Protein, bone

We proposed to study diet and health by combining bone chemistry and histomorphometry. Diet would be determined by analysis of stable isotopes of carbon and nitrogen in bone protein and some preserved hair. In addition, trace elements would be quantitatively analyzed in preserved bone mineral. Abonyi (1993) participated in the study by reconstructing the diet from historical sources and analyzing various foods. Having analyzed human tissues for stable isotopes and trace elements, and foods for the same variables, we hoped to learn more about 19th century diet in southern Ontario, and at the same time, learn more about paleodiet reconstruction. 

Bone protein was extracted following the method described by Sealy (1986). Bone chips were demineralized in a weak HCl solution, then soaked in 0.1 M NaOH to remove base-soluble humic substances. Remaining material, which is mainly collagen, but includes non-collagenous proteins, was... 

Unquestionably, there are limitations to such a procedure, and because calculations for two specimens failed, they lead to an even higher deviation from the control signal. These limits have to be defined by future work. The model experiment is only an approach to collagen diagenesis in buried bone. In nature, more than one bacterial species feeds from bone protein, and a... 

There are approximately 200 other proteins present in bone, though most of them are present only in trace amounts (Delmas et al., 1984 Linde et al., 1980, as cited in van Klinken, 1991). The second most common bone protein, osteocalcin, comprises 1-2 weight % of total fresh bone. Osteocalcin bonds with both the bone mineral fraction and bone collagen, but it seems to be unstable in solutions. Due to its small molecular size and strong mineral stabilization, osteocalcin can survive up to 50.000 years (C.l. Smith et al., 2005), and it may offer an alternative to the use of collagen in paleoenvironmental stable isotope research. However, osteocalcin s role and importance in this field of study has yet to be defined (Collins et al., 2002). 

Collagens Collagen type 1 Approximately 90% of total bone protein. Composed of two a1(l) and one a2(l) chains. 

Kuftinec, M. M., Miller, S. A. Bone growth in the neonatal rat I. Biochemical aspects of bone protein synthesis. Calc. Tiss. Res. 11, 105 (1973)... 

Other phosphoproteins, glycoproteins, and proteoglycans may also be required for mineralization. For example, the 286-residue glycoprotein osteonectin323 700 701 accounts for 3% of total bone protein. It contains two Ca2+-binding motifs and inhibits growth of hydroxylapatite crystals, but its role in bone development is not clear. One of the phosphoproteins of developing bone has been identified as... 

The odontoblasts secrete an extracellular matrix that is rich in collagen I and which also contains all of the other major bone proteins as well as a dentin sialoprotein and poorly characterized phosphate carriers, the phosphophoryns. 

Bone proteins Limits crystal growth (Gla proteins)... 

The number of amino acids in bone was also observed to decline with postmortem age as bone proteins hydrolyzed and released the amino acids into the environment (Knight 1968). A bone sample that yields seven or more amino acids suggests an age of less than 100 years old, and if it contains both proline and hydroxyproline, it is most likely less than 50 years old (Knight 1968). 

Racemization rates (Table I) clearly differ among these seven amino acids. To compare results from the four proteins, rate constants were calculated from these data. For casein, D/L ratios were measured at 0, 1, 3, 8 and 24 hours. These results are plotted in Figure 2. The curves have two regions of different racemization rates. Rapid initial rates observable up to about 3 hours are followed by slower rates up to 24 hours. The amino acids apparently have not reached equilibrium by 24 hours of incubation. Theoretically for amino acids having one asymmetric center, the equilibrium D/L ratio is 1.0. This value has been observed in fossil bone protein (see 13) and in dry roasted proteins (10), but not in calcareous marine sediments (17) nor in fossil mollusc shell (18). 

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