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Rainer Kaufmann

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Experimental Cryo-Photonics

IMAGE: Martin Bühler for Volkswagen Foundation

“Cutting edge technology is the key to new biological discoveries. But still, many biological questions remain unanswered due to the lack of suitable technology. At the CSSB we are not only relying on state-of-the-art commercially available solutions, but also focus on developing new methodology to push the boundaries of biological imaging.”

Rainer Kaufmann, CSSB Group Leader

Previous and current research

Super-resolution fluorescence microscopy under cryo-conditions (super-resolution cryo-FM) is a new field of microscopy that is aiming to combine super-resolution concepts with the benefits of cryo-immobilized samples. Pushing the resolution of the microscope is only one part of the story in biological imaging. Equally important is the structural preservation of the sample to prevent artefacts and misinterpretation of the data. Making use of the near-native state of the sample when immobilized by fast freezing methods leads to two major application areas of super-resolution cryo-FM:

1) Provide an alternative to conventional (ambient temperature) super-resolution FM methods, where currently the common practise for immobilization is chemical fixation.

2) Bridge the resolution gap in cryo-CLEM (correlative light and electron cryo-microscopy) to take full advantage of the complementary features of both imaging modalities.

The key for super-resolution imaging in general is photo-switching of the fluorophores. As this is only poorly studied and understood under cryo-conditions, one of our major aims is to gain a deeper insight into the photo-physical mechanisms in different molecules at a temperature range suitable for amorphous ice (devitrification point of water: -135°C).

We are focusing on developing new techniques and methodology in the area of super-resolution cryo-FM with a particular interest on super-resolution cryo-CLEM (imaging the same sample with super-resolution cryo-FM and subsequent cryo-EM). Minimizing the resolution gap in cryo-CLEM will open up a broad spectrum of applications in the field of structural biology.

In close collaboration with other groups in the CSSB we will use super-resolution cryo-CLEM to tackle current biological questions in the context of infectious diseases ranging from the single particle to the cellular level.

Future projects and goals

Super-resolution cryo-FM/cryo-CLEM is currently at a very early and experimental stage. Overcoming technical challenges and a better understanding of the underlying photo-physics will help us to push the boundaries of this method and turn it into a powerful tool for structural biology.

Publications

Gartenmann, L., Wainman, A., Qurashi, M., Kaufmann, R., Schubert, S., Raff, J. W., & Dobbie, I. M. (2017). A combined 3D-SIM/SMLM approach allows centriole proteins to be localized with a precision of∼ 4–5 nm. Curr. Biol., 27(19), R1054-R1055.

Wolff, G., Hagen, C., Grünewald, K., Kaufmann, R. (2016) Towards correlative super‐resolution fluorescence and electron cryo‐microscopy. Biol. Cell 108 (9): 245-258.

Johnson, E., Seiradake, E., Jones, E.Y., Davis, I., Grünewald, K., Kaufmann, R. (2015) Correlative in-resin super-resolution and electron microscopy using standard fluorescent proteins. Sci. Rep. 5: 9583.

Kaufmann, R., Schellenberger, P., Seiradake, E., Dobbie, I.M., Jones, E.Y., Davis, I., et al. Hagen, C., Grünewald, K. (2014) Super-resolution microscopy using standard fluorescent proteins in intact cells under cryo-conditions. Nano Lett. 14 (7): 4171-4175.


Kaufmann, R., Hagen, C., Grünewald, K. (2014) Fluorescence cryo-microscopy: current challenges and prospects. Curr. Opin. Chem. Biol. 20: 86-91.

Seiradake, E., Schaupp, A., del Toro Ruiz, D., Kaufmann, R., Mitakidis, N., Harlos, K., Aricescu, A.R., Klein, R., Jones, E.Y. (2013) Structurally encoded intraclass differences in EphA clusters drive distinct cell responses. Nat. Struct. Mol. Biol. 20 (8): 958-964.

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