Characterisation of novel α‐keratin peptide markers for species identification in keratinous tissues using mass spectrometry

Abstract

A proteomics approach can successfully identify specific markers for the identification of materials to the genus level, and should be considered when identification by other means is not possible. Identification by PMF is fast, reliable and inexpensive.

Advances in identifying archaeological traces of horn and other keratinous hard tissues

“…The sulfur-sulfur cross-linking between cysteines in the keratin's non-helical end and tail domains and the cysteine-rich keratin-associated proteins contribute to the strength and rigidity of the tissues. 'Hard' keratins have, however, a higher sulfur content than 'soft' keratins, which are also present as minor components in horn and hoof (Solazzo et al, 2013b). The structural organization and orientation of the intermediate filaments vary from tissue to tissue and influence their mechanical properties.…”

“…Trypsin is less efficient on the matrix proteins and therefore the alpha-keratin proteins are expressed to a greater degree in the PMF and peptide markers belonging to the most abundant alpha-keratins can provide reliable identification up to the genus level (Solazzo et al, 2013b). The wool (or hair), horn, and hoof of an animal produce the same keratin sequences but, due to variations in protein expression, differences can be identified between some species markers in 'soft' and 'hard' tissues (Solazzo et al, 2013b). Trypsin is less well adapted to beta-keratin digestion as these keratins contain less of the basic residues.…”

“…While it is preferable to identify a combination of markers for reliable identification, some unique markers have been found to be diagnostic to the genus level (Solazzo et al, 2013b) and therefore can be used to discriminate the most common taxa. Fig.…”

“…21 shows the main markers used for species identification in horse, cow, and sheep gained from the comparandum specimens and Table 2 gives the peptide sequences for these peaks. A complete list of markers can be found in Solazzo et al (2013b) where sheep horn, cow horn, and horse hoof were compared to their wool or hair equivalents. The same diagnostic area is shown in Fig.…”

“…Markers to separate all three species have been described elsewhere (Solazzo et al, 2013b) and are summarized in Table 2, but we focused here on the most diagnostic region of the peptide profiles, between m/z 1800 and 2800 Da. One marker in particular is diagnostic of sheep at m/z 2665, its equivalent in goat is at m/z 2692.…”