Sound, light sources and the thrill of glimpsing the future

Scientific research is a process fraught with fits and starts, dead-ends, dashed dreams, unexpected turns, and the occasional exhilarating insight. As scientists, many of us continue along our career path in part because of those rare moments of joy felt when contributing to the frontiers of science. We experienced one of those rare moments this past January at the National Synchrotron Light Source (NSLS) X25 beamline, when we successfully tested a new method to collect data from protein crystals—by using sound waves to eject the crystals through the air into an X-ray beam.

For decades now, preparing microscopic protein crystals to collect data was done typically by hand with a microscope, and lassoing a crystal out of its liquid environment required great skill. After that was done, the sample would be transported from the lab to a beamline end station and then mechanically transferred into the X-ray beam, where we collected data to determine the atomic structure of complex macromolecules.

In contrast, this new method—called acoustic droplet ejection (ADE)—employs pulsed sound waves to eject crystals encased in a droplet from their source into the X-ray beam. This can be done with great precision, at high speeds, and without touching the crystals at all. We theorized that this was in fact possible back in 2008, but we were overcome with joy when, last month, we observed the first X-ray diffraction pattern from crystals with our new, automated ADE method.