journal menu
abstracts
Selenium is the most widely used heavy atom for experimental phasing, either by single anomalous scattering (SAD) or multiple-wavelength anomalous diffraction (MAD) procedures. The use of the single isomorphous replacement (SIR) or single isomorphous replacement with anomalous scattering (SIRAS) phasing procedure with selenomethionine (Mse) containing proteins is not so commonly used, as it requires isomorphous native data. Several non-redundant X-ray diffraction data sets from various Mse derivatised protein crystals were collected at energies far below the absorption edge before and after exposing the crystal to ultraviolet (UV) radiation with 266 nm lasers. A detailed analysis revealed that significant changes in diffracted intensities were induced by ultraviolet irradiation whilst retaining crystal isomorphism. These intensity changes allowed the crystal structures to be solved by the radiation damage-induced phasing (RIP) technique [1]. These can be coupled with the anomalous signal from the dataset collected at the selenium absorption edge to obtain SIRAS phases in a UV-RIPAS phasing experiment [2]. Inspection of the crystal structures and electron-density maps demonstrated that covalent bonds between selenium and carbon at all sites located in the core of the proteins or in a hydrophobic environment were much more susceptible to UV radiation-induced cleavage than other bonds typically present in Mse proteins. The rapid UV radiation-induced bond cleavage opens a reliable new paradigm for phasing at synchrotron [1,2] and at in-house X-ray source [3].
abstracts
MxCuBE, is a beamline control graphical user interface (GUI) for macromolecular crystallography (MX) experiments that was developed by the ESRF and has been in use since 2005. The GUI provides the user with a friendly interface to electronic devices, permitting to carry out experiments in a intuitive environment while benefiting from the increasing automation. Since its release, MxCuBE has become the preferred MX data acquisition software, also installed at other European synchrotron sites [SOLEIL, EMBL@PETRAIII, BESSY and MAXLAB].In September 2013, after intense recoding, experiment design and testing, the ESRF has deployed MxCuBE2 on all the ESRF's MX beamlines. This new generation of GUI is capable of interfacing with a variety of low level control systems. MxCuBE2, written in the Python programming language, has a radical new appearance and provides an updated environment for performing complicated multi-crystal/multi-position MX experiments in a modular, logical and automatic fashion. ISPyB is a Laboratory Information Management System (LIMS) conceived to record experimental parameters and basic reporting of the data obtained. Since 2009 ISPyB has been a collaboration between ESRF and Diamond Light Source (DLS) and the LIMS is now a multi-site, generic system for synchrotron-based (MX) experiments. The current version allows users to track their sample location (to/from & at the synchrotron), facilitates transmission of information from and to other LIMS, records experiment details, and provides the results - including reflection files - of automatic data processing protocols. Indeed as experiments have become more complex and automated ISPyB has become more than just a repository for project histories - it has become a support for rapid decision making during experiments. The combination of these two indispensable tools in every day users life at the European Synchrotron Radiation Facility will be presented and discussed.
