Which of the following scenarios best illustrates the appropriate application of the Folin phenol reagent in protein quantification?

The Folin phenol reagent is used in the Lowry protein assay, which measures protein concentration by reacting with peptide bonds and aromatic amino acids to produce a blue color. This reagent is best applied when you need a sensitive assay for low‑concentration protein samples, such as measuring the amount of a purified enzyme before an activity assay. For instance, if you isolate a recombinant protein at 0. 5 mg mL⁻¹ and want to confirm its concentration, you would mix it with the Folin reagent, add alkaline medium, and measure the absorbance at 750 nm to calculate the protein amount. The key idea is that the reagent’s reaction with proteins yields a quantifiable color change that is proportional to protein mass, making it ideal for accurate protein quantification in biochemical experiments.