Small-angle X-ray and neutron scattering

SAXSMoW 3.0: New advances in the determination of the molecular weight of proteins in dilute solutions from SAXS intensity data on a relative scale

“…Small-angle X-ray scattering (SAXS) technique is being widely used to retrieve low-resolution structural information on biomacromolecules in solution. [1][2][3][4] After the pioneering works by A. Guinier, 5 the SAXS technique found its applications in investigations of polymers, liquid crystals, proteins in solution, and other materials. 6 Modern synchrotron-based X-ray sources, powerful computers, and specialized software along with new area detectors significantly improved the quality of the results derived from SAXS experiments.…”

“…6 Modern synchrotron-based X-ray sources, powerful computers, and specialized software along with new area detectors significantly improved the quality of the results derived from SAXS experiments. 1,2,7 Isotropic systems composed of a diluted set of randomly oriented identical nanoparticles immersed in liquids (e.g., proteins diluted in buffers) are particularly favorable for SAXS data analysis. 8 As a matter of fact, in this case the associated SAXS curves are free from frequently complex effects due to anisotropy, size polydispersity, and spatial correlation.…”

“…7,[9][10][11] Using classical setups, SAXS technique allows for the determination of low-resolution structural parameters of biological systems, such as macromolecules in solution, with sizes ranging from 1 nm up to 50 nm. 1,7 The relevant parameters usually determined for macromolecules from SAXS data are the radius of gyration, R g , threedimensional low-resolution envelope, molecular weight, M r , and oligomeric state. [1][2][3][4] Knowledge of the molecular weight is particularly helpful for determination of the oligomeric state of proteins in solution.…”

“…1,7 The relevant parameters usually determined for macromolecules from SAXS data are the radius of gyration, R g , threedimensional low-resolution envelope, molecular weight, M r , and oligomeric state. [1][2][3][4] Knowledge of the molecular weight is particularly helpful for determination of the oligomeric state of proteins in solution.…”

A database of calculated solution parameters for the recently released AlphaFold predicted protein structures

“…These measurements, requiring little material and with a reasonably quick turnaround, are usually accessible in most research endeavors, especially in core facilities where analytical ultracentrifugation 7,8 , multi-angle static and dynamic light scattering (MALS and DLS) coupled to size-exclusion chromatography (SEC) 9,10 or directly on plate readers 11 , and SEC-coupled differential viscosimetry 12,13 , can often be found. On another level, small-angle X-ray scattering (SAXS) measurements can provide the rms radius of gyration R g and the pair-wise distance distribution function p(r) vs. r 14,15,16 . Notably, several synchrotron beamlines offer on-line SEC-SAXS (e.g., Table 11.1 in 17 ), some accepting mailed-in samples for this set-up (e.g., https://www.diamond.ac.uk/Users/Support-for-European-Access-to-Life-Sciences/Applications/Bio-SAXS.html; https://www.embl-hamburg.de/biosaxs/mailin.html).…”