Archaeological collagen: Why worry about collagen diagenesis?
Archaeological collagen: Why worry about collagen diagenesis?
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DOI：
10.1007/s12520-009-0002-7
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发表时间：
2009-03-01
影响因子：
2.2
通讯作者：
Ritz-Timme, S.
中科院分区：
文献类型：
--
作者：
Dobberstein, R. C.;Collins, M. J.;Ritz-Timme, S.
DNA似乎通过随机断链而衰变，导致可预测的片段长度范围。胶原蛋白的衰变也以同样的方式建模，尽管越来越明显的是，胶原蛋白的衰变并不遵循这种相同的模式。放射性碳和稳定同位素分析现在使用超滤分离大碎片（>原始聚合物长度的30%），即使在更新世骨骼中。那么胶原蛋白是如何衰变的呢？这项研究对比实验降解的样品与从法医，考古和化石骨骼中提取的胶原蛋白。在实验降解的骨中，氨基酸和元素（C：N）组成、体积Δ C-13、Δ N-15和天冬氨酸外消旋（AAR）的值变化很小，直到99%的胶原蛋白丢失，这表明胶原蛋白三螺旋和多肽链保持非常完整。通过使用溴化氰（CNBr）切割，然后通过SDS-PAGE电泳检查单个多肽链的完整性，直接证明了这一建议。在古代样本中，AAR值保持非常稳定，CNBr裂解的模式仅在最古老的（更新世）骨骼中被较小的多肽涂抹所取代。涂片可能反映了甲硫氨酸残基（CNBr切割位点）的修饰和/或胶原蛋白分子的部分水解。研究结果揭示了为什么通常不必担心胶原成岩作用;它大部分是完整的。然而，最古老的骨骼样本部分恶化的证据表明，替代的纯化策略可能会增加一些样本的产量。
DNA appears to decay by random chain scission resulting in a predictable range of fragment lengths. Collagen decay has also been modelled in this same way, although it has become increasingly evident that collagen decay does not follow this same pattern. Radiocarbon and stable isotope analysis now use ultra-filtration to isolate large fragments (>30% of original polymer length) even in Pleistocene bone. How then does collagen decay? This study contrasts experimentally degraded samples with collagen extracted from forensic, archaeological and fossil bone. In experimentally degraded bone, values for amino acid and elemental (C:N) composition, bulk delta C-13, delta N-15, and aspartic acid racemisation (AAR) changed very little until 99% of the collagen was lost, suggesting that the collagen triple helix and polypeptide chains remained remarkably intact. This suggestion was demonstrated directly by examining the integrity of individual polypeptide chains using cyanogen bromide (CNBr) cleavage followed by SDS-PAGE electrophoresis. In ancient samples, AAR values remain remarkably stable and the pattern of CNBr-cleavage was only replaced with a smear of smaller polypeptides in the oldest (Pleistocene) bones investigated. Smearing may reflect both modification of the methionine resides (the sites of CNBr-cleavage) and/or partial hydrolysis of the collagen molecule. The findings reveal why it is not usually necessary to worry about collagen diagenesis; it is mostly intact. However, evidence of partial deterioration of the oldest bone samples suggests that alternative purification strategies may increase yields in some samples.