Before embarking on any type of protein analysis, particularly when using comparative techniques, it is important to accurately quantify the amount of protein in your samples. Fluorescence-based protein quantification detection methods provide the highest sensitivity which means you use less of your protein samples for quantification and have more sample available for your experiment. For the assays described below, few steps are required and timing is not critical so the assays can be adapted for automated robotic handling in high throughput applications. The fluorescence signal can be detected using a fluorometer or microplate reader.

Related Products

 

Comparison of Solution Assays for Protein Quantification

Assay *Detection Wavelength Sensitivity and Effective Range Mechanism of Action Notes
Quant-iT™ Protein Assay (Q33210)470/570Quasi-linear from 0.5 to 4 µg in a 200 µL assay volume, with a sample volume of 1–20 µLBinds to detergent coating on proteins and hydrophobic regions of proteins; the unbound dye is nonfluorescent•Best for more than 20 samples
•Extremely fast and easy—just add sample to diluted dye and read fluorescence
•High sensitivity
•Little protein-to-protein variation
•Compatible with salts, solvents, 2-mercaptoethanol, amino acids and DNA, but not detergents
Qubit® Protein Assay (Q33211, Q33212)470/570Quasi-linear from 0.5 to 4 µg in a 200 µL assay volume, with a sample volume of 1–20 µLBinds to detergent coating on proteins and hydrophobic regions of proteins; the unbound dye is nonfluorescent•Best for 1 to 20 samples
•Compatible with Qubit® Fluorometer
•Extremely fast and easy—just add sample to diluted dye and read fluorescence
•High sensitivity
•Little protein-to-protein variation
•Compatible with salts, solvents, 2-mercaptoethanol, amino acids and DNA, but not detergents
NanoOrange® Protein Quantification Assay (N6666) 470/57010 ng/mL to 10 µg/mL Binds to detergent coating on proteins and hydrophobic regions of proteins; the unbound dye is nonfluorescent •High sensitivity
•Little protein-to-protein variation
•Rapid assay with a simple procedure
•Compatible with reducing agents, but not detergents
CBQCA Protein Quantification Assay (C6667) 450/550 10 ng/mL to 150 µg/mL Reacts with primary amine groups on proteins in the presence of cyanide or thiols; the unreacted dye is nonfluorescent •High sensitivity
•Sensitivity depends on the number of amines present
•Linear over an extended range of protein concentration
•Compatible with detergents and lipophilic proteins
•Not compatible with buffers containing amines or thiols
EZQ™ Protein Quantification Assay (R33200) 280 and 450/61850 µg/mL to 5 mg/mL, with a sample volume of 1 µLBinds electrostatically to basic amino acids, supplemented by additional hydrophobic interactions •Ideal for determining protein concentration prior to electrophoresis
•Solid-phase format designed for high-throughput analysis
•Little protein-to-protein variation
•Compatible with detergents, reducing agents, urea and tracking dyes
Bradford Assay ref (Coomassie Brilliant Blue) 595 1 µg/mL to 1.5 mg/mL Directly binds specific amino acids and protein tertiary structures; the dye's color changes from brown to blue •High protein-to-protein variation
•Not compatible with detergents
•Rapid assay
•Useful when accuracy is not crucial
BCA Method ref (bicinchoninic acid) 562 0.5 µg/mL to 1.2 mg/mL Cu2+ is reduced to Cu+ in the presence of proteins at high pH; the BCA reagent chelates Cu+ ions, forming purple-colored complexes •Compatible with detergents, chaotropes and organic solvents
•Not compatible with reducing agents
•The sample must be read within 10 minutes
Lowry Assay ref (biuret reagent plus Folin–Ciocalteu reagent) 750 1 µg/mL to 1.5 mg/mL Cu2+ is reduced to Cu+ in the presence of proteins at high pH; the biuret reagent chelates the Cu+ ion, then the Folin–Ciocalteu reagent enhances the blue color •Lengthy procedure with carefully timed steps
•Not compatible with detergents or reducing agents
Fluorescamine ref (F2332, F20261) 390/475 0.3 µg/mL to 13 µg/mL Reacts with primary amine groups on proteins; unbound dye is nonfluorescent •Sensitivity depends on the number of amines present
•Reagent is unstable
•Not compatible with amine-containing buffers
OPA ref (o-phthaldialdehyde) (P2331MP) 340/455 0.2 µg/mL to 25 µg/mL Reacts with primary amine groups on proteins in the presence of 2-mercaptoethanol; unbound dye is nonfluorescent •Sensitivity depends on the number of amines present
•Not compatible with amine-containing buffers
•Low cost
UV absorption ref 280 10 µg/mL to 50 µg/mL or 50 µg/mL to 2 mg/mL Peptide bond absorption; tryptophan and tyrosine absorption •Sensitivity depends on the number of aromatic amino acid residues present
•Nondestructive
•Low cost
* Excitation and emission wavelength maxima or absorption wavelength maximum, in nm.

Solution-Based Protein Quantification Assay Products

Sku Name Size Price Qty
Q33210 Quant-iT™ Protein Assay Kit 1 kit USD 349.00
Q33211 Qubit® Protein Assay Kit 100 assays USD 79.00
Q33212 Qubit® Protein Assay Kit 500 assays USD 237.00
N6666 NanoOrange® Protein Quantitation Kit, 200-2,000 assays 1 kit USD 252.00
C6667 CBQCA Protein Quantitation Kit 1 kit USD 224.00
R33200 EZQ™ Protein Quantitation Kit 2,000 assays USD 335.00
F2332 Fluorescamine, 100 mg 100 mg USD 93.00



For Research Use Only.  Not intended for any animal or human therapeutic or diagnostic use.