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CASP9 · Western blot design guide
Design a Western Blot for CASP9
Real validated CASP9 Western blot protocols, expected-band and isoform facts, troubleshooting for weak or shifted signal, and recommended anti-CASP9 WB antibodies. Everything you need to plan the experiment before you commit precious samples.
Last reviewed: May 2026 · Scientific review: Boster Bio technical team
CASP9 Western Blot Experimental Design Guide
Expected bands, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before running
| Expected band | ~46.3 kDa | |
| Observed band | 46 kDa | |
| Gel | 10–12% | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your observed band may differ from the expected size.
| PTM | Phosphorylated + Cleaved | |
| Caveat | Proteolytic cleavage | |
| Regulation | Apoptosis | |
| Isoform | 4 isoform(s) |
Section 1
Real Curated CASP9 Western Blot Protocols
Literature-validated Western blot parameters for CASP9 — gel percentage, transfer, blocking, antibody incubation and detection, extracted from published methods.
| Sample / lysate | human Hela, human A549 |
| Gel % | 5–20% |
| Load | 30ug |
| Transfer | nitrocellulose membrane, 150 mA, 50–90 min |
| Membrane | nitrocellulose |
| Blocking | 5% non-fat milk / TBS, 1.5 h RT |
| Primary antibody | 0.5 µg/mL |
| Primary incubation | overnight at 4 °C |
| Secondary antibody | goat anti-rabbit IgG-HRP, 1:5000 |
| Wash | TBS-0.1% Tween, 3 × 5 min |
| Detection | ECL |
| Exposure / imaging | Tanon 5200 |
| Observed band | 46 kDa |
Section 2
What Is the Expected CASP9 Western Blot Band Size?
CASP9 has a 46.3 kDa backbone and typically runs at 46 kDa as the zymogen, with lower bands arising from proteolytic processing to p35 and p10.
| Single band at 46 kDa | full-length caspase-9 zymogen close to the 46.3 kDa predicted backbone |
| Band near 35 kDa | processed caspase-9 p35 cleavage product from zymogen maturation |
| Smaller fragment near 10 kDa | processed caspase-9 p10 small subunit |
| Multiple bands between full-length and smaller fragments | coexistence of precursor, processed subunits, and splice isoforms 1 to 4 |
💡Expected CASP9 appearanceUnder reducing whole-cell lysate conditions, expect a main CASP9 band at 46 kDa for the full-length zymogen, with possible additional lower processed bands such as the p35 cleavage product.
| 46.3 kDa predicted backbone | supports a full-length band around 46 kDa |
| zymogen propeptide and proteolytic maturation | creates smaller mature cleavage products than the precursor |
| p35 subunit formation | produces a prominent lower band near 35 kDa after processing |
| p10 subunit formation | produces a much smaller fragment band |
| alternative splicing isoforms 1, 2, 3, and 4 | can generate additional bands of different relative sizes |
| Situation | Likely cause | Next action |
|---|---|---|
| Band higher than expected | full-length zymogen is being compared with a processed p35 expectation | distinguish whether your antibody should detect precursor 46 kDa, processed p35, or both |
| Band lower than expected | caspase-9 has undergone proteolytic processing from the zymogen into smaller subunits | look for the accompanying full-length 46 kDa band and expected processed fragments such as p35 |
| Multiple bands | mixture of precursor, processed products, and splice isoforms 1 to 4 | interpret bands in the context of activation state and confirm which isoforms or cleavage forms your antibody recognizes |
| Weak or no signal | the detected epitope may be absent from the dominant processed form or from some isoforms | check the antibody immunogen region and use a lysate expected to contain full-length CASP9 if targeting the 46 kDa species |
| Fragments below expected size | normal caspase-9 maturation generates smaller subunits including p35 and p10 | treat lower bands as plausible processing products rather than nonspecific bands if they accompany CASP9 precursor loss |
Experiment evidence
Western blot images showing CASP9 band
A00080-5 · CASP9
A00080-6 · CASP9
A00080-8 · CASP9
PA1595 · CASP9
PB9332 · CASP9
← swipe / scroll for more images →
Real WB data behind the band-size expectations in this section.
Sample controls for CASP9 Western blot
🧪For positive controls for CASP9 in Western blot, you can use adrenal gland lysate as a positive control based on HPA medium expression.
Positive control: Adrenal gland
Negative control: Adipose tissue
Loading controls: Run GAPDH, β-actin, and a total-protein stain such as stain-free, Ponceau, or REVERT alongside.
⚠️Feasibility: Controls are reasonably feasible because HPA shows medium-positive tissues and low-expression tissues, though a completely absent normal-tissue negative control is not evident.
HPA tissue expression evidence for CASP9
Comprehensive Human Protein Atlas IHC scoring per tissue. 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 |
|---|---|---|---|---|
| Adrenal gland | glandular cells | Medium | Protein (IHC) | HPA → |
| Appendix | glandular cells | Medium | Protein (IHC) | HPA → |
| Bone marrow | hematopoietic cells | Medium | Protein (IHC) | HPA → |
| Breast | glandular cells | Medium | Protein (IHC) | HPA → |
| Bronchus | respiratory epithelial cells | Medium | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | adipocytes | Low | Protein (IHC) | HPA → |
| Esophagus | squamous epithelial cells | Low | Protein (IHC) | HPA → |
| Liver | cholangiocytes | Low | Protein (IHC) | HPA → |
| Lung | alveolar cells | Low | Protein (IHC) | HPA → |
| Oral mucosa | squamous epithelial cells | Low | Protein (IHC) | HPA → |
Section 3
Advanced CASP9 Western Blot Tips
Deeper troubleshooting and optimisation questions for CASP9, answered from its protein features.
Why might CASP9 show bands besides 46 kDa?
CASP9 is a zymogen that is processed into a 35 kDa p35 subunit and a 10 kDa p10 subunit. Depending on the antibody epitope, you may detect full-length protein near 46 kDa, processed fragments, or both. Alternative splicing can also add isoform-dependent bands.
Could alternative splicing affect CASP9 band patterns?
Yes. UniProt lists four CASP9 isoforms. Different isoforms can migrate differently and may not all contain the same antibody epitope. If you see multiple specific bands, check whether your antibody targets a region shared by all isoforms or only a subset.
Can apoptosis change the CASP9 Western blot pattern?
Yes. CASP9 is an apoptosis-related zymogen and forms an active complex containing p35 and p10 subunits. During apoptotic activation, full-length CASP9 near 46 kDa can decrease while cleavage products appear. Interpreting activation therefore requires knowing whether your antibody recognizes precursor, cleaved forms, or both.
Do PTMs complicate CASP9 band interpretation?
Potentially. UniProt annotates CASP9 as a phosphoprotein and also includes Ubl conjugation among keywords. These modifications can alter apparent mobility or create band heterogeneity around the main species. If bands are close together, consider that modification state may contribute alongside cleavage and isoform differences.
What transfer method to use for CASP9 Western blot?
CASP9 full-length is about 46.3 kDa, which transfers well with standard wet or semi-dry conditions. If you need to detect the 10 kDa p10 fragment, optimize for small proteins by avoiding over-transfer and using conditions that retain low-mass species efficiently.
How should CASP9 be quantified on Western blot?
Quantify the band that matches your biological question. For total CASP9, measure the full-length band near 46 kDa using an antibody validated for the precursor. For activation studies, quantify full-length loss and appearance of p35 or p10 separately, because cleavage changes the distribution of signal.
How can antibody choice affect CASP9 band detection?
CASP9 undergoes cleavage and has four isoforms, so epitope location matters. An N-terminal antibody may detect precursor and some processed species differently than a C-terminal antibody. Choose an antibody against a region present in the forms you want to measure, and expect different band patterns with different epitopes.
Boster reagents
Best CASP9 Western Blot Antibodies
BosterBio's CASP9 antibodies are among the best-performing WB antibodies on the market — well cited, thoroughly validated, and orthogonally cross-validated against negative tissues and complementary methods.
Real WB data
Anti-Caspase-9/CASP9 Antibody Picoband®
Cat # A00080-5
Real WB data
Anti-Caspase-9/CASP9 Antibody Picoband®
Cat # A00080-6
Real WB data
Anti-Caspase-9/CASP9 Antibody Picoband®
Cat # A00080-8
Real WB data
Anti-Caspase 9/CASP9 Antibody Picoband®
Cat # PA1595
Real WB data
Anti-Caspase-9/CASP9 Antibody Picoband®
Cat # PB9332
These recommended anti-CASP9 Western blot antibodies represent Boster’s best-performing, well-cited, thoroughly validated options, with orthogonal cross-validation supported by negative-tissue and complementary-method evidence for confident band assignment.
Which to pick: For CASP9, all listed SKUs include WB validation images. Start with A00080-5, A00080-6, or A00080-8 for direct CASP9 WB examples; consider PA1595 or Picoband PB9332 if you want additional lysate-panel validation.
Source: BosterBio CASP9 gene-info card — filtered to Western-blot-capable antibodies; each card shows that product's actual WB validation figure.
References
- UniProt Consortium. UniProt entry P55211.
- Human Protein Atlas. CASP9 tissue expression.