Frequently Asked Questions about Our Products
Q: I just received your product and it was shipped at room temperature. Is the product ok to use?
A: Yes. Most of our products are formulated into a stable buffer and then lyophilized for long term storage and stability. Upon reconstitution it is recommended that the product be aliquoted into working volumes and stored at -20 degrees. Adding a carrier protein such as HSA or BSA will help protect the protein and prevent the product from sticking to the wall of the vial. It is important to avoid repeated freeze thaw cycles as this can damage the protein and render the product inactive.
Q: When I opened the vial, I don’t see anything. How do I know there is protein in the vial?
A: Most of our products are lyophilized with a low concentration buffer and we do not add carrier proteins (BSA, HSA, sucrose, mannitol, etc.), so the few micrograms of product may not be very visible. It is recommended to spin the vial before opening to ensure the product is not near the cap, and to carefully follow the reconstitution instructions.
Q: Your datasheet states the biological activity as an ED50. What is the Specific Activity?
A: The ED50 is an expression of activity at 50% of it’s maximum response. Specific activity is just another way of conveying the activity of the protein. To calculate a specific activity, divide 1 x 106 by the ED50 in ng/ml.
Specific Activity (Units/mg) = 1 x 106 / ED50 (ng/ml)
Q: I’m thinking of changing our supplier of cytokines. How do I know if your products are of equal or better quality than the competition?
A: All of our products go through rigorous quality control testing. Our QC testing includes the following:
- Endotoxin levels determined by LAL methods to be less than <0.01ng/ug or <0.1EU/ug.
- Most products are great than 95% pure based on SDS-PAGE and analytical HPLC.
- Depending on the characteristics and properties of each protein, protein content is determined by one or more of the following methods: SDS-PAGE, analytical HPLC and A280.
- Each protein is tested for biological activity based on the proteins known activity information. In some cases there may not be a known assay for some products, especially those that are very new to the research community.
- We are always willing to provide a sample to any research lab that would like to compare our products side by side with the competition.
Q: I want to try to do an experiment with your protein, but the bioassay you use for determining activity is not the same as my application. Will my application work with your protein?
A: Our products are used for many different purposes, so it would be impossible to predict every possible usage. Our standard bioassay is used to confirm an accepted activity level for the product. There is a lot of information in the literature that may help you decide if your experiment will work.
Q: Do most proteins show cross-species activity?
A: Most human cytokines will respond nicely in mouse cell lines, and many mouse proteins will show activity on human cells, but the activity level may be lower. Some products are very species specific and require the same species cell line to show activity.
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