The Structural Characteristics Features of the Nanocomposite Systems of CdS Quantum Dots in the Gel Matrix Obtained by the Method of Small-Angle X-Ray Scattering

2014 ◽  
Vol 213 ◽  
pp. 216-221
Author(s):  
Anna N. Galkina ◽  
Alexander A. Sergeev
Keyword(s):  
Quantum Dots ◽  
Small Angle ◽  
Structural Characteristics ◽  
Data Interpretation ◽  
Cds Quantum Dots ◽  
Particle Structure ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The strucrture of CdS quantum dots 0,3% (mass), stabilized by the solution of the mercaptosuccinic acid in the gel matrix 50% THEOS is investigated by small-angle X-ray scattering (SAXS). Application of modern methods of SAXS data interpretation, including procedure of ab initio modeling of particle structure, allowed us for the to reveal structural organization of both individual nanoparticles and of their clusters incorporated in the polymer matrix. As a result, the shape, size, and size distribution of the obtained nanoparticles and their clusters depended on the structure of the gel matrix used as a formation medium.

Study of CdSe/CdS quantum dots in solutions and gels by small-angle X-ray scattering

2011 ◽  
Vol 5 (1) ◽  
pp. 126-133 ◽  
Author(s):  
N. B. Simonova ◽  
F. V. Tuzikov ◽  
R. N. Khramov ◽  
N. A. Tuzikova ◽  
M. F. Tuzikov ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Small Angle ◽  
Cds Quantum Dots ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Influence of polychromaticity on particle structure determination in small-angle X-ray scattering

2015 ◽  
Vol 48 (6) ◽  
pp. 1935-1942 ◽  
Author(s):  
Wenjia Wang ◽  
Eleonora V. Shtykova ◽  
Vladimir V. Volkov ◽  
Guangcai Chang ◽  
Lianhui Zhang ◽  
...  
Keyword(s):  
Small Angle ◽  
Structural Parameters ◽  
Shape Reconstruction ◽  
The Body ◽  
Particle Structure ◽  
Saxs Data ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Pink beams are now widely used for small-angle X-ray scattering (SAXS) data collection owing to their high intensity. However, the wavelength spread of a pink beam is a factor of 100 higher than that of a monochromatic beam, thus causing the experimental data to be smeared. To reveal the influence of polychromaticity on shape reconstruction, four geometric bodies (sphere, cube, helix and long cylinder) were used for SAXS data analysis. The results reveal that the influence of polychromaticity on the process of shape reconstruction is significantly more dependent on the geometry of the body than on its size. Scattering objects with smoothed scattering curves can tolerate a higher wavelength spread than those with tortuous curves. It is further demonstrated that the structural parameters calculated from the smeared data sets have little deviation from the ideal ones, which indicates the possibility of using a light source with a greater wavelength spread than a conventional pink beam for special time-resolved SAXS experiments. Finally, it is concluded that SAXS data collected in pink-beam mode can be used directly for structural calculations and model reconstructions without a desmearing procedure.

Grazing incidence small-angle X-ray scattering studies of the synthesis and growth of CdS quantum dots from constituent atoms in SiO2matrix

2003 ◽  
Vol 36 (3) ◽  
pp. 443-446 ◽  
Author(s):  
U.V. Desnica ◽  
P. Dubček ◽  
I.D. Desnica-Frankovic ◽  
M. Buljan ◽  
S. Bernstorff ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Small Angle ◽  
Grazing Incidence ◽  
Cds Quantum Dots ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

A Small-Angle X-ray Scattering Study of the Binding of Cyclosporin A to Cyclophilin

1995 ◽  
Vol 28 (5) ◽  
pp. 546-552 ◽  
Author(s):  
R. B. Knott ◽  
M. Capel ◽  
S. Hansen ◽  
R. E. Handschumacher
Keyword(s):  
Cyclosporin A ◽  
Small Angle ◽  
Structural Characteristics ◽  
Radius Of Gyration ◽  
Crystallographic Structure ◽  
Experimental Conditions ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The small-angle X-ray scattering (SAXS) technique was used to investigate structural characteristics of the protein cyclophilin in solution and to attempt to detect major changes induced by the binding of the immunosuppressant drug cyclosporin A. Maximum-entropy methods were used to analyse the experimental SAXS data. The measured radius of gyration, Rg , for cyclophilin is 16.3 (5) Å. This is equivalent to a compact sphere of radius 21.0 Å. There is qualitative agreement between the experimental SAXS profiles and the derived distance-distribution function, p(r), for cyclophilin, and similar profiles calculated from the crystallographic structure. The notable discrepancy is the difference of approximately 1.5 Å in the estimated radius of the equivalent sphere. On binding cyclosporin A, the main structure-related change in cyclophilin observed under these experimental conditions is an increased propensity to form oligomers. Meaningful estimates of Rg for the monomeric complex are not possible because of the presence of a significant population of aggregates. In a second series of experiments, both native cyclophilin and the cyclophilin/cyclosporin A complex readily formed aggregates under the prevailing experimental conditions.

Structural refinement by restrained molecular-dynamics algorithm with small-angle X-ray scattering constraints for a biomolecule

2004 ◽  
Vol 37 (1) ◽  
pp. 103-109 ◽  
Author(s):  
Masaki Kojima ◽  
Alexander A. Timchenko ◽  
Junichi Higo ◽  
Kazuki Ito ◽  
Hiroshi Kihara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Molecular Dynamics ◽  
Small Angle ◽  
Protein Structures ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Curve ◽  
Restrained Molecular Dynamics ◽  
Ray Scattering

A new algorithm to refine protein structures in solution from small-angle X-ray scattering (SAXS) data was developed based on restrained molecular dynamics (MD). In the method, the sum of squared differences between calculated and observed SAXS intensities was used as a constraint energy function, and the calculation was started from given atomic coordinates, such as those of the crystal. In order to reduce the contribution of the hydration effect to the deviation from the experimental (objective) curve during the dynamics, and purely as an estimate of the efficiency of the algorithm, the calculation was first performed assuming the SAXS curve corresponding to the crystal structure as the objective curve. Next, the calculation was carried out with `real' experimental data, which yielded a structure that satisfied the experimental SAXS curve well. The SAXS data for ribonuclease T1, a single-chain globular protein, were used for the calculation, along with its crystal structure. The results showed that the present algorithm was very effective in the refinement and adjustment of the initial structure so that it could satisfy the objective SAXS data.

Quality control of protein standards for molecular mass determinations by small-angle X-ray scattering

2010 ◽  
Vol 43 (2) ◽  
pp. 237-243 ◽  
Author(s):  
Shuji Akiyama
Keyword(s):  
Quality Control ◽  
Molecular Mass ◽  
Small Angle ◽  
Biological Macromolecules ◽  
Average Deviation ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Standard Quality ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is a powerful technique with which to evaluate the size and shape of biological macromolecules in solution. Forward scattering intensity normalized relative to the particle concentration,I(0)/c, is useful as a good measure of molecular mass. A general method for deducing the molecular mass from SAXS data is to determine the ratio ofI(0)/cof a target protein to that of a standard protein with known molecular mass. The accuracy of this interprotein calibration is affected considerably by the monodispersity of the prepared standard, as well as by the precision in estimating its concentration. In the present study, chromatographic fractionation followed by hydrodynamic characterization is proposed as an effective procedure by which to prepare a series of monodispersed protein standards. The estimation of molecular mass within an average deviation of 8% is demonstrated using monodispersed bovine serum albumin as a standard. The present results demonstrate the importance of protein standard quality control in order to take full advantage of interprotein calibration.

Small-Angle X-Ray Scattering for the Discerning Macromolecular Crystallographer

2014 ◽  
Vol 67 (12) ◽  
pp. 1786 ◽  
Author(s):  
Lachlan W. Casey ◽  
Alan E. Mark ◽  
Bostjan Kobe
Keyword(s):  
Structural Biology ◽  
Small Angle ◽  
Significant Risk ◽  
Macromolecular Crystallography ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The role of small-angle X-ray scattering (SAXS) in structural biology is now well established, and its usefulness in combination with macromolecular crystallography is clear. However, the highly averaged SAXS data present a significant risk of over-interpretation to the unwary practitioner, and it can be challenging to frame SAXS results in a manner that maximises the reliability of the conclusions drawn. In this review, a series of recent examples are used to illustrate both the challenges for interpretation and approaches through which these can be overcome.

Silicon photodiode detector for small-angle X-ray scattering

1990 ◽  
Vol 23 (5) ◽  
pp. 430-432 ◽  
Author(s):  
P. R. Jemian ◽  
G. G. Long
Keyword(s):  
Small Angle ◽  
Signal To Noise Ratio ◽  
Scintillation Counter ◽  
Detector Response ◽  
Silicon Photodiode ◽  
Double Crystal ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

A photodiode X-ray detector was built to measure small-angle X-ray scattering (SAXS) at a synchrotron-radiation source in conjunction with a double-crystal diffractometer SAXS camera at photon energies between 5 and 11 keV. The photodiode detector response in this energy range is linear at photon counting rates up to 1012 photons s−1 and thus it was not necessary to attenuate the monochromatic X-ray beam with calibrated foils. SAXS data taken with a scintillation counter and the photodiode detector are compared, demonstrating marked improvement in counting statistics, rate of data acquisition and signal-to-noise ratio.

scholarly journals Guinier peak analysis for visual and automated inspection of small-angle X-ray scattering data

2016 ◽  
Vol 49 (5) ◽  
pp. 1412-1419 ◽  
Author(s):  
Christopher D. Putnam
Keyword(s):  
Small Angle ◽  
Peak Position ◽  
Scattering Data ◽  
Radius Of Gyration ◽  
Automated Inspection ◽  
Elongation Ratio ◽  
Saxs Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The Guinier region in small-angle X-ray scattering (SAXS) defines the radius of gyration,Rg, and the forward scattering intensity,I(0). In Guinier peak analysis (GPA), the plot ofqI(q)versus q2transforms the Guinier region into a characteristic peak for visual and automated inspection of data. Deviations of the peak position from the theoretical position in dimensionless GPA plots can suggest parameter errors, problematic low-resolution data, some kinds of intermolecular interactions or elongated scatters. To facilitate automated analysis by GPA, the elongation ratio (ER), which is the ratio of the areas in the pair-distribution functionP(r) after and before theP(r) maximum, was characterized; symmetric samples have ER values around 1, and samples with ER values greater than 5 tend to be outliers in GPA analysis. Use of GPA+ER can be a helpful addition to SAXS data analysis pipelines.

scholarly journals Structure of Nonionic Surfactant Diglycerol Monomyristate Micelles in Cyclohexane: a SAXS Study

1970 ◽  
Vol 23 ◽  
pp. 74-81
Author(s):  
Lok Kumar Shrestha
Keyword(s):  
Nonionic Surfactant ◽  
Small Angle ◽  
Water Addition ◽  
Saxs Data ◽  
Cross Sectional ◽  
X Ray ◽  
X Ray Scattering ◽  
Added Water ◽  
Trace Water ◽  
Ray Scattering

Structure of nonionic surfactant diglycerol monomyristate (C14G2) micelles in cyclohexane has been investigated by small-angle X-ray scattering (SAXS) technique. Structural modulation of reverse micelle (RM) has been systematically studied by changing composition, temperature change and added-water. The SAXS data were evaluated by the generalized indirect Fourier transformation (GIFT) method, which gives pair-distance distribution function (PDDF). Unlike conventional poly(oxyethylene) type nonionic surfactants, C14G2 forms RM in cyclohexane without water addition at normal room temperature. A clear indication of one dimensional (1-D) micellar growth was found with increasing C14G2 concentrations. On the other hand, temperature induced cylinder-to-sphere type transition in the RM structure. The maximum dimension and the cross-sectional diameter of the RM increased upon addition of trace water indicating the formation of water pool in the reverse micellar core.Keywords: Diglycerol monomyristate, small-angle X-ray scattering, reverse micelles.DOI: 10.3126/jncs.v23i0.2099J. Nepal Chem. Soc., Vol. 23, 2008/2009Page: 74-81

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