Chemistry

ABSTRACTS

Dr. Markus Germann, Georgia State University: "DNA Damage and Recognition by the Repair Machinery: Structure and Dynamic Markers"

Nucleic acids play a central role in many biological processes. Their functions include information storage and controlling gene expression. Many external and internal processes damage DNA, moreover mismatches can arise form a variety of sources. It is vital for the survival of organisms that such damage is recognized and repaired. Here we discuss recognition strategies used by different repair system to accomplish this task.

Dr. Craig Barnes, UTK: "The Design, Synthesis and Reactivity of Nanostructured Metal Oxide-silicate Catalysts"

Nanostructured heterogeneous catalysts may be defined as materials in which the form and structure of the catalyst-support matrix are designed and simultaneously controlled at several different length scales.  At the level of the active site itself, nanostructuring requires that we be able to identify and target specific arrangements of metals and ligands such that a desired catalyst “ensemble” is obtained and all other potential metal species excluded (the definition of a single site catalyst).  In the context of metals on the surfaces of metal oxide supports, some tailoring of the surface functionality that both holds them in place and contributes to the sphere of coordinating ligands must take place as the catalyst ensemble is developed.  Catalytic activity is directly proportional to the number of accessible sites in the system.  Therefore, a second goal in developing nanostructured catalysts is to achieve the highest density of sites possible within the support matrix while maintaining site isolation.  Finally, all sites must be accessible and mass transfer rates should be as high as possible.  An operational target satisfying this goal is to achieve a distribution of meso and microporosity throughout the solid analogous to vascular systems found in plants and animals. 

Such “next generation” catalysts will require entirely new synthetic approaches than are currently available.  Our efforts to articulate a general methodology for the preparation of single site, nanostructured catalysts based upon a silicate building block and a wide variety of metal and main group linking reagents will be described.  Specific examples involving Ti, V, Al and Sn will be discussed.

Dr. Christoph Fahrni, Georgia Tech, "Cellular Imaging of Trace Metals"

Approximately one third of the human proteome contains metal cations, either in form of cofactors with catalytic functions, or as structural support. At present, still little is known about the cellular structures that are involved in transiently storing metal ions as part of cellular homeostasis. An important first step towards unraveling the regulatory mechanisms involved in trace metal transport, storage, and distribution represents the identification and quantification of the metals, ideally in context of their native physiological environment in tissues, cells, or even at the level of individual organelles and subcellular compartments. Metal-responsive fluorescent probes are powerful tools for exploring the biological chemistry of trace elements in living cells. To develop fluorescent probes for the selective detection of zinc and monovalent copper in a cellular environment, several different fluorescence switching mechanisms were explored, including photoinduced electron transfer as well as modulation of intramolecular charge transfer states through cation coordination and conformational switching. Detailed analysis of the underlying photophysical mechanisms allowed for precise tuning of the fluorescence properties and switching responses. In addition, we utilized synchrotron x-ray fluorescence microscopy to image the subcellular distribution of the total trace metals pools with submicron resolution and to correlate the optical imaging data.