(Sandermann and Stromiger. 1972. J. Biol. Chem. 247:5123-5131.)
The advantage of this assay over the Lowry assay from which it is derived, is the presence of SDS in reagent A. This allows one to perform protein assays in nearly any detergent (eg., when detergents are used in the purification of outer membrane proteins). In addition, SDS separates membrane proteins from contaminating membrane constituents and denatures the proteins allowing more reproducible results.
2% Na2CO3, 0.02% NaK tatrate, 0.1M NaOH, 1% SDS (added last).
On the day of the assay mix 25ml of solution A with 1ml of solution B.
Dilute Folin reagent to 1N with deionized water.