“温和”差异裂解法在性侵积案检验中的应用

The Application of‘Gentle’Differential Lysis Method in the Identifi cation of Cold Rape Cases

本文通过分享一起性侵积案的检验过程及成功经验,总结出一种独特的“温和”差异裂解法,为处理陈旧混合斑检材提供一种新的解决方案。生物检材为案发时受害人穿的秋裤,前期PSA确证实验的结果为阳性,并通过一步裂解法获得了比较完整的男女混合DNA分型,随后通过常规的差异裂解法仅能获得上清女性分型,沉淀部分未获得有效分型结果。经过多次摸索,尝试将第一步女性成分裂解条件变为:裂解液1 mL,蛋白酶K(protease K,PK)工作浓度50μg/mL,37℃裂解20 min;女性成分消化结束后,沉淀洗涤次数调整为1 mL超纯水洗涤1次,最终成功获得了单一女性及单一男性的DNA分型。后续利用模拟的男女混合斑样本对该方法进行进一步测试,发现当混合斑中男女成分的比例不超过1∶40时,该方法具有良好的效果。

In this paper,we summarized a“gentle”differential lysis method by sharing the experimental process and successful experiences of a sexual assault cold case.This method can provide a new solution for handling old mixed stains.The biological sample is the long underwear worn by the victim at the time of the crime.Firstly,we got a positive PSA result of the mixed stains,and then we obtained great mixed DNA profiles with males and females using the one-step lysis method.When we tried the traditional differential lysis method to get a complete single male DNA profile,the result was disappointing because we only met female DNA profiles of the supernatant and the precipitation had nothing.By many tests,we modified the lysis conditions of the female cells to 1mL of lysisbuffer,37℃,20 min and the working concentration of protein’s K(Protease K,PK)is 50μg/mL,after lysis,wash the precipitation once time by 1 mL ddH_(2)O.Finally,we successfully obtained single DNA profiles of both female and male.Subsequently,further testing of this method was carried out utilizing simulated mixed stains from known male and female samples,this method had a good effi ciency when the ratio of male to female was below 1∶40 in mixed stains.At the end,we discuss the relevant factors affecting the quality of sperm DNA profiling results and the considerations for applying this method in practice.