Animal soft tissues feature regularly in cultural artefacts but it can be difficult to pinpoint their origin. Visual identification of these tissues relies on the skill of the examiner and the condition of the material. Analytical techniques, like gas chromatography-mass spectrometry, can detect and broadly classify proteins but give no answers as to their source. Precise identification of the sinews used for stitching is often impossible. Now, researchers in the US and UK have shown that peptide mass fingerprinting can be used to determine the animal species of collagen-based materials in a diverse range of museum objects.
Peptide mass fingerprinting (PMF) uses enzymes to digest proteins to produce a mixture of peptides. The mass spectrum of this mixture will have characteristic marker ions – called a peptide mass fingerprint – which are compared to a database of species-specific markers to identify the proteins.
Dan Kirby, from the Straus Center for Conservation and Technical Studies, Cambridge, Massachusetts, and co-workers, were asked to identify the source of skin and sinew on 19th century kayaks from Kodiak Island in Coastal Alaska. Using PMF, they identified the exact species of seal, whale and caribou that were used to make the kayaks – valuable information for understanding the past.
Caroline Solazzo an expert in proteomics at the University of York, UK, likes that the technique can identify proteins with such a high level of specificity and describes it as ‘elegant, fast and minimally destructive.’
The technique is easy to use. Following on from the team’s work, museum personnel have been trained to use PMF and have identified over 100 Coastal Alaska Native objects.
In order to identify more objects Kirby says that ‘filling out the database and providing an easy search method are the top priorities.’ Other groups are now applying the technique to identify keratin-based materials such as feathers, horns and hooves.