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  • 1
    Electronic Resource
    Electronic Resource
    Post-refinement of oscillation diffraction data collected at a synchrotron radiation source (1986)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 19 (1986), S. 134-139 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: `Post-refinement' is a technique used to compare the intensity of partially recorded reflections on oscillation photographs with their full intensity observed elsewhere on the same or a different film. A reflection's partiality depends on crystal orientation, crystal cell dimension and crystal mosaicity, and post-refinement is a very sensitive tool for the refinement of these parameters. A previous paper [Rossmann, Leslie, Abdel-Meguid & Tsukihara (1979). J. Appl. Cryst. 12, 570–581] describes how post-refinement can be applied to data derived from a set of oscillation films. In this paper the technique has been extended to the refinement of anisotropic beam divergence and wavelength dispersion as is normally found on synchrotron sources. In an example it is shown that post-refinement is sufficiently sensitive to detect small wavelength variations due to changes in temperature of the monochromating crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889886089793
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  • 2
    Electronic Resource
    Electronic Resource
    Two open-flow cryostats for macromolecular crystallography (1994)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 27 (1994), S. 133-139 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Two open-flow cryostats for macromolecular crystallographic studies, which make it possible to freeze macromolecular crystals very rapidly and maintain them for long periods of time at reduced temperatures, have been constructed. Both systems avoid the use of opaque shrouds and hence permit monitoring of the optical properties of protein crystals at all temperatures. The first uses a cold-gas stream derived from boil-off of liquid nitrogen, with a surrounding warm-gas stream, and covers a temperature range of 80 K to room temperatures. The second uses a cold-gas stream derived from boil-off of either liquid helium or liquid nitrogen to cover a temperature range of 10 to 70 K or above 80 K, respectively. Special care has been taken to make it possible to switch back and forth between the two cryogenic liquids in routine operation. The temperature stability of the cold-gas stream is ±0.5 K, which is achieved by controlling both the flow rate of the gas stream and the power of a heater within the cold-gas stream prior to its exit from the nozzle. The liquid helium consumption is less than 21 h−1 at a working temperature of 40 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889893008519
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative Analysis of Time-Resolved Laue Diffraction Patterns (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 29 (1996), S. 246-260 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Integration and quantification of time-resolved Laue images poses problems beyond those encountered with static Laue images. The flexible analytical profile-fitting technique [Ren & Moffat (1995). J. Appl. Cryst. 28, 461–481] has been extended to handle the integration of multiple-spot images with two or more exposures at different time points superimposed on a single detector flame but displaced by a small shift. Each Lane pattern on a multiple-spot image can be integrated separately; possible spatial overlaps between adjacent spots from either the same or different exposures can be resolved; streakiness and streakiness anisotropy are allowed to be different for each time point. Various strategies for time-resolved Lane diffraction data collection and processing are compared. Time-resolved Lane images obtained during the relaxation of photoactive yellow protein (PYP) from its photostationary state have been processed by the Laue data reduction package LaueView. Continuous laser illumination of PYP crystals establishes a photostationary state and termination of laser illumination starts a relaxation process. However, PYP crystals at the photostationary state are more anisotropically mosaic than those at the ground state, and the mosaicity and its anisotropy vary during the relaxation. Accurate integration of elongated and spatially overlapping spots therefore becomes more difficult. Two data processing strategies have been applied to calculate time-dependent difference Fourier maps of PYP. The first route takes advantage of both the wavelength normalization and the harmonic deconvolution [Ren & Moffat (I 995). J. Appl. Cryst. 28, 461–481, 482–493] algorithms. The second is the method of relative percentage changes of structure-factor amplitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889896000659
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  • 4
    Electronic Resource
    Electronic Resource
    Cooling Rates During Flash Cooling (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 252-257 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Flash cooling of macromolecular crystals was investigated by measurement of the cooling rates achieved by different cryoprotectant solutions (glycerol, sucrose and polyethylene glycol) with different sample volumes (0.2–0.8 mm3) and by different cooling agents (cold nitrogen or helium gas, liquid nitrogen and liquid propane). Samples were not cooled instantaneously; it usually took 0.5 to 1 s to reach the glass transition temperature and 1 to 2 s to reach the final temperature. The cooling rate varied from 5̃0 to 700 K s−1 depending on the volume of the sample, the cooling agent used and the temperature at the time of measurement. The cooling rate may affect the distribution of unit-cell dimensions, structural states and the average structure throughout the volume of the crystal, and hence its mosaic spread.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897009229
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitive analysis of Laue diffraction patterns recorded with a 120 ps exposure from an X-ray undulator (1992)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 25 (1992), S. 414-423 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray Laue diffraction patterns with an exposure time of 120 ps have been obtained from single crystals of an indole alkaloid and of the enzyme lysozyme using the X-rays emitted as a single bunch of electrons traverses a hard X-ray undulator inserted in CESR, the Cornell Electron–Positron Storage Ring. The patterns were recorded on a sensitive storage-phosphor detector. Despite complexities posed by the sharp variation of the incident X-ray spectrum with wavelength and the weakness of the diffraction patterns, accurate crystallographic structure amplitudes were extracted from the Laue intensities by the generalized scale-factor approach to the determination of the wavelength- and position-dependent correction factors. The results show that crystallography is feasible on the 100 ps time scale and open up the prospect of time-resolved measurements of ultra-rapid changes in molecular structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889891014826
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  • 6
    Electronic Resource
    Electronic Resource
    Deconvolution of Energy Overlaps in Laue Diffraction (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 482-494 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The energy-overlap problem in Laue diffraction often makes a Laue diffraction data set incomplete in a systematic way: low-resolution reflections more commonly overlap with other reflections than do reflections at higher resolution. We describe the development and testing of a harmonic deconvolution procedure that resolves energy overlaps accurately and is based on the wavelength-normalization curve obtained from single reflections. The conditions for satisfactory harmonic deconvolution are identified by examination of a series of data sets that differ in their redundancy. This procedure has been incorporated in the software system LaueView [Ren & Moffat (1995). J. Appl. Cryst. 28, 461–481]. Results on Laue data sets from crystals of lysozyme and α-haemolysin demonstrate that Laue data sets can be more than 90% complete even at 10 Å resolution and that structure amplitudes derived from these deconvoluted multiples can be as accurate as those derived from the best monochromatic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889895003219
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  • 7
    Electronic Resource
    Electronic Resource
    Feasibility and Realization of Single-Pulse Laue Diffraction on Macromolecular Crystals at ESRF (1996)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 3 (1996), S. 65-74 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Laue diffraction patterns with an exposure time of ca 60 ps have been acquired at the European Synchrotron Radiation Facility (ESRF) on protein crystals by using the single-bunch mode of the storage ring. A 10 ns laser pulse initiating photodissociation was synchronized with the X-ray pulse. The potential for a quantitative detection of conformational changes in proteins on the nanosecond timescale with this technique is demonstrated using the example of carbonmonoxymyoglobin, from simulations and real data. The instrumental aspects of the experiment (highly intense X-ray beam, fast shutter system, Laue camera, detector, laser apparatus and synchronization technique) are emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090904959501661X
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  • 8
    Electronic Resource
    Electronic Resource
    Laue diffraction from protein crystals using a sealed-tube X-ray source (1991)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 146-148 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: It is shown that Laue diffraction patterns may be obtained from a protein crystal using the continuous radiation emitted by a tungsten sealed-tube X-ray source and that precise structure amplitudes may be extracted from these patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889890010846
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  • 9
    Electronic Resource
    Electronic Resource
    Quantitative Analysis of Synchrotron Laue Diffraction Patterns in Macromolecular Crystallography (1995)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 28 (1995), S. 461-481 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The reduction of X-ray diffraction data obtained by the Laue method to accurate integrated intensities is more complicated and much less familiar than the reduction of monochromatic data. Problems of data accuracy and completeness have hindered the wide use of the Laue technique in macromolecular crystallography. Its unique advantage, data-collection speed, has been exploited only in situations such as fast time-resolved crystallography, to which monochromatic techniques are not as well suited. This paper reviews the major problems in data reduction in the Laue technique and provides a unified solution to the problems in integration of both streaky and spatially overlapping spots and data scaling. This solution has been incorporated into a new Laue diffraction data-reduction software package, LaueView. Laue data sets from crystals of lysozyme and α-haemolysin have been processed to test this solution, and demonstrate that Laue data sets can be reduced to yield structure amplitudes of at the very least the same quality as the best monochromatic data sets in terms of both accuracy and completeness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889895003207
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  • 10
    Electronic Resource
    Electronic Resource
    Time-Resolved Crystallography (1998)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 833-841 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Time-resolved crystallography has been successfully applied on the time scale from seconds via milliseconds and nanoseconds to picoseconds on a variety of systems. This brief review largely deals with macromolecular systems, on which there has been substantial recent progress. The strategies for design of a successful experiment that eliminates or minimizes potential artefacts have been identified, and the specifically crystallographic components of these strategies have been implemented. The remaining computational challenge is to identify and extract time-independent structures, each corresponding to a distinct reaction intermediate, whose populations vary with time and give rise to the time-dependent X-ray diffraction data. The fourth dimension, time, has been added to the three spatial dimensions of crystallography; it can no longer be regarded as purely a static technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767398010605
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