Qubit Protein Assay Kit
The Qubit Protein Assay Kit is designed specifically for use with any Qubit fluorometer. While using between 1 and 20 µL of sample, this assay can quantify samples ranging from 12.5 µg/mL to 5 mg/mL with low protein-to-protein variation.

The Qubit Protein Assay Kit is highly selective for proteins and is also highly accurate in the presence of reducing reagents, but not in the presence of large amounts of detergent. Common contaminants, such as reducing reagents (e.g., DTT, β-mercaptoethanol), salts, free nucleotides, amino acids, solvents, and DNA (but not detergents), are well tolerated in the assay. Slight protocol modifications are required for other contaminants.

The kit provides concentrated assay reagent, dilution buffer, and pre-diluted BSA standards. Simply dilute the reagent using the buffer provided, add your sample (any volume between 1 µL and 20 µL is acceptable), and read the concentration.

Which product should you choose for fluorometric protein quantitation?
• 1–20 samples: use this Qubit Protein Assay Kit with the Qubit Fluorometer
• 20–2000 samples: use the Quant-iT Protein Assay Kit with a microplate reader

Qubit Protein BR Assay Kit
The Qubit Protein BR Assay Kit provides a quick, easy, and reliable method for determining the protein concentration of purified proteins, lysates, serum, plasma, or complex protein mixtures using a Qubit 4 Fluorometer. This protein kit can deliver accurate protein quantitation across a broad range (0.1–20 mg/mL), enabling most samples to be used neat (undiluted) and eliminating the guess work and dilution steps that accompany traditional protein quantitation methods. The assay is compatible with many common contaminants, such as detergents, reducing reagents (e.g., DTT, β-mercaptoethanol), salts, and nucleic acids.

Key features of the Qubit Protein BR Assay Kit include:
• Broad dynamic range—0.1 to 20 mg/mL, measure samples without dilution
• Two-point standard curve—eliminate time-consuming standard preparation
• Automatic concentration determination—receive protein concentration instantaneously; no need for offline calculations
• Compatible—accurate in the presence of reducing reagents, detergents, and other common buffer components

The Qubit Protein BR Assay Kit comes with two calibration standards, Protein BR Assay Buffer, and Protein BR Assay Reagent. Simply add 150–160 µL of Protein BR Assay Buffer to 10 or 20 µL of your sample, followed by 30 µL of Protein BR Assay Reagent. Incubate for 10 minutes at room temperature. Then insert the sample into a Qubit 4 instrument and read the concentration.

Notes
• The Qubit Protein Assay Kit can be used with Qubit 1.0, Qubit 2.0, Qubit 3, and Qubit 4 fluorometers
• The Qubit Protein BR Assay Kit is a fluorescence-based assay intended for use only with the Qubit 4 Fluorometer
• 500 µL thin-walled clear PCR tubes (Cat. No. Q32856) are required but not included in the Protein Assay and BR Assay Kits