Can you provide the shelf-life for the Pierce Cell Surface Protein Isolation Kit?
The Pierce Cell Surface Protein Isolation Kit is covered under our general 1-year warranty and is guaranteed to be fully functional for 12 months from the date of shipment, if stored as recommended. Please see section 8.1 of our Terms & Conditions of Sale (https://www.thermofisher.com/content/dam/LifeTech/Documents/PDFs/Terms-and-Conditions-of-Sale.pdf) for more details.
Can I use conjugated streptavidin to detect proteins isolated with the Thermo Scientific Cell Surface Protein Isolation Kit following my Western blot transfer?
No. As a cleavable biotin is used to release the labeled proteins from the NeutrAvidin Agarose in a relatively gentle manner, incubation of the labeled proteins on the NeutrAvidin Agarose with a reducing agent will cleave the disulfide bond in the spacer arm of the biotinylation reagent, leaving the biotin on the NeutrAvidin Agarose, and allowing the protein to be recovered free of the biotin tag.
If I want to obtain a higher level of labeling of my cell surface molecules is it okay to increase the concentration of the Sulfo-NHS-SS-Biotin?
No. Biotin is a small compound and high concentrations can behave similar to high concentrations of salt, compromising the cell membrane and allowing proteins to escape from the cell's interior. We do not recommend using a concentration higher than 0.25 mg/mL of the Sulfo-NHS-SS-Biotin when labeling surface proteins.
Why does the Thermo Scientific Cell Surface Protein Isolation Kit include a cleavable version of water soluble biotin?
The biotinylation reagent is water soluble to prevent it from passing through the cell membrane and labeling proteins on the interior of the cell. This reagent is cleavable in order to allow release from the NeutrAvidin Agarose. NeutrAvidin, which is deglycosylated avidin, has the same binding affinity for biotin as does avidin (Kd = 1.3 x 10-15 at pH 5), which is often considered the strongest non-covalent interaction known. Conditions required to release the biotin from the NeutrAvidin do so by irreversibly denaturing the NeutrAvidin protein, as well as most other proteins. Cleavage via reduction with a sulfhydryl-containing compound is a much gentler recovery method for the labeled cell surface proteins.