DC™ Protein Assay



Protein Concentration Test Tube Microplate
High-concentration assay 0.2–1.5 mg/ml protein 0.2–1.5 mg/ml protein
  100 µl sample 5 µl sample
  500 µl reagent A 25 µl reagent A
  4.0 ml reagent B 200 µl reagent B
Low-concentration assay 5–250 µg/ml protein 5–250 µg/ml protein
  200 µl sample 20 µl sample
  100 µl reagent A 10 µl reagent A
  800 µl reagent B 80 µl reagent B
Compatible Reagents*
Brij 35, 1% Guanidine-HCl, 0.4 M Sodium hydroxide, 0.5 M
C12E8,** 0.2% HCl, 0.5 M Thesit, 1%
Calcium chloride, 50 mM (NH4)2SO4, 0.5 M Tris, pH 8, 0.1 M
CHAPS, 1% Nonidet P-40 (NP-40), 2% Triton X-100, 1%
CHAPSO 1% Octyl-β-glucoside, 1% Tween 20, 1%
DTT, 1 mM SDS, 10% Urea 4 M
EDTA, <1 mM Sodium azide, 0.05%  
* Using standard procedure.
** Octaethyleneglycol dodecyl ether.
Protein Assay Selection Guide

Chart RC DC Protein Assay DC Protein Assay Quick Start Bradford Assay Assay Bio-Rad Protein Assay

  * Nonidet P-40 >0.25%, Triton C-100 >0.05%, Tween 20 >0.01%, SDS >0.025%
** DTT >1 mM, EDTA >1 mM

Protein Assay Comparison
Characteristics of Bio-Rad's Protein Assays
  Protein Assay
Quick Start™ Bradford Bio-Rad DC RC DC™
Adapted from method of Bradford (1976) Bradford (1976) Lowry et al. (1951) Lowry et al. (1951)
Standard concentration assay        
Sample volume 100 µl 100 µl 100 µl 100 µl
Linear range 0.125–1.5 mg/ml 0.2–1.5 mg/ml 0.125–1.5 mg/ml 0.125–1.5 mg/ml
Low-concentration assay        
Sample volume 1 ml 800 µl 200 µl 200 µl
Linear range 1.25–25 µg/ml 1.25–25 µg/ml 5–250 µg/ml 5–250 µg/ml
Microplate assay sample volume 5 µl 10 µl 5 µl *
Minimum incubation time 5 min 5 min 15 min 15 min
Assay wavelength 595 nm 595 nm 650–750 nm 650–750 nm

All assays are easy to use, require little reagent preparation, and give accurate and reproducible results.

* To adapt the RC DC assay to a microplate format, follow the micro test tube (microfuge tube) assay protocol in the RC DC instruction manual up to the centrifugation step where the supernatant is discarded. The pellet can then be transferred to the microplate, and the microplate assay protocol in the DC protein assay manual can be followed.

In a typical protein assay, a chemical reagent is added to a protein sample, producing a visible result, such as a color change in the sample solution. This color change is quantitated with a spectrophotometer or microplate reader, and compared to a standard curve of known concentrations of protein versus their absorbance after reaction with the reagent. The amount of protein in the unknown sample is determined by interpolation, reading the concentration of protein on the standard curve that corresponds to its absorbance.

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.

Microassay Capability
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.


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DC™ Protein Assay Kit I

Detergent-compatible colorimetric assay kit, includes 250 ml alkaline copper tartrate, 2 L dilute Folin reagent, 5 ml surfactant solution, bovine γ-globulin standard; 450 assays

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DC™ Protein Assay Kit II

Detergent-compatible colorimetric assay kit, includes 250 ml alkaline copper tartrate, 2 L dilute Folin reagent, 5 ml surfactant solution, BSA standard; 450 assays

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Number Description Options
1123 Protein Assay Applications Bibliography Click to download
1069 Colorimetric Protein Assays, Rev D Click to download
1731 Bio-Rad DC Protein Assay Flier, Rev A. Click to download
LIT448 Instruction Manual, DC Protein Assay Click to download
1909 Modification of Bio-Rad DC Protein Assay for Use With Thiols Click to download
1770 Total Cellular Protein Determination Using the DC Protein Assay Click to download
6837 DC™ Protein Assay Quick Guide, Ver A Click to download