Before revision: Without the Strep-Tactin backbone, the single MHC-Strep-tag fusion proteins spontaneously distatch from the TCR of the T cell, because of weak binding affinities (monomeric MHC-epitope complexes cannot provide stable binding, see above).
After revision: Without the Strep-Tactin backbone, the single MHC-Strep-tag fusion proteins spontaneously detatch from the TCR of the T cell, because of weak binding affinities (monomeric MHC-epitope complexes cannot provide stable binding, see above).