Shop All Protein Quantitation Assay Kits, Reagents & Standards

Easy-Titer™ Human IgM Assay Kit (Thermo Scientific™)

The Thermo Scientific Easy-Titer Human IgM Assay Kit includes antibody-sensitized microspheres to measure the specific concentration of antibodies by an easy and rapid microagglutination technique using standard microplates and UV-Vis plate reader (spectrophotometer). This kit is specific for human IgM and, unlike total protein assays, can specifically measure the concentration of target antibody in samples (e.g., serum, plasma, culture supernatant) that contain other proteins. It is sensitive, requiring very small sample volumes. Antibody concentration is determined from the assay response (absorbance) by comparison to a standard curve prepared using dilutions of a known antibody sample (sold separately).

General features of Easy-Titer Antibody Assay Kits:

Antibody-based specificity—measure concentration of target antibody in a sample, not just total protein; no need to purify antibody to assess its concentration
Faster and easier than ELISA—three-component, homogenous assay; 10 minutes total incubation time
No special equipment needed—uses standard vortex mixer, pipetter, 96-well microplate, plate shaker and reader (measure absorbance at 340nm or 400nm)
Sensitive—assay range (standard curve) 8 to 500 ng/mL; use sample at 15 to 300 ng/mL for optimal results
Reproducible—coefficient of variation < 5%; error depends on dilution and pipetting technique
Antibody standards sold separately—see product list for suggested products; use any antibody standard with proper target identity and known concentration (greater than 10 µg/mL)
Kits for five popular targets—choose a kit specific for a particular species and class of immunoglobulin; no cross-reaction with other species and classes of the target antibody

Easy-Titer Assay Kits detect and measure specific target antibodies using agglutination of microspheres that are coated ("sensitized") with the specific anti-IgG or IgM polyclonal antibodies. In the appropriate aqueous buffer (supplied in kit), the monodispersed antibody-coated microspheres (> 1 µM diameter) have highest absorptivity (λ-max) to incident light having a wavelength (340nm) that is equal to approximately half their diameter. When sample is added, two or more microspheres bind to each antibody target via their coated specific polyclonal antibodies, and this agglutination into effectively larger apparent spheres results in proportional decrease in absorptivity (lower absorbance).

Typical microagglutination assays depend on a change in light-scattering and corresponding change in transmittance, to which absorbance is inversely related. Easy-Titer Assay Kits use a special dilution buffer whose refractive index eliminates the effect of light-scattering on the monodispersed microspheres for the measurement wavelength used. Because of this, the final 10- to 20-fold dilution of the sample for use in the assay must be done using the Dilution Buffer supplied in the kit.

Easy-Titer Antibody Assays are faster and easier than ELISA:
• Prepare standards (5 to 500 ng/mL) by diluting purified antibody in Kit Dilution Buffer.
• Prepare samples by diluting in Dilution Buffer to within assay range (8 to 500 ng/mL).
• Vortex vial of microsphere beads to create homogeneous suspension.
• Pipette 20 µL of bead suspension and 20 µL of each sample and standard into 96-well microplate wells.
• Incubate microplate for 5 minutes with vigorous mixing.
• Add 100 µL of Kit Blocking Reagent.
• Incubate microplate for 5 minutes with vigorous mixing.
• Measure absorbance on standard plate reader (340nm or 405nm).
• Plot standard curve and interpolate samples to determine concentration.

Related Products
Easy-Titer™ Mouse IgG Assay Kit
Easy-Titer™ Rabbit IgG Assay Kit
Easy-Titer™ Human IgG (H+L) Assay Kit
Easy-Titer™ Human IgG (gamma chain) Assay Kit

Micro BCA™ Protein Assay Kit (Thermo Scientific™)

The Pierce Micro BCA Protein Assay Kit is a three-component version of our BCA reagents, optimized to measure total protein concentration of dilute protein solutions (0.5 to 20 µg/mL).

Compare all available BCA protein assays ›

Features of the Micro BCA Protein Assay Kit include:
Sensitivity—accurately detect down to 0.5 µg/mL (2 µg/mL in microplate format)
Working range—linear working range for BSA of 0.5 to 20 µg/mL
Colorimetric—measure with a standard spectrophotometer or plate reader at 562 nm
Compatibility—unaffected by typical concentrations of most ionic and non-ionic detergents
Stability—kit is stable at room temperature; prepared working reagent stable for up to 24 hours

The Micro BCA Protein Assay Kit is a specialized version of the popular Pierce BCA Protein Assay for determining the protein concentration of dilute samples. Mixing together the three Micro BCA reagents results in a working solution that is sufficiently concentrated to measure protein when mixed with an equal volume of sample. The result is an assay for accurately measuring 0.5 to 20 µg/mL protein solutions. The assay is exceptionally linear and exhibits very low levels of protein-to-protein variability.

Related products
Micro BCA Reagent A (MA)
Micro BCA Reagent B (MB)
Micro BCA Reagent C (MC)
Ampule Breakers

Pierce™ Coomassie Plus (Bradford) Assay Kit (Thermo Scientific™)

The Pierce Coomassie Plus (Bradford) Protein Assay is a ready-to-use, reducing agent-compatible, improved Bradford assay reagent to quickly measure total protein concentration compared to a protein standard. The Pierce Coomassie Plus Assay Reagent provides increased linearity and half the protein-to-protein variability of other commercial Bradford assay formulations.

Compare all available Bradford assays ›

Features of the Coomassie Plus Protein Assay include:
Colorimetric—measure with a standard spectrophotometer or plate reader at 595 nm
Easy to use—single reagent; no working reagent preparation required
Fast—almost immediate color development; add, mix, and read results
Assay range—detects protein concentration in the range 1 to 1500 µg/mL
Better—improved linearity and response uniformity compared to traditional Bradford formulations
Flexible—microplate and cuvette protocols provided and adaptable to several target working ranges

The assay is performed at room temperature. Simply add the sample to the tube containing reagent and the resultant blue color is measured at 595 nm following a short room-temperature incubation. The protein assay is compatible with most salts, solvents, buffers, thiols, reducing substances, and metal-chelating agents encountered in protein samples. The assay can be performed in either test tube or microplate format.

How the Coomassie Plus (Bradford) Assay detects protein
Use of Coomassie G-250 dye in a colorimetric reagent for the detection and quantitation of total protein was first described by Dr. Marion Bradford in 1976. In the acidic environment of the reagent, protein binds to the Coomassie dye. This results in a spectral shift from the reddish/brown form of the dye (absorbance maximum at 465 nm) to the blue form of the dye (absorbance maximum at 610 nm). The difference between the two forms of the dye is greatest at 595 nm, so that is the optimal wavelength to measure the blue color from the Coomassie dye-protein complex. If desired, the blue color can be measured at any wavelength between 575 nm and 615 nm. At the two extremes (575 nm and 615 nm) there is a loss of about 10% in the measured amount of color (absorbance) compared to that obtained at 595 nm.

Development of color in Coomassie dye-based (Bradford) protein assays has been associated with the presence of certain basic amino acids (primarily arginine, lysine, and histidine) in the protein. Van der Waals forces and hydrophobic interactions also participate in the binding of the dye by protein. The number of Coomassie dye ligands bound to each protein molecule is approximately proportional to the number of positive charges found on the protein. Free amino acids, peptides, and low molecular weight proteins do not produce color with Coomassie dye reagents. In general, the mass of a peptide or protein must be at least 3,000 daltons to be assayed with this reagent.

Related products
Pierce Coomassie Plus (Bradford) Assay Reagent
Pierce Detergent Compatible Bradford Assay Kit
Ampule Breakers

Pierce™ Modified Lowry Protein Assay Kit (Thermo Scientific™)

The Pierce Modified Lowry Protein Assay is a stable form of a traditional, two-component, folin phenol- and copper-based reagent system to measure total protein concentration compared to a protein standard.

See all available protein assays ›

Features of Modified Lowry Protein Assay include:
Popular method—widely cited in protein research literature
Colorimetric—measure with a standard spectrophotometer or plate reader at 750 nm
Stability—uses a modified cupric sulfate-tartrate reagent that is stable at room temperature
Assay range—exhibits good linearity in the range 1 to 1500 µg/mL (tested with BSA protein)

The Modified Lowry Protein Assay Kit combines a stabilized formulation of the original Lowry reagents and the essential Folin-Ciocalteu Phenol reagent in a complete kit for accurately determining protein concentration in a variety of samples types. Although newer protein assay methods provide greater speed and convenience, the Lowry method remains a popular, accurate, and useful option for many applications.

Pierce™ 660nm Protein Assay Kit (Thermo Scientific™)

The Pierce 660-nm Protein Assay is a ready-to-use, detergent- and reducing agent-compatible assay reagent to quickly measure total protein concentration compared to a protein standard. The assay is more linear than Coomassie-based Bradford assays and compatible with higher concentrations of most detergents, reducing agents, and other commonly used reagents.

See all available protein assays ›

Features of the 660-nm Protein Assay Kit:
Compatibility—works with a greater range of detergents and reducing agents than other dye-based assays
Ready-to-use—single reagent with a simple mix-and-read protocol; no working reagent to prepare
Linearity—produces standard curves that are more linear than with the Bradford assay method
Assay format—assay may be performed in test tubes or microplates
Sample volume—requires only 10 µL for microplate or 100 µL for the test tube procedures
Storage—room temperature storage

The accessory Ionic Detergent Compatibility Reagent (IDCR) provides for even broader detergent compatibility, making this one of the only protein assays that is suitable for samples containing Laemmli SDS sample buffer with bromophenol blue. Although the Pierce 660-nm Protein Assay produces a higher level of protein-to-protein variation (37%) than other assays, such as the BCA Protein Assay, the simpler single-reagent format and broader substance compatibility make the Pierce 660-nm assay more convenient for many routine applications. The Pierce 660-nm Protein Assay can be performed in either a test tube or microplate format.

How the Pierce 660-nm Assay detects protein
The Pierce 660-nm Protein Assay is based on the binding of a proprietary dye-metal complex to protein in acidic conditions that causes a shift in the dye's absorption maximum, which is measured at 660 nm. The dye-metal complex is reddish-brown and changes to green upon protein binding. The color change is produced by deprotonation of the dye at low pH facilitated by interactions with positively charged amino acid groups in proteins. Therefore, the dye interacts mainly with basic residues in proteins, such as histidine, arginine, and lysine and to a lesser extent tyrosine, tryptophan, and phenylalanine.

The color produced in the assay is stable and increases in proportion to a broad range of increasing protein concentrations, even in the presence of detergents and reducing agents that would be incompatible with Bradford and BCA protein assays.

Related products
Pierce 660-nm Protein Assay Reagent
Ionic Detergent Compatibility Reagent for Pierce 660-nm Protein Assay Reagent

Easy-Titer™ Rabbit IgG Assay Kit (Thermo Scientific™)

The Thermo Scientific Easy-Titer Rabbit IgG Assay Kit includes antibody-sensitized microspheres to measure the specific concentration of antibodies by an easy and rapid microagglutination technique using standard microplates and UV-Vis plate reader (spectrophotometer). This kit is specific for rabbit IgG and, unlike total protein assays, can specifically measure the concentration of target antibody in samples (e.g., serum, plasma, culture supernatant) that contain other proteins. It is sensitive, requiring very small sample volumes. Antibody concentration is determined from the assay response (absorbance) by comparison to a standard curve prepared using dilutions of a known antibody sample (sold separately).

General features of Easy-Titer Antibody Assay Kits:

Antibody-based specificity—measure concentration of target antibody in a sample, not just total protein; no need to purify antibody to assess its concentration
Faster and easier than ELISA—three-component, homogenous assay; 10 minutes total incubation time
No special equipment needed—uses standard vortex mixer, pipetter, 96-well microplate, plate shaker and reader (measure absorbance at 340nm or 400nm)
Sensitive—assay range (standard curve) 8 to 500 ng/mL; use sample at 15 to 300 ng/mL for optimal results
Reproducible—coefficient of variation < 5%; error depends on dilution and pipetting technique
Antibody standards sold separately—see product list for suggested products; use any antibody standard with proper target identity and known concentration (greater than 10 µg/mL)
Kits for five popular targets—choose a kit specific for a particular species and class of immunoglobulin; no cross-reaction with other species and classes of the target antibody

Easy-Titer Assay Kits detect and measure specific target antibodies using agglutination of microspheres that are coated ("sensitized") with the specific anti-IgG or IgM polyclonal antibodies. In the appropriate aqueous buffer (supplied in kit), the monodispersed antibody-coated microspheres (> 1 µM diameter) have highest absorptivity (λ-max) to incident light having a wavelength (340nm) that is equal to approximately half their diameter. When sample is added, two or more microspheres bind to each antibody target via their coated specific polyclonal antibodies, and this agglutination into effectively larger apparent spheres results in proportional decrease in absorptivity (lower absorbance).

Typical microagglutination assays depend on a change in light-scattering and corresponding change in transmittance, to which absorbance is inversely related. Easy-Titer Assay Kits use a special dilution buffer whose refractive index eliminates the effect of light-scattering on the monodispersed microspheres for the measurement wavelength used. Because of this, the final 10- to 20-fold dilution of the sample for use in the assay must be done using the Dilution Buffer supplied in the kit.

Easy-Titer Antibody Assays are faster and easier than ELISA:
• Prepare standards (5 to 500 ng/mL) by diluting purified antibody in Kit Dilution Buffer.
• Prepare samples by diluting in Dilution Buffer to within assay range (8 to 500 ng/mL).
• Vortex vial of microsphere beads to create homogeneous suspension.
• Pipette 20 µL of bead suspension and 20 µL of each sample and standard into 96-well microplate wells.
• Incubate microplate for 5 minutes with vigorous mixing.
• Add 100 µL of Kit Blocking Reagent.
• Incubate microplate for 5 minutes with vigorous mixing.
• Measure absorbance on standard plate reader (340nm or 405nm).
• Plot standard curve and interpolate samples to determine concentration.

Related Products
Easy-Titer™ Mouse IgG Assay Kit
Easy-Titer™ Human IgG (H+L) Assay Kit
Easy-Titer™ Human IgG (gamma chain) Assay Kit
Easy-Titer™ Human IgM Assay Kit

Easy-Titer™ Mouse IgG Assay Kit (Thermo Scientific™)

The Thermo Scientific Easy-Titer Mouse IgG Assay Kit includes antibody-sensitized microspheres to measure the specific concentration of antibodies by an easy and rapid microagglutination technique using standard microplates and UV-Vis plate reader (spectrophotometer). This kit is specific for mouse IgG and, unlike total protein assays, can specifically measure the concentration of target antibody in samples (e.g., serum, plasma, culture supernatant) that contain other proteins. It is sensitive, requiring very small sample volumes. Antibody concentration is determined from the assay response (absorbance) by comparison to a standard curve prepared using dilutions of a known antibody sample (sold separately).

General features of Easy-Titer Antibody Assay Kits:

Antibody-based specificity—measure concentration of target antibody in a sample, not just total protein; no need to purify antibody to assess its concentration
Faster and easier than ELISA—three-component, homogenous assay; 10 minutes total incubation time
No special equipment needed—uses standard vortex mixer, pipetter, 96-well microplate, plate shaker and reader (measure absorbance at 340nm or 400nm)
Sensitive—assay range (standard curve) 8 to 500 ng/mL; use sample at 15 to 300 ng/mL for optimal results
Reproducible—coefficient of variation < 5%; error depends on dilution and pipetting technique
Antibody standards sold separately—see product list for suggested products; use any antibody standard with proper target identity and known concentration (greater than 10 µg/mL)
Kits for five popular targets—choose a kit specific for a particular species and class of immunoglobulin; no cross-reaction with other species and classes of the target antibody

Easy-Titer Assay Kits detect and measure specific target antibodies using agglutination of microspheres that are coated ("sensitized") with the specific anti-IgG or IgM polyclonal antibodies. In the appropriate aqueous buffer (supplied in kit), the monodispersed antibody-coated microspheres (> 1 µM diameter) have highest absorptivity (λ-max) to incident light having a wavelength (340nm) that is equal to approximately half their diameter. When sample is added, two or more microspheres bind to each antibody target via their coated specific polyclonal antibodies, and this agglutination into effectively larger apparent spheres results in proportional decrease in absorptivity (lower absorbance).

Typical microagglutination assays depend on a change in light-scattering and corresponding change in transmittance, to which absorbance is inversely related. Easy-Titer Assay Kits use a special dilution buffer whose refractive index eliminates the effect of light-scattering on the monodispersed microspheres for the measurement wavelength used. Because of this, the final 10- to 20-fold dilution of the sample for use in the assay must be done using the Dilution Buffer supplied in the kit.

Easy-Titer Antibody Assays are faster and easier than ELISA:
• Prepare standards (5 to 500 ng/mL) by diluting purified antibody in Kit Dilution Buffer.
• Prepare samples by diluting in Dilution Buffer to within assay range (8 to 500 ng/mL).
• Vortex vial of microsphere beads to create homogeneous suspension.
• Pipette 20 µL of bead suspension and 20 µL of each sample and standard into 96-well microplate wells.
• Incubate microplate for 5 minutes with vigorous mixing.
• Add 100 µL of Kit Blocking Reagent.
• Incubate microplate for 5 minutes with vigorous mixing.
• Measure absorbance on standard plate reader (340nm or 405nm).
• Plot standard curve and interpolate samples to determine concentration.

Related Products
Easy-Titer™ Rabbit IgG Assay Kit
Easy-Titer™ Human IgG (H+L) Assay Kit
Easy-Titer™ Human IgG (gamma chain) Assay Kit
Easy-Titer™ Human IgM Assay Kit

Compat-Able™ Coomassie Plus Protein Assay Kit (Thermo Scientific™)

The Thermo Scientific Compat-Able Coomassie Plus Protein Assay Kit eliminates interfering substances from protein assay samples to make them compatible with BCA and Bradford assays.

The Compat-Able Reagents remove salts, detergents, reducing agents and other substances from protein samples to eliminate interference with protein assays. The protocol selectively precipitates all of the protein, thereby allowing the non-protein components to be easily decanted and removed. The purified, precipitated protein is redissolved in water, making it ready for accurate determination of the protein concentration by standard protein assay methods. The procedure is accomplished in less than 10 minutes with just a few simple steps. The Compat-Able Preparation Set is available individually or conveniently bundled with either the Thermo Scientific Pierce BCA Protein Assay Kit or the Thermo Scientific Pierce Coomassie Plus Protein Assay Kit.

Features of the Compat-Able Protein Assay Preparation Reagent Kit:

Eliminate incompatibilities—removes nearly any substance that interferes with colorimetric protein assays: salts, detergents, denaturants, reducing agents, and even IEF sample buffer
Simple and fast—prepare samples in less than 10 minutes with four simple steps
Convenient—reagent set is easier to use than homemade TCA or acetone precipitation reagents, thereby producing more consistent results
Scalable—microcentrifuge method is easily scaled to larger centrifuge tube volumes for special needs
Validated—tested and offered together with BCA and Coomassie Plus Protein Assay Kits; protocol integrates control and normalization procedures

Related Products
Compat-Able™ Protein Assay Preparation Reagent Kit
Compat-Able™ BCA Protein Assay Kit
Pierce™ Detergent Compatible Bradford Assay Kit

ProteinSEQ™ Protein A Core Kit (Applied Biosystems™)

The ProteinSEQ™ Protein A Core Kit is a partial kit that enables users to customize their ProteinSEQ protein measurements for leeched Protein A, or any other ligand used in their purification columns. It contains the buffers and reagents, but not the antibody-loaded capture beads, needed to enable PCR-based quantitation of Protein A or any other purification ligand. The kit contains sufficient reagents for 200 reactions. For a kit that includes Protein A capture beads and standards, for use in the quantitation of Protein A, please see the ProteinSEQ™ Protein A Quantitation Kit (Cat. No. 4469343).

• Quantitate leeched protein contaminants with ultra-high sensitivity
• Accelerate process development with more valid test results per run
• Reduce assay hands-on time with less sample dilution and preparation
• Achieve unprecedented productivity with near-5-log assay dynamic range

ProteinSEQ Protein A quantitation
The ProteinSEQ assay platform uses qPCR technology to measure process contaminants with extraordinary sensitivity and unparalleled dynamic range. Protein A or other purification ligands leeching from purification columns can be accurately measured with outstanding spike recovery and dilutional linearity.

Streamlined assay worflow
The ProteinSEQ system is the only instrument platform-based Protein A and purification ligand quantitation solution to offer single-digit picogram sensitivity and nearly 5 logs of dynamic range. Laboratory workflow is greatly accelerated due to the reduction in the number of sample dilutions and replicates in each run.

Pierce™ Rapid Gold BCA Protein Assay Kit (Thermo Scientific™)

The Pierce Rapid Gold BCA Protein Assay Kit is a fast, two-component, high-precision, detergent-compatible assay optimized to determine total protein concentration. It uses the same copper-chelating technology as the well-known traditional Pierce BCA Protein Assay and provides comparable accuracy but with a 5-min, room temperature incubation and measured at 480 nm. This improvement eliminates the need to wait or expose the samples to elevated temperatures for a fast time to results.

Compare all available BCA protein assays ›

Features of the Rapid Gold BCA Protein Assay Kit include:
Absorbance—colorimetric assay, with optimal absorbance at 480 nm
Uniformity—exhibits similar protein-to-protein variation as traditional BCA Protein Assay and less protein-to-protein variation than dye-binding protein assay methods (Bradford)
Compatibility—unaffected by typical concentrations of most ionic and non-ionic detergents
Assay time—5-min, room temperature reaction
Assay range—linear working range for BSA of 20 to 2000 µg/mL

The traditional BCA Protein Assay is a widely used and accepted protein assay, trusted for its highly accurate protein concentration determination and compatibility with most sample types encountered in protein research. However, in order to develop the samples in this traditional protocol, one must either heat the reaction at 37°C for 30 minutes or allow room temperature development for two hours. The Rapid Gold BCA Protein Assay maintains the key characteristics of the traditional BCA assay but allows a fast time and room temperature incubation equal to dye-binding methods. The Rapid Gold BCA assay can be used to assess yields in whole cell lysates and affinity-column fractions, as well as to monitor protein contamination in industrial applications. Compared to most dye-binding methods and similar to the traditional BCA assay, the Rapid Gold BCA assay is affected much less by protein compositional differences, providing low protein-to-protein variation.

How the Rapid Gold BCA Protein Assay detects protein
The Rapid Gold BCA Protein Assay uses the same copper reduction method as the traditional BCA Protein Assay with a unique copper chelator. The assay combines the well-known reduction of Cu2+ to Cu1+ by protein in an alkaline medium with the highly sensitive and selective colorimetric detection of the cuprous cation (Cu1+) by the proprietary chelator. The first step is the chelation of copper with protein in an alkaline environment to form a light green complex. In this reaction, known as the biuret reaction, peptides containing three or more amino acid residues form a colored chelate complex with cupric ions in an alkaline environment containing sodium potassium tartrate.

In the second step of the color development reaction, the Rapid Gold BCA chelator reacts with the reduced (cuprous) cation that was formed in step one. The intense gold-colored reaction product results from the chelation of two molecules of BCA with one cuprous ion. The BCA/copper complex is water soluble and exhibits a strong linear absorbance at 480 nm with increasing protein concentrations. The complex is approximately 100 times more sensitive (lower limit of detection) than the pale green color of the first reaction.

The reaction that leads to the color formation is strongly influenced by four amino acid residues (cysteine, cystine, tyrosine, and tryptophan) in the amino acid sequence of the protein. However, unlike the Coomassie dye-binding methods, the universal peptide backbone also contributes to color formation, helping to minimize variability caused by protein compositional differences.

Compatibility of the Rapid Gold BCA Protein Assay
Certain substances are known to interfere with the Rapid Gold BCA Protein Assay, including those with reducing potential, chelating agents, and strong acids or bases. Because they are known to interfere with protein estimation at even minute concentrations, avoid the following substances as components of the sample buffer:
• Ascorbic acid
• EGTA
• Iron
• Impure sucrose
• Catecholamines
• Impure glycerol
• Lipids
• Tryptophan
• Creatinine
• Hydrogen peroxide
• Melibiose
• Tyrosine
• Cysteine
• Hydrazides
• Phenol Red
• Uric acid

Easy-Titer™ Human IgG (gamma chain) Assay Kit (Thermo Scientific™)

The Thermo Scientific Easy-Titer Human IgG (gamma chain) Assay Kit includes antibody-sensitized microspheres to measure the specific concentration of antibodies by an easy and rapid microagglutination technique using standard microplates and UV-Vis plate reader (spectrophotometer). This kit is specific for the human IgG gamma chain and, unlike total protein assays, can specifically measure the concentration of target antibody in samples (e.g., serum, plasma, culture supernatant) that contain other proteins. It is sensitive, requiring very small sample volumes. Antibody concentration is determined from the assay response (absorbance) by comparison to a standard curve prepared using dilutions of a known antibody sample (sold separately).

General features of Easy-Titer Antibody Assay Kits:

Antibody-based specificity—measure concentration of target antibody in a sample, not just total protein; no need to purify antibody to assess its concentration
Faster and easier than ELISA—three-component, homogenous assay; 10 minutes total incubation time
No special equipment needed—uses standard vortex mixer, pipetter, 96-well microplate, plate shaker and reader (measure absorbance at 340nm or 400nm)
Sensitive—assay range (standard curve) 8 to 500 ng/mL; use sample at 15 to 300 ng/mL for optimal results
Reproducible—coefficient of variation < 5%; error depends on dilution and pipetting technique
Antibody standards sold separately—see product list for suggested products; use any antibody standard with proper target identity and known concentration (greater than 10 µg/mL)
Kits for five popular targets—choose a kit specific for a particular species and class of immunoglobulin; no cross-reaction with other species and classes of the target antibody

Easy-Titer Assay Kits detect and measure specific target antibodies using agglutination of microspheres that are coated ("sensitized") with the specific anti-IgG or IgM polyclonal antibodies. In the appropriate aqueous buffer (supplied in kit), the monodispersed antibody-coated microspheres (> 1 µM diameter) have highest absorptivity (λ-max) to incident light having a wavelength (340nm) that is equal to approximately half their diameter. When sample is added, two or more microspheres bind to each antibody target via their coated specific polyclonal antibodies, and this agglutination into effectively larger apparent spheres results in proportional decrease in absorptivity (lower absorbance).

Typical microagglutination assays depend on a change in light-scattering and corresponding change in transmittance, to which absorbance is inversely related. Easy-Titer Assay Kits use a special dilution buffer whose refractive index eliminates the effect of light-scattering on the monodispersed microspheres for the measurement wavelength used. Because of this, the final 10- to 20-fold dilution of the sample for use in the assay must be done using the Dilution Buffer supplied in the kit.

Easy-Titer Antibody Assays are faster and easier than ELISA:
• Prepare standards (5 to 500 ng/mL) by diluting purified antibody in Kit Dilution Buffer.
• Prepare samples by diluting in Dilution Buffer to within assay range (8 to 500 ng/mL).
• Vortex vial of microsphere beads to create homogeneous suspension.
• Pipette 20 µL of bead suspension and 20 µL of each sample and standard into 96-well microplate wells.
• Incubate microplate for 5 minutes with vigorous mixing.
• Add 100 µL of Kit Blocking Reagent.
• Incubate microplate for 5 minutes with vigorous mixing.
• Measure absorbance on standard plate reader (340nm or 405nm).
• Plot standard curve and interpolate samples to determine concentration.

Related Products
Easy-Titer™ Mouse IgG Assay Kit
Easy-Titer™ Rabbit IgG Assay Kit
Easy-Titer™ Human IgG (H+L) Assay Kit
Easy-Titer™ Human IgM Assay Kit

Compat-Able™ Protein Assay Preparation Reagent Kit (Thermo Scientific™)

The Thermo Scientific Compat-Able Protein Assay Preparation Set eliminates interfering substances from protein assay samples to make them compatible with BCA and Bradford assays.

The Compat-Able Reagents remove salts, detergents, reducing agents and other substances from protein samples to eliminate interference with protein assays. The protocol selectively precipitates all of the protein, thereby allowing the non-protein components to be easily decanted and removed. The purified, precipitated protein is redissolved in water, making it ready for accurate determination of the protein concentration by standard protein assay methods. The procedure is accomplished in less than 10 minutes with just a few simple steps. The Compat-Able Preparation Set is available individually or conveniently bundled with either the Thermo Scientific Pierce BCA Protein Assay Kit or the Thermo Scientific Pierce Coomassie Plus Protein Assay Kit.

Features of the Compat-Able Protein Assay Preparation Reagent Kit:

Eliminate incompatibilities—removes nearly any substance that interferes with colorimetric protein assays: salts, detergents, denaturants, reducing agents, and even IEF sample buffer
Simple and fast—prepare samples in less than 10 minutes with four simple steps
Convenient—reagent set is easier to use than homemade TCA or acetone precipitation reagents, thereby producing more consistent results
Scalable—microcentrifuge method is easily scaled to larger centrifuge tube volumes for special needs
Validated—tested and offered together with BCA and Coomassie Plus Protein Assay Kits; protocol integrates control and normalization procedures

Related Products
Compat-Able™ BCA Protein Assay Kit
Compat-Able™ Coomassie Plus Protein Assay Kit

Pierce™ Bovine Gamma Globulin Standard Ampules, 2 mg/mL (Thermo Scientific™)

Thermo Scientific Pierce BGG Protein Assay Standards are high-quality reference samples for generating accurate standard curves and calibration controls in total protein assays.

Features of BGG Protein Assay Standards:

Convenient—1 mL ampules
Antibody standard—best reference standard for immunoglobulin quantitation in colorimetric protein assays
Bradford standard—best general protein standard in coomassie-based (Bradford) protein assays
Pure and stable—supplied in ultrapure 0.9% saline solution with 0.05% sodium azide; room temperature stable
Accurate and consistent—precisely formulated at 2.00 +/-0.03 mg/mL, ensuring excellent lot-to-lot consistency

These bovine gamma globulin (BGG) solutions are protein concentration reference standards for use in BCA, Bradford and other protein assay protocols. BGG is an accepted reference protein for total protein quantitation of purified antibodies or immunoglobulin-rich samples. The IgG standard is precisely formulated at 2 mg/mL in an ultrapure 0.9% sodium chloride (saline) solution. The concentration of the stock solution of purified BGG (Fraction II) is calibrated by direct comparison to an internal standard to ensure lot-to-lot consistency and accuracy.

Applications:
• Protein assay immunoglobulin quantitation standard (Coomassie-Bradford Assay, etc.)
• Antibody recovery control for desalting and other column procedures
• Loading control for SDS-PAGE
• General calibration of spectrophotometer UV-lamp (absorbance at 280nm)

Selection of a protein standard is potentially the greatest source of error in any protein assay. The best choice for an antibody quantitation standard is a purified, known concentration of the specific immunoglobulin being tested. Often this is not available or it is too expensive to use as a standard. In such cases, the best standard is one that will produce a representative color response curve with the selected protein assay and is readily available to any researcher. BGG provides this function for all kinds of immunoglobulin samples, including IgG.

For greatest accuracy in estimating total protein concentration in unknown samples, it is essential to include a standard curve each time the assay is performed. This is particularly true for the protein assay methods that produce non-linear standard curves. Deciding on the number of standards and replicates used to define the standard curve depends upon the degree of non-linearity in the standard curve and the degree of accuracy required. In general, fewer points are needed to construct a standard curve if the color response is linear. Typically, standard curves are constructed using at least two replicates for each point on the curve.

For added safety when opening glass ampules, consider using our Ampule Breakers, which are disposable safety devices that protect the fingers when breaking open a glass ampule.

Related Products
Pierce™ Bovine Gamma Globulin Standard Pre-Diluted Set

Micro BCA™ Reagent A (MA) (Thermo Scientific™)

The Pierce Micro BCA Reagent A (MA) is a unique alkaline tartrate-carbonate buffer. This product is sufficient for 3,200 microplate assays when mixed with Reagents MB and MC.

Compare all available BCA protein assays ›

Related products
Micro BCA Protein Assay Kit
Micro BCA Reagent B (MB)
Micro BCA Reagent C (MC)

Pierce™ BCA Protein Assay Kit (Thermo Scientific™)

Pierce BCA Protein Assay Kit is a two-component, high-precision, detergent-compatible protein assay for determination of protein concentration. Pierce BCA reagents provide accurate determination of protein concentration with most sample types encountered in protein research. The Pierce BCA assay can be used to assess yields in whole cell lysates, affinity-column fractions, purified proteins samples, as well as to monitor protein contamination in industrial applications. Compared to most dye-binding methods, the BCA assay is affected much less by protein compositional differences, providing greater concentration accuracy.

Compare all available BCA protein assays ›

Features of the BCA Protein Assay Kit include:
Colorimetric—estimate visually or measure with a standard spectrophotometer or plate reader at 562 nm
Uniformity—exhibits less protein-to-protein variation than dye-binding methods (Bradford)
Compatibility—unaffected by typical concentrations of most ionic and non-ionic detergents
Assay time—30-min incubation; much easier and four times faster than classical Lowry methods
Assay range—linear working range for BSA of 20 to 2000 µg/mL
Sensitivity—detect down to 5 µg/mL with enhanced protocol

How the assay works
The BCA Protein Assay combines the well-known reduction of Cu2+ to Cu1+ by protein in an alkaline medium with the highly sensitive and selective colorimetric detection of the cuprous cation (Cu1+) by bicinchoninic acid (BCA). The first step is the chelation of copper with protein in an alkaline environment to form a light blue complex. In this reaction, known as the biuret reaction, peptides containing three or more amino acid residues form a colored chelate complex with cupric ions in an alkaline environment containing sodium potassium tartrate.

In the second step of the color development reaction, BCA reacts with the reduced (cuprous) cation that was formed in step one. The intense purple-colored reaction product results from the chelation of two molecules of BCA with one cuprous ion. The BCA/copper complex is water soluble and exhibits a strong linear absorbance at 562 nm with increasing protein concentrations. The complex is approximately 100 times more sensitive (lower limit of detection) than the pale blue color of the first reaction.

The reaction is strongly influenced by four amino acid residues (cysteine, cystine, tyrosine, and tryptophan) in the amino acid sequence of the protein. However, unlike Coomassie dye-binding methods, the universal peptide backbone also contributes to color formation, helping to minimize variability caused by protein compositional differences.