Key Takeaways
- The UNC Cryo-EM Core is receiving the Titan Krios G4, one of the most powerful cryo-electron microscopes in structural biology, later this year.
- Since opening, the core has contributed to over 100 structural maps and trained more than 50 researchers across UNC and beyond.
- The core serves UNC researchers, external academic institutions, and industry partners through both fee-for-service and hands-on training models.
There is a Titan lying in wait in a warehouse in Garner, North Carolina.
Aptly named after the mythical Greek giant, the Titan Krios G4 – one of the most powerful cryo-electron microscopes in structural biology – stands nearly 12 feet tall and weighs several tons. It will be installed at the UNC Cryo-EM Core in the coming months, expanding the facility’s capabilities for single particle analysis and cryo-electron tomography by “a factor of three at the minimum,” says UNC Cryo-EM Core Director Joshua Strauss.
Despite its size, what makes the Krios remarkable isn’t how large it is but how small it can see. The instrument images biological samples in their near native state in water – proteins, receptors, viruses, nucleic acids captured exactly as they exist in the body. Structure, in biology, yields function – knowing the precise three-dimensional shape of a protein at atomic resolution reveals how it behaves, how it can be targeted, and what might be done to intervene.
The Titan Krios G4 resolves structures at atomic resolution, its Selectris X energy filter removing electrons that would otherwise blur the image. This is particularly valuable for thicker samples and for cryo-electron tomography, where the sample is tilted at multiple angles to capture different views of the same object. “It’s kind of like medical MRI body scan where the person goes in with an instrument and it takes different images of the person,” Strauss says, “but this is like a cell or a bacteria or a virus.” Combined with more automated software and higher throughput, this new addition to the core is built to collect better data faster.
Titan Krios G4: Key Specifications
300 kV transmission electron microscope with XFEG (Xtreme brightness) field emission gun
Falcon 4i direct electron detector with Selectris X energy filter
Resolves structures below 2.0 angstrom (Å) – atomic resolution
Optimized for single particle analysis, cryo-electron tomography high-resolution data collection
Automated sample loading for up to 12 grids
Smart EPU, AI-powered data acquisition software
Shared expertise and collaboration
A powerful microscope is only as useful as the team that knows how to operate it – and cryo-EM, for all its capability, is not a simple instrument to walk up to and use. The UNC Cryo-EM Core has spent years making sure researchers don’t have to struggle alone. Collaboration and comprehensive training are what sets the core apart from a simple fee-for-service facility.
Since opening summer of 2019, the core has contributed to over 100 structural maps deposited in the Electron Microscopy Data Bank (EMDB), “spanning multiple labs, multiple departments, multiple protein complexes.” More than 50 researchers have been trained to operate the equipment independently with the current 200 kilovolt Talos Arctica. If the Titan Krios is the giant waiting in the wings, the Talos Arctica is the steadfast guardian already at work. Named for the bronze sentinel of Greek mythology, it has become a cornerstone of the UNC Cryo-EM Core’s training and research efforts.
From problem to structure
Take Matthew Hvasta, a graduate student in Dr. Brian Kuhlman’s lab working on a protein that is a primary target of the immune response during dengue virus infection. While the protein behaved well in solution, it repeatedly failed during cryo-EM sample preparation, interacting with the air-water interface and remaining outside the holes in the grid where particles must be located for imaging. After months of unsuccessful optimization, the CryoEM Core worked closely with Hvasta to troubleshoot the problem. Eventually, Core Director Josh Strauss suggested trying graphene oxide grids fabricated in-house.
“The graphene oxide grids immediately fixed the problem,” Hvasta says. “Josh and his technicians were great to work with throughout the process. They always took the time to talk through experimental problems and come up with unique solutions.”
“We made him graphene oxide grids and then we were able to get structures using this methodology,” Strauss says. “They’ve been using it for designing better vaccines. That was an example of us investing in and developing different sample preparation methods to make available to researchers.”
The solution not only enabled imaging of the original protein but also provided a workflow Hvasta has since used to study multiple protein variants, helping advance vaccine design efforts.
Access at and beyond UNC
That investment extends to everyone – UNC researchers, institutions across the region, and industry alike. Labs from across UNC’s schools and departments use the core regularly, alongside researchers from Duke, NC State, and East Carolina University. Industry partners have come through for nanoparticle characterization and products in development. “Our approach to training people and collaborating with people and having both the fee-for-service model but also being able to work with people on different projects so that they can be successful – we try to be very accessible to researchers that are really interested in cryo-EM,” Strauss says. “We spend a lot of time trying to develop very robust training programs to teach people so that they can become experts and the technology is accessible to people.”
How to get started and what’s coming
The process starts with a simple conversation. “We would set up a consultation to discuss project goals, expectations, and timeline,” Strauss says. From there, researchers can choose between a full-service model – submit a sample, receive data – or a training pathway to operate the equipment independently. The training program covers specimen preparation, microscope operation, and data processing, certified through a standardized rubric and updated every year. “Every person that goes through the training program gets the same attention and also the same training,” Strauss says – whether they are an industry professional, an academic researcher, or a graduate student brand new to the technique.
The core’s investment doesn’t stop at the equipment or the users. “We’re also really invested in the technique and improving it,” Strauss says. “Since the core started we’ve been developing different types of methodologies for specimen prep and imaging to add to the technique.” A new collaboration with Josh Chen in the Chemistry department on microelectron diffraction is already underway, with plans to have it online later this year.
The UNC Cryo-EM Core has spent years doing what good science requires – meeting researchers where they are, working through the hard problems alongside them, and building the kind of expertise that makes the technology incredibly useful.
Sometime this year the Titan Krios G4 will take its place at the UNC Cryo-EM Core – ready, along with the team behind it, to see things that have never been seen before.
Written by Tanisha Choudhury