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      Peptide-MHCs: FAQS

      1. What is pMHC? 

      KACTUS offers a range of high-quality MHC-peptide(pMHC) complex protein products covering popular targets such as NY-ESO-1, WT-1, MAGE-A, AFP, and HPV16.  


      1. Is pMHC a single-chain design?

      KACTUS pMHCs expressed in HEK293T cells are a single-chain design of α-chain and β-2 microglobulin by our protein engineering team. KACTUS can also provide pMHC expressed in E. coli which is not single-chain design. 


      1. Is pMHC purified from mammalian cells?

      These can be expressed using mammalian cells or E. coli expression systems.


      1. How is pMHC purified?

      The pMHC is affinity purified via His tag at the C-terminus with additional size exclusion chromatography steps.


      1. What pMHC products does KACTUS provide?

      KACTUS provides pMHC monomer, biotinylated monomer, and fluorescent tetramer. 


      1. What is single-chain pMHC monomer?

      The pMHC monomer consists of α-chain, peptide and β-2 microglobulin.


      1. What is pMHC biotinylated monomer?

      It is pMHC monomer with biotin at C-terminal Avi tag.


      1. What is fluorescent pMHC tetramer?

      Fluorescent pMHC tetramer has fluorophores conjugated to each monomer subunit of the complex.


      1. How are pMHC products QC’d? 

      We analyze pMHC products by Tris-Bis PAGE, SEC-HPLC, endotoxin level, peptide-loading and functionality tests.


      1. Which fluorophores are available for pMHC tetramer?

      We currently offer APC-equivalent, FITC-equivalent and PE conjugation for pMHC tetramer.


      1. Is pMHC tetramer made by in vitro assembly by streptavidin? 

      Yes, pMHC tetramer is assembled by biotinylated monomer and streptavidin. But KACTUS also has pMHC that tetramerizes in vivo during expression in Expi293, a KACTUS propriety design.


      1. Does KACTUS provide custom pMHC I and pMHC II? 

      Yes, KACTUS provides custom pMHC I and II for all available MHC alleles. 


      1. What is the lead time for custom pMHC services?

      The lead time is 6 to 8 wks. 


      1. How do I order custom MHC?

      Go to our website and fill out a custom order request form, or email us at order@kactusbio.us  


      1. Can you provide a tetramer staining protocol using pMHC?

      Yes, contact support@kactusbio.us for a protocol.


      1. What is the shelf life of pMHC?

      pMHC can be stored for at least 12 months at -80°C.