Molecular Size

Among the many parameters used to describe molecular size, the radius of gyration (Rg) is one of the most commonly used. Rg is defined as the mass-weighted average distance from the center of mass of a molecule to each of its mass elements, providing information about the molecular size and conformation in solution. In light scattering measurements, Rg indicates whether a molecule behaves as a small, compact structure or a large, extended one.

When the molecular size exceeds a certain threshold, scattering becomes angle-dependent, and low-angle light scattering is required for accurate analysis. By combining low-angle and right-angle light scattering signals, both absolute molecular weight and Rg can be determined, offering deeper insight into molecular structure beyond molecular weight alone.