Mass photometry is an analytical technique that precisely measures the mass of individual molecules in solution. This method represents an advancement in molecular analysis, offering high precision in determining the mass and composition of biological molecules. It provides researchers with an understanding of molecular weight and how molecules interact, without the need for chemical labels. This approach helps to characterize a wide range of macromolecules and their complexes, providing insights.
How Mass Photometry Works
The principle behind mass photometry involves detecting light scattered by individual molecules as they briefly interact with a specialized surface. A light source, typically a laser, illuminates a glass microscope slide where the sample is introduced. As individual molecules from the solution adsorb onto this surface, they scatter the incident light.
The instrument then measures the interference between the light scattered by the molecule and the light reflected from the surface. This phenomenon, known as interferometric detection, allows for the detection of very small molecules. The resulting signal, or “contrast,” is directly proportional to the molecule’s mass, enabling accurate mass determination after calibration with known molecular standards. Data is collected as a short movie and then processed using ratiometric imaging to differentiate the faint signals from individual molecules against the background.
Insights from Mass Photometry
Mass photometry provides specific information about molecules, which is valuable for understanding their behavior. One primary insight is the accurate determination of molecular weight for single molecules, ranging from approximately 30 kilodaltons (kDa) to 6 megadaltons (MDa), encompassing proteins, nucleic acids, and even small viruses. This direct measurement differs from techniques that infer size from hydrodynamic radius, offering a true molecular mass.
The technique also assesses sample purity and heterogeneity by measuring each molecule individually. This single-molecule resolution allows for the detection of various subpopulations within a sample, revealing mixtures of different sizes or aggregation states that might be missed by bulk methods. Mass photometry can also quantify the concentration of active molecules and determine the stoichiometry of molecular complexes. This means it can ascertain how many units make up a larger complex, providing precise details on molecular assembly and interactions.
Real-World Applications of Mass Photometry
Mass photometry has diverse applications across scientific and medical fields, due to its minimal sample volumes, speed, and high resolution. In drug discovery, it is used for the characterization of proteins, helping researchers understand protein-protein interactions and the assembly of large, multimeric complexes. This includes assessing protein oligomerization and identifying complex formation.
The technology is also applied in the quality control of gene therapy vectors, such as adeno-associated viruses (AAVs), by rapidly determining capsid loading and the ratio of empty to full capsids. This provides quick insights into vector production, aiding in early fault detection and process optimization. Mass photometry is also used to analyze viral particles and virus-like particles (VLPs), offering a quick and sensitive solution for their characterization.
Mass photometry is also used to study protein-protein interactions by quantifying the relative abundance of species and determining dissociation constants. It also helps in understanding molecular assembly and the stability of sample components, providing insights into molecular assembly and stability. Its label-free nature and ability to analyze samples in their native state make it a versatile tool for biomolecular analysis, including antibody characterization and the detection of aggregates or impurities.