By Xenocs
SAXS encodes structural information through the scattering intensity profile, which reflects the internal pairwise distances within the particle. Fourier transformation converts this information into the pair distance distribution function (PDDF), which represents all distances between points inside the particle. From the PDDF, SAXS provides: - Overall particle shape, distinguishing globular, rod-like, disk-like, or more complex geometries - Characteristic dimensions, such as maximum particle dimension (Dmax), radii, or aspect ratios - Internal symmetry and compactness, inferred from the PDDF profile shape - Presence of extended or flexible domains, visible through long tails or broadened distributions XSACT Pro uses modern Bayesian approaches [1], to extract the PDDF with minimal user input and no loss of structural information, ensuring a robust reconstruction. SAXS shape determination applies to a wide range of nanoscale systems, particularly those that are monodisperse or moderately polydisperse. Typical samples include: - Protein solutions, including monomeric and oligomeric species - Dilute nanoparticles in aqueous or organic media - Surfactant assemblies and micelles, including block-copolymer micelles - Lipid-based colloidal systems such as liposomes or vesicles - Polymeric or inorganic nano-objects stable in suspension Because researchers perform SAXS measurements in solution or in soft-matter environments, they preserve the native, hydrated structure of the particle. Ensemble-averaged statistical relevance: SAXS probes millions of particles within the illuminated volume, ensuring ensemble-averaged statistical relevance. Non-destructive and label-free analysis: This preserves the sample’s native state. Measurements under physiological or formulation conditions: Enabling shape determination in buffers, solvents, surfactant environments, or other realistic media. Compatibility with flexible or partially disordered systems: Where high-resolution crystallography or microscopy may be limited. Straightforward workflow: Allowing shape determination from a single scattering curve without the need for crystallization or staining. These features make SAXS a powerful method for elucidating particle and macromolecular geometry in biostructural research, nanomaterial design, drug delivery systems, soft-matter physics, and colloidal science.
