Eric Greene smashes molecules together. He precisely arranges proteins on strands of DNA and sends one zipping toward another, headed for an impact. Sometimes, a weaker molecule falls off the DNA immediately. Other times, in a feat of acrobatics, one protein hurdles another. Recently, Greene saw a protein push another one backward when the two collided.

How proteins behave in such a crash test gives scientists data about their structural integrity, how they attach to DNA, and how they behave in a cell—where molecular fender-benders are likely a commonplace occurrence in the jam-packed nucleus.

Greene, an HHMI early career scientist at Columbia University, is doing these kinds of experiments on an entirely new scale. Rather than looking at the behavior of just one molecule at a time, he lines up hundreds of DNA strands and watches hundreds or thousands of proteins as they interact with the DNA. The aligned molecules of DNA with bright dots of fluorescent protein look like glittering, beaded curtains—leading Greene to dub them "DNA curtains." But these flashing curtains provide more than stunning images. They give researchers powerful insights into how DNA-bound proteins interact with the DNA and with each other.

Illustration: Laura Carlin