How can we understand the cell membrane structure using chemistry tricks? In this recent JPhysD article, published as part of the Emerging Leaders special issue, Dr Erdinc Sezgin and his co-workers use advanced imaging and spectroscopy techniques to investigate how certain fluorescent molecules can react photo-physically to the membrane environment.
Each cell in our body has a membrane structure setting the boundary between interior and exterior of the cell. This structure is called a plasma membrane, and is composed mainly of proteins and lipids. The plasma membrane is not only a selective barrier for the cell but also the initiation point of most of the cellular events, consequences of which we encounter every day such as immunity against microbes, healing of a wound, even changes in your mood. Therefore, it is crucial to elucidate every possible aspect of the plasma membrane.
The membrane accommodates hundreds of different types of lipids and proteins. Some of these components have “feelings” for each other, thus they tend to get together and segregate from the others. This segregation causes distinct small regions in the plasma membrane enriched with certain molecules.
A cartoon showing the heterogeneous membrane structure, © Erdinc Sezgin
Cell membrane heterogeneity is vital as these distinct regions can perform multiple functions. Therefore, scientists have made tremendous effort to understand the nature of this membrane heterogeneity in the last decades. One particular tool to elucidate the physico-chemical state of these membrane compartments (for instance, how tightly the molecules are organized), is chemicals that can fluoresce differently in different environments. In other words, they change their colour depending on, for example, the polarity, viscosity or the electrical potential of the environment.
In our recent work, we tested two of such chemicals commonly used in membrane research. By using advanced microscopy and spectroscopy tools, we tested whether the reason for the change in their colour (“spectral shift”) in different regions of the membrane is the same for both molecules. We found that two molecules, despite being used for the same purpose, react to different properties of the cell membrane. While one of them was very sensitive to the cholesterol content (a fundamental element of the plasma membrane and a regulator of plasma membrane fluidity), the other one was more sensitive to temperature changes. Detailed analysis on their photo-physical behaviour showed that underlying principles behind their spectral shift is significantly different.
Our findings will pave a way to more accurately investigate the cell membrane heterogeneity using diverse molecules and advanced microscopy techniques.
The full article is available now for free on IOPscience.
About the authors
Erdinc Sezgin is an EMBO and a Marie Skłodowska-Curie fellow at the MRC Weatherall Institute of Molecular Medicine, University of Oxford since 2014. He carried out his PhD work in the group of Petra Schwille at the Technical University of Dresden and a short postdoctoral period in Kai Simons lab at Max Planck Institute of Cell Biology and Genetics in Dresden, Germany. His current research is focused on the role of membrane heterogeneity in immune system.
Mariana Amaro is a postdoctoral fellow in the Hof Lab, at the J. Heyrovský Institute of Physical Chemistry of the C.A.S.
Francesco Reina is a PhD student in the Eggeling Lab, at the MRC Weatherall Institute of Molecular Medicine, University of Oxford.
Martin Hof is a professor at the J. Heyrovský Institute of Physical Chemistry of the C.A.S.
Christian Eggeling is a professor at the MRC Weatherall Institute of Molecular Medicine, University of Oxford.
This work is licensed under a Creative Commons Attribution 3.0 Unported License. Figure and author images © Erdinc Sezgin.
Categories: Journal of Physics D: Applied Physics
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