screen optimisation

Following identification of a condition or set of conditions for successful crystal formation, the aim of the crystallographer is to perform screen optimisation in order to determine the optimal conditions for protein crystallisation, ensuring crystal stability and/ or conformation before scale up studies are carried out.

Screen optimisation involves the study of a range of parameters such as the crystallisation temperature, pH range, precipitants and concentration range of the buffer  which can prove to be a costly and time consuming process requiring the set-up of multiple studies to analyse each individual parameter.

TTP Labtech’s dragonfly crystal is a compact, affordable addition to screen optimisation workflows to eliminate the tedium and complication of plate set-up in screen optimisation assays. With its novel dispensing technology and intuitive software, rapid non-contact dispensing, where each tip can dispense any volume into any well, the risk of cross-contamination is eliminated, ensuring accurate and repeatable results.

Microseeding is another common method employed in crystal optimisation. Here a submicroscopic crystal seed is removed from one condition where the level of supersaturation is high, to a similar condition at a lower level of supersaturation. In order to have lower levels of supersaturation the protein or the precipitant concentration can be lowered in a crystallisation set-up.

The determination of optimal conditions for successful crystallisation during the seeding process can be extremely time-consuming. Setting up plates with varying salt, buffer and precipitant ratios and concentrations for the crystal optimisation process can be tedious, repetitive and complicated.

mosquito crystal and mosquito LCP enable easy addition of extremely low volumes of seed stock and screen solution to the protein drop to enable rapid elucidation of ideal scale-up conditions. mosquito’s ability to multi-aspirate not only provides “in tip” mixing but also gives additional benefits by reducing the minimum dispense volume from 25 nL to 10 nL. Its use of disposable positive displacement tips mean that they will never clog when handling the seed stock ‘paste’.

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