The UK Chemistry X-Ray Laboratory is located in room 146 of the Chemistry-Physics Building

Views of the X-Ray Laboratory

The X-Ray laboratory is packed full of modern scientific equipment. We have a Nonius kappaCCD machine with a sealed-tube molybdenum X-ray source and a new specially configured machine based on the Bruker-Nonius X8 Proteum. The former was installed in 1998 and features a low-temperature machine from CryoIndustries of America. The big new machine pictured above right (and on the main page) was designed as a hybrid small-macromolecule diffractometer. It features a rotating anode (both Cu and Mo), kappa diffractometer, large-format (4Kx4K) CCD detector and large (Bruker "Helios") graded multilayer optics for both Cu and Mo x-rays. It has the same nitrogen-based low-temperature device as the older kappaCCD, but also has a He-based crystal cooler that can achieve ultra-low crystal temperatures of about 5K. This machine, obtained in 2004 with funding from the Major Research Instrumentation program of the NSF and a generous match from the University of Kentucky, is probably the world's most powerful diffractometer housed within an academic chemistry department. By careful design and integration of its component parts, it is also one of the most versatile diffractometers.

The picture above left shows the kappaCCD diffractometer and that on the right shows the X8 Proteum.

The low-temperature machine below delivers a constant, low-velocity flow of cold nitrogen gas over the crystal during data collection. Low temperature has many benefits for X-ray structure determination, including better quality data in less time than room-temperature work and the ability to handle highly reactive compounds with minimal fuss. We typically collect data at 90K, but on occasion, destructive phase transitions force data collection at higher temperatures. Fortunately the Cryo Industries control box on the left makes changing temperature quick and painless.

High-quality stereo optical microscopes are also an essential feature of any well-equipped X-ray laboratory. We have two main microscopes - an Olympus SZX12 stereo research microscope, and its brother, the SZX9. The SZX12 sits on a specially designed and built low-profile light box allowing both transmitted and reflected light and is equipped with easily interchangeable polarizers and filters. Since our recently installed big diffractometer is able to handle crystals well over a thousand times smaller than conventional diffractometers, we also have special add-on objectives and higher-power eyepiece lenses to aid in crystal selection and microsurgery. The SZX9 has an Olympus ILL-D base, again allowing reflected and transmitted light. Rotating stages are an absolute necessity for crystal inspection. Our preferred stage for the SZX12 (below right) is actually a Supper film measuring device. It is large, flat and easily positioned, and is thus much more convenient than ordinary rotary microscope stages. The stage on the SZX9 was custom-made by our superb machine shop, which is housed in the Physics end of the building, it is a sort of cross between the Supper stage and the dedicated offerings of the microscope companies.

The video camera shown in the picture above middle (attached to the SZX12) is invaluable for teaching crystal manipulation techniques. For quality stills we have interchangeable high-resolution digital cameras (normally attached to the SZX9).

Modern X-ray crystallography can be a compute-intensive endeavour. The X-ray laboratory is well equipped for crystallographic computations with a half dozen Linux computers for data collection, structure solution/refinement and for the Cambridge Structure Database. Macintosh (OS X) computers (desk and laptop) are housed in the Director's office (CP-135) and in the graduate student office, which is conveniently located in a separate room at the back of the X-ray laboratory. We even have a couple of Windows machines, though of course, not by choice. They are carefully and purposefully positioned behind Linux firewalls where they hopefully can cause no damage.

 


These pages are (c) Dr. Sean Parkin, Director, X-Ray Laboratory, Department of Chemistry , University of Kentucky
phone : (859) 323-8984, fax : (859) 323-1069, e-mail : spark2@uky.edu