Conformational properties obtained from H-1 NMR, CD, and molecular mechanics analysis are reported for Ac-Hel(1), an N-terminal helix-inducing template for polypeptides. The conformational state ratio [ts]/[cs] of Ac-Hel(1) is shown to be 0.79 +/- 0.14 in water and in trifluoroethanol-water mixtures. The rate of (t)-(c) state equilibration and the sensitivities of the ([ts] + [te])/[cs] state ratio to salt, temperature, and TFE concentration are reported. The [t]/[c] state ratio is shown to be a reliable monitor of stability of peptide structure induced by Ac-Hel(1).