|| X-Ray Diffraction
X-ray diffraction studies at the NIH date from the early 1950s (Davies, Dunitz, Felsenfeld, and Rich). Fiber diffraction work on synthetic polyribonucleotides, initiated in 1955, led to the proposal of three-stranded and other forms of association (Davies, Felsenfeld, and Rich). Interest in multi-stranded nucleic acids also resurfaced at a later date in proposals for four-stranded structures that are now believed to play a role in telomere organization. Fiber diffraction experiments on muscle were initiated in the 1970s (Podolsky and Yu) and continue fruitfully today. The first protein crystallography on campus was carried out in the 1960s with a structure determination of g-chymotrypsin, followed by a series of studies on antibodies and their Fab fragments, both alone and in complex with antigens. Subsequent research has been extended to other proteins, in particular, to several kinds of proteases and many other enzymes. In recent years, crystallography at the NIH has proliferated to a total of 17 groups, on the Bethesda campus (Buchanan, Davies, Dyda, Hurley, Kwong, Mayer, Xia, Xiao, Yang, and Yu), at the NCI-Frederick (Ji, Lubkowski, Waugh, and Wlodawer), at Twinbrook (Sun), at the Research Triangle Park (Hall), and at the Advanced Photon Source (Dauter), creating a critical mass of expertise and a cooperative, well-equipped environment in which the structures of a wide variety of proteins and other macromolecules are vigorously pursued. In addition to the 17 groups, macromolecular crystallography has been integrated into more and more laboratories that are not specialized in X-ray diffraction.