TOAC, a nitroxide spin-labeled, achiral C-alpha-tetrasubstituted alpha-amino acid, is an excellent tool in material science and biochemistry

The 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid is a nitroxide spin-labeled, achiral C(alpha)-tetrasubstituted alpha-amino acid that has recently been shown to be an effective beta-turn and 3(10)/alpha-helix inducer in peptides and an excellent and relatively rigid electron spin resonance probe and fluorescence quencher.