Titan Krios

The Titan Krios are fully automated cryo-electron microscopes from Thermo Fisher Scientific, designed for rapid, stable, high-resolution data collection on frozen-hydrated samples.

Cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET) data can be collected automatically on all four Krios microscopes.

All Krios microscopes are equipped with the latest generation Ametek-Gatan Bio-quantum-K3 detectors, as well as the Thermo Fisher Scientific Falcon III detectors.

Thermo Fisher Scientific's EPU software, with aberration free image shift data collection (AFIS), is primarily used for single particle data collection (SPA) at eBIC. SerialEM is also available on all 4 Krios microscopes for optimal cryo-ET data collection.

All Krios are equipped with Volta style phase plates, greatly boosting low-resolution contrast, facilitating cryo-EM on small proteins and cryo-ET applications.

Benefits for structural biology

• Reduced time to data and reduced cost per structure enabled by automated sample loader and long unattended operation
• Robotic loading of up to 12 frozen-hydrated samples for increased throughput
• Reduced installation and operating requirements: environmental instrument enclosure provides optimal thermal and acoustic shielding
• Optimised connectivity to latest hardware and software developments
• Minimal thermal drift due to ConstantPower™ lenses 

Who should apply for use?

eBIC particularly encourage applications from users with frozen-hydrated specimens that have been optimised in their home laboratories, and which would greatly benefit from the increased data quality and throughput the Krios offers.

Falcon lll (Integrating and counting detector)

• Works at a range of electron doses, so short exposures can be used
• Up to 450 images per hour throughput in integrating mode with AFIS equipped EPU
• Excellent for large complexes above 1 mDa in integrating mode
• Excellent for complexes below 500 kDa in counting mode

Bio-quantum K3 (Counting detector)

• Super resolution can recover information past the Nyquist frequency of the original image
• Counting greatly increases Detective Quantum Efficiency (DQE) at lower spatial frequencies
• Up to 450 images per hour throughput with AFIS equipped EPU
• Excellent for complexes below 500 kDa
• Located behind an energy filter for improved contrast - the preferred detector for
  cryo-tomography applications

Magnification 

Both the Falcon lll and the K3 will provide information at the Nyquist frequency of the image. The most common magnification used on both the Falcon lll and K3 are 1.4, 1.1 and 0.8 Å/pix. Using a lower magnification may not give you more particles as you can not take as many movies per hole which slows down data collection rates.

Hole size

Larger holes in combination with AFIS allow more movies to be collected per hour. For example, with 2 micron holes and a magnification equivalent to 1.1 Å/pixel we can routinely get 3 movies per hole and approximately 300 movies per hour, compared to only 2 movies per hole in 1.3 micron holes and approximately 250 movies per hour.

Loading samples

• Loading up to 4 grids is recommended, which if pre-clipped can take only 15 minutes. If the grids need to be clipped this will add an additional 15 minutes to the loading time.
• Backup samples can be brought to eBIC, if this has been agreed in the proposal - these samples must be listed on the session Experimental Risk Assessment (ERA)
• Local contacts load the Krios once per 48 hour session (for both Block Allocation Group & Rapid sessions)
• Super-users (BAG sessions) may operate the microscope according to their individual accreditation.