Table S4 from A fossil protein chimera; difficulties in discriminating dinosaur peptide sequences from modern cross-contamination

A decade ago, reports that organic-rich soft tissue survived from dinosaur fossils were apparently supported by proteomics-derived sequence information of exceptionally well-preserved bone. This initial claim to the sequencing of endogenous collagen peptides from an approximately 68-Myr Tyrannosaurus rex fossil was highly controversial, largely on the grounds of potential contamination from either bacterial biofilms or from laboratory practice. In a subsequent study, collagen peptide sequences from an approximately 78 Myr Brachylophosaurus canadensis fossil were reported which has remained largely unchallenged. However, the endogeneity of these sequences relies heavily on a single peptide sequence, apparently unique to both dinosaurs. Given the potential for cross-contamination from modern bone analysed by the same team, here we extract collagen from bone samples of three individuals of ostrich, Struthio camelus. The resulting LC–MS/MS data were found to match all of the proposed sequences for both the original Tyrannosaurus and Brachylophosaurus studies. Regardless of the true nature of the dinosaur peptides, our finding highlights the difficulty of differentiating such sequences with confidence. Our results not only imply that cross-contamination cannot be ruled out, but that appropriate measures to test for endogeneity should be further evaluated.十年前，有研究报道恐龙化石中仍留存有富含有机物的软组织，该结论得到了保存异常完好的骨骼的蛋白质组学（proteomics）序列信息的佐证。这项针对约6800万年前霸王龙（Tyrannosaurus rex）化石中内源性胶原肽进行测序的最初主张，引发了广泛争议，争议核心在于其存在潜在污染风险——污染来源可能为细菌生物膜，亦或是实验室操作污染。在后续的一项研究中，研究者报道了来自约7800万年前加拿大短冠龙（Brachylophosaurus canadensis）化石的胶原肽序列，该结论迄今基本未受到质疑。然而，认定这些序列为内源性的结论，高度依赖于一条仅在这两种恐龙中存在的单一肽段序列。考虑到同一研究团队在分析现代骨骼样本时存在交叉污染的潜在可能，本研究从3只非洲鸵鸟（Struthio camelus）的骨骼样本中提取了胶原。最终获取的液相色谱-串联质谱（LC–MS/MS）数据显示，其与前述两项研究（霸王龙与短冠龙研究）中提出的所有序列均匹配。无论恐龙来源肽段的真实属性如何，本研究结果均凸显了准确区分此类序列的难度。本研究结果不仅表明交叉污染无法被完全排除，同时也提示，用于验证内源性的合理检测手段仍需进一步优化完善。