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Identifying ritual blood in African artifacts
Intensity
Throughout history, mythologies have cation of chemical imaging techniques lated spatially with the protein signals. built up about the roles of sacred—and that allowed the researchers not only to However, in four other samples— in some cases, sacrificial—rituals in identify the constituents of the patinas three of which belonged to the older, ancient cultures. How much these stobut also to conserve the spatial distribu- Dogon culture—the scientists were ries reflect historical realities, however, tion of the components. unable to detect any heme, suggesthas been a long-standing question. In The first step was to look for eviing either they had reached the blood research published in AC (2007, 79, dence of hemoglobin with TOF secdetection limits of TOF SIMS or there 9253–9260), Pascale Richardin and ondary ion MS (SIMS) and synchrowas no blood. The researchers therefore colleagues at the Centre de Recherche tron-based IR microspectrometry looked for signs of another blood comet de Restauration des Muponent—iron—with both X-ray sées de France, the Institut microfluorescence (µXRF) and Proteins Max 100 de Chimie des Substances X-ray absorption near-edge miNaturelles, and the European crospectroscopy (µXANES). 80 Synchrotron Research FacilAs Richardin explains, Min 60 ity (all in France) answer this “XANES ensures that the iron Heme Max m /z 616.2 question for a series of African detected by XRF is indeed 40 art objects. linked with proteins and not “The physical reality of ritwith the mineral phase of the Min 20 ual objects cannot be separated clay, [which may be] present as from cultural mythology,” another patina component.” 0 350 400 450 500 550 600 650 Richardin says. “Indeed, they For three of the four obare often the only statement jects, the researchers could and visible consequences of the TOF SIMS analysis of an African artifact, highlighting the identify protein-related traces rituals or beliefs, which in some characteristic m/z 616.2 peak of heme as well as the overlapping of iron, whereas one Dogon cases disappeared long ago.” spatial distribution of proteins (sum of amino acid fragments) and statuette showed only clay-maRichardin and colleagues heme (tripyrrole fragments) on the sample’s surface. trix-related iron. Thus, Richarwere interested in the patina— din was able to say with some a residual coating left by ritual fluids (SR-µFTIR). TOF SIMS allowed the degree of certainty that seven of the poured on the objects. They analyzed researchers to detect low-m/z fragartifacts had been used in blood rituals several African artifacts dating from the ments characteristic of proteins, which at some point in their history. late 19th to early 20th centuries back to they compiled to develop a 2D im“Using this new protocol, we conthe 12th to 14th centuries to determine age of the distribution of the proteins tinue to study others samples of African whether blood served as one of these across the surfaces of the objects. They patinas,” she says. “Another project is ritual fluids. then confirmed the distribution with the analysis of materials used by Euro“The only scientific information SR-µFTIR, creating a similar image of pean Renaissance painters and, in parconcerning these ritual objects and the the surfaces composed of amide 1 band ticular, copper-based pigments and their composition of the materials used for spectra. With this method, the research- degradation products when they are in libations are oral testimonies collected ers found protein in all but the oldest contact with a lipid-type binder.” during ethnographic expeditions,” samples, for which protein degradation Despite her scientific vocation, or Richardin explains. was likely a problem. perhaps because of it, Richardin sees Given the age and value of the obNext, the researchers looked for eviherself as very much part of the mujects, the researchers needed methods dence of the iron-binding component seum community. that were nondestructive but sensiof blood—the iron protoporphyrin “Physicochemical analyses are a way tive enough to work with very small IX complex heme—with TOF SIMS. to increase our knowledge about the samples. “The chosen methods must be Wherever heme signals overlapped the mythology, and our analyses are comable to work on a unique sample withprotein signals they had identified earplementary with ethnological and arout destroying it,” Richardin says. “And lier, the researchers could be confident chaeological approaches,” she says. “All to get the maximum amount of inforthe protein was hemoglobin. They these fields follow the same goal: the mation possible, the selected techniques noted a clear heme signal in one of the understanding of cultures and beliefs of must be complementary.” statuettes, whereas three others showed past and present civilizations.” a Also key to the work was the appliweaker signals that nonetheless corre—Randall C Willis 10
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