Corporate Profile
Simplifying the process of protein crystallography by automation
P
rotein crystallography is a powerful tool for both academic research and the drug discovery industry. Alongside biological studies, knowledge of the 3D structure of a protein can provide important information about its conforma- tion and active site, enabling the design of selective inhibitors during the drug discov- ery process.
Obtaining crystals of diffraction quality poses many difficulties, involving repeti- tive, and often lengthy, trials – varying buffer conditions, precipitants and dilu- tions thereof to find the ideal crystallisa- tion conditions. Historically, crystallogra- phy was restricted to specialists in the field and was thought to be ‘an art’ with success being hidden in the hands of the individual scientist.
In 2000, recognising that automating the accurate manipulation of nano- litre quantities of protein, buffer and precipitating solutions would consid- erably simplify crystalli- sation methods, TTP LabTech launched mos- quito® Crystal. This automated liquid han- dling platform, with its positive-displacement pipette technology, copes with the wide range of viscosities and solu- tion surface ten- sions used in
drop) and microbatch crystallisation tech- niques. Using low-cost disposable tips, mosquito Crystal accurately dispenses nanolitre volumes (25nL to 1.2µL), guar- anteeing zero cross-contamination between samples and maximising the number of potential screening conditions with valu- able and often limited protein sample. Following the success of mosquito Crystal, TTP LabTech also addressed the issue of automating the difficult in meso or LCP technique of membrane protein crys- tallography, launching mosquito® LCP in 2010.
Membrane proteins reside within a lipidic bilay- er and, in order to reduce risks of instability and pre- cipitation, it was suggested that crystallisation is best performed within a lipidic environment. In 1996, a technique known as the lipidic cubic phase (LCP) revolutionised the process of crystallising membrane proteins1. LCP crystallisa- tion is carried out as a two- step process. Firstly the pro- tein is mixed with a lipid, producing a jelly-like, highly viscous material which is followed by the addition of additives and pre-
vapour phase (sitting drop and hanging Drug Discovery World Fall 2011
cipitants to trigger crystallisation. The ability to accurately pipette highly-vis-
cous cubic phase material, which proved to be the main technical issue associated with automating this method, was overcome by the introduction of a unique micro syringe dispensing arm. By employing mosquito Crystal’s positive tip placement technology, mosquito® LCP can accurately dispense nanolitre volumes (25 to 200nL) of this material on to the screening plate. These drops are then rapidly covered with screen conditions using the mosquito crystal pipetting head, minimising risks of evapo- ration or loss of sample integrity. With an optional LCP mixer, TTP LabTech offers a fully automated solution to the in meso (LCP) technique. Not only can mosquito LCP perform these lipidic studies but by retaining all the features of mosquito Crystal, it can also be used for vapour dif- fusion, microbatch and bicelle methods. The successful automation of crystallog- raphy using robots such as mosquito Crystal and LCP has significantly improved the consistency, efficiency and speed of protein crystallography. By maximising the number of screening conditions per protein sample, optimising crystallisation condi- tions and enabling faster scale up, the structural biologist can address complex biological questions quickly and efficiently. The dispensing speed and accuracy of drop-placement of these robots enable plates to be set up in less than two minutes and their ease of use and robust nature makes them ideal for a multi-user environ- ment. These instruments enable crystallog- raphy techniques to be made available not just to a select group of specialist scientists but for use by multidisciplinary teams working in the field of structural and molecular biology.
Reference 1 Cheng, A, Hummel, B, Qiu, H, Caffrey, M. 1998. A simple mechanical mixer for small viscous lipid-containing samples. Chem. Phys. Lipids. 95: 11-21.
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