The changes of Fourier transform infrared spectroscopy in rat's brain

Objective: To apply Fourier transform infrared (FTIR) spectroscopy to study the process of post-mortem degradation of the rat brain and to provide a new way for the estimation of postmortem interval (PMI). Methods: The rats were sacrificed by cervical dislocation and the bodies were kept in a controlled environmental chamber set at (30±2)°C. To measure the content of the chemical groups in postmortem rat brains at the different time points from 0 to 36 h using the FTIR spectrograph. Results: With prolongation of PMI, the peak position of main absorbance bands in the FTIR spectra showed no significant changes, while the peak levels showed dramatic changes: (1) The relative peak intensity of 1080 cm^-1, 1238 cm^-1 (I₁₀₈₀/I₁₃₉₈/ I₁₃₉₈) associated with nucleic acid decreased obviously; (2) The peak intensity ratio at Amide I, II (I₁₆₄₇/ I₁₅₄₁) decreased; (3) The peak intensities at 1456 cm^-1 and 1398 cm^-1 showed a decreased and an increased trend, respectively; (4) Compared to the peak intensity of 1647 cm^-1, the peak intensities at 2852 cm^-1, 2871 cm^-1, 2923 cm^-1, and 2958 cm^-1 tended to increase, with only a slightly increased tendency in peak intensity of 2871 cm^-1. Conclusion: FTIR spectroscopy may be potentially used as an effective method for estimating the PMI in medicolegal practice using brain tissue sample.