Determination of the molecular weight of proteins in solution from a single small-angle X-ray scattering measurement on a relative scale

2009 ◽  
Vol 43 (1) ◽  
pp. 101-109 ◽  
Author(s):  
H. Fischer ◽  
M. de Oliveira Neto ◽  
H. B. Napolitano ◽  
I. Polikarpov ◽  
A. F. Craievich
Keyword(s):  
Molecular Weight ◽  
Small Angle ◽  
Dilute Solution ◽  
X Ray ◽  
Molecular Weights ◽  
X Ray Scattering ◽  
Saxs Curve ◽  
Relative Scale ◽  
Ray Scattering

This paper describes a new and simple method to determine the molecular weight of proteins in dilute solution, with an error smaller than ∼10%, by using the experimental data of a single small-angle X-ray scattering (SAXS) curve measured on a relative scale. This procedure does not require the measurement of SAXS intensity on an absolute scale and does not involve a comparison with another SAXS curve determined from a known standard protein. The proposed procedure can be applied to monodisperse systems of proteins in dilute solution, either in monomeric or multimeric state, and it has been successfully tested on SAXS data experimentally determined for proteins with known molecular weights. It is shown here that the molecular weights determined by this procedure deviate from the known values by less than 10% in each case and the average error for the test set of 21 proteins was 5.3%. Importantly, this method allows for an unambiguous determination of the multimeric state of proteins with known molecular weights.

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.

scholarly journals Size and Concentration Determination of Colloidal Nanocrystals by Small-Angle X-Ray Scattering

2018 ◽  
Author(s):  
Jorick Maes ◽  
Nicolo Castro ◽  
Kim De Nolf ◽  
Willem Walravens ◽  
Benjamin Abécassis ◽  
...  
Keyword(s):  
Band Gap ◽  
Small Angle ◽  
Accurate Determination ◽  
Band Gap Energy ◽  
Colloidal Nanocrystals ◽  
X Ray ◽  
Absolute Scale ◽  
X Ray Scattering ◽  
Ray Scattering

<div> <div> <div> <p>The accurate determination of the dimensions of a nano-object is paramount to the de- velopment of nanoscience and technology. Here, we provide procedures for sizing quasi- spherical colloidal nanocrystals (NCs) by means of small-angle x-ray scattering (SAXS). Using PbS NCs as a model system, the protocols outline the extraction of the net NC SAXS pattern by background correction and address the calibration of scattered x-ray intensity to an absolute scale. Different data analysis methods are compared, and we show that they yield nearly identical estimates of the NC diameter in the case of a NC ensemble with a monodisperse and monomodal size distribution. Extending the analysis to PbSe, CdSe </p> </div> </div> <div> <div> <p>and CdS NCs, we provide SAXS calibrated sizing curves, which relate the NC diameter and the NC band-gap energy as determined using absorbance spectroscopy. In compari- son with sizing curves calibrated by means of transmission electron microscopy (TEM), we systematically find that SAXS calibration assigns a larger diameter than TEM calibration to NCs with a given band gap. We attribute this difference to the difficulty of accurately sizing small objects in TEM images. To close, we demonstrate that NC concentrations can be directly extracted from SAXS patterns normalized to an absolute scale, and we show that SAXS-based concentrations agree with concentration estimates based on absorption spectroscopy.</p></div></div></div>

Analysis of Nanopowders by Small-Angle X-Ray Scattering Method’s

2012 ◽  
Vol 7 (4) ◽  
pp. 107-116
Author(s):  
Sergey Bardakhanov ◽  
Ludmila Vikulina ◽  
Vladimir Lysenko ◽  
Andrey Nomoev ◽  
Sergey Poluyanov ◽  
...  
Keyword(s):  
Distribution Function ◽  
Size Distribution ◽  
Small Angle ◽  
Electron Accelerator ◽  
Size Distribution Function ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The possibility of application of small-angle X-ray scattering (SAXS) for nanopowders analysis was studied. The research for eight silica powders (including four powders obtained by the authors with help of electron accelerator) was conducted. The possibility of application of small angle X-ray scattering for determination of size distribution function of nanoparticles was shown

Combined Small-Angle Neutron and X-Ray Scattering Studies of Polymers

1992 ◽  
Vol 36 ◽  
pp. 355-372
Author(s):  
George D. Wignall
Keyword(s):  
Crystal Structures ◽  
Small Angle ◽  
Polymer Science ◽  
X Ray ◽  
X Ray Scattering ◽  
Made In ◽  
Ray Scattering

Scattering technigues have been employed since the beginnings of polymer science to provide information on the spatial arrangements of macromolecules. The first measurements were made in the 1920s and were concerned primarily with the determination of crystal structures via the Bragg lawnλ = 2dsinθ.

Determination of a molecular shape for netrin-4 from hydrodynamic and small angle X-ray scattering measurements

2012 ◽  
Vol 31 (2) ◽  
pp. 135-140 ◽  
Author(s):  
Trushar R. Patel ◽  
Raphael Reuten ◽  
Shawn Xiong ◽  
Markus Meier ◽  
Donald J. Winzor ◽  
...  
Keyword(s):  
Small Angle ◽  
Molecular Shape ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Measurements ◽  
Ray Scattering
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