Scientists at the European Molecular Biology Laboratory in Heidelberg, Germany have developed a new adaptation of a technique called cryo-electron tomography to provide high resolution 3-D imaging of cells.
Traditional electron tomography can generate 3-D extreme close-ups of cells, but the procedure comes at a cost. Samples to be studied typically undergo elaborate chemical treatment that allows them to withstand the vacuum within the microscope and the powerful beam of electrons used to generate the image. However, that chemical processing also disturbs proteins and organelles from their natural configurations, destroying valuable information about how they function.
Scientists can circumvent this problem by freezing a sample so quickly that ice crystals–which would ravage the cell’s delicate internal structures–don’t have time to form. But since samples must be extremely thin for cryo-electron tomography to work, most cell types were ineligible. Only tiny bacterial cells and the thin fringes of eukaryotic cells made the cut.
Now Frangakis and his team have developed a way to cut frozen cells into miniscule slices, revealing the previously unavailable innards of much thicker cells. This includes eukaryotic cells–cells with nuclei–like those that make up human tissues. The scientists then use a lower-power electron beam to image the sample, so that it holds up longer in the microscope. They have also refined the software needed to build a 3-D representation of the slice.