<i>Neutron scattering at a pulsed source</i>edited by R. J. Newport, B. D. Rainford and R. Cywinski

Howard, J. A. K.

doi:10.1107/s0021889889002037

Cited by 11 publications

(14 citation statements)

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“…Nevertheless, the approximate error magnitude can be calculated from the e.s.d.s of the refined parameters. In the program SHADOW (Howard & Snyder, 1989), the weighted least-squares error is minimized, / Rwp:RES/~i wil2(obs. ), (ll) where RES = ~_~iwi[li(obs.)-li(cal.)]…”

Section: Methodsmentioning

confidence: 99%

“…Data were transferred to a personal computer for processing. The program SHADOW (Howard & Snyder, 1989) was partially modified and implemented on a personal computer and a program for the Warren-Averbach analysis was written in Fortran. The method of size and strain analysis, described above, was done on diffraction patterns of commercially available tungsten and silver powders with nominal grain sizes 4-12l.tm.…”

Section: Experimental Methods and Choice Of Standard Specimenmentioning

confidence: 99%

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Profile fitting of X-ray diffraction lines and Fourier analysis of broadening

Balzar¹

1992

J Appl Cryst

135

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The extraction of pure‐specimen X‐ray diffraction‐line broadening is described using a convolution of the instrumental profile and an exact Voigt function. Real Fourier coefficients were computed from the Cauchy and Gauss integral breadths and were input for Warren–Averbach analysis. Smooth surface‐weighted and volume‐weighted column‐length distribution functions were obtained and errors in root‐mean‐square strains as well as effective domain sizes were evaluated. The method was applied to two cubic structures with average volume‐weighted domain sizes up to 3600 Å as well as patterns of tetragonal and orthorhombic (La, Sr)2CuO4, which exhibit weak line broadenings and highly overlapping reflections. Comparison with the integral‐breadth methods is given. Reliability of the method is discussed in the case of a cluster of overlapping peaks.

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Section: Methodsmentioning

confidence: 99%

Section: Experimental Methods and Choice Of Standard Specimenmentioning

confidence: 99%

Profile fitting of X-ray diffraction lines and Fourier analysis of broadening

Balzar¹

1992

J Appl Cryst

135

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“…In order to merit a 'direct quantitative' appelation, in principle the g instrumental function has to be kept fixed during refinements and h must be modelled by performance of the f. g convolution either directly or in Fourier space. The convolution in WPPF has been carried out (i) numerically with (Howard & Snyder, 1989) or without (Toraya, 1989) the structure constraint, (ii) in Fourier space with the summations replaced by a product of Fourier coefficients representingfand g (Le Bail, 1985) and (iii) through the simple expressions available (de Keijser, Mittemeijer & Rozendaal, 1983) when both f and g are described by analytical profiles. A detailed chronological presentation, concerning applications of the above methods, is reported by Le Bail (1992b) and to it can be added some more recent results (Latroche, Rodriguez-Carvajal, Percheron-Gurgan & Bourre-Vigneron, 1995).…”

Section: Quantitative Approach Of Anisotropic Line Broadening In Wppfmentioning

confidence: 99%

A Qualitative Account for Anisotropic Broadening in Whole-Powder-Diffraction-Pattern Fitting by Second-Rank Tensors

Bail¹,

Jouanneaux²

1997

J Appl Cryst

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Anisotropic line broadening in cell-constrained wholepowder-pattern fitting (including the Rietveld method) is proposed to be modelled qualitatively. The object is primarily to improve the fit, with the expectation of an increase in the feasibility of an ab initio structure determination in difficult cases. In a first simple approach, distances from an origin to ellipsoid surface are considered to represent the directionally dependent widths and shapes. Improvements in the profile refinements with a decrease of up to about 50% in the R factors may be obtained in cases unaffected by faulting. Experimental cases support the method and show the application limits.

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“…The lack of neurotoxicity in preparations of the toxin labelled with N-bromosuccinimide or ethoxyformic acid, even when the phospholipase active centre was protected from the latter reagent [39], could be due to differences in the extent of modification, groups labelled or their positions. Likewise, [3H]pyridoxalation of /?-bungarotoxin, even to low specific radioactivity (8.4 Ci/mmol), lowered its peripheral toxicity 10-fold [50]; phospholipase activity of this preparation was not reported.…”

Section: Discussionmentioning

confidence: 99%

“…It is assumed, but not proven, that lysine groups are labelled, as demonstrated for propionylated a-bungarotoxin [32]. This assumption is supported by the demonstration of an essential residue, presumably a lysine amino group in the phospholipase A2 active site of p-bungarotoxin which can be modified by ethoxyformic anhydride [39]. The lethality of 3H-toxin was.…”

Section: Churucter Isu T Ion Of H-p-bunguro T Oxinmentioning

confidence: 99%

Preparation of Neurotoxic 3H-β-Bungarotoxin: Demonstration of Saturable Binding to Brain Synapses and Its Inhibition by Toxin I

Othman

Spokes

Dolly

2005

European Journal of Biochemistry

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Homogeneous β‐bungarotoxin, isolated from the venom of Bungarus multicinctus was radiolabelled with N‐Succinimidyl‐[2,3‐3H]propionate. Stable, di‐propionylated material was obtained which was tritiated on both subunits and had a specific radioactivity of 102 Ci/mmol. After separation from unlabelled toxin by isoelectric focussing, it was shown to exhibit significant biological activity in both the peripheral and central nervous systems but had negligible phospholipase A2 activity towards lecithin or cerebrocortical synaptosomes. The labeled neurotoxin binds specifically to a single class of non‐interacting sites of high affinity (Kd= 0.6 nM) on rat cerebral cortex synaptosomes; the content of sites is about 150 fmol/mg protein. This binding was inhibited by unlabelled β‐bungarotoxin with a potency which indicates that tritiation does not alter the affinity significantly. The association of toxin with its binding component and its dissociation were monophasic; rate constants observed were 7.8 × 105 M−1 s−1 and 5.6 × 10−4 s−1 at 37°C, respectively. β‐Bungarotoxin whose phospholipase activity had been inactivated with p‐bromophenacyl bromide inhibited to some extent the binding of tritiated toxin but with low efficacy. Taipoxin and phospholipase A2 from bee venom, but not Naja melanoleuca, inhibited the synaptosomal binding of toxin with low potencies in the presence, but not the absence, of Ca2+. Toxin I, a single‐chain protein from Dendroaspis polylepis known to potentiate transmitter release at chick neuromuscular junction, completely inhibited the binding of 3H‐β‐bungarotoxin with a Ki of 0.07 nM; this explains its ability to antagonise the neuroparalytic action of β‐bungarotoxin. Other pure presynaptic neurotoxins, α‐latrotoxin and botulinum neurotoxin failed to antagonise the observed binding; likewise tityustoxin, which is known to affect sodium channels, had no effect on 3H‐β‐bungarotoxin binding. Trypsinization of synaptosomes completely destroyed the binding activity, suggesting that the binding component is a protein; the functional role of the latter is discussed in relation to the specificity of toxin binding.

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Neutron scattering at a pulsed sourceedited by R. J. Newport, B. D. Rainford and R. Cywinski

Abstract: Occurrence, properties and utilization of natural zeolites. Edited by D. Kall6 and H. S. Sherry. Pp. xiii +857. Budapest:

Cited by 11 publications

References 0 publications

Profile fitting of X-ray diffraction lines and Fourier analysis of broadening

Profile fitting of X-ray diffraction lines and Fourier analysis of broadening

A Qualitative Account for Anisotropic Broadening in Whole-Powder-Diffraction-Pattern Fitting by Second-Rank Tensors

Preparation of Neurotoxic 3H-β-Bungarotoxin: Demonstration of Saturable Binding to Brain Synapses and Its Inhibition by Toxin I

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