Anti-MMP-21 Rabbit Polyclonal Antibody

Frequently Asked Questions

What is the expected molecular weight of MMP-21 on a Western blot?

MMP-21 is a 569-amino-acid protein with a predicted molecular weight of approximately 63 kDa for the full-length form. However, as a secreted metalloproteinase, MMP-21 undergoes proteolytic processing that removes the N-terminal propeptide during activation. Depending on your sample type and cell state, you may observe the full-length zymogen around 63 kDa, the mature catalytically active form around 52–54 kDa, or both. Glycosylation can also shift the apparent MW upward by 2–5 kDa. We recommend loading 20–40 µg total protein per lane and starting with a 1:1000 dilution of this antibody for initial detection.

Does MMP-21H antibody cross-react with other MMP family members?

MMP-21 shares only 30–40 percent sequence identity with classical collagenases and gelatinases, which reduces the likelihood of cross-reactivity compared to closely related MMPs like MMP-1, -8, and -13. This polyclonal antibody was raised against a recombinant fragment spanning a substantial portion of MMP-21, and our validation in human lysates shows a single dominant band at the expected MW. We have not observed cross-reactivity with MMP-1, -2, -9, or -14 in side-by-side Western blots. That said, if you are working with tissues or cells expressing multiple MMPs, include a known MMP-21-negative cell line as a specificity control.

What dilution should I use for immunohistochemistry with MMP-21H antibody?

While this antibody has been validated for Western blot at 1:1000, IHC typically requires empirical optimization depending on your fixation method, antigen retrieval, and detection system. A reasonable starting range for IHC is 1:100 to 1:400. We recommend citrate-based antigen retrieval (pH 6.0, 20 min sub-boiling) for formalin-fixed paraffin-embedded tissue. MMP-21 is secreted and may show diffuse extracellular staining in addition to cytoplasmic signal in producing cells. Include a no-primary-antibody control and, if possible, a tissue known to express MMP-21 such as embryonic heart or kidney to confirm specificity.

Is MMP-21 expression limited to embryonic tissues or can I detect it in adult samples?

MMP-21 is most prominently expressed during embryogenesis, particularly in the context of left-right axis determination and organogenesis. Expression drops sharply in most adult tissues, though low-level transcripts have been reported in skin, kidney, and some epithelial compartments. If you are working with adult human or rodent lysates, expect weak or undetectable signal unless you enrich for epithelial cells or examine regenerating tissues. Embryonic day 9.5–12.5 mouse embryo lysate serves as a good positive control. For adult studies, consider qPCR to confirm MMP21 mRNA before committing to Western blot or IHC.

Can I use this antibody to detect mouse or rat MMP-21?

The antibody has been validated in human samples and shows predicted cross-reactivity with mouse and rat orthologs based on sequence homology in the immunogen region. Human and mouse MMP-21 share approximately 75 percent amino-acid identity, which often supports polyclonal antibody recognition. We have preliminary data suggesting successful detection in mouse embryo lysate, but you should validate performance in your specific model system. Start at 1:1000 for Western blot and include a known positive control such as whole-embryo lysate at embryonic day 10.5–12.5. If signal is weak, increase lysate load before raising antibody concentration to preserve specificity.

What sample preparation considerations are important for detecting MMP-21?

Because MMP-21 is secreted, you can detect it in both cell lysates and conditioned medium. For lysates, standard RIPA buffer with protease inhibitors works well; include EDTA or 1,10-phenanthroline to inhibit MMP autocatalysis during sample handling. If harvesting conditioned medium, serum-free or low-serum conditions minimize albumin contamination. Concentrate conditioned medium 10- to 20-fold using centrifugal filters (10 kDa cutoff) to achieve detectable signal. MMP-21 is sensitive to freeze-thaw cycles; aliquot samples and avoid repeated thawing. For tissues involved in laterality or NOTCH signaling studies, microdissection of the relevant embryonic structures improves signal-to-noise over whole-tissue homogenates.

How should I store the MMP-21H antibody to maintain long-term stability?

Store the antibody at –20°C in small aliquots to avoid repeated freeze-thaw cycles, which can reduce titer and increase aggregate formation. The antibody is supplied as a polyclonal rabbit serum or purified IgG in a buffer containing glycerol and a preservative, which provides reasonable stability for 12–18 months when stored correctly. For convenience, you may keep a working aliquot at 4°C for up to one month, but return it to –20°C for longer intervals. Do not store diluted antibody; prepare fresh working dilutions in your blocking buffer on the day of use to maintain optimal performance and minimize bacterial contamination.

What positive and negative controls should I use when working with MMP-21H antibody?

An ideal positive control is lysate or tissue from a system known to express MMP-21, such as embryonic mouse heart or kidney at E10.5–12.5, or a human cell line overexpressing MMP21 if available. For negative controls, use a cell line or tissue confirmed to lack MMP21 mRNA by qPCR—adult tissues from most organs qualify, given the developmental restriction of MMP-21. Additionally, pre-incubating the antibody with recombinant MMP-21 blocking peptide can serve as a competition control to confirm specificity. Because MMP-21 regulates NOTCH signaling, consider comparing signal before and after pathway activation as a functional validation step.