Researchers from the Cluster of Excellence “Physics of Life” at the Technical University of Dresden, the Leibniz Institute for Polymer Research Dresden and the Max Planck Institute of Molecular Cell Biology and Genetics have developed an innovative method to precisely quantify the molecular composition of biological condensates. These membraneless organelles, which consist of proteins and nucleic acids, play a central role in numerous cellular processes. The findings, published in Nature Chemistry, could revolutionize basic research and biomedical applications.

Biological condensates are formed by phase separation, in which proteins and RNA or DNA form “droplets”. Their exact composition has been difficult to determine until now, as conventional methods with fluorescent labels are often inaccurate and can change the properties of the molecules. In addition, existing label-free approaches could not reliably analyze complex condensates with multiple components. The new method, called ATRI (Analysis of Connecting Lines and Refractive Index), overcomes these hurdles.

ATRI combines the measurement of the refractive index using quantitative phase imaging (QPI) with the concept of the connecting line from physical chemistry. The refractive index shows how strongly light is refracted in a medium and thus allows conclusions to be drawn about the concentration in the condensate. The connecting line links the composition of the condensate and the surrounding phase with the overall system. By combining both approaches, the concentrations of several components can be precisely calculated, even in complex mixtures with many molecules.

The method made it possible for the first time to determine the concentrations of five molecules in a condensate without fluorescence labels, a significant advance over previous approaches that were limited to one or two components. This allows researchers to predict the behavior and function of condensates in more detail. ATRI also allows the investigation of how condensates react to changes in molecular composition, such as fluctuations in gene expression.

The findings have far-reaching implications. In basic research, ATRI facilitates the understanding of the physical properties of condensates. In biomedicine, the method could help to develop therapies for diseases in which condensates play a role by showing how they react to potential active ingredients. The high precision and applicability even with small sample quantities make ATRI a promising tool for future research and therapeutic approaches.

Original Paper:

A label-free method for measuring the composition of multicomponent biomolecular condensates | Nature Chemistry

Editor: X-Press Journalistenbüro GbR

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