The DC™ (detergent compatible) protein assay is a colorimetric assay for protein concentration following detergent solubilization. The reaction is similar to the well-documented Lowry assay, but has been modified to save time. The DC protein assay requires only a single 15 minute incubation, and absorbance is stable for at least 2 hours.
Using standard procedure, the assay is used with samples having protein concentrations between 0.2 and 1.5 mg/ml and requires just 100 µl of sample. The procedure can easily be adapted to a low-concentration microassay (see below). The microplate assay reduces the volume of sample required to just 5 µl. The DC protein assay is measured at 650–750 nm with a standard laboratory spectrophotometer or microplate reader.
DC protein assay kits offer either bovine serum albumin or bovine γ-globulin standard sets.
For lower concentrations of protein, the microassay procedure can be used in a standard test tube or in a microplate format. The microassay procedure can be used to measure protein concentrations from 5 to 250 µg/ml; it requires 200 µl of sample for the test tube assay or 20 µl of sample for the microplate assay. When using the microassay format, the kit contains enough reagent for 2,500 standard assays or 25,000 microplate assays.
Because the ratio of sample to reagent is changed, compatibility changes when using the microassay. The DC protein microassay is not compatible with 2-mercaptoethanol, dithiothreitol, or guanidine HCl.