During our recent MicroED webinar, we answered many great questions from the audience. Here is a collection of replies from Sacha De Carlo, DECTRIS Business Development Manager, to quench your thirst for knowledge about using DECTRIS detectors in Micro Electron Diffraction.
What is the advantage of using a DECTRIS detector for MicroED?
“In view of the fact that more automation is required for high-throughput workflows in EM, the advantages of a DECTRIS detector are direct detection, shutterless operation, high dynamic range, and radiation hardness. These advantages provide the necessary speed and data quality for MicroED and an optimal user experience.
We think that the detector should not be a limiting factor for high throughput, so our readout speed of over 2,000 frames per second and the absence of dead time let the detector adapt to different manufacturers’ sample stages. Regarding dynamic range, our two 16-bit counters in each pixel mean true electron counting and a 32-bit dynamic range. When it comes to standing up to radiation, DECTRIS detectors require no beamstop whatsoever!”
Is the detector compatible with products made by different EM manufacturers?
“Yes. We use standard interfaces for several EM manufacturers, where the bottom-mounted, on-axis position is free and not already occupied by an energy filter or spectrometer.”
What is the advantage of ED over XRD?
“Electron Diffraction is not really a separate alternative, but a complementary technique in cases where crystal volume is the limiting factor.”
Can we determine the chirality?
“We now know that the chirality can be determined (Ma et al., http://doi.org/10.1038/nmat4890), and it is simply a matter of refinement to prove the same for organic compounds.”
We have a 120 kV machine. Is that sufficient, or do we need to have a 200–300 kV instrument?
“The 100–200 kV energy range is ideal for DECTRIS detectors with a Si sensor. However, in principle, a 120 kV electron beam is enough to get good results in electron crystallography. A few MicroED studies have, indeed, already been published by other groups using this lower energy range (e.g. by the Gemmi group in Pisa, http://journals.iucr.org/m/issues/2019/02/00/eh5001/index.html).”
What software do we need to collect data for MicroED?
“DECTRIS has worked with the Boulder 3D Lab to have our detectors integrated into SerialEM. Together with scripts from the Gonen Lab, SerialED can be done within the SerialEM program suite. Alternatively, DECTRIS provides open-source and license-free software for acquisition and visualization over either Python-based scripting or Albula, a flexible GUI available for Linux and Windows. Other academic solutions also exist, such as SerialED from Stockholm University; see Smeets et al., http://scripts.iucr.org/cgi-bin/paper?S1600576718009500.”
When will the detectors be available?
“DECTRIS will launch QUADRO and another, larger detector for MicroED at the M&M show in Portland, August 2019.”