5-​[[[[[(5S)​-​5-​Amino-​5-​carboxypentyl]​amino]​carbonyl]​oxy]​methyl]​-​1,​3-​dihydro-​1,​1,​3,​3-​tetramethyl-2H-​isoindol-​2-​yloxy, a spin-labeled reagent, was used as tyrosine aminoxy radical derivative to generate proteins having genetically encoded spin labels.