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Prof. Bowman’s research interests center on free radical reactions in proteins and other ordered but non-crystalline environments and on the application of pulsed EPR spectroscopy to determine the structure and function of enzymes, free radicals and materials.
Pulsed Electron Paramagnetic Resonance Spectroscopy
Electron Paramagnetic Resonance (EPR) is a branch of spectroscopy that observes the spin of unpaired electrons in free radicals, excited states of molecules, metal ions and magnetic materials. Because the unpaired electrons are often the most reactive sites, EPR provides a highly selective method to study the sites that are most interesting to chemists, biologists and physicists. Pulsed EPR methods now provide ways to determine the structure, function and dynamics of proteins, free radicals and magnetic materials.
Current research involves the used of pulsed EPR to measure nanometer distances within proteins and nucleic acids to determine their structure and how their structure changes as part of their biological function. Another area of research involves measurement of the spatial distribution of radiation damage in DNA in order to understand how clusters of multiple damage sites affect the biological repair of radiation damage.
Structure and Function of Metalloproteins
Large, complex proteins catalyze a wide variety of chemical reactions at room temperature and pressure. Some reactions, such as water splitting in photosynthesis or nitrogen fixation, can only be done inefficiently in the laboratory under extreme conditions. Other enzyme reactions, such as stereospecific chemical synthesis can be done in the laboratory but with unwanted by-products that must be removed.
Current research focuses on the cytochrome bc1 complex which sits in the mitochondrial membrane and uses electron transport to pump protons across the membrane and provide the driving force for ATP synthase. Under some conditions, the cytochrome bc1 complex can be diverted into producing the toxic molecule superoxide. This production of superoxide is alleged to be involved in ageing, carcinogenesis, Type II diabetes and several genetic diseases. An important question is how this enzyme avoids producing superoxide under normal conditions and whether superoxide production can be turned on in disease causing organisms to kill them without turning it on in the host.
Defect Centers in Crystalline and non-Crystalline solids
The electronic, magnetic and optical properties of many materials are modified by adding small amounts of impurities or dopants. How these dopants are incorporated into the material and affect the local structure can have a major effect on its properties. EPR is one of the few spectroscopic methods capable of determining the electronic and physical structure of the dopant and in distinguishing between dopants incorporated into the material in different sites.
Current research involves studies of SiO2, TiO2 and ZrO2 crystals doped with different anions or cations. In TiO2, metal ions occupy several different interstitial sites and change the crystal from completely colorless to blue-black or grey and convert it from an insulator into a semiconductor. Once the EPR spectral parameters have been identified from careful single crystal measurements, those species can be identified in nanoparticles of TiO2 and correlated with the properties of those nanomaterials.
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