The structure and energetics of helix formation by short templated peptides in aqueous solution .3. Calculation of the helical propagation constant s from the template stability constants t/c for Ac-Hel(1)-Ala(n)-OH, n=1-6

From t/c values measured at 25 degrees C for the series Ac-Hel(1)-A(n)-OH, n = 1-6 in D2O the helical propagation constant (s value) for alanine in this templated peptide series is 1.03; the corresponding value in 10 mol % trifluoroethanol-D2O is 1.47. An iterative least squares analysis for calculating s values from t/c ratios is developed, errors implicit in its application are discussed, and the s value is related to the degree of helical fraying.