Before releasing our cytokines and cytokine products for sale they are thoroughly analyzed to ensure the following qualities:
Authenticity: by N-terminal sequence analysis and, when possible, by SDS PAGE, RP-HPLC, and Mass Spectrometry analyses versus standards.
Purity: by SDS-PAGE and RP-HPLC analysis
Biological Activity: by the relevant in vitro or in vivo bioassay.
Protein content: by UV spectroscopy, SDS-PAGE analysis and, when possible, by HPLC analysis versus the calibrated standard solution.
Endotoxin contamination: by kinetic LAL method.
Microbiological contamination: by membrane filtration method; protein solutions are sterile-filtered prior to vialing.
What should I know about the stability of your protein products?
Unless otherwise mentioned on the product information sheet, all of our products are formulated in such a manner that the lyophilized proteins are very stable at room temperature. However, we recommend storing lyophilized products at -20癈. For reconstituted solutions of most products, we recommend short-term storage at 4癈. For longer term storage the protein solution should be stored with a carrier protein (eg. 0.1%BSA) in working aliquotes and stored frozen at -20癈. Please keep in mind that every freeze/thaw cycle may cause some denaturation of the protein.
Which cytokines show cross-species activity?
With a few exceptions, most human cytokines are active on mouse cells. Many mouse cytokines are active on human cells, but may show lower specific activity than the corresponding human cytokine. A few human cytokines, such as IL-7, even exhibit higher specific activities on mouse cells than do the corresponding mouse cytokines. The interferons, GM-CSF, IL-3, and IL-4 are known to be species-specific with very little, if any, activity on non-homologous cells. In contrast, the FGF's and neurotrophins are very highly conserved and show excellent activity on cells of other animal species.
How do I convert kDa to grams/mol?
Molecular weight of our proteins was listed in kDa on the datasheets. The approximate conversion to molar mass is 1 dalton = 1 gram/mol. As an example, an 8 kDa protein would be 8000 grams/mol.
What grade BSA is used for the reconstitution of EZ Biosystems cytokines?
EZ Bioystems uses a Fraction V BSA, Very Low Endotoxin (Millipore, Catalog # 81-068) for protein reconstitution. It is recommended that customers use the same or equivalent.
Why should I reconstitute the cytokine in PBS/BSA if it is lyophilized from the same solution?
The additional BSA in the reconstitution buffer will aid in the recovery of the cytokine as well as add additional stability. The volume of PBS with which the product is lyophilized is generally very small. Therefore, PBS reconstitution does not significantly increase the salt concentration when reconstituted according to the datasheet. Presence of additional salt in the stock does not interfere in an assay when diluted to the working concentration. Please contact Technical Service if the volume of PBS prior to lyophilization is a concern. Because products are Quality Control tested in the manner stated on the data sheet, EZ Biosystems cannot guarantee the performance of products not reconstituted as described in the data sheet.