The intermediate voltage (300kV) electron microscope equipped with a tilting sample holder for tomography and a cryostage is serving a longstanding need to provide key imaging technologies to a wide variety of biological and bioengineering research programs on the University of Wisconsin - Madison. Users of this microscope are heavily dependent on high resolution imaging for their work on a wide range of important topics, including membrane and protein trafficking, biomineral and biopolymers, viral replication and virus-host interaction, cytoskeletal organization and cell division, nerve terminal organization and exocytosis, bacterial architecture, imaging of molecular complexes, and neuroengineering. This imaging system enables researchers to collect multiple images of relatively thick samples over a series of tilt angles. All these images are mathematically processed to generate a 3D reconstruction (tomogram) of the original section. The increased acceleration voltage is essential for allowing the electron beam to penetrate the sample without plural or inelastic scattering, especially at high tilt angles where the section thickness doubles or nearly triples Electron tomograms of either plastic sections of biological samples or cryofixed biological specimens or biopolymers results in an axial resolution of 2-10 nm. The new equipment is housed in an existing, highly effective campus microscopy and characterization center, managed by a permanent, full-time PhD expert entirely funded by the center budget, and supervised by a dedicated advisory committee of faculty users.
The new tomographic system fosters many collaborations on campus and allows researchers and students from almost every single college/school to apply state-of-the-art high resolution imaging techniques. Hands-on demonstrations on the use and applications of the proposed EM are included in the imaging courses taught by the PI and co-PIs. In addition, annual summer workshops are held to train researchers and students on campus on tomographic approaches. The new microscope has also a very important role in outreach. Three-dimensional tomographic models are visually stunning representations. They convey 3D information of cellular structures in a very effective way to everyone, from highly trained biologists to the general public. The new Wisconsin Institute of Discovery (WID) has a microscope and imaging discovery niche in the Town Center that includes a high resolution display consisting of an array of monitors. Tomographic reconstructions derived from the use of the new microscope, including images of replicating viruses, cytoskeletal arrays during cell division, plant organelles, signal transmission in neurons, are displayed in these monitors. In addition, some tomographic models are printed in a 3D printer for display in the WID and other participating Departments.
We have acquired a transmission electron microscope that is able to image samples such as proteins and cells in frozen state and extract three-dimensional information from them (electron tomography). The microscope was installed in the Materials Science Center at the University of Wisconsin-Madison and has enabled a strong synergy between biologists and engineers. This has been a very important step towards a more comprehensive integration of infrastructure and resources from different units on campus. Graduate students, postdoctoral fellows, and principal investigators are using the microscope to collect structural and analytical data to understand the structure and function of molecular complexes, plant and animal cells, viruses, bacteria, biopolymers, and soft materials. The microscope is also used for teaching and training. The course "Materials Science and Engineering 758: Transmission Electron Microscopy" uses the microscope weekly to train 15 graduate students each Spring semester. The students received hands-on training in cryo-microscopy, tomography, and other analytical techniques. We have also organized a symposium on electron microscopy that brings to campus an internationally recognized expert in biological electron microscopy every Fall semester. This symposium gives the opportunity to both undergraduate and graduate students to learn about state-of-the-art imaging technologies in the field of electron microscopy