspezies, von denen pro Zigarettenzug mehr als zehn Billiarden (1016) Moleküle eingeatmet werden. Die Mainzer Wissenschaftler unter der Leitung von Prof. Dr. Wolfgang Tremel haben einen Weg gefunden, die Zahl dieser freien Sauerstoffradikale und damit die Giftigkeit von Zigaretten deutlich zu senken. Diese Entwicklung könnte nicht nur dazu beitragen, den Genuss von Tabakprodukten ein Stück weit ungefährlicher zu machen, sondern sie lässt sich auch auf weitere Gebiete ausweiten, in denen reaktive Sauerstoffradikale ein Problem darstellen.

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Die grundlegenden Ideen holten sich die Forscher dabei von Enzymen aus der Natur. Eine erhöhte Konzentration von reaktiven Sauerstoffspezies, zum Beispiel durch enzymatische Dysfunktion, UV-Strahlung oder das Inhalieren von Zigarettenrauch, kann zu unkontrollierter Zellteilung und oxidativer Zellschädigung führen. Zur Regulierung der Radikalkonzentration verwendet die Natur antioxidativ wirkende Enzyme wie die Superoxid-Dismutase (SOD), die eine zentrale Rolle bei der Prävention von Krankheiten, etwa der Tumor- und Krebsbildung, Entzündungen sowie Schlaganfallerkrankungen, spielt. Das natürliche Enzym nutzt dabei Metalle wie Kupfer, Zink, Nickel, Eisen und Mangan als reaktive Zentren, an denen Sauerstoffradikale zersetzt werden, sodass der lebende Organismus vor ihrem aggressiven Reaktionsverhalten geschützt wird.

Viele Enzyme wie die SOD lassen sich leicht herstellen oder isolieren. Problematisch ist jedoch ihre geringe Stabilität bei hohen Temperaturen oder nicht-physiologischen pH-Werten. Mit Blick auf natürliche Enzyme beschäftigen sich Forscher im Bereich der Biomimetik damit, das biologische Reaktionsverhalten mit Hilfe synthetischer Verbindungen nachzuahmen. Der Chemiker Karsten Korschelt und die Lebensmittelchemikerin Dr. Carmen Metzger untersuchten Aminosäure-funktionalisierte Kupferhydroxid-Nanopartikel als potenzielle synthetische Analoga kupferhaltiger SOD. Dabei zeigte sich, dass die Partikel eine höhere katalytische Aktivität bei der Zersetzung reaktiver Sauerstoffradikale besitzen als das Enzym selbst. "Dies ist im Prinzip nicht verwunderlich, da alle Kupfer-Atome auf der Partikeloberfläche katalytisch wirksam sein können, das Enzym aber nur ein aktives Zentrum besitzt", teilt Prof. Dr. Wolfgang Tremel dazu mit. Im Gegensatz zu natürlichen Enzymen sind funktionalisierte Kupferhydroxid-Nanopartikel sehr stabil und kostengünstig herstellbar.

Pressemeldung der Johannes Gutenberg-Universität

Prof. Wolfgang Tremel, Dr.
Phone:+49 6131 39-25135

http://www.ak-tremel.chemie.uni-mainz.de/

1.
Karsten Korschelt,  Ruben Ragg,  Carmen S. Metzger,  Martin Kluenker,  Michael Oster,  Bastian Barton,  Martin Panthöfer,  Dennis Strand,  Ute Kolb,  Mihail Mondeshki,  Susanne Strand,  Jürgen Brieger,  M. Nawaz Tahir, Wolfgang Tremel
Glycine-functionalized copper(II) hydroxide nanoparticles with high intrinsic superoxide dismutase activity

How does ice melt? Layer by layer!

Scientists at the Max Planck Institute for polymer research have solved a controversial question concerning the melting of ice: it melts in a layer-by-layer fashion.

We all know that ice melts at 0°C. However, already 150 years ago the famous physicist Michael Faraday discovered that at the surface of frozen ice, well below 0°C, a thin film of liquid-like water is present. This thin film makes ice slippery and is crucial for the motion of glaciers.

Since Faraday’s discovery, the properties of this water-like layer have been the research topic of scientists all over the world, which has entailed considerable controversy: at what temperature does the surface become liquid-like? How does the thickness of the layer dependent on temperature? How does the thickness of the layer increases with temperature? Continuously? Stepwise? Experiments to date have generally shown a very thin layer, which continuously grows in thickness up to 45 nm right below the bulk melting point at 0°C. This also illustrates why it has been so challenging to study this layer of liquid-like water on ice: 45 nm is about 1/1000th part of a human hair and is not discernible by eye.

Scientists of the Max Planck Institute for Polymer Research (MPI-P), in a collaboration with researchers from the Netherlands, the USA and Japan, have succeeded to study the properties of this quasi-liquid layer on ice at the molecular level using advanced surface-specific spectroscopy and computer simulations. The results are published in the latest edition of the scientific journal Proceedings of the National Academy of Science (PNAS).

The team of scientists around Ellen Backus, group leader at MPI-P, investigated how the thin liquid layer is formed on ice, how it grows with increasing temperature, and if it is distinguishable from normal liquid water. These studies required well-defined ice crystal surfaces. Therefore much effort was put into creating ~10 cm large single crystals of ice, which could be cut in such a way that the surface structure was precisely known.

Inorganic nanoparticles on the other hand are readily available by cost-efficient synthesis and have been used for many years as heterogeneous catalysts in organic solvents. The past three decades, have seen a wide variety of materials, including metal complexes, polymers, and other biomolecules, that mimic the structure and function of naturally occurring enzymes. Among these, inorganic nanomaterials bear huge potential, because they are more stable than their natural counterparts, while having large surface areas and sizes comparable to those of natural enzymes. Therefore, an enormous amount of inorganic nanomaterials with intrinsic enzymatic activities has been reported. The microreview highlights the recent progress in the field of “Inorganic Nanoparticles as Enzyme Mimics” and focuses on enzymatic systems that only recently have been made available.

Ice melts layer by layer Zoom Image
Ice melts layer by layer

To investigate whether the surface was solid or liquid, the team made use of the fact that water molecules in the liquid have a weaker interaction with each other compared to water molecules in ice. Using their interfacial spectroscopy, combined with the controlled heating of the ice crystal, the researchers were able to quantify the change in the interaction between water molecules directly at the interface between ice and air.

The experimental results, combined with the simulations, showed that the first molecular layer at the ice surface has already molten at temperatures as low as -38° C (235 K), the lowest temperature the researchers could experimentally investigate. Increasing the temperature to -16° C (257 K), the second layer becomes liquid. Contrary to popular belief, the surface melting of ice is not a continuous process, but occurs in a discontinuous, layer-by-layer fashion.

"A further important question for us was, whether one could distinguish between the properties of the quasi-liquid layer and those of normal water" says Mischa Bonn, co-author of the paper and director at the MPI-P. And indeed, the quasi-liquid layer at -4° C (269 K) shows a different spectroscopic response than supercooled water at the same temperature; in the quasi-liquid layer, the water molecules seem to interact more strongly than in liquid water.

The results are not only important for a fundamental understanding of ice, but also for climate science, where much research takes place on catalytic reactions on ice surfaces, for which the understanding of the ice surface structure is crucial.

Dr. Ellen Backus
Phone:+49 6131 379-536

http://www.mpip-mainz.mpg.de/88225/Dr_Ellen_Backus

2.
M. Alejandra Sánchez, Tanja Kling, Tatsuya Ishiyama, Marc-Jan van Zadel, Patrick J. Bisson, Markus Mezger, Mara N. Jochum, Jenée D. Cyran, Wilbert J. Smit, Huib J. Bakker, Mary Jane Shultz, Akihiro Morita, Davide Donadio, Yuki Nagata, Mischa Bonn & Ellen H. G. Backus
Experimental and theoretical evidence for bilayer-by-bilayer surface melting of crystalline ice
DOI

Martin Brüggemann mit Klaus Tschira Preis für verständliche Wissenschaft ausgezeichnet

Entwicklung einer neuartigen Methode zur Untersuchung von Feinstaubpartikeln allgemeinverständlich erklärt

Der Chemiker Dr. Martin Brüggemann gehört zu den diesjährigen Preisträgern des Klaus Tschira Preises für verständliche Wissenschaft. Brüggemann hat 2015 am Max Planck Graduate Center (MPGC) über die Untersuchung von Feinstaubpartikeln auf ihre chemische Zusammensetzung promoviert und das Thema seiner Arbeit in einem populärwissenschaftlichen Artikel allgemeinverständlich dargestellt. Hierfür erhielt er jetzt die mit 5.000 Euro dotierte Auszeichnung der Klaus Tschira Stiftung. „Ich freue mich sehr über diese Auszeichnung und das damit verbundene Privileg, meine Studien einem breiten Publikum vorstellen zu dürfen. Ich denke, dass es extrem wichtig ist, aktuelle Forschungsthemen auch außerhalb der akademischen Kreise zu diskutieren – gerade wenn es sich um globale, gesellschaftlich hochrelevante Probleme wie Feinstaub und Klimawandel handelt“, so Martin Brüggemann. Die Preisverleihung fand am 6. Oktober an der Universität Heidelberg statt.

Die Preisträgerinnen und Preisträger des Klaus Tschira Preises 2016: (v.l.) Dr. Martin Brüggemann, Jiehua Chen, Dr. Ágnes Cseh, Dr. Benjamin Gaub, Dr. Lena Veit und Dr. Martin Pitzer Zoom Image
Die Preisträgerinnen und Preisträger des Klaus Tschira Preises 2016: (v.l.) Dr. Martin Brüggemann, Jiehua Chen, Dr. Ágnes Cseh, Dr. Benjamin Gaub, Dr. Lena Veit und Dr. Martin Pitzer [less]

Aerosolpartikel sind kleinste Schwebstoffe in der Luft, die in der gesamten Atmosphäre vorkommen. Sie beeinflussen die lokale Luftqualität ebenso wie die Wolkenbildung und den Treibhauseffekt. Martin Brüggemann hat eine Methode gesucht, um die Partikel möglichst schnell analysieren und damit einordnen zu können. In seiner Promotionsarbeit entwickelte er ein Verfahren, um die Partikel zu verdampfen und sie dann mit der Massenspektrometrie, einer bewährten Nachweismethode, zu analysieren. Die Wirksamkeit der neuen Methode konnte nicht nur in Laborstudien, sondern auch bei Messungen im Fichtelgebirge unter realistischen Bedingungen bewiesen werden.

3.
Martin Brüggemann, Einar Karu, Torsten Stelzer, Thorsten Hoffmann
Real-Time Analysis of Ambient Organic Aerosols Using Aerosol Flowing Atmospheric-Pressure Afterglow Mass Spectrometry (AeroFAPA-MS)
DOI

Pressemitteilung Johannes Gutenberg Universität Mainz

Solids Go Bio: Inorganic Nanoparticles as Enzyme Mimics

Enzymes belong to the most selective and efficient catalysts known to men and have evolved to almost perfection over the last billions of years. So the question arises why natural enzymes have not reached broad industrial utilization. The answer is pretty simple in this case, as the production of natural enzymes is associated with immense costs and they generally suffer from an overall low stability and shelf-life, especially when exposed to external stimuli such as heat, sun light, and change of pH or solvent. Enzymes generally work unrivalled in terms of efficiency and specifity in their natural environment (aqueous buffers, pH around 7, ≈37°C), but quickly get misfolded or start denaturating when used in organic solvents or with temperatures of above 60°C (most industrial applications).

Enzymes belong to the most efficient catalysts known to man, but their high production costs and low stability cause severe problems. Inorganic nanoparticles on the other hand are readily available by cost-efficient synthesis and are more stable compared to their natural counterpart. In recent years, an enormous amount of inorganic nanomaterials with intrinsic enzymatic activities has been reported, which is summarized in this microreview with cover page and cover profile. Zoom Image
Enzymes belong to the most efficient catalysts known to man, but their high production costs and low stability cause severe problems. Inorganic nanoparticles on the other hand are readily available by cost-efficient synthesis and are more stable compared to their natural counterpart. In recent years, an enormous amount of inorganic nanomaterials with intrinsic enzymatic activities has been reported, which is summarized in this microreview with cover page and cover profile. [less]

Inorganic nanoparticles on the other hand are readily available by cost-efficient synthesis and have been used for many years as heterogeneous catalysts in organic solvents. The past three decades, have seen a wide variety of materials, including metal complexes, polymers, and other biomolecules, that mimic the structure and function of naturally occurring enzymes. Among these, inorganic nanomaterials bear huge potential, because they are more stable than their natural counterparts, while having large surface areas and sizes comparable to those of natural enzymes. Therefore, an enormous amount of inorganic nanomaterials with intrinsic enzymatic activities has been reported. The microreview highlights the recent progress in the field of “Inorganic Nanoparticles as Enzyme Mimics” and focuses on enzymatic systems that only recently have been made available.

Prof. Wolfgang Tremel, Dr.
Phone:+49 6131 39-25135

http://www.ak-tremel.chemie.uni-mainz.de/

4.
Ruben Ragg, Muhammad N. Tahir, Wolfgang Tremel
Solids Go Bio: Inorganic Nanoparticles as Enzyme Mimics
DOI

The effects of bacterial ice nuclei

Bacteria induce the formation of ice crystals by changing the order and dynamics of surface water molecules.

The freezing point of water is anything but a clear subject. Small droplets of the purest water only freeze at minus 37 degrees Celsius. Crystalization nuclei such as bacteria with ice-forming proteins on their surface are required for ice crystals to develop at just under 0 degrees Celsius. Researchers at the Max Planck Institutes for Chemistry and for Polymer Research have now elucidated the molecular mechanism how proteins congeal water molecules. According to the researchers, the proteins create ordered structures in the water and remove heat from the water. The findings not only help to facilitate a better understanding of the conditions under which frost damage occurs on plants. Since the bacteria are also airborne in the atmosphere, where they promote the formation of ice crystals, they also play a role in formation of clouds and precipitation – a major factor of uncertainty in weather and climate forecasts.

A water droplet in a cloud does not freeze at 0 degrees Celsius. Water forms ice only at the temperature which is commonly known as freezing point, if it is in contact with large surfaces with many and large ice forming parts – for example in a vessel or a lake. It has been known for some time that ice formation in water droplets is promoted by bacteria by specific protein molecules at their surface. Until recently, however, the molecular mechanisms responsible for this phenomenon have been unclear.

Ice crystals: Max Planck researchers discovered that certain bacteria can affect the ordering and the dynamics of water molecules in water droplets. Thus, ice crystals develop already at zero degrees Celsius or just below, and not at minus 37 degrees Celsius as in pure water. Protein molecules at the surface of the bacteria are responsible for this process. The graphics shows surface proteins (green arrows) that are surrounded by water molecules (red-white). Zoom Image
Ice crystals: Max Planck researchers discovered that certain bacteria can affect the ordering and the dynamics of water molecules in water droplets. Thus, ice crystals develop already at zero degrees Celsius or just below, and not at minus 37 degrees Celsius as in pure water. Protein molecules at the surface of the bacteria are responsible for this process. The graphics shows surface proteins (green arrows) that are surrounded by water molecules (red-white). [less]

Max Planck researchers have now unraveled the interactions between water and protein molecules at the bacterial surface. A team around Tobias Weidner who heads a research team at the Max Planck Institute for Polymer Research and Janine Fröhlich-Nowoisky, head of a research group at the Max Planck Institute for Chemistry, shows how ice-active bacteria influence the order and dynamics of water molecules. Together with American colleagues, the Mainz researchers have reported in the latest edition of the scientific journal Science Advances that the interactions of specific amino acid sequences of the protein molecules generate water domains with increased order and stronger hydrogen bonds. Additionally, the proteins remove thermal energy from the water into the bacteria. As a result, water molecules can aggregate into ice crystals more easily.

Ice-active bacteria are of great importance to scientists from a variety of different perspectives. On the one hand they can cause frost damage on the surface of plants. On the other hand when carried by wind into the atmosphere, they can trigger as crystalization and condensation nuclei the formation of snow and rain and thus influence the hydrological cycle. The spread of ice-active bacteria and other biological aerosol particles in the atmosphere and their impact on the formation of clouds and precipitation is a much-debated topic in current climate and Earth system research. Findings about the ice forming effect of bacteria can help to better understand their role in the climate system.

To understand how bacterial proteins stimulate the formation of ice crystals, the researchers concentrated on the ice-active bacterium Pseudomonas syringae. This bacterium can trigger the formation of ice in water droplets beginning at -2 degrees Celsius, while mineral dust usually triggers the freezing process only below -15 degrees Celsius. Due to their high ice nucleating ability, devitalized Pseudomonas syringae are used for the production of artificial snow in the commercial product “Snomax”.

The scientists utilized the so-called sum frequency generation spectroscopy for their studies. By use of laser beams this technology allows the investigation of water molecules at the bacterial or protein surface.

Thanks to the new findings it appears possible to imitate the bacterial ice nucleating mechanism and make it usable for other applications. “For the future it is conceivable to produce artificial nano-structured surfaces and particles to selectively influence and control the formation of ice,” says Tobias Weidner.

Encouraged by the positive results, the two Max Planck research groups want to extend their cooperation. “We plan to examine the ice-nucleating proteins in isolated form. Currently, we are still analyzing whole bacterial cells and cell fragments. Additionally, we want to extend the analyses to fungal ice nuclei,” explains Janine Fröhlich-Nowoisky, whose working group specializes in the characterization of biological ice nuclei and has an extensive collection of both ice-active bacteria and cultures from ice-active fungi available.

Dr. Tobias Weidner
Phone:+49 6131 379547

http://www2.mpip-mainz.mpg.de/~weidner/GroupPage/Home.html

5.
Ravindra Pandey, Kota Usui, Ruth A. Livingstone, Sean A. Fischer, Jim Pfaendtner, Ellen H. G. Backus, Yuki Nagata, Janine Fröhlich-Nowoisky, Lars Schmüser, Sergio Mauri, Jan F. Scheel, Daniel A. Knopf, Ulrich Pöschl, Mischa Bonn, Tobias Weidner
Ice-nucleating bacteria control the order and dynamics of interfacial water
DOI

Fusion protein controls design of photosynthesis platform

Collaborative project uncovers the role of a protein in the formation and maintenance of the inner membrane structures of photosynthetic systems

Chloroplasts are the solar cells of plants and green algae. In a process called photosynthesis, light energy is used to produce biochemical energy and the oxygen we breathe. Thus, photosynthesis is one of the most important biological processes on the planet. A central part of photosynthesis takes place in a specialized structure within chloroplasts, the thylakoid membrane system. Despite its apparent important function, until now it was not clear how this specialized internal membrane system is actually formed. In a collaborative project, researchers at Johannes Gutenberg University Mainz (JGU) in Germany have now identified how this membrane is generated. According to their findings, a protein called IM30 plays a major role by triggering the fusion of internal membranes. The study elucidating the role of IM30 involved biologists, chemists, biochemists, and biophysicists at Mainz University and the Max Planck Institute for Polymer Research. Their results have recently been published in the journal Nature Communications.

Chloroplasts are organelles found in higher plants and green algae. They contain an internal membrane system, so-called thylakoid membranes, where the key processes of photosynthesis take place. "A detailed understanding of photosynthesis and the associated molecular processes is essential to properly comprehend life on our planet," emphasized Professor Dirk Schneider of the Institute of Pharmaceutical Sciences and Biochemistry at JGU, who coordinated the study. "Despite the significance of the process, we know almost nothing about how these special membranes are formed and maintained." It had not previously been possible to identify a single fusion-mediating protein in photosynthetic cells, even though it was perfectly clear that such proteins have to be involved in the development of thylakoid membranes.

An IM30 ring docks with internal membranes. In the background is part of an image of a blue-green alga prepared using an electron microscope. A 3D model of the IM30 ring can be seen in the foreground. The images are not to scale. Zoom Image
An IM30 ring docks with internal membranes. In the background is part of an image of a blue-green alga prepared using an electron microscope. A 3D model of the IM30 ring can be seen in the foreground. The images are not to scale. [less]

With this in mind, the Mainz-based research team isolated and investigated the protein IM30 from a blue-green alga, which might be classified as a "free-living chloroplast." IM30 – the "IM" stands for "internal membrane" while 30 is its atomic mass (30 kilodaltons) – was first described in the mid-1990s and it was demonstrated that it binds to internal membranes. Thanks to the combined expertise of the teams headed by Professor Dirk Schneider, Professor Jürgen Markl of the JGU Institute of Zoology, and Professor Tobias Weidner of the Max Planck Institute for Polymer Research it has now emerged that IM30 forms a ring structure that specifically interacts with phospholipids of the membranes. "This binding alters the membrane structure and under certain conditions can lead to membrane fusion," explained Schneider. In absence of IM30, thylakoid membranes are noticeably deteriorated, which can subsequently lead to loss of cell viability. The IM30 fusion protein provides a starting point for future research, unraveling new types of membrane fusion mechanisms in chloroplasts and blue-green algae.

The interdisciplinary research project was primarily undertaken by doctoral candidates at the Max Planck Graduate Center (MPGC). The MPGC was founded in June 2009 to support joint projects and shared doctorates at Johannes Gutenberg University Mainz and the Max Planck Institutes for Polymer Research and for Chemistry, both of which are based in Mainz.

Dr. Tobias Weidner
Phone:+49 6131 379547

http://www2.mpip-mainz.mpg.de/~weidner/GroupPage/Home.html

6.
Raoul Hennig, Jennifer Heidrich, Michael Saur, Lars Schmüser, Steven J. Roeters, Nadja Hellmann, Sander Woutersen, Mischa Bonn, Tobias Weidner, Jürgen Markl, Dirk Schneider
IM30 triggers membrane fusion in cyanobacteria and chloroplasts
DOI

 
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