Synthetic Polypeptides Related to Collagen

In addition to the stereochemical features imposed on a polypeptide chain as a consequence of the insertion of a proline residue, the imino nitrogen atom of the pyrrolidine ring is devoid of a proton and is consequently unable to participate in the formation of inter- or intrachain hydrogen bonds. This means that the regularity of any systematic, hydrogen-bonded peptide structure will be interrupted in proline-containing regions. The effect of such internal breaks on the stability of the a-helix has been considered by Schellman (1955) who demonstrated that usu- 

A complete X-ray diffraction study of this imino acid has been prevented as a result of its strongly hygroscopic character. However, Mathieson and 

Welsh (1952) have deduced structure parameters from a careful investigation of copper-DL-proline dihydrate. In Fig. 1, atoms Ci and N, C2, Cj, and Cs of the pyrrolidine ring are coplanar. C4 lies at a distance of about 0.60 A out of plane while the carboxyl group attached to atom C2 is disposed on the opposite side of the plane with respect to C4 Bond angles N—Cs—C4 

The crystal structure of L-hydroxyproline was first reported by Zussman (1951) and a complete three-dimensional Fourier analysis published a year 

Several noteworthy features emerge from an examination of the structure 

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