The tiniest ‘ruler’ ever recorded distances as minuscule as an atom’s width

The smallest “ruler” ever made is accurate enough to measure the width of a single atom in a protein.

Proteins and other large molecules, or macromolecules, can sometimes fold into the wrong shape, and this can affect their function. Some structural changes also play a role in conditions such as Alzheimer’s disease. To understand this process, they say it is important to determine the precise distances between atoms and between clusters of atoms within these macromolecules. stephen saar At the Max Planck Institute for Interdisciplinary Sciences in Germany.

“We wanted to take a bold step from microscopy mapping the relative positions of macromolecules to going inside them,” he says.

To construct the intramolecular “ruler,” Searle and his colleagues exploited fluorescence, the fact that some molecules glow when exposed to light. They attached two fluorescent molecules to two different points on a larger protein molecule and used a laser beam to illuminate them. Based on the light emitted by the glowing molecules, the researchers were able to measure the distances between them.

They used this method to measure the distances between molecules of several well-understood proteins. Their minimum distance is only 0.1 nanometers, or the width of a typical atom. The fluorescent ruler also provided accurate measurements up to about 12 nanometers. This means it has a wider measurement range than can be achieved with many traditional methods.

In one example, researchers looked at two different forms of the same protein and found that they could tell them apart because the same two points were 1 nanometer apart in one shape and 4 nanometers apart in the other. I discovered. In another experiment, they measured small distances in human bone cancer cells.

Searle said the research team will take advantage of several recent technological advances, including better microscopes and fluorescent molecules that don’t flicker and emit light that can be confused with other effects. This accuracy was achieved with.

“I don’t know how they made the microscope so stable. The new method is definitely a technological advance,” he says. Jonas Reese at the University of Vienna, Austria. But future research will need to determine exactly which molecules are most useful as sources of information for biologists, he says.

“Although this new method boasts great accuracy, it does not necessarily achieve the same level of detail or resolution when applied to more complex biological systems,” he says. Kirti Prakash At the Royal Marsden NHS Foundation Trust and Cancer Research Institute, UK. Additionally, several other new technologies are already becoming competitive in measuring increasingly shorter distances, he says.

Searle said his team is currently working on two things: further refining the method and expanding its ideas about which macromolecules it can peer inside.