The spin trap 2-methyl-2-nitrosopropane (MNP). This diamagnetic molecule forms adducts with unstable free radicals to form a more stable paramagnetic nitroxide radical that can be detected by electron spin resonance spectroscopy. It is particularly useful for trapping carbon-centered tyrosyl radicals [eg. see J. Biol. Chem. 271 (1996), 15498-15503].