Multi-Angle Light Scattering (MALS) measures the amount of light scattered by particles in solution relative to the angle of the incident light. For larger macromolecules and complexes (above 10 nm for 690 nm light) or for unfolded or strongly elongated proteins, the angular dependence in a multi-angle light scattering experiment can be used to calculate Rg. Rg is the “root means square radius” or “radius of gyration” and reflects the mass distribution of a macromolecule around its center of mass.

MALS in conjunction with a concentration detector can directly measure the absolute molar masses of macromolecules and complexes, independent of structure and shape from 200 daltons to hundreds of millions of daltons. SEC-MALS uses size exclusion chromatography (SEC) coupled to an in-line multi- angle light scattering detector and an in-line refractive index or UV/Vis detector. SEC-MALS can be used to determine the absolute molecular mass of proteins and complexes in complex samples, independent of their elution volume from the SEC column. In contrast to conventional SEC chromatography this method can accurately measure MW, even for sticky or elongated proteins that elute to late or too early for their actual mass to be correctly determined by size exclusion chromatography SEC alone (due to their unusual interaction with the columns).

An integrated dynamic light scattering detector allows measurement of the hydrodynamic radius (Rh)  of particles, with a lower limit of 0.5 nm.

In CG-MALS a composition-gradient preparative system is combined with MALS/RI/UV detectors to measure interactions between biological macromolecules, by directly observing changes in molar mass due to complex formation or dissociation in solution and without the need for labeling or immobilization.

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Exciting Possibilities in Biology, Biochemistry and Biophysics:

  • Absolute molar mass of macromolecules and complexes  
  • Absolute molecular stoichiometry
  • Binding affinity from pM to mM
  • Self- and hetero-association and simultaneous self- and hetero-association
  • Second virial coefficient A2
  • Molar mass and  stoichiometry of membrane protein-detergent complexes
  • Protein-conjugate analyses ( e.g. glycosylated or pegylated proteins)
  • Non-specific interactions between proteins at high concentrations
  • And a lot more ...