A new technique uses glowing molecules, laser light and microscopes to measure distances as minuscule as 0.1 nanometres – the width of a typical atom
By Karmela Padavic-Callaghan
10 October 2024
This fluorescent technique can precisely measure minuscule distances
Steffen J. Sahl / Max Planck Institute for Multidisciplinary Sciences
The tiniest “ruler” ever is so precise that it can measure the width of a single atom within a protein.
Proteins and other large molecules, or macromolecules, sometimes fold into the wrong shape, and this can affect the way they function. Some structural changes even play a role in conditions like Alzheimer’s disease. To understand this process, it is important to determine the exact distance between atoms – and clusters of atoms – within these macromolecules, says Steffen Sahl at the Max Planck Institute for Multidisciplinary Sciences in Germany.
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“We wanted to go from a microscope that maps positions of macromolecules relative to each other, to taking this bold step of going within the macromolecule,” he says.
To construct their intramolecular “ruler”, Sahl and his colleagues used fluorescence, or the fact that some molecules glow when illuminated. They attached two fluorescent molecules to two different points on a larger protein molecule and then used a laser beam to illuminate them. Based on the light the glowing molecules released, the researchers could measure the distance between them.
They used this method to measure distances between the molecules of several well-understood proteins. The smallest of those distances was just 0.1 nanometres – the width of a typical atom. The fluorescent ruler also gave accurate measurements up to about 12 nanometres, meaning it had a broader measuring range than can be achieved with many traditional methods.