Calypso CG-MALS system succeeds in ABRF-MIRG study

Wyatt Technology is pleased to report the success of the Calypso composition-gradient multi-angle light scattering (CG-MALS) system in a study conducted by the Molecular Interactions Research Group (MIRG) of the Association of Biomolecular Research Facilities (ABRF). The conclusions of the 2012 MIRG study were announced at the ABRF 2013 annual meeting in early March.

In the study, a pair of unknown proteins, prepared and characterised by the ABRF, was sent out to multiple labs to determine binding affinity and stoichiometry. In a single afternoon consisting of two CG-MALS runs, the Wyatt Calypso system correctly determined that Protein Y (26.3 kDa) contains two binding sites for Protein X (11.9 kDa).

The first X binds with KD of 10 nM and the second X binds with 14 μM. This analysis agreed perfectly with extensive analytical ultracentrifugation (AUC) and isothermal titration calorimetry (ITC) measurements performed by ABRF prior to distributing the samples.

CG-MALS was the only solution-based technique utilised among the participating labs. Other participants used surface plasmon resonance (SPR) instruments which require immobilisation of one of the binding partners. Interestingly, the affinities determined by SPR were significantly weaker than those found by any of the solution-based measurements (AUC, ITC, CG-MALS), possibly indicating that immobilisation modifies this interaction.