Explain 3 nanomoles of free amino acid tyrosine gives less r

Explain: \"3 nanomoles of free amino acid tyrosine gives less reaction in the Lowry assay than 1 nanomole of a tripeptide containing 3 tyrosines\" Why

Solution

The principle behind the Lowry method of determining protein concentrations lies in the reactivity of the peptide nitrogen[s] with the copper [II] ions under alkaline conditions.

As free amino acids do not have peptide bond therefore effective formation of color complex with Cu⁺⁺ ion is not there.

In the case of tripeptide peptide nitrogen is available for the reaction hence gives more reading compared to free amino acids.