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

The Thermo Scientific Pierce Coomassie Plus Protein Assay is a ready-to-use, reducing agent-compatible, improved Bradford assay reagent to quickly measure (A595nm) total protein concentration compared to a protein standard.

The Pierce Coomassie Plus Assay Reagent is a single, ready-to-use solution for measuring protein concentration. Simply add the reagent to equal volumes of samples and standards, mix and then measure the absorbance at 595nm. The assay costs only pennies per sample and can be performed in either test tube or microplate format. The Pierce Coomassie Plus Assay Reagent provides increased linearity of response and only half the protein-to-protein variability of other commercial Bradford assay formulations.

Features of the Coomassie Plus Protein Assay:

Colorimetric—measure with a standard spectrophotometer or plate reader (595nm)
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
Better—improved linearity and response-uniformity compared to traditional Bradford formulations
Flexible—microplate and cuvette protocols provided with the instructions and adaptable to several target working ranges

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 465nm) to the blue form of the dye (absorbance maximum at 610nm). The difference between the two forms of the dye is greatest at 595nm, 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 575nm and 615nm. At the two extremes (575nm and 615nm) there is a loss of about 10% in the measured amount of color (absorbance) compared to that obtained at 595nm.

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. 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 595nm 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.

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Pierce™ Coomassie Plus (Bradford) Assay Kit
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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

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Compat-Able™ Protein Assay Preparation Reagent Kit
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Pierce™ HA-Tag Magnetic IP/Co-IP Kit (Thermo Scientific™)

The Thermo Scientific Pierce Magnetic HA-Tag IP/Co-IP Kit contains specific immunoaffinity magnetic beads and reagents to perform immunoprecipitation assays of HA fusion proteins or co-IP experiments using HA-tagged bait proteins.

Features of the HA-Tag Magnetic IP/Co-IP Kit:

Specific magnetic beads—covalently immobilized high-quality anti-HA monoclonal antibody enables high yields of immunoprecipitation products
Low non-specific binding—stable, pre-blocked beads and specific antibody minimize off-target binding
Trouble-free elution—low-pH elution buffer ensures recovery of HA-tagged protein interaction complexes without antibody leaching contamination
Convenient and fast—complete kit and easy-to-follow instructions provide optimized protocols to perform IP or Co-IP experiment in approximately 1 hour
Versatile—magnetic beads are compatible with manual and automated magnetic separation workflows (e.g., Thermo Scientific KingFisher Instruments)

Unlike traditional IP procedures based on capture with Protein A/G beads, this kit uses magnetic beads containing pre-immobilized anti-HA antibody. These Pierce Anti-HA Magnetic Beads ensure specific binding of HA-tagged protein complexes from biological samples. Because the antibody is covalently attached to the beads, IP-targets are easily eluted and recovered without antibody contamination. The complete IP kit includes the magnetic beads, lysis/wash buffer, low-pH elution buffer, neutralization buffer, HA-tag positive control lysate, and non-reducing sample buffer for SDS-PAGE. Protocols are provided for both manual and automated magnetic separation workflows. Sufficient components are provided to perform 40 IP or co-IP assays.

The hemagglutinin (HA) peptide (YPYDVPDYA), derived from the human influenza virus HA protein, is one of several fusion protein tags used for recombinant protein expression. The Pierce Magnetic HA-Tag IP/Co-IP Kit uses a specific, high-affinity immobilized antibody (clone 2-2.2.14) for rapid purification of HA-tagged fusion proteins from bacterial and mammalian cell lysates, as well as from lysates prepared with the Pierce Human in vitro Translation Kits. The beads are incubated with a cell lysate containing HA-tagged protein, the fusion protein is captured, and the beads are subsequently washed and then eluted using low-pH elution buffer or non-reducing sample buffer. The protocol and buffers have been optimized for both IP and co-IP reactions, enriching for specific protein interaction complexes in the eluted samples. Anti-HA antibody can be used to detect HA-tagged protein by Western blot analysis.

For information about the binding capacity and other properties of the magnetic beads used in this kit, see Pierce Anti-HA Magnetic Beads (Part No. 88836).

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Pierce™ HA-Tag IP/Co-IP Kit

Pierce™ Streptavidin Coated Plate IP Kit (Thermo Scientific™)

The Thermo Scientific Pierce Streptavidin Coated Plate IP Kit uses coated streptavidin microplates to perform immunoprecipitation assays in 96-well plates without resins, beads, centrifugation or magnets.

Pierce Coated Plate IP Kits enable rapid immunoprecipitation of multiple samples without the usual tedium of pipetting, centrifuging and separating beaded affinity resin in individual microcentrifuge tubes. Immunoprecipitation is accomplished using coated 96-well microplates rather than beaded agarose resin. The plate format allows for faster processing of multiple samples.

Features of the Streptavidin Coated Plate IP Kit:

• Ready-to-use, high quality coated plates provide high capacity and consistency
• Plate format best suited for simultaneously processing multiple samples and their control conditions
• Faster, easier and more thorough washing than with traditional tube/resin IP methods
• Uses familiar and convenient ELISA tools (multichannel pipettors and plate washing); no tedious separation of supernatant from pelleted resin beads, and no tubes to open and close and centrifuge
• Coated plates are 96-well strip plates, convenient for experiments requiring only a partial plate
• Easy-to-follow instructions, including detailed explanation of appropriate controls

Applications:
• Rapid, trouble-free immunoprecipitation of multiple samples and their controls
• Immunoprecipitation when plate-based tools and techniques are preferred

Streptavidin is a protein that binds specifically and very strongly to biotin; therefore, the Streptavidin Coated Plate IP Kit (Part No. 45360) is appropriate for immunoprecipitation when using a biotin-labeled (biotinylated) antibody. In fact, this kit can be used to affinity purify a binding partner to any antibody species or subclass or any other protein or molecule that is biotinylated. Because the streptavidin-biotin affinity interaction is so strong, the elution step generally will dissociate only the antigen (binding partner), not the biotinylated antibody or "bait" protein.

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Pierce™ His Protein Interaction Pull-Down Kit (Thermo Scientific™)

Thermo Fisher Scientific Pierce His Tag Protein Interaction Pull-Down Kit contains the necessary components to capture and purify proteins that interact with His-tagged fusion proteins.

Features of His Tag Protein Interaction Pull-Down Kit:

6xHis pull-down (Product No. 21277)—purifies protein interactors of any His-tagged fusion protein
Complete kits—provide all components and detailed protocol for purifying protein:protein interactions
No special equipment needed—use common laboratory equipment and reagents (e.g., microcentrifuge)
Convenient—microcentrifuge spin columns facilitate simple and efficient manipulation of agarose beads, including simple processing of multiple samples
Flexible—instructions include protocols for use with bait and prey proteins expressed from a variety of sample types
Less non-specific binding—Cobalt chelate resin is more specific for histidine-tagged fusion proteins than nickel resins, resulting in less non-specific binding
Binding—Binds 10 to 25 mg of histidine-tagged fusion protein per mL of resin

Applications:

• Discover a new protein:protein interaction from a cell lysate
• Confirm a putative interaction from a cell lysate or with a previously purified protein
• Extract protein:protein interaction information from in vitro transcription/translation lysates

You provide the tagged fusion protein as the "bait" and the cells expressing the putative protein interaction target ("prey"), and the Pull-Down Kits provide everything else: cell lysis buffer, microcentrifuge spin columns, tag-specific affinity resin (agarose beads) and optimized buffers and protocol. The Pull-Down Kits are designed to teach the method to first-time users and to increase ease-of-use, convenience and reproducibility for experienced researchers.

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

The Thermo Scientific Pierce Rapid Gold BCA Protein Assay Kit is a two-component, high-precision, detergent-compatible assay optimized to measure (at 480 nm) total protein concentration compared to a protein standard curve of known concentrations. The Pierce Rapid Gold BCA Protein Assay uses the same copper-chelating technology as the well-known traditional Pierce BCA Protein Assay and provides comparable accuracy but with a 5 minute, 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.

Features of the Rapid Gold BCA Protein Assay Kit:
• Colorimetric—estimate visually or measure with a standard spectrophotometer or plate reader (480 nm)
• Excellent uniformity—exhibits similar protein-to-protein variation as traditional BCA Protein Assay, and less protein-to-protein variation than dye-binding protein assay methods
• Compatible—unaffected by typical concentrations of most ionic and nonionic detergents
• Fast time to results—significant improvement over traditional BCA Assay with a 5 minute, room temperature reaction
• High linearity—linear working range for BSA equals 20 to 2000 µg/mL
• Optimal absorbance on standard spectrophotometers—reaction produces a color change to an intense orange-gold that results in a strong linear response at 480 nm

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 2 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.

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 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 proprietary copper chelator. The Rapid Gold BCA 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 BCA reagent 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 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.

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

Protein assays using a copper chelator are found to be highly advantageous in that most surfactants (even if present in the sample at concentrations up to 5%) are compatible with the assay. Thermo Fisher Scientific has performed extensive compatibility experiments on all of our protein assays, in particular for the traditional BCA Protein Assay. The new Rapid Gold BCA Protein Assay was determined to have similar compatibility of interfering substances as traditional BCA. Additional data and information can be found in the instructional booklet for each protein assay.

PIP Strips™ Membranes (Invitrogen™)

PIP Strips™ membranes are designed for the identification of proteins possessing phosphoinositide domains and for analysis of their lipid-binding specificities. PIP Strips™ membranes facilitate the analysis of phosphoinositide protein interactions by protein-lipid overlay assays. Proteins may be detected using standard western blot procedures in conjunction with high-performance alkaline phosphatase- and horseradish peroxidase (HRP)-mediated signal generation systems.

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.

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Pro-Detect™ Rapid Antibody Isotyping Assay Kit, rat (Thermo Scientific™)

The Thermo Scientific Pro-Detect Rapid Antibody Isotyping Assay Kit - Rat is a single-use, dipstick lateral flow kit for quick, easy determination of rat monoclonal antibody class and subclass identity. This antibody isotyping assay uses membrane-based strips coated with dye-bound conjugated antibodies that provide a visual, color readout of the monoclonal antibody isotype within ten minutes. The kit determines rat IgG1, IgG2a, IgG2b , and IgG2c.

Features of the Pro-Detect Rapid Antibody Isotyping Assay Kit:
Long shelf life—stable for at least one year at 4°C
Simple workflow—dilute antibody sample using provided diluent and dip in the lateral flow strip
Fast—within 5–10 minutes a band appears that indicates the antibody isotype
Sensitive—detect antibodies in tissue culture media or ascites fluid samples down to low ng/mL concentrations
Specific—assay does not cross-react with fetal bovine serum (FBS)
Reliable—results are similar to standard ELISA-based isotyping assays

Each Pro-Detect Rapid Antibody Isotyping assay is performed by simply adding a properly diluted tissue culture supernatant or mouse ascites sample to a test tube or microplate well and dipping in a lateral flow strip. Gold conjugates embedded in the strip membrane form specific class- and subclass-soluble complexes with the antibodies in the sample. These complexes travel the length of the membrane and are resolved on the anti-isotype and class-specific antibody-impregnated regions of the membrane. Results are displayed as a red band above the printed class or sub-class description, indicating the antibody isotype present.

Determining the subclass of a rat antibody is important when selecting the best purification method. IgG2a, IgG2b, and IgG2c can be purified with Protein A columns at a pH of 7–8. IgG1 isotypes bind best to Protein A at a slightly higher pH of 8–9.

The Pro-Detect Rapid Antibody Isotyping Assay Kit is compatible with both tissue culture supernatant and mouse ascites fluid, and is more sensitive than conventional latex bead-based dipstick assays and much faster than ELISA-based isotyping assays. The kit requires only 0.5 µL ascites fluid, 2–22 µL of cell culture supernatant or 1.5 ng of purified antibody.

GlycoLink™ IP Kit (Thermo Scientific™)

The Thermo Scientific GlycoLink IP Kit provides components for effective immunoprecipitation (IP and co-IP) based on small-scale, covalent, affinity-resin immobilization of antibodies and other glycoproteins via oxidized sugar groups.

Features of the GlycoLink IP Kit:

Efficient immobilization—couple 2 to 10 µg of oxidized antibody or other glycoprotein to 20 µL of resin in 2 hours or less
Stable immobilization—resonance structure of the hydrazone bonds are sufficiently stable so the antibody remains coupled during elution
Preserves binding function—immobilizes IgG via the Fc region, thereby keeping both antigen binding sites available for capturing target
Versatile applications—immobilize any molecule that contains oxidizable sugars, including glycoproteins for use in purifying protein interaction binding partners

The GlycoLink Kit uses hydrazide-activated UltraLink Resin to immobilize and perform 25 IP or Co-IP assays with different antibodies or glycoprotein ligands. The method is ideal for polyclonal antibodies, which typically have abundant carbohydrates (glycosylation) on their Fc portions. Monoclonal antibodies that contain adequate carbohydrates are also effective. Antibodies immobilized by this hydrazide-to-carbohydrate method have unobstructed antigen-binding sites and optimal purification capability. The prepared glycoprotein or antibody columns can be regenerated and reused at least five times for immunoprecipitation, co-immunoprecipitation or pull-down affinity-purification without significant loss in binding capacity.

Applications:
• Immunoprecipitation followed by electrophoresis and excision of the protein for mass spectrometry or sequencing
• Immunoprecipitation and SDS-PAGE analysis of a protein with a molecular weight similar to the antibody's heavy or light chain
• Identification of binding partners of immobilized glycoprotein
• Co-immunoprecipitation for determining protein-protein interactions

Includes:
Kit contains resin, buffers and reagents for immobilization; desalting columns; IP lysis/wash and elution buffers for immunoprecipitation; microcentrifuge spin columns and collection tubes; and loading buffer for SDS-PAGE

The GlycoLink IP Kit method results in covalent attachment of oxidized sugar groups of an IP antibody (or any other glycoprotein with oxidizable carbohydrate groups) to the hydrazide resin. The antibody resin is then incubated with the sample that contains the protein antigen of interest, allowing the antibody-antigen complex to form. After washing to remove non-bound components of the sample, the antigen is recovered by dissociation from the antibody with elution buffer supplied in the kit. The entire procedure is performed in a microcentrifuge spin cup, allowing solutions to be fully separated from the resin with a brief centrifugation. Only the antigen is eluted by the procedure, enabling it to be identified and further analyzed without interference from antibody fragments.

More Product Data
Improved immobilization and conjugation of glycoproteins

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.

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tRNA for LightShift™ Chemiluminescent RNA EMSA Kit (Thermo Scientific™)

tRNA, formulation: Transfer RNA at 10 mg/mL in 10mM HEPES.
Sufficient For: 100 binding reactions

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Pierce™ Bovine Serum Albumin Standard Pre-Diluted Set (Thermo Scientific™)

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

Features of BSA Protein Assay Standards:

Convenient—complete set containing seven ready-to-use dilutions
Universal—recognized as the industry standard for protein quantitation in colorimetric protein assays
Pure and stable—supplied in ultrapure 0.9% saline solution with 0.05% sodium azide

These bovine serum albumin (BSA) solutions are protein concentration reference standards for use in BCA, Bradford and other protein assay protocols. BSA is the universally accepted reference protein for total protein quantitation. The set of standards is prepared from a stock solution that is calibrated by direct comparison to purified BSA (Fraction V) from the National Institute of Standards and Technology (NIST).

Applications:
• Protein assay quantitation standard (BCA Protein Assay, Coomassie-Bradford Assay, etc.)
• Protein recovery control for desalting and other column procedures
• 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 a standard is a purified, known concentration of the most abundant protein contained in the samples being tested. Often, a highly purified, known concentration of the protein of interest is not available or it is too expensive to use as the standard, or the sample itself is a mixture of many proteins (e.g., cell lysate). In such cases, the best standard is one that will produce a normal (i.e., average) color response curve with the selected protein assay method and is readily available to any researcher. BSA is such a protein, and the Pierce Albumin Standards are the most convenient source of ready-to-use BSA standard.

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.

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Pierce™ Cell Surface Biotinylation and Isolation Kit (Thermo Scientific™)

The Thermo Scientific Pierce Cell Surface Protein Biotinylation and Isolation Kit enables the selective biotinylation, solubilization, and enrichment of plasma membrane proteins.

Features of the Cell Surface Protein Biotinylation and Isolation Kit include:
Improved performance—kit and protocol have been re-designed to improve enrichment and extraction of biotinylated plasma membrane proteins while minimizing intracellular protein contamination
Optimized—protocol has been refreshed to reduce processing time and the number of steps, and reagent formulations optimized for improved performance
Compatible—reagents have been verified with suspension and adherent cell lines, with additional instructions provided for MS sample preparation
Validated applications—reagents and procedures are compatible with western blotting and MS applications

This easy-to-use kit provides all of the necessary components and procedure for optimal labeling and subsequent isolation of cell surface proteins. Buffers are supplied pre-formulated to produce consistent results. Mammalian cells are first labeled with EZ-Link Sulfo-NHS-SS-Biotin, a thiol-cleavable amine-reactive biotinylation reagent. Cells are subsequently lysed and the labeled proteins are captured with NeutrAvidin Agarose. Dithiothreitol (DTT) is used in the elution to reduce the disulfide bonds in the biotin label, resulting in the release of the bound proteins without the biotin label. This kit contains sufficient reagents for eight experiments, consisting of two 85-95% confluent 15-cm dishes or four 75-cm2 flasks.

Cell surface proteins represent a key subset of cellular proteins and play major roles in signal transduction, cell adhesion, and ion transport. These proteins are challenging to efficiently extract and isolate due to their multiple membrane-spanning domains. Often, the harsh detergents and conditions necessary for efficient extraction result in denaturation and contamination of plasma membrane proteins after isolation. As an alternative, this kit utilizes a membrane-impermeable, amine-reactive, sulfo-NHS-SS-biotin to efficiently label cell surface proteins with accessible lysines. The lysis, capture, wash, and elution conditions have been optimized for efficient enrichment and isolation while minimizing contamination of intracellular proteins.

The protocol has been optimized for use with diverse mammalian cell lines, including adherent and suspension cells, and is useful for differential expression analysis between treated and non-treated cells or between one or more cell lines. Selectivity and efficiency of the cell surface protein isolation has been verified by western blotting and LC-MS analysis.

Pro-Detect™ Rapid Antibody Isotyping Assay Kit, human (Thermo Scientific™)

The Thermo Scientific Pro-Detect Rapid Antibody Isotyping Assay Kit - Human is a single-use, dipstick lateral flow kit for quick, easy determination of rat monoclonal antibody class and subclass identity. This antibody isotyping assay uses membrane-based strips coated with dye-bound conjugated antibodies that provide a visual, color readout of the monoclonal antibody isotype within ten minutes. The kit determines human IgG1, IgG2, IgG3, IgG4, IgA, IgM, as well as light-chain identity (kappa vs. lambda light chains).

Features of the Pro-Detect Rapid Antibody Isotyping Assay Kit:
Long shelf life—stable for at least one year at 4°C
Simple workflow—dilute antibody sample using provided diluent and dip in the lateral flow strip
Fast—within 5–10 minutes a band appears that indicates the antibody isotype
Sensitive—detect antibodies in tissue culture media or ascites fluid samples down to low ng/mL concentrations
Specific—assay does not cross-react with fetal bovine serum (FBS)
Reliable—results are similar to standard ELISA-based isotyping assays

Each Pro-Detect Rapid Antibody Isotyping assay is performed by simply adding a properly diluted tissue culture supernatant or mouse ascites sample to a test tube or microplate well and dipping in a lateral flow strip. Gold conjugates embedded in the strip membrane form specific class- and subclass-soluble complexes with the antibodies in the sample. These complexes travel the length of the membrane and are resolved on the anti-isotype and class-specific antibody-impregnated regions of the membrane. Results are displayed as a red band above the printed class or sub-class description, indicating the antibody isotype present.

Determining the class and subclass of a human antibody is important in a variety of research areas including infectious disease, cancer, autoimmune diseases, immunodeficiency disorders, and drug and vaccine development. Isotyping is also important when developing and purifying humanized antibodies.

The Pro-Detect Rapid Antibody Isotyping Assay Kit is compatible with both tissue culture supernatant and mouse ascites fluid, and is more sensitive than conventional latex bead-based dipstick assays and much faster than ELISA-based isotyping assays. The kit requires only 2–22 µL of cell culture supernatant.

Pierce™ Bovine Serum Albumin Standard, 2 mg/mL (Thermo Scientific™)

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

Features of BSA Protein Assay Standards:

Convenient—50 mL bottle
Universal—recognized as the industry standard for protein quantitation in colorimetric 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 compared to an NIST reference

These bovine serum albumin (BSA) solutions are protein concentration reference standards for use in BCA, Bradford and other protein assay protocols. BSA is the universally accepted reference protein for total protein quantitation. The albumin standard is precisely formulated at 2 mg/mL in an ultrapure 0.9% sodium chloride (saline) solution. The concentration of the stock solution is calibrated by direct comparison to purified BSA (Fraction V) from the National Institute of Standards and Technology (NIST).

Applications:
• Protein assay quantitation standard (BCA Protein Assay, Coomassie-Bradford Assay, etc.)
• Protein recovery control for desalting and other column procedures
• 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 a standard is a purified, known concentration of the most abundant protein contained in the samples being tested. Often, a highly purified, known concentration of the protein of interest is not available or it is too expensive to use as the standard, or the sample itself is a mixture of many proteins (e.g., cell lysate). In such cases, the best standard is one that will produce a normal (i.e., average) color response curve with the selected protein assay method and is readily available to any researcher. BSA is such a protein, and the Pierce Albumin Standards are the most convenient source of ready-to-use BSA standard.

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.

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Pierce™ Bovine Serum Albumin Standard Pre-Diluted Set

Pierce™ Crosslink IP Kit (Thermo Scientific™)

The Thermo Scientific Pierce Crosslink IP Kit adapts the traditional IP method to include reagents and protocol for crosslinking IP antibodies to Protein A/G agarose to enable antigen immunoprecipitation without antibody contamination.

The primary benefits resulting from these features are the ability to purify target protein without contamination by the antibody and the ability to more effectively wash and separate samples from the beaded agarose resin.

Features of the Crosslink IP Kit:

Eliminates antibody contamination—antibody is irreversibly attached to the agarose beads so that co-elution of heavy and light chains with the purified protein is minimized
Easy and efficient scalability—use only the amount of antibody needed for a single IP experiment or immobilize 100-200 µg of antibody to prepare ready-made IP affinity resin for many experiments
Assay reliability and sample handling—Pierce Spin Columns eliminate resin loss and provide for more efficient separation of solutions than traditional IP methods that use only microcentrifuge tubes
Prepared antibody affinity resin is reusable—because the antibody is covalently immobilized and usually is not inactivated by the mild elution procedure, the resin often can be used several times
Complete kits—package includes sufficient reagents and spin columns to perform at least 50 antibody immobilizations and IP experiments

Applications:
• Immunoprecipitation followed by electrophoresis and excision of the protein for mass spectrometry or sequencing identification analysis
• Immunoprecipitation and SDS-PAGE analysis of a target protein whose molecular weight is similar to the heavy or light chain antibody fragment
• Immunoprecipitation of target proteins for subsequent analysis by nondenaturing methods (i.e., methods not involving SDS-PAGE)

The Pierce Crosslink IP Kit method involves capturing the IP antibody to Protein A/G Agarose resin and covalently immobilizing it to the support by crosslinking with disuccinmidyl suberate (DSS). The antibody resin is then incubated with the sample that contains the protein antigen of interest, allowing the antibody:antigen complex to form. After washing to remove nonbound (presumably undesired) components of the sample, the antigen is recovered by dissociation from the antibody with elution buffer supplied in the kit. The entire procedure is performed in a microcentrifuge spin cup, allowing solutions to be fully separated from the agarose resin upon brief centrifugation. Only antigen is eluted by the procedure, enabling it to be identified and further analyzed without interference from antibody fragments. Furthermore, the antibody resin often can be reused for additional rounds of immunoprecipitation.

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Pierce™ Crosslink Magnetic IP/Co-IP Kit

Pierce™ c-Myc-Tag Magnetic IP/Co-IP Kit (Thermo Scientific™)

The Thermo Scientific Pierce Magnetic c-Myc-Tag IP/Co-IP Kit contains specific immunoaffinity magnetic beads and reagents to perform immunoprecipitation assays of c-Myc fusion proteins or co-IP experiments using c-Myc-tagged bait proteins.

Unlike traditional IP procedures based on capture with Protein A/G beads, this kit uses magnetic beads containing pre-immobilized anti-c-Myc antibody. These Pierce Anti-c-Myc Magnetic Beads ensure specific binding of c-Myc tagged protein complexes from biological samples. Because the antibody is covalently attached to the beads, IP-targets are easily eluted and recovered without antibody contamination. The complete IP kit includes the magnetic beads, lysis/wash buffer, low-pH elution buffer, neutralization buffer, c-Myc-tag positive control lysate, and non-reducing sample buffer for SDS-PAGE. Protocols are provided for both manual and automated magnetic separation workflows. Sufficient components are provided to perform 40 IP or co-IP assays.

Features of the c-Myc-Tag Magnetic IP/Co-IP Kit:

Specific magnetic beads—covalently immobilized high-quality anti-c-Myc monoclonal antibody enables high yields of immunoprecipitation products
Low non-specific binding—stable, pre-blocked beads and specific antibody minimize off-target binding
Trouble-free elution—low-pH elution buffer ensures recovery of c-Myc-tagged protein interaction complexes without antibody leaching contamination
Convenient and fast—complete kit and easy-to-follow instructions provide optimized protocols to perform IP or Co-IP experiment in approximately 1 hour
Versatile—magnetic beads are compatible with manual and automated magnetic separation workflows (e.g., Thermo Scientific KingFisher Instruments)

The c-Myc peptide (EQKLISEEDL) derived from the C-terminus region of human c-Myc protein is one of several fusion protein tags used for recombinant protein expression. The Pierce c-Myc Magnetic IP/Co-IP Kit uses a specific, high-affinity immobilized antibody (clone 9E10) for rapid immunoprecipitation of c-Myc tagged fusion proteins from bacterial and mammalian cell lysates, as well as from lysates prepared with the Pierce Human in vitro Translation Kits. The beads are incubated with a cell lysate containing c-Myc tagged protein, the fusion protein is captured, and the beads are subsequently washed and then eluted using low-pH elution buffer or non-reducing sample buffer. The protocol and buffers have been optimized for both IP and co-IP reactions, enriching for specific protein interaction complexes in the eluted samples. Anti-c-Myc antibody can be used to detect c-Myc tagged protein by Western blot analysis.

For information about the binding capacity and other properties of the magnetic beads used in this kit, see Pierce Anti-c-Myc Magnetic Beads (Part No. 88842).

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Pierce™ c-Myc-Tag IP/Co-IP Kit

Pierce™ Rapid Antibody Isotyping Kit - Mouse (Thermo Scientific™)

The Thermo Scientific Pierce Rapid Mouse Antibody Isotyping Kit is a single-use, cassette-based kit for 5-minute lateral-flow assay determination of mouse monoclonal antibody class and subclass identity.

This antibody isotyping kit uses cartridges that provide a color-readout of the monoclonal antibody isotype within five minutes after pipetting a small amount of diluted culture supernatant or ascites fluid sample into the sample well. The kit determines mouse IgG1, IgG2a, IgG2b, IgG3, IgA, IgM.

Features of the Pierce Rapid Mouse Antibody Isotyping Kit:

Long shelf life—stable for at least one year at room temperature
Single-step—add diluted antibody sample to the loading-well of cassette
Fast—within 5 minutes a band appears that indicates the antibody isotype
Sensitive—detect antibodies in tissue culture media or ascites fluid samples at any concentration greater than 10 ng/mL
Specific—assay does not cross-react with fetal bovine serum (FBS)
Reliable—results are similar to the standard ELISA-based isotyping assays

Each Pierce Rapid Isotyping Kit assay is performed by simply adding a properly diluted tissue culture supernatant or mouse ascites sample to the well of the small cassette. Gold conjugates embedded in the cassette form specific class- and subclass-soluble complexes with the antibodies in the sample. These complexes travel the length of the membrane and are resolved on the anti-isotype and class-specific antibody-impregnated membrane. Results are displayed as a red band indicating the antibody isotype or subclass.

Determining the class and subclass of a monoclonal antibody is useful in planning the best immunoglobulin purification method. For example, mouse IgA and IgM are best purified by size (i.e., gel exclusion) or using immunoaffinity separation columns. Mouse IgG2a and IgG2b are purified with immobilized Protein A at pH 7-8, while Mouse IgG1 binds best to Protein A at pH 8-9. Immunoglobulin that contains kappa light chains can be purified using immobilized Protein L.

The Pierce Rapid Isotyping Kit is compatible with both tissue culture supernatant and mouse ascites fluid, and is more sensitive than conventional latex-bead based dipstick assays and much faster than ELISA-based isotyping assays. The kit requires only 0.5µL ascites fluid, 5 to 55µL of cell culture supernatant or 1.5ng of purified antibody.

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LightShift™ Chemiluminescent EMSA Kit (Thermo Scientific™)

The Thermo Scientific LightShift Chemiluminescent EMSA Kit is an extraordinarily robust and sensitive system for performing electrophoretic mobility shift assays (EMSA) to identify and characterize protein-DNA binding interactions. The kit includes reagents for setting up and customizing DNA binding reactions, a control set of DNA and protein extract to test the kit system, stabilized streptavidin-HRP conjugate to probe for the biotinlabeled DNA target, and an exceptionally sensitive chemiluminescent substrate module for detection.

Features of the LightShift Chemiluminescent EMSA Kit:

• Excellent for detecting low-abundance proteins in nuclear extracts
• Sensitivity that surpasses radioactive and digoxigenin methods
• Compatible with previously established binding conditions for popular DNA-protein interactions
• Includes EBNA control system to help new users develop a working assay and understand the methods used to confirm binding interaction specificity

The principle for LightShift EMSA Detection is similar to a Western blot. Biotin end-labeled duplex DNA is incubated with a nuclear extract or purified factor and electrophoresed on a native gel. The DNA is then rapidly (30 minutes) transferred to a positive nylon membrane, UV crosslinked, probed with streptavidin-HRP conjugate and incubated with the substrate. The protocol from labeling to results can be accomplished in a single day.

The interaction of proteins with DNA is central to the control of many cellular processes including DNA replication, recombination and repair, transcription, and viral assembly. One technique that is central to studying gene regulation and determining protein:DNA interactions is the electrophoretic mobility shift assay (EMSA).

The EMSA technique is based on the observation that protein:DNA complexes migrate more slowly than free DNA molecules when subjected to non-denaturing polyacrylamide or agarose gel electrophoresis. Because the rate of DNA migration is shifted or retarded upon protein binding, the assay is also referred to as a gel shift or gel retardation assay. Until conception of the EMSA protein:DNA interactions were studied primarily by nitrocellulose filter-binding assays.

All that is needed to perform the assay is purified DNA target that has been end-labeled with biotin, the protein extract to be tested, nylon membrane and basic electrophoresis equipment. DNA targets can be synthesized with 5' or 3' biotin labels or they can be labeled after synthesis using the Thermo Scientific Biotin 3' End DNA Labeling Kit (Product No. 89818). Nuclear, cytosolic or whole cell protein extracts can be obtained by a variety of methods, including the Thermo Scientific NE-PER Nuclear and Cytoplasmic Extraction Reagent Kit (Product No. 78833).

More Product Data
Transfer EMSA gels using the Pierce G2 Fast Blotter

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ProteinSEQ™ Protein A Quantitation Kit (Applied Biosystems™)

The ProteinSEQ™ Protein A Quantitation Kit contains all reagents and buffers needed for the PCR-based quantitation of Protein A leeched from Protein A purification columns. The kit utilizes TaqMan assay technology to deliver a quantitation method with the highest sensitivity and widest dynamic range of all methods currently available. The kit contains sufficient reagents for 200 reactions.

• Quantitate residual Protein A 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 protein process contaminants with extraordinary sensitivity and unparalleled dynamic range. Residual Protein A leeching from purification columns can be accurately measured from 2.56-8000 pg/mL, with outstanding quantitation efficiency and dilutional linearity.

Streamlined assay worflow
The ProteinSEQ Protein A Quantitation Kit is the only instrument platform-based Protein A 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.

What you get
The ProteinSEQ Protein A Quantitation Kit contains:
• Capture beads loaded with industry standard anti-Protein A antibody
• Protein A standards
• All reagents and buffers needed to enable PCR-based quantitation of Protein A

For a kit that does not include the capture beads and standards that may be used for customized Protein A measurements or for the quantitation of other purification ligands, please see the ProteinSEQ™ Protein A Core Kit (Cat. No. A28406).

Pierce™ Chromogenic Endotoxin Quant Kit (Thermo Scientific™)

The Thermo Scientific Pierce Chromogenic Endotoxin Quant Kit is a highly sensitive endpoint assay that accurately measures and detects endotoxin (lipopolysaccharide) in a protein, peptide, nucleic acid, or antibody sample using the amebocyte lysate assay. The kit enables detection within two linear sensitivity ranges of 0.01–0.1 EU/mL and 0.1–1.0 EU/mL.

Features and benefits of the Pierce Chromogenic Endotoxin Quant Kit include:
Highly sensitive with a broad range—detect as little as 0.01 EU/mL to 1 EU/mL
Specific—no interference from ß-glucans and suitable for wide range of samples, including protein, vaccine, plasmid, DNA, RNA
Fast—perform assay in as little as 20 minutes
End-point chromogenic assay—measure with a standard spectrophotometer or plate reader at 405–410 nm

The Pierce Chromogenic Endotoxin Quant Kit is an end-point chromogenic endotoxin detection assay based on the amebocyte lysate method, which measures endotoxin through the interaction of the endotoxin with the proenzyme Factor C found in circulating amebocytes of the horseshoe crab. The proteolytic activity of this proenzyme is activated in the presence of lipopolysaccharides (endotoxins) derived from the outer cell membrane of gram-negative bacteria such as E.coli. Endotoxin levels are determined by measuring the activity of Factor C in the presence of a synthetic peptide substrate that releases p-nitroaniline (pNA) after proteolysis, producing a yellow color that can be measured at an absorbance of 405 nm.

Endotoxin levels in the samples are accurately determined using the included endotoxin standard of known concentration that is derived from E.coli strain O111: B4. Determining endotoxin levels is important to assess the efficiency of endotoxin removal methods and prevent endotoxic shock, inflammation, and/or sepsis in tissue culture cells and animals injected with endotoxin-contaminated proteins.

Applications: quantitation of endotoxin levels in a protein, peptide, antibody, or nucleic acid samples

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Pierce High Capacity Endotoxin Removal Resin
Pierce High Capacity Endotoxin Removal Spin Columns

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

The Thermo Scientific Pierce Coomassie Plus Protein Assay is a ready-to-use, reducing agent-compatible, improved Bradford assay reagent to quickly measure (A595nm) total protein concentration compared to a protein standard.

The Pierce Coomassie Plus Assay Reagent is a single, ready-to-use solution for measuring protein concentration. Simply add the reagent to equal volumes of samples and standards, mix and then measure the absorbance at 595nm. The assay costs only pennies per sample and can be performed in either test tube or microplate format. The Pierce Coomassie Plus Assay Reagent provides increased linearity of response and only half the protein-to-protein variability of other commercial Bradford assay formulations.

Features of the Coomassie Plus Protein Assay:

Colorimetric—measure with a standard spectrophotometer or plate reader (595nm)
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
Better—improved linearity and response-uniformity compared to traditional Bradford formulations
Flexible—microplate and cuvette protocols provided with the instructions and adaptable to several target working ranges

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 465nm) to the blue form of the dye (absorbance maximum at 610nm). The difference between the two forms of the dye is greatest at 595nm, 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 575nm and 615nm. At the two extremes (575nm and 615nm) there is a loss of about 10% in the measured amount of color (absorbance) compared to that obtained at 595nm.

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. 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 595nm 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.

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Ampule Breakers

Pierce™ Detergent Compatible Bradford Assay Kit (Thermo Scientific™)

The Thermo Scientific™ Pierce™ Detergent Compatible Bradford Assay Kit is a quick and ready-to-use modification of the well-known Bradford coomassie dye-binding, colorimetric method for total protein quantitation. Proprietary additives to the Bradford Reagent make it compatible with up to 1% or higher of detergents and lysis reagents that are commonly used in life science research, including Triton® X-100 and NP-40.

• Convenient— detergent-free standard curve
• Flexible— compatible with samples both with and without detergent
• Minimal sample—requires only 10 µL for microplate procedure
• Colorimetric—measure with a standard spectrophotometer or plate reader (595 nm)
• Easy to use— single reagent, no working reagent preparation required
• Fast—10 minute incubation at room temperature
• Broad range—detects protein concentration in the ranges of 2 to 1500 µg/mL

Similar to the Bradford method, coomassie dye binds protein in an acidic medium causing an immediate shift in absorption maximum from 465 nm to 595 nm with a concomitant color change from green to blue. In addition, the assay is complete in just 10 minutes.

The protein assay can be performed in either test tube or microplate format. The standard working range is 100-1500 µg/mL with up to 1% detergent (or higher in some cases). Protein concentrations are estimated by reference to absorbances obtained for a series of standard protein dilutions, typically bovine serum albumin (BSA), which are assayed alongside the unknown samples. Because the color response with coomassie dye is non-linear with increasing protein concentration, a standard curve must be completed with each assay. Standards can be used directly without preparing them in the same detergent found in the test samples.

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Glycoprotein Standards Set for Pierce™ Glycoprotein Carbohydrate Estimation Kit (Thermo Scientific™)

The Thermo Scientific Pierce Glycoprotein Standards Set includes six purified standards (two negative and four positive controls) intended for use with any glycoprotein carbohydrate determination protocol.

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Pierce™ 660nm Protein Assay Kit (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 660nm Protein Assay can be performed in either a test tube or microplate format.

Features of the 660 nm Protein Assay Kit:

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 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. 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.

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ProQuest™ Two-Hybrid System with Gateway™ Technology (Invitrogen™)

The ProQuest™ Two-Hybrid System with Gateway® Technology is an in vivo yeast-based system for identifying interactions between two proteins. This interaction reconstitutes a functional transcription factor that activates chromosomally integrated reporter genes where transcriptional activation is monitored by the growth of cells on selective media.
The ProQuest™ System features:
• Gateway® Technology to allow rapid and easy generation of bait and prey constructs, and to facilitate downstream application
• Low copy-number DBD (DNA Binding Domain) and AD (Activation Domain) vectors (ARS/CEN) to control over-expression and increase reproducibility
• Three different reporter genes (HIS3, URA3, and lacZ) with independent promoter regions to rapidly weed out false positives. URA3 reporter gene allows for both positive and negative selection, enabling advanced two-hybrid techniques such as reverse two-hybrid.

• A set of strong-to-weak Gateway®-based control interactions to evaluate results and assess the strength of the interaction being tested

Pierce™ Bovine Serum Albumin Standard Ampules, 2 mg/mL (Thermo Scientific™)

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

Features of BSA Protein Assay Standards:

Convenient—1 mL ampules
Universal—recognized as the industry standard for protein quantitation in colorimetric 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 compared to an NIST reference

These bovine serum albumin (BSA) solutions are protein concentration reference standards for use in BCA, Bradford and other protein assay protocols. BSA is the universally accepted reference protein for total protein quantitation. The albumin standard is precisely formulated at 2 mg/mL in an ultrapure 0.9% sodium chloride (saline) solution. The concentration of the stock solution is calibrated by direct comparison to purified BSA (Fraction V) from the National Institute of Standards and Technology (NIST).

Applications:
• Protein assay quantitation standard (BCA Protein Assay, Coomassie-Bradford Assay, etc.)
• Protein recovery control for desalting and other column procedures
• 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 a standard is a purified, known concentration of the most abundant protein contained in the samples being tested. Often, a highly purified, known concentration of the protein of interest is not available or it is too expensive to use as the standard, or the sample itself is a mixture of many proteins (e.g., cell lysate). In such cases, the best standard is one that will produce a normal (i.e., average) color response curve with the selected protein assay method and is readily available to any researcher. BSA is such a protein, and the Pierce Albumin Standards are the most convenient source of ready-to-use BSA standard.

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.

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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™ Phosphoprotein Phosphate Estimation Assay Kit (Thermo Scientific™)

The Thermo Scientific Phosphoprotein Phosphate Estimation Kit enables classification and identification of proteins as phosphorylated (serine and threonine), as well as semi-quantitative assessment of the phosphorylation level.

Features of the Phosphoprotein Phosphate Estimation Kit:

Specific—measures phosphoserine (p-Ser) and phosphothreonine (p-Thr) only; does not measure phosphotyrosine (p-Tyr)
Convenient—test tube and 96-well microplate protocols included and require less than 90 minutes to perform
Semi-quantitative—calculate moles of phosphate (P) per mole of protein using the included phosvitin standard
Customizable—format is adaptable to development of specific assays for pure phosphoproteins when previously characterized standards are available

The Phosphoprotein Phosphate Estimation Assay Kit is designed to aid in characterization of the status and extent of phosphorylation of purified protein samples. The assay is based on the alkaline hydrolysis of phosphate from seryl and threonyl residues in phosphoproteins and quantification of the released phosphate with malachite green and ammonium molybdate. The assay is easily performed in 96-well microplates or test tubes and is completed in about one hour.

Applications:
• Identify proteins as containing phosphoserine or phosphothreonine phosphorylations
• Estimate the amount of pS and pT phosphorylation
• Develop specific quantitative assays for well-characterized phosphoproteins of interest

The assay can be used to identify whether a purified protein contains either phospho-serine (p-Ser) or phospho-threonine (p-Thr) as well as to estimate the level of this type of phosphorylation. For quantitation, the test protein sample is compared with specific concentrations of phosvitin, a phosphoprotein of known phosphorylation level. The alkaline hydrolysis step does not release phosphate from phospho-tyrosine (p-Tyr) residues in peptide linkage. Therefore, a negative result for an unknown purified protein preparation indicates that the protein is either (1) not a phosphoprotein or (2) is phosphorylated exclusively at tyrosine residues. In the latter case, Western blot analysis using an anti-phosphotyrosine antibody will be necessary to distinguish between these two possibilities.