The development of oxaziridine-based methionine spin-labels for EPR Siyao Chen, Gordon J. Florence and Bela E. Bode University of St Andrews, UK Methionine (Met) is a sulfur-containing proteinogenic amino acid playing various biophysical and biochemical functions. Due to its rare occurrence on the protein surface, Met has become a potentially greater protein modification target without modifying and compromising other surface-accessible amino acid residues. Therefore, the physiological function of modified proteins will not be interfered with. Recently, redox-activated chemical tagging (ReACT) has become the first method to modify Met residues specifically over other nucleophilic amino acids at physiological conditions ( Scheme 1 ). 1 A novel application of ReACT has been proposed in the Florence group: combining site-directed spin-label (SDSL) with Met-specific ReACT. Due to Met’s rareness on the protein surface, ReACT will only modify Met residues introduced by site-directed mutagenesis of proteins with a low risk of affecting the protein’s normal function. This offers potential advantages over the use of SDSL probes to modify cysteine (Cys) residues. This poster details synthetic access to a range of nitroxide radical-containing oxaziridine probes and assessment of their selectivity towards Met over Cys and other amino acid residues. Currently, pyrroline nitroxide radical oxaziridine has been found with a 100-fold selectivity on Met over Cys, and further chemical modifications will be carried out to improve the selectivity.
Scheme 1. Schematic presentation of methionine selective ReACT References 1. S. Lin, X. Yang, S. Jia, A. M. Weeks, M. Hornsby, P. S. Lee, R. V. Nichiporuk, A. T. Iavarone, J. A. Wells, F. D. Toste and C. J. Chang, Science , 2017, 355 , 597–602.
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