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 deltaT(t)-mechanism in cross-linked macroscopic polypentapeptide (PPP) films. In the literature, the responsible element of conformation in such polypeptides is described as a beta-spiral and the deltaT(t) effect is explained as a sudden change of macroconformation of single polypeptide molecules from an extended but not regular state below a transition temperature T(t) to the beta-spiral above T(t). We examined the secondary structure of the linear PPP C(GVGVP)6 in solution with DSC, CD, UV absorption, FTIR and NMR spectroscopy. The results suggest that the beta-spiral is not present in the conformational structure of the PPP molecules. The antiparallel beta-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.