A key feature in many biological systems is the self-assembly of proteins into specific quaternary structures, which often determine and regulate their function. Assessment of protein oligomerisation is vital for a detailed understanding of complex biological processes. In this context, molecular mass is an important parameter, as it serves as a direct measure of oligomerisation.
Mass photometry provides high resolution distributions of molecular mass with single molecule sensitivity. This makes our technology useful for detecting rare species that form less than 1% of the main sample population.
Many proteins adopt a particular oligomeric form under certain conditions. Figure 1 illustrates how mass photometry was used to characterise four different proteins: protein A, beta-amylase, urease and thyroglobulin. These standard protein samples showcase a whole range of behaviours – from purely monomer or dimer, to a dynamic equilibrium between a different number of states.
2G12 IgG is a monoclonal antibody against the HIV envelope glycoprotein gp120. In Figure 2, mass photometry reveals the distribution of 2G12 monomer and dimer with baseline separation.
Dissecting FOXP2 oligomerization and DNA binding
Häußermann et al., Angewandte Chemie 2019, 8(23), 7662-7667
FOXP2 (Forkhead box protein P2) is a transcription factor. It contains several functional domains commonly involved in both nucleic acid-binding and protein oligomerization, whose roles in the activity of FOXP2 remain largely unknown. In this publication, mass photometry was used to quantify the interaction of FOXP2 with itself. By measuring mass distributions of the different variants of FOXP2, the authors were able to reveal the interplay between its domains.