Anti-Pappalysin-2 Rabbit Polyclonal Antibody

Frequently Asked Questions

What is the expected molecular weight for PAPPA2 on Western blot?

Full-length PAPPA2 runs at approximately 200 kDa on reducing SDS-PAGE, reflecting the 1,791-amino-acid polypeptide plus glycosylation. You may observe heterogeneity due to variable N-glycosylation at multiple sites. In some biological samples, particularly serum or conditioned media, you will detect proteolytic fragments or complexes that migrate differently. If you see bands substantially lower than 200 kDa, consider whether your sample contains active proteases or whether PAPPA2 has been processed. Running a positive control lysate from a known PAPPA2-expressing cell line helps confirm the expected migration pattern.

Does this antibody distinguish between PAPPA and PAPPA2?

PAPPA and PAPPA2 share structural homology as metalloproteinases but differ substantially in sequence and substrate specificity. This polyclonal was raised against a PAPPA2-specific region and shows no cross-reactivity with PAPPA in our validation. However, if you work in pregnancy serum or placental lysates where PAPPA is highly abundant, run parallel controls with recombinant PAPPA2 and verify band identity by size. PAPPA migrates near 400 kDa as a disulfide-linked dimer; PAPPA2 runs at approximately 200 kDa, so gel resolution typically separates them clearly on Western blot.

What dilution should I start with for Western blot and IHC?

For Western blot, start at 1:1000 dilution in 5 percent milk or BSA in TRIS-buffered saline with Tween-20, the validated dilution for this antibody. If your sample expresses PAPPA2 at low levels—common in many tissues outside bone and reproductive organs—you may need to concentrate lysates or increase exposure time rather than raise antibody concentration excessively. For immunohistochemistry, begin at 1:200 to 1:500 on formalin-fixed paraffin-embedded sections with antigen retrieval in citrate buffer, pH 6. Titrate against your specific tissue and fixation protocol.

Which species can I use this PAPPA2 antibody with?

This antibody is validated for human PAPPA2. Predicted cross-reactivity includes mouse, rat, dog, and non-human primate based on epitope homology in the immunogen region, but we have not experimentally confirmed those species. If you work with mouse or rat samples, expect reasonable signal given the approximately 80 percent homology in the target domain, but run a positive control with recombinant protein or a known-positive tissue such as pregnant mouse serum or neonatal bone lysate. Always verify band size and specificity with a blocking peptide or knockout control when working outside validated species.

What tissues or cell types express PAPPA2 at detectable levels?

PAPPA2 is secreted and often detected in conditioned media rather than whole-cell lysates. Pregnancy serum, placental tissue, and osteoblast cultures are rich sources. Postnatal bone, particularly growth-plate chondrocytes and osteoblasts, expresses PAPPA2 during active remodeling. Vascular smooth muscle and endothelial cells show inducible expression under proliferative or inflammatory conditions. If you see weak or absent signal in standard cell lines, consider treating cells with IGF-stimulating conditions or collecting serum-free conditioned medium after 24 to 48 hours to concentrate secreted PAPPA2 before Western blot analysis.

Can I use this antibody for immunoprecipitation or ELISA?

This rabbit polyclonal works reliably for Western blot and immunohistochemistry, the two applications we have validated. Immunoprecipitation is feasible with polyclonals recognizing native epitopes; if you attempt it, use 2 to 5 micrograms antibody per 500 micrograms lysate and include protease inhibitors to prevent PAPPA2 autodegradation. For ELISA, you would need to establish standard curves and validate linearity yourself, as we have not tested this antibody in plate-based assays. Sandwich ELISA typically requires matched pairs of antibodies targeting distinct epitopes, which we do not currently offer for PAPPA2.

How should I store this antibody and what is the shelf life?

Store the antibody at minus 20 degrees Celsius in single-use aliquots to avoid repeated freeze-thaw cycles, which can reduce titre and increase aggregation. The formulation includes glycerol and stabilizers that maintain activity for at least 12 months under these conditions. Once thawed, an aliquot remains stable at 4 degrees Celsius for up to one month; add sodium azide at 0.02 percent final concentration if you plan to store diluted antibody longer than a week. Do not store in frost-free freezers where temperature cycling accelerates degradation. If signal drops unexpectedly, prepare a fresh aliquot before troubleshooting other variables.

What controls should I include when validating PAPPA2 signal?

Run a positive control such as conditioned medium from PAPPA2-transfected HEK293 cells, pregnancy serum, or lysate from human osteoblasts. Include a negative control—either a PAPPA2-knockout cell line if available or a tissue known not to express PAPPA2, such as liver or brain under basal conditions. A blocking-peptide competition experiment, pre-incubating antibody with the immunogen peptide, confirms specificity. For tissues where PAPPA and PAPPA2 might coexist, siRNA knockdown or parallel blots with a PAPPA-selective antibody help distinguish the two proteases. Molecular-weight markers spanning 150 to 250 kDa are essential for confident band assignment.