Technical FAQs

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.

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

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.

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

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.

It is different from case to case. For some applications, small tags, such as His-tag and FLAG-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.

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.

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.

Yes, we provide customized formulation service. Please contact us (mail to: to submit your request.

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.

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

Normally we determine the concentration of proteins by measuring their UV absorbance. We also use BCA, SDS-PAGE, HPLC and other methods to quantify the proteins.

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.

The ED50 is defined as the cytokine concentration at which the activity is 50% of the maximum response. The formula for converting the activity as an ED50 in ng/ml to specific activity in units/mg is: Specific Activity (Units/mg) = 1,000,000 / ED50 (ng/ml)

The bio-activity data is mentioned on our datasheet. If there's no activity information on the datasheet, please contact us (mail to: to obtain further information.

Our products are used for many different purposes, so it would be impossible to predict every possible application. Our standard bioassay is used to confirm an accepted activity level for the product. Our proteins can be used at a broad concentration range, in many different applications, thus, it is the scientist’s responsibility to determine the concentrations that work best for their specific assays.

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.

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

Please contact us (mail to: to obtaint the sequence information for the protein of interest.