![]() Future developments and projections based on multipole sources are given. In the latter case, the data were used in a difference Fourier calculation which showed the mercury peak. In both the pea lectin and mercury derivative cases, doublet Laue spots were deconvoluted. To assess the use of a vertically focussing mirror, we have successfully used a mercury derivative protein crystal to yield isomorphous and anomalous differences suitable for phase determination. In order to assess the efficacy of the Laue method for quantitative crystallography, we have used Laue data from the protein pea lectin and compared it in detail with monochromatic pea lectin data. Laue diffraction uses white Bremsstrahlung instead of monochromatic radiation. We performed initial experiments using a direct detection CCD imager, and have obtained satisfactory diffraction data on a 40 ms time scale. This will allow tight control of parasitic scatter for microcrystal Laue diffraction and real‐time monitoring for time‐resolved work. The attraction of using the CCD, even to look at a small portion of the Laue pattern, is to view the diffraction in real time. To date, we have processed Laue film data successfully. It is useful to consider the joint theoretical spatial and energy distribution of spots in defining the detector specification and geometry. The detector options used to date have been photographic film, Fuji image plate (at Photon Factory)/Kodak storage phosphor (at Cornell) and charge coupled device (CCD) (at Daresbury). A mirror can be usefully introduced to enhance the multiplicity distribution in favor of single wavelength spots or to focus the white beam so far only vertical focussing has been used. λ min is determined either by the spectral curve or a critical cutoff if a mirror is used. λ max is determined by the use of any filters in the beamline. This distribution is determined by the ratio λ max/λ min (λ max =maximum wavelength, λ min =minimum wavelength in the beam). The multiplicity distribution is the histogram of the number of spots of a given order. The fact that different equivalents occur at different wavelengths means that the differences in these intensities can be used to establish the ‘‘λ curve.’’ Successful wavelength normalization to date has used a relatively broad‐band pass. This can be achieved by using the symmetry of the diffraction pattern. For neither space group does the axial choice. Possible space groups are Pcn 2 (30) and Pcnm (53). Table 3.1.4.1 shows that the diffraction symbol is mmmPcn. The diffraction spots are indexed such that the reflection conditions are. In addition, empirical wavelength normalization is required. The diffraction pattern of a compound has Laue class mmm. It can be shown that the bulk of the Laue spots are single order, provided d h k l<2 d min where d h k l is the interplanar spacing and d min is the resolution limit of the data. The so‐called ‘‘overlapping orders problem’’ has been found not to be limiting. The use of Laue geometry as a means of quantitative data acquisition required the solution of some fundamental problems. In the latter case especially, there is a critical need to control parasitic scatter in the Laue camera. Alternatively, this gain factor can be used instead to reduce the sample volume for a fixed exposure time. Journal of Physics D: Applied Physics 50, 373001.Single‐crystal x‐ray diffraction data can be measured very quickly in Laue geometry compared with monochromatic methods. (2017) Watching proteins function with time-resolved x-ray crystallography. Time-resolved crystallography principles and practice at BioCARS and LCLS.Journal of Synchrotron Radiation 18, 658–670. (2011) BioCARS: a synchrotron resource for time-resolved X-ray science. Infrastructure for time-resolved crystallography at BioCARS 14-ID beamline.(1999) Laue crystallography: coming of age. Laue technique and examples of applications.For comprehensive reviews of time-resolved crystallography at BioCARS we suggest the following: Time-resolved pump-probe experiments at BioCARS utilize polychromatic, Laue X-ray diffraction technique. BioCARS is one of only several synchrotron beamlines worldwide with infrastructure for conducting time-resolved experiments. Time-resolved crystallography is a unique tool for achieving this goal because it provides direct, detailed and global structural information as molecules in the crystal undergo structural changes.īioCARS scientists played essential role in the early development of all aspects of time-resolved crystallography, including advances in processing and analysis of time-resolved data. While standard static 3-D structures of macromolecules obtained by using X-ray diffraction technique provide important insights into their function, to fully elucidate details of how these molecules perform their function, one ideally needs to capture them in action. ![]()
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