Obituary of Gerard John Bunick

Gerard John Bunick, Research Professor at the University of Tennessee/Oak Ridge Graduate School of Genome Science and Technology, died of multiple cancers on Sept. 19, 2007 at Methodist Medical Center of Oak Ridge. Born on May 27, 1947, in Boston, Massachusetts, he obtained a B.S. in chemistry in 1969 at the University of Massachusetts at Amherst. His graduate studies at the University of Pennsylvania with Donald Voet, resulting in a Ph.D. in 1975, involved the crystal structures of models for protein-nucleic acid interactions together with the structure of the enzyme yeast inorganic pyrophosphatase.

In August 1977 Gerry then went to the Chemistry Division at Oak Ridge National Laboratory, and was a Staff Member in the Solid State Division from 1982 to 1990. He then became a Senior Staff Member in the Biology Division of the Life Sciences Division. He also had appointments at University of Tennessee/Oak Ridge Graduate School of Genome Science and Technology where he was a Research Professor.

Gerry was meticulous in his laboratory work. His father was a research machinist at MIT and Gerry inherited an amazing ability to use complicated instruments and to service them when they failed. This was very useful to him in the course of his career, and was a skill he inculcated in those working in his group.

Gerry investigated methods for producing better macromolecular crystals for diffraction studies. He pioneered the use of macromolecular crystal annealing to reduce any mosaicity acquired by crystals during flash cooling. In this technique a flash-cooled crystal is transferred to a droplet of the original cryoprotectant solution at ambient temperature for about three minutes and then is reflashed to a cryogenic temperature. Details of this method were worked out by Gerry. In order to improve crystal quality Gerry grew macromolecular crystals on NASA and MIR space flights; some of the crystals that were obtained were large and of acceptable quality for neutron diffraction experiments.

Gerry focused his interests on chromatin structure and gene regulation, and studied the structure of the nucleosome core. This was a huge task and he was not the first to publish the entire structure which was reported in 1997 at 2.8 Å resolution. However Gerry’s work provided much additional information when his 2.5 Å structure was published in 2000. A DNA palindrome was a feature pioneered by Gerry and his group and essential for obtaining the structure of the nucleosome core particle (Acta Cryst. D52, 283). Palindromic DNA had been expected to form a perfectly twofold symmetric nucleosome core particle. In fact the result was found to be asymmetric because of the manner in which the DNA binds to the protein surface and nucleosomes pack in the crystal.

Gerry more recently tackled the determination of hydrogen positions in enzymes that transfer hydrogen ions as part of their mechanism of action. In analyses of D-xylose isomerase he compared the structure at 0.94 Å resolution at 100 K from X-ray diffraction data, with time-of-flight neutron diffraction data measured at room temperature at 1.8 Å resolution at Los Alamos on a deuterated enzyme crystal. He showed the protonation state of one histidine residue, ready to act on the substrate and open its ring structure. He also showed that a metal ion binds a water molecule (rather than hydroxyl group even though the pH was 8.0) and that one lysine has only two, rather than three, hydrogen atoms attached to its terminal nitrogen atom. This work showed how productive a comparison of X-ray and neutron diffraction results can be.

Gerry played a central role in aggressively pushing back the experimental limitations of macromolecular neutron crystallography. When the Protein Crystallography Station (PCS) was built at Los Alamos, breaking new ground for structural biology by becoming the first of its kind in the world at a spallation neutron source, Gerry was the first official user, collecting a data set from D-xylose isomerase which, in 2003, was the largest enzyme ever studied by neutron crystallography. Gerry was at the heart of developing the case for a new neutron beam line at the next generation spallation neutron source (SNS) at Oak Ridge. With the SNS ramping up in power to become the worlds most powerful neutron source and the Macromolecular Neutron Diffraction (MaNDi) beam line in the first stages of design and construction, perhaps the biggest impact of Gerry’s influence in this field will only be realized in 4-5 years time when MaNDI and the SNS are operating at full speed.