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Figure 1
Acoustic droplet ejection (ADE) from a concave agarose pedestal (CAP). ADE uses sound energy to transfer 2.5 nl microdroplets of liquids (such as chemical libraries) or suspended solids (such as mother liquor containing small protein crystals) from a source well, through a short air column (1–10 mm) to a micromesh. Sound energy from the transducer is channeled to the focal point (i.e. ejection zone), displacing the surface, where a controlled ejection occurs. The droplet size is governed by the wavelength of the sound emitted; we used a fixed wavelength to eject chemicals and crystals in 2.5 nl increments. Chemicals are ejected from unmodified source wells. Protein crystals are ejected from source wells that have a CAP with the same chemical composition as the mother liquor of the crystals, ensuring that the crystals remain intact and viable for transfer. Agarose, being acoustically transparent, allows the transfer of most suspended solids (such as crystals) with very high precision onto a standard micromesh. Protein crystals in mother liquor are sequestered in the concave basin and suspended above the dead volume. A 2% agarose solution in the random-coil phase (at 100°C) was mixed in a 1:1 ratio with crystallization conditions for lysozyme, thermolysin, stachydrine demethylase and photosystem II. Wells of a 384-well polypropylene source microplate were overfilled with 70 µl of the agarose and precipitant mixture. To create the concave topography of the pedestal, 40 µl were removed from the wells after a 3 s cooling period.

Journal logoBIOLOGICAL
ISSN: 1399-0047
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