The authors showed that the majority of the 284 commercial crystallization reagents tested, which can include quite viscous liquids, were transferred successfully by this method. Transfer was successful for 93% of the solutions tested, and the majority of the solutions that did not transfer effectively contained >50% 2-methyl-2,4-pentanediol. Overall the coefficient of variation (CV) for the volume transferred (5 nL) was quite good, with 73% of the reagents having a CV of <10%. The authors tried to add various oils onto the drops to minimize evaporation of the drops, but the transfer of the oils was problematic with the acoustic technology.
A diverse set of proteins were tested using the acoustic dispensing method, and the crystals that were obtained at day 15 (Figure) indicate that crystals can be successfully grown using this technique. The authors mention that for one previously uncrystallized protein complex, they were able to obtain crystals and solve the structure using this technique. They were able to obtain satisfactory crystals and solve the structure of their Fab-protein target using just 10 μL of total protein for a series of 20-nL test drops.
It will be interesting to see how easily diverse proteins will crystallize in this nanoliter environment. In particular, this technique could greatly increase the number of conditions that can be tested for proteins in which protein supply is limited. Crystallography can be quite useful for guiding medicinal chemistry optimization during drug discovery, and this technique might make crystal structures more accessible for projects in which protein limitations had previously precluded it.