• Activity-related FAQs

    1. In the instruction manual, it says touse acid to reconstitute. Would that affect the activity of the protein or thecells during experiment?

    The reconstitution buffer recommended inthe instruction manual is selected since it has good solubility and ensure thatthe activity of the protein remains intact. When using the protein, the smallamounts of acid present in the reconstitution buffer will not affect theresults of the experiment.

    2. When using ED50 or units/mgstandards to compare specific activity, is there correlation orinter-conversion between the two parameters?

    ED50 is defined as theconcentration that can produce a reaction 50% that of the maximum reaction.This parameter is only applicable to reagents that exhibit the “S” biologicalactivity vs. concentration graph. The formula used to convert ED50 (ng/ml) tospecific activity (units/mg) is:

    Lot No.

    Evaluated ED50

    Reported ED50




    0.16 ng/ml


    1-6 pg/ml


    0.18 ng/ml

    0.34 ng/ml

    1 pg/ml


    3. Which cell factors have cross-speciesactivity? Cross-product activity?

    Apart from a few exception, most human cellfactors have effect on mice cells. Likewise, many mice cell factors have effecton human cells. However, the effect of mice cell factors on human cells tendsto be lower than the effect of human cell factors on human cells. In addition,for IL-7 and some other human cell factors, their effect on mice cells isgreater than that produced by the corresponding mice cell factors. Interferons,GM-CSF, IL-3, and IL-4 are very species specific and have almost no effect onthe cells of other species. In contrast, fibroblast growth factors (FGFs0) andneurotrophins are highly conserved and can produce strong effects in cells fromvarious animal species. The above descriptions are mere generalizations andintended for reference purposes only. When assessing a specific cell factor,please use published journals and/or your own experimental results to obtainthe most accurate information regarding cross-species activity. 

    4. How will tag and additional amino acidsaffect protein activity?

    This question needs to be analyzed case bycase. If the experiment does not require a tag, we recommend that the customerpurchase proteins that do not contain the tag. When our company’s products havebeen purified, there are almost no excessive amino acid residues.

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