Notes of a protein crystallographer: my nights with ACTOR

It would have appeared to be an impossible dream in the late sixties, when the ®eld of protein crystallography ®rst became established, just as the structures of myoglobin and hemoglobin were ®rst unveiled. Even if somebody would have thought about it in the early seventies, when protein crystallography was`coming of age' (Cold Spring Harbor Symposium, 1971), it would have still seemed utterly impossible or even a miracle. Yet, only 30 years later, here I am late at night putting a protein crystal in front of an extremely brilliant X-ray beam using a computer-controlled robot to mount, center and expose a protein crystal in front of the X-rays emanating from a third-generation synchrotron source. My diffraction data from this crystal will be collected in approximately 15 minutes, processed, as it is being collected, reduced and scaled a few minutes later. Things going well, the three dimensional structures of the protein and various ligand(s) within these crystals will be unveiled tomorrow and presented and discussed with chemists, biologists, pharmacologists rapidly. The detailed analysis will aid and direct the synthesis of new compounds for several drug-design projects. In a year or so, after several iterations of the process, the resulting optimized compound with the most suitable pharmacokinetic properties could be selected for clinical testing. After rigorous clinical studies, it might become one of those rare chemical entities with a therapeutic effect on a speci®c patient population. Am I talking science ®ction? Certainly not. This is the current state of macromolecular crystallography in certain industrial laboratories and other general user facilities at synchrotrons, and this modus operandi will soon spread to a sizeable portion of the laboratories around the world. How did this all happen? Who were the people involved in these amazing technological advances? What are the implications of these developments for the future of the ®eld? There was a sequence of modest, somewhat unrelated changes in the way that the macromolecular crystals were handled that has turned out to be of tremendous importance. A little bit of historical background is necessary to put this in perspective. Besides having read about it in the textbooks, the new generation of protein crystallographers may never have mounted a protein crystal in a glass or quartz capillary, the way it was done in the past. This was the critical observation by Bernal and Crowfoot in their 1934 Nature paper (Bernal & Crowfoot, 1934). Protein crystals needed …