Chemistry of Organic Matrix

In Table 3, the geometric means of amino acids in mineralized tissues of a series of representative classes of organisms are sumarized217,218,22S). In spite of the diversity in the amino acid composition of the shell organic matter, all matrices have one property in common, that is, they contain functions that operate as an effective calcifying agent. 

On a relative basis, i.e. residues per 1000, there is virtually no one species like the other. In contrast, different shell samples from the same species and obtained from the same natural habitat yield identical amino acid patterns. It is of interest that (1) the structure of carbonates (aragonite-calcite-vaterite), (2) the content in trace elements, and (3) the stable isotope distribution are markedly effected by fluctuations in salinity, water temperature, Eh/pH conditions, and some anthropogenic factors. The same environmental parameters determine to a certain degree the chemical composition of the shell organic matrix. This feature suggests a cause-effect relationship between mineralogy and organic chemistry of a shell. In the final analysis, however, it is simply a reflection of the environmentally-controlled dynamics of the cell. 

To explain the species-specific amino acid pattern one can assume that each organism secretes one particular calcifying protein which to a limited extent is controlled by the environment. Alternately, a series of different proteins can yield the observed pattern, however, we have to postulate that each one is secreted at a constant rate. Changes in rate of secretion, perhaps environmentally induced, will effect the ratio of the individual proteins and thus account for slight variation in the amino acid distribution in the hydrolyzed matrix. 

Since at the species level virtually no difference in distribution of amino acids exists, unless specimens are taken from diverse environments, it was of interest to 

Bryozoa (3) Echinoidea (4) Portunid- crabs (6) Pisces (Otoliths) Avian Shell (Goon) 

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