Anti-Calpain-3 Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight should I expect for Calpain-3 on Western blot?

Full-length Calpain-3 migrates at approximately 94 kDa on SDS-PAGE, which accounts for its alternative name calpain p94. The 821-amino acid protein has a calculated mass near 94 kDa. Be aware that Calpain-3 undergoes rapid autolysis upon extraction from muscle tissue due to its intrinsic calcium sensitivity, so you may observe proteolytic fragments in the 55-60 kDa range depending on sample preparation speed and protease inhibitor cocktail efficacy. Fresh or snap-frozen skeletal muscle lysates prepared in the presence of EDTA and calpain inhibitors yield the most consistent full-length band.

What dilution should I start with for Calpain-3 Western blot?

We recommend starting at 1:1000 dilution for Western blot applications with this rabbit polyclonal antibody. This dilution has been validated in human skeletal muscle lysates. Depending on your sample source, protein loading amount, and detection system sensitivity, you may need to optimize between 1:500 and 1:2000. Skeletal muscle expresses Calpain-3 abundantly, so signal intensity is typically robust at 1:1000. For non-muscle tissues or cells with lower endogenous expression, consider starting at 1:500 and titrating upward to minimize background while maintaining signal.

Does this Calpain-3 antibody cross-react with other calpain family members?

Calpain-3 shares structural homology with ubiquitous calpains (CAPN1 and CAPN2), particularly in the catalytic domain, which raises potential cross-reactivity concerns. This polyclonal was raised against Calpain-3-specific sequences, but we recommend including lysates from Calpain-3-null tissue or cells as a specificity control if available. LGMDR1 patient-derived myoblasts lacking functional CAPN3 serve as an ideal negative control. In skeletal muscle, where Calpain-3 is the predominant muscle-specific isoform, the 94 kDa band should disappear or substantially diminish in knockout samples, while ubiquitous calpains migrate differently.

Can I use this antibody to detect mouse or rat Calpain-3?

Human Calpain-3 shares approximately 86% sequence identity with mouse and 85% with rat orthologs, suggesting cross-reactivity is likely but not yet experimentally validated by Triple Point Biologics for this antibody. Researchers have reported successful detection of rodent Calpain-3 in skeletal muscle lysates using antibodies raised against human epitopes, but we classify mouse and rat as predicted rather than validated species. If working with rodent samples, include a positive control lysate from mouse or rat skeletal muscle (gastrocnemius or quadriceps) and be prepared to optimize dilution, as epitope accessibility may differ from human.

What is the best positive control tissue for Calpain-3 detection?

Skeletal muscle is the optimal positive control tissue because Calpain-3 expression is predominantly restricted to this compartment. Human skeletal muscle lysate from limb muscles (quadriceps, biceps, gastrocnemius) will provide robust signal at the expected 94 kDa. Cardiac muscle expresses Calpain-3 at much lower levels. Avoid smooth muscle, liver, or brain as positive controls since Calpain-3 is nearly undetectable in these tissues. For cell culture work, differentiated myotubes or myoblasts (C2C12 after differentiation, primary human myotubes) serve as appropriate positive controls, though expression levels depend on differentiation efficiency.

Why do I see multiple bands below 94 kDa on my Calpain-3 Western blot?

Calpain-3 is highly susceptible to autolytic cleavage upon calcium exposure during tissue extraction. If you observe bands at 55-60 kDa or other lower molecular weights alongside or instead of the full-length 94 kDa band, this typically reflects autolysis rather than non-specific binding. To minimize degradation, work quickly during lysis, keep samples ice-cold, include 5 mM EDTA or EGTA in lysis buffer to chelate calcium, and add a broad-spectrum protease inhibitor cocktail containing calpain inhibitors such as leupeptin or E-64. Snap-freezing tissue in liquid nitrogen immediately after harvest also preserves full-length protein.

How should I store this Calpain-3 antibody for long-term stability?

Store the antibody at -20°C in undiluted aliquots to maintain stability. Avoid repeated freeze-thaw cycles, which can reduce antibody activity over time. For frequent use, prepare working aliquots: dilute a portion in antibody storage buffer containing carrier protein and 50% glycerol, which remains liquid at -20°C and allows direct pipetting without thawing. Once diluted in blocking buffer for Western blot, the antibody can be stored at 4°C with 0.02% sodium azide and reused for up to one week, though fresh dilutions generally provide optimal signal-to-noise ratios.

Does Calpain-3 require special sample preparation compared to other proteases?

Yes. Calpain-3 is calcium-activated and will autolyze rapidly if calcium is present during lysis. Always include calcium chelators (5-10 mM EDTA or EGTA) in your lysis buffer. Additionally, because Calpain-3 is a thiol protease with an active-site cysteine, avoid reducing agents like DTT or β-mercaptoethanol in excess during prolonged sample handling prior to denaturation, as they can affect enzyme conformation. Denature samples promptly by boiling in SDS-containing sample buffer. For muscle biopsies, minimize the time between excision and snap-freezing to prevent post-mortem proteolysis.