Copper-Catalyzed Nondecarboxylative Cross Coupling of Alkenyltrifluoroborate Salts with Carboxylic Acids or Carboxylates: Synthesis of Enol Esters

A mild copper-catalyzed Chan–Lam–Evans type cross-coupling reaction for the regioselective and stereospecific preparation of (<i>E</i>)- or (<i>Z</i>)-enol esters is described. The method couples carboxylate salts or carboxylic acids with potassium alkenyltrifluoroborate salts in the presence of catalytic CuBr and DMAP with 4 Å molecular sieves under O₂ at 60 °C. Overall, this method demonstrates carboxylic acids as suitable reaction partners for nondecarboxylative copper-catalyzed cross-couplings to form C–O bonds in an Ullmann-like reaction

Additional file 1: Table S1. of eRFSVM: a hybrid classifier to predict enhancers-integrating random forests with support vector machines

The datasets for training of cell lines from ENCODE. Table S2. Results training on four cell lines. Table S3. The peaks of different tissues from Roadmaps. Table S4. The datasets for training of different tissues from Roadmap. Table S5. Results training on different tissues with ChIP-Seq datasets. Table S6. Results training on tissues with DEEP-FANTOM5. Table S7. Results training on tissues with sequence features. Table S8. Results training on tissues with DEEP-FANTOM5. (DOCX 20 kb

Density Functional Theory Mechanistic Study of the Reduction of CO₂ to CH₄ Catalyzed by an Ammonium Hydridoborate Ion Pair: CO₂ Activation via Formation of a Formic Acid Entity

Density functional theory computations have been applied to gain insight into the CO₂ reduction to CH₄ with Et₃SiH, catalyzed by ammonium hydridoborate <b>1</b> ([TMPH]⁺[HB­(C₆F₅)₃]⁻, where TMP = 2,2,6,6-tetramethylpiperidine) and B­(C₆F₅)₃. The study shows that CO₂ is activated through the concerted transfer of H^δ+ and H^δ− of <b>1</b> to CO₂, giving a complex (<b>IM2</b>) with a well-formed HCOOH entity, followed by breaking of the O–H bond of the HCOOH entity to return H^δ+ to TMP, resulting in an intermediate <b>2</b> ([TMPH]⁺[HC­(O)­OB­(C₆F₅)₃)]⁻), with CO₂ being inserted into the B–H bond of <b>1</b>. However, unlike CO₂ insertion into transition-metal hydrides, the direct insertion of CO₂ into the B–H bond of <b>1</b> is inoperative. The computed CO₂ activation mechanism agrees with the experimental synthesis of <b>2</b> via reacting HCOOH with TMP/B­(C₆F₅)₃. Subsequent to the CO₂ activation and B­(C₆F₅)₃-mediated hydrosilylation of <b>2</b> to regenerate the catalyst (<b>1</b>), giving HC­(O)­OSiEt₃ (<b>5</b>), three hydride-transfer steps take place, sequentially transferring H^δ− of Et₃SiH to <b>5</b> to (Et₃SiO)₂CH₂ (<b>6</b>, the product of the first hydride-transfer step) to Et₃SiOCH₃ (<b>7</b>, the product of the second hydride-transfer step) and finally resulting in CH₄. These hydride transfers are mediated by B­(C₆F₅)₃ via two S_N2 processes without involving <b>1</b>. B­(C₆F₅)₃ acts as a hydride carrier that, with the assistance of a nucleophilic attack of <b>5</b>–<b>7</b>, first grabs H^δ− from Et₃SiH (the first S_N2 process), giving HB­(C₆F₅)₃^–, and then leave H^δ− of HB­(C₆F₅)₃^– to the electrophilic C center of <b>5</b>–<b>7</b> (the second S_N2 process). The S_N2 processes utilize the electrophilic and nucleophilic characteristics possessed by the hydride acceptors (<b>5</b>–<b>7</b>). The hydride-transfer mechanism is different from that in the CO₂ reduction to methanol catalyzed by N-heterocyclic carbene (NHC) and PCP-pincer nickel hydride ([Ni]­H), where the characteristic of possessing a CO double bond of the hydride acceptors is utilized for hydride transfer. The mechanistic differences elucidate why the present system can completely reduce CO₂ to CH₄, whereas NHC and [Ni]H catalysts can only mediate the reduction of CO₂ to [Si]­OCH₃ and catBOCH₃, respectively. Understanding this could help in the development of catalysts for selective CO₂ reduction to CH₄ or methanol

Sorption of tetracycline on biochar derived from rice straw under different temperatures

<div><p>Biochars produced from the pyrolysis of waste biomass under limited oxygen conditions could serve as adsorbents in environmental remediation processes. Biochar samples derived from rice straw that were pyrolyzed at 300 (R300), 500 (R500) and 700°C (R700) were used as adsorbents to remove tetracycline from an aqueous solution. Both the Langmuir and Freundlich models fitted the adsorption data well (R² > 0.919). The adsorption capacity increased with pyrolysis temperature. The R500 and R700 samples exhibited relative high removal efficiencies across a range of initial tetracycline concentrations (0.5mg/L-32mg/L) with the maximum (92.8%–96.7%) found for adsorption on R700 at 35°C. The relatively high surface area of the R700 sample and π–π electron-donor acceptor contributed to the high adsorption capacities. A thermodynamic analysis indicated that the tetracycline adsorption process was spontaneous and endothermic. The pH of solution was also found to influence the adsorption processes; the maximum adsorption capacity occurred at a pH of 5.5. These experimental results highlight that biochar derived from rice straw is a promising candidate for low-cost removal of tetracycline from water.</p></div

Effect of pH on adsorption capacity for tetracycline sorption on biochars.

<p>The concentration of tetracycline solution was 32 mg/L. Values are triplicate means ± SD. Letters indicate significant differences among treatments at a level of p < 0.05(Tukey test).</p

Thermodynamic parameters for tetracycline sorption on biochars with initial concentration of tetracycline changing from 0.5 mg/L to 32 mg/L.

<p>Thermodynamic parameters for tetracycline sorption on biochars with initial concentration of tetracycline changing from 0.5 mg/L to 32 mg/L.</p

The Human Antiviral Factor TRIM11 Is under the Regulation of HIV-1 Vpr

<div><p>TRIM11 has been reported to be able to restrict HIV-1 replication, but the detailed aspects of the interfering mechanisms remain unclear. In this study, we demonstrated that TRIM11 mainly suppressed the early steps of HIV-1 transduction, resulting in decreased reverse transcripts. Additionally, we found that TRIM11 could inhibit HIV-1 long terminal repeat (LTR) activity, which may be related to its inhibitory effects on NF-κB. Deletion mutant experiments showed that the RING domain of TRIM11 was indispensable in inhibiting the early steps of HIV-1 transduction but was dispensable in decreasing NF-κB and LTR activities. Moreover, we found that low levels of Vpr decreased TRIM11 protein levels, while high levels increased them, and these regulations were independent of the VprBP-associated proteasome machinery. These results suggest that the antiviral factor TRIM11 is indirectly regulated by HIV-1 Vpr through unknown mechanisms and that the concentration of Vpr is essential to these processes. Thus, our work confirms TRIM11 as a host cellular factor that interferes with the early steps of HIV-1 replication and provides a connection between viral protein and host antiviral factors.</p></div

Pore structure of biochars derived from rice straw.

<p>Pore structure of biochars derived from rice straw.</p

Effects of TRIM11 on the early steps of HIV-1 replication.

<p><b>A</b>. HEK293 cells stably expressing TRIM11 or control pCDH vector were inoculated with 50 ng/ml (p24^gag) of HIV-1 Vpr⁻ viruses and analyzed by qPCR for late reverse transcripts and 2-LTR circle DNA at 24 hpi and integrated DNA at 14 day post infection (dpi). <b>B</b>. TRIM11 knock-down and control cell lines were inoculated with 50 ng/ml (p24^gag) of HIV-1 Vpr⁻ viruses and analyzed by qPCR for late reverse transcripts and 2-LTR circle DNA at 24 hpi and integrated DNA at 14 dpi. Error bars represent the standard deviations from three independent replicates of the same experiment. *P<0.05.</p

Effects of proteasomes and VprBP on the regulation of TRIM11 by Vpr.

<p><b>A</b>. HEK293 cells were cotransfected with different amounts of Vpr and 300 ng Myc-TRIM11. Twelve hours post-transfection, cells were treated with DMSO or MG132 for another 12 h. Cell lysates were immunoblotted with the indicated antibodies. <b>B</b>. HEK293 cells stably transduced with shRNA targeting VprBP or GFP were cotransfected with different amounts of Vpr and 300 ng Myc-TRIM11. Twenty-four hours post-transfection, cell lysates were immunoblotted with the indicated antibodies. The numbers under each lines display the relative ratios between the Myc signals and actin signals. Representative results from three separate experiments are shown.</p