Scattering/Diffraction

Methods based on scattering and diffraction utilize the radiation that changes direction when interacting with the object. This typically provides information on length scales smaller than what can be directly imaged. In small angle X-ray scattering, samples are analyzed to obtain information about sizes, shapes and orientations of internal structures. The analyzed features are mostly in the size range 1-200 nm. For structures down to the atomic scale, X-ray diffraction is a very powerful technique to analyze crystalline samples. For example, the atomic structures of entire proteins can be resolved.

Excillum-scattering-diffraction-image

Small Angle X-ray Scattering (SAXS)

Small Angle X-ray Scattering is used to study the structure of materials in the 1 nm to ~200 nm range. The materials typically studied include polymers, metals, colloids, liquid crystals and biological samples e.g. proteins. The information determined relates to the particle size, shape, distribution and orientation, porosity, surface features and internal structure.

A SAXS sample requires very little preparation and results are representative of the bulk material. The scattered signal is typically recorded at diffraction angles of <6° and the sample is positioned at a long distance from the detector. The measured scattered signals are accordingly extremely weak. For this reason, SAXS measurements benefit from the use of a high brilliance X-ray source such as the MetalJet, which makes weak scattering effects, stronger, more visible and more readily studied.

Examples

In-Lab SEC-SAXS for Structual Investigation of Protein Samples

  • SAXS can be used to investigate biological macromolecules especially in monodisperse solutions.

    Xenocs BioXolver equipped with MetalJet

  • However liquid bio-solutions involve structurally different molecules and complexes in dynamic equilibria.
  • SEC – Size Exclusion Chromatography has evolved as a technique to mitigate this by separating the molecules in time.
  • However this limits the measurements time window which put huge
    requirements on the X-ray source.
  • With MetalJet source in the Xenocs BioXolver system it is possible to
    perform protein in-lab SEC-SAXS even for very diluted solutions containing
    less than 1 mg of sample.

   

Application note kindly provided by Application Scientist at Xenocs SAS using a BioXolver equipped with Metaljet X-ray source.
You find the Appl. note in full here.
Bucciarelli, S. et al. Size-exclusion chromatography small-angle X-ray scattering (SEC-SAXS) of water soluble proteins on a laboratory instrument, J. Appl. Crystallogr. 2018

Fibres

Application scientists at Bruker AXS have used a NANOSTAR instrument equipped with a MetalJet (200W at 70kV) to record a series of SAXS scattering plots of a very thin fibre from a rat tail tendon. Providing intensity gains of more than 50x compared to state-of-the-art sealed microfocus tubes.

 

 

Biological (BioSAXS)

Researchers at Nanyang Technical University, A*STAR, University of Louisville, Rosalind Franklin University of Medicine and Science and Kyung Hee University have used a MetalJet equipped SAXS instrument to study the BclxL protein, a key regulator in mitochondrial calcium ion transport. The protein was treated with a mild detergent and studied during the formation of a dimer resulting from three-dimensional domain swapping (3DDS) of helices α6-α8 between two monomers.

Sci. Rep. 5, 10609 (2015), S. Rajan, M. Choi, Q. T. Nguyen, H. Ye, W. Liu, H. T. Toh, C. B. Kang, N. Kamariah, C. Li, H. Huang, C. White, K. Baek, G. Grüber, H. S. Yoon.

 

Metals and colloids

Researchers at the Slovak Academy of Science and STU Centre for Nano-diagnostics performed in-situ tests on a strain gauge, based on a monolayer of colloidal gold nanoparticles deposited on a flexible Mylar foil. The tests were monitored by SAXS where the high brightness of the MetalJet allowed a very fast data collection, with 10 seconds temporal resolution.

Sensors and Actuators A: Physical, 2016, 247, 87-95, K. Vegso, M. Jergel, P. Siffalovic, M. Kotlar, Y. Halahovetsa, M. Hodasa, M. Pellettaa, E. Majkovaa

 

Polymers

The investigation of polymers is one of the main areas of focus of the Soft Matter Analytical Laboratory (SMALL) at the University of Sheffield. Following a £2 million infrastructure investment in 2016 and the purchase of a new SAXS system with a gallium MetalJet X-ray source, their first new resulting publication was a co-polymerisation study of Styrene with N-Phenylmaleimide.

Macromolecules, 2016, 49 (18), 6731–6742, P. Yang, O. O. Mykhaylyk, E. R. Jones, S. P. Armes.

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