Effect of substitution of D-alanine for L-alanine on activity and conformation of an encephalitogenic peptide.

Synthetic peptides Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys and its D-Ala analog were tested for induction of experimental allergic encephalomyelitis (EAE) in guinea pig. The L-Ala peptide was highly active at 0.5 μg dosage and the D-Ala peptide was inactive even at 10 μg dosage. NMR spectra indicated backbone conformational differences between the two isomers. Energy calculations delineate conformations that are high in energy for the D-form and low for the L-form. A conformation for the physiologically active peptide is suggested that is in accord with both clinical and physical data.