ESR1 (Ab-167) Antibody
Description
Introduction to ESR1 and its Significance
Estrogen receptor alpha (ESR1) is a ligand-activated transcription factor encoded by the ESR1 gene, playing a critical role in sexual development and reproductive function. Beyond reproduction, ESR1 serves essential functions in other tissues such as bone. The protein localizes to the nucleus where it may form homodimers or heterodimers with estrogen receptor 2 . As a nuclear hormone receptor, ESR1 is involved in the regulation of eukaryotic gene expression and affects cellular proliferation and differentiation in target tissues .
The significance of ESR1 extends to pathological conditions, particularly in breast cancer where over 70% of cases are ESR1-positive at diagnosis. Estrogen mediates its effects by binding to ESR1, leading to expression of genes controlling proliferation and cell survival . The clinical importance of ESR1 is underscored by the fact that patients with ESR1-positive breast cancer are typically treated with endocrine agents such as tamoxifen, aromatase inhibitors, or fulvestrant, which impede ESR1-signaling .
Recent research has highlighted the emergence of ESR1 mutations as a mechanism of resistance to endocrine therapy, particularly in metastatic settings. These mutations show increased prevalence in metastatic, endocrine-resistant breast cancer cases . Notably, ESR1 mutations are rarely detectable at diagnosis but are present in 30% to 40% of advanced breast cancer cases after treatment, making the timeline of testing crucial .
Definition and Target Specificity
The ESR1 (Ab-167) Antibody is a polyclonal antibody raised against synthetic peptide sequences derived from the human estrogen receptor alpha protein, specifically targeting the region around amino acids 165-169 with the sequence LASTN . This antibody is designed to recognize and bind to this specific epitope of the ESR1 protein, allowing for its detection in various experimental settings.
There are also phospho-specific variants of this antibody that recognize ESR1 when phosphorylated at serine 167 (LASTN where S is phosphorylated) . These phospho-specific antibodies are particularly valuable for studying the phosphorylation status of ESR1, which is known to regulate its activity.
Physical and Biochemical Properties
The ESR1 (Ab-167) Antibody is produced in rabbits as host animals, resulting in a rabbit polyclonal IgG antibody . It is typically supplied in liquid form at concentrations of approximately 1.0 mg/mL in phosphate buffered saline without Mg²⁺ and Ca²⁺, at pH 7.4, with 150mM NaCl, 0.02% sodium azide and 50% glycerol as preservatives .
The target protein, ESR1, has a predicted molecular weight of approximately 66-67 kDa, which is the size recognized by this antibody in Western blot applications . The antibody is designed to detect endogenous levels of ESR1 in human and mouse samples .
Production and Purification Methods
The ESR1 (Ab-167) Antibody is produced by immunizing rabbits with a synthetic peptide corresponding to the region around amino acids 165-169 (LASTN) of human ESR1 . For phospho-specific variants, the immunogen consists of a phosphopeptide derived from human estrogen receptor alpha around the phosphorylation site of serine 167 .
The antibody is typically affinity-purified from rabbit antiserum using epitope-specific peptides . In the case of phospho-specific antibodies, a two-step purification process is employed where the antibody is first purified using the phospho-peptide, and then antibodies that might recognize the non-phosphorylated form are removed using corresponding non-phosphopeptides .
Recommended Applications and Dilutions
The ESR1 (Ab-167) Antibody has been validated for multiple research applications, making it a versatile tool for studying estrogen receptor alpha. The following table outlines the recommended applications and dilution ranges:
| Application | Recommended Dilution Range |
|---|---|
| Western Blot (WB) | 1:500 - 1:1000 |
| Immunohistochemistry (IHC) | 1:50 - 1:200 |
| Immunofluorescence (IF) | 1:100 - 1:200 |
| ELISA | 0.01 - 0.1 μg/mL |
| Immunoprecipitation | 2 - 5 μg/mL |
Table 2: Recommended Applications and Dilutions for ESR1 (Ab-167) Antibody
The optimal working dilution should be determined by the end user, as it may vary depending on the specific experimental conditions and sample characteristics .
Experimental Validation
The antibody has been experimentally validated in several applications, as evidenced by the search results. These include:
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Western blot analysis of MCF cells using ESR1 (Ab-167) antibody, demonstrating specific detection of the ESR1 protein .
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Immunohistochemical staining of human breast carcinoma tissue showing ESR1 expression patterns .
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Immunofluorescence analysis of MCF cells revealing subcellular localization of ESR1 .
These validations confirm the antibody's specificity and utility in detecting ESR1 in various experimental contexts.
Role in Breast Cancer Research
The ESR1 (Ab-167) Antibody serves as a valuable tool in breast cancer research, particularly in studies investigating endocrine resistance mechanisms. As mentioned earlier, ESR1 mutations have emerged as important factors in resistance to endocrine therapy in breast cancer patients .
Recent studies have discovered naturally occurring ESR1 mutations, specifically Y537S and Y537C, in cell lines that have acquired resistance to long-term estrogen deprivation and fulvestrant . These mutations impact ESR1 binding to the genome and alter the ESR1 interactome, highlighting their functional consequences in endocrine resistance .
By using ESR1 (Ab-167) Antibody and its phospho-specific variants, researchers can detect and study changes in ESR1 expression, localization, and post-translational modifications (particularly phosphorylation) in response to various treatments or in different cancer models. This contributes to a better understanding of the molecular mechanisms underlying endocrine resistance.
Emerging Applications in Liquid Biopsy
The growing interest in liquid biopsy for detecting ESR1 mutations presents another area where ESR1 antibodies may play an indirect but important role. While the antibody itself is not used in liquid biopsy (which typically analyzes circulating cell-free DNA), research on ESR1 often combines multiple approaches, including antibody-based detection methods and genetic analyses .
The detection of ESR1 mutations in liquid biopsies has recently been recommended for ER-positive, HER2-negative advanced breast cancer, representing an innovative way to personalize endocrine therapy through the surveillance of ESR1 mutations throughout the disease course .
Research Limitations and Considerations
When using the ESR1 (Ab-167) Antibody, researchers should be aware of certain limitations and considerations. As with any polyclonal antibody, there may be batch-to-batch variations that could affect specificity and sensitivity . Additionally, the optimal working dilutions should be determined empirically for each application and experimental system .
Product Specs
Target Background
- Estrogen-induced miR-191 was identified as a direct upstream regulator of DAB2 in ER-positive breast cancer cells. PMID: 29247596
- The whole-genome insights carried in this work can help fully understand the biological roles of ER1 in breast cancer. PMID: 30301189
- There was a relationship between rs2046210 and rs3803662, and the risk of developing breast cancer in Vietnamese women. The A allele is the risk allele for both rs2046210 (OR [95% CI] = 1.43 [1.14 - 1.78], P = 0.0015) and rs3803662 (OR [95% CI] = 1.45 [1.16 - 1.83], P = 0.001). We conclude that two polymorphisms, rs2046210 in ESR1 and rs3803662 in TNRC9, are associated with breast cancer risk in the Vietnamese population. PMID: 30078824
- This study demonstrates that Estrogen receptor alpha can enhance the odonto/osteogenic differentiation of stem cells from apical papilla via ERK and JNK MAPK pathways. PMID: 30069950
- No association between polymorphisms in genes encoding estrogen receptors (ESR1 and ESR2) and excreted BPA levels was found in orthodontic patients after bracket bonding. PMID: 29961922
- Analysis of the genome-wide ER binding sites identified mutant ER unique recruitment mediating the allele-specific transcriptional program. PMID: 29438694
- This study describes RNF8 as a co-activator of ERalpha, which increases ERalpha stability via a post-transcriptional pathway, and provides new insights into the mechanisms by which RNF8 promotes cell growth in ERalpha-positive breast cancer. PMID: 28216286
- Reduced expression of ERbeta1 in female ERalpha-negative papillary thyroid carcinoma patients is associated with greater disease progression. PMID: 29655286
- ERbeta1 exhibits a heterogeneous distribution in deep infiltrating endometriosis. PMID: 29383962
- The ER-alpha36/EGFR signaling loop promotes the growth of hepatocellular carcinoma cells. PMID: 29481815
- This study aimed to determine the presence and localization of estrogen receptors (ERs), progesterone receptors (PRs), and androgen receptors (ARs) in both healthy and varicose vein wall cells and their relationship with gender. PMID: 30250632
- Estrogen receptor-alpha was expressed only in women and showed a positive correlation with the amount of fungi in oral paracoccidioidomycosis, while progesterone receptor was observed in both genders and exhibited no correlation with estrogen receptor-alpha or fungi counting. PMID: 29796757
- ERalpha upregulates vinculin expression in breast cancer cells. Loss of vinculin promotes amoeboid features of cancer cells. PMID: 28266545
- Polymorphisms in ESR1 do not predict in vitro fertilization outcome. PMID: 29916276
- High ESR1 expression is associated with metastasis in breast cancer. PMID: 29187405
- The G/G XbaI genotype of the ESR1 gene is associated with breast cancer risk. PMID: 29893332
- miR-221 may impair the protective effect of estrogen in degenerated cartilaginous endplate cells through targeting estrogen receptor alpha. PMID: 29529124
- Results showed that NAT1 and ESR1 expression were increased in primary breast tumor samples compared with normal breast tissue samples, and in ER+ primary breast tumors compared with ER- tumors. Additionally, NAT1 and ESR1 expression seem to have overlapping regulation. PMID: 29901116
- All patients without these mutations by molecular barcode next-generation sequencing (MB-NGS) were found to have no mutations by ddPCR. In conclusion, MB-NGS could successfully detect ESR1 mutations in cfDNA with a higher sensitivity of 0.1% than conventional NGS and was considered clinically useful as ddPCR. PMID: 28905136
- In summary, an association between the presence of the particular genotypes at the three ESR1 polymorphisms (rs2234693, rs6902771, rs7774230) and one ESR2 polymorphism (rs3020449), and the presence of metabolic syndrome in postmenopausal women was found. PMID: 30049354
- A higher frequency of ESR1 and PIK3CA mutations was found in the plasma than in the serum in 33 MBC patients. Therefore, serum samples should not be considered the preferred source of cfDNA. PMID: 29689710
- These results suggest that miR-125a-3p can function as a novel tumor suppressor in ER(+) breast cancer by targeting CDK3, which may be a potential therapeutic approach for TamR breast cancer therapy. PMID: 28939591
- A major finding of our study is that one out of five (20%) patients with breast cancer BM had a receptor discrepancy between the primary tumor and the subsequent BM, with loss of hormone receptors (ER and/or PR) expression, and gain of HER2 overexpression as the most commonly observed changes. PMID: 28975433
- This report highlights a nodal role of IGF-IR in the regulation of ERalpha-positive breast cancer cell aggressiveness and the regulation of expression levels of several extracellular matrix molecules. PMID: 28079144
- The associations between PvuII (T>C) and XbaI (A>G) polymorphisms of estrogen receptor alpha (ESR1) gene with type 2 diabetes mellitus (T2DM) or metabolic syndrome (MetS), are reported. PMID: 29883973
- The ERalpha gene appears to play a key role in stress urinary incontinence in the premenopausal period. PMID: 29769420
- This study reports the first discovery of naturally occurring ESR1 (Y537C) and ESR1 (Y537S) mutations in MCF7 and SUM44 ESR1-positive cell lines after acquisition of resistance to long-term-estrogen-deprivation (LTED) and subsequent resistance to fulvestrant (ICIR). Mutations were enriched with time, impacted on ESR1 binding to the genome and altered the ESR1 interactome. PMID: 29192207
- Concomitant high expression of ERalpha36, GRP78 and GRP94 is associated with aggressive papillary thyroid cancer behavior and may be used as a predictor for extrathyroid extension, lymph node metastasis, and distant metastasis. PMID: 29368272
- Estrogen receptor-1 is a key regulator of HIV-1 latency that imparts gender-specific restrictions on the latent reservoir. PMID: 30061382
- Down-regulation of ESR1 gene expression was enhanced by the development of breast cancer. PMID: 29543921
- The aim of this study was to assess whether fibrosis markers, estrogen receptor (ER)alpha, and the stromal-derived factor (SDF)1/CXC chemokine receptor type 4 (CXCR4) axis are abnormally expressed in Intrauterine adhesions endometrium. PMID: 29568895
- The frequency of alleles and genotypes of polymorphisms FSHR(-29G/A) and ESRI (XbaI A/G) in women with normal to poor response did not have a significant correlation. PMID: 29526845
- Each estrogen receptor alpha and estrogen receptor beta gene polymorphism might have different impacts on postmenopausal osteoporosis risk and bone mineral density in various ethnicities. PMID: 29458346
- The results suggest that the minor allele A of the ESR1 gene is associated with the development of arterial hypertension in men. PMID: 29658078
- This study found that tamoxifen treatment induced a decrease in PRMT2 and an increase in ER-alpha36 as well as ER-alpha36-mediated non-genomic effect in the MDA-MB-231 breast cancer cell line. PMID: 29620287
- ESR1 mutations are not associated with clinical resistance to fulvestrant in breast cancer patients. PMID: 27174596
- Overexpression of COPS5, through its isopeptidase activity, leads to ubiquitination and proteasome-mediated degradation of NCoR, a key corepressor for ERalpha and tamoxifen-mediated suppression of ERalpha target genes. PMID: 27375289
- ESR alpha PvuII and XbaI polymorphisms have no association with systemic lupus erythematosus. The combination of the TC/AA and CC/GG genotypes were associated with SLE susceptibility. PMID: 29356461
- Estrogen receptor (ER) and progesterone receptor (PR) expression in endometrial carcinoma (EC) were significantly higher than those in the paracarcinoma tissue and control. PMID: 29081408
- ESR1 promoter methylation was an independent risk factor and had a high value to predict 28-day mortality from acute-on-chronic hepatitis B liver failure. PMID: 29082740
- By analyzing different estrogen receptor-alpha(ER-a)-positive and ER-a-negative breast cancer cell lines, the role of CCN5 in the leptin-mediated regulation of growth and invasive capacity was defined. PMID: 29370782
- This study identified ESR1 as a direct target of miR-301a-3p. PMID: 29763890
- This report presents the first discovery of the presence of ESR1 methylation in plasma ctDNA of patients with HGSC. The agreement between ESR1 methylation in primary tumors and paired ctDNA is statistically significant. PMID: 29807696
- This study reports the development of a novel class of ERa AF2 inhibitors, which have the potential to effectively inhibit ERa activity by a unique mechanism and to circumvent the issue of mutation-driven resistance in breast cancer. PMID: 29462880
- The P2X7R rs3751143 and ER-alpha PvuII two-locus interaction confers a significantly high susceptibility to osteoporosis in Chinese postmenopausal women. PMID: 28884379
- Alcohol consumption may have differential effects on concordant and discordant receptor subtypes of breast cancer. PMID: 29353824
- ERalpha and ERbeta mRNA expression was significantly higher (p < 0.05) in tumor tissues relative to their paired normal mucosa and correlated inversely with survival outcome. PMID: 29390981
- High ESR1 expression is associated with Papillary Thyroid Carcinoma. PMID: 28124274
- Oral administration of RAD140 substantially inhibited the growth of AR/ER(+) breast cancer patient-derived xenografts (PDX). Activation of the AR and suppression of the ER pathway, including the ESR1 gene, were seen with RAD140 treatment. PMID: 28974548
- Polymorphism in the ERalpha gene is associated with an increased risk for advanced Pelvic Organ Prolapse. However, polymorphism in the LAMC1 gene does not seem to be associated with such risk. PMID: 29241914
Q&A
What is ESR1 (Ab-167) antibody and what epitope does it recognize?
ESR1 (Ab-167) antibody is a rabbit polyclonal antibody that specifically recognizes the region around the phosphorylation site of serine 167 (Ser167) in human Estrogen Receptor alpha. The antibody is generated against a synthetic peptide sequence around amino acids 165-169 (L-A-S-T-N) derived from human Estrogen Receptor-α . This site is a critical regulatory phosphorylation target that affects receptor function and signaling.
What are the recommended applications for ESR1 (Ab-167) antibody?
The antibody has been validated for multiple experimental applications:
| Application | Validated | Recommended Dilution |
|---|---|---|
| Western Blot (WB) | Yes | 1:500-1:1000 |
| Immunohistochemistry (IHC-P) | Yes | 1:50-1:200 |
| Immunofluorescence (IF) | Yes | 1:100-1:200 |
| ELISA | Yes | Varies by protocol |
Validation data shows successful detection in MCF7 cells and human breast carcinoma tissues .
What positive controls are recommended for ESR1 (Ab-167) antibody experiments?
Based on validation studies, the following positive controls are recommended:
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Tissue samples: Human breast carcinoma tissue (particularly ER+ samples)
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Lysates: Extracts from estradiol or growth factor-stimulated cells, which enhance Ser167 phosphorylation
Validation images demonstrate specific staining in these control samples with appropriate signal localization.
What is the best method for validating antibody specificity for phospho-Ser167 ESR1?
Thorough validation should include multiple approaches:
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Peptide competition assay: Pre-incubate the antibody with the immunizing phosphopeptide to block specific binding. This should eliminate the signal in Western blot, IHC, and IF applications .
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Phosphatase treatment: Treat a portion of your positive control samples with lambda phosphatase to remove phosphorylation. A true phospho-specific antibody will show diminished or absent signal after treatment .
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siRNA knockdown: Compare staining between ESR1 knockdown and control cells to confirm specificity.
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Multi-application concordance: Verify that the antibody produces consistent results across different applications (WB, IHC, IF) .
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Mass spectrometry validation: For definitive validation, immunoprecipitate with the antibody and confirm target identity by mass spectrometry .
How does sample preparation affect ESR1 (Ab-167) antibody performance?
The phosphorylation status of Ser167 is highly sensitive to sample handling conditions:
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Fixation for IHC/IF: Overfixation can mask the epitope. Optimal fixation is 10% neutral buffered formalin for 24-48 hours. For frozen sections, 4% paraformaldehyde for 10-15 minutes is recommended .
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Antigen retrieval: Heat-induced epitope retrieval using citrate buffer (pH 6.0) or EDTA buffer (pH 9.0) is essential for formalin-fixed samples .
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Lysis buffers for WB: Include phosphatase inhibitors (sodium fluoride, sodium orthovanadate, β-glycerophosphate) to preserve phosphorylation status. Cell signaling lysis buffer supplemented with protease inhibitors is recommended .
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Sample collection timing: Phosphorylation at Ser167 can be rapidly lost post-mortem or after sample collection. Samples should be processed or flash-frozen immediately .
How can ESR1 (Ab-167) antibody be used to study treatment resistance in breast cancer?
Phosphorylation at Ser167 has been implicated in tamoxifen resistance and endocrine therapy response. Methodological approach:
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Comparative analysis: Quantify phospho-Ser167 levels between sensitive and resistant cell lines using Western blot with densitometry (normalizing to total ESR1) .
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Tissue microarrays: Perform IHC on patient samples with known treatment response to correlate phospho-Ser167 status with clinical outcomes.
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Pathway inhibition studies: Combine with kinase inhibitors targeting AKT, p90RSK, or mTOR (kinases that phosphorylate Ser167) to determine signaling dependencies .
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Mutation context analysis: Compare phospho-Ser167 levels between wild-type ESR1 and samples with activating mutations (Y537S, D538G) that confer resistance to treatment .
What other ESR1 phosphorylation sites should be analyzed alongside Ser167?
A comprehensive analysis should include multiple regulatory phosphorylation sites:
| Phosphorylation Site | Kinase | Functional Significance |
|---|---|---|
| Ser118 | ERK1/2, IKKα | AF-1 activation, coactivator binding |
| Ser167 | AKT, p90RSK, mTOR | DNA binding, stability, tamoxifen response |
| Ser305 | PKA, PAK1 | Ligand-independent activation |
| Tyr537 | Src, EGFR | Conformational change, constitutive activity |
For multi-site analysis, use parallel Western blots or multiplexed immunofluorescence with site-specific antibodies against each phosphorylation site .
How do ESR1 mutations affect antibody recognition and experimental interpretation?
Recent studies have identified activating ESR1 mutations in metastatic breast cancer patients. These mutations affect antibody performance in several ways:
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Conformational changes: Mutations like Y537S and D538G in the ligand-binding domain alter protein conformation, potentially affecting epitope accessibility .
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Baseline phosphorylation: Activating mutations can alter baseline phosphorylation at multiple sites, including Ser167, independent of upstream signaling .
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Experimental design considerations:
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Always include both wild-type and mutant-expressing controls
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Use genomic analysis to identify mutation status of samples
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Consider differential drug responses when interpreting phosphorylation patterns
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For patient-derived samples, correlate antibody signals with sequencing data
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What methodological considerations are important when quantifying ESR1 phosphorylation across different samples?
For accurate quantification:
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Normalization strategy: Always normalize phospho-specific signal to total ESR1 levels to account for expression differences.
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Internal controls: Include recombinant phosphorylated standards at known concentrations for absolute quantification.
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Technical considerations:
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Use fluorescent secondary antibodies for wider linear detection range
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Perform time-course experiments to capture dynamic phosphorylation events
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Utilize digital image analysis software for objective quantification
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Advanced quantification methods:
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Quantitative mass spectrometry for precise stoichiometry determination
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Reverse phase protein arrays for high-throughput analysis
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Phospho-flow cytometry for single-cell resolution
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How should researchers troubleshoot weak or inconsistent signals with ESR1 (Ab-167) antibody?
When facing detection challenges:
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Verifying phosphorylation status:
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Application-specific troubleshooting:
For Western blot:
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Ensure complete transfer of higher molecular weight proteins
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Optimize blocking conditions (5% BSA is often superior to milk for phospho-epitopes)
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Consider longer primary antibody incubation (overnight at 4°C)
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Use enhanced chemiluminescence detection systems
For IHC/IF:
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Optimize antigen retrieval (test both citrate and EDTA buffers)
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Extend primary antibody incubation time
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Use amplification systems (TSA, polymer detection)
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Reduce background with additional blocking steps
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What are the critical differences between phospho-specific and total ESR1 antibodies?
Understanding these differences is crucial for experimental design:
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Detection targets:
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Phospho-specific antibodies like ESR1 (Ab-167) detect only the fraction of receptor phosphorylated at Ser167
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Total ESR1 antibodies detect the receptor regardless of phosphorylation status
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Experimental implications:
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Changes in phospho-ESR1 signal may reflect altered phosphorylation OR altered total expression
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Always run parallel blots with total ESR1 antibodies for proper interpretation
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The ratio of phospho/total provides insight into the activation state independent of expression levels
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Control selection:
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For phospho-antibodies: include both positive controls (treated to induce phosphorylation) and negative controls (phosphatase-treated)
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For total antibodies: verified ESR1-expressing and ESR1-negative cell lines serve as controls
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