Abstract: Objective To apply Fourier transform infrared (FTIR) spectroscopy to study the process of postmortem 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)℃. 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,I1238/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.

Key words: fourier transform infrared, postmortem interval, brain, chemical group