PROTEIN MEASUREMENT WITH THE FOLIN PHENOL REAGENT¶
Why this mattered¶
Lowry, Rosebrough, Farr, and Randall’s paper mattered because it turned protein quantification into a sensitive, practical routine measurement. Earlier protein assays existed, including Folin-based methods after Wu, but the Lowry procedure combined the copper-protein reaction under alkaline conditions with reduction of the Folin phenol reagent, producing a much stronger color response. That made it possible to measure much smaller amounts of protein than many prevailing methods, using ordinary laboratory spectrophotometry rather than specialized instrumentation.
The shift was methodological but broad: once protein could be measured reliably at microscale, biochemical experiments became easier to normalize, compare, and reproduce. Enzyme activities could be expressed per milligram of protein; cell fractions, tissue extracts, serum samples, and purified preparations could be tracked quantitatively through isolation steps; and small experimental samples no longer had to be discarded as analytically inaccessible. The paper did not discover a new protein or pathway, but it supplied one of the measurement foundations that made postwar biochemistry more quantitative.
Its influence is visible in the later expansion of enzymology, cell biology, protein purification, membrane biochemistry, and molecular biology, where protein concentration became a routine denominator for experimental claims. The assay’s limits, including sensitivity to reagent timing, protein composition, detergents, and reducing agents, eventually motivated alternatives such as Bradford and bicinchoninic acid assays. Even so, the Lowry assay became a canonical laboratory standard because it made protein measurement cheap, sensitive, and widely transferable across biological systems.
Abstract¶
Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins (l), a number of modified analytical procedures ut.ilizing this reagent have been reported for the determination of proteins in serum (2-G), in antigen-antibody precipitates (7-9), and in insulin (10).
Related¶
- enables → A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding — The Lowry Folin phenol protein assay established colorimetric protein quantitation that the Bradford dye-binding assay later made faster and more sensitive.
- enables → The Carbon Monoxide-binding Pigment of Liver Microsomes — The Lowry Folin phenol assay enabled protein quantification needed to characterize cytochrome P-450 as the carbon monoxide-binding pigment of liver microsomes.
- enables → A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding — The Lowry Folin phenol assay set the standard for protein quantitation, which the Bradford dye-binding method improved with faster microgram-scale measurement.
- cite ← A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding — Bradford's protein-dye binding assay is presented as a faster, more sensitive alternative to Lowry's Folin phenol protein quantitation method.
- cite ← The Carbon Monoxide-binding Pigment of Liver Microsomes — The liver microsome pigment study uses the Lowry Folin phenol assay to quantify protein in microsomal preparations.
- cite ← A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding — The Bradford protein assay cites the Lowry Folin phenol method as the prior standard for colorimetric protein quantitation that Bradford sought to simplify and speed up.