Probing the Dynamics of Optically Induced Protein Droplets with Single-Walled Carbon Nanotubes

Eukaryotic cells exhibit high levels of internal spatial organization, including a wide variety of membrane-less compartments. Protein-protein and protein-RNA interactions have been implicated as the primary factors responsible for these membrane-less structures, but how they are maintained and utilized by the cell is still poorly understood. Many proteins essential to the formation of these structures feature long intrinsically disordered regions (IDRs) that interact with each other and can induce demixing, as seen in many recent in vitro studies. However, quantitative characterization of these structures in vivo remains challenging due to the complexity of intracellular environments. Here, we use single-walled carbon nanotubes (SWNTs), which fluoresce in the near infrared and are photostable, to probe the local environment of optically induced protein droplets in vivo. The dynamics of SWNTs can reveal internal organization within these droplets and the influence of the intracellular environment on their mechanical properties.