By Julia Karow
The arm moves up, then slows down just a little. “It took them a while to figure out how to be able to do that,” says Robert Sweet, of the machine moving on his computer screen. He and his fellow x-ray crystallographers at the National Synchrotron Light Source at Brookhaven National Laboratory are eagerly awaiting the arrival of their first crystal-mounting robot. “We expect to have it running in March,” says Sweet, a senior scientist at the department of biology at Brookhaven who operates several beamlines.
With more and more beamlines becoming available, getting access to synchrotron radiation has become increasingly easy for protein crystallographers. But one remaining bottleneck is the simple process of placing the cryogenically frozen protein crystals into the path of the x-ray beam. At present, it takes an operator several minutes to leave the hutch that shields him or her from the x-rays, take a few exposures, go back in, take the crystal down, reach into the liquid nitrogen container, take out a new crystal, put that one on — and then repeat the whole process.
The robot will speed up crystal screening considerably. “To do more than about six an hour by hand is very hard,” says Sweet, but “to do a dozen an hour or 20 an hour using the robot is in sight.” Eventually this will free up beamtime, allowing more users to take turns.
Brookhaven’s robot will be an almost identical twin of one that lives in the hutch of structural genomics company Syrrx’s beamline at the Advanced Light Source in Berkeley, Calif., developed in Thomas Earnest’s group at the Lawrence Berkeley National Laboratory. Its pneumatically driven arm reaches down into a nitrogen-cooled Dewar filled with disks the size of hockey pucks, each of which holds up to 64 protein crystals on pins. The Dewar is movable, allowing each pin to be placed directly under the robot’s collar. It clamps the pin, picks it up, rotates 90 degrees, mounts the crystal and aligns it — all in just a few seconds.
And unlike a human being, the robot needs no gloves. “It doesn’t get its hands burnt, so there are no safety considerations at all,” says Sweet. But like a human operator, it regulates its own temperature: if it threatens to frost up, a little “hair dryer” will blow hot air on its front end. Conversely, when ready to cool down, it dips its snout into liquid nitrogen and takes a refreshing sip.
Sweet estimates the instrument will cost about $100,000 to build, paid for by the National Center for Research Resources, but, he says, “I think if we practice we can do it for less.” He and his colleagues will construct the robot according to plans provided under an agreement with the Berkeley Lab.
There is still room for improvement, however — a cooling snap could be made a bit smaller and the angle between robot and beamline could benefit from some adjusting. For the most part, though, Sweet is pleased with the machine: “It’s very highly engineered, they really have done a marvelous job.” And if this one proves a success, they will build more. The main problem, Sweet thinks, will be getting scientists to use the pucks and the right type of pins to freeze their crystals prior to sending them to the synchrotron.
Of course, even a clone needs a name. Syrrx, which hosts the original robot in its beamline, has been quite inventive in naming its robots, which answer to Sonic Hedgehog, Agincourt, and Robohutch. For now, Sweet is undecided. “I’m sure we’ll name it something,” he says via e-mail. “I suspect four-letter words will suffice for the first few months.”