DATE2025.08.20 #Press Releases

Visualization of Intracellular Biomolecular Thermophoresis

— A Novel Measurement Method Reveals the Link Between Intracellular Fluidity and Biological Phenomena —

Summary

A research group led by Project Assistant Professor Keiichiro Toda and Associate Professor Takuro Ideguchi at the Institute for Photon Science and Technology, The University of Tokyo, has achieved the world’s first visualization of biomolecular thermophoresis within living cells. This was accomplished using vibrational photothermal microscopy, which generates temperature gradients inside cells and detects the resulting molecular transport through refractive index changes.

Using this technique, the team quantitatively measured the diffusion and Soretcoefficients in both the nucleus and cytoplasm. Notably, they observed that in the cytoplasm, molecules moved in the opposite direction to those in the nucleus—specifically, from cooler to warmer regions.

The researchers further discovered that thermophoresis was progressively suppressed as cells approached death, suggesting a link between alterations in the intracellular environment and molecular mobility.

These findings provide new insights into the dynamics of intracellular molecules and their connection to biological processes, while also paving the way for broader applications of vibrational microscopy.

Figure: Conceptual illustration of intracellular biomolecular thermophoresis visualized using vibrational photothermal microscopy.

Journals

Journal name	Proceedings of the National Academy of Sciences of the United States of America
Title of paper	Ludwig-Soret microscopy with vibrational photothermal effect.