Electron tomography facility

Electron tomography facility

Electron tomography is a technique for 3-dimensional reconstruction of molecular complexes and cellular organelles at intermediate resolution of 3-7 nm. Biological samples can be studied either in situ or in vitro.

Description

Electron tomography allows a supramolecular object to be reconstructed in three dimensions from a series of micrographs. As a first step, sequential images of the tilted object are recorded in the electron microscope. The data obtained are processed by 3D reconstruction algorithms, leading to a 3D reconstruction of the sample. The reconstructed volume can be visualised from all directions on the computer screen. Electron tomography is used in studies of cellular organelles both in situ and in vitro as well as macromolecular complexes. The method does not need any crystallisation that simplifies its usage.

We perform data collection at very low temperatures, which allows us to use cryo-embedded material in aqueous conditions. The most advantageous feature of tomography compared to other methods of structure determination is the possibility to reconstruct individual objects without averaging.

We are interested in both collaboration projects and in assisting researchers in their research. The primary tasks for the facility are:

to assist the researcher to prepare the object for electron tomography

to record the primary data in the electron microscope (requires comprehensive experience and technical competence)

to assist the researcher to reconstruct the object in three dimensions from the electron images taken. When the reconstruction once has been accomplished, the further analysis should be made in the home laboratory.

Infrastructure/Methods

We use a FEG transmission electron microscope (Philips CM200) equipped with a slow-scan CCD and TVIPS system for automated data collection to collect tilt series, usually at -180°C, with one- or two-degree increments from -60 to +60 degrees. The 3D reconstructions are then computed using weighted backprojection, refined with constrain maximum entropy method (COMET) and analysed. For more detailed methods, please find publications of interest on our research website.

Practical information

We are interested in both collaboration projects and in assisting researchers in their research. In order to get better insight into the kind of research that can be conducted using electron tomography, please find publications of interest on our research website. Please contact us for more information.

Interested in Industry collaboration
von Eulers väg 3
Karolinska Institutet, Department of Cell and Molecular Biology
171 77 Stockholm
+46 (0)8 524 873 61