MIT researchers have developed a novel technique to measure the strength of the bonds between two protein molecules important in cell machinery: Gently tugging them apart with light beams. “It’s really giving us a molecular-level picture of what’s going on,” said Matthew Lang, an assistant professor of biological and mechanical engineering
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The researchers studied the interactions between the proteins by pinning one actin filament to a surface and controlling the motion of the second one with a beam of light. As the researchers tug on a bead attached to the second filament, the bond mediated by the actin-binding protein eventually breaks.

With this technique, the researchers can get a precise measurement of the force holding the proteins together, which is on the order of piconewtons (10^-12 newtons).