<i>Fourier Methods in Crystallography</i>

Ramachandran, G.; Srinivasan, R.; Stewart, Robert F.

doi:10.1063/1.3070964

Cited by 71 publications

(70 citation statements)

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“…This name is inspired by the term`double-phasing' used by Ramachandran & Srinivasan (1970) in reference to SIR and SAD phasing. The rationale behind the phase-o-phrenia algorithm is that the Fourier transform of a constant function [e.g.…”

Section: Unexpected Symmetrymentioning

confidence: 99%

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On symmetries of substructures

Adams

2003

Acta Crystallogr D Biol Crystallogr

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This paper accompanies a lecture given at the 2003 CCP4 Study Weekend on experimental phasing. With the audience of the CCP4 Study Weekend in mind, an overview is given of symmetries of substructures and the implications for single isomorphous replacement and single anomalous diffraction phasing procedures, as well as difference Fourier analyses. Pointers are also provided to practical tools for working with substructure symmetries.

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Section: Unexpected Symmetrymentioning

confidence: 99%

“…An electron-density map obtained through SAD phasing is a superposition of the true electron density and the negative inverse of the true electron density convoluted with the Fourier transform of exp(2i9 sub ) (Ramachandran & Srinivasan, 1970),…”

Section: Unexpected Symmetrymentioning

confidence: 99%

On symmetries of substructures

Adams

2003

Acta Crystallogr D Biol Crystallogr

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“…Another difficulty lies in the fact that many of the early structure determinations carried out in the Soviet Union were on compounds for which the X-ray crystal structures were already known and, indeed, the atomic positions from these structures were often used to phase the electron-diffraction structure-factor magnitudes to allow the computation of electrostatic potential maps. Since it is well known (Ramachandran & Srinivasan, 1970) that a correct set of crystallographic phases applied to permuted structure-factor amplitudes results in a Fourier map with a recognizable crystal structure, this early work unfortunately failed to answer the skeptical criticism of many other structural crystallographers that the measured electron diffraction intensity data by themselves may not be sufficient for an ab initio structure analysis.…”

Section: Introductionmentioning

confidence: 99%

Electron diffraction structure analysis of diketopiperazine – a direct phase determination

Dorset¹

1991

Acta Cryst Sect A

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Three-dimensional electron-diffraction intensity data from crystalline textures of diketopiperazine (2,5-0108-7673/91/050510-06503.00 piperazinedione) published by B. K. Vainshtein in 1955 [Zh. Fiz. Kim. (1955 are found to be suitable for ab initio structure analysis via conventional direct phase determination based on the © 1991 International Union of Crystallography DOUGLAS L. DORSET 511 estimates of three-and four-phase structure invariants. Of the 289 non-zero reflections found in this data set, 196 with [E I ->0.5 were used to generate triples and quartets to phase 133 reflections correctly. The resultant [001] and [100] zonal electrostatic potential maps reveal an easily identifiable molecular structure and the atomic coordinates are close to the values found in an X-ray crystal structure.

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“…Electron-density syntheses calculated using experimental magnitudes and phases obtained from an available atomic model are known to be strongly biased towards the model, resulting in spurious density features (Raman, 1959;Ramachandran & Srinivasan, 1970;Oppenheim, 1981;Hodel, Kim & Bfiinger, 1992). Significant efforts were made to find a combination of experimental and calculated magnitudes and of calculated phases that reduces this bias (Luzzati, 1953;Main, 1979;Vijayan, 1980;Read, 1986).…”

Section: Introductionmentioning

confidence: 99%

A procedure compatible withX-PLORfor the calculation of electron-density maps weighted using anR-free-likelihood approach

Urzhumtsev¹,

Skovoroda²,

Lunin³

1996

J Appl Cryst

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A program has been developed that uses an R-free-likelihoodbased technique to estimate the errors of phases calculated from atomic models. This technique allows one to obtain realistic estimates when it is applied to refined models. The program reads a file of structure factors in the X-PLOR format and creates a new one that contains information necessary to calculate weighted maps. The output file can be used directly by X-PLOR.

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Fourier Methods in Crystallography

Cited by 71 publications

References 0 publications

On symmetries of substructures

On symmetries of substructures

Electron diffraction structure analysis of diketopiperazine – a direct phase determination

A procedure compatible withX-PLORfor the calculation of electron-density maps weighted using anR-free-likelihood approach

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