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Qubit Protein Assays
Rapid, accurate protein quantitation
The Qubit Protein Assays are protein quantitation assays optimized to work on your Qubit device. These assays provide low protein variability, rapid quantitation, and high sensitivity. Learn more about each of the available assays below.
Qubit protein assays
| Qubit Protein BR Assay | Qubit Protein Assay | |
|---|---|---|
 |  | |
| Appropriate for | A broad range of protein concentrations and types; samples containing detergents | Testing dilute samples, <100 µg/mL |
| Compatible platform | Qubit 4 | Qubit Flex, Qubit 4* |
| Features | Simple, rapid assay with 2-point standard curve | Simple, rapid assay with 3-point standard curve |
| Sample volume required | 10 or 20 µl | 1–20 µL |
| Compatibility | Detergents, reducing agents (e.g., TCEP, DTT) | Reducing agents (e.g., TCEP, DTT) |
| Incompatibility | Glycine | Detergents (e.g., SDS, Tween 20, Triton X-100) |
| Initial sample range | 100 µg/ml to 20 mg/ml | 12.5 µg/mL to 5 mg/mL |
| Quantitation range | 1–400 µg | 0.25–5 µg |
| Cat. No. | A50668 (100 assays) A50669 (500 assays) | Q33211 (100 assays) Q33212 (500 assays) |
*The Qubit Protein Assay is also supported on older Qubit models–Qubit 2 and Qubit 3
Simple rapid quantitation
Qubit Protein Assays are easy to perform and only require a 10–15 minute room temperature incubation, eliminating the need to wait for long incubation periods or expose samples to elevated temperatures. The assays are easy to set up with just two or three standards to prepare, unlike traditional assays which typically require a 7-point standard curve for quantitation determination.
Qubit Protein BR Assay workflow
Click image to enlarge
Qubit Protein Assay workflow
Click image to enlarge
Accurate protein quantitation
Qubit Protein Assays provide accurate protein quantitation with low protein to protein variability as compared to traditional assays such as the Bradford assay. Proteins are diverse in their composition and structure. Differences in amino acid sequence, isoelectric point (pI), secondary structure, and side chains or prosthetic groups can result in variation in the quantitated amount.
To demonstrate the accuracy and low protein-to-protein variability of the Qubit Protein BR Assay, several different cell lysates were generated, and total protein concentration was determined with the Qubit Protein BR Assay and a Bradford Protein assay. The calculated concentrations were used to load 10 µg of each lysate onto a protein gel. Accuracy of total protein load was evaluated using No-Stain Protein Labeling Reagent. The load variation produced by Qubit Protein BR Assay was relatively low, with a CV of 11%, whereas the load variation produced by the Bradford assay was 2.5 times higher, with a CV of 28%.
Click image to enlarge
An accurate protein assay for use in downstream applications. When loading an electrophoresis gel for western blot analysis to study protein expression, accurate protein loading is essential. Qubit Protein BR Assay and Bradford Protein Assay were used to determine a 10 µg protein load for 5 different cell lysates. No-Stain Protein Label Reagent was used to estimate the total protein lane loads. The Qubit Protein BR Assay accurately determined the protein concentration of the lysates as demonstrated by a CV of 11% between loads, whereas the Bradford assay exhibited higher variability with a CV of 28%.
Skip the dilutions with a wide dynamic range assay
The Qubit Protein Assays provide a large dynamic range in comparison to standard assays. This response curve allows accurate determination of unknown protein concentration at much higher protein concentrations than other standard assays (e.g., Bradford assays). The Qubit Protein BR Assay can be used to detect protein concentrations between 100 µg/mL to 20,000 µg/mL, enabling most samples to be used neat (undiluted), eliminating the guess work and dilution steps that accompany traditional protein quantitation methods.
Click image to enlarge
Click image to enlarge
Qubit Protein Assays provide a much larger dynamic range than standard protein quantitation assays such as Bradford assays. Qubit Protein Assay is capable of accurate quantitation down to 12.5 µg/mL and Qubit Protein BR Assay has a quantitation range up to 20,000 µg/mL.
Get quantitation data faster
The user-friendly Qubit Fluorometer delivers results using quick, simple assay procedures. The large, color touch screen allows you to easily navigate through the various options. Calculations and settings are automatically performed by the instrument—so no need for offline data calculation. The Qubit 4 Fluorometer will save the data for up to 1,000 samples, and you can transfer data using Wi-Fi, a USB drive, or direct connection with a USB cable.
Protein BR Assay user interface on the Qubit 4 Fluorometer.
Assay compatibility with common buffer components
| Qubit Protein BR Assay | Qubit Protein Assay | |
|---|---|---|
| Contaminant | Compatible concentration in sample | Compatible concentration in sample |
| β-Mercaptoethanol | 1 mM | 10 mM |
| Acetonitrile | 20% | |
| Ammonium sulfate | 200 mM | 50 mM* |
| Bicine | 100 mM | |
| Borate (50 mM pH 8.5) | Neat | |
| B-PER reagent | Neat | |
| CHAPS | 5% | |
| Carbonate-bicarbonate | Neat | |
| DTT | 5 mM | 10 mM* |
| DMSO | 10% | |
| EDTA | 50 mM | 10 mM |
| Glucose | 1 M | |
| Glycerol | 10% | 10%* |
| Guanidine-HCl | 4 M | |
| Imidazole | 200 mM | 12.5 mM |
| I-PER | Neat | |
| Mem-PER | Neat | |
| MES | 125 mM | |
| MOPS | 100 mM | |
| M-PER | Neat | |
| Sodium acetate | 100 mM | |
| Sodium azide | 10 mM | |
| Sodium chloride | 5 M | 200 mM* |
| NE-PER (CER) | Neat | |
| NE-PER (NER) | Neat | |
| NP-40 | 5% | Ø |
| Phosphate-buffer saline (PBS), pH 7.4 | Neat | 10 mM KPO4, 150 mM NaCl* |
| Potassium phosphate, pH 7.4 | 5 mM | |
| PMSF | 1 mM | |
| RIPA | Neat | |
| SDS | 5% | 0.1%* |
| Sucrose | 20% | 500 mM |
| T-PER | Neat | |
| Tricine | 50 mM | |
| Tris-buffer saline (TBS) | Neat | |
| Tris-glycine, pH 8.0*** | Ø | |
| Tris-glycine SDS, pH 8.3 | Ø | |
| Tris-HCl | 500 mM | |
| Tris-HEPES SDS, pH 8.0 | Neat | |
| Triton X-100 | 5% | Ø |
| Tween 20 | 3% | Ø |
| Urea | 3 M | |
| Y-Per | Ø | |
| GPCR Extraction & Stabilization Reagent | 1:2 | |
| Cell Surface Protein Isolation Kit | Neat |
*An acceptable result, but with some distortion of the standard curve. For best results, add the same amount of contaminant to the standard samples.
The Qubit Protein BR Assay and Qubit Protein Assay were performed according to instructions with samples of 1,000 µg/mL of BSA containing commonly used buffers and contaminants. Assays were performed in triplicate, and RFU values were compared to that of BSA in 0.9% NaCl, 0.05% NaN3. The assay was considered compatible with the tested substance at the indicated concentration if the error in protein concentration estimation caused by the presence of the substance was less than 10%. Concentrations listed refer to the actual concentration in the protein sample. Ø denotes compounds that were not compatible at the lowest concentration tested. Blank rows denote the compounds were not tested with that particular assay.
Buffer formulations used in compatibility testing
| Buffer | Formulation |
|---|---|
| Sodium carbonate-bicarbonate, pH 9.4 | 0.2 M sodium carbonate-bicarbonate, pH 9.4 |
| Phosphate-buffered saline (PBS) | 100 mM sodium phosphate, 150 mM NaCl, pH 7.2 |
| RIPA buffer | 25 mM Tris, 150 mM NaCl, 1% DOC, 1% NP-40, 0.1% SDS, pH 7.6 |
| Tris-buffered saline (TBS) | 25 mM Tris, 150 mM NaCl, pH 7.4 |
| Tris-glycine, pH 8.0 | 25 mM Tris, 192 mM glycine, pH 8.0 |
| Tris-glycine-SDS, pH 8.3 | 25 mM Tris, 192 mM glycine, 0.1% SDS, pH 8.3 |
| Tris-HEPES-SDS | 100 mM Tris, 100 mM HEPES, 3 mM SDS |
Product manuals
Application notes
Qubit protein assays
| Qubit Protein BR Assay | Qubit Protein Assay | |
|---|---|---|
| | | |
| Appropriate for | A broad range of protein concentrations and types; samples containing detergents | Testing dilute samples, <100 µg/mL |
| Compatible platform | Qubit 4 | Qubit Flex, Qubit 4* |
| Features | Simple, rapid assay with 2-point standard curve | Simple, rapid assay with 3-point standard curve |
| Sample volume required | 10 or 20 µl | 1–20 µL |
| Compatibility | Detergents, reducing agents (e.g., TCEP, DTT) | Reducing agents (e.g., TCEP, DTT) |
| Incompatibility | Glycine | Detergents (e.g., SDS, Tween 20, Triton X-100) |
| Initial sample range | 100 µg/ml to 20 mg/ml | 12.5 µg/mL to 5 mg/mL |
| Quantitation range | 1–400 µg | 0.25–5 µg |
| Cat. No. | A50668 (100 assays) A50669 (500 assays) | Q33211 (100 assays) Q33212 (500 assays) |
*The Qubit Protein Assay is also supported on older Qubit models–Qubit 2 and Qubit 3
Simple rapid quantitation
Qubit Protein Assays are easy to perform and only require a 10–15 minute room temperature incubation, eliminating the need to wait for long incubation periods or expose samples to elevated temperatures. The assays are easy to set up with just two or three standards to prepare, unlike traditional assays which typically require a 7-point standard curve for quantitation determination.
Qubit Protein BR Assay workflow
Click image to enlarge
Qubit Protein Assay workflow
Click image to enlarge
Accurate protein quantitation
Qubit Protein Assays provide accurate protein quantitation with low protein to protein variability as compared to traditional assays such as the Bradford assay. Proteins are diverse in their composition and structure. Differences in amino acid sequence, isoelectric point (pI), secondary structure, and side chains or prosthetic groups can result in variation in the quantitated amount.
To demonstrate the accuracy and low protein-to-protein variability of the Qubit Protein BR Assay, several different cell lysates were generated, and total protein concentration was determined with the Qubit Protein BR Assay and a Bradford Protein assay. The calculated concentrations were used to load 10 µg of each lysate onto a protein gel. Accuracy of total protein load was evaluated using No-Stain Protein Labeling Reagent. The load variation produced by Qubit Protein BR Assay was relatively low, with a CV of 11%, whereas the load variation produced by the Bradford assay was 2.5 times higher, with a CV of 28%.
Click image to enlarge
An accurate protein assay for use in downstream applications. When loading an electrophoresis gel for western blot analysis to study protein expression, accurate protein loading is essential. Qubit Protein BR Assay and Bradford Protein Assay were used to determine a 10 µg protein load for 5 different cell lysates. No-Stain Protein Label Reagent was used to estimate the total protein lane loads. The Qubit Protein BR Assay accurately determined the protein concentration of the lysates as demonstrated by a CV of 11% between loads, whereas the Bradford assay exhibited higher variability with a CV of 28%.
Skip the dilutions with a wide dynamic range assay
The Qubit Protein Assays provide a large dynamic range in comparison to standard assays. This response curve allows accurate determination of unknown protein concentration at much higher protein concentrations than other standard assays (e.g., Bradford assays). The Qubit Protein BR Assay can be used to detect protein concentrations between 100 µg/mL to 20,000 µg/mL, enabling most samples to be used neat (undiluted), eliminating the guess work and dilution steps that accompany traditional protein quantitation methods.
Click image to enlarge
Click image to enlarge
Qubit Protein Assays provide a much larger dynamic range than standard protein quantitation assays such as Bradford assays. Qubit Protein Assay is capable of accurate quantitation down to 12.5 µg/mL and Qubit Protein BR Assay has a quantitation range up to 20,000 µg/mL.
Get quantitation data faster
The user-friendly Qubit Fluorometer delivers results using quick, simple assay procedures. The large, color touch screen allows you to easily navigate through the various options. Calculations and settings are automatically performed by the instrument—so no need for offline data calculation. The Qubit 4 Fluorometer will save the data for up to 1,000 samples, and you can transfer data using Wi-Fi, a USB drive, or direct connection with a USB cable.
Protein BR Assay user interface on the Qubit 4 Fluorometer.
Assay compatibility with common buffer components
| Qubit Protein BR Assay | Qubit Protein Assay | |
|---|---|---|
| Contaminant | Compatible concentration in sample | Compatible concentration in sample |
| β-Mercaptoethanol | 1 mM | 10 mM |
| Acetonitrile | 20% | |
| Ammonium sulfate | 200 mM | 50 mM* |
| Bicine | 100 mM | |
| Borate (50 mM pH 8.5) | Neat | |
| B-PER reagent | Neat | |
| CHAPS | 5% | |
| Carbonate-bicarbonate | Neat | |
| DTT | 5 mM | 10 mM* |
| DMSO | 10% | |
| EDTA | 50 mM | 10 mM |
| Glucose | 1 M | |
| Glycerol | 10% | 10%* |
| Guanidine-HCl | 4 M | |
| Imidazole | 200 mM | 12.5 mM |
| I-PER | Neat | |
| Mem-PER | Neat | |
| MES | 125 mM | |
| MOPS | 100 mM | |
| M-PER | Neat | |
| Sodium acetate | 100 mM | |
| Sodium azide | 10 mM | |
| Sodium chloride | 5 M | 200 mM* |
| NE-PER (CER) | Neat | |
| NE-PER (NER) | Neat | |
| NP-40 | 5% | Ø |
| Phosphate-buffer saline (PBS), pH 7.4 | Neat | 10 mM KPO4, 150 mM NaCl* |
| Potassium phosphate, pH 7.4 | 5 mM | |
| PMSF | 1 mM | |
| RIPA | Neat | |
| SDS | 5% | 0.1%* |
| Sucrose | 20% | 500 mM |
| T-PER | Neat | |
| Tricine | 50 mM | |
| Tris-buffer saline (TBS) | Neat | |
| Tris-glycine, pH 8.0*** | Ø | |
| Tris-glycine SDS, pH 8.3 | Ø | |
| Tris-HCl | 500 mM | |
| Tris-HEPES SDS, pH 8.0 | Neat | |
| Triton X-100 | 5% | Ø |
| Tween 20 | 3% | Ø |
| Urea | 3 M | |
| Y-Per | Ø | |
| GPCR Extraction & Stabilization Reagent | 1:2 | |
| Cell Surface Protein Isolation Kit | Neat |
*An acceptable result, but with some distortion of the standard curve. For best results, add the same amount of contaminant to the standard samples.
The Qubit Protein BR Assay and Qubit Protein Assay were performed according to instructions with samples of 1,000 µg/mL of BSA containing commonly used buffers and contaminants. Assays were performed in triplicate, and RFU values were compared to that of BSA in 0.9% NaCl, 0.05% NaN3. The assay was considered compatible with the tested substance at the indicated concentration if the error in protein concentration estimation caused by the presence of the substance was less than 10%. Concentrations listed refer to the actual concentration in the protein sample. Ø denotes compounds that were not compatible at the lowest concentration tested. Blank rows denote the compounds were not tested with that particular assay.
Buffer formulations used in compatibility testing
| Buffer | Formulation |
|---|---|
| Sodium carbonate-bicarbonate, pH 9.4 | 0.2 M sodium carbonate-bicarbonate, pH 9.4 |
| Phosphate-buffered saline (PBS) | 100 mM sodium phosphate, 150 mM NaCl, pH 7.2 |
| RIPA buffer | 25 mM Tris, 150 mM NaCl, 1% DOC, 1% NP-40, 0.1% SDS, pH 7.6 |
| Tris-buffered saline (TBS) | 25 mM Tris, 150 mM NaCl, pH 7.4 |
| Tris-glycine, pH 8.0 | 25 mM Tris, 192 mM glycine, pH 8.0 |
| Tris-glycine-SDS, pH 8.3 | 25 mM Tris, 192 mM glycine, 0.1% SDS, pH 8.3 |
| Tris-HEPES-SDS | 100 mM Tris, 100 mM HEPES, 3 mM SDS |
Product manuals
Application notes
仅供研究使用，不可应用于诊断程序。