这项研究的目的是研究阳光对从不同类型表面的血迹中提取的DNA样品降解的影响。从单个男性供体获得的血液样本被放置在七个不同的表面上(镀锌板,铁杆,报纸,白色打印纸,玻璃,土壤,和陶瓷面板)。样本被保存,在4周的夏季期间,在一个房间里,但旁边是一个打开的窗口。每7天,从每个基底收集1mm2的血液样品并储存在标记的管中用于以后的分析。用Chelex方法提取DNA,使用AmpFISTRTMMinifilerTMPlus扩增试剂盒扩增,并使用QuantifilerTM人DNA定量试剂盒定量。经过7天的阳光照射,确定最高的DNA浓度来自镀锌板染色的样品,其次是,按照浓度递减的顺序,陶瓷面板,玻璃,报纸,铁杆,和白色打印纸表面。不出所料,所有样品的DNA浓度随着日光暴露时间的延长而降低。在MiniFilerTM系统中扩增后获得的结果与通过qPCR方法测量的所有样品的DNA浓度相关,除了玻璃,土壤,和白色打印纸样品。获得的数据表明,DNA降解与阳光暴露的长度以及从其收集样品的表面类型相关。阴性qPCR结果并不意味着STR系统中的阴性PCR扩增;因此,在分析从痕迹证据中收集的法医样本时,应应用这两种方法。
The aim of this study was to investigate the effect of sunlight on the degradation of DNA samples taken from blood stains from different types of surfaces. A blood sample obtained from a single male donor was placed on seven different surfaces (galvanized sheet, iron rod, newspaper, white printer paper, glass, soil, and ceramic panel). Samples were kept, during a 4-week summer period, in a room, but next to an open window. Every 7 days, 1 mm2 of blood sample was collected from each substrate and stored in labeled tube for later analysis. DNA was extracted with the Chelex method, amplified using AmpFISTRTM MinifilerTM Plus Amplification Kit, and quantified using a QuantifilerTM Human DNA Quantification kit. After 7 days of sun exposure, the highest DNA concentration was determined to be from the sample from a galvanized sheet stain, followed by, in order of decreasing concentration, the ceramic panel, glass, newspaper, iron rod, and white printer paper surface. As expected, the DNA concentration from all samples decreased as the sunlight exposure time progressed. The results obtained after the amplification in the MiniFilerTM system were in correlation with the DNA concentrations measured by the qPCR method for all samples, except for the glass, soil, and white printer paper samples. The obtained data show that DNA degradation is correlated to the length of sunlight exposure and to the type of surface the samples are collected from. A negative qPCR result does not mean negative PCR amplification in the STR system; therefore, both methods should be applied when analyzing forensic samples collected from trace evidence.