Standard protocol for mass photometry experiments

Mass photometry (MP) is a relatively new experimental technique with a quickly expanding list of applications. Using optical detection, MP measures the mass of individual molecules to obtain molecular mass distributions of proteins and other biomolecules in solution. The combination of speed, sensitivity, and very low sample consumption with label- and immobilization-free detection sets MP apart from other analytical methods. An increasing number of laboratories incorporates mass photometry as a routine sample analysis technique. However, MP measurements can sometimes be challenging, especially for users without previous experience with single-molecule techniques. Here, we present a protocol for the determination of protein molecular mass distributions by MP. It describes the sample and materials preparation as well as data collection and analysis. The advantages and limitations of this technique and the potential sources of artifacts are also given. This protocol can be used by new MP users and serve as a checklist for laboratories routinely performing MP experiments to guide consistent data collection and documentation.

Automated summary

Mass photometry is a rapidly expanding experimental technique that measures the mass distribution of molecules in solution. It offers speed, sensitivity, and low sample consumption without the need for labeling or immobilization, making it stand out from other analytical methods. Increase in the number of laboratories using mass photometry for routine sample analysis highlights its advantages for consistent data collection and documentation.