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Even though dilute (unentangled) polymer solutions cannot act as gel-like sieving media, it has been shown that they can be used to separate DNA molecules in capillary electrophoresis. The separation then comes from sporadic, independent DNA–polymer collisions. We study polymer–polymer collisions in nanochannels (i.e., channels that are smaller than the normal size of the polymers), a situation where a polyelectrolyte is forced to migrate "through" isolated uncharged molecules during electrophoresis. We use Langevin dynamics simulations to explore the nature of these collisions and their effect on the net motion of the two polymer chains. We identify several types of collisions, including some that are unique to nanochannels. When the uncharged polymer is much larger than the polyelectrolyte, the system is reminiscent of gel electrophoresis, and we propose a modified empirical reptation model to explain the data, with an orientation factor that depends on the tube diameter. We also observe that the duration of a collision is a non-monotonic function of the polymer size ratio when the two chains are of comparable size, a surprising resonance-like phenomenon, which, combined with the asymmetric nature of molecular conformations during collision, suggests possible ratchet-like mechanisms that could be used to sort polyelectrolytes in nanodevices. [ABSTRACT FROM AUTHOR]

Unbalanced and degraded mixtures (UDM) are very common in forensic DNA analysis. For example, DNA signals from criminal suspects are masked by a large amount of DNA from victims, or cell-free fetal DNA (cffDNA) in maternal plasma is masked by a high background of maternal DNA. Currently, detecting minor DNA in these mixtures is complex and challenging. We developed a new set of SNP-SNP microhaplotypes with short amplicons, and we successfully genotyped them using the new method of amplification-refractory mutation system PCR (ARMS-PCR) combined with SNaPshot technology based on a capillary electrophoresis (CE) platform. This panel reflects a high polymorphism in the Southwest Chinese Han population and thus has excellent potential for mixture studies. We evaluated the feasibility of this panel for UDM detection and noninvasive prenatal paternity testing (NIPPT). Fifteen SNP-SNPs detected minor DNA of homemade DNA mixtures, with a sensitivity of 0.025–0.05 ng and a specificity of 1:1,000. In addition, the panel successfully genotyped degraded DNA from single and mixed samples. Finally, 15 SNP-SNPs were applied to 26 trios. All samples displayed positive results with at least one marker to detect cffDNA. Besides, all fetal alleles in maternal plasma were confirmed by genotyping fetal genomic DNA from amniocentesis and paternal genomic DNA from peripheral blood. The results indicated that the SNP-SNP strategy based on the CE platform was useful for UDM detection and NIPPT. [ABSTRACT FROM AUTHOR]

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This study reported a large cohort of fetal blood analysis of various hemoglobinopathies.A total of 371 fetal blood specimens were recruited. Complete blood count and hemoglobin (Hb) analysis using capillary electrophoresis were performed. Genotypes were defined by DNA analysis.Among 371 fetuses, 36 were non-thalassemic and 29 thalassemia genotypes were identified in the remaining 335 fetuses. Fetuses with β-thalassemia and Hb E traits, homozygous Hb E, and Hb E-β0-thalassemia had similar hematological parameters as those of non-thalassemic. However, the levels of Hb A in β-thalassemia and Hb E traits were approximately half of that observed in the non-thalassemic fetuses. As for Hb E, fetuses with a single copy of the βE-globin gene in the Hb E trait and Hb E-β0-thalassemia had lower Hb E levels as compared to that of the homozygous Hb E. For α-thalassemia, fetuses with one or two α-globin gene defects had small changes in hematological parameters, but variable Hb Bart’s levels were observed. Fetuses with Hb H and Hb H-CS diseases had moderate anemia, whereas those with homozygous Hb CS and Hb Bart’s hydrops fetalis had severe anemia. Identification of the fetuses with Hb Bart’s hydrops fetalis with various genetic interactions allows the exact re-location of electrophoretic mobilities of various embryonic Hbs.This study confirmed the genetic heterogeneity of hemoglobinopathies among the fetuses and fetal blood analysis are useful for presumptive diagnosis of hemoglobinopathies. The results should facilitate a prevention and control program of hemoglobinopathies in the region. [ABSTRACT FROM AUTHOR]

\nHIGHLIGHTShort tandem repeat (STR) analysis of a perpetrator’s touch DNA on a victim’s skin is crucial in forensic science. This study evaluates the accuracy of male contributor assignment from skin-to-skin transferred touch DNA using STR profiling with and without whole-genome amplification (WGA). Each of 32 touch DNA samples was collected from a woman’s wrist after being grasped by a man, with each sample divided into three aliquots: one left as a non-WGA sample, another subjected to WGA via multiple displacement amplification (MDA), and the third amplified using modified T oligo-primed PCR (TOP-PCR). Ninety-six (32 × 3) STR profiles were analysed via capillary electrophoresis (CE) and massively parallel sequencing (MPS), with male contributors assigned using EuroForMix. Among the 10 Qubit-detectable samples of the 32 touch DNA samples, the accuracy rates of male contributor assignment using CE were 50% (non-WGA), 40% (MDA) and 70% (TOP-PCR) and using MPS were 100.0% (non-WGA), 50.0% (MDA), and 80.0% (TOP-PCR). For the 22 Qubit-undetectable samples, the accuracy rates using CE were 13.6% (non-WG3A), 4.5% (MDA) and 59.1% (TOP-PCR) and using MPS were 68.2% (non-WGA), 0% (MDA-) and 77.3% (TOP-PCR). In conclusion, TOP-PCR may improve the accuracy of male contributor assignment for Qubit-undetectable samples.WGA using modified TOP-PCR may enhance forensic STR analysis of low-quality touch DNA samples. [ABSTRACT FROM AUTHOR]