Schbio Biotech

Technical FAQs

1. Why can't I see the protein pellet in the vial?

Small amounts of protein can be deposited on the vial during lyophilization as a thin and, sometimes, invisible film. Please centrifuge vial prior to opening to ensure the product is not near the cap or on the side of the vial. Our quality control procedures assure that each vial contains the correct amount of product.

2. How do you calculate the purity of the protein?

For all of our products we run SDS-PAGE gel to determine the purity. HPLC is doable upon request.

3. Why is the actual western blot band size different from the predicted?

Western blotting is a technique that separates proteins based on size. In general, the smaller the protein the faster it migrates through the gel. However, migration is also affected by other factors, such as splice variants, PTM, relative charge, multimers, etc.

4. How do I find information on the tag cleavage site for my protein?

Please contact the technical support (mail to: to obtain the details for tag cleavage site.

5. Why are some proteins fused to tags?

The initial use of protein tags is for protein purification purpose. In addition, tags are also used for protein detection in several applications, such as western blot and ELISA, when the specific antibodies are not available. Furthermore, some tags stabilize molecules, which may increase the half-life of the products. Fc-tag also helps the protein, particularly receptors, to form biologically active dimers.

6. Do protein tags affect protein activity?

It is different from case to case. For some applications, small tags, such as His-tag, may not affect protein activity and do not need to be removed. You could also contact us (mail to: to obtain the activity information of the item of interest.

7. Why are the proteins lyophilized? How will lyophilization affect the characteristics of the proteins?

Lyophilization (freeze-drying) technique is applied to increase the stability and shelf life of proteins, and decrease shipping cost. Lyophilization may cause loss of activity or aggregation of proteins. But addition of protectants (stabilizers, additives, excipients) and proper control of lyophilization conditions will minimize the adverse effect for most proteins.

8. Why are protectants added to protein solutions before lyophilization? What protectants do you add to your products?

Protectants (stabilizers) are added to protect proteins during lyophilization and/or long-term storage. Proteins are subjected to various stresses generated by lyophilization which may cause loss of activity, aggregation, or denaturation. We use trehalose and mannitol (normally 8% w/v) as protectants for lyophilization.

9. How do I reconstitute or dilute the protein?

If the protein is lyophilized you should use our reconstitution recommendations in the data sheet provided. If the protein is liquid form, we recommend to further dilute the protein using the same formulation as published in our data sheet.

10. How do you determine the quantity of your proteins?

Normally we determine the concentration of proteins by using SDS-PAGE, HPLC , ELISA, SRP and other methods to quantify the proteins.

11. Why is the quantification of the protein generated by my assay different from the one on the label?

Different assays generate different quantification result. Sometimes the discrepancy can be significant if you conduct a different assay. It is also possible that the protein forms aggregations during storage which causes loss after reconstitution and centrifugation. We run quality control tests for each batch of proteins. However, it is still inevitable that a few vials are not the same with the rest of the same batch. This happens very rare and can be minimized by our effort on Quality Control.

12. How should I store the products?

Lyophilized proteins are stable for at least twelve months from date of receipt when stored at -20℃ to -70℃. Upon reconstitution, the proteins can be stored at 2℃ - 8℃ for at least 1 month without detectable loss of activity. It is recommended to aliquote and store the reconstituted protein at -20℃ to -70℃. Avoid repeated freeze-thaw cycles.

13. Do you supply Material Safety Data Sheets (MSDS) for your products?

Yes, please contact us (mail to: to submit your request.

14. Where do I find the sequence of the protein? Please contact us (mail to: to obtaint the sequence information for the protein of interest.

15. Can I get a free sample of a product?

We can offer 10 μg product in stock to you as a free sample. As a premise, you need to feedback the experiment data to us.

16. Can I get a discount?

You can get discount through the following ways:
a. Promotions on the home page. b. Order much enough products to get discount.