Lipids of Decomposing Vertebrate Tissue Analyzed with GC-MS and ATR-IR

Lipids are unique molecules that are significant to the structure of cell membranes, metabolism, and cell signaling. Their abundance and stability make them great molecular targets for studying tissue decomposition. Chicken drumsticks and segments of a donated human femur were buried at Southeast Texas Applied Forensic Sciences (STAFS), and sampling of the decomposing bones and the surrounding soil were conducted over a three month period. The Haines lab has employed an extraction method to detect lipids in bone tissue and soil using Gas Chromatography Mass Spectrometry (GC-MS) and Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR) at Texas Research Institute for Environmental Sciences (TRIES). Principal Component Analysis (PCA) of IR spectra in R demonstrated several principle components of variation, including one representing ester hydrolysis in formation of carboxylate groups in the 1400-1600 cm-1 region. PCA data for GC-MS also supports the ester hydrolysis in the degradation of monoacylglycerols. Additional correlations were identified between fatty acid decomposition products, but there is less confidence in the time dependence of the patterns of decomposition. Lipid detection in soil through GC-MS analysis confirmed leaching of tissue lipids into soil.