Our Best View Yet of Molecules Moving Inside Living Cells

By George Dvorsky on at

A new microscope developed by the Marine Biological Laboratory in Chicago is allowing scientists track the position and orientation of individual molecules in living cells. It has the potential to reveal unknown aspects of molecular behaviour, including those that turn cells into agents of disease.

Dubbed the “instantaneous fluorescence polarisation” microscope, this new tool is being used to understand how tiny molecules move and assemble within live human skin cells. It reveals how individual molecules—which measure just a billionth of a meter across—wiggle their way inside a live cell, bind together to form larger cellular structures, and drive a cell’s biological functions.

Left: Individual molecules in action. Right: Pink lines show the orientation of each fluorescent particle. In this video, the molecules are riding along actin filaments, which allow cells to contract. (Credit: Shalin Mehta and Tomomi Tani)

As described in a new paper in Proceedings of the National Academy of Sciences, scientists were able to determine the orientation of single molecules, and watch how an assembly of molecules came together to form a higher-order structure.

“Cells rely on a wide variety of molecular arrangements for their function,” lead author Shalin Mehta of the University of Chicago told Gizmodo. “For example, muscles contract along a specific orientation because of the alignment of molecules. This new microscope and algorithms let scientists see how individual molecules align and interact with each other in live cells, even though these assemblies are much finer than the resolution limit of the light microscope.”

Our Best View Yet of Molecules Moving Inside Living Cells
Actin filaments are colour coded to show how they’re oriented atop an image of fluorescent particle intensity. (Credit: Shalin Mehta and Tomomi Tani)

Meha and his team were able to catch a glimpse of the microscopic particles by using polarised light, a property of light that’s not visible to the human eye. After bathing DNA and actin molecules in fluorescence, the researchers tracked the movements of these tiny particles in living human skin cells.

This microscope will improve our understanding of cellular function, and potentially explain why cells sometimes go haywire, such as when they turn cancerous. [Proceedings of the National Academy of Sciences]