Development of a Novel Minimally Invasive Sampling and Analysis Technique for Bioarchaeological Proteomics

Ancient proteomic analysis has been shown to have several advantages over ancient DNA studies, largely due to the ability of many proteins to survive over longer periods of time than their corresponding genes. High-resolution mass spectrometry allows for large scale data to be generated from small amounts of sample. Typically, sampling of bioarchaeological material for proteomics has involved the use of invasive tools such as drills and hammers, which presents an issue when working with museums and other heritage organisations. There exist a few studies in the published literature on the use of specifically manufactured sampling tapes for the minimally invasive analysis of paintings and frescoes, and recently an example of their application to mummified skin. Here we present the development of a novel minimally invasive sample preparation technique for application in the mass spectrometric analysis of bioarchaeological materials. The extraction protocol was developed by applying commercially available, dermatology grade skin sampling strips to modern skin surfaces as a surrogate, and then applied to cranial and bone fragments belonging to a 26th Dynasty Egyptian mummified individual from the coffin of a woman named Mer-Neith-it-es. Extracted proteins were subjected to electrophoretic separation and proteolytic digestion, resulting in peptides that were separated, fragmented and identified using nanoflow liquid chromatography - high resolution tandem mass spectrometry. We have identified a number of ancient brain and intracellular proteins on the surfaces of the various cranial and bone fragments, without causing any significant damage to these valuable remains.