Abstract
DNA on touched objects is often present in low amounts, causing poor STR typing results. Testing genetically variable proteins is a promising approach for obtaining additional individualization. We are showing here that it is possible to obtain PCR-STR results for DNA and mass spectrometry protein sequences starting with a single trypsin digestion. For a standard DNA extraction method using Millipore Microcon MW100 filter units, proteinase K was replaced with trypsin, and sodium dodecyl sulfate with ProteaseMAX, a mass spectrometry compatible detergent. This neatly separates both substances: DNA is retained by the membrane with digested proteins in the flow through. It was also possible to amplify trypsin extracted DNA without further purification, but Microcon separation of both fractions was more suitable for both STR and mass spectrometry analysis. When tested in parallel to a standard proteinase K method, the Microcon co-extraction method showed better DNA typing success rates. Mass spectrometry for the Microcon based trypsin co-extraction method yielded a large number of identified proteins, including tissue specific proteins for both fingerprint and saliva samples.
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