Mirror-Image Thymidine Discriminates against Incorporation of Deoxyribonucleotide Triphosphate into DNA and Repairs Itself by DNA Polymerases

DNA polymerases are known to recognize preferably d-nucleotides over l-nucleotides during DNA synthesis. Here, we report that several general DNA polymerases catalyze polymerization reactions of nucleotides directed by the DNA template containing an l-thymidine (l-T). The results display that the 5′–3′ primer extension of natural nucleotides get to the end at chiral modification site with Taq and Phanta Max DNA polymerases, but the primer extension proceeds to the end of the template catalyzed by Deep Vent (exo^–), Vent (exo^–), and Therminator DNA polymerases. Furthermore, templating l-nucleoside displays a lag in the deoxyribonucleotide triphosphate (dNTP) incorporation rates relative to natural template by kinetics analysis, and polymerase chain reactions were inhibited with the DNA template containing two or three consecutive l-Ts. Most interestingly, no single base mutation or mismatch mixture corresponding to the location of l-T in the template was found, which is physiologically significant because they provide a theoretical basis on the involvement of DNA polymerase in the effective repair of l-T that may lead to cytotoxicity

Antibody-Free Colorimetric Detection of Total Aflatoxins in Rice Based on a Simple Two-Step Chromogenic Reaction

The prevalently used immunoassays for fast screening of aftatoxins (AFs) usually cannot meet the requirement for simultaneous determination of total AFs (aflatoxin B₁ + aflatoxin B₂ + aflatoxin G₁ + aflatoxin G₂) due to the deficiency of highly group-specific antibodies. This paper describes a two-step chromogenic reaction based method to quantitatively detect total AFs in rice using colorimetric measurement without antibody. In the method, colorless AFs transform into green-colored indophenol products through the reaction with sodium hydroxide and 2,6-dibromoquinone-4-chloroimide (DBQC) successively, allowing selectively determining total AFs up to 3.9 μg/kg over other competitive mycotoxins under optimal conditions by a UV–vis spectrophotometer. In addition, the colorimetric measurement results of the rice samples agree well with that of a standard HPLC method, demonstrating the good reliability and applicability of the method. Uniquely, the method has potential for on-site detection of total AFs in rice when using a nylon membrane-based device

Efficient Compact-Layer-Free, Hole-Conductor-Free, Fully Printable Mesoscopic Perovskite Solar Cell

A compact-layer-free, hole-conductor-free, fully printable mesoscopic perovskite solar cell presents a power conversion efficiency of over 13%, which is comparable to that of the device with a TiO₂ compact layer. The different wettability of the perovskite precursor solution on the surface of FTO and TiO₂ possesses a significant effect on realizing efficient mesoscopic perovskite solar cell. This result shows a promising future in printable solar cells by further simplifying the fabrication process and lowering the preparation costs

Dual Supports by Cation Vacancies and Surface Optimization for CoNiSe₂‑Based Hybrid Supercapacitors with High Energy Density

Transition metal selenides as electrode materials for supercapacitors are becoming increasingly attractive, and effective modification strategies for improving their practical energy storage performance are highly desired. Herein, a dual modification strategy combined with surface laminating and introducing cation vacancies is utilized to optimize the polynary transition metal selenide CoNiSe2 in the surface and atomic levels. The as-obtained sample CNVS/rGO possesses well-developed surface chemical properties, optimized electron state, more exposed inner electroactive sites, and barrier-decreased kinetics. For the assembled asymmetric hybrid supercapacitor device, a high energy density of 106.2 Wh kg–1 at a power density of 0.77 KW kg–1 is achieved. Importantly, a pseudo-in-situ XPS test method and DFT calculations are conducted for better understanding of the modification mechanisms and electrochemical kinetics. This work presents a performance breakthrough; the corresponding modification strategy and kinetic studies are inspiring for the design of electrode materials in the related fields

Pt-Sensitized In₂O₃ Nanotubes for Sensitive Acetone Monitoring

Detecting 1 ppm acetone at high humidity is essential for a noninvasive diabetes diagnosis. Metal oxide gas sensors are a promising technology to achieve high sensitivity acetone monitoring. Here, we fabricated Pt-sensitized In2O3 nanotubes, and the gas-sensing performance was tested against eight gases. The fiber structure contributes to the uniform dispersion of Pt onto the In2O3. Pt-sensitized In2O3 nanotubes have lower optimal operating temperatures and higher sensitivity and selectivity than those of the In2O3 nanotubes. The 0.75 wt % Pt-In2O3 sensor has the maximum sensitivity (113) to 10 ppm acetone at 300 °C; the response and response time to 1 ppm acetone are 19.9 and 10 s, respectively. The response to 1 ppm acetone still has 9.83 at the relative humidity of 83%. It also has a low limit of detection (8.4 ppb) and good long-term stability (30 days). These results illustrate that Pt-sensitized In2O3 nanotubes have the potential for a noninvasive diabetes diagnosis