Correlation between computed conformational properties of cytochrome c peptides and their antigenicity in a T‐lymphocyte proliferation assay

By means of conformational energy calculations, we previously showed that the antigenic strength of a series of oligopeptides (derived from the carboxyl terminal sequence of cytochrome c) in a T‐lymphocyte proliferation assay depends on their ability to adopt the α‐helix conformation. Using experimentally determined statistical weights (within the framework of the Zimm–Bragg theory for the helix–coil transition), here we present a simple free energy analysis of the ability of these peptides to adopt the α‐helix conformation in water. The experimental statistical weights have been modified to include the effect of long‐range charge–dipole interactions on helix stability. We find that there is a close correlation between the tendency of a peptide to adopt the α‐helix conformation and its ability to stimulate antigen‐primed T cells. The shortest peptide with a tendency to adopt the α‐helix conformation is also the shortest one that exhibits antigenic activity. The rapid and simple method presented here can thus be used to predict relative antigenicities for different peptides derived from cytochrome c.