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  • 1
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 495-497 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 496-502 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: LAUEGEN version 6.0 is a significantly developed version of the original LAUEGEN program [Campbell (1995a). J. Appl. Cryst. 28, 228–236]. It is an X-Windows-based program which now carries out the stages of processing Laue diffraction data up to and including the integration of spot intensities. The integration routines have also been incorporated in a stand-alone integration program INTLDM. The programs are distributed as part of the Daresbury Laboratory Laue Software Suite.
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  • 3
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 2 (1995), S. 27-30 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: In the Laue diffraction pattern, 10–-20% of the spots result from the exact superposition of two or more reflections that are `harmonics', e.g. hkl; 2h 2k 2l, ...; a high proportion of these are low-resolution reflections. For the solution of large or difficult structure problems, the intensities of the remaining 80–90% of the reflections, measurable as singles, may not be sufficient and thus the evaluation of the intensities of the components of the multiple spots is important. A new procedure, DECONV, for this deconvolution using real-space density modifications on the Patterson map is given. This development is based on a procedure in reciprocal space related to direct methods [Hao, Campbell, Harding & Helliwell (1993). Acta Cryst. A49, 528–531]. A Patterson map is calculated using single reflections and modified by removing negative densities and squaring with an appropriate adjustment at the origin peak. The procedure can be repeated until convergence is reached. It has been tested with Laue diffraction data from 4Zn insulin and cytochrome c peroxidase (CCP). 304 and 1134 reflection intensities were evaluated from multiple spots of insulin and CCP, respectively; the mean fractional differences (on F), showing the agreement with high-quality monochromatic data, were 0.27 and 0.21, respectively.
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  • 4
    Electronic Resource
    Electronic Resource
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 4 (1997), S. 214-222 
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 Å3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or 1 = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.
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  • 5
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Developments in electronic area detectors such as CCDs and image plates have transformed the capability of the synchrotron Laue protein crystallography technique compared with film. The rapid readout of CCDs makes practical the use of rather fine angular interval settings of the crystal between each Laue exposure and a large overall angle coverage. The use of the ESRF CCD (image intensifier type) presented here in the Laue data collection on ESRF ID09 (the `Laue beamline') from a single crystal of the 34 kDa wild-type hydroxymethylbilane synthase (HMBS), space group P21212 a = 88.06, b = 75.73, c = 50.35 Å, yielded 47 Laue exposures in 2.5° angle intervals from a single crystal. The data processed by the Daresbury Laue software is highly complete (∞–2dmin = 77.5%; 2dmin–dmin= 91.7%) to 2.3 Å with high redundancy (11.2). Comparison with calculated structure factors and careful analysis of the Laue geometry shows that between ∞ and 5dmin better completeness still should be possible, which can ideally be realized from CCD detector dynamic range hardware improvements and/or software algorithms to integrate saturated spot profiles. Prospects for Laue diffraction data collection using yet faster detectors such as the `pixel detector' to study irreversible catalytic structural processes in a crystal, the most challenging of all time-resolved experiments, are bright.
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 43-48 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Successful integration of the spot intensities on a single-crystal X-ray diffraction image depends on the ability to predict the spot positions accurately throughout the image. In some image-plate systems, there are spatial distortions, resulting from imperfections in the scanning system, for which corrections need to be made before a satisfactory match between observed and predicted spot positions can be achieved. A procedure to correct for this spatial distortion as part of the refinement procedure used in processing Laue diffraction data is described. The spatial distortion is modelled using polynomial functions. For the test and other images considered, with a pixel size of 88 μm, the root-mean-square (r.m.s.) deviations between the observed and predicted spot positions were reduced from up to 1.4 pixels to 0.4 pixels or less for the 400 or so spots used in the refinements and good predictions throughout the images were obtained.
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 228-236 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: LAUEGEN is an X-windows-based program for carrying out the initial stages of processing Laue diffraction data. It incorporates facilities for image display and measurement, simulation of Laue diffraction patterns, determination of the crystal orientation and refinement of the orientation and other variable parameters to obtain a good fit between predicted and observed spot positions in preparation for the integration of the spot intensities. The program is distributed as part of the Daresbury Laboratory Laue Software Suite.
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 447-450 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The parameters dmin and λmin, essential for the processing of synchrotron X-ray Laue patterns, can be efficiently estimated by examination of the distribution of measured intensities as a function of d spacing and wavelength, respectively. A procedure that can be carried out automatically as one step in the data processing has been tested with Laue data sets from an organometallic compound and two proteins.
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  • 9
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Image plates have advantages over photographic films, which include wider dynamic range, higher detector quantum efficiency, reduced exposure time and large size. In this study, an on-line image-plate system has been used to record crystallographic data from a small crystal. In particular, synchrotron Laue data were recorded with λmin = 0.455, λmax = 1.180 Å, in 20 images 10° apart and with an exposure time of 0.3 s each from a crystal (0.02 × 0.05 × 0.25 mm) of a nickel-containing aluminophosphate, NiAPO. The Laue data were analyzed with the Daresbury Laue software, including the application of an absorption correction. The structure was solved by a combination of the Patterson method and successive difference Fourier calculations using SHELXS86 and SHELXL93; the final R value for 1934 unique reflections (all data) and 310 parameters was 7.90%. The structure agrees with that determined by monochromatic diffractometry using the same crystal and reported by Helliwell, Gallois, Kariuki, Kaucic & Helliwell [Acta Cryst. (1993), B49, 420–428] with an r.m.s. deviation of 0.03 Å. Hence, this study shows the image-plate device to be very effective for synchrotron data collection and subsequent structure analysis from small crystals, i.e. 0.02 × 0.05 × 0.25 mm, in chemical crystallography as well as providing further confirmation of the practicability of Laue data in structure solution and refinement.
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  • 10
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Transmission Laue diffraction photographs can be recorded with short exposure times from stationary macromolecular and small-molecule crystals. With the use of a broad wavelength band a very large number of reflections is stimulated in a single `snapshot' of large regions of reciprocal space. Processing software has been developed which allows quantitation of the Laue data without resort to monochromatic data. The procedures have been developed and the software strategies optimized by using test data recorded on the SRS wiggler from a protein, pea lectin, and small-molecule crystals. These latter include an organic molecule, trimethyl-1H-2,1,3-benzophosphadiazine-4(3H)-thione 2,2-disulfide, referred to as BPD, and a rhodium complex, [Rh6(CO)14(dppm)], where dppm is Ph2PCH2PPh2, referred to as RHCOP. Monochromatic data were available for comparison.
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