Under an electron microscope, a protein looks like a series of blurry shadows — hundreds of thousands of images of the same molecule, but from different angles and with heavy noise. Previously, from these shadows, one first assembled a volumetric 'haze'—a map of how electric charge is distributed inside the protein. Only then, looking at this haze like a sculptor at a block of marble, did one carve out the atomic model.

The new approach does it differently. It takes a ready-made template of the protein chain, like a wireframe, and starts bending, twisting, and shifting it until the shadows of this frame match the actual images. No intermediate haze. The protein is compared directly with the images, as if checking a key's shape by inserting it into a lock, rather than drawing the lock from an imprint.

To make the frame bend plausibly, its movements are constrained by rules that prevent the protein from 'breaking.' It's like a jointed doll: arms and legs only turn at the joints. On synthetic data, the method recovered both single chains and complex multi-chain proteins, even catching transitions between different shapes.

In the end, the path from blurry shadows to a clear model has become one step shorter. And the shorter the path, the fewer errors accumulate along the way.