大头金蝇蛹壳蛋白质降解特征的法医学意义

The forensic significance of characteristics of the protein degradation in puparium cases of Chrysomyia megacephala

目的研究大头金蝇Chrysomyia megacephala蛹壳风化不同时间的蛋白质降解,探讨其在法医学死亡时间推断上的意义。方法收集人工饲养的C.megacephala蛹壳,放置于树林内5、10天后收回,进行红外光谱采集及预处理,读取蛋白质酰胺吸收峰,并对每组平均光谱进行曲线拟合。应用SPSS 19.0软件进行统计学分析。结果与对照组相比,风化5天组,蛋白质酰胺Ⅰ的峰位蓝移,酰胺Ⅱ的峰位变化无统计学意义,且酰胺Ⅰ及Ⅱ的峰强度变化均无统计学意义。蛋白质的二级结构,α-helix略减少且β-sheet略增加,而β-turn无变化;风化10天组,蛋白质酰胺Ⅰ及Ⅱ的峰位均蓝移,酰胺Ⅰ吸收峰出现明显肩峰,且酰胺Ⅰ及Ⅱ的峰强度均明显下降。蛋白质二级结构,α-helix及β-sheet的变化趋势与5天组一致,而β-turn显著增加。结论红外光谱显示C.megacephala蛹壳风化10天内,蛋白质酰胺Ⅰ及Ⅱ的吸收峰变化开始呈现出一定的特征性,可辅助较长时间的死亡时间推断。

Objective To observe the protein degredation of empty puparium cases ofC. megacephala after weathering and to explore its practical significance on postmortem interval estimation in forensic science. MethodsThe standardized feeding was used inC. megacephala, and the empty puparium cases were collected and put into the forest. They were taken back 5 days, and 10 days later, respectively. The spectra were collected and preprocessed, and then the absorption peaks of amides were read, and curve fitting was performed in the average spectra of each group. The statistical analysis was performed by SPSS 19.0.Results Compared to control group, ifve days post weathering, the position of amideⅠabsorption peak showed blue shift, but the amideⅡabsorption peak showed no shift, moreover, none of the amide absorption peaks showed changes inpeak intensity. For the secondary structures, α-helix decreased and β-sheet increased slightly, however, β-turn did not change; Ten days post weathering, the positions of both amideⅠandⅡabsorption peaks showed blue shift, and an obviousshoulder peak appeared in amide I absorption peak. Meanwhile, both of amideⅠandⅡabsorption peaks showed decreased in peak intensity. Moreover, for the secondary structures, α-helix and β-sheet showed the same tendency as in the 5th day group, except for the β-turn increased dramaticlly.Conclusion The spectra of the empty puparium cases of C. megacephala showed that the absorption peaks of amideⅠandⅡpresented certain characteristic features within ten days post weathering, and estimate relative long-time postmortem interval.