Phase assignment to diffraction patterns based on the analytic properties of scattered fields applied to the structure of nerve myelin

Burge, R. E.; Fiddy, Michael A.

doi:10.1107/s002188988100976x

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…(b) The use of sigma 1 triples, which must be done more cautiously than the evaluation of the Y2 phase sums, seems to be governed, in part, by the envelope of normalized IE.I in Figs. 1 and 3, reminiscent of the search for "intensity zeroes" when using bilayer swelling techniques to phase x-ray diffraction data (Burge and Fiddy, 1981). For example, within the first low angle intensity region, it is often possible to assign a phase *M2 = 0, as indicated by a large positive A, value.…”

Section: Discussionmentioning

confidence: 99%

Direct determination of crystallographic phases for diffraction data from lipid bilayers. I. Reliability and phase refinement

Dorset

1991

Biophysical Journal

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Direct analysis of lipid lamellar packing based on the probabilistic estimate of sigma 1- and sigma 2-triplet phase invariants is evaluated here for a large variety of bilayer structures than examined in an original study of this problem (Dorset, D.L., 1990. Biophys. J. 58:1077-1087). Using x-ray crystal structures of five phospholipids, three glycerides and two cerebrosides, lamellar diffraction data were generated at the approximately 3 A resolution often found experimentally from oriented multilayers. For structures where no significant density occurs at the unit cell origin, the ab initio phase determination is successful for six of the ten structures. A seventh structure can be solved if a limited set of sigma 2-triples are used to determine the initial phase set based on the hierarchy of the A2 values. Bilayers, e.g., with solvent at the origin, can be analyzed if a modified criterion for accepting phase estimates for sigma 1-triples is used, as suggested by the distribution of normalized structure factors and the number of probable single-valued phase domains. In all cases, partial phase determinations can be refined effectively by density modification ("flattening") of the hydrocarbon region in real space. A figure of merit suggested by Luzzati et al. (Luzzati, V., A. Tardieu, and D. Taupin. 1972. J. Mol. Biol. 64:269-286) used to evaluate the success of such refinement can be supplemented by an evaluation of density smoothness, which can also detect the presence of near structure homomorphs not identified by the former test for density flatness.

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Section: Discussionmentioning

confidence: 99%

Direct determination of crystallographic phases for diffraction data from lipid bilayers. I. Reliability and phase refinement

Dorset

1991

Biophysical Journal

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“…Structurally, this made a considerable difference to the physical structure, and hence the interpretation, of the biochemical function, of nerve myelin. This was published by Burge and Fiddy (1981). The study of the analytic properties of fields led to a recognition that from a finite support scattering target, all information about that target was encoded in the displacement of zeros from a regular array of real zero locations.…”

Section: P1520mentioning

confidence: 97%

Imaging with Electrons, X-rays, and Microwaves

Burge

2015

Advances in Imaging and Electron Physics

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“…Subjective constraints are placed on the solution based upon what "looks to be correct." Recently, hopes for a unique solution have been revived with a method for correctly determining where the zeros of the continuous intensity transform occur (Burge and Fiddy, 1981).…”

Section: Introductionmentioning

confidence: 99%

Direct determination of crystallographic phases for diffraction data from phospholipid multilamellar arrays

Dorset

1990

Biophysical Journal

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Direct determination of crystallographic phases based on probabilistic of sigma 1 and sigma 2 "triplet" structure invariants has been found to be an effective technique for structure analysis with lamellar x-ray or electron diffraction intensity data from phospholipids. In many cases, nearly all phase values are determined, permitting a structure density (electron density for x-ray diffraction; electrostatic potential for electron diffraction) map to be calculated, which is directly interpretable in terms of known bilayer lipid structure. The major source of error is found to be due to the distortion of observed electron diffraction intensity data by incoherent multiple scattering, which can significantly affect the appearance of the electrostatic potential map, but not the success of the phase determination, as long as the observed Patterson function can be interpreted.

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Phase assignment to diffraction patterns based on the analytic properties of scattered fields applied to the structure of nerve myelin

Cited by 7 publications

References 28 publications

Direct determination of crystallographic phases for diffraction data from lipid bilayers. I. Reliability and phase refinement

Direct determination of crystallographic phases for diffraction data from lipid bilayers. I. Reliability and phase refinement

Imaging with Electrons, X-rays, and Microwaves

Direct determination of crystallographic phases for diffraction data from phospholipid multilamellar arrays

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