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  • 1
    Electronic Resource
    Electronic Resource
    Comparison and optimization of smoothing procedures for small-angle X-ray scattering curves. Polynomial fitting and modified frequency filtering (1979)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 267-274 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The filter theory allows one to compare the efficiencies of smoothing procedures widely used in the field of small-angle X-ray scattering. This method is demonstrated for polynomial fitting and modified frequency filtering. Optimized and objective smoothing parameters are determined for both procedures through the knowledge of variance reduction factors, transfer functions of the filters, the largest value of the spatial frequencies of the scattering curve and the distortions caused by the smoothing procedures. The comparison of the efficiency of polynomial fitting and frequency filtering clearly shows the superiority of the latter; therefore, this method has to be preferred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889879012450
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The model resolution function – a technique for estimating the quality of approximation of particles by models in small-angle X-ray or neutron scattering (1985)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 18 (1985), S. 241-247 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Although the quality of a structure model obtained from small-angle X-ray or neutron scattering curves for polymers can be determined qualitatively by comparing the isotropic scattering curve calculated for the model with the experimental scattering data for a solution of polymer molecules, other methods are needed for a more precise evaluation. A model resolution function has been defined to permit quantitative comparisons. With this function, the quality of the approximation can be assessed, and the structure resolution can be determined. An overinterpretation of scattering curves by use of complex but uniform-density models can thus be avoided. Furthermore, the value of the Porod volume calculated from the scattering data has been found to depend strongly on the interval in which the scattering data are recorded or selected for evaluation. The calculations with the atomic model curves showed that it is impossible to compute physically meaningful values of the hydration of the molecules from the Porod volume and the dry volume by use of extrapolated scattering curves with an insufficient resolution. The theory of the model resolution function and the interpretation of the Porod volume have been verified and tested with experimental scattering curves from solutions of RNA molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889885010214
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The database BIOSCAT: a tool for structure research by scattering and hydrodynamic methods (1992)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 25 (1992), S. 803-806 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The crystal structures of a large number of proteins and nucleic acids are known and the corresponding sets of coordinates are stored in the Brookhaven Protein Data Bank. For structure investigations of biological macromolecules in solution, scattering and hydrodynamical methods are powerful biophysical tools when starting the data interpretation on the basis of the crystal structure of the molecules. The database BIOSCAT covers the main structural parameters estimable by X-ray scattering, translation and rotation diffusion methods and the X-ray scattering intensities and low- and high-resolution real-space electron distance distribution functions of 70 biological macromolecules and of oligonucleotides in standard conformation. The parameters and the scattered intensities are calculated from the atomic coordinates using the improved cube method and the real-space functions are estimated via a termination-error-reduced Fourier sine transformation. The database access is organized by the program PASSDB, which can generally be used for `readable' databases. A simple query language allows enquiries into the database without knowledge of a programming language. The program CONVSQL converts the database into normalized relations that can be handled by structured query languages (SQLs).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889892006733
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The highly resolved excess electron distance distribution of biopolymers in solution – calculation from intermediate-angle X-ray scattering and interpretation (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 26-34 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray and neutron scattering provide valuable and specific information about the internal structure of macromolecules in solution. The excess electron distance distribution function of a macromolecule p(r), derived from the scattering by a Fourier transformation, is more directly structurally interpretable than the scattering curve itself. This is especially the case when a set of atomic coordinates is available as a `starting structure' and when the p(r) function is highly resolved. A procedure is proposed for calculation of the high-resolution p(r) function at distances greater than 0.4 nm. To reduce termination errors in the distance distribution function, the difference between the scattered intensity of the molecule, calculated using atomic coordinates, and the scattered intensity of the `independent' atoms of the macromolecule is modified by a Hamming window and then Fourier transformed. A more direct structural interpretation of changes in the highly resolved p(r) function is possible by the correlation of known structural elements in proteins and nucleic acids with main features of the electron distance distribution function via the so-called distance plot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889889010526
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  • 5
    Electronic Resource
    Electronic Resource
    On the calculation of a slit-smeared small-angle X-ray scattering function for coated spheres (1974)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 7 (1974), S. 445-446 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A formula is presented for calculating `infinite-slit' smeared small-angle X-ray scattering curves for concentrically coated spheres of uniform electron densities ρ1 and ρ2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889874010119
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of the largest particle dimension by direct Fourier cosine transformation of experimental small-angle X-ray scattering data (1980)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 13 (1980), S. 280-283 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The largest dimension, L, of a scattering particle is an essential structure parameter of the sample and is necessary both for designing and carrying out experiments and also for analysis of the scattering data. It is shown that L, which is identical to the upper-limit frequency of the scattering curve, can always be evaluated from a Fourier cosine transformation of scattering data which are not corrected for collimation effects, regardless of the shape of the primary beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S002188988001206X
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Bestimmung der Gestalt gelöster Makromoleküle aus Röntgen-Kleinwinkeldiagrammen mit Hilfe von Gleichungssystemen (1969)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 25 (1969), S. 708-710 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: From the small-angle X-ray scattering diagrams of monodisperse dilute solutions of protein molecules or virus particles the moments of the intersect distribution function can be determined. With the aid of a set of equations it is possible to determine the shape of the particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739469001586
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  • 8
    Electronic Resource
    Electronic Resource
    Entschmierung von fehlerbehafteten Röntgen-Kleinwinkel-Streukurven (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 11-18 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The experimentally determined small-angle X-ray scattering curve is approximated by a Fourier series. For smoothing the scattering curve a limit for the correlation range of the difference of the electron density from the average is presupposed. The smoothing, the correction of the slit width error by deconvolution and the differentiation for the correction of slit height error are carried out with the Fourier coefficients. The smeared scattering curve is reconstructed by Fourier synthesis. The method makes it possible to correct scattering curves with random and no-random errors working with digital computers in on-line or off-line technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000032
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  • 9
    Electronic Resource
    Electronic Resource
    Röntgen-Kleinwinkelstreuung von isotropen Proben ohne Fernordnung. I. Allgemeine Theorie (1971)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 27 (1971), S. 193-197 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The spatial correlation function C(x) calculated with the aid of the scattered intensity φ(b) is assumed to be sufficiently convergent for X ≥ L. L is the correlation range of the electron density. Then φ(b) and C(x) may be replaced by a trigonometrical progression φk = φ(k/2X), k = 1,2, 3,..., where X is the upper limit of integration of the Fourier representation of φ(b). C(x) may be determined from φk with the aid of a summation formula. For the non-measurable limit of the scattered intensity at zero angle φ(0) there exists a mathematical representation by the other values φk. The moments Cn of C(x) are also determined by the φk, particularly the radius of gyration and some characteristic quantities are given by rapidly convergent series.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739471000457
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of platinum(II) chemotherapeutic agents on properties of DNA liquid crystals
    Amsterdam : Elsevier
    Biophysical Chemistry 35 (1990), S. 143-153 
    Details
    ISSN: 0301-4622
    Keywords: CD ; DNA liquid crystal ; Liquid-crystalline dispersion ; Optical texture ; Platinum(II) coordination complex ; X-ray crystallography
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0301-4622(90)80004-Q
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