The FragMAX sample preparation laboratory is located within the BioMAX sample prep area, directly adjacent to the beamline. The lab is equipped with:

  • an Oryx4 crystallisation robot (Douglas Instruments)
  • an Opentrons OT-2 liquid handler for soak plate formatting
  • an Integra MINI-96 pipette for rapid soaking
  • MAXwell, our in-house developed semi-automated crystal mounting system
  • a large collection of loops and pucks for crystal mounting
  • various crystal storage dewars

Crystallisation is typically set up in SWISSci 3-lens or MRC 2-lens sitting-drop plates, although other formats can also be accommodated.

For crystal soaking, we use a programmable 96-channel pipette rather than an acoustic liquid dispensing device. In brief, a suitable soaking buffer is first added to the fragment stock plates. Suitable crystals are then identified by manual inspection, after which the fragment plates are reformatted using our Opentrons liquid handler so that fragment solutions are in the corresponding positions of the selected crystals. Finally, 1–2 µL of soaking solution are added directly to the crystal drops using the 96-channel pipette. While soak plate preparation with the OT-2 is comparatively slow, it is highly robust, and the actual crystal soaking itself takes only seconds.

This setup offers two main advantages. First, soaking can be performed both at 4 °C and at room temperature, as the pipette can be easily moved between environments. Second, the larger drop volumes allow additional experimental adjustments, such as controlled pH changes through the addition of suitably concentrated buffers.

We have developed our own semi-automated crystal mounting device, MAXwell, inspired by the original Crystal Shifter design (Wright et al., 2021). Whenever possible, crystal mounting is carried out at room temperature; however, for temperature-sensitive crystals, soaking and mounting can also be performed in the cold room. The entire workflow is supported by FragMAXdb, a project database system that tracks samples and metadata from protein batch to structure refinement. This ensures that critical experimental information is preserved throughout the project. Metadata such as fragment concentration, solvent composition, soaking time and chemical conditions are comprehensively recorded and linked to each dataset.