Post-injection hybridization of complementary DNA strands on capillary electrophoresis platforms: A novel solution for dsDNA artifacts

Several laboratories have reported the occurrence of a split or n − 1 peak at the vWA locus in PowerPlex^® 16 and PowerPlex^® ES amplification products separated on 4- and 16-capillary electrophoresis instruments. The root cause of this artifact is post-PCR reannealing of the unlabeled, unincorporated vWA primer to the 3′-end of the tetramethylrhodamine (TMR)-labeled strand of the vWA amplicon. This reannealing occurs in the capillary post-electrokinetic injection. The split peak is eliminated by incorporation into the loading cocktail of a sacrificial hybridization sequence (SHS) oligonucleotide that is complementary to the vWA primer. The SHS preferentially anneals to the primer instead of the TMR-labeled strand of the vWA amplicon. In addition, the n − 10/n − 18 artifact that may be seen at the vWA locus was determined to be due to double-stranded amplicon formed post-electrokinetic injection into the capillary. This was also eliminated by adding in two Complementary Oligo Targets (COT1 and COT2) in addition to the SHS oligonucleotide into the loading cocktail. These three oligonucleotides are complementary to the 33 bases at the 5′-end of the unlabeled vWA amplicon strand and the 60 bases at its 3′-end and therefore compete for hybridization to the TMR-labeled amplicon strand. Incorporation of these three oligonucleotides in the Internal Lane Standard 600 (ILS600) eliminate both the split peak and n − 10/n − 18 artifact in PowerPlex^® 16 and PowerPlex^® ES amplification products without affecting sizing of alleles at the vWA locus or any locus in the PowerPlex^® 16, PowerPlex^® Y, PowerPlex^® ES, AmpFlSTR^® Profiler Plus^® ID, AmpFlSTR^® Cofiler^®, and AmpFlSTR^® SGM Plus^® kits.     

Blood group frequencies of the population of Trinidad and Tobago, West Indies.

The results of grouping tests performed on blood samples collected over a five-year period at the Trinidad and Tobago Forensic Science Centre are presented. The samples were tested using the ABO, PGM, EAP and GLO blood group systems. Phenotypic frequencies and allele frequencies for each system were calculated for the two major ethnic groups of the population, the African and East Indian. Matching probabilities, which can be used in the interpretation of physical evidence in forensic cases, were also calculated.     

Application of a simple extraction procedure using aqueous ammonia to the analysis of basic drugs in blood by gas chromatography

A simple and reliable previously reported extraction procedure has been extended to the analysis of a wide range of basic and neutral drugs in postmortem blood and other tissues. The method employs 200 microliters of blood treated with water and ammonia and extracted with diethyl ether. The concentrated extract is generally sufficiently clean for direct analysis by gas chromatography and high pressure liquid chromatography. Recovery, precision and linearity data are presented for selected drugs.     

An Empirical Note on Economic Freedom and Income Inequality

I report estimates for a fixed-effects model of country-level Gini coefficients as a function of economic freedom along with relevant control variables. Gini coefficients are drawn from the UNU/WIDER World Income Inequality Database Version 2.0a, while economic freedom is measured by the Fraser Institute's Economic Freedom of the World index. Controls are included for per capita income, political structure, education, demographics, and industrial composition. Over a broad range of freedom, the estimated relation between economic freedom and income inequality is positive, statistically significant, but relatively inelastic.