CMOS - Shutterless Operation Boosts Speed and Quality

CMOS technology based X-ray detectors offer numerous advantages compared to traditionally used CCD detectors: · CMOS sensors are available in larger sizes with a pixel size optimized for X-ray scattering and X-ray diffraction. · CMOS sensors have lower power consumption than CCDs and provide excellent signal-to-noise ratios even when only moderately cooled. This allows the design of air-cooled detectors. Both, low power consumption and no need for cooling-water, lead to minimized pre-installation requirements. · While CCDs use a bucket brigade read-out, CMOS technology does allow continuous direct sensor read-out. These features make modern CMOS based X-ray detectors, such as the PHOTON 100, an excellent solution for single crystal X-ray diffraction (SC-XRD) experiments. In particular, the capability to continually read out pixels provides a new approach for data collection. While CCDs require closing the shutter for each read-out step, introducing system overhead, CMOS based detectors can be operated in shutterless mode, which not only eliminates over-head time but it also reduces mechanical jitter. We will present details on the implementation of shutterless readout in the current state-of-the-art SC-XRD instrumentation, the D8 QUEST and D8 VENTURE systems. Furthermore, the impact of shutterless read-out on data quality and data collection speed will be discussed using examples from chemical crystallography and structural biology.

Light-Atom Structures: Absolute Configuration Determination and Beyond

The determination of the absolute configuration for light-atom structures is central to research in pharmaceuticals and natural-product synthesis [1]. In the absence of elements heavier than silicon, it is often problematic to make a significant assignment of absolute configuration. Traditionally, heavy-atom derivatives were prepared which have a stronger anomalous signal compared to the native compound. However, this is not always feasible. The assignment of the absolute structure of pure organic compounds has become somewhat easier with the advent of high-intensity microfocus sources [2], as the increased flux density improves the anomalous signal through improvements in counting statistics. In order to maximize the anomalous signal, X-ray sources with Cu anodes are usually used for the absolute structure determination. However, these data are usually limited to a maximum resolution of about 0.80 Å. High-brilliance microfocus X-ray sources with Mo targets enable the collection of high quality data beyond 0.40 Å within a reasonable amount of time. This allows not only a more accurate modelling of the electron density by using aspherical scattering factors, but also enables a reliable determination of the absolute structure, despite the significantly lower anomalous signal obtained with Mo Kα radiation. With the recently introduced liquid-Gallium-jet X-ray source unprecedented beam intensities can be achieved [3]. The shorter wavelength of Ga Kα compared to Cu Kα slightly weakens the anomalous signal of a typical light-atom structure. However, due to the shorter wavelength, the highest resolution for the liquid metal-jet source is typically at about 0.70 Å, compared to about 0.80 Å for Cu Kα. Hence, about 50% more unique reflections can be recorded. This clearly improves the structural model and the quality of the Flack parameter. Selected results on the absolute structure and charge density determinations for light-atom structures will be presented.

Bringing Instrumentation to the Undergraduate Laboratory

Efforts to bring crystallography into undergraduate laboratories are often hampered by one principal factor: the available funding. The acquisition of instrumentation has always been the stumbling block to establishing a program of crystallography in the undergraduate curriculum. With the introduction of Bruker's D8 QUEST ECO line of diffractometers, new opportunities arise. The ECO line is an all air-cooled set of instrumentation that lowers initial cost, operating cost, and environmental footprint. The system is configured with molybdenum radiation, and, for the first time in a low-cost instrument, with copper radiation. While molybdenum radiation has long been the dominant wavelength, copper allows access to absolute configuration of light-atom molecules. These instruments are fully capable research instruments, allowing for the demonstration and training of the complete experiment, from crystal selection, to selection of experimental parameters, data collection, and structure solution and refinement. Various levels of automation are available to match the needs and abilities of the students, making these instruments versatile through the entire undergraduate program. The transition from this entry-level system to high-end research instrumentation is transparent and undergraduate students will be well prepared for the next steps in their careers.

Bruker proudly contributes to IYCR

Bruker congratulates the IUCR to the proclamation of the International Year of Crystallography (IYCR). As one of the world's leading analytical instrumentation companies, Bruker enthusiastically supports the IYCr activities to increase public awareness of the science of crystallography with a variety of activity. In addition to a direct donation to the IUCR our customers participate in the IYCR's Openlab initiative with state-of-the-art instrument in Pakistan, South Africa, United Arab Emirates and Vietnam. During the entire year Bruker supports meetings and conferences and organizes workshops and user meetings to inspire new blood as well as old hands. In countries with a small base of installed instruments Bruker contributes to the OpenLab initiative loaning a complete for the entire year 2014. Education and research at sites in Ivory Coast, South Africa, Morocco, Indonesia & Brazil benefit from this single crystal X-ray diffraction solution. The system is covered by a free-of-charge service contract and warranty. Personnel from each site receive training prior to the arrival of the instrument and get unlimited support by Bruker's service desk. Bruker is happy to contribute with knowledge, instrumentation and sponsorship to the success of the IYCr all over the planet. We are convinced that the combined efforts of the global crystallographic community demonstrate the importance of crystallography in most technological developments and increase interest in this interdisciplinary method. The talk will provide an summary on the events held, the impact achieved and provide an outlook on activities planned for the remaining IYCR.