Jürgen Engel, J. Kurtz, Ephraim Katchalski
May 1, 1966
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Journal
Journal of molecular biology
Abstract
An ordered sequence polymer of the structure H(Pro.Gly.Pro)n OH was synthesized as a collagen model. Fractionation by gel filtration gave samples of average molecular weights between 1000 and 12,000. The polymer showed in aqueous solution ordered (helical) conformation which could be destroyed by heating or by the addition of a number of salts. Extent of helicity and sharpness of thermal transitions increased with increasing molecular weight. On the basis of optical rotation measurements, it was concluded that the observed structure is of the poly- L -proline II type, stabilized by co-operative hydrogen-bonding leading to side-to-side association of chain sections. The resulting structure is probably the triple-stranded helix observed in the solid state with this polymer, but alternatives (anti-parallel arrangement, double-strand structure) could not be excluded. The results obtained show that the replacement of every third proline residue in poly- L -proline by a glycine residue, thus introducing one CONH group per tripeptide unit, is sufficient to stabilize a collagen-like structure in solution as well as in the solid state.