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A correlation between the distribution of biological apatite and amino acid sequence of type I collagen

University of British Columbia

The present study was undertaken to examine the distribution of biological apatite within type I collagen fibrils of calcifying turkey leg tendons. The localization of apatite was determined by both bright field and selected-area dark field electron microscopy and was correlated with specific classes of amino acids from chick type I collagen sequence data by computer modelling. These electron microscopic techniques illustrated that apatite occurs in both the gap and overlap zones at early stages of mineralization in an asymmetric pattern which corresponds to the polarized IM- to C- molecular orientation within the collagen fibril. Based on comparisons with theoretical computer images of the known amino acid sequence of collagen it was determined for early stages of mineral deposition that apatite is excluded from areas of high hydrophobic density. The gap zone is less hydrophobic than the overlap zone on average but each of these zones had areas of high density of hydrophobic amino acids which corresponded to sites of low mineral density. Conversely, regions with a high proportion of mineral were low in density of hydrophobic amino acids. The possible interactions between hydrophobic effects and the process of mineral deposition are discussed. In addition, the accommodation of collagen to the deposition of apatite in the overlap zone is discussed.

Text

2010-08-21

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http://hdl.handle.net/2429/27591

Anatomy, Cell Biology and Physiology

University of British Columbia

Graduate