Special issue on electron tomography.
This special issue of the Journal of Structural Biology is devoted to electron tomography and is based on posters and presentations given at the 6th International Conference on Electron Tomography that took place May 2011, at the EMBL Heidelberg. The conference covered recent software and hardware developments as well as exciting applications exemplifying the diversity of biological fields in which electron tomography is considered as a central technique. Electron tomography and cryo-electron tomography in particular, became the method of choice for acquiring insights into the molecular organization and architecture of tissues, cells, organelles, and macromolecular assemblies, in situ. It is now considered to play a pivotal roll in answering fundamental questions in cellular and structural biology. The field of electron tomography has grown tremendously during the last decade as a result of improved software for 3D averaging and visualization of 3D images, the development of larger cameras and direct detection chips, as well as fully automated and high-throughput tilt-series collection systems for electron microscopes. Yet, there remains considerable room for improvement, especially in algorithms for classification of subtomograms and feature segmentation, as well as camera improvements, correlative light and electron microscopy and advanced specimen preparation techniques. Contributions to this special issue also address some of these issues. The application of cryo-electron tomography is of great interest since it provides the means for studying tissues and cells captured in a close-to-native state, but the methodology still requires a high level of expertise. Dose sensitivity and sample thickness remain major resolution limiting factor, however, improved detectors promise to revolutionize the current low-dose imaging capabilities. Preparation of frozen-hydrated specimens, especially the production of cryo-sections remains a bottleneck, but is of great