Three-dimensional Pt-nanoparticle networks studied by anomalous small-angle X-ray scattering and X-ray absorption spectroscopy

Anomalous small-angle X-ray scattering (ASAXS) experiments with synchrotron radiation were performed to study the three-dimensional nanostructures of metal/organic hybrids formed by crosslinking aluminium-organic-stabilized platinum nanoparticles with various bifunctional organic spacer molecules. The advantage of ASAXS is the possibility of separating the particle scattering from that of the organic components, thus providing unbiased information about particle size distributions and interparticle correlation. In order to obtain the structural information from the scattering data, a model function based on Vrij's analytical solution for a multicomponent system of hard spheres is proposed. The model is applied to three different samples and the results are compared with those obtained from the application of Fourier methods (characteristic function) and X-ray absorption measurements.

Download Full-text

Two practical Java software tools for small-angle X-ray scattering analysis of biomolecules

Journal of Applied Crystallography ◽

10.1107/s1600576714004737 ◽

2014 ◽

Vol 47 (2) ◽

pp. 810-815 ◽

Cited By ~ 1

Author(s):

Andreas Hofmann ◽

Andrew E. Whitten

Keyword(s):

Small Angle ◽

Three Dimensional ◽

Small Angle Scattering ◽

Ease Of Use ◽

Scattering Data ◽

X Ray ◽

X Ray Scattering ◽

Angle Scattering ◽

Three Dimensional Models ◽

Ray Scattering

Small-angle X-ray scattering has established itself as a common technique in structural biology research. Here, two novel Java applications to aid modelling of three-dimensional macromolecular structures based on small-angle scattering data are described.MolScatis an application that computes small-angle scattering intensities from user-provided three-dimensional models. The program can fit the theoretical scattering intensities to experimental X-ray scattering data.SAFIRis a program for interactive rigid-body modelling into low-resolution shapes restored from small-angle scattering data. The program has been designed with an emphasis on ease of use and intuitive handling. An embedded version ofMolScatis used to enable quick evaluation of the fit between the model and experimental scattering data.SAFIRalso provides options to refine macromolecular complexes with optional user-specified restraints against scattering data by means of a Monte Carlo approach.

Download Full-text

Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species

Journal of The Royal Society Interface ◽

10.1098/rsif.2012.0191 ◽

2012 ◽

Vol 9 (75) ◽

pp. 2563-2580 ◽

Cited By ~ 81

Author(s):

Vinodkumar Saranathan ◽

Jason D. Forster ◽

Heeso Noh ◽

Seng-Fatt Liew ◽

Simon G. J. Mochrie ◽

...

Keyword(s):

Phase Separation ◽

Small Angle ◽

Three Dimensional ◽

Structural Data ◽

Optical Function ◽

Scattering Data ◽

X Ray ◽

X Ray Scattering ◽

Medullary Cells ◽

Ray Scattering

Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours . SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology.

Download Full-text

Reconstructing three-dimensional shape envelopes from time-resolved small-angle X-ray scattering data

Journal of Applied Crystallography ◽

10.1107/s0021889808028264 ◽

2008 ◽

Vol 41 (6) ◽

pp. 1046-1052 ◽

Cited By ~ 19

Author(s):

Jessica Lamb ◽

Lisa Kwok ◽

Xiangyun Qiu ◽

Kurt Andresen ◽

Hye Yoon Park ◽

...

Keyword(s):

Conformational Changes ◽

Small Angle ◽

Three Dimensional ◽

Model Systems ◽

Scattering Data ◽

Time Resolved ◽

X Ray ◽

X Ray Scattering ◽

Group I ◽

Ray Scattering

Modern computing power has made it possible to reconstruct low-resolution, three-dimensional shapes from solution small-angle X-ray scattering (SAXS) data on biomolecules withouta prioriknowledge of the structure. In conjunction with rapid mixing techniques, SAXS has been applied to time resolve conformational changes accompanying important biological processes, such as biomolecular folding. In response to the widespread interest in SAXS reconstructions, their value in conjunction with such time-resolved data has been examined. The group I intron fromTetrahymena thermophilaand its P4–P6 subdomain are ideal model systems for investigation owing to extensive previous studies, including crystal structures. The goal of this paper is to assay the quality of reconstructions from time-resolved data given the sacrifice in signal-to-noise required to obtain sharp time resolution.

Download Full-text

Treatment of grazing-incidence small-angle X-ray scattering data taken above the critical angle

Journal of Applied Crystallography ◽

10.1107/s0021889801001157 ◽

2001 ◽

Vol 34 (2) ◽

pp. 152-156 ◽

Cited By ~ 2

Author(s):

A. Martorana ◽

A Longo ◽

F. d'Acapito ◽

C. Maurizio ◽

E. Cattaruzza ◽

...

Keyword(s):

Small Angle ◽

Critical Angle ◽

Hard Spheres ◽

Grazing Incidence ◽

Sample Surface ◽

Scattering Data ◽

X Ray ◽

X Ray Scattering ◽

Incoming Beam ◽

Ray Scattering

The equations taking into account refraction at the sample surface in grazing-incidence small-angle X-ray scattering (GISAXS) when the angle between the incoming beam and the sample surface is slightly larger than the critical angle are derived and discussed. It is demonstrated that the refraction of both the incoming and the scattered beam at the sample surface affects the GISAXS pattern and that, when a planar bidimensional detector perpendicular to the incoming beam is used, the effect depends on the azimuthal detector angle. The smearing of the pattern depending on the size of the illuminated sample area in grazing incidence is estimated by simulations with Cauchy functions of different widths. The possibility of integrating the recorded intensities over a suitable azimuthal angular range and then of making the correction for refraction is also analysed, employing simulations involving the intensity function of monodisperse interacting hard spheres. As a case study, the refraction correction is applied to the investigation of a Cu–Ni implant on silica glass.

Download Full-text

X-ray imaging with ultra-small-angle X-ray scattering as a contrast mechanism

Journal of Applied Crystallography ◽

10.1107/s0021889804016073 ◽

2004 ◽

Vol 37 (5) ◽

pp. 757-765 ◽

Cited By ~ 28

Author(s):

L. E. Levine ◽

G. G. Long

Keyword(s):

Small Angle ◽

Imaging Technique ◽

Three Dimensional ◽

Sample Volume ◽

Contrast Imaging ◽

X Ray ◽

X Ray Scattering ◽

X Ray Imaging ◽

Contrast Mechanism ◽

Ray Scattering

A new transmission X-ray imaging technique using ultra-small-angle X-ray scattering (USAXS) as a contrast mechanism is described. USAXS imaging can sometimes provide contrast in cases where radiography and phase-contrast imaging are unsuccessful. Images produced at different scattering vectors highlight different microstructural features within the same sample volume. When used in conjunction with USAXS scans, USAXS imaging provides substantial quantitative and qualitative three-dimensional information on the sizes, shapes and spatial arrangements of the scattering objects. The imaging technique is demonstrated on metal and biological samples.

Download Full-text