Semi-quantitative Detection of Signature Peptides in Body Fluids by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

This study covers a modified semi-quantitative approach for liquid chromatography mass spectrometry (LC-MS/MS) signature peptide detection for body fluid identification. Peptide concentrations were measured based on synthetic peptide standards. Samples were processed with varying trypsin digestion and purification protocols, including a three-hour trypsin digestion and Microcon membrane filtration. The Microcon filtration method generates polymerase chain reaction (PCR) compatible DNA and peptide fractions that can be analyzed without any further purification. Preliminary validation tests covered stains on different substrates, semen/ saliva mixtures, minimum sample volume, and repeatability. All signature peptides in the multiplex were present at different concentrations and varied amongst donors. Saliva peptides were detected at lower concentrations and had a higher minimum sample volume. Semen peptides could be detected even as a minor component in a mixture. All semen and saliva peptides were detected on the various substrates. DNA fractions did not show signs of degradation or PCR inhibition