This week, the SCIART Chemistry and Biology teams welcomed a special guest, Dr. Daniel Kirby , as he assisted us in our ivory analyses. For this, Dr. Kirby taught us peptide mass fingerprinting via MALDI-TOF (Matrix Assisted Laser Desorption/Ionization—Time of Flight) mass spectroscopy. 

In peptide mass fingerprinting, the protein of interest is cut into pieces (peptides) by enzymes and suspended in a chemical matrix. The sample is then spotted onto a plate, where the matrix dries and creates a crystal containing the peptides. Once the crystals have formed, the plate is placed into the MALDI-TOF apparatus. A computer then fires a laser at the crystal. This causes the pieces of protein to break apart from the crystal and ionize.

While the laser fires, the ionized peptides are then pulled out by an electric field and reflected by a second field The machine’s computer can then determine the mass of these ionized peptides by how long it takes for them to move through these fields (hence “Time of Flight”).

MALDI-TOF is a useful analytical technique for identifying not only the protein in question, but also the source organism of the protein. Proteins, while largely the same, have some small variances between species. These variances can be from post-translational modifications, as well as different amino acid residues or sequences utilized by the particular species. Through MALDI-TOF, the differences between these versions of protein can be detected, allowing for potential identification of a species or group of species as the source of the protein.

Our research this week served as a practical example. In ivory, there is a protein called collagen. Collagen is one of the most abundant proteins in mammals, where it largely contributes to structures like bones, tendons, and, most important to our project, teeth. 

Ivory is derived from the tusks—or modified teeth—of animals. By analyzing the collagen in suspected ivory samples, we could determine whether it is genuine elephant ivory, as well as what species of elephant (Asian, African bush, or African forest) it may come from.

In our analyses, we succeeded in identifying numerous samples. Some were confirmed of their identity, such as a piece of deer antler. Others were surprises: a small sculpture was polished cow bone, rather than elephant ivory; a contributor’s sample was mammoth ivory, rather than elephant ivory; and that a collection of ivory powder was completely elephant ivory.

This last result will be critical to the future of our project, as this was derived from a sample that must be worked on for future experiments. Confirming this piece as genuine ivory ensures the fidelity of future experiments.