A Quantitative Description for Optical Mass Measurement of Single Biomolecules

Label-free detection of single biomolecules in solutionhas beenachieved using a variety of experimental approaches over the pastdecade. Yet, our understanding of the magnitude of the optical contrastand its relationship with the underlying atomic structure as wellas the achievable measurement sensitivity and precision remain poorlydefined. Here, we use a Fourier optics approach combined with an atomicstructure-based molecular polarizability model to simulate mass photometryexperiments from first principles. We find excellent agreement betweenseveral key experimentally determined parameters such as optical contrast-to-massconversion, achievable mass accuracy, and molecular shape and orientationdependence. This allows us to determine detection sensitivity andmeasurement precision mostly independent of the optical detectionapproach chosen, resulting in a general framework for light-basedsingle-molecule detection and quantification.

Automated summary

Label-free detection of single biomolecules in solution has been achieved using various experimental approaches, but our understanding of the optical contrast and its relationship with atomic structure, as well as the measurement sensitivity and precision, is still unclear. In this study, a Fourier optics approach combined with an atomic structure-based molecular polarizability model is used to simulate mass photometry experiments, resulting in excellent agreement with experimentally determined parameters. This provides a general framework for light-based single-molecule detection and quantification that is independent of the optical detection approach chosen.