Two major events affected the operation of the laboratory during the past year. Both events contributed to a decrease in the number of samples submitted. The total number of samples examined in 1997 was 185, and an analysis of the sample characteristics is presented in tables 1 and 2. A trend that is especially noteworthy is the increasing size of the target molecules. The largest structure completed during the year consisted of 252 non-hydrogen atoms.
Larger structures require more time for data collection, solution, and refinement.
During the year the rotating anode X-ray source and imaging plate data collection system from Molecular Structure Corporation was installed. A new liquid nitrogen cooled gas-flow system was also designed and constructed to cool the crystals on the new diffractometer. CCD Small Molecule Diffraction System. The proposal was funded and two site visits were made to examine available systems. Bids for the CCD instrument will be requested early in 1998.