Estimation of Postmortem Interval Based on the Third Component of Complement (C3) Cleavage

用交叉免疫电泳法研究了老年血和尸体血中补体第三组分（C3）的自发裂解，以估计死亡间隔（PMI）。体外不同温度下的C3裂解实验表明，全血在较高温度下孵育能更快地将β IC（天然C3）转化为β 1A （C3_c）。在尸体血液中，我们发现C3切割百分比与pmi之间存在显著的正相关。从这些结果，可以估计PMI从C3解理的比率。利用C3体外解理动力学dC/dt = -kC，其中C为t时刻天然C3的浓度，k为一级速率常数，利用Arrhenius方程和另一个假设死亡后体温线性下降的方程，计算C3解理的百分比。在尸体血液中，计算百分比与测量百分比之间存在显著的正相关关系，最高可达10%。我们发现，在每个可选的死后间隔内计算出的C3切割百分比与在尸体血液中测量到的高达10%的百分比之间的比较可以得出PMI的估计。这种方法是朝着开发基于C3解理（即基于一级反应）确定PMI的准确方法迈出的一步。

To estimate postmortem interval(PMI), spontaneous cleavage of the third component of complement (C3) was studied in aged blood and cadaveric blood by crossed immunoelectrophoresis. C3 cleavages in vitro at different temperatures showed that the incubation of whole blood at a higher temperature led to a faster conversion of beta IC (native C3) to beta 1A (C3_c). In cadaveric blood, we found a significant positive correlation between percentage of C3 cleavage and pmi. From these results, it is possible to estimate PMI from the ratios of C3 cleavege. Using the kinetics of C3 cleavage in vitro described as dC/dt = -kC, where C is the consentration of native C3 at time t and k is a first-order rate constant, Arrhenius' equation, and another equation which assumes a linear drop of body temperature after death, the percentages of C3 cleavage were calculated. There was a significant positive correlation between the calculated percentages and the measured percentages of up to 10% in cadaveric blood. We found that the comparison between the calculated percentage of C3 cleavage for each optional postmortem interval and the measured percentage of up to 10% in cadaveric blood leads to the estimation of PMI. This approach is one step towards the development of an accurate method for determining PMI based on C3 cleavage, that is, on a first-order reaction.