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EIF2S1 / Eukaryotic translation initiation factor 2 subunit 1 · IHC design guide
Design Immunohistochemistry for EIF2S1
Plan EIF2S1 paraffin IHC around the widespread cytoplasmic tissue pattern (HPA tissue IHC). Use total EIF2S1 staining for protein distribution and phospho-S51 staining when assessing its stress response (UniProt; catalog P04387).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
EIF2S1 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Cytoplasmic staining in tissue (HPA tissue IHC) | |
| Staining pattern | Widespread cytoplasmic staining across cell types (HPA tissue IHC) | |
| Antigen retrieval | Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen) | |
| Positive control | Adipose tissue+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image M04387-6) | |
| Caveat | Phospho-S51 staining varies with stress state (UniProt; catalog P04387) | |
| Regulation | Stress induces EIF2S1 phosphorylation (UniProt) | |
| Isoform / epitope | 0 annotated isoforms; one 1–315 chain (UniProt) |
Section 1
Recommended EIF2S1 IHC & IF Protocols
The catalog antibody protocol is followed by published EIF2S1 IHC methods for intestinal-type adenocarcinoma tissue arrays and paraffin-embedded liver sections (PMC8616251; PMC10079382).
| Sample | Tissue sections; selected-image fixative not specified (standard IHC workflow) |
| Fixation | Image fixative and duration unreported (datasheet M04387-6); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in citrate buffer, pH 6.0, 20 min at 95–98 °C (standard rule: cytoplasmic / membrane antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit anti-EIF2S1, 1:1000-1:5000 (datasheet M04387-6) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | EIF2S1-positive staining in adipocytes of adipose tissue (HPA tissue IHC: High). HPA tissue profile: Ubiquitous cytoplasmic expression. No signal in the no-primary control. |
💡Decision noteStart with citrate pH 6.0 retrieval at 95–98 °C for 20 min for cytoplasmic EIF2S1 (page retrieval rule; UniProt P05198 localisation).
Section 2
What Is the Expected EIF2S1 Staining Pattern?
EIF2S1 should show broadly distributed cytoplasmic staining in paraffin sections (HPA: ubiquitous cytoplasmic expression; IHC reliability Supported, with medium consistency against RNA data). High staining is reported in adipocytes, respiratory epithelial cells, neurons, glandular cells and some endothelial cells (HPA: tissue IHC). A dominant membrane pattern is unexpected for this protein (UniProt P05198: no transmembrane segment).
| Cytoplasmic staining across several cell populations, with stronger cells in expected sites. | This fits the reported broad distribution (HPA: ubiquitous cytoplasmic expression). Adipocytes, bronchial respiratory epithelium, cerebellar Purkinje cells, cerebral cortical neurons, duodenal and endometrial glandular cells, and colonic endothelial cells are reported as High (HPA: tissue IHC). Compare intensity within the same staining run; High is an HPA category, not a calibrated score. |
| Predominantly nuclear, crisp membrane, or extracellular staining. | These are poor matches to the reported cytoplasmic tissue pattern and cytosolic localization (HPA: tissue IHC; HPA: ICC-IF). A membrane outline alone has no support from the recorded topology (UniProt P05198: no transmembrane segment). Review morphology, background and controls before assigning the signal to EIF2S1 (general IHC practice). |
| Strong signal in a cell population expected to be low while nearby expected High cells remain blank. | Consider cross-reactivity or endogenous detection activity, particularly if staining persists in a no-primary control (general IHC practice). Interpret the discrepancy against the sampled tissue: cardiomyocytes, skeletal myocytes, smooth muscle cells, cholangiocytes, ovarian follicle cells and chondrocytes are listed as Low, not absent (HPA: tissue IHC). |
| Uniform haze over cells, stroma and blank areas. | This lacks the cell-associated cytoplasmic pattern expected for EIF2S1 (HPA: tissue IHC). Diffuse chromogen can reflect background from detection reagents, insufficient blocking or washing, or an overly concentrated primary (general IHC practice). Use a no-primary control and assess whether cellular contrast remains after background is reduced. |
| No staining in a known High cell population. | An all-blank section is inconclusive when an expected positive population is present (HPA: tissue IHC). Check that tissue morphology is preserved and the detection system works; then optimize the IHC-validated antibody under its documented conditions (general IHC practice). The supplied sources give no EIF2S1-specific fixation or retrieval sensitivity. |
💡Expected EIF2S1 appearanceCall the result positive when cell-associated cytoplasmic chromogen is clear in an expected High population, such as bronchial respiratory epithelium or cerebellar Purkinje cells (HPA: tissue IHC); dominant nuclear outlines, membrane rims or tissue-wide haze warrant control review (HPA: cytoplasmic expression; general IHC practice).
| Cell and tissue context | Expression is described as ubiquitous and cytoplasmic, with low tissue specificity at the RNA level (HPA: tissue IHC). High and Low labels are relative observations; the supplied HPA set names no negative tissue. Select a documented High population for a positive control and avoid treating a Low population as a knockout control. |
| Antibody validation | HPA064885 and CAB011663 are each listed as IHC Supported (HPA: antibody records). Supported is the supplied status; do not upgrade either antibody to Enhanced. Review the actual catalog antibody's IHC-P documentation before applying a dilution or retrieval condition; neither is provided here. |
| Phosphorylation and mitochondrial stress | EIF2S1 phosphorylation participates in the integrated stress response, and mitochondrial damage can promote relocation to the mitochondrial surface (UniProt P05198: function, subcellular location). Routine tissue IHC intensity does not establish phosphorylation state or mitophagy without a validated state-specific assay (general IHC interpretation). |
| Cytosol and stress granules | Cytosol and stress granules are annotated locations, with stress-granule colocalization supported by similarity (UniProt P05198: subcellular location). HPA describes the observed tissue pattern as ubiquitous cytoplasmic expression (HPA: tissue IHC); do not require puncta to call a routine chromogenic section positive. |
| Retrieval and detection controls | Antigen retrieval, blocking and detection chemistry are adjustable parts of paraffin-section IHC (general IHC practice). Optimize them against a documented positive tissue and a no-primary control; the supplied UniProt and HPA records do not specify an EIF2S1-specific retrieval condition or fixation effect. |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected High cells show no chromogen. | An assay or detection failure is possible; the expected population is documented as High (HPA: tissue IHC). | Confirm tissue identity and morphology, run a working detection control, and follow the catalog antibody's IHC-P instructions before adjusting retrieval or primary concentration (general IHC practice). |
| Whole section has diffuse brown background. | Non-specific reagent binding, residual endogenous detection activity, or inadequate washing can obscure the expected cytoplasmic signal (general IHC practice; HPA: tissue IHC). | Compare a no-primary control, check blocking and endogenous-activity quenching appropriate to the detection chemistry, and reduce primary or detection reagent concentration if controls implicate those steps (general IHC practice). |
| Nuclei or cell borders dominate the image. | The compartment conflicts with HPA's cytoplasmic tissue profile and UniProt's lack of a transmembrane segment (HPA: tissue IHC; UniProt P05198: topology). | Inspect morphology and no-primary staining, then repeat with documented IHC conditions or another appropriately validated antibody if the discordance persists (general IHC practice). |
| Low-listed cells appear stronger than nearby High-listed cells. | Cell identification, section context or non-specific staining may explain the mismatch; HPA's Low category does not mean absent (HPA: tissue IHC). | Verify cell identities and compare an expected High population in the same run. Treat isolated discordance cautiously, especially if the no-primary control stains those cells (general IHC practice). |
| The sample has only weakly stained muscle or another Low-listed population. | Cardiomyocytes, myocytes and smooth muscle cells are listed as Low (HPA: tissue IHC); weak staining there alone cannot demonstrate assay failure. | Include a documented High population as a positive control before changing assay conditions (HPA: tissue IHC; general IHC practice). |
| What should IF/ICC show? | HPA reports enhanced cytosolic localization in ICC-IF, while UniProt also annotates stress granules and conditional mitochondrial-surface relocation (HPA: subcellular; UniProt P05198: subcellular location). | Expect a cytosolic signal in a suitable IF/ICC experiment (HPA: subcellular). Interpret puncta or mitochondrial proximity only with appropriate colocalization and condition controls; this IHC guide supplies no IF/ICC protocol (general IF practice). |
Experiment evidence
IHC & IF images showing EIF2S1 staining
M04387-6 · IHCHuman breast was stained with anti-eIF2α rabbit antibody
M04387-6 · IHCHuman kidney was stained with anti-eIF2α rabbit antibody
P04387 · IHCImmunohistochemical analysis of paraffin-embedded human colon cancer, using Phospho-eIF2 alpha (Ser51) Antibody.
P04387 · IFImmunofluorescent analysis using the Antibody at 1:50 dilution.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000134001-EIF2S1/tissue/cerebral+cortex#imid_17868227
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000134001-EIF2S1/tissue/colon#imid_17868169
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000134001-EIF2S1/tissue/liver#imid_17868170
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000134001-EIF2S1/tissue/kidney#imid_17868163
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB011663; green = EIF2S1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB011663; green = EIF2S1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for EIF2S1 IHC & IF
🧪Run breast first and look for staining in adipocytes (HPA: High in breast adipocytes; selected IHC caption: human breast). HPA detects EIF2S1 in all 45 scored tissues, so there is no supported negative tissue; no-primary and isotype controls provide the background reference, and less-stained cells on the positive slide should not be treated as confirmed target-negative cells (HPA: no negative rows).
Positive control tissue: Adipose tissue (Adipocytes, HPA High)
Negative control tissue: None in HPA: EIF2S1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show EIF2S1 in A-431, U-251MG, U2OS, MCF-7, with annotated localisation: Cytosol (enhanced) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only section and a host- and clonality-matched isotype control; use EIF2S1-knockout material, if available, or immunizing-peptide competition when the epitope is known as a biological specificity control (standard IHC practice; selected IHC caption: rabbit antibody). Check endogenous peroxidase background in the breast section before interpreting chromogenic staining (standard IHC practice).
⚠️Feasibility: No target-specific fixation window or retrieval effect is reported in the supplied evidence, and the selected breast IHC caption does not state its fixative (selected IHC caption: fixative unreported). HPA ICC-IF images show cytosolic localization, but the supplied evidence does not establish that frozen sections or IF are easier than paraffin IHC (HPA: Cytosol, enhanced; ICC-IF images). In breast adipocytes, assess staining in the thin peripheral cytoplasm around lipid vacuoles; an unstained vacuole is not a negative cell (standard IHC morphology; HPA: High in breast adipocytes).
HPA tissue IHC evidence for EIF2S1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | High | Protein (IHC) | HPA → |
| Breast | Adipocytes | High | Protein (IHC) | HPA → |
| Bronchus | Respiratory epithelial cells | High | Protein (IHC) | HPA → |
| Cerebellum | Purkinje cells | High | Protein (IHC) | HPA → |
| Cerebral cortex | Neuronal cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: EIF2S1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced EIF2S1 IHC Tips
Troubleshoot chromogenic IHC for EIF2S1 in paraffin sections using the specified retrieval setting, reported localisation, and tissue staining evidence.
How should I retrieve EIF2S1 if cytoplasmic staining is weak in paraffin sections?
Start with citrate buffer at pH 6.0 for heat-induced epitope retrieval at 95–98 °C for 20 min (page retrieval setting). Allow sections to cool in buffer, then compare staining with an otherwise identical section processed without retrieval; this checks whether heating improves the signal (standard IHC practice). Because EIF2S1 is reported in the cytosol and has no transmembrane segment, assess cytoplasmic staining in intact cells rather than treating membrane outlines as the expected pattern (HPA: cytosol; UniProt P05198 topology). If staining remains weak, test an alternative retrieval condition on matched sections while holding antibody dilution and detection conditions constant (standard IHC practice).
Can I attribute weak EIF2S1 staining to the fixation used for my paraffin sections?
Target-specific fixation sensitivity is unknown from the supplied evidence, so weak EIF2S1 staining alone cannot identify fixation as the cause (supplied evidence: no target-specific fixation data). The selected M04387-6 image describes staining in human breast but does not state its fixative; it cannot establish an optimal fixation time or chemistry (selected tissue-IHC caption). Review the documented fixative and processing history, then compare sections processed under known conditions while keeping citrate retrieval at pH 6.0, antibody dilution, and detection constant (page retrieval setting; standard IHC practice). Include a positive control section in each comparison so a failed staining run is distinguishable from a sample-specific result (standard IHC practice).
Should I score nuclear or mitochondrial staining as EIF2S1 positive in routine IHC?
Score convincing cytoplasmic staining first: EIF2S1 is reported in the cytosol, and tissue IHC describes ubiquitous cytoplasmic expression (HPA: subcellular; HPA: tissue IHC). UniProt also reports stress granule localisation and mitochondrial-surface relocalisation after mitochondrial damage and EIF2AK1/HRI phosphorylation; routine chromogenic sections alone cannot establish either event (UniProt P05198 localisation and function; standard IHC interpretation). Compare the pattern across intact cells and tissue compartments, using a positive control and a no-primary control on the same run (standard IHC practice). Treat isolated nuclear staining or sharp membrane outlines cautiously because neither is the principal reported localisation (HPA: cytosol; UniProt P05198 topology).
How do I distinguish total EIF2S1 staining from a phosphorylation-dependent epitope?
Confirm whether the catalog antibody recognises total EIF2S1 or a specified modification before interpreting staining intensity as signalling activity; the supplied caption does not define its epitope (selected tissue-IHC caption). UniProt lists one 315-aa chain, no annotated isoforms, and multiple modified residues, including phosphoserines, so isoform switching is not a supported explanation for different staining patterns here (UniProt P05198 processing, isoforms, and modified residues). Compare matched sections stained with appropriately validated total-protein and modification-specific antibodies if phosphorylation is the question (standard IHC practice). Record each antibody's epitope and retrieval conditions separately, since unequal staining cannot by itself distinguish epitope accessibility from protein abundance (standard IHC interpretation).
How should I check EIF2S1 localisation by multiplex IF in tissue?
Pair EIF2S1 with a marker for the cell population being examined, such as an epithelial marker in bronchus, where respiratory epithelial cells show high tissue-IHC staining (HPA: bronchus respiratory epithelial cells; standard IF practice). Assign the weaker signal to a far-red fluorophore when green tissue autofluorescence is troublesome, and inspect single-stain controls for bleed-through (standard IF practice). EIF2S1 is cytosolic and has no transmembrane segment, so use a mild permeabilisation condition appropriate for access to an intracellular epitope and check that cell boundaries remain interpretable (HPA: cytosol; UniProt P05198 topology; standard IF practice). Verify fixation and permeabilisation empirically for the IF antibody because no directly relevant target-specific IF fixation condition is supplied (supplied evidence: no IF fixation condition).
What should I adjust when EIF2S1 DAB staining is diffuse across the section?
Begin with a no-primary control and inspect whether colour persists in the same compartments; residual colour implicates detection or tissue background rather than EIF2S1 binding (standard IHC practice). Use a peroxidase block before DAB detection, then check blocking, washing, primary-antibody dilution, and chromogen development time on matched sections (standard chromogenic IHC practice). Because tissue IHC describes ubiquitous cytoplasmic EIF2S1, widespread cellular signal can be plausible, whereas colour over empty spaces or section edges should not be counted as cellular positivity (HPA: tissue IHC; standard IHC interpretation). Keep the retrieval setting at citrate pH 6.0, 95–98 °C, 20 min while isolating detection variables (page retrieval setting; standard IHC practice).
What is a defensible way to quantify EIF2S1 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and cytoplasmic compartment before scoring, because EIF2S1 tissue staining is described as ubiquitous and cytoplasmic (HPA: tissue IHC). For cell-based scoring, report the percentage of positive cells and an H-score from 0–300, using the same intensity thresholds and regions of interest across samples (standard IHC quantification). If counting positive cells per area, report density per mm² of viable tissue and exclude folds, necrosis, and tissue-free regions (standard IHC quantification). Normalise comparisons to the number of evaluable cells or viable tissue area, and process control and study sections with matched retrieval, detection, and imaging settings (standard IHC practice).
How can I distinguish true EIF2S1 positivity from staining artefacts?
A credible result shows cellular cytoplasmic staining in intact tissue, consistent with the reported EIF2S1 localisation and ubiquitous tissue profile (HPA: subcellular; HPA: tissue IHC). High staining in bronchial respiratory epithelium or breast adipocytes is compatible with the supplied tissue observations, but those patterns alone do not validate a particular antibody or section (HPA: bronchus; HPA: breast). Discount edge accentuation, necrotic debris, staining outside cells, and colour reproduced in a no-primary control; check peroxidase blocking if DAB background persists (standard chromogenic IHC practice). Do not infer integrated stress response activation from total EIF2S1 staining alone, because phosphorylation is the relevant regulatory event and the caption does not specify a phosphorylation-dependent epitope (UniProt P05198 function; selected tissue-IHC caption).
Boster reagents
Best EIF2S1 / Eukaryotic translation initiation factor 2 subunit 1 IHC Antibodies
Anti-EIF2S1 IHC images show human breast, kidney, and colon cancer, plus rat kidney (catalog IHC captions: M04387-6, P04387); P04387 also has an IF image (catalog IF caption).
Real IHC data
Anti-eIF2α Rabbit Monoclonal Antibody
Cat # M04387-6
Real IHC data
Anti-Phospho-EIF2S1 (S51) Rabbit Monoclonal Antibody
Cat # P04387
M04387-6 lists IHC and IF for Human, Mouse, and Rat, with IHC images of human breast, human kidney, and rat kidney (catalog: M04387-6 applications, reactivity, IHC captions). P04387 lists IHC and ICC/IF for Human, Mouse, and Rat, with a paraffin-section IHC image of human colon cancer and an IF image (catalog: P04387 applications, reactivity, IHC and IF captions).
Which to pick: For total eIF2α tissue IHC, choose rabbit monoclonal M04387-6; its IHC captions show human breast and kidney and rat kidney, but do not report processing or fixative (catalog: M04387-6 title and IHC captions). For phospho-Ser51 IHC in paraffin sections or for ICC/IF, choose rabbit monoclonal P04387; its human colon cancer IHC caption specifies paraffin embedding but does not report the fixative, and it has an IF image (catalog: P04387 title, applications, IHC and IF captions). For cross-species planning, both list Human, Mouse, and Rat reactivity; the pictured IHC species are Human and Rat for M04387-6 and Human for P04387 (catalog: both reactivity lists and IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P05198 (IF2A_HUMAN, Eukaryotic translation initiation factor 2 subunit 1).
- Human Protein Atlas. EIF2S1 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. EIF2S1 subcellular location (ICC-IF): Localized to the cytosol..
- Human Protein Atlas. EIF2S1 antibody validation summary (2 antibodies).
- Dysregulation of Translation Factors EIF2S1, EIF5A and EIF6 in Intestinal-Type Adenocarcinoma (ITAC). Cancers 2021 — PMC8616251.
- EIF2S1 Silencing Impedes Neuroblastoma Development Through GPX4 Inactivation and Ferroptosis Induction. International journal of genomics 2024 — PMC11512646.
- EIF2A promotes cell survival during paclitaxel treatment in vitro and in vivo. Journal of cellular and molecular medicine 2019 — PMC6714208.
- Bioinformatics Analysis of Molecular Interactions between Endoplasmic Reticulum Stress and Ferroptosis under Stress Exposure. Analytical cellular pathology (Amsterdam) 2023 — PMC10079382.
- PubMed PMID:2948954 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
- PubMed PMID:10026192 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for EIF2S1 (Eukaryotic translation initiation factor 2 subunit 1). Expected localisation Cytoplasmic staining in tissue (HPA tissue IHC). Antigen retrieval: Citrate pH 6.0 HIER, 95–98 °C, 20 min (rule: cytoplasmic / membrane antigen). Validated IHC antibody: M04387-6 at 1:1000-1:5000 (the product's own IHC validation image is shown). Controls (HPA): positive Adipose tissue (Adipocytes); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC workflow; specimen preparation unspecified. Protocol steps: 1. Sample: Tissue sections; selected-image fixative not specified (standard IHC workflow); 2. Fixation: Image fixative and duration unreported (datasheet M04387-6); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat-induced epitope retrieval in citrate buffer, pH 6.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit anti-EIF2S1, 1:1000-1:5000 (datasheet M04387-6); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image M04387-6); Caveat: Phospho- S51 staining varies with stress state (UniProt; catalog P04387); Isoform / epitope: 0 annotated isoforms; one 1–315 chain (UniProt); Regulation: Stress induces EIF2S1 phosphorylation (UniProt). Evidence: UniProt P05198, HPA tissue IHC · Supported, HPA ICC-IF · cytosol., Datasheet M04387-6, PMC8616251, PMC10079382. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/EIF2S1/immunohistochemistry-ihc-guide.