2019: Falk Schneider

During my Bachelor and Master studies in Biochemistry at the University of Hanover and the Hanover Medical School I became interested in quantitative methods and techniques to assess molecular interactions.

Fascinatingly, most biological processes start with the right molecules finding each other at the right time, yet measuring this accurately and shining a light on the underlying mechanisms poses a huge challenge. For my Master’s thesis project, I worked with Joerg Enderlein at the University of Goettingen and learned invaluable lessons on the physics of fluorescence and the use of spectroscopy and microscopy to evaluate diffusion dynamics as indicator of interactions in artificial model systems.

In 2015, I was then extremely fortunate to join the lab of Professor Christian Eggeling for my DPhil studies. I was recruited to investigate the motion and organisation of bio-molecules in the plasma membrane of living (immune) cells. My co-supervisor, Simon Davis, and my day-to-day supervisor, Erdinc Sezgin, introduced me to the magical world of membrane heterogeneity, short-lived interactions and their possible implications on immune cell activation. It is captivating how a highly complex process such as T-cell activation can be orchestrated by so many different proteins (and lipids) coming together in specific ways to form functional platforms or clusters in the living cell’s membrane right when needed.

To investigate this process conventional and super-resolution imaging has been widely used before, so I took a different angle and set out to directly observe diffusion to 'see' changes happening. To this end, I used super-resolved stimulated emission depletion (STED) microscopy in combination with fluorescence correlation spectroscopy (FCS, STED-FCS) to observe molecular diffusion on the relevant length scales. Employing a model membrane system, so-called giant plasma membrane vesicles (GPMVs), and STED-FCS I could show that most plasma membrane heterogeneity depends on an intact actin cytoskeleton and active processes. This study also suggested that the living plasma membrane is very heterogeneous in space, which led to the development of a new technique to enable spatially super-resolved diffusion measurements. For the first time molecular diffusion behaviours could be mapped across a larger area in the plasma membrane of living cells. The aforementioned methods allowed to dissect the diffusion in high temporal or spatial detail but rely on the ability to use a STED laser beam which is not available to every laboratory, can only act on certain fluorescent labels, and may be potentially harmful to the cell. Therefore, in collaboration with Marco Fritzsche, a statistical analysis pipeline was developed which uses large sets of conventional FCS data to infer information on the underlying dynamics on the population level. All the developed methods and approaches were validated with simulations performed in collaboration with Dominic Waithe and applied to various problems in other projects in the lab.

My DPhil work benefitted a lot from the highly collaborative and supportive environment in the lab and all across the WIMM. Working with many different researchers allowed me as a biochemist to learn about optics, scientific programming, immunology, membrane biology and a great deal about biophysics. I remain fascinated by the possibility to measure molecular interactions in live cells.

Despite the WIMM being a great place to work, the connection between students in different labs needed to be improved. Thus, I was involved with founding and leading the WIMM Graduate Student association to further improve the social and scientific environment and connect the WIMM student body. I really hope this is going to shape the institute into an even more collaborative and lively place to do great science.