Anti-HBP-2 Rabbit Polyclonal Antibody

Frequently Asked Questions

What is the expected molecular weight for HBP-2 on Western blot?

HBP-2 (FSAP) runs at approximately 70 kDa on reducing SDS-PAGE, corresponding to the single-chain zymogen form secreted into plasma. You may also observe a doublet or two bands at approximately 50 kDa and 27 kDa under certain conditions, representing the heavy and light chains of the activated two-chain form after proteolytic cleavage at Arg313-Ile314. The relative abundance of these forms depends on whether your sample contains active proteases or has undergone ex vivo activation. Plasma samples often show predominantly the 70 kDa form unless clotting has been initiated.

What starting dilution should I use for HBP-2 Western blot?

We recommend starting at 1:1000 dilution for Western blot based on validation data with human plasma and recombinant HBP-2. This polyclonal antibody typically yields clean bands at this concentration with standard chemiluminescent detection. If your sample has low HBP-2 expression or you are working with conditioned media or tissue lysates rather than plasma, you may need to increase antibody concentration to 1:500. Always include a positive control such as human plasma or recombinant HBP-2 to establish optimal signal in your specific detection system before troubleshooting sample-specific issues.

Does this HBP-2 antibody cross-react with mouse or rat samples?

This antibody is validated only for human HBP-2. Cross-reactivity with mouse or rat HABP2 has not been experimentally confirmed. Human HBP-2 shares approximately 70 percent sequence identity with mouse and rat orthologs, so cross-reactivity is possible but not guaranteed. If you are working with rodent samples, we recommend validating the antibody in your system using a positive control such as transfected lysate expressing mouse or rat HABP2, and confirming band identity by siRNA knockdown or peptide competition. Predicted cross-reactivity without validation should be interpreted cautiously.

Can I use this antibody for immunohistochemistry on tissue sections?

Triple Point Biologics antibodies are routinely validated for immunohistochemistry, and this rabbit polyclonal format is suitable for IHC applications. HBP-2 is a secreted plasma protein, so you should expect extracellular and vascular staining patterns in tissues such as liver, where it is synthesized, and areas of vascular injury or thrombosis. Antigen retrieval is typically required; citrate buffer pH 6.0 is a reasonable starting condition. We recommend beginning with a 1:100 to 1:200 dilution and optimizing on your specific tissue type. Include appropriate positive controls such as liver sections and negative controls including isotype-matched IgG.

What is the biological difference between HBP-2 and FSAP nomenclature?

HBP-2 and FSAP refer to the same protein encoded by the HABP2 gene. The protein was initially identified as hyaluronan-binding protein 2 based on its affinity for hyaluronic acid, but was later characterized as Factor VII-activating protease due to its ability to activate coagulation factor VII. Both names remain in active use in the literature. The UniProt entry Q14520 lists both designations. Functionally, it is a circulating serine protease involved in coagulation and fibrinolysis, with emerging roles in tumor suppression and extracellular matrix remodeling. Either name is acceptable depending on your experimental context.

What sample types work best for detecting endogenous HBP-2?

Human plasma and serum are optimal sources for detecting endogenous HBP-2, as it circulates at approximately 10 to 12 micrograms per milliliter in healthy individuals. Citrated or EDTA plasma is preferred over serum to minimize ex vivo activation. For cell culture models, HBP-2 is primarily expressed by hepatocytes, so liver-derived cell lines or conditioned media from hepatocyte cultures are suitable. Tissue lysates from liver are also appropriate. Most other cell types express minimal HBP-2 unless induced by inflammatory stimuli. If working with non-plasma samples, include recombinant HBP-2 or plasma as a positive control to confirm antibody performance.

How should I store this HBP-2 antibody to maintain activity?

Store the antibody at minus 20 degrees Celsius in single-use aliquots to avoid repeated freeze-thaw cycles, which can reduce titer and increase background. The antibody is supplied as a rabbit polyclonal in a stabilized formulation at 100 micrograms per vial. After the first thaw, working aliquots can be held at 4 degrees Celsius for up to one month if sodium azide preservative is present, but long-term storage should remain frozen. Do not store diluted antibody in blocking buffer for extended periods. If you observe increased background or reduced signal over time, prepare a fresh aliquot rather than attempting to concentrate or re-use old stocks.

What controls should I include when working with HBP-2 antibody for the first time?

Include human plasma or recombinant HBP-2 as a positive control to confirm antibody specificity and optimize detection conditions. A negative control using lysate from cells with HABP2 knocked down by siRNA or CRISPR is ideal for confirming band identity, especially if you observe multiple bands. For IHC, include tissue known to lack HBP-2 expression and an isotype-matched rabbit IgG control at the same concentration. Peptide competition using the immunogen peptide, if available, provides additional specificity confirmation. Because HBP-2 is a secreted protease, also consider whether your sample handling may have caused degradation or activation, which alters banding patterns.