Harvard’s Peabody Museum successfully demonstrates new method for identifying mammalian materials used in cultural objects; opens door for large-scale studies-
Project funding provided by the National Center for Preservation Technology and Training, a unit of the National Park Service (P13AP00078).
Cambridge, MA. October 5, 2015. A two-year project funded by the National Center for Preservation Technology and Training implemented the use of a modern bioanalytical technique (Peptide Mass Fingerprinting—PMF—described below) to identify materials in cultural objects. The Peabody Museum with the Straus Center for Conservation and Technical Studies at the Harvard Art Museums and the FAS Division of Science proposed a proof-of-concept project to demonstrate that (1) PMF could corroborate or replace current methods of materials’ identification by providing specific and accurate information about materials’ sources, (2) PMF could be learned quickly and used successfully by non-expert museum personnel, (3) the technique was sufficiently sensitive to ensure that sample size requirements were consistent with museum sampling practices, and (4) large numbers of objects could be studied in a short period of time. All these goals were met.
According to T. Rose Holdcraft, senior conservator at the Peabody, “This is the first time that PMF has been used in a large-scale survey of materials in any museum collection. We are grateful to the National Park Service for making it possible.” The project team analyzed 449 samples from 111 individual objects with a success rate of 89 percent (i.e., identification of the material source to at least the mammalian family level). Ease of use, quick turnaround time, and accurate analysis of large numbers of samples opens the possibility for extensive, collaborative studies of objects across collections in different institutions. Until now, the identification of mammalian materials used in objects has principally utilized visual or tactile examination and historical information, all of which can be subjective and inaccurate, or in the case of archaeological samples impossible. Although the Peabody project focused on North West Coast and Alaskan Native materials, the technique is the same for any region.
The PMF technique requires comparison with known reference materials for identification of unknowns. The project started with published reference markers for 45 species, and by analyzing over 200 new reference samples, the Project team obtained reference spectra for an additional 61 new mammals, as well as additions to several existing mammalian families.
PMF is one of the modern techniques for protein analysis recently introduced into conservation science and requires only micro-samples of material. The technique uses enzymatic digestion of extracted collagen, the chief proteinaceous component of vertebrate connective tissue (skin, tendon, ligament, bone, and gut), to cleave proteins at specific amino acid sites forming a peptide mixture. Each protein amino acid sequence is unique, and so the mixture of peptides is unique. The mixture is then analyzed by Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI), resulting in a mass spectrum containing characteristic marker peptides—a “peptide mass fingerprint.” Markers are compared with those from known materials to determine the species from which they were derived. The equipment required for the analysis (outside of the MALDI instrument) is modest, of the type found in any lab. MALDI instrumentation is available in most university labs, or can usually be accessed as an open access instrument for a fee. For museums, this technique offers the ability to identify to the family and sometimes the species level the sources of materials in objects made of skin, tendon, ligament, bone, and gut. Such information has not heretofore been possible.
The ability to confirm materials identification will offer researchers the opportunity to assess the availability of specific materials in a given region and, in some cases, may help in sourcing an object of unknown provenance. Conservation scientist Dan Kirby said “We hope that museum professionals see PMF as a powerful method to add to their arsenal of other methods used for materials studies.”
For artisans and cultural groups studying traditional crafts, this technique can aid their efforts to understand and sustain their native heritage. In addition, PMF success with archaeological materials demonstrates that even with a high level of degradation, identification of materials can be made. The most important outcome of the project however will be in raising an awareness of the potential of this relatively simple technique to curators, conservators, and cultural stakeholders. The Project team has developed a procedural manual for interested museums and researchers and will make the reference spectra available on request.
Principal investigator/project coordinator: T. Rose Holdcraft, Head Conservator, Peabody Museum of Archaeology and Ethnology, Harvard University.
Primary analytical investigator/scientist: Daniel Kirby, Ph.D., Conservation Scientist in private practice (formerly of the Straus Center for Conservation and Technical Studies, Harvard Art Museums)
Mass spectrometrist/scientist: Sunia Trauger, Director of the Small Molecule Mass Spectrometry Facility, FAS Division of Science, Harvard University.
About the Peabody Museum
The Peabody Museum is among the oldest archaeological and ethnographic museums in the world with one of the finest collections of human cultural history found anywhere. It is home to superb materials from Africa, ancient Europe, North America, Mesoamerica, Oceania, and South America in particular. In addition to its archaeological and ethnographic holdings, the Museum’s photographic archives, one of the largest of its kind, hold more than 500,000 photographs, dating from the mid-nineteenth century to the present and chronicling anthropology, archaeology, and world culture.
For additional information, please contact Pamela Gerardi, Deputy Director, Curatorial Administration and Outreach. Tel: (617) 496-0099, firstname.lastname@example.org