High-Throughput Automated System for Crystallizing Membrane Proteins in Lipidic Mesophases

Abstract

A high-throughput robotic system has been developed to enable the automatic handling of nanoliter volumes of highly viscous biomaterials for crystallizing membrane proteins using lipidic mesophases. The in meso method introduced a few years ago has produced crystal structures of a number of important membrane proteins. The bottleneck to achieve high throughput automation of this, so-called in meso method, is the handling of nanoliter volumes of the highly viscous cubic phase as part of the crystallization process. The cubic phase sticks to everything that it has contact with and has a tendency to disable dispensing robotic tools. In this paper, we discuss the factors that influence the successful and automatic delivery of nanoliter volumes of the cubic phase. A creative cubic-phase-based coordinate measuring mechanism is presented for controlling the dispensing distance of the cubic phase which is critically important for the successful performance of the system. A mathematical model describing the cubic-phase delivery is proposed and verified. We also present the optimization of liquid handling parameters for the successful and automatic delivery of different precipitant solutions. The performance characteristics of the robotic system in terms of accuracy and reproducibility of delivering nano volumes of highly viscous biomaterials and micro volumes of different precipitant solutions are reported. Note to Practitioners-Automatic handling of nanoliter volumes of highly viscous biomaterials is a practically challenging yet important task in research-and-development activities of biology and drug industry, including protein crystallization. The latter, however, is a key step for determining the structure of the proteins. Only when the structure of the proteins is revealed, can one understand the function of the proteins and/or develop drugs to cure various kinds of diseases. This paper uses a practical project, crystallizing membrane proteins using lipidic mesophases, as an example to develop approaches for automatically handling highly viscous biomaterials. This paper presents the factors that influence the successful and automatic delivery of nanoliter volumes of viscous biomaterials and introduces a new coordinate measuring mechanism using the viscous biomaterials for controlling the dispensing distance of the biomaterials, which is critical for the successful delivery of viscous materials. A mathematical model describing the delivery of viscous material is for guiding the design of practical delivering systems. This paper also presents a number of parameters for successful and automatic delivery of different precipitant solutions which are involved in the biomaterial screening activities in drug development and biological research. A simple and effective computer vision approach for measuring the volume of bio-solutions and biomaterials in the nanoliter scale is presented which is verified by the fluorescence intensity measurement of the delivered samples. The performance of the automatic system developed in terms of accuracy and reproducibility of delivering nanovolumes of highly viscous biomaterials is reported which proves that the proposed approach is not only practically useful but also feasible for many applications