NPD2 (N-phenyl-1-naphthylamine-2-sulfonic acid) and PMA (phenylmalonic acid) are both derivatives of phenylalanine. NPD2 is a sulfonic acid, while PMA is a dicarboxylic acid. Both compounds are used as fluorescent dyes. NPD2 is used in the detection of proteins, while PMA is used in the detection of metal ions.

NPD2 is a water-soluble dye that emits blue fluorescence when excited by ultraviolet light. It is used in the detection of proteins because it binds to the amino acid tryptophan. The binding of NPD2 to tryptophan causes a change in the fluorescence emission spectrum of the dye, which can be used to quantify the amount of protein present.

PMA is a water-soluble dye that emits green fluorescence when excited by ultraviolet light. It is used in the detection of metal ions because it forms complexes with metal ions. The formation of these complexes causes a change in the fluorescence emission spectrum of the dye, which can be used to quantify the amount of metal ion present.

NPD2 and PMA are both sensitive and selective dyes for the detection of proteins and metal ions, respectively. They are used in a variety of applications, including the analysis of biological samples, the detection of environmental pollutants, and the development of new drugs.