Application of the Ninhydrin Reaction for Quantification of Total Protein Contents: Establishment of Conversion Formulas.

ABSTRACT: The ninhydrin assay is an interesting alternative for protein quantification to the widely used Kjeldahl and elemental analysis methods. The two latter methods only measure the nitrogen content that must be converted into the protein content using empirical factors. In contrast, the ninhydrin reaction is more selective and reacts with primary amines including α-amino acids but not with nitrate and nucleic acids, the main source of nonprotein nitrogen in biological samples. Here, we determined the protein contents of a number of samples with the Kjeldahl method and elemental analysis and measured the amount of liberated amino acids using the ninhydrin assay. These results allowed establishing a universal formula ω(P) = (AA - 0.21) × 11.2 for conversion of the amino acid content (AA, in mmol

SUBMITTER: Alcock K 

PROVIDER: S-EPMC12921656 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature