Journal
INTERNATIONAL JOURNAL OF LEGAL MEDICINE
Volume 127, Issue 2, Pages 321-333Publisher
SPRINGER
DOI: 10.1007/s00414-012-0770-y
Keywords
PCR inhibition; Pressure cycling technology; Forensic DNA analysis; Hematin; Humic acid; Hi-Flow column
Categories
Funding
- National Institute of Justice, Office of Justice Programs, US Department of Justice [2009-DN-BX-K188]
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A common problem in the analysis of forensic human DNA evidence, or for that matter any nucleic acid analysis, is the presence of contaminants or inhibitors. Contaminants may copurify with the DNA, inhibiting downstream PCR or they may present samples effectively as containing fewer templates than exist in the PCR, even when the actual amount of DNA is adequate. Typically, these challenged samples exhibit allele imbalance, allele dropout, and sequence-specific inhibition, leading to interpretational difficulties. Lessening the effects of inhibitors may increase the effective yield of challenged low template copy samples. High pressure may alter some inhibitors and render them less effective at reducing the yield of PCR products. In an attempt to enhance the amplicon yield of inhibited DNA samples, pressure cycling technology was applied to DNA exposed to various concentrations of hematin (0, 1.25, 2.5, 5, and 7 mu M) and humic acid (0, 1.25, 2.5, 5, and 7 ng/mu L). The effect of high pressure on the inhibitors, and subsequently the PCR process, was assessed by measuring DNA quantity by quantitative PCR and evaluating short tandem repeat typing results. The results support that pressure cycling technology reduces inhibitory effects and thus, in effect, enhances yield of contaminated amplified products of both hematin and humic acid contaminate samples. Based on the results obtained in this study, this method can improve the ability to type challenged or inhibited DNA samples.
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