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P042 Novel agents for the in-situ detection of cysteine oxidation states Shibani N. Ratnayake, Eric Lattmann and Helen R. Griffiths Aston University, Birmingham, UK Cysteine (Cys-SH) readily undergoes oxidation by reactive oxygen species (ROS) to form sulfenic (Cys-OH), sulfinic (Cys-SO2H) and sulfonic (Cys-SO3H) acids. Thiol modifications of cysteine have been implicated as modulators of cellular processes and represent significant biological modifications that occur during oxidative stress and cell signalling. However, the different oxidation states are difficult to monitor in a physiological setting due to the limited availability of experimental tools. Therefore it is of interest to synthesise a range of chemical probes that selectively recognise specific oxidation states of cysteine. The current study is aimed at investigating a synthetic approach for novel fluorescent probe synthesis, for the specific detection of cysteine sulfenic acids by fluorescence spectroscopy. N-[2-(anthracen2-ylamino)-2-oxoethyl]-3,5-dioxocyclohehanecarboxamide, fluoresceneamine-5-N-(3,5-dioxoxyxlohexane)carboxamide and 3,5-dioxo-N-(2-phenylethyl)cyclohexanecarboxamide have successfully been synthesised and confirmed by nuclear magnetic resonance spectroscopy. Optimal conditions for testing the novel probes, using the oxidation of cysteine moieties to produce sulfenic acid by hydrogen peroxide mediated oxidation of human serum albumin, are described. Sulfenic acid was detected using the commercial, non-fluorescent probe DCP-Bio1. Jurkat T cells have been used as a model to investigate sulfenic acid modifications in a cell lysate and membrane fraction pre- and post- stimulus. Membrane proteins of resting Jurkat T cells have sulfenic acid modifications and 2 prominent bands are detected by SDS-PAGE and western blotting with molecular weights of approximately 25kDa and 50 kDa. Their identity is under investigation by LC-MS/MS.