Template tailoring: Accurate determination of heterozygous alleles using peptide nucleic acid and dideoxyNTP

Measurement of the length of DNA fragments plays a pivotal role in genetic mapping, disease diagnostics, human identification and forensic applications. PCR followed by electrophoresis is used for DNA length measurement of STRs, a process that requires labeled primers and allelic ladders as standards to avoid machine error. Sequencing‐based approaches can be used for STR analysis to eliminate the requirement of labeled primers and allelic ladder. However, the limiting factor with this approach is unsynchronized polymerization in heterozygous sample analysis, in which alleles with different lengths can lead to imbalanced heterozygote peak height ratios. We have developed a rapid DNA length measurement method using peptide nucleic acid and dideoxy dNTPs to “tailor” DNA templates for accurate sequencing to overcome this hurdle. We also devised an accelerated “dyad” pyrosequencing strategy, such that the combined approach can be used as a faster, more accurate alternative to de novo sequencing. Dyad sequencing interrogates two bases at a time by allowing the polymerase to incorporate two nucleotides to DNA template, cutting the analysis time in half. In addition, for the first time, we show the effect of peptide nucleic acid as a blocking probe to stop polymerization, which is essential to analyze the heterozygous samples by sequencing. This approach provides a new platform for rapid and cost‐effective DNA length measurement for STRs and resequencing of small DNA fragments.     

First-principles calculations of nitrogen-doped antimony triselenide: A prospective material for solar cells and infrared optoelectronic devices

This study is focused on calculation of the electronic structure and optical properties of non-metal doped Sb2Se3 using the first-principles method. One and two N atoms are introduced to Sb and Se sites in a Sb₂Se₃ crystal. When one and two N atoms are introduced into the Sb₂Se₃ lattice at Sb sites, the electronic structure shows that the doping significantly modifies the bandgap of Sb₂Se₃ from 1.11 eV to 0.787 and 0.685 eV, respectively. When N atoms are introduced to Se sites, the material shows a metallic behavior. The static dielectric constants ε1(0) for Sb₁₆Se₂₄, Sb₁₅N₁Se₂₄, Sb₁₄N₂Se₂₄, Sb₁₆Se₂₃N₁, and Sb₁₆Se₂₂N₂ are 14.84, 15.54, 15.02, 18.9, and 39.29, respectively. The calculated values of the refractive index n(0) for Sb₁₆Se₂₄, Sb₁₅N₁Se₂₄, Sb₁₄N₂Se₂₄, Sb₁₆Se₂₃N₁, and Sb₁₆Se₂₂N₂ are 3.83, 3.92, 3.86, 4.33, and 6.21, respectively. The optical absorbance and optical conductivity curves of the crystal for N-doping at Sb sites show a significant redshift towards the short-wave infrared spectral region as compared to N-doping at Se sites. The modulation of the static refractive index and static dielectric constant is mainly dependent on the doping level. The optical properties and bandgap narrowing effect suggest that the N-doped Sb₂Se₃is a promising new semiconductor and can be a replacement for GaSb due to its very similar bandgap and low cost.     

Fabrication and characterization of amidoxime-functionalized silica decorated with copper: a catalytic assembly for rapid reduction of dyes

In this study, amidoxime-functionalized silica decorated with copper (AFS-Cu) was fabricated and tested for its catalytic application. Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were employed to characterize its structure and morphology. The application of AFS-Cu as a catalyst for the catalytic reduction of methylene blue (MB) in aqueous media using NaBH₄ as reductant was evaluated. The ability to reuse as well as the effect of catalyst dose and pH of solution on the catalytic activity was investigated. The reduction of MB followed pseudo-first-order kinetics and the rate constant (k) was 0.6224 min^-1. AFS-Cu was found to be a highly effective catalyst for MB reduction reaction and can be easily recovered and reused several times with no appreciable loss of catalytic activity.     

Antiparasitic activities of bimetallic N-heterocyclic carbene gold(I) complexes with ferrocene ligands: Relevance of chlorido and phosphino ligands

Gold(I) complexes carrying imidazole-2-ylidene ligands and ferrocene substituents were prepared. Their activities against protozoal Leishmania major and Toxoplasma gondii parasites were analyzed. Certain gold(I) complexes with chlorido and 1,1′-bis(triphenylphosphino)ferrocene ligands revealed promising antiparasitic effects. The new chlorido complexes 5b and 5c showed high activities against T. gondii tachyzoites and L. major promastigotes while the new ferrocene-bridged bis-gold(I) complexes 8a and 8b were particularly active against L. major amastigotes and considerably selective as to toxicity results from Vero cells and macrophages.     

Liquid-liquid equilibrium for the ternary system ethanol/toluene/n-decane: a correction to the existing coexistence curve and NRTL parameters

A correction to the reported liquid–liquid equilibrium parameters using the non-random two liquid (NRTL) thermodynamic model for the ethanol/toluene/n-decane system at 298 K is reported. The parameters were calculated by minimising the residual between the calculated coexistence and the experimental compositions. However, to obtain a physically plausible coexistence curve, a parameter in the NRTL model had to be fixed. This highlights the importance of assessing the entire coexistence curve, as opposed to only comparing the calculated compositions to the experimental data points. This is because undertaking the regression for all the available parameters will result in a smaller residual and better fit of the calculated points to the experimental points. This leads to an apparent improved fit but the complete coexistence curve will show that the parameters are not physically plausible.     

Strain sensors based on carbon nanotubes-cuprous oxide composite

This paper presents the design, fabrication and experimental results of carbon nanotubes-cuprous oxide (CNTs-Cu₂O) composite based strain sensors. The press-tablets were fabricated from the blend of CNTs (25 wt%) and Cu₂O (75 wt%) at a pressure of 353 MPa. The diameter of multiwalled carbon nanotubes (MWCNTs) varied between 10 and 30 nm. The sizes of Cu₂O micro-particles were in the range of 3-4 μm. The thickness of the press-tablets was 1 mm. The samples were installed on the polymer elastic beam by glue. The electric contacts to the samples were made by silver paste. The inter-electrodes distance (length) and diameter of the surface-type samples were in the range of 6-8 mm and 10 mm, respectively. The DC resistance of the strain sensors increases under tension and decreases under compression, while the average strain sensitivities are in the range of 44-46 and 24-28 for tension and compression, respectively. The simulation is in good agreement with the experimental results.     

Determination of selenium in animal tissue samples using radioisotope induced X-ray fluorescence

A summary of sources of background affecting gamma-ray spectrometers and methods for eliminating each are discussed, along with practical cost/benefit ratios. Background contributed by samples generally defines practical levels for system background. The practical bottom line can be obtained for relatively modest costs. A realistic bottom line is attained in underground systems when the major contributions to the background come from cosmogenically produced⁶⁸Ge and double-beta decay of⁷⁶Ge in the detector. The true bottom line is reached with isotopically enriched detectors that eliminate these two chemically inseparable radioactive impurities. Data from isotopically enriched detectors are presented.     

The photochemistry of proaporphines: a new route to the aporphines

Proaporphines undergo light catalyzed rearrangement. Pakistanamine ($\text{1}$) is thus converted into lumipakistanine ($\text{2}$), while pronuciferine ($\text{7}$) and N-acetylnorpronuciferine ($\text{8}$) afford the corresponding C-9 hydroxylated aporphines $\text{9}$ and $\text{10}$. Possible biogenetic schemes for the formation of C-8, C-9-, and C-8,9-substituted aporphines are presented.     

Thermal analysis of mercury(I) sulfate and mercury(II) sulfate

The thermal decomposition of mercury(I) and (II) sulfates has been investigated by thermogravimetry. The solid-state decomposition products have been characterized by infrared and Raman spectroscopy, mass spectrometry and an X-ray diffraction method. It is concluded that mercury(I) sulfate decomposes in two steps, initially forming a mixture of metallic mercury and mercury(II) sulfate — the latter subsequently decomposes without forming a stable intermediate. The stoichiometry of disproportionation of mercury(I) sulfate and the thermal stability range of mercury(I) and mercury(II) sulfates have been established.

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Zusammenfassung Die thermische Zersetzung von Quecksilber(I) und (II)-sulfaten wurde durch Thermogravimetrie untersucht. Die Festphasen-Zersetzungsprodukte wurden durch Infrarot- und Ramanspektroskopie, Massenspektrometrie und Röntgendiffraktion charakterisiert. Es wurde gefolgert, dass Quecksilber(I)sulfat in zwei Stufen zersetzt wird, unter anfänglicher Bildung eines Gemisches von metallischem Quecksilber und Quecksilber(II)-sulfat, welches in der Folge ohne Bildung eines stabilen Zwischenproduktes zersetzt wird. Die Stöchiometrie der Disproportionierung des Quecksilber(I)sulfats und der Bereich der Thermostabilität der Quecksilber(I) und Quecksilber(II)sulfate wurden ermittelt.

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Résumé La décomposition thermique des sulfates de mercure(I) et de mercure(II) a été suivie par TG. On a caractérisé les produits de la décomposition en phase solide par spectroscopies infrarouge et Raman, spectrométrie de masse et diffraction des rayons X. On en a conclu que le sulfate de mercure(I) se décompose en deux étapes, formant initialement un mélange de mercure métallique et de sulfate de mercure(II), ce dernier se décomposant ensuite sans formation d'un intermédiaire stable. Les proportions stoechiométriques de la dismutation du sulfate de mercure(I) et de l'intervalle de stabilité thermique des sulfates de mercure(I) et de mercure(II) ont été établis.

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Chimeric streptogramin-tyrocidine antibiotics that overcome streptogramin resistance

Streptogramin antibiotics are comprised of two distinct chemical components: the type A polyketides and the type B cyclic depsipeptides. Clinical resistance to the type B streptogramins can occur via enzymatic degradation catalyzed by the lyase Vgb or by target modification through the action of Erm ribosomal RNA methyltransferases. We have prepared through chemical and chemo-enzymatic approaches a series of chimeric antibiotics composed of elements of type B streptogramins and the membrane-active antibiotic tyrocidine that evade these resistance mechanisms. These new compounds show broad antibiotic activity against gram-positive bacteria including a number of important pathogens, and chimeras appear to function by a mechanism that is distinct from their parent antibiotics. These results allow for the development of a brand new class of antibiotics with the ability to evade type B streptogramin-resistance mechanisms.