A UNIQUE APPROACH TO HANGING DROP – TTP LabTech’s mosquito can create up to 288 drops per 96-well plate

TTP LabTech’s mosquito® has a unique approach to automating hanging drop protein crystallography set-ups. This increases the chance of scale-up success as it allows the same technique to be used for both screening and scale-up, which is particularly beneficial for membrane protein crystallographers. It is one of the key reasons mosquito has become the first choice for protein crystallographers along with its accurate positioning, ability to miniaturise crystallography set-ups (with drop volumes of only 50nl to 1200nl) and disposable pipettes which guarantee zero-cross contamination of samples.

Mosquito automates hanging drop plate set-up by aliquoting protein solution from a single source column to all 96 adhesive-free ‘windows’ on a hanging drop plate seal. Then, because mosquito pipettes in columns, it is able to take a column of droplets of solutions from the reservoir plate and place these directly on top of the protein drops to form a mirror image of the reservoir plate. The seal containing the mirror image drops is then inverted over the reservoir plate – so each combined droplet of protein and screen hangs over its corresponding well of reservoir solution. Complete set-up takes under 2 minutes and it does not require a wash step or the creation of a duplicate source plate.

Automating drop set-up allows the researcher to screen more conditions using less sample in a shorter time, with the added advantages of improved accuracy and repeatability.

Mosquito’s precise linear drives and optical sensors achieve positional accuracy better than 0.05mm in the X, Y and Z axes. This, along with the tightly toleranced and relatively short pipette tips, means that drops are placed with a high degree of accuracy on the flat surface of the plate seal, which gives excellent optical properties for both manual and automated imaging. Smaller drops can be used without the worry of protein and screen drops not coinciding. This accuracy also means mosquito can create several multi-component drops per well, even in high-density 96-well hanging drop set-ups. This allows up to 288 drop conditions to be created per plate.

Multi-aspirate protocols also enable mosquito to simply automate additive and seeding set-ups. For protein crystallographers, the “aspirate, aspirate, dispense” capability allows a combination of solutions to be dispensed simultaneously – with additional mixing if required – resulting in perfect drop formation, rapid liquid diffusion and no protein evaporation.

mosquito applies this same accuracy and speed to setting up sitting drop or microbatch screens – without requiring reconfiguration or changes to the instrument head.

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