Cells spin into view

Ohad Medalia, Wolfgang Baumeister, and colleagues (Max Planck Institute for Biochemistry, Martinsried, Germany) have shown that a three-dimensional version of electron microscopy (EM), called cryoelectron tomography (cryo-ET), can be applied to whole intact cells. Their eventual aim, says Medalia, is “to get pseudo-atomic maps of the cytoplasm.”

Standard EM methods yield two-dimensional projections. Thus, researchers such as Gary Borisy (Northwestern University, Chicago, IL) have studied systems that approximate two dimensionality, such as the flattened lamellipodia at the front of a moving cell. But, says Borisy, “there is no substitute for three-dimensional data. Even in the systems we have analyzed I would love to have three-dimensional data.”

The tomogram provides these data by rotating the sample between sampling runs. After each rotation the sample must be refocused and realigned—a...