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CBA034 STAT1 ELISA Kit

STAT1 ELISA Kit MSDS (material safety data sheet) or SDS, CoA and CoQ, dossiers, brochures and other available documents.
CBA034
  
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Overview

Replacement Information
Description
OverviewDetects and quantifies the level of STAT1 protein independent of its phosphorylation state. STAT1 is a member of STAT family of proteins which exists in a latent state in the cytoplasm and is directly activated in response to stimulation by interferons-α and -γ. It participates in the regulation of cytokine-signaling and cellular responses and plays an important role in the growth and differentiation of a variety of cell types. This kit is designed for use with human cells and tissues.
Catalogue NumberCBA034
Brand Family Calbiochem®
Application Data
Materials Required but Not Delivered• 96 well plate reader capable of measurement at or near 450 nm. • Calibrated adjustable precision pipettes, preferably with disposable plastic tips. (A manifold multi channel pipette is desirable for large assays.) • Cell Lysis Buffer. • Deionized or distilled H2O. • Plate washer: automated or manual (squirt bottle, manifold dispenser, etc.). • Graph paper: linear (Cartesian), log log, or semi log, as desired. • Glass or plastic tubes for diluting and aliquoting standard. • Absorbent paper towels. • Calibrated beakers and graduated cylinders in various sizes
References
ReferencesBoudny, V. and J. Kovarik 2002. Neoplasm 49, 349. Brivanlou, A.H. and J.E. Darnell, 2002. Science 295, 813. Bromberg, J. 2002. J. Clin. Invest. 109, 1139. Levy, D.E. and J.E. Darnell 2002. Nat. Rev. Mol. Cell. Biol. 3, 651. Ghislain, J.J., et al. 2001. Interferon Cytokine Res. 21, 379. Shankaran, V. and R.D. Shreiber 2001. In Cytokine Reference. Volume 2: Receptors. J.J. Oppenheim, M. Feldmann, S.K. Durum, T. Hirano, J. Vilcek, and N.A. Nicola, editors. Academic Press, London, UK. pp.1819. Stephens, J.M., et al. 1998. J. Biol. Chem. 273, 31408.
Product Information
Detection methodColorimetric
Form96 Tests
Format96-well plate
Kit containsSTAT1 Standard, Standard Diluent Buffer, STAT1 Antibody-Coated 96-Well Plate, Rabbit Anti-STAT1 (pSer218/222) Detector Antibody, Anti-Rabbit IgG-HRP Concentrate, Sample Treatment Buffer, HRP Diluent, Wash Buffer Concentrate, Soluble Substrate (TMB), Stop Solution, Plate Covers, and a user protocol.
Applications
Biological Information
Assay range0.3-20 ng/ml
Assay time4 h
Sample TypeCells
Physicochemical Information
Sensitivity<0.27 ng/ml
Dimensions
Materials Information
Toxicological Information
Safety Information according to GHS
Safety Information
Product Usage Statements
Intended useThe Calbiochem® STAT1 ELISA Kit is designed to detect and quantify the level of STAT1 protein independent of its phosphorylation state. This assay is intended for the detection of STAT1 from lysates of human cells or tissues. This kit does not cross react with STAT1 from mouse or rat cells. This kit can be used to normalize the phosphorylated STAT1 content of the samples when using the PhosphoDetect™ STAT1 (pTyr⁷⁰¹) ELISA Kit (Cat. No. CBA035)
Storage and Shipping Information
Ship Code Blue Ice Only
Toxicity Multiple Toxicity Values, refer to MSDS
Storage +2°C to +8°C
Storage ConditionsUpon arrival store the entire contents of the kit at 4°C.
Do not freeze Ok to freeze
Packaging Information
Transport Information
Supplemental Information
Kit containsSTAT1 Standard, Standard Diluent Buffer, STAT1 Antibody-Coated 96-Well Plate, Rabbit Anti-STAT1 (pSer218/222) Detector Antibody, Anti-Rabbit IgG-HRP Concentrate, Sample Treatment Buffer, HRP Diluent, Wash Buffer Concentrate, Soluble Substrate (TMB), Stop Solution, Plate Covers, and a user protocol.
Specifications
Global Trade Item Number
Catalogue Number GTIN
CBA034 0

Documentation

STAT1 ELISA Kit Certificates of Analysis

TitleLot Number
CBA034

References

Reference overview
Boudny, V. and J. Kovarik 2002. Neoplasm 49, 349. Brivanlou, A.H. and J.E. Darnell, 2002. Science 295, 813. Bromberg, J. 2002. J. Clin. Invest. 109, 1139. Levy, D.E. and J.E. Darnell 2002. Nat. Rev. Mol. Cell. Biol. 3, 651. Ghislain, J.J., et al. 2001. Interferon Cytokine Res. 21, 379. Shankaran, V. and R.D. Shreiber 2001. In Cytokine Reference. Volume 2: Receptors. J.J. Oppenheim, M. Feldmann, S.K. Durum, T. Hirano, J. Vilcek, and N.A. Nicola, editors. Academic Press, London, UK. pp.1819. Stephens, J.M., et al. 1998. J. Biol. Chem. 273, 31408.
User Protocol

Revision20-October-2008 RFH
Form96 Tests
Format96-well plate
Detection methodColorimetric
Specieshuman, not mouse, not rat
StorageUpon arrival store the entire contents of the kit at 4°C.
Intended useThe Calbiochem® STAT1 ELISA Kit is designed to detect and quantify the level of STAT1 protein independent of its phosphorylation state. This assay is intended for the detection of STAT1 from lysates of human cells or tissues. This kit does not cross react with STAT1 from mouse or rat cells. This kit can be used to normalize the phosphorylated STAT1 content of the samples when using the PhosphoDetect™ STAT1 (pTyr⁷⁰¹) ELISA Kit (Cat. No. CBA035)
BackgroundSTAT1 is a member of the STAT family of proteins, which is comprised of STATs 1, 2, 3, 4, 5A, 5B, and 6. STAT homologs have also been described in Drosophila sp. and Dictyostellium discoidium. STAT family members are characterized by the presence of a DNA binding domain, an SH3 domain that mediates interaction with polyproline-containing proteins, an SH2 domain that mediates interaction with phosphotyrosine-containing proteins, and a C terminal transactivation (TAD) domain. STAT proteins control the transcription of specific genes in response to cytokine stimulation. Alternative splicing yields two STAT1 isoforms, designated STAT1α and STAT1β, with MW=91 kDa and 84 kDa, respectively, which differ at their C termini. As with all members of the STAT family, STAT1 exists in a latent state in the cytoplasm, and is activated and translocated to the nucleus in response to stimulation. Stimuli that activate STAT1 include interferons-α and -γ, IL-6 family members including oncostatin M and LIF, as well as other cytokines, and the growth factor PDGF. The series of events leading to STAT1 activation arising from interferon-γ stimulation is best characterized. The interferon-γ receptor is composed of two IFNGR1 subunits and two IFNGR2 subunits that are localized at the plasma membrane as monomers prior to stimulation. Each IFNGR1 subunit has a constitutively associated JAK1, while each IFNGR2 has a constitutively associated JAK2. Upon interferon-γ-stimulation, the dimeric ligand binds and dimerizes IFNGR1 subunits, which in turn recruit two IFNGR2 subunits through their extracellular domains. This association allows JAK1 and JAK2 to interact. The interacting JAK proteins transactivate one another by reciprocal tyrosine phosphorylation, and phosphorylate tyrosine 440 of the two IFNGR1 subunits contained in the receptor complex. These phosphorylated tyrosine residues on the IFNGR1 subunits provide paired docking sites for STAT1 via its SH2 domain. STAT1, recruited to the receptor complex, is then phosphorylated at tyrosine residue 701 by the JAKs. This tyrosine phosphorylation promotes STAT1 homo- and heterodimerization mediated by reciprocal phosphotyrosine-SH2 domain interaction and the dissociation of the dimers from the receptor complex. Activated STAT1 is then phosphorylated at serine 727 by an activity with MAPK-like properties, and is translocated to the cell nucleus. STAT1 nuclear transport is GTP-dependent and involves STAT1 interaction with the protein importin. Once in the nucleus, STAT1-containing dimers complex with other nuclear proteins including p48, CBP, and p300. The STAT1-containing complexes regulate gene expression, either through interaction with the consensus DNA sequence TTCC(C or G)GAA (the GAS element [interferon-γ-activated sequence]) located in the promoter regions of target genes, or through interacting with the interferon-stimulated response element (ISRE). Genes that are upregulated in response to interferon-γ through STAT1 signaling are denoted immediate-early genes, and include those for the transcription factor IRF-1, the type I Fcγ receptor, and guanylate binding protein 1. STAT1 activation of gene transcription is usually transient, being completed in about 15 min. A second wave of transcription, observed 6-8 hours following STAT1 activation, produces intermediate gene transcripts by a process which requires additional protein synthesis. Intermediate genes include those for MHC class I and II. STAT1 is currently under investigation in many diverse areas of research including host responses to viral and bacterial infection, immune cell differentiation, and cell growth. STAT1 mediates apoptotic signals arising from interferon-γ stimulation, and may modulate anti-apoptotic signaling arising from NF-κB. STAT1 is also of interest in cancer studies, as this protein is constitutively activated in many tumors, including those of the breast, ovary, lung, head and neck, and in acute myeloid leukemia and erythroleukemia.
Principles of the assayThe Calbiochem® STAT1 ELISA Kit is a solid phase sandwich Enzyme Linked-Immuno-Sorbent Assay (ELISA). A monoclonal antibody specific for STAT1 (regardless of phosphorylation state) has been coated onto the wells of the strips provided. Samples, including a standard containing STAT1, control specimens, and unknowns, are pipetted into these wells. During the first incubation, the STAT1 antigen binds to the immobilized (capture) antibody. After washing, a rabbit antibody specific for total STAT1 is added to the wells. During the second incubation, this antibody serves as a detection antibody by binding to the immobilized STAT1 protein captured during the first incubation. After removal of excess detection antibody, a horseradish peroxidase-labeled anti-rabbit IgG (anti-rabbit IgG-HRP) is added. This binds to the detection antibody to complete the four-member sandwich. After a third incubation and washing to remove all the excess anti-rabbit IgG-HRP, a substrate solution is added, which is acted upon by the bound enzyme to produce color. The intensity of this colored product is directly proportional to the concentration of STAT1 present in the original specimen.
Materials provided• STAT1 Standard (Kit Component No. JA8063-1EA): Recombinant protein prepared in E. coli. Refer to vial label for quantity and reconstitution volume • Standard Diluent Buffer (Kit Component No. JA8064-25ML): 1 bottle, 25 ml per bottle, Contains 15 mM sodium azide • STAT1 Antibody-Coated 96-Wells Plate (Kit Component No. JA8065-1EA): 1 plate, 96 wells per plate • Rabbit Anti-STAT1 (pSer218/222) Detector Antibody (Kit Component No. JA8066-11ML): 1 bottle, 5.5 ml per bottle, Contains 15 mM sodium azide • Goat Anti-Rabbit IgG-Horseradish Peroxidase (HRP) Concentrate (Kit Component No. JA8067-125UL): 1 vial, (100X), 125 µl per vial, Contains 3.3 mM thymol • Sample Treatment Buffer (Kit Component No. JA8068-10ML): 1 bottle, 10 ml per bottle • HRP Diluent (Kit Component No. JA8069-25ML): 1 bottle, 25 ml per bottle, Contains 3.3 mM thymol • Wash Buffer Concentrate (Kit Component No. JA8070-100ML): 1 bottle, (25X), 100 ml per bottle • Soluble Substrate (Kit Component No. JA8071-25ML): 1 bottle, 25 ml per bottle, Tetramethylbenzidine (TMB) • Stop Solution (Kit Component No. JA8072-25ML): 1 bottle, 25 ml per bottle • Plate Sealers (Kit Component No. JA8073-1EA): 3 adhesive strips
Materials Required but not provided• 96 well plate reader capable of measurement at or near 450 nm. • Calibrated adjustable precision pipettes, preferably with disposable plastic tips. (A manifold multi channel pipette is desirable for large assays.) • Cell Lysis Buffer. • Deionized or distilled H2O. • Plate washer: automated or manual (squirt bottle, manifold dispenser, etc.). • Graph paper: linear (Cartesian), log log, or semi log, as desired. • Glass or plastic tubes for diluting and aliquoting standard. • Absorbent paper towels. • Calibrated beakers and graduated cylinders in various sizes
Precautions and recommendations• Disposal Note: This kit contains materials with small quantities of sodium azide. Sodium azide reacts with lead and copper plumbing to form explosive metal azides. Upon disposal, flush drains with a large volume of water to prevent azide accumulation. Avoid ingestion and contact with eyes, skin and mucous membranes. In case of contact, rinse affected area with plenty of water. Observe all federal, state and local regulations for disposal. • When not in use, kit components should be refrigerated. All reagents should be warmed to room temperature before use. • Plates should be allowed to come to room temperature before opening the foil bags. Once the desired number of strips has been removed, immediately reseal the bag and store at 4°C to maintain plate integrity. • Samples should be frozen if not analyzed shortly after collection. Avoid multiple freeze thaw cycles of frozen samples. Thaw completely and mix well prior to analysis. • If particulate matter is present, centrifuge or filter prior to analysis. • All standards, controls and samples should be run in duplicate. • Samples that are greater than the highest standard point should be diluted with Standard Diluent Buffer and retested. • When pipetting reagents, maintain a consistent order of addition from well to well. This ensures equal incubation times for all wells. • Cover or cap all reagents when not in use. • Do not mix or interchange different reagent lots from various kit lots. • Do not use reagents after the kit expiration date. • Read absorbances within 2 h of assay completion. • In house controls should be run with every assay. If control values fall outside pre established ranges, the accuracy of the assay is suspect. • All residual wash liquid must be drained from the wells by efficient aspiration or by decantation followed by tapping the plate forcefully on absorbent paper. Never insert absorbent paper directly into the wells. • Because Soluble Substrate is light sensitive, avoid prolonged exposure to light. Also avoid contact between Soluble Substrate and metal, or color may develop. • Safety All blood components and biological materials should be handled as potentially hazardous. Follow universal precautions as established by the Centers for Disease Control and Prevention and by the Occupational Safety and Health Administration when handling and disposing of infectious agents. • Guidelines for Washing: Incomplete washing will adversely affect the results. All washing must be performed with Wash Buffer Concentrate provided. Washing can be performed manually as follows: completely aspirate the liquid from all wells by gently lowering an aspiration tip (aspiration device) into the bottom of each well. Take care not to scratch the inside of the well. After aspiration, fill the wells with at least 0.4 ml Diluted Wash Buffer. Let soak for 15 to 30 s and aspirate the liquid. Repeat as directed in the Detailed Protocol. Following the final wash, the plate should be inverted and tapped dry on absorbent tissue. Alternatively, the Diluted Wash Buffer may be put into a squirt bottle. If a squirt bottle is used, flood the plate with Diluted Wash Buffer, completely filling all wells. Following the final wash, the plate should be inverted and tapped dry on absorbent tissue. If using an automated washer, the operating instructions for washing equipment should be carefully followed. If your automated washer allows, 30 s soak cycles should be programmed into the wash cycle.
Preparation• Cell Lysis Buffer: • 10 mM Tris, pH 7.4 • 100 mM NaCl • 1 mM EDTA • 1 mM EGTA • 1 mM NaF • 20 mM Na4P2O7 • 2 mM Na3VO4 • 1% Triton® X 100 detergent • 10% glycerol • 0.1% SDS • 0.5% deoxycholate • 1 mM PMSF (stock is 0.3 M in DMSO) • Protease Inhibitor Cocktail Set III (Cat. No. 539134) This buffer is stable for 2-3 weeks at 4°C or for up to 6 months when aliquoted (without protease inhibitors and PMSF added) and stored at 20°C. When stored frozen, the Cell Lysis Buffer should be thawed on ice. Important: add the protease inhibitors just before using. The stability of protease inhibitor supplemented Cell Lysis Buffer is 24 h at 4°C. PMSF is very unstable and must be added prior to use, even if added previously. • Preparation of Cell Lysates: This protocol has been successfully applied to several cell lines. Researchers should optimize the cell lysis procedures for their own applications. 1. Collect cells in PBS by centrifugation (non-adherent) or scraping from culture flasks (adherent). 2. Wash cells twice with cold PBS. 3. Remove and discard the supernatant and collect the cell pellet. (At this point the cell pellet can be frozen at -80°C and lysed at a later date). 4. Lyse the cell pellet in Cell Lysis Buffer for 30 min, on ice, with vortexing at 10 min intervals. The volume of Cell Lysis Buffer depends on the cell number in cell pellet and expression of STAT1. For example, 107 HeLa cells grown in DMEM plus 10% FBS can be extracted in 1 ml of Cell Lysis Buffer. Under these conditions, use of 1-10 µl of the clarified cell lysate diluted to a volume of 100 µl/well in Standard Diluent Buffer (See Detailed protocol) is sufficient for the detection of STAT1. 5. Transfer extract to microcentrifuge tubes and centrifuge at 13,000 rpm for 10 min at 4°C. 6. Aliquot the clear lysate to clean microfuge tubes. These samples are ready for assay. Lysates can be stored at -80°C. Avoid multiple freeze/thaw cycles. • Sample Pre-Treatment: Incubate each sample and control with an equal volume of Sample Treatment Buffer on ice for 20 min. Dilute this mixture at least 5-fold in Standard Diluent Buffer. For example, for duplicate analyses, add 25 µl sample and 25 µl Sample Treatment Buffer, then after incubation, add 200 µl Standard Diluent Buffer. The dilution chosen should be optimized for each experimental system.
Reagent preparation• Reconstitution and Dilution of Human STAT1 Standard: Note: This STAT1 standard is calibrated against the mass of a purified, full length, recombinant STAT1 protein. 1. Reconstitute STAT1 Standard with Standard Diluent Buffer. Refer to standard vial label for instructions. Swirl or mix gently and allow to sit for 10 min to ensure complete reconstitution. Label as 20 ng/ml STAT1. Use the standard within 1 h of reconstitution. 2. Add 0.25 ml of Standard Diluent Buffer to each of 6 tubes labeled 10, 5, 2.5, 1.25, 0.625 and 0.313 ng/ml STAT1. 3. Make serial dilutions of the standard as described in the following dilution table. Mix thoroughly between steps.

Table 1: B. Dilution of Human STAT1 Standard

Remaining reconstituted standard should be discarded or frozen at 80°C for further use. Standard can be frozen and thawed one time only without loss of immunoreactivity.

• Storage and Final Dilution of Anti Rabbit IgG Horseradish Peroxidase (HRP): Please Note: The Anti Rabbit IgG HRP Concentrate is in 50% glycerol. This solution is viscous. To ensure accurate dilution, allow Anti Rabbit IgG HRP Concentrate to reach room temperature. Gently mix. Pipette Anti Rabbit IgG HRP Concentrate slowly. Remove excess concentrate solution from pipette tip by gently wiping with clean absorbent paper. 1. Within 1 h of use, dilute 10 µl of this 100X concentrated solution with 1 ml of HRP Diluent for each 8 well strip used in the assay. Label as Anti Rabbit IgG HRP Working Solution.

Table 2: Storage and Final Dilution of Anti Rabbit IgG Horseradish Peroxidase (HRP)

2. Return the unused Anti rabbit IgG HRP concentrate to the refrigerator. • Dilution of Wash Buffer: Allow the 25X concentrate to reach room temperature and mix to ensure that any precipitated salts have redissolved. Dilute 1 volume of the Wash Buffer Concentrate with 24 volumes of deionized water (e.g., 50 ml may be diluted up to 1.25 liters, 100 ml may be diluted up to 2.5 liters). Label as Working Wash Buffer. Store both the concentrate and the Working Wash Buffer in the refrigerator. The diluted buffer should be used within 14 days.
Detailed protocolBe sure to read the Precautions and Recommendations section before carrying out the assay. Allow all reagents to reach room temperature before use. Gently mix all liquid reagents prior to use. Note: A standard curve must be run with each assay. 1. Determine the number of 8 well strips needed for the assay. Insert these in the frame(s) for current use. (Re bag extra strips and frame. Store these in the refrigerator for future use.) 2. Add 100 µl of the Standard Diluent Buffer to zero wells. Well(s) reserved for chromogen blank should be left empty. 3. Add 100 µl of standards, samples or controls to the appropriate wells. Samples prepared in Cell Lysis Buffer must be diluted 1:100 or greater in Standard Diluent Buffer (for example, 1 ml sample into 99 ml buffer). While a 1:100 sample dilution has been found to be satisfactory, higher dilutions such as 1:200 may be optimal. The dilution chosen should be optimized for each experimental system. Tap gently on side of plate to thoroughly mix. 4. Cover wells with a Plate Sealer and incubate for 2 h at room temperature. 5. Thoroughly aspirate or decant solution from wells and discard the liquid. Wash wells 4 times. See Directions for Washing. 6. Pipette 100 µl of rabbit Anti-STAT1 Detector Antibody to each well except the chromogen blank(s). Tap gently on the side of the plate to mix. 7. Cover wells with a Plate Sealer and incubate for 1 h at room temperature. 8. Thoroughly aspirate or decant solution from wells and discard the liquid. Wash wells 4 times. See Directions for Washing. 9. Add 100 µl Anti Rabbit IgG HRP Working Solution to each well except the chromogen blank(s). 10. Cover wells with a Plate Sealer and incubate for 30 min at room temperature. 11. Thoroughly aspirate or decant solution from wells and discard the liquid. Wash wells 4 times. See Directions for Washing. 12. Add 100 µl Soluble Substrate to each well. The liquid in the wells will begin to turn blue. 13. Incubate for 30 min at room temperature and in the dark. Please Note: Do not cover the plate with aluminum foil or metalized mylar. The incubation time for Soluble Substrate is often determined by the plate reader used. Many plate readers have the capacity to record a maximum (Abs) of 2.0. The absorbance values should be monitored and the substrate reaction stopped before the absorbance of the positive wells exceed the limits of the instrument. The absorbance values at 450 nm can only be read after the Stop Solution has been added to each well. If using a reader that records only to 2.0 Abs units, stopping the assay after 20 to 25 min is suggested. 14. Add 100 µl Stop Solution to each well. Tap side of plate gently to mix. The solution in the wells should change from blue to yellow. 15. Read the absorbance of each well at 450 nm having blanked the plate reader against a chromogen blank composed of 100 µl each of Soluble Substrate and Stop Solution. Read the plate within 2 h after adding the Stop Solution. 16. Plot on graph paper the absorbance of the standards against the standard concentration. (Optimally, the background absorbance may be subtracted from all data points, including standards, unknowns and controls, prior to plotting.) Draw the best smooth curve through these points to construct the standard curve. If using curve fitting software, the four parameter algorithm provides the best curve fit. 17. Read the STAT1 concentrations for unknown samples and controls from the standard curve plotted in step 16. Multiply value(s) obtained for sample(s) by dilution factor to correct for the dilution in step 3. (Samples producing signals higher than the highest standard (100 Units/ml) should be further diluted in Standard Diluent Buffer and reanalyzed, multiplying the concentration by the appropriate dilution factor.)
Standard curve

Table 3: Typical Data Obtained with STAT1 Standard

Example data obtained for the various standards over the range of 0 to 20 ng/ml STAT1.
Limitations of the assayDo not extrapolate the standard curve beyond the 20 ng/ml standard point; the dose-response is non-linear in this region and accuracy is difficult to obtain. Dilute samples >20 ng/ml with Standard Diluent Buffer; re-analyze these and multiply results by the appropriate dilution factor. The influence of various lysis buffers has not been thoroughly investigated. The rate of degradation of native STAT1 in various matrices has not been investigated. Although STAT1 degradation in the Cell Lysis Buffer described in this protocol has not been seen to date, the possibility of this occurrence cannot be excluded.
Sensitivity<0.27 ng/ml
Sensitivity NotesThe analytical sensitivity of this assay is <0.27 ng/ml of STAT1. This was determined by adding two standard deviations to the mean absorbance obtained when the zero standard was assayed 30 times. The sensitivity of this ELISA was compared to immunoblotting using known quantities of STAT1. The data presented in Figure 1 show that the sensitivity of the ELISA is approximately 4x greater than that of immunoblotting. The bands shown in the immunoblotting data were developed using an anti-STAT1 antibody and chemiluminescent detection.

Figure 1: Sensitivity
Assay Range0.3-20 ng/ml
Precision

Table 4: Intra Assay Precision

Samples of known STAT1 concentration were assayed in replicates of 16 to determine precision within an assay.

Table 5: Inter Assay Precision

Samples were assayed 36 times in multiple assays to determine precision between assays.
RecoveryTo evaluate recovery, STAT1 Standard was spiked at 3 different concentrations into 10% Cell Lysis Buffer. The average recovery was 99%.
ParallelismNatural STAT1 from HeLa cell lysate was serially diluted in Standard Diluent Buffer. The absorbance of each dilution was plotted against the STAT1 standard curve. Parallelism demonstrated by the figure below indicates that the standard accurately reflects STAT1 content in samples.

Figure 2: Parallelism

Natural STAT1 from HeLa cell lysate was serially diluted in Standard Diluent Buffer. The absorbance of each dilution was plotted against the STAT1 standard curve. Parallelism demonstrated by the figure above indicates that the standard accurately reflects STAT1 content in samples.
LinearityHeLa cells were grown in tissue culture medium containing 10% fetal calf serum and lysed with Cell Lysis Buffer. This lysate was diluted in Standard Diluent Buffer over the range of the assay and measured for STAT1 content. Linear regression analysis of sample values versus the expected concentration yielded a correlation coefficient of 0.99.

Table 6: Linearity of Dilution

HeLa cells were grown in tissue culture medium containing 10% fetal calf serum and lysed with Cell Lysis Buffer. This lysate was diluted in Standard Diluent Buffer over the range of the assay and measured for STAT1 content. Linear regression analysis of sample values versus the expected concentration yielded a correlation coefficient of 0.99.
SpecificityThis ELISA recognizes STAT1 of human origin and does not cross-react with mouse or rat STAT1. This assay recognizes both α and β isoforms of STAT1. The STAT1 ELISA is specific for the measurement of total STAT1 protein.

Figure 3: Specificity

To determine the specificity of this ELISA kit, cell lysates from different cell lines, each at a concentration of 100 µg/ml total protein, were analyzed. The data presented shows that the kit detects STAT1 protein in cell lysates from human Jurkat, HeLa, 293, and HT1080 cells. The levels of STAT1 protein detected with this ELISA kit are consistent with results obtained by immunoblot analysis (inset in graph).
Registered TrademarksCalbiochem® is a registered trademark of EMD Chemicals, Inc. Triton® is a registered trademark of Dow Chemical Company PhosphoDetect™ and Interactive Pathways™ are trademarks of EMD Chemicals, Inc.