Phase determination and Patterson maps from multiwave powder data

Prandl, W.

doi:10.1107/s0108767390008819

Cited by 29 publications

(19 citation statements)

References 7 publications

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“…Nowadays, we can separate, e.g. by anomalous (resonant) scattering contrast, the partial structure amplitudes of one atomic species from those for the rest of the structure (Karle, 1980;Hendrickson, 1985;Prandl, 1990) and high-speed computing is available at our desks.…”

Section: Coefficients Of the Polynomial R(c) Coefficients Of The Polymentioning

confidence: 99%

“…Hence, we assume a monoatomic crystal structure (or a partial structure of atoms designated 'a'). Partial structure amplitudes IFal or IF21 can be separated (Karle, 1980;Hendrickson, 1985;Prandl, 1990) if the a atoms are anomalous scatterers (as widely used in MAD techniques). The representation of atoms by points with unit weight is achieved by reducing lEVI (or IF.I) according to…”

Section: Preliminaries Requirementsmentioning

confidence: 99%

See 1 more Smart Citation

Solving Crystal Structures without Fourier Mapping. I. Centrosymmetric Case

Pilz¹,

Fischer²

1998

Acta Cryst Sect A

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Table 1. List of symbols and definitions A recursive algebraic procedure for solving onedimensional monoatomic crystal structures is presented.(If applied to projections, also a three-dimensional atom arrangement may be reconstructed.) Moduli of h, i, j, k, l, n the geometrical parts of the corresponding structure N factors serve as experimental input. The atom coordi-m nates are found from the roots of a polynomial. For a space group Pi with m atoms in the asymmetric unit, f(x, sin0/)Q the first m + 1 reflections are needed for finding their B signs by means of a determinant technique. Using F Monte Carlo calculations, the influence of the standard Fo uncertainties of the data on the uncertainties of the derived coordinates is simulated. In a similar way, hints F~ for discriminating between sign variations are obtained, gh The resolution in direct space is better than that of a one-dimensional Fourier summation over the same number of reflections. Error-free data provide a unique solution (if homometries are excluded). For data affected by experimental uncertainties, all possible solutions (compatible with the data) are found. Their Sh-S(hkl) number is always finite, and it may be further reduced by employing reflection orders higher than m -t-1. Some s applications of the method are discussed.

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Section: Coefficients Of the Polynomial R(c) Coefficients Of The Polymentioning

confidence: 99%

Section: Preliminaries Requirementsmentioning

confidence: 99%

Solving Crystal Structures without Fourier Mapping. I. Centrosymmetric Case

Pilz¹,

Fischer²

1998

Acta Cryst Sect A

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“…Nevertheless, dispersive differences, due to the variation in f 0 can be measured. The implications of this systematic overlap problem have been discussed by Prandl (1990Prandl ( , 1994, who reached the conclusion that phases can be determined for centric reflections using a single anomalous scatterer but that, for acentric reflections, at least two anomalously scattering species are required. Plö hn & Bü ldt (1986) have also considered the powder phasing problem and also discuss the ways in which D 2 O/H 2 O substitution could be used for labelling with neutron data.…”

Section: Emerging Powder Phasing Methodsmentioning

confidence: 99%

Powder crystallography on macromolecules

Margiolaki

Wright

2007

Acta Cryst Sect A

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Following the seminal work of Von Dreele, powder X-ray diffraction studies on proteins are being established as a valuable complementary technique to singlecrystal measurements. A wide range of small proteins have been found to give synchrotron powder diffraction profiles where the peak widths are essentially limited only by the instrumental resolution. The rich information contained in these profiles, combined with developments in data analysis, has stimulated research and development to apply the powder technique to microcrystalline protein samples. In the present work, progress in using powder diffraction for macromolecular crystallography is reported.

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“…Since its demonstration on polycrystalline materials [76][77][78][79], almost no application of resonant diffraction has been proposed for de novo structure determination of small molecules. This is probably related to the efficiency of conventional crystallography methods for elucidating those crystal structures.…”

Section: Structure Solution and Mad On Macromolecular Powdermentioning

confidence: 99%

X-ray resonant powder diffraction

Palancher

Bos

Bérar

et al. 2012

Eur. Phys. J. Spec. Top.

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Abstract. X-ray resonant diffraction can be applied in structural chemistry studies on powder samples. It enables an important limitation of powder diffraction to be overcome. This limitation is related to the low ability of powder diffraction to differentiate elements with close atomic numbers when they occupy the same or close crystallographic sites (mixed occupancy case) and also to discriminate cations with different valence states in different sites. However the resonant effect usually has a second order influence on the measured intensity. As a consequence, the efficiency of this method directly implies the need for excellent quality data collection and has generally been better assessed on elements present in single phase powder samples. In recent years, instrumental developments have been made in synchrotron radiation facilities which allow easier use of resonant powder diffraction for site-specific contrast and valence i.e. oxidation state analyses. Moreover, resonant contrast diffraction tools also have been proposed for better visualization of the anomalous effect both in direct and reciprocal space by using differences between electron density maps or diffraction patterns. Finally the potentialities of this technique for de novo structure solution on macromolecular systems are mentioned.

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Phase determination and Patterson maps from multiwave powder data

Cited by 29 publications

References 7 publications

Solving Crystal Structures without Fourier Mapping. I. Centrosymmetric Case

Solving Crystal Structures without Fourier Mapping. I. Centrosymmetric Case

Powder crystallography on macromolecules

X-ray resonant powder diffraction

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