Project Summary: Background and Challenge: Peroxynitrite (OONO-) emerged as a potent cytotoxic compound and has been implicated in a host of pathophysiological conditions. Peroxynitrite is the primary product of the in vivo reaction of nitric oxide and superoxide anion-radical. The multifaceted physiologic reactions of this compound are directly implicated in a number of pathologies including cardiovascular disease, immune response, chronic inflammation, and sepsis, to cite a few. According to recent statistics by the American Heart Association, just cardiovascular disease alone claims about 7 deaths every 4 minutes. On the other hand, sepsis affects 1.7 million adults in the United States each year and potentially contributes to more than 250,000 deaths. Just these two statistics are staggering and make the footprint of this deadly biological analyte an important priority. The common thread that links peroxynitrite to all cited pathologies is its potent reactivity toward most cellular components including DNA, proteins, and lipids in cell membranes. Substantial oxidations and other transformations of proteins, DNA, and lipids contribute to the disruption of key cellular functions. Assessing peroxynitrite’s deleterious effects and examining hypotheses of its potential signaling roles cannot be achieved without first accurately measuring and monitoring its concentration. This task is however inherently difficult due to low submicromolar concentrations under physiologic conditions coupled with its high reactivity. Sensitive and accurate measurement of peroxynitrite is crucial in order to shed light on the illusive pathophysiologic roles of this metabolite. Some of the known detection methods for peroxynitrite include oxidation of fluorescent probes, EPR spectroscopy, chemiluminescence, immunohistochemistry, and probe nitration; however, these are more difficult to apply for real-time quantification due to their inherent complexity. The electrochemical detection of peroxynitrite is a simpler and more convenient technique for application in biological settings. However, a systematic development of the right electrode interface that enhances the sensitivity and selectivity for this molecule is lacking. Recently, several synthetic organic selenides have been prepared as antioxidants in medicinal chemistry. Electrochemical data in our hands showed that some organoselenium compounds have specific redox activity with peroxynitrite in solution. For these reasons, we believe that an electrode interface decorated with organoselenides attached to the surface will potentially serve as catalytic entities for mediated PON electrocatalytic determination. Our proposal: In this work, we propose to develop a functional thin film material based on defined organic selenides chemically attached on graphite electrodes and use this interface in sensitive electrochemical determination of peroxynitrite. This bottom-up interface design approach is innovative because it a...