Obituary of David Sayre (1924-2012)

David Sayre, a pioneer crystallographer, a member of the team that wrote the original FORTRAN compiler, and a visionary leader in X-ray microscopy, died on February 23, 2012.

David received his B. S. from Yale at the age of 19. During the last year of World War II he worked on Radar at the MIT Radiation Laboratory, before going to graduate school. He received his Ph. D. from Oxford University in 1951, working with Dorothy Hodgkin. It was during this time that David and his wife Anne got to know Rosalind Franklin, another young crystallographer, working at Kings College, London.

David wrote some of his seminal papers during the 1951-52 period. It was then that he discovered what is know today as Sayre’s equation, and which was the first and critical step in the development of direct methods in crystallography. His half-page 1952 paper “Some implications of a Theorem due to Shannon” forms the foundation of diffraction microscopy, and 50 years later is still frequently cited in the literature.

Between 1956 and 1990 Sayre worked for IBM, where he was Assistant Manager of the Fortran Development Group and later Corporate Director of Programming. In the 1960’s he lead the Programming Research Group that developed the first virtual memory operating system. In 1971 he proposed that IBM’s newly developed electron beam microfabrication technique be used to make Fresnel zone plates for X-ray microscopy. It took a decade for this idea to be realized, but it is now the basis of the rapidly growing field of X-ray microscopy at synchrotron light sources world wide, and of commercial laboratory instruments made by the company, Xradia, founded by one of Sayre’s first Ph. D. students, Wenbing Yun.

In 1972-73 the Sayres returned to Oxford where David once again worked in Dorothy Hodgkin’s lab. This was after the publication of the book by James Watson, the Double Helix, in which the author treated the contributions of Rosalind Franklin to DNA structure determination in a scandalously dismissive way. This inspired Anne Sayre to write the book “Rosalyn Franklin and DNA”, a book that became a best seller, and went a long way toward setting the record straight.

Subsequently David turned his attention to X-ray microscopy. He realized that due to the short wavelengths involved, X-rays could reach higher resolution than standard visible light microscopes, and due to the penetrating nature of the radiation, they would not be limited to ultrathin samples as electron microscopes are. He worked on contact microscopy at IBM, and later became involved with the development of microscopes using the National Synchrotron Light Source at Brookhaven National Laboratory.

After his retirement from IBM, he served as Adjunct Professor at Stony Brook University. Sayre’s last great scientific contribution was Diffraction Microscopy, or Coherent Diffraction Imaging. In 1980 he realized that synchrotron lightsources may be powerful enough to provide sufficient coherent X-rays so that the diffraction pattern of non-crystalline specimens could be recorded. These patterns would be continuous, and not restricted to Bragg peaks. He conjectured that even though only the intensity could be recorded and not the phase, the information could be sampled on a much finer grid than Bragg peaks from crystals, and this may make the phase reconstruction possible.

In the 1980’s he succeeded in recording the first diffraction patterns from non-crystalline samples. In the 1990’s, working with Henry Chapman (then a Stony Brook postdoc) and John Miao (then a graduate student), he was able to apply James Fienup’s iterative algorithm to find the phases for a computer generated diffraction pattern. The final breakthrough came when Miao succeeded in reconstructing an experimentally recorded diffraction pattern. This achievement opened up the field of diffraction microscopy, now practiced in different forms at many lightsources around the world, and which is playing a critical role in the experimental program at recently developed free electron lasers such as the Linac Coherent Lightsource at SLAC.

During his career, Sayre served on numerous committees. In 1983 he was President of the American Crystallographic Association. He received the organization’s Fankuchen Award in 1989. In 2008, at the triennial Congress in Osaka he received the highest award of the International Union of Crystallography, the Ewald Prize. David was a superb scientist, a warm hearted colleague, and an exceptional mentor. He was preceded in death by his wife, Anne. He is greatly missed. Chris Jacobsen, Argonne National Laboratory and Northwestern Univeristy Janos Kirz, Lawrence Berkeley National Laboratory John Miao, UCLA