Shop All Protein Quantitation Assay Kits, Reagents & Standards

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

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

The Thermo Scientific Pierce 660 nm Protein Assay is a ready-to-use, detergent- and reducing agent-compatible assay reagent to quickly measure (A660 nm) total protein concentration compared to a protein standard.

The Pierce 660 nm Assay is more linear than coomassie-based Bradford assays and compatible with higher concentrations of most detergents, reducing agents and other commonly used reagents. 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.

Features of the 660 nm Protein Assay Reagent:

Versatile—works with a greater range of detergents and reducing agents than other dye-based assays
Fast—single reagent with a simple mix-and-read protocol; no working reagent to prepare
Accurate—produces standard curves that are more linear than with the Bradford assay method
Flexible—assay may be performed in test tubes or microplates
Conserve samples—requires only 10 µL for microplate or 100 µL for the test tube procedures
Convenient—room temperature storage means no waiting for reagent equilibration before use

How the Pierce 660nm Assay Detects Protein:
The Pierce 660nm 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 660nm. 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. The optional IDCR may be added to the assay reagent to increase compatibility with high amounts of ionic detergents, allowing samples containing Laemmli SDS sample buffer with bromophenol blue to be measured. The IDCR completely dissolves by thorough mixing and does not have any effect on the assay.

For more information, see the article "Chemistry of Protein Assays" in the Protein Methods Library.

Related Products
Pierce™ 660nm Protein Assay Kit
Ionic Detergent Compatibility Reagent for Pierce™ 660nm Protein Assay Reagent

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

Thermo Scientific Pierce Micro BCA Reagent A (MA) is a proprietary alkaline tartrate-carbonate buffer. This product is sufficient for 3200 microplate assays when mixed with Reagents MB and MC.

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

Compat-Able™ BCA Protein Assay Kit (Thermo Scientific™)

The Thermo Scientific Compat-Able BCA 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™ Coomassie Plus Protein Assay Kit
Ampule Breakers

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

Quant-iT™ Protein Assay Kit (Invitrogen™)

The Quant-iT Protein Assay Kit makes protein quantitation easy and accurate. The kit provides concentrated assay reagent, dilution buffer, and pre-diluted BSA standards. Simply dilute the reagent, load it into the wells of a microplate, add 1-20 µL of sample, mix, then measure the fluorescence. The assay is highly selective for protein and exhibits very little protein-to-protein variation. The assay is performed at room temperature, and the signal is stable for 3 hours. Common contaminants, such as salts, solvents, or DNA—but not detergents—are well tolerated in the assay. Quant-iT DNA Assay Kits (Q33120, Q33130) and a Quant-iT RNA Assay Kit (Q33140) are also available.

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

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

The Thermo Scientific Pierce Coomassie Protein Assay Kit is a ready-to-use, stable formulation of the traditional Bradford assay reagent to measure (A595 nm) total protein concentration compared to a protein standard.

The Pierce Coomassie Protein Assay Kit is a ready-to-use formulation of the popular assay reagent originally described by Bradford in 1976. When mixed with a protein solution, the acidic coomassie-dye reagent changes color from brown to blue in proportion the amount of protein present in the sample. Protein determinations are made by comparison to the color response of protein assay standards, usually prepared as a series of known dilutions of bovine serum albumin (BSA) or bovine gamma globulin (BGG). The kit includes Coomassie Protein Assay Reagent and a package of Albumin Standard Ampules. The simple procedure is adaptable to nearly any volume scale, including test tubes, cuvettes and microplates.

Features of the Coomassie Protein Assay Kit:

Bradford reagent—stable, ready-to-use kit of the classical Bradford assay reagent
Colorimetric—measure with a standard spectrophotometer or plate reader (595 nm)
Easy to use—single reagent; no working reagent preparation required
Fast—almost immediate color development; add, mix and read results
Broad range—detects protein concentration in the range 1 to 1500 µg/mL
Flexible—microplate and cuvette protocols provided with the instructions and adaptable to several target working ranges

How the Coomassie (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 465nm) 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 3000 daltons to be assayed with this reagent. The assay is performed at room temperature and no special equipment is required. 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 coomassie dye containing protein assay is compatible with most salts, solvents, buffers, thiols, reducing substances and metal chelating agents encountered in protein samples.

For more information, see the article "Chemistry of Protein Assays" in the Protein Methods Library.

Related Products
Pierce™ Coomassie Plus (Bradford) Assay Kit
Pierce™ Detergent Compatible Bradford Assay Kit
Ampule Breakers

Pierce™ Microplate BCA Protein Assay Kit - Reducing Agent Compatible (Thermo Scientific™)

This BCA Protein Assay Kit is the reducing agent-compatible version of our popular Thermo Scientific Pierce BCA Protein Assay. The kit enables you to measure protein concentration in samples that contain thiol-reductants dithiothreitol (DTT) and 2-mercaptoethanol (BME), and comes with 20 96-well microplates.

Features of the Microplate BCA Protein Assay Kit—Reducing Agent Compatible:

Compatible—assay samples that contain up to 5 mM DTT, 35 mM BME, or 10 mM TCEP
BCA technology—only a slight modification of the standard BCA Protein Assay protocol (15-minute incubation with Compatibility Reagent); no precipitation steps required
Small samples—requires only 25 µL (standard kit) or less than 10 µL (microplate kit) of sample
Colorimetric—measure with a standard spectrophotometer or plate reader (562nm)
Excellent uniformity—exhibits less protein-to-protein variation than dye-binding methods
High linearity—linear working range for BSA equals 125 to 2000 µg/mL

The BCA Protein Assay Kit—Reducing Agent Compatible (BCA-RAC) provides all of the advantages of the original BCA Assay, plus compatibility with disulfide reducing agents at concentrations routinely used in protein sample buffers. This special adaptation of the popular Pierce BCA Protein Assay method enables accurate protein concentration measurement for samples containing DTT, 2-ME or TCEP. This reducing agent compatible (RAC) BCA Kit extends the already broad reagent compatibility of the BCA Protein Assay protocol to include nearly all types of components commonly present in protein research samples.

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Pierce™ BCA Protein Assay Kit - Reducing Agent Compatible
96-Well Plates for Pierce™ BCA-RAC Assay
Ampule Breakers

Pierce™ BCA Protein Assay Kit - Reducing Agent Compatible (Thermo Scientific™)

This BCA Protein Assay Kit is the reducing agent-compatible version of our popular Thermo Scientific Pierce BCA Protein Assay. The kit enables you to measure protein concentration in samples that contain thiol-reductants dithiothreitol (DTT) and 2-mercaptoethanol (BME).

Features of the BCA Protein Assay Kit—Reducing Agent Compatible:

Compatible—assay samples that contain up to 5 mM DTT, 35 mM BME, or 10 mM TCEP
BCA technology—only a slight modification of the standard BCA Protein Assay protocol (15-minute incubation with Compatibility Reagent); no precipitation steps required
Small samples—requires only 25 µL (standard kit) or less than 10 µL (microplate kit) of sample
Colorimetric—measure with a standard spectrophotometer or plate reader (562nm)
Excellent uniformity—exhibits less protein-to-protein variation than dye-binding methods
High linearity—linear working range for BSA equals 125 to 2000 µg/mL

The BCA Protein Assay Kit—Reducing Agent Compatible (BCA-RAC) provides all of the advantages of the original BCA Assay, plus compatibility with disulfide reducing agents at concentrations routinely used in protein sample buffers. This special adaptation of the popular Pierce BCA Protein Assay method enables accurate protein concentration measurement for samples containing DTT, 2-ME or TCEP. This reducing agent compatible (RAC) BCA Kit extends the already broad reagent compatibility of the BCA Protein Assay protocol to include nearly all types of components commonly present in protein research samples.

Related Products
Pierce™ Microplate BCA Protein Assay Kit - Reducing Agent Compatible
96-Well Plates for Pierce™ BCA-RAC Assay

Pierce™ BCA Protein Assay Kit (Thermo Scientific™)

The Thermo Scientific Pierce BCA Protein Assay Kit is a two-component, high-precision, detergent-compatible assay reagent set to measure (A562nm) total protein concentration compared to a protein standard. Used in more labs than any other detergent-compatible protein assay, 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 and affinity-column fractions, 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 protein-to-protein uniformity.

Features of the BCA Protein Assay Kit:
• Colorimetric—estimate visually or measure with a standard spectrophotometer or plate reader (562nm)
• Excellent uniformity—exhibits less protein-to-protein variation than dye-binding methods
• Compatible—unaffected by typical concentrations of most ionic and nonionic detergents
• Moderately fast—much easier and four times faster than the classical Lowry method
• High linearity—linear working range for BSA equals 20 to 2000 µg/mL
• Sensitive—detect down to 5 µg/mL with the enhanced protocol

Applications:
• Studying protein:protein interactions
• Measuring column fractions after affinity chromatography
• Estimating percent recovery of membrane proteins from cell extracts
• High-throughput screening of fusion proteins

How the BCA Protein Assay Detects Protein:
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. 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, bicinchoninic acid (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 BCA reagent is approximately 100 times more sensitive (lower limit of detection) than the pale blue color of the first reaction.

The reaction that leads to BCA color formation is strongly influenced by four amino acid residues (cysteine or 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.

For more information, see the article "Chemistry of Protein Assays" in the Protein Methods Library.

ProteinSEQ™ CHO HCP Quantitation Kit (Applied Biosystems™)

The ProteinSEQ™ CHO HCP Quantitation Kit is an assay kit containing all reagents and buffers needed to perform 200 PCR reactions to quantify process-independent host cell proteins from CHO cell lines. It combines a broadly reactive anti-CHO HCP antibody with a qPCR-based TaqMan™ Assay platform to enable measurements of HCPs with high sensitivity and wide dynamic range.

The ProteinSEQ CHO HCP Quantitation Kit contains:

• Capture beads loaded with anti-CHO HCP antibody
• CHO HCP standards
• All reagents and buffers needed to perform 200 PCR reactions for the process-independent quantitation of host cell proteins

Features include:

• Precise—quantitate host cell protein contaminants with excellent precision
• Fast—helps accelerate process development with more valid test results per run
• Efficient—helps reduce hands-on time with less sample dilution and preparation
• Reproducible—achieve unprecedented productivity with 4-log dynamic range

ProteinSEQ CHO HCP quantitation
The ProteinSEQ assay platform uses qPCR technology to measure protein process contaminants with extraordinary sensitivity and unparalleled dynamic range. Host cell protein contaminants from CHO cell lines can be accurately measured from 0.5–3,150 ng/mL, with outstanding quantitation efficiency and dilutional linearity.

Streamlined workflow
The ProteinSEQ CHO HCP Quantitation Kit is the only instrument platform-based HCP quantitation solution to deliver a generic, process-independent HCP assay with class-leading sensitivity and 4-log dynamic range. The kit helps accelerate laboratory workflows because the number of sample dilutions and replicates is reduced in each run.

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