Simultaneous CT-13C and VT-15N chemical shift labelling: Application to 3D NOESY-CH3NH and 3D 13C,15N HSQC-NOESY-CH3NH

Based on the HSQC scheme, we have designed a 2D heterocorrelated experiment which combines constant time (CT) ¹³C and variable time (VT) ¹⁵N chemical shift labelling. Although applicable to all carbons, this mode is particularly suitable for simultaneous recording of methyl-carbon and nitrogen chemical shifts at high digital resolution. The methyl carbon magnetisation is in the transverse plane during the whole CT period (1/J_CC=28.6 ms). The magnetisation originating from NH protons is initially stored in the 2H_zN_z state, then prior to the VT chemical shift labelling period is converted into 2H_zN_y coherence. The VT -¹⁵N mode eliminates the effect of ¹ J _N,CO and ^1,2 J _N,CA coupling constants without the need for band-selective carbon pulses. An optional editing procedure is incorporated which eliminates signals from CH₂ groups, thus removing any potential overlap with the CH₃ signals. The CT-¹³CH₃,VT-¹⁵N HSQC building block is used to construct two 3D experiments: 3D NOESY-CH₃NH and 3D ¹³C,¹⁵N HSQC-NOESY-CH₃NH. Combined use of these experiments yields proton and heteronuclear chemical shifts for moieties experiencing NOEs with CH₃ and NH protons. These NOE interactions are resolved as a consequence of the high digital resolution in the carbon and nitrogen chemical shifts of CH₃ and NH groups, respectively. The techniques are illustrated using a double labelled sample of the CH domain from calponin.     

Mutational fitness landscape of human influenza H3N2 neuraminidase

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Simultaneous quantification of N2, NH3 and N2O emissions from a flooded paddy field under different N fertilization regimes

Gaseous nitrogen (N) emissions, especially emissions of dinitrogen (N₂) and ammonia (NH₃), have long been considered as the major pathways of N loss from flooded rice paddies. However, no studies have simultaneously evaluated the overall response of gaseous N losses to improved N fertilization practices due to the difficulties to directly measure N₂ emissions from paddy soils. We simultaneously quantified emissions of N₂ (using membrane inlet mass spectrometry), NH₃ and nitrous oxide (N₂O) from a flooded paddy field in southern China over an entire rice‐growing season. Our field experiment included three treatments: a control treatment (no N addition) and two N fertilizer (220 kg N/ha) application methods, the traditional surface application of N fertilizer and the incorporation of N fertilizer into the soil. Our results show that over the rice‐growing season, the cumulative gaseous N losses from the surface application treatment accounted for 13.5% (N₂), 19.1% (NH₃), 0.2% (N₂O) and 32.8% (total gaseous N loss) of the applied N fertilizer. Compared with the surface application treatment, the incorporation of N fertilizer into the soil decreased the emissions of NH₃, N₂ and N₂O by 14.2%, 13.3% and 42.5%, respectively. Overall, the incorporation of N fertilizer into the soil significantly reduced the total gaseous N loss by 13.8%, improved the fertilizer N use efficiency by 14.4%, increased the rice yield by 13.9% and reduced the gaseous N loss intensity (gaseous N loss/rice yield) by 24.3%. Our results indicate that the incorporation of N fertilizer into the soil is an effective agricultural management practice in ensuring food security and environmental sustainability in flooded paddy ecosystems.     

Oxygen Degradation in Mesoporous Al2O3/CH3NH3PbI3‐xClx Perovskite Solar Cells: Kinetics and Mechanisms

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market‐competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen‐induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build‐up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge‐extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen.     

Computational studies of H5N1 hemagglutinin binding with SA-alpha-2, 3-Gal and SA-alpha-2, 6-Gal

For influenza H5N1 hemagglutinin, a switch from SA-alpha-2, 3-Gal to SA-alpha-2, 6-Gal receptor specificity is a critical step leading to the conversion from avian-to-human to human-to-human infection. Therefore, the understanding of the binding modes of SA-alpha-2, 3-Gal and SA-alpha-2, 6-Gal to H5N1 hemagglutinin will be very important for the examination of possible mutations needed for going from an avian to a human flu virus. Based on the available H5N1 hemagglutinin crystal structure, the binding profiles between H5N1 hemagglutinin and two saccharide ligands, SA-alpha-2, 3-Gal and SA-alpha-2, 6-Gal, were investigated by ab initio quantum mechanics, molecular docking, molecular mechanics, and molecular dynamics simulations. It was found that SA-alpha-2, 3-Gal has strong multiple hydrophobic and hydrogen bond interactions in its trans conformation with H5N1 hemagglutinin, whereas the SA-alpha-2, 6-Gal only shows weak interactions in a different conformation (cis type).     

Chronic alcoholization-induced damage to astroglia and intensification of lipid peroxidation in the rat brain: Protector effect of hydrated form of fullerene C<Subscript>60</Subscript>

We studied the intensity of lipid peroxidation (LP) and the amount of a marker of astrocytes (glial fibrillary acidic protein, GFAP) in tissues of the rat brain under conditions of long-lasting consumption (12 weeks) of ethyl alcohol, as well as the protective effects of peroral administration of hydrated forms of fullerene ?₆₀ (?₆₀HyFn, FWS, fullerene water solutions). Consumption of ethanol resulted in a rise in the amount of molecular markers of oxidative stress (thiobarbiturate-active compounds) in the cerebral tissues. The level of the filamentous GFAP form in the hippocampus and cerebral cortex of alcoholized animals decreased significantly, which can be a result of death of the population of GFAP-imunnoreactive astrocytes in the brain. In the brain of rats after systematic consumption of both ethanol and an aqueous solution of hydrated fullerenes ?₆₀, the amounts of products of lipid peroxidation and of the astroglial marker did not differ significantly from the respective indices in the control animals. Our data demonstrate the efficiency of hydrated fullerenes as pathogenetic therapeutic remedies for elimination of the negative effects of ethyl alcohol on the CNS.     

Quenching of electronically excited N2 molecules and Tb3+/Eu3+ ions by polyatomic sulfur‐containing gases upon triboluminescence of inorganic lanthanide salts

The triboluminescence of Eu₂(SO₄)₃·8H₂O and Tb₂(SO₄)₃·8H₂O crystals in an atmosphere of sulfur dioxide (SO₂) or sulfur hexafluoride (SF₆) was studied. Quenching of the gaseous (emitter N₂) and solid‐state (emitter Ln³⁺) components of the triboluminescence (TL) emission spectrum was seen when compared with the TL spectra of the crystals in air. One reason for the quenching is a reduction in the effective charge both on the crystal surface and in micro‐cracks under an SO₂ or SF₆ atmosphere, leading to a decrease in the probability of electrical breakdown and a reduction in electric field strength responsible for the electroluminescence excitation of lanthanide ions in TL. In an SO₂ atmosphere, there is an additional mode of quenching, as confirmed by quenching of the crystal photoluminescence (emitter Ln³⁺). It is supposed that this quenching is due to an exchange of energy on electronic excitation of the lanthanide ions to the vibrational sublevels of the SO₂ molecules adsorbed on the crystal surface. Another additional channel of TL quenching originates from non‐radiative transfer of excitation energy during collisions between the *N₂ and SO₂ molecules in the gaseous phase.     

Effects of N2,N2-dimethylguanosine on RNA structure and stability: crystal structure of an RNA duplex with tandem m2 2G:A pairs

Methylation of the exocyclic amino group of guanine is a relatively common modification in rRNA and tRNA. Single methylation (N²-methylguanosine, m²G) is the second most frequently encountered nucleoside analog in Escherichia coli rRNAs. The most prominent case of dual methylation (N²,N²-dimethylguanosine, m²₂G) is found in the majority of eukaryotic tRNAs at base pair m²₂G26:A44. The latter modification eliminates the ability of the N² function to donate in hydrogen bonds and alters its pairing behavior, notably vis-à-vis C. Perhaps a less obvious consequence of the N²,N²-dimethyl modification is its role in controlling the pairing modes between G and A. We have determined the crystal structure of a 13-mer RNA duplex with central tandem m²₂G:A pairs. In the structure both pairs adopt an imino-hydrogen bonded, pseudo-Watson–Crick conformation. Thus, the sheared conformation frequently seen in tandem G:A pairs is avoided due to a potential steric clash between an N²-methyl group and the major groove edge of A. Additionally, for a series of G:A containing self-complementary RNAs we investigated how methylation affects competitive hairpin versus duplex formation based on UV melting profile analysis.     

Interactions of elevated CO2, NH3 and O3 on mycorrhizal infection,gas exchange and N metabolism in saplings of Scots pine

Four-year-old saplings of Scots pine (Pinus sylvestris) (L.) were exposed for 11 weeks in controlled-environment chambers to charcoad-filtered air, or to charcoal-filtered air supplemented with NH₃ (40 g m^–3), O₃ (110 g m^–3 during day/ 40 g m^–3 during night) or NH₃+O₃. All treatments were carried out at ambient (259 L L^–1) and at elevated CO₂ concentration (700 L L^–1). Total tree biomass, mycorrhizal infection, net CO₂ assimilation (P_n), stomatal conductance (g_s), transpiration of the shoots and NH₃ metabolization of the needles were measured. In ambient CO₂ (1) gaseous NH₃ decreased mycorrhizal infection, without significantly affecting tree biomass or N concentration and it enhanced the activity of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in one-year-old needles; (2) ozone decreased mycorrhizal infection and the acitivity of GS in the needles, while it increased the activity og GDH; (3) exposure to NH₃+O₃ lessened the effects of single exposures to NH₃ and O₃ on reduction of mycorrhizal infection and on increase in GDH activity. Similar lessing effects on mycorrhizal infection as observed in trees exposed to NH₃+O₃ at ambient CO₂, were measured in trees exposed to NH₃+O₃ at elevated CO₂. Exposure to elevated CO₂ without pollutants did not significantly affect any of the parameters studied, except for a decrease in the concentration of soluble proteins in the needles. Elevated CO₂ _NH₃ strongly decreased root branching and mycorrhizal infection and temporarily stimulated P_n and g_s. The exposure to elevated CO₂+NH₃+O₃ also transiently stimulated P_n. The possible mechanisms underlying and integrating these effects are discussed. Elevated CO₂ clearly did not alleviate the negative effects of NH₃ and O₃ mycoorhiral infection. The significant reduction of mycorrhizal infection after exposure to NH₃ or O₃, observed before significant changes in gas exchange or growth occurred, suggest the use of mycorrhizal infection as an early indicator for NH₃ and O₃ induced stress.Abbreviations DW dry weight - FA filtered air - FA_a filtered air at ambient CO₂ - FA_e filtered air at elevated CO₂ - FW fresh weight - GDH glutamate dehydrogenase - GS glutamine synthetase - g_s stomatal conductance - P_n net CO₂ assimilation - RWR root weight ratio - SRL specific root length     

Synthesis of trialkyl[60]fullerene C60(CH2SiMe3)3H and its potassium and rhodium(I) complexes

The reaction of [60]fullerene with Me₃SiCH₂MgCl in 1,2-Cl₂C₆H₄/THF (1/1) under dry air afforded a bis-alkyl adduct, C₆₀(CH₂SiMe₃)₂ (1), in 54% yield. Treatment of 1 with Me₃SiCH₂MgCl in THF under argon then afforded a trialkyl[60]fullerene, C₆₀(CH₂SiMe₃)₃H (2), in 37% yield. Further treatment of 2 with KO^tBu gave a potassium salt, [K(thf)_n][C₆₀(CH₂SiMe₃)₃] (3), which was then converted to a C_s-symmetric Rh(I) complex, Rh[η⁵-C₆₀(CH₂SiMe₃)₃](1,5-cyclooctadiene) (4), in 91% yield.     

Temperature dependence of the generalized frequency distribution of water molecules: comparison of experiments and molecular dynamics simulations

The results of inelastic neutron scattering experiments on water in the temperature interval 300–623 K along the coexistence curve are compared with data obtained from molecular dynamics simulations. In general, a good agreement between experiments and calculations is observed and it serves as a satisfactory test of the potential models employed. The temperature dependence of the generalized frequency distribution of water molecules obtained by both experiment and computer simulation demonstrates the accordance with the temperature evolution of the water structure, extracted from neutron and X-ray diffraction measurements.     

Effects of N source on proton excretion,ionic balance and growth ofAlnus glutinosa (L.) Gaertner: comparison of N2 fixation with single and mixed sources of NO3 and NH4

Summary Non-nodulatedalnus glutinosa plants were grown for 6 weeks in nutrient solutions using 3 combined-N treatments (NO₃; NO₃/NH₄; and NH₄) at a total N level of 4 meq.l^–1, and growth was ccmpared with nodulated plants at zero N (N₂ fixation). Of the combined-N sources, 100 per cent NH₄ resulted in the highest dry matter yields when the solution pH was adjusted daily atc. 6. The dry matter yield was lowest with NO₃.During the first 3 weeks, the yield of the N₂-fixing plants was as high as that of the NH₄ plants, but fell relatively behind during the second 3-week period. These effects could be attributed to higher initial N contents and higher shoot:root ratios, respectively, in the N₂-fixing plants. Specific rates of N acquisition in the root were of a comparable order of magnitude for the combined-N and zero-N treatments.When NO₃ was taken up, it was almost completely reduced in the roots. Regardless of N source there was a large excess of cations (C) relative to inorganic anions (A) in the plants, which was presumed to be balanced by an equivalent amount of organic anions (C-A). The relatively small differences in generation of organic anions for the various modes of N supply indicated the relative importance of the proton pump when NH₄ or N₂ was the N source. Proton or hydroxyl-ion effluxes, calculated on the basis of plant analyses, were generally in good agreement with measured excretion values. The acidity generation with N₂ fixation amounted toc. 0.5 meq H⁺.mmol^–1 N_org, which was distinctly higher than the range of 0.1–0.2 mentioned by Raven and Smith⁴³ for dinitrogen-fixing plants.Without pH adjustment, specific rates of cation uptake and carboxylate generation were strongly depressed as the acidity increased, when NO₃/NH₄, NH₄ and N₂ were the N sources. Growth ofAlnus glutinosa appeared to be still normal at a pH ofc. 2.8. During the final 3 weeks, only the NH₄ plants ceased growing at a pH of 2.6.     

Fullerene‐Based In Situ Doping of N and Fe into a 3D Cross‐Like Hierarchical Carbon Composite for High‐Performance Supercapacitors

Fullerene‐based carbons are promising electrode materials for supercapacitors due to their unique carbon structures and tunable architectures at the molecular level. By introducing various functional groups with many elements on the fullerene cages, diverse in situ metal/nonmetal‐doped carbon materials with enhanced pseudocapacitances and/or double layer capacitances can be prepared. In the present work, a fullerene derivative, ferrocenylpyrrolidine C₆₀, containing nitrogen and iron, is chosen as the only precursor. A unique microstructure is fabricated by a liquid–liquid interfacial precipitation process. Subsequently, a facile, one‐step annealing of the microstructure at different temperatures is performed. A series of in situ N and Fe‐codoped laminated 3D hierarchical carbon composites in the shape of a cross are successfully synthesized. The as‐prepared N and Fe‐codoped carbon material treated at 700 °C exhibits a high specific capacitance of 505.4 F g^?1 at 0.1 A g^?1. To the best knowledge, this is the highest supercapacitor capacitance based on fullerene electrode materials. The use of a fullerene derivative as an in‐situ doped carbon for applications in energy storage opens a new avenue for developing future synthetic strategies to extend the repertoire of electrode materials with high performance.     

Studies on activities, cell up take and DNA binding of four multinuclear complexes of the form: [[trans-PtCl(NH(3))(2)](2)mu-[trans-Pd(NH(3))(2)-(H(2)N(CH(2))(n)NH(2))(2)]]Cl(4) where n=4-7

The activity against human cancer cell lines including ovarian: A2780, A2780(cisR), cell up take, DNA-binding and nature of interaction with pBR322 plasmid DNA have been studied for four multinuclear complexes code named DH4Cl, DH5Cl, DH6Cl and DH7Cl, having the general formula: [[trans-PtCl(NH(3))(2)](2)mu-[trans-Pd(NH(3))(2)-(H(2)N(CH(2))(n)NH(2))(2)]]Cl(4) where n=4, 5, 6 and 7 for DH4Cl, DH5Cl, DH6Cl and DH7Cl, respectively. The compounds are found to exhibit significant anticancer activity against ovarian cancer cell lines: A2780, A2780(cisR) and A2780(ZD0473R). DH6Cl in which the linking diamine has six carbon atoms is found to be the most active compound. As the number of carbon atoms in the linking diamine is decreased below six and increased above six, the activity is found to decrease, illustrating structure-activity relationship. All the multinuclear compounds are believed to form a plethora of long-range interstrand GG adducts with DNA dictated by the sequence of bases in the DNA strands. Increasing prevention of BamH1 digestion with the increase in concentration of the compounds is due to global changes in DNA conformation brought about by interstrand long-range binding of the compounds with DNA.     

SARS-CoV-2 in patients with cancer: possible role of mimicry of human molecules by viral proteins and the resulting anti-cancer immunity

A few reports suggest that molecular mimicry can have a role in determining the more severe and deadly forms of COVID-19, inducing endothelial damage, disseminated intravascular coagulation, and multiorgan failure. Heat shock proteins/molecular chaperones can be involved in these molecular mimicry phenomena. However, tumor cells can display on their surface heat shock proteins/molecular chaperones that are mimicked by SARS-CoV-2 molecules (including the Spike protein), similarly to what happens in other bacterial or viral infections. Since molecular mimicry between SARS-CoV-2 and tumoral proteins can elicit an immune reaction in which antibodies or cytotoxic cells produced against the virus cross-react with the tumor cells, we want to prompt clinical studies to evaluate the impact of SARS-CoV-2 infection on prognosis and follow up of various forms of tumors. These topics, including a brief historical overview, are discussed in this paper.     

Biochar application as a tool to decrease soil nitrogen losses (NH3 volatilization,N2O emissions,and N leaching) from croplands: Options and mitigation strength in a global perspective

Biochar application to croplands has been proposed as a potential strategy to decrease losses of soil‐reactive nitrogen (N) to the air and water. However, the extent and spatial variability of biochar function at the global level are still unclear. Using Random Forest regression modelling of machine learning based on data compiled from the literature, we mapped the impacts of different biochar types (derived from wood, straw, or manure), and their interactions with biochar application rates, soil properties, and environmental factors, on soil N losses (NH₃ volatilization, N₂O emissions, and N leaching) and crop productivity. The results show that a suitable distribution of biochar across global croplands (i.e., one application of <40 t ha^?1 wood biochar for poorly buffered soils, such as those characterized by soil pH<5, organic carbon<1%, or clay>30%; and one application of <80 t ha^?1 wood biochar, <40 t ha^?1 straw biochar, or <10 t ha^?1 manure biochar for other soils) could achieve an increase in global crop yields by 222–766 Tg yr^?1 (4%–16% increase), a mitigation of cropland N₂O emissions by 0.19–0.88 Tg N yr^?1 (6%–30% decrease), a decline of cropland N leaching by 3.9–9.2 Tg N yr^?1 (12%–29% decrease), but also a fluctuation of cropland NH₃ volatilization by ?1.9–4.7 Tg N yr^?1 (?12%–31% change). The decreased sum of the three major reactive N losses amount to 1.7–9.4 Tg N yr^?1, which corresponds to 3%–14% of the global cropland total N loss. Biochar generally has a larger potential for decreasing soil N losses but with less benefits to crop production in temperate regions than in tropical regions.     

Modeling the C Economy of Anabaena flos-aquae: Estimates of Establishment, Maintenance, and Active Costs Associated with Growth on NH(3), NO(3), and N(2)

Steady state cultures of Anabaena flos-aquae were established over a wide range of phosphate-limited growth rates while N was supplied as either NH₃, NO₃⁻, or N₂ gas. At growth rates greater than 0.03 per hour, rates of gross and net carbon fixation were similar on all N sources. However, at lower growth rates (<0.03 per hour) in the NO₃⁻ and N₂ cultures, gross photosynthesis greatly exceeded net photosynthesis. The increase in photosynthetic O₂ evolution with growth rate was greatest when N requirements were met by NO₃⁻ and least when met by NH₃. These results were combined with previously reported measurements of cellular chemical composition, N assimilation, and acetylene reduction (Layzell, Turpin, Elrifi 1985 Plant Physiol 78: 739-745) to construct empirical models of carbon and energy flow for cultures grown at 30, 60, and 100% of their maximal growth rate on all N sources. The models suggested that over this growth range, 89 to 100% of photodriven electrons were allocated to biomass production in the NH₃ cells, whereas only 49 to 74% and 54 to 90% were partitioned to biomass in the NO₃⁻-and N₂-grown cells, respectively. The models were used to estimate the relative contribution of active, maintenance, and establishment costs associated with NO₃⁻ and N₂ assimilation over the entire range of growth rates. The models showed that the relative contribution of the component costs of N assimilation were growth rate dependent. At higher growth rates, the major costs for NO₃⁻ assimilation were the active costs, while in N₂-fixing cultures the major energetic requirements were those associated with heterocyst establishment and maintenance. It was concluded that compared with NO₃⁻ assimilation, N₂ fixation was energetically unfavorable due to the costs of heterocyst establishment and maintenance, rather than the active costs of N₂ assimilation.