top of page

Frequently Asked Questions

Recombinant Proteins

1. What are the endotoxin levels?

Less than 0.1 ng/µg (1 IEU/µg) as determined by LAL test.

2. What are the purity levels?

Greater than 95% for most proteins as determined by reducing SDS-PAGE. The actual purity will show in CoA.

3. What are the storage conditions for proteins in lyophilized form?

Lyophilized proteins should be stored at < -20°C, though stable at room temperature for three weeks. Reconstituted protein solution can be stored at 4-7°C for 2-7 days. Aliquots of reconstituted samples are stable at < -20°C for 3 months.

4. What are the storage conditions for proteins in liquid form?

Store at ≤-70°C, stable for 6 months after receipt. Store at ≤-70°C, stable for 3 months under sterile conditions after opening. 

5. What is the reconstitution instruction for a lyophilized protein?

Always centrifuge tubes before opening. Do not mix by vortex or pipetting. Dissolve the lyophilized protein in ddH2O. It is not recommended to reconstitute a concentration less than 100 µg/ml. Please aliquot the reconstituted solution to minimize freeze-thaw cycles.

6. What is the shelf-life? And how do you measure it?

We do not determine the shelf-life of recombinant proteins, since the proteins can be stable for multiple years under recommended storage conditions. Instead, we provide the warranty on our proteins for 6-12 months upon the date of receipt. Information can be found on the CoA. Our lab also conducts routine QC testing to ensure the quality of protein at the time of sales.

7. What is the mammalian expression system you use?

We use human cells in most cases. However, this might not apply to all proteins, as we always select the best expression system for each protein. Please inquire for details.

8. What is the plasmid transfection method you use?

We use liposome-based transfection for all our recombinant proteins.

9. Does it contain DNA with animal or human origin?

No, It doesn't.

10. Have you done any test to verify the activity of the protein?

We have tested the activity for some proteins and the list of tested protein is expanding. Please inquire to know whether it is tested or not.

11. How do I know if the protein you made works for my project if you haven’t tested its activity yet?

While we haven't tested and thus couldn't guarantee the activities for some proteins, over 90% of our selling proteins are working well for the customers. We design and manufacture in the best strategy to ensure all of the proteins are soluble with high purity. We also offer free samples to help customers test the performance before ordering a large amount.


For any additional questions regarding our recombinant protein products, kindly reach out to a team representative.

bottom of page