Technical Questions

  1. How do you calculate an enzyme’s purity?
    For all of our products we run SDS-PAGE gel with a titration of the enzyme, followed by the densitometry measurement to determine the purity.
  2. Where do I find the sequence of the protein?
    To request the sequence information for the protein of interest please contact us.
  3. How much enzyme should I use for my assay?
    An enzyme titration curve and calculated specific activity are included in the data sheet of each active enzyme. It is recommend that the researchers perform a serial dilution of an enzyme product to determine the optimal amount to use in their own assay systems.
  4. How do you calculate a protein’s concentration?
    The concentration of each of our products is calculated from a titration on SDS-PAGE gel with a standard curve of the Bovine serum albumin (BSA) or the Bovine gamma globulin (BGG).
  5. Do you offer the enzymes at a higher concentration?
    Yes, we may provide enzymes at a higher concentration. Please contact us to obtain more detailed information.
  6. Can I purchase proteins with different buffer formulation?
    Yes, we can supply our protein in a customized buffer formulation. Please contact us to submit your request.
  7. What is the difference between active and unactive proteins?
    SignalChem’s active enzymes are produced using specific treatment or conditions to achieve optimal activity in vitro, while unactive proteins are generally produced without any stimulation or from prokaryotic systems so the enzymes only show minimal basal activity. Active enzymes can be directly used in biochemical assays for compound screening or enzymatic studies. Unactive proteins can be used as substrates, negative controls, or to study activation of the particular enzymes in vitro.
  8. How are your enzymes activated?
    SignalChem’s active enzymes are activated using specific protocols during the process of expression and production to achieve optimal post-translation modification and in vitro activity. The treatment methods may vary for different enzymes depending on their functional roles.
  9. Do you express proteins with any tags other than HIS and GST?
    Yes, we do customize the proteins with other tags (e.g. FLAG, Fc). Please contact us for the detailed information.
  10. Do you offer untagged proteins?
    Yes, we can customize the protein as per your requirements. Please contact us to submit your query.
  11. How do I find information on the tag cleavage site for my protein?
    Please contact us to obtain the details for tag cleavage site.
  12. Why are some of your recombinant proteins expressed in E.coli cells while others in Sf9 insect cells?
    The expression system of each recombinant protein is selected based on that products respective function and application.
  13. Are your enzymes suitable for crystallography studies?
    SignalChem’s active enzymes are validated for in vitro activity assays. We offer a wide range of custom services including additional purification steps, buffer exchange, and tag modification to fulfill the requirements for other applications such as protein crystallography. Please contact us find more information about this service.
  14. I want to use the protein for binding studies. Which protein type do you recommend – Active Enzyme or Recombinant Protein?
    SignalChem’s active enzymes and recombinant proteins both may work in binding assays. We recommend clients to test the compatibility of a product in their assay system. contact us to request a free sample.
  15. Do you determine the Km values of the protein?
    SignalChem offers Profiling Services for enzymatic studies including Km determination. Please click here to find more information about this service.
  16. What is the level of phosphorylation of your Active Kinases?
    Generally active kinases are phosphorylated on certain sites in their catalytic domain. However, the number of total phosphorylation sites from each active kinase may vary. We do not perform any test to probe for specific phosphorylation in our kinases.
  17. How do I know whether or not certain key residues in the protein are phosphorylated?
    Phosphorylation of a certain residue can be determined by Western Blot or ELISA using phospho-specific antibodies.