Proteomic Evaluation of Biomarkers to Determine the Postmortem Interval

Proteomics separates and analyzes proteins for investigation at the cellular level in regard to disease processing by analyzing the proteins’ expression, function, structure, post-translational modification, and protein–protein interaction. In general forensic investigations, the postmortem interval was evaluated by measuring changes in body temperature after death, along with forensic entomological knowledge. These investigations may be restrictive and subjective because of external factors. The objectives of this study are to sort biomarker candidates and develop a direct postmortem-interval characterization method using proteomics through analyzing and tracking down proteins in the deceased that change in accordance with the postmortem interval. The liver and heart tissues of rats were collected for protein extraction in the 24-h interval following death, and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis was conducted based on the isoelectric point and the molecular weight for separation. To validate protein spot changes on the gel, the stained electrophoresis gels were scanned and converted to digital images. Through image analysis, 14 liver proteins and 12 heart proteins were sorted and classified into four groups based on pattern changes. These proteins containing spots were extracted from the gel and analyzed by high-performance liquid chromatography with tandem mass spectrometry. Finally, 26 protein postmortem-interval relevant biomarker candidates were identified using software. Some of the proteins were muscle proteins while others were oxidation-related proteins. This study presents a new approach to the postmortem-interval research using proteomics and could be substituted for postmortem-interval evaluation.