A template-induced incipient collagen-like triple-helical structure

In this communication, we report the use of a conformationally constrained organic template to induce collagen-like triple helical structures composed of Gly-Pro-Hyp sequences. This template, cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid (known as the Kemp triacid, KTA), possesses three carboxyl groups which can be coupled to the N-terminal of three peptide chains. We insert as a spacer between each peptide chain and each carboxyl group on KTA to compensate for the difference in diameters between the KTA and the collagen triple helix and to facilitate the synthesis. On the basis of the NMR and optical rotation results we can conclude that KTAg-3,3 forms a triple-helical conformation in H2O with a melting temperature of 30°C. We believe this compound represents the shortest chain polypeptide able to form a triple helical structure at room temperature in H2O reported to date. This compound will be useful as a model system for the study of the stages of triple-helix folding. Therefore, we denote this borderline ordered structure as an incipient triple helix.