First 11 pages of thesis. - OPUS - Universität Würzburg
First 11 pages of thesis. - OPUS - Universität Würzburg
First 11 pages of thesis. - OPUS - Universität Würzburg
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Figure 7: Principle <strong>of</strong> ESR spectroscopy. (Picture from Bruker Biospin GmbH, Karlsruhe,<br />
Germany).<br />
Free radicals like nitric oxide, superoxide and peroxynitrite are too low in<br />
concentration and too short lived to be directly detectable by ESR in biological<br />
systems. This problem can be overcome by the addition <strong>of</strong> exogenous spin<br />
traps that react with free radicals to form secondary ESR detectable radicals<br />
with a higher stability. These spin traps, frequently nitroxide and nitrone<br />
derivatives, can also be used to label biomolecules and probe basal and<br />
oxidation induced events in protein and lipid microenvironments. With a<br />
sensitivity limit <strong>of</strong> ~10 -9 mol/L, ESR spectroscopy is also capable <strong>of</strong> detecting<br />
the more stable free radical species produced in the vascular compartment<br />
during oxidative stress and inflammation, including ascorbyl radical,<br />
tocopheroxyl radical, and heme-nitrosyl complexes directly 189 .<br />
Reaction <strong>of</strong> nitric oxide with endogenous heme and non-heme iron<br />
proteins leads to the formation <strong>of</strong> iron-nitrosyl complexes with characteristic<br />
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