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Guardian Peroxidase Conjugate Stabilizer-Diluent

Store and protect the activity of very dilute HRP conjugates, even to 10ng/mL.

Guardian Peroxidase Stabilizer-Diluent

Thermo Scientific Guardian Peroxidase Stabilizer-Diluent preserves the functional integrity and activity of horseradish peroxidase conjugated antibodies and other proteins at very dilute concentrations for long-term storage.

With Guardian Stabilizer-Diluent, typical 1mg/mL antibody or streptavidin peroxidase conjugates can be diluted as much as 100,000-fold for storage at 4°C. Most ELISA and blotting applications for HRP conjugates require dilution of typical 1mg/mL stocks by at least 1000-fold (to 1µg/mL). Sensitive assay systems, such as with chemiluminescent substrates, often require dilution up to 100,000-fold (10ng/mL). The Guardian Solution enables these 1X working concentrations of HRP conjugate to be prepared in advanced and stored at 4°C for 12 months or at room temperature for six months.


  • Preserves HRP activity – no significant loss of HRP activity over a six-month period at room temperature (1:1000 dilution) or 12 months at 4°C
  • Convenient – store ready-to-use dilutions (1:1000 to 1:100,000) that maintain enzyme activity in the refrigerator – no aliquoting or freezing
  • Assay compatible – simply add your favorite blocking buffer to create the ideal diluent for your HRP-based ELISA system or store the HRP conjugate as a 1:1000 stock solution for Western blots and dilute in the final assay buffer
  • Saves money – less expensive than competitor formulations or ordering new HRP conjugates

Product Details:

Typical colorimetric ELISA procedures requires that 10mL of HRP-conjugated secondary antibody be diluted 1000- to 5000-fold from a 1mg/mL stock solution. That necessitates pipetting 2 to 10µL of stock into a tube with 10mL of diluent. More sensitive assay systems, such as Western blots with Thermo Scientific SuperSignal West Pico, Dura or Femto Chemiluminescent Substrates for HRP, require a second round of dilution to achieve the needed working concentration of HRP conjugate. With Guardian Stabilizer-Diluent, HRP conjugates can be pre-diluted and stored at concentrations that are either ready to use or easily diluted 10- to 100-fold for final use. Preparing larger volumes of pre-diluted stocks ensures consistency and greater accuracy for assays performed repeatedly day after day.

Guardian Stabilizer-Diluent is ideal as an assay diluent for ELISA and solution-based assays. In most situations, the HRP conjugate can be stored in Guardian Solution at the final working concentration needed for the assay. For blotting applications, it is usually best to prepare a concentration for storage that can be diluted 10-fold in assay buffer (which may contain blocking components) for final use.

HRP conjugate stability in Guardian Diluent
Dilute secondary antibody stable for three months at 37°C. An ELISA assay was performed using Anti-rabbit IgG antibody coated plates (white opaque) blocked with SuperBlock Blocking Buffer (Part No. 37535). Goat anti-rabbit HRP that had been stored in Guardian Stabilizer-Diluent at a 1:100,000 dilution was further diluted to 1:5,000,000 in TBS and SuperBlock Buffer to perform the stability assay. The conjugate (1:5,000,000) was incubated in each well for one hour at room temperature and then wells were washed three times with TBS buffer. Bound antibody-HRP conjugate was detected using 100µL of SuperSignal ELISA Femto Substrate (Part No. 37075). Storing an antibody-HRP conjugate for 84 days at 37°C is equivalent to storing the conjugate for 24 months at 4°C or nine months at room temperature.


Guardian Stabilizer-Diluent with Streptavidin-HRP conjugate Northern blot using stabilized, diluted streptavidin-HRP conjugate. A Northern blot of serial dilutions of total yeast RNA (5µg, 2.5µg, 1.25µg and 0.625µg) was performed to measure TCM1 gene expression. A biotinylated TCM1 cRNA probe was hybridized and detected using the North2South Chemiluminescent Hybridization and Detection Kit (Part No. 17097). The blot was then exposed to film for 25 minutes. The Streptavidin-HRP conjugate used for generating the signal had been stored at 10µg/mL in Guardian Peroxidase Stabilizer-Diluent (for several months at 4°C) and was further diluted (1:300) to perform the Northern blot assay.


Guardian Peroxidase Stabilizer-Diluent is better
Better HRP-conjugate stability with Thermo Scientific Guardian Stabilizer-Diluent. Streptavidin-HRP (1mg/mL) was diluted 1:1000 and stored at 50°C in Guardian Stabilizer-Diluent (Ours) or another supplier's HRP stabilizer (Theirs). At each time-point, the HRP conjugate was diluted to 1:5,000,000 with PBS/SuperBlock Blocking Buffer and incubated for one hour in a white plate that had been coated with biotinylated BSA. The plate was then washed three times with 200µL PBS-T. SuperSignal ELISA Femto Substrate (100µL) was added to the plate and incubated for one minute and then measured in a luminometer. Samples at each time-point were compared to control (i.e., HRP conjugate that had not been stored in diluted form). Storing enzymes at 50°C for two weeks is equivalent to 12 months at 4°C.

Related Products:

Other HRP conjugate stabilizers and anti-freeze solutions
Protein Stabilizing Cocktail
Blocking Buffers for ELISA and Western blotting

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
37548 Guardian Peroxidase Conjugate Stabilizer/Diluent 200mL Product Instructions for product #37548 Guardian Peroxidase Conjugate Stabilizer/Diluent MSDS for product #37548 Guardian Peroxidase Conjugate Stabilizer/Diluent Certificate of Analysis for product #37548 Guardian Peroxidase Conjugate Stabilizer/Diluent $105.00

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37552 Guardian Peroxidase Conjugate Stabilizer/Diluent 1L Product Instructions for product #37552 Guardian Peroxidase Conjugate Stabilizer/Diluent MSDS for product #37552 Guardian Peroxidase Conjugate Stabilizer/Diluent Certificate of Analysis for product #37552 Guardian Peroxidase Conjugate Stabilizer/Diluent $299.00

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37552B Guardian Peroxidase Conjugate Stabilizer/Diluent Custom MSDS for product #37552B Guardian Peroxidase Conjugate Stabilizer/Diluent Certificate of Analysis for product #37552B Guardian Peroxidase Conjugate Stabilizer/Diluent

Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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