An Alternative Structure Model for the Polypentapeptide in Elastin

Polypentapeptides (GVGVP)n which are designed in analogy to the connective tissue protein elastin are reported to transform various kinds of energy into mechanical work by the so-called ⊿Tt-mechanism in cross-linked macroscopic polypentapeptide (PPP) films. In the literature, the responsible element of conformation in such polypeptides is described as a β- spiral and the ⊿Tt effect is explained as a sudden change of macroconformation of single polypeptide molecules from an extended but not regular state below a transition temperature Tt to the β-spiral above Tt. We examined the secondary structure of the linear PPPC(GVGVP)6 in solution with DSC, CD, UV absorption, FTIR and NMR spectroscopy. The results suggest that the β-spiral is not present in the conformational structure of the PPP molecules. The antiparallel β-sheet is proposed to be the basic regular part of conformation because it agrees with all spectroscopic data. As a consequence, the elasticity of natural elastin must be considered from a new perspective.