Researchers at the Max Planck Institute of Biochemistry and Ludwig-Maximilians-Universität München have developed a method to study spontaneous molecular interactions on biological membranes. Their method, called Mass-Sensitive Particle Tracking (MSPT), determines the movements and reactions of individual unlabeled proteins on biological membranes solely by their mass.
Cellular processes on membranes are often fast and short-lived. Molecules assemble briefly, separate again, interact with different partners and move along or through the membrane. It is therefore important to not only study static snapshots of these processes, but also to understand their dynamics.
The starting point for the team was recent advancements in mass photometry. What is new about MSPT is that the dynamics of membrane-associated proteins can now be tracked in their biologically plausible environment. In this process, individual proteins are identified by their molecular mass without the need for labeling. Frederik Steiert, one of the first authors of the paper published recently in Nature Methods, explains "We can now track directly on biological membranes what mass individual proteins have, how they move and how they interact. This allows us to study the dynamics of biological systems in greater detail." Analyzing dynamic processes is particularly important in biology as many processes at the membrane are transient.
The new method relies on videos in which individual proteins on membranes that have been made directly visible are recorded with a microscope. With the aid of analysis software, these proteins can be tracked and their scattering signal, and thus their mass, can be determined. This is currently possible for proteins with a molecular weight of at least 50 kDa.