The binding affinity and dissociation rates of peptides for class I major histocompatibility complex molecules

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Abstract
Peptides of various lengths derived from the influenza nucleoprotein (NP) bind to H‐2Db class I molecules with affinities at 4 °C between ∼3 × 105‐∼3 × 107 M−1. The peptide with the highest affinity corresponds to the sequence of nine amino acids (NP366–374) recently isolated from cells infected with influenza. This peptide forms stable complexes with half‐lives > 110 h at 4 °C, 39 h at 22 °C and 3 h at 37 °C. Small increases in length of the peptide greatly reduce the stability of the complex (t1/2 ∼1–10 h at 4 °C). These results may explain the homogeneous length of peptides isolated from class I molecules formed in vivo, and suggest that class I and II may differ in their dependence on the length of peptides for the formation of stable complexes.