Omics for Precious Rare Biosamples: Characterization of Ancient Human Hair by a Proteomic Approach

Omics technologies have far-reaching applications beyond clinical medicine. A case in point is the analysis of ancient hair samples. Indeed, hair is an important biological indicator that has become a material of choice in archeometry to study the ancient civilizations and their environment. Current characterization of ancient hair is based on elemental and structural analyses, but only few studies have focused on the molecular aspects of ancient hair proteins-keratins-and their conservation state. In such cases, applied extraction protocols require large amounts of raw hair, from 30 to 100 mg. In the present study, we report an optimized new proteomic approach to accurately identify archeological hair proteins, and assess their preservation state, while using a minimum of raw material. Testing and adaptation of three protocols and of nano liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) parameters were performed on modern hair. On the basis of mass spectrometry data quality, and of the required initial sample amount, the most promising workflow was selected and applied to an ancient archeological sample, dated to about 3880 years before present. Finally, and importantly, we were able to identify 11 ancient hair proteins and to visualize the preservation state of mummy's hair from only 500 μg of raw material. The results presented here pave the way for new insights into the understanding of hair protein alteration processes such as those due to aging and ecological exposures. This work could enable omics scientists to apply a proteomic approach to precious and rare samples, not only in the context of archeometrical studies but also for future applications that would require the use of very small amounts of sample.