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Sequential polyhexapeptides, synthesised by combination of sequences from collagen type Gly-X-Y (X = Ala, Pro, Ser; Y = Ala, Gly, Lys, Pro), were characterized by the temperature dependence of circular dichroism spectra. Under comparable conditions these studies revealed that alternating triplets of Gly-Pro-Pro or Gly-Pro-Ala combined with Gly-Pro-Lys or Gly-Pro-Glu exhibit collagen-like structures in aqueous solutions. In case of unstructured chains of (Gly-Pro-Ala) ≈ 12 it can be shown that N-terminal crosslinking of three chains produces a similar ordered structure.

Upon use of a synthetic method reported earlier by us respective alloys of Na/Sn, Na/Ge and Na/Sb are dissolved in ethylenediamine and the title compounds precipitated from the solutions in high yield. By recrystallisation well shaped, stable crystals are obtained. The crystal structure of [Na4 · 7 en]Sn9 confirms the presence of a Sn9 4---polyhedron which had been suggested by us on the basis of other investigations. The Sn9 4--polyhedron may be described as a distorted tricapped trigonal prism. Ethylenediamine is coordinated to Na+-ions exclusively.