I purchased Thermo Scientific Pierce Streptavidin- Horseradish peroxidase conjugated and in the product data sheet its explained that you can reconstitute it with NF water, but avoid repeated freezing and thawning and as i use 1 uL per essay i cannot make such smalls aliquots for that. That´s why I was looking for a buffer that could preserve my hrp ;) Thank you in advance
You may dissolve the conjugate in a storage buffer with 50% (v/v) glycerol as a cryoprotector, and keep this stock at (-20)oC, it should not freeze. For example:
"... HRP (93% isoenzyme C) was purchased from Roche (Indianapolis, IN) and analyzed by MALDI (Applied Biosystems Voyager DE-PRO). Phosphate buffered saline (PBS) (2.7 mM KCl, 1.5 mM KH2PO4, 136 mM NaCl, 8.1 mM Na2HPO4, pH 7.3) was used as the buffer system. HRP was reconstituted to 100 μM in 50:50 PBS/glycerol and stored at −20 °C. Glycerol (Invitrogen, ≥99.5% pure) was added to prevent freezing of the stock solution ..."
(reference: "Mechanistic Aspects of Horseradish Peroxidase Elucidated through Single-Molecule Studies", Hans H. Gorris, David R. Walt. Am. Chem. Soc. 2009, 131, 17, 6277–6282)
1uL per assay is such a small volume that can introduce large error in your assay. After reconstitution with NF water, make an intermediate dilution of the HRP-Streptavidin in phosphate buffered or Tris buffered saline. pH 7.4 containing 10mg/mL BSA ( for example 1/10dilution or 1/100 dilution then use it in your assay at 10uL or 100uL volume). I have kept streptavidin-HRP solution diluted in the above buffer for over 3 years at 4oC without loss of activity. Make sure you do not use sodium azide as preservative as it inhibits HRP enzyme activity. I recommend using Proclin 300 (Sigma-Aldrich) at 1/1000 dilution.
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