Acidic amino acids: A new-type of enzyme mimics with application to biosensing and evaluating of antioxidant behaviour.

Nanomaterials have triggered tremendous interest to mimick peroxidase but rarely attention has been paid to small molecules. Herein we first found that acidic amino acids including l-glutamic acid (L-Glu) and l-aspartic acid (L-Asp) exhibited an intrinsic peroxidase-like activity, endowing acidic amino acids with the capability of catalysing the oxidation of the peroxidase substrates 3,3',5,5'-tetramethylbenzidine (TMB) to produce color reaction in the presence of HO. Reaction mechanism was further investigated by means of electron spin resonance spectroscopy (ESR), enzyme kinetics assay and quantum theoretical calculations, to verify and provide a good deal of insight into the catalytic process.