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In order to enhance the four‐way purification performance of PM, NOx, CO and HC emitted by automobile exhausts over woody La0.8Ce0.2Fe0.3Co0.7O3 perovskite‐type catalysts. First, the woody La0.8Ce0.2Fe0.3Co0.7O3 perovskite‐type catalysts were modified by nonthermal plasma (NTP). The physicochemical properties of the catalyst surface were characterized utilizing x‐ray diffractometer, Fourier‐transform infrared spectroscopy, x‐ray photoelectronic spectroscopy, scanning electron microscope and Brunauer–Emmett–Teller to analyze the effect of NTP on surface character of the catalyst samples. Second, NTP was combined with woody La0.8Ce0.2Fe0.3Co0.7O3 perovskite‐type catalysts to form in‐plasma catalysis purification (IPCP) systems. Finally, the four‐way purification performance of perovskite‐type catalysts were evaluated in the presence and absence of the plasma by simulation test bench. The results showed that NTP can enhance the four‐way purification performance for PM, NOx, CO and HC emitted by automobile exhausts over woody La0.8Ce0.2Fe0.3Co0.7O3 perovskite‐type catalysts. NTP can increase the specific surface area and porosity. When the input voltage, frequency and filling rate of IPCP systems are 15 kV, 15 Hz and 0.3, respectively, the maximum purification efficiency for PM, NOx, CO and HC are about 96%, 95%, 95%, and 84%. Moreover, four‐way purification mechanism of IPCP was deduced according to the experimental results. [ABSTRACT FROM AUTHOR]

Heterochiral DNA with hydrogen‐bonded and silver‐mediated base pairs have been constructed using complementary strands with nucleosides with α‐d or β‐d configuration. Anomeric phosphoramidites were employed to assemble the oligonucleotides. According to the Tm values and thermodynamic data, the duplex stability of the heterochiral duplexes was similar to that of homochiral DNA, but mismatch discrimination was better in heterochiral DNA. Replacement of purines by 7‐deazapurines resulted in stable parallel duplexes, thereby confirming Watson–Crick‐type base pairing. When cytosine was facing cytosine, thymine or adenine residues, duplex DNA formed silver‐mediated base pairs in the presence of silver ions. Although the CD spectra of single strands with α‐d configuration display mirror‐like shapes to those with the β‐d configuration, the CD spectra of the hydrogen‐bonded duplexes and those with a limited number of silver pairs show a B‐type double helix almost indistinguishable from natural DNA. Nonmelting silver ion–DNA complexes with entirely different CD spectra were generated when the number of silver ions was equal to the number of base pairs. [ABSTRACT FROM AUTHOR]

In order to reduce the emissions of pollutants from diesel exhaust, a kind of exhaust purification technology by the combination of non‐thermal plasma (NTP) with Nano‐CeO2 supported on the micro‐wood fiber filter is proposed, and a simulation test bench is designed to test the influence factors of purification efficiency. It can be seen from the simulation experiments, the purification efficiency for particulate matter (PM) and NOx can be enhanced from 37 and 28% to 53 and 38% when the content of Nano‐CeO2 is from 0 to 16.92 wt%. The test results also show that the purification efficiency of PM and NOx increases with the rising of temperature between 40 and 160°C. Furthermore, when the mass of PM is no more than 30 mg, the purification efficiency of PM and NOx increases with the rising of PM mass. At last, the experiment shows that when the input voltage is between 6 and 12 kV, the corresponding purification efficiency increases with the rising of voltage. Temperature 160°C, catalyst 16.92 wt%, input voltage 12 kV, and PM 30 mg are the best experimental conditions for this study, in which the corresponding purification of PM and NOx is 66 and 53%, respectively. This can provide an experimental basis for the practical application of NTP and wood fiber filters in the field of exhaust gas purification. [ABSTRACT FROM AUTHOR]

Isolated and consecutive heterochiral α‐dC– base pairs have been incorporated into 12‐mer oligonucleotide duplexes at various positions, thereby replacing Watson–Crick pairs. To this end, a new synthesis of the α‐d anomer of dC has been developed, and oligonucleotides containing α‐dC residues have been synthesized. Silver‐mediated base pairs were formed upon the addition of silver ions. Furthermore, we have established that heterochiral α‐dC–dC base pairs can approach the stability of a Watson–Crick pair, whereas homochiral dC–dC pairs are significantly less stable. A positional change of the silver‐mediated base pairs affects the duplex stability and reveals the nearest‐neighbor influence. When the number of silver ions was equivalent to the number of duplex base pairs (12), non‐melting silver‐rich complexes were formed. Structural changes have been supported by circular dichroism (CD) spectra, which showed that the B‐DNA structure was maintained whilst the silver ion concentration was low. At high silver ion concentration, silver‐rich complexes displaying different CD spectra were formed. [ABSTRACT FROM AUTHOR]

Abstract: 5‐Aza‐7‐deaza‐2′‐deoxyguanosine (dZ) forms a silver‐mediated base pair with dC. The metal ion pair represents a mimic of the H‐bonded Watson–Crick dG‐dC pair. The modified nucleoside displays a similar shape as the parent 2′‐deoxyguanosine from which it can be constructed by transposition of nitrogen‐7 to the bridgehead position‐5. It lacks the major groove binding site as the positional change moves the dG‐ acceptor position from nitrogen‐7 to nitrogen‐1. As a shape mimic of dG, it fits nicely in the DNA double helix. The purine–pyrimidine dZ‐dC hetero pair shows a relationship to the pyrimidine–pyrimidine dC‐dC homo base pair. The dZ‐dC pair forms a mismatch in the absence of silver ions and matches after addition of metal ions. Base‐pair formation was verified on self‐complementary 6‐mer duplexes and 12‐mer DNA with random composition by UV‐dependent Tm measurements. Modified silver‐mediated and hydrogen‐bonded canonical base pairs can coexist. The dZ‐Ag+‐dC base pair is slightly less stable than the dG‐dC pair, shows sequence dependence, and consumes one or two silver ions. These properties make the dZ‐Ag+‐dC pair suitable for programmable incorporation of silver ions in DNA which cannot be achieved by canonical base pairs. If the silver ion content is higher than the total number of base pairs the duplexes turn into very stable structures in which all base pairs are considered to be in the silver‐mediated pairing mode. [ABSTRACT FROM AUTHOR]

The stability of silver-mediated 'dC-dC' base pairs relies not only on the structure of the nucleobase, but is also sensitive to structural modification of the sugar moiety. 2′-Fluorinated 2′-deoxycytidines with fluorine atoms in the arabino (up) and ribo (down) configuration as well as with geminal fluorine substitution (anticancer drug gemcitabine) and the novel fluorescent phenylpyrrolo-gemcitabine (phPyrGem) have been synthesized. All the nucleosides display the recognition face of naturally occurring 2′-deoxycytidine. The nucleosides were converted into phosphoramidites and incorporated into 12-mer oligonucleotides by solid-phase synthesis. The addition of silver ions to DNA duplexes with a fluorine-modified 'dC-dC' pair near the central position led to significant duplex stabilization. The increase in stability was higher for duplexes with fluorinated sugar residues than for those with an unchanged 2′-deoxyribose moiety. Similar observations were made for 'dC-dT' pairs and to a minor extent for 'dC-dA' pairs. The increase in silver ion mediated base-pair stability was reversed by annulation of a pyrrole ring to the cytosine moiety, as shown for 2′-fluorinated phPyrGem in comparison with phenylpyrrolo-dC (phPyrdC). This phenomenon results from stereoelectronic effects induced by fluoro substitution, which are transmitted from the sugar moiety to the silver ion mediated base pairs. The extent of the effect depends on the number of fluorine substituents, their configuration, and the structure of the nucleobase. [ABSTRACT FROM AUTHOR]

α- d-Nucleosides are rare in nature but can develop fascinating properties when incorporated into DNA. This work reports on the first silver-mediated base pair constructed from two anomeric nucleosides: α-dC and β-dC. The hybrid base pair was integrated into the DNA and DNA/RNA double helix. A 12-mer duplex with α-dC and β-dC pair exhibits a higher thermal stability ( Tm=43 °C) than that incorporating the β-dC-Ag+-β-dC homo pair ( Tm=34 °C). Furthermore, α-dC shows excellent mismatch discrimination for DNA single nucleotide polymorphism (SNP). All four SNPs were identified on the basis of large Tm value differences measured in the presence of silver ions. High resolution melting was not required. [ABSTRACT FROM AUTHOR]

Formation of silver-mediated DNA was studied with oligonucleotides incorporating 8-aza-7-deazapurine, 7-deazapurine, and purine nucleosides. The investigation was performed on non-self-complementary duplexes with one or two modifications and self-complementary duplexes with an alternating dA-dT motif. Homo base pairs as well as base pair mismatches of dA analogues with dC and Watson-Crick pairs with dT were studied by stoichiometric silver ion titration and Tm measurements. N8-Glycosylated 8-aza-7-deazaadenine forms silver-ion-mediated base pairs capturing two silver ions (low silver content) whereas regularly glycosylated 8-aza-7-deazapurine, 7-deazapurine (c7Ad), and dA do not form comparable structures. Stable silver-mediated 'dA-dC' base pair mismatches were detected for all nucleosides. Two silver ions per base pair are bound by 8-aza-7-deazapurine whereas c7Ad binds only one silver ion. The situation is different when the equivalents of silver ions were increased to the number of total base pairs. Surprisingly, in 12-mer duplexes as well as in related 25-mer duplexes every base pair consumed one silver ion. [ABSTRACT FROM AUTHOR]

Structurally modified nucleosides are central players in the field of nucleic acid chemistry. Adenine-thymine (AT) pyrimido[4,5-d]pyrimidine furanosyl and pyranosyl arabinonucleosides have been synthesized for the first time. Single-crystal X-ray diffraction analysis reveals novel base pairs that, in synergy with the sugar residues, direct the emergence of distinct networks containing channels and cavities. The microscopic noncovalent connections can be translated into macroscopic levels in which robust organogels are formed by the furanoside but not the pyranoside. The influences of the sugars are also displayed by the different shaped superstructures of the free nucleosides in solution. The readout of the information in the base moiety is therefore tailored by the sugar configuration, and the interplays exert subtle effects on the structures, from solid to gel and to the solution state. The potential for forming these appealing base pairs and higher structures enables these intriguing nucleosides to serve as unique building blocks in various areas or to construct innovative nucleic acid structures. [ABSTRACT FROM AUTHOR]