When you sit down to watch your new 4K television for the first time, suddenly those old standard-definition re-runs of “Star Trek” don’t look so futuristic. The leaps in scientific and technological knowledge responsible for the advance in video quality since the starship Enterprise took its first voyage in the 1960s are worthy of Starfleet.
But gains in image quality have not been limited to photography and film. A new way of capturing images with cryo-electron microscopes has sparked what is being called the “resolution revolution.” Using extreme cold to arrest fluid samples in motion, cryo EM allows researchers to see proteins, clusters of molecules, and viruses with astounding clarity — to the point where individual atoms may become visible.
In 2017, the Huck Institutes of the Life Sciences unveiled its Cryo Electron Microscopy Facility, which allows researchers to quickly create high-resolution three-dimensional models of intricate biological, chemical, and synthetic structures.
“It’s like putting on glasses for the first time,” said facility director Susan Hafenstein. “With cryo EM, we have gone from a general idea of structure to crystal-clear detail.”
How it works
Like other electron microscopes, the facility’s Titan Krios microscope creates images by firing electrons through a sample, where they encounter tiny structural features, and recording their image when they emerge. Sophisticated software uses thousands of images from each sample to create a 3D image of the structure in question.
The cryo EM differs from other kinds of electron microscope in that the sample consists of many copies of a particle, such as a protein, suspended in a liquid and then plunged into liquid nitrogen to preserve the natural shape of the particles and arrest them mid-movement. This allows scientists to glimpse processes such as an enzyme changing its shape as it catalyzes a chemical reaction, or a protein forming a complex with other molecules.
The Titan Krios can produce a 3D rendering of a structure in two ways. Single-particle reconstruction provides a high-resolution view of something relatively small, like a single protein. Cryo-tomography provides a view of larger structures in context, such as enzymes and other proteins bound together in a functional complex.
Both techniques generate thousands of images per sample — up to 10 terabytes of data per day. To meet the new challenges for data processing, transfer, and storage, Penn State implemented a high-speed fiber-optic network that allows data transfer from the microscope to the researcher ten times faster than before, and allocated additional storage space for researchers using the microscope.
“Penn State has made a huge investment in infrastructure,” said Hafenstein. “We needed to set it up so the data coming off the Krios has someplace to go, and someplace to go as fast as it is being created.”
During planning for the facility, scientists from the Materials Research Institute urged that the instrument be outfitted with a powerful upgrade: the ability to do spectroscopy on a sample being imaged. This would make it possible to see the overall structure of a particle and identify the chemical elements within it at the same time, opening up whole new lines of inquiry. To date, Penn State’s instrument is the only one in the world to have this dual capability.
Hafenstein uses the Titan Krios in her own research on how viruses bind to and enter host cells.
“There are all kinds of steps that the virus has to go through to enter and infect a human cell,” she said. “In the past we were never really able to see this entry process. Now with cryo EM we can, and that’s pretty exciting.”
She consults with researchers across campus who are using the new microscope to investigate questions as varied as how certain proteins are involved in the transmission of the malaria parasite and how sticky proteins called amyloids cluster into potentially damaging plaques in the brain. The work isn’t all biological; materials scientists are taking advantage of the instrument’s ability to provide high-resolution images of fragile “soft” materials that are hard or impossible to examine with other microscopic techniques.
Like the other 10 core facilities managed by Huck, the Titan Krios is available for use by all Penn State researchers and by outside academic and private sector clients. Scientists on campus meet often to share the newest ways to analyze data, discuss the challenges of particular projects, and explore how to enhance the vast potential of the new facility.
The combination of cryo EM technology and spectroscopy has positioned Penn State to make significant contributions to the field of structural biology and beyond.
“There are about 100 of these microscopes in the world today,” said Hafenstein, “but because of the unique combination of imaging technologies, ours is a one and only.”
Susan Hafenstein is associate professor of medicine, microbiology, and immunology at Penn State College of Medicine, associate professor of biochemistry and molecular biology in the Eberly College of Science, and Lloyd & Dottie Huck Chair of Structural Virology.
This story appeared in the spring 2019 issue of Research/Penn State magazine. It is abridged from an in-depth version of the story that appeared in Science Journal in fall 2018.