Proposal to Establish an NSF Science Technology Center
by Eaton E. (Ed) Lattman
Fall 2011

At the meeting of the HWI Governing Board in May, a member asked our visiting Scientific Advisory Board members how they thought HWI was doing in staying on the cutting edge of our field, and in planning for a rapidly evolving environment. It turns out that we are doing quite a lot, and our efforts make an interesting story. Let me elaborate one example.

HWI, in its role as the UB Department of Structural Biology, is the lead institution in a proposal to the National Science Foundation to establish an NSF Science Technology Center. The budget for this grant is $25 million over five years, and we have a large number of highly visible and productive co-investigators. These awards are very competitive, and no group has a particularly good chance to receive one. Nevertheless, to be invited to lead the charge is exciting and flattering to our scientists. And it represents only one of a number of efforts on the part of HWI to be at the forefront of new technology.

The proposal for the Center is to further the development of an exciting new device called an X-ray Free Electron Laser (XFEL). This device produces x-ray beams comprised of incredibly short pulses, each one being incredibly intense - rather like the world’s brightest flash bulb. It has the capacity to remake our field in several ways. To understand this, a bit of technology history is helpful.

Progress in HWI’s specialty of x-ray crystallography is strongly dependent on continually improving technology. Our experiment is conceptually simple. We shine a beam of x-rays at a crystal and record the pattern of x-rays that bounce off the crystal in all directions. But such a one-sentence description glosses over a multitude of complexities. Take the x-ray beam, for example. We want a narrow beam, so that it hits the crystal but not much else. It also has to be very parallel: otherwise the pattern of beams that bounce off the crystal gets smeared out and confuses us. An intense beam is good too – the more intense the beam the more quickly an experiment can be completed. Finally we want a beam in which the x-rays are all of one “color.” Color seems a strange word to apply to x-rays, but color is really the way that our eyes and brains record the energy of light. Light energy increases along the spectrum. Red light is low energy, blue is higher, and ultraviolet, which can damage our cells, is more energetic still.

For the first 75 years of x-ray science, x-rays were produced by tubes that looked like giant light bulbs. They met the criteria above only fairly well. For example, the tube creates x-rays that spray out in all directions. To get a parallel beam we put up a pipe (called a collimator) that collects all the x-rays going in the directions of its hole. All the x-rays going off in other directions go to waste. These tubes generate x-rays by crashing electrons into a metal target, and the “color” of the x-rays is determined by the choice of metal. Colors not emitted by some metal are impossible to create.

More recent x-rays sources are called synchrotrons. These are very large facilities to which scientists travel to conduct experiments. Synchrotron beams are naturally parallel, and users can tune them to get whatever “color” they want. These beams are also thousands of times brighter than those x-ray tubes mentioned above. Finally, the beams are actually composed of a series of very short pulses, about a millionth of a millionth of a second long. These short pulses turn out to be very useful for taking sophisticated snapshots of certain kinds.

How can we be so greedy as to want a new x-ray source when synchrotrons seems so wonderful? There are two experimental issues that cause considerable difficulties, and that in many cases preclude a successful experiment all together. The first is radiation damage. X-rays damage protein crystals just as they damage the proteins or DNA in our bodies. If the crystal is quite small, the damage can take place so rapidly that the crystals die before we can make measurements on it. Another issue is that attempts to grow protein crystals usually fail – only about 20% of proteins give useable crystals.

The XFEL can deal with both of these problems at the same time. The wonderful trick is that its beam is really a train of unimaginably short pulses: so short that the x-rays bounce off the crystal before the damage has time to take place. An instant after the pulse passes the crystal basically explodes, but only after the data have been generated. These same pulses also allow us to use crystals much smaller than we have ever been able to use before - and smaller crystals form much more readily. The XFEL pulses are so intense that they can bounce a measurable number of x-rays off a truly tiny crystal – as small as a few ten thousandths of an inch across.

So, if we are fortunate, the Center we help to establish will place us at the center of the development of this exciting technology. We will host an international conference each year, and will enroll many students to work on various aspects of the XFEL. And if the award does not come through, we have many other irons in the fire – subjects for future columns perhaps.