Species identification of elephant and mammoth ivory products by LC-MS analysis of type I collagen marker peptides...

Unlike the legal trade in ivory from extinct mammoths, the international trade in ivory from extant elephants is highly restricted. This regulatory difference has led to the fraudulent labeling of elephant ivory as mammoth ivory. Here, we developed an LC-MS method to discriminate between elephant and mammoth species based on interspecies differences in the amino acid sequence of type I collagen, a stable protein component of ivory. Our LC-MS/MS proteomic analysis conclusively determined that there are two amino acid substitutions in mammoth type I collagen α2 chain relative to African elephants (savanna and forest species) and one substitution relative to Asian elephant. No substitutions were found between the two African species. From these findings, four tryptic peptides from the α2(I) chain were selected as markers providing distinct and species-specific detection patterns using LC-MS in multiple reaction monitoring (MRM) mode, allowing for the discrimination between African elephants, Asian elephant, and mammoth. A microsampling technique remarkably reduced the sample requirements and eliminated the need for sample demineralization before trypsin digestion. Our approach, combining the MRM detection of collagen marker peptides with microsampling, successfully identified the animal origin of commercial personal seals made from elephant and mammoth ivory without causing any visible damage. This robust and sensitive species identification methodology provides a powerful, semi-nondestructive tool to verify ivory products and could serve as a deterrent to the illegal trade in elephant ivory.