Why Sandwich Boxes? They allow one to use very, very large drops. Drop sizes up to 800 microliters are possible with the Sandwich Box Setup. They are optically superior to plastic plates and glass slides, and offer different equilibration kinetics than other crystallization plates. Each of the Sandwich Box components can be washed and reused so there is little waste with the Sandwich Box Setup. These plates can be used during screening and optimization, but are best suited for final optimization and production of crystals. Since the glass plates can be removed from the boxes, crystal mounting is convenient. The siliconized 9 well depression plates are also useful for heavy atom soaks, cryo solution dilution and transfers, and seeding experiments where serial dilutions are involved. Sandwich Box Setups are available as a complete set or as individual components so one can customize the system to meet their needs. Square cover slides can be used to seal individual reservoirs but are not typically used in a crystallization setup.
The Sandwich Box Setup consists of a square plastic box (4 5/16” x 4 5/16” x 1 1/8”), a polystyrene plate support, and a siliconized, glass plate (4” L x 3 3/8” W (100 mm x 85 mm)) with nine concave depressions (7/8” O.D. x 1/4” D (22 mm x 7 mm)).
When setting up a Sandwich Box, one pipets 25 ml of crystallization reagent or dehydrant into the bottom of the Sandwich Box, then places a support into the box. The 9 well depression plate is placed upon the support. Drops of sample and reagent are pipetted into the depressions and the lid of the Sandwich Box is sealed closed with vacuum grease.
Image credit: Tobias Tandrup, Leila Leggio, and Flora Meilleur. Joint X-ray/neutron structure of Lentinus similis AA9_A at room temperature. Acta Crystallographica Section F, Volume 79, Part 1, Pages 1-7, January 2023. DOI: 10.1107/S2053230X22011335 Figure 2. Octahedral crystal of hydrogenated LsAA9_A grown from 100 µl sitting drops.
Tandrup et al report the crystal structure of Lentinus similis AA9_A from data sets collected at room temperature using both neutron and x-ray diffraction in the Journal Acta Crystallographica Section F, Volume 79, Pages 1-7, Published January 2023. LsAA9_A crystals were obtained using the Sandwich Box setup at 10 degrees Celsius. The Sandwich Box setup allowed the use of large 100 uL drops equilibrated against a reservoir solution of 3.0 M Sodium chloride and 0.1 M Citric acid pH 3.5.
