Collagen imino acid content

Fig. 37. Dependence of the thermodynamic parameters AH and AS of triple-helix formation on the imino acid content of the peptides (obtained by cleavage of calf skin-type I collagene with cyanogene and subequent isolation by column chromatrography)3) and of the native neutral salt-soluble skin collagene of various animals. The entropy values are denoted by dotted lines...

Relation between Imino Acid Content and Shrinkage and Denaturation Temperatures for Various Collagens... 

Ty ( ), and the total imino acid content of various collagens. The numbers refer to samples listed in Table I. Sample 7 was not included when calculating regression lines. See Ref. 9 for details. 

Fig. 168. The collagen melting temperature in salt-free solution with pH 3.7 vs total imino acid content per 1000 residues (O) vertebrates ( ) invertebrates constructed after data presented in [430]...

Fig. 2. Alpha carbon traces for the collagen-like peptide T3-785 (thick lines) superimposed on idealized models of 7/2 and 10/3 symmetry (thin lines), showing the variation in helical S30nmetry in different regions along this peptide. The central zone lacks imino acids while the terminal zones have a high imino acid content as they are Gly-Pro-Hjrp repeats. From Ref. 8 with permission.

The total imino acid content of collagen is higher than in most other proteins. Proline and hydroxyproline together account for two-ninths of the residues. Wherever an imino acid unit occurs there is a loss of free rotation about successive bonds in the polypeptide chain because of the influence of the rigid planar pyrrolidine ring (Figure 27.4). In consequence the chain is both stiff and bent at this point. 

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