SAS from inhomogeneous particles with more than one domain of scattering density and arbitrary shape

Abstract

The Small Angle Scattering from inhomogeneous particles is very important in the investigation of biological systems, where the scattering objects might be formed by many domains. For these systems, the scattering intensity, as well as its Fourier transform, are written as a sum of different contributions. In this work, for the simple case of two domains, the form factors of different scattering particle shapes, such as the oblate, prolate and biaxial ellipsoids, spherocylinder and disks were calculated by using a Monte Carlo method. Finally, SAS data of sodium lauryl sulfate micelles in water were analysed by using a model that accounts for polydispersity and micelles of different shape.

The Role of Decorated SDS Micelles in Sub-CMC Protein Denaturation and Association

“…The approach is inspired by the work of Hansen 42 and Spinozzi et al 43 The method is similar to the traditional modeling of SAXS data in which a structure is assumed and parameters describing the structure are optimized by weighted least-squares methods when fitting the scattering intensity of the model to the experimental data. 41 The main difference of the new method introduced here is that Monte Carlo simulation techniques are used for integrating over the volume of the objects in connection with the calculation of scattering intensity.…”

“…41 The main difference of the new method introduced here is that Monte Carlo simulation techniques are used for integrating over the volume of the objects in connection with the calculation of scattering intensity. 42,43 This is accomplished by using a finite set of points generated by Monte Carlo methods for representing the structure. The Monte Carlo method has the great advantage that one can apply very complex structural models since one is not limited to structures for which the intensity can be calculated analytically.…”

“…The main difference between the traditional modeling approach and the new one introduced here is that Monte Carlo simulation techniques are used for integrating over the volume of the objects in connection with the calculation of the scattering intensity. 42,43 A finite set of points generated by Monte Carlo methods is used for representing the structure. Note that it is straightforward to introduce smeared distributions or interfaces in the model by adding random vectors with a certain distribution to the points.…”

Structure of Immune Stimulating Complex Matrices and Immune Stimulating Complexes in Suspension Determined by Small-Angle X-Ray Scattering

“…Because it is not easy to calculate the scattering of such spherical structures on an analytical form (21,22), we developed and implemented what to our knowledge is a new modeling method. The approach was inspired by the work of Hansen (23) and Spinozzi et al (24). In their methods, Monte Carlo simulations are used to generate uniformly distributed points in space, and a subset of these points are used to represent the geometric structure of particles.…”

SANS/SAXS study of the BSA solvation properties in aqueous urea solutions via a global fit approach

“…Therefore, such urea effects merit to be further investigated, considering a different protein, but also using a broader experimental approach. In particular, the combination of SANS and SAXS techniques is a very suitable tool for this purpose: contrast variation SANS data offer the possibility to easily derive direct information about the solvation layer, while the higher quality of SAXS curves, especially in the low Q range, allows a better investigation of the structure factor, hence of the protein-protein interactions (Svergun et al 1998;Spinozzi et al 2000). In this paper, we then investigate by SAXS and SANS experiments a model protein, the bovine serum albumin (BSA) at concentration up to 125 g L -1 , in the presence of a molar content of urea well below those causing protein unfolding.…”