Noninvasive analysis reveals gum arabic in Dead Sea Scrolls ink

Using a gentle extraction procedure to pull proteins and peptides from parchment without damaging it, scientists have discovered that the Dead Sea Scrollswere written with ink containing gum arabic (J. Proteomics 2021, DOI: 10.1016/j.jprot.2021.104370). The pigment in the ink of the Dead Sea Scrolls comes from ground-up carbon—essentially, soot. But the composition of the ink’s binder, which adheres the pigment to the parchment, has been a mystery. To identify it, scientists have to remove just enough of the material from the parchment for chemical analysis without disturbing the text, explains Gleb Zilberstein, CEO of the sensor company Spectrophon and lead author on the study. Curators of antiquities rightfully live in horror of the idea that any damage could come to their artifacts, so the extraction technique must also be completely noninvasive, leaving no trace on the parchment. Zilberstein and his colleagues adapted a technology he invented that uses charged beads embedded in ethylene-vinyl acetate to extract molecules. Then, they analyzed the extracted material with gas chromatography/mass spectrometry, generating a list of proteins, peptides, and organic molecules. They mined taxonomy databases to identify organisms containing the mixture. Two species of acacia trees common in the Middle East, Vachellia nilotica and Acacia albida, popped up, which suggests that the ink’s binder is made from gum arabic. The sticky substance is derived from these trees. Zilberstein says any lab could use this technique to analyze similarly precious materials.