Structural Dynamics at LCLS

ABSTRACT: TR&D-2 TR&D-2 tackles the challenges of sample delivery for data collection at the LCLS X-ray FEL. High intensity X-ray FEL beams used to probe sample structure will destroy the sample after exposure to a single X-ray pulse. As a result, experiments at LCLS require a sample delivery system that can replace the damaged sample between every X-ray pulse. Crystal injectors were the first crystal delivery method used for serial femtosecond diffraction and are commonly used at X-ray FEL facilities because they can efficiently deliver a large number of crystals, reduce background scattering and enable new classes of time resolved studies. Sample injectors produce a thin stream of crystals (or sample solution) by ejecting a suspension through a small orifice. X-ray pulses at a high repetition rate interrogate the crystal stream and a diffraction pattern is produced each time a crystal and an X-ray pulse coincide. While it is possible to collect serial data at cryogenic temperatures with rapid scanning fixed target systems, injectors can replenish room temperature samples at even faster rates. Furthermore, many biomedical problems require the unique features offered by sample injectors including methods that use rapid mixing to study biomolecular dynamics. TR&D-2 focuses on advancing injector-based sample delivery methods to enable research following the DBP themes, specifically, solving new structures of membrane proteins and other radiation sensitive biomolecules and enabling the study of protein dynamics including those of metalloenzymes. This will be achieved via the development of remote access capabilities for data collection for Lipidic Cubic Phase (LCP) and other viscous media samples, as well as through the thorough testing and optimization of rapid mixing injectors. TR&D-2 aims to maximize the efficiency in the use of the unique LCLS beam, promoting greater access to biomedical community and new scientific discovery.