Protein Radio Immuno Assay (pRIA)

(Positive Identification of Morphologically Unidentifiable Bone Fragments)

         Bones contain a variety of proteins, the principle one being collagen, which constitutes about twenty percent by weight in fresh vertebrate bones. Serum albumin is also present in bone. Both protein and albumin are usually preserved in fossil bones with some degree of species specificity. pRIA is a method capable of extracting this genetic information. It is most suited for identification of "human" vs. "animal" origin, but capable of identification to family or even species in some cases. Its greatest applicability is to specimens which are morphologically unidentifiable. The capability of the method to work on any individual sample ultimately depends upon the preservation within that sample. However, verifiable results have been obtained on archaeological specimens exceeding 10,000 years old and on cremated specimens.

         pRIA was first applied to analysis of fossils and living species by Dr. Jerold Lowenstein while at the University of California (Department of Medicine, San Francisco). Dr. Lowenstein pioneered the application of pRIA to fossil molecules, with his 1st paper given to the Royal Society of London in 1981. Dr. Lowenstein has used his method routinely throughout the 1980's to present in his personal research. MicroAnalytica partnered with Dr. Lowenstein in 2002 to offer pRIA services to the forensic community. MicroAnalytica is managed by Mr. Darden Hood, who has 20 years experience in providing analytical services on a time-critical basis to the research, governmental and industrial communities. The collaboration provides a pRIA service that delivers results within as little as two weeks.

         pRIA is a valuable complement to DNA analysis, especially in cases where DNA is degraded or absent and taxonomic information is essential. In extreme cases (e.g. fossils or cremated specimens) pRIA has some advantages over DNA analysis. DNA is poorly preserved in fossils and usually absent in cremated specimens. However, the proteins and albumin used in pRIA analysis often remain to provide genetic information. pRIA routinely gives positive results, takes only a few weeks, is not burdened with the severe contamination issues of DNA analysis and is readily verifiable.

         pRIA analysis is based upon antibody response. The protein from the bone specimen under examination acts as an "antigen" (i.e. a foreign agent that generates an antibody response). Approximately 200 mg of bone powder is extracted from the specimen, digested in EDTA, and then subjected to species-specific antisera. If the anti-sera recognizes the antigen, it will attach itself to it (called "binding"). For example, antisera specific to human albumin will bind more strongly to albumin extracted from a human bone and will bind more weakly or not at all to the non-human albumin extracted from other species. By designing species-specific antibodies (antisera) and labeling them with a known amount of radioactive tracer (iodine-125), the degree of binding can be quantified (using scintillation counting) and the taxonomic identity can be determined.

         pRIA is a relative measure. A comparison is made between the proteins or albumin within the unknown sample and the species-specific antisera. It works best for "human" identification since binding is usually large in all cases of a match (sample and antisera). In cases of family or species identification, the client provides a list of 4-5 possible candidates (e.g. cow, bird, dog, or goat) and the suspected unknown candidate is compared to known animal antisera within our library. Species to species identification is limited due to do cross-reactions between similar species (e.g. sheep vs. goat or cow vs. bison).