In an interdisciplinary collaboration, researchers at the University of Münster have developed a method of visualizing an important component of the cell membrane in living cells. Therefore, they synthesized a family of new substances. The study has been published in “Cell Chemical Biology”.
Exchange of material and information at the level of individual cells requires transport and signalling at level of the plasma membrane enclosing the cell. Studying mechanisms at such tiny dimensions presents researchers with enormous challenges – for example, when they want to find out how an important component of the membrane – cholesterol – behaves and is distributed. So far, cholesterol can only be labelled to a very limited extent with fluorescent dyes, which can be visualized under the microscope without damaging the membrane.
Researchers at the University of Münster (Germany) have now developed a method which enables them to circumvent these difficulties. They synthesized a new type of compound which has properties similar to those of cholesterol, but which can be labelled with dyes and visualized in living cells. There, the compound realistically mimics the behaviour of natural cholesterol.
“Our new approach offers enormous potential for imaging membrane dynamics in living cells,” says Prof. Volker Gerke, one of the leaders of the study and Coordinator at the Cells-in-Motion Cluster of Excellence. The work is the result of an interdisciplinary study involving organic chemists, biochemists and biophysicists. The study appears in the current issue of the journal “Cell Chemical Biology”.
The detailed story:
Cells in the body are enclosed in a kind of protective envelope – the plasma membrane, which separates the cell from its environment. Cells also contain internal membranes which separate the individual components of the cell from each other and regulate the movement of substances between the different “spaces”. Cholesterol, a fatlike substance, is an important component of membranes ensuring that they work properly.
Synthesis of new compounds
In order to generate substances which behave similarly to natural cholesterol, the research group of organic chemists led by Prof. Frank Glorius first synthesized a series of chemical compounds. As a starting substance they used natural cholesterol, which was transformed into a certain organic salt, an imidazolium salt. “We already knew from previous studies that these salts interact well with biomolecules and are therefore suitable for cellular experiments,” says Frank Glorius, who also led the study.
In order to compare the biophysical properties of the newly synthesized compounds with those of the natural cholesterol, the researchers incorporated the substances to synthetic model membranes consisting of phospholipids (these phospholipids constitute the main component of membranes).
Biochemists and Biophysicists at the Cluster of Excellence in the group of Prof. Dr. Hans-Joachim Galla measured, among other things, how the new substances affected the phase transition temperature of model membranes, and how they changed the fluidity in the phospholipid layer at different temperatures.
“After evaluating the data, we finally settled on three compounds which exhibited very similar properties to those of natural cholesterol,” says Lena Rakers, a PhD student of Organic Chemistry and one of the two first authors of the study.
Experiments in living cells
The researchers selected these compounds in order to examine them in living cellular membranes, thereby studying them in even more complex structures. For this purpose, they used cultures of human epithelial cells – HeLa cells – as well as cells from human blood vessels, HUVEC cells. Due to their structure, the newly synthesized substances fitted well into the cellular membranes. With the aid of surface mass spectrometry, the researchers measured the molecules in the membrane and could show that the compounds behaved in a very similar way to natural cholesterol in living cells, too.
Because of its structure, one of the new substances could be labelled with fluorescent dyes. To this end, the researchers attached an azide group onto the substance. They then linked the dyes to this azide group using click chemistry – an effective method enabling molecular components to be joined on the basis of a few chemical reactions. Finally, the biochemists visualized the substance in living cells using high-resolution confocal microscopy.
In this way, they were able to observe its distribution and dynamic changes. “These analyses also showed that the novel compound behaved analogously to cellular cholesterol,” says David Grill, a PhD student of Biochemistry and the other first author of the study. One great advantage of the new method is that during the entire process the components and the properties of the cellular membrane remained undamaged.
In the future the researchers want to continue developing their method and test the new substances in further cellular studies using a variety of microscopic imaging methods. One of their aims is to use click chemistry to attach fluorescent dyes and other molecules to the new compounds to eventually introduce selective changes in the membrane.
The study received financial support from the German Research Foundation (DFG), specifically through the Cells-in-Motion Cluster of Excellence and the Collaborative Research Centre 858 (“Synergistic Effects in Chemistry – From Additivity towards Cooperativity”) at Münster University as well as an individual DFG grant.
Rakers L#, Grill D#, Matos A, Wulff S, Wang D, Börgel J, Körsgen M, Arlinghaus HF, Galla HJ*, Gerke V*, Glorius F* (2018): Addressable Cholesterol Analogs for Live Imaging of Cellular Membranes. Cell Chem Biol; DOI: 10.2016/j.chembiol.2018.04.015.
https://www.uni-muenster.de/Chemie.oc/glorius/glorius.html Prof. Frank Glorius
https://www.uni-muenster.de/Cells-in-Motion/people/all/gerke-v.php Prof. Volker Gerke
Svenja Ronge | idw - Informationsdienst Wissenschaft
Drugs for better long-term treatment of poorly controlled asthma discovered
15.10.2019 | University of South Florida (USF Health)
Epilepsy: Seizures not forecastable as expected
25.09.2019 | Rheinische Friedrich-Wilhelms-Universität Bonn
A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)
It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.
The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...
Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.
Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...
A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.
The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...
Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).
Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...
02.10.2019 | Event News
02.10.2019 | Event News
19.09.2019 | Event News
17.10.2019 | Physics and Astronomy
17.10.2019 | Physics and Astronomy
17.10.2019 | Life Sciences