Small-angle scattering techniques for biomolecular structure and dynamics

ANDREA MATHILDE MEBERT; MARÍA EMILIA VILLANUEVA; GABRIEL TOVAR GIMENEZ; PEREZ BRAVO, JONAS; COPELLO, GUILLERMO J

ADVANCED SPECTROSCOPIC METHODS TO STUDY BIOMOLECULAR STRUCTURE AND DYNAMICS

Elsevier

Año: 2022; p. 271 - 301

Small-angle scattering (SAS) techniques provide useful information, typicallyaround the mesoscale (1–100 nm), but they could bring the information upto 1000 nm for certain instrumental arrangements. Contrary to microscopies,a direct image is not obtained in SAS techniques. The scattered light, X-ray, orneutron radiation is analyzed to deduce the structure. Light scattering fromhomogeneous media (gas, solid, or liquid) is because of electron density fluctuations. The contrast in X-ray scattering results from the differences in theelectron densities and, for neutron beams, arises from the differences in thenature ofthe atomic nucleus.The X-rays and neutrons can sample similar structural dimensions because oftheir comparable wavelengths. From another pointof view, although electrons surrounding the atomic nuclei are thetarget of lightand X-ray interaction,the neutrons are scattered bythe nucleusitself.Althoughexperiments and data treatment of SAStechniques are different,the fundamental theories and models are quite similar. The main difference is the mechanismby which the incident radiation interacts with the matter. In all approaches, acollimated radiation interacts with a sample, and the scattered pattern is analyzed. A perpendicular monochromatic beam interacts with the sample, andthe scattered radiation is recorded on a detector, as represented in Fig. 1.Time-averaged intensity is measured as a function of the scattering angle andthen, for isotropic systems, radially averaged to produce a chart of intensity versus the scattering vector (q)