High-Throughput and Automated Protein Crystallography at the Photon Factory

â—‹Masahiko Hiraki Ryuichi Kato Masanori Kobayashi Yusuke Yamada Naohiro Matsugaki Noriyuki Igarashi Yurii A Gaponov Soichi Wakatsuki

For high-throughput protein crystallography, we are developing a fully automated X-ray structural analysis system that consists of several subsystems for protein crystallization, harvesting and freezing crystals, exchanging samples inside a hutch and data acquisition. Obtaining X-ray quality crystals might require setting up thousands of crystallization trials on different conditions for protein solutions and precipitants. To this end, we have developed a large-scale protein crystallization system (PXS) that allowed efficient crystallization trials of large protein complexes and structure-based drug design. It includes a dispensing system using disposable tips which are specifically designed for high dispensing accuracy, an observation system for acquiring images of drops according to a pre-programmed schedule and storing them to a file server, incubators and a plate-carrying robot. Users can access the file server from anywhere in the world through a Web browser for checking the status of their crystal growth. Protein crystals which have grown large enough for X-ray diffraction experiment are harvested using cryo-loops and plunged into liquid nitrogen. In order to pick up a frozen crystal from a Dewar and mount it onto a goniometer on an X-ray diffractometer automatically, we have installed two sample exchange robots based on the SAM (SSRL Automated Mounting) systems at our insertion device beam lines BL-5A and AR-NW12A at the Photon Factory. In order to reduce the time required for sample exchange further, a prototype of a double-tong system was developed. As a result of preliminary experiments, the sample exchange time was successfully reduced from 70 seconds to 10 seconds excluding the time required for pre-cooling and warming up the tongs.