In collagen

Fibrous proteins can serve as structural materials for the same reason that other polymers do they are long-chain molecules. By cross-linking, interleaving and intertwining the proper combination of individual long-chain molecules, bulk properties are obtained that can serve many different functions. Fibrous proteins are usually divided in three different groups dependent on the secondary structure of the individual molecules coiled-coil a helices present in keratin and myosin, the triple helix in collagen, and P sheets in amyloid fibers and silks. 

Fibrous proteins are long-chain polymers that are used as structural materials. Most contain specific repetitive amino acid sequences and fall into one of three groups coiled-coil a helices as in keratin and myosin triple helices as in collagen and p sheets as in silk and amyloid fibrils. 

FIGURE 6.16 The hydroxylated residues typically found in collagen. 

FIGURE 6.20 A disaccharide of galactose and glucose is covalently linked to the 5-hydroxyl group of hydroxylysines in collagen by the combined action of the enzymes galactosyl transferase and glucosyl transferase. 

Model peptides that could build up quarternary fibrillar structures are not yet known. Though complete explanation of the interdependence between the primary structure and the stability of the quarternary structure has not yet been possible, i.e. the role of the different amino acids in collagen could be understood completely only in correlation with the fibril formation (formation of polar and hydrophobic clusters ). 

Brown, A.F. (1982). Neutrophil granulocytes Adhesion and locomotion on collagen substrata and in collagen matrices. J. Cell Sci. 58, 455-467. 

The 8 C values of the Preclassic humans at Cuello (Table 2.1) average -12.9 0.9%o (n = 28) in collagen, -9.8 1.0 in bone apatite (n = 16), and -8.7 2.3%o in tooth enamel apatite (n = 33) the S N values in collagen average 8.9 1.0%o (n = 23). The discrepancy in the number of specimens is due to the fact that more teeth were available than post-cranial material, while some of the specimens contained insufficient collagen to measure the nitrogen isotope ratios. Additional bone apatite analyses are in progress. 

Table 2.2. Carbon isolope values in collagen of modern and ancicni fauna wiih C3 plant diets. The isotope values for ancient armadillo were not included in the average since they dearly consumed some C4 plants.

The following differences have been observed in modern mammals from cold and temperate areas with no C4 plants a slight enrichment in C in collagen between herbivores and carnivores a clear difference in carbonate hydroxylapatite 8 C values between herbivores and carnivores (including bears), and thus a difference between A Cvalues of herbivores and carnivores a clear enrichment in N between herbivore and carnivore bone collagen. 

Bocherens, H., Pacaud, G., Lazarev, P. and Mariotti, A. 1996 Stable isotope abundances ( C, N) in collagen and soft tissues from Pleistocene mammals from Yakutia. Implications for the paleobiology of the mammoth steppe. Palaeogeography, Palaeoclimatolology, Palaeoecology 126 31. ... 

Figure 9.2. Amino acid content (mol %) in collagen extract (dark columns) and serum proteins (light columns) from a skeleton from coastal Peru. Due to a prevalence of degraded and soluble collagen, the nonmineral-bound protein fraction shows a collagen amino acid profile.

Figure 9.3. Percentage of non-detectable amino acids in collagen extracts from archaeological human skeletons. Numbers on top of the columns indicate number of carbon atoms per amino acid. XW = weighted mean of % loss (cf. text). Only high-carbon amino acids are more frequently lost than the average.

NOTE ADDED IN PROOF This manuscript had been submitted shortly after the presentation of the paper at the Fourth Advanced Seminar on Pale-odiet, 1994. Ongoing research, especially stable isotope analysis of single amino acids from inoculated and non-inoculated marten bones (same specimens as in this paper) further and strongly support our conclusion that bacterial modifica-tion causes substantial shifts in collagen stable isotope ratios (Balzer et fl/. 1997). 

These mechanisms for the synthesis of glycine present a partial barrier to the movement of FA carbons into this molecule, the most abimdant AA in collagen. On the other hand, proline is synthesized from a-keto glutarate which can be freely derived from either carbohydrates or FAs thus the synthesis of pro line does not present a barrier to entry ofFA-derived carbons into collagen. 

Diet-Tissue Differences in Collagen and Hair Nitrogen Isotopes... 

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