Computational synthesis of hydrogenated fullerenes from C<Subscript>60</Subscript> to C<Subscript>60</Subscript>H<Subscript>60</Subscript>

Hydrogenation from C₆₀ to C₆₀H₆₀ was studied by an unrestricted broken spin symmetry Hartree–Fock approach implemented in semiempirical codes based on the AM1 technique. The calculations focused on the successive addition of hydrogen molecules to the fullerene cage following the identification of the cage target atoms by calculating the highest atomic chemical susceptibility at each step. The results obtained are analyzed from energy, symmetry, and composition perspectives.     

Physical,chemical, and regulatory properties of glycolate oxidase in C<Subscript>3</Subscript> and C<Subscript>4</Subscript> plants

Physical, chemical, and regulatory properties of glycolate oxidase (GO) isolated from the leaves of C₄ and C₃ plants (Zea mays L., cv. Voronezhskaya 76 and Glycine max (L.) Merr., cv. Pripyat’, respectively) were studied. The homogenous preparations were obtained by multistage enzyme purification from soybean leaves and maize mesophyll and bundle sheath. The glycolate oxidase (GO) preparations obtained consisted of two types of subunits, 37 and 44 kD. The GO isolated from C₃ plant leaves had many in common with that extracted from C₄ plant bundle sheath as regards physical, chemical, and catalytic properties. The primary function of GO in both plant types is metabolism of glycolate, which is a product of ribulosebisphosphate oxalacetic acid oxidation and is used by plants for biosynthesis of hydrocarbons and amino acids.     

C<Subscript>3</Subscript> and C<Subscript>4</Subscript> photosynthetic pathways and life form types for native species from agro-forestry region,Northeastern China

Of the total 570 species, 194 species in 116 genera and 52 families were found with C₃ photosynthesis, 24 species in 17 genera and 6 families with C₄ photosynthesis, and 2 species in 1 genera and 1 family with CAM photosynthesis. 90 % of the total species can be found in Changbai Mountain flora, more a half (69 %) in North China flora, and about 1/3 in Mongolian flora and Xinan flora, respectively. The occurrence of C₄ species was not as common as that in adjacent grasslands and deserts, but relatively more than in the adjacent forests. Of the total 24 C₄ species, 63 % C₄ species (15 of 24) was found in Gramineae. Nine life form types can be found, reflecting the moist climate in the region, especially the occurrence of epiphyte and liana forms. Relatively more geophyte life form plants suggested the winter in the region was much colder than in grasslands. These indicated that both ecological studies and land management decisions must take into account plant photosynthetic pathway and life form patterns, for both of them are closely related to climatic changes and land use.     

Modeling zigzag CNT: dependence of structural and electronic properties on length,and application to encapsulation of HCN and C<Subscript>2</Subscript>H<Subscript>2</Subscript>

Density functional theory (B3LYP, B3LYP-D2 and wB97XD functionals) was used in finite models of zigzag carbon nanotubes (CNT), (n,0)×k with n?=?6–9 and k?=?2–4, to systematically investigate the effects of size on their structural and electronic properties. We found that the ratio between the length (L _t) and the diameter (d _t) of the pristine CNT has to be larger than 2, i.e., L _t/d _t?>?2, in order to provide the observed experimental trends of C=C bond distances, as well as to maintain the atomic charges nearly constant and zero around the center of the tube. Therefore, the concepts of useful length and volume were developed and tested for the encapsulation process of HCN and C₂H₂ into CNTs. The energies involved in these processes, as well as the changes in molecular structure and electronic properties of the dopants and the CNTs are discussed and rationalized by the amount of charge transferred between dopant and CNT.

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Graphical Abstract Illustration of zigzag CNT length and diameter ratio in order to represent C=C bond experimental trend

     

H<Subscript>2</Subscript>-Producing bacterial communities from a heat-treated soil inoculum

Hydrogen gas (60% H₂) was produced in a continuous flow bioreactor inoculated with heat-treated soil, and fed synthetic wastewater containing glucose (9.5 g l^–1). The pH in the bioreactor was maintained at 5.5 to inhibit consumption of H₂ by methanogens. The objective of this study was to characterize bacterial communities in the reactor operated under two different hydraulic retention times (HRTs of 30-h and 10-h) and temperatures (30°C and 37°C). At 30-h HRT, the H₂ production rate was 80 ml h^–1 and yield was 0.91 mol H₂/mol glucose. At 10-h HRT, the H₂ production rate was more than 5 times higher at 436 ml h^–1, and yield was 1.61 mol H₂/mol glucose. Samples were removed from the reactor under steady-state conditions for PCR-based detection of bacterial populations by ribosomal intergenic spacer analysis (RISA). Populations detected at 30-h HRT were more diverse than at 10-h HRT and included representatives of Bacillaceae, Clostridiaceae, and Enterobacteriaceae. At 10-h HRT, only Clostridiaceae were detected. When the temperature of the 10-h HRT reactor was increased from 30°C to 37°C, the steady-state H₂ production rate increased slightly to 463 ml h^–1 and yield was 1.8 mol H₂/mol glucose. Compared to 30°C, RISA fingerprints at 37°C from the 10-h HRT bioreactor exhibited a clear shift from populations related to Clostridium acidisoli (subcluster Ic) to populations related to Clostridium acetobutylicum (subcluster Ib).     

The polythiophene molecular segment as a sensor model for H<Subscript>2</Subscript>O,HCN, NH<Subscript>3</Subscript>, SO<Subscript>3</Subscript>, and H<Subscript>2</Subscript>S: a density functional theory study

Studying the interaction of some atmospheric gases (H₂O, HCN, NH₃, SO₃ and H₂S) with 3PT oligomers is important in the development of polymeric sensors for gas detection. In the present study, we studied the relaxed geometries, interaction energies, charge analysis, HOMO–LUMO orbital analysis, and UV–vis spectra of all interacted systems using first-principles density functional theory (DFT). All these analyses indicated the potential of polythiophene as an inexpensive polymeric sensor for the analytes mentioned. Interaction energy values of ?19.90, ?19.66, ?14.01, ?8.70, and ?4.76 kJ mol^?1 were achieved for adsorption of SO₃, H₂O, NH₃, HCN, and H₂S on 3PT, respectively. Consequently, clarification of their physical parameters became the major focus of this study.     

Putrescine protects hulless barley from damage due to UV-B stress via H<Subscript>2</Subscript>S- and H<Subscript>2</Subscript>O<Subscript>2</Subscript>-mediated signaling pathways

Key message

In hulless barley, H ₂ S mediated increases in H ₂ O ₂ induced by putrescine, and their interaction enhanced tolerance to UV-B by maintaining redox homeostasis and promoting the accumulation of UV-absorbing compounds.

Abstract

This study investigated the possible relationship between putrescence (Put), hydrogen sulfide (H₂S) and hydrogen peroxide (H₂O₂) as well as the underlying mechanism of their interaction in reducing UV-B induced damage. UV-B radiation increased electrolyte leakage (EL) and the levels of malondialdehyde (MDA) and UV-absorbing compounds but reduced antioxidant enzyme activities and glutathione (GSH) and ascorbic acid (AsA) contents. Exogenous application of Put, H₂S or H₂O₂ reduced some of the above-mentioned negative effects, but were enhanced by the addition of Put, H₂S and H₂O₂ inhibitors. Moreover, the protective effect of Put against UV-B radiation-induced damage to hulless barley was diminished by dl-propargylglycine (PAG, a H₂S biosynthesis inhibitor), hydroxylamine (HT, a H₂S scavenger), diphenylene iodonium (DPI, a PM-NADPH oxidase inhibitor) and dimethylthiourea (DMTU, a ROS scavenger), and the effect of Put on H₂O₂ accumulation was abolished by HT. Taken together, as the downstream component of the Put signaling pathway, H₂S mediated H₂O₂ accumulation, and H₂O₂ induced the accumulation of UV-absorbing compounds and maintained redox homeostasis under UV-B stress, thereby increasing the tolerance of hulless barley seedlings to UV-B stress.

     

Fumonisin B<Subscript>1</Subscript>, a sphingoid toxin,is a potent inhibitor of the plasma membrane H<Superscript>+</Superscript>-ATPase

Fumonisin B₁ (FB₁) is an amphipathic toxin produced by the pathogenic fungus Fusarium verticillioides which causes stem, root and ear rot in maize (Zea mays L.). In this work, we studied the action of FB₁ on the plasma membrane H⁺-ATPase (EC 3.6.1.34) from germinating maize embryos, and on the fluidity and lipid peroxidation of these membranes. In maize embryos the toxin at 40 M inhibited root elongation by 50% and at 30 M decreased medium acidification by about 80%. Irrespective of the presence and absence of FB₁, the H⁺-ATPase in plasma membrane vesicles exhibited non-hyperbolic saturation kinetics by ATPH-Mg, with Hill number of 0.67. Initial velocity studies revealed that FB₁ is a total uncompetitive inhibitor of this enzyme with an inhibition constant value of 17.5±1 M. Thus FB₁ decreased V_max and increased the apparent affinity of the enzyme for ATP-Mg to the same extent. Although FB₁ increased the fluidity at the hydrophobic region of the membrane, no correlation was found with its effect on enzyme activity, since both effects showed different FB₁-concentration dependence. Peroxidation of membrane lipids was not affected by the toxin. Our results suggest that, under in vivo conditions, the plasma membrane H⁺-ATPase is a potentially important target of the toxin, as it is inhibited not only by FB₁ but also by its structural analogs, the sphingoid intermediates, which accumulate upon the inhibition of sphinganine N-acyltransferase by this toxin.     

Performance of a generalist grasshopper on a C<Subscript>3</Subscript> and a C<Subscript>4</Subscript> grass: compensation for the effects of elevated CO<Subscript>2</Subscript> on plant nutritional quality

The increasing CO₂ concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C₃ than C₄ plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C₃ plants. These hypotheses were tested by growing the grasses Lolium multiflorum C₃) and Bouteloua curtipendula C₄) at ambient (370 ppm) and elevated (740 ppm) CO₂ levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO₂ treatment combinations. As expected, the nutritional quality of the C₃ grass declined to a greater extent than did that of the C₄ grass at elevated CO₂; protein levels declined in the C₃ grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C₃ grass grown under elevated CO₂. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C₃ grass under elevated CO₂. Consumption rates of the C₃ and C₄ grasses were also similar, demonstrating a lack of compensatory feeding on the C₄ grass. We also examined the relative efficiencies of nutrient utilization from a C₃ and C₄ grass by M. sanguinipes to test the basis for the C₄ plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C₄ grass than from the C₃ grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C₃ grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C₃ grass and the better growth performance of M. sanguinipes on this grass at both CO₂ levels, we conclude that C₃ grasses are likely to remain better host plants than C₄ grasses in future CO₂ conditions.     

C<Subscript>1</Subscript>-/C<Subscript>2</Subscript>-aromatic-imino-glyco-conjugates: experimental and computational studies of binding,inhibition and docking aspects towards glycosidases isolated from soybean and jack bean

Several C₁-imino conjugates of d-galactose, d-lactose and d-ribose, where the nitrogen center was substituted by the salicylidene or naphthylidene, were synthesized and characterized. Similar C₂-imino conjugates of d-glucose have also been synthesized. All the glyco-imino-conjugates, which are transition state analogues, exhibited 100% inhibition of the activity towards glycosidases extracted from soybean and jack bean meal. Among these, a galactosyl-napthyl-imine-conjugate (1c) showed 50% inhibition of the activity of pure α-mannosidase from jack bean at 22 ± 2.5 μM, and a ribosyl-naphthyl-imine-conjugate (3c) showed at 31 ± 5.5 μM and hence these conjugates are potent inhibitors of glycosidases. The kinetic studies suggested non-competitive inhibition by these conjugates. The studies are also suggestive of the involvement of aromatic, imine and carbohydrate moieties of the glyco-imino-conjugates in the effective inhibition. The binding of glyco-imino-conjugate has been established by extensive studies carried out using fluorescence emission and isothermal titration calorimetry. The conformational changes resulted in the enzyme upon interaction of these derivatives has been established by studying the fluorescence quench of the enzyme by KI as well as from the secondary structural changes noticed in CD spectra. All these studies revealed the difference in the binding strengths of the naphthylidene vs. salicylidene as well as galactosyl vs. lactosyl moieties present in these conjugates. The differential inhibition of these glyco-conjugates has been addressed by quantifying the specific interactions present between the glyco-conjugates and the enzyme by using rigid docking studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of exogenous H<Subscript>2</Subscript>O<Subscript>2</Subscript> on the content of endogenous H<Subscript>2</Subscript>O<Subscript>2</Subscript>, activities of catalase and hydrolases,and cell ultrastructure in tobacco leaves

It was shown that tobacco leaf treatment with 100 mM H₂O₂ increased their content of endogenous H₂O₂ and activities of catalase and hydrolases (acid phosphatase, proteases, and RNase) and also caused various changes in the cell structure. In this case, programmed cell death (PCD) occurred in some cells, which was observed as chromatin condensation, cytoplasm collapse, etc. In the meantime, many cells displayed organelle activation rather than PCD. It is suggested that cells that undergo H₂O₂-dependent PCD release signaling molecules inducing protective mechanisms against oxidative stress in neighboring cells not exhibiting PCD.     

The interactive effects of elevated CO<Subscript>2</Subscript>, temperature and initial size on growth and competition between a native C<Subscript>3</Subscript> and an invasive C<Subscript>3</Subscript> grass

A controlled environment experiment was conducted to determine the impact of enhanced carbon dioxide and temperature on competition between the C₃ grasses Austrodanthonia eriantha and Vulpia myuros. Plants were grown in mixtures and monocultures to compare the responses both with and without an interspecific competitor. Temperature and CO₂ were set at current levels (350 ppm CO₂; 20 °C day and 10 °C night temperature), in factorial combination with enhanced levels (700 ppm CO₂; 23 °C day and 13 °C night temperature). To examine the potential impact of initial seedling size on competition under elevated CO₂ and temperature, the two species were combined in mixtures of differing initial sizes. Above-ground growth of all plants was enhanced by increased CO₂ and temperature alone, however the combined temperature and CO₂ treatment showed a sub-additive effect, where growth was less than expected based on the responses to each factor independently. Austrodanthonia in mixture with Vulpia plants of the same initial size experienced a 27 reduction in growth. Austrodanthonia grown in the presence of an initially larger Vulpia plant experienced a 58 reduction in growth. When the Vulpia plant was initially smaller than Austrodanthonia, growth of the Austrodanthonia was reduced by 16%. The growth of Vulpia appeared to be largely unaffected by the presence of Austrodanthonia. Variation in the CO₂ and temperature environment did not affect the pattern of these interspecific interactions, although there was some evidence to suggest that the degree of suppression of Austrodanthonia by Vulpia was less under elevated CO₂. These results do not support the initial advantage hypothesis, as Vulpia was always able to suppress Austrodanthonia, regardless of the initial relative sizes of the competitors. Furthermore, the lack of an effect of changing the CO₂ or temperature environment on the direction of interspecific competition suggests that the competitiveness of the invasive Vulpia will be minimally affected by changes in atmospheric CO₂ concentration or temperature.     

The contribution of C<Subscript>3</Subscript> and C<Subscript>4</Subscript> plants to the carbon cycle of a tallgrass prairie: an isotopic approach

The photosynthetic pathway composition (C₃:C₄ mixture) of an ecosystem is an important controller of carbon exchanges and surface energy flux partitioning, and therefore represents a fundamental ecophysiological distinction. To assess photosynthetic mixtures at a tallgrass prairie pasture in Oklahoma, we collected nighttime above-canopy air samples along concentration and isotopic gradients throughout the 1999 and 2000 growing seasons. We analyzed these samples for their CO₂ concentration and carbon isotopic composition and calculated C₃:C₄ proportions with a two-source mixing model. In 1999, the C₄ percentage increased from 38% in spring (late April) to 86% in early fall (mid-September). The C₄ percentages inferred from ecosystem respiration measurements in 2000 indicate a smaller shift, from 67% in spring (early May) to 77% in mid-summer (late July). We also sampled daytime CO₂ concentration and carbon isotope gradients above the canopy to determine ecosystem discrimination against ¹³CO₂ during net uptake. These discrimination values were always lower than corresponding nighttime ecosystem respiration isotopic signatures would suggest. After accounting for the isotopic disequilibria between respiration and photosynthesis resulting from seasonal variations in the C₃:C₄ mixture, we estimated canopy photosynthetic discrimination. The C₄ percentage calculated from this approach agrees with the percentage determined from nighttime respiration for sampling periods in both growing seasons. Isotopic imbalances between photosynthesis and respiration are likely to be common in mixed C₃:C₄ ecosystems and must be considered when using daytime isotopic measurements to constrain ecosystem physiology. Given the global extent of such ecosystems, isotopic imbalances likely contribute to global variations in the carbon isotopic composition of atmospheric CO₂.     

A DFT study of addition reaction between fragment ion (CH<Subscript>2</Subscript>) units and fullerene (C<Subscript>60</Subscript>) molecule

The theoretical study of the interaction between CH₂ and fullerene (C₆₀) suggests the existence of an addition reaction mechanism; this feature is studied by applying an analysis of electronic properties. Several different effects are evident in this interaction as a consequence of the particular electronic transfer which occurs during the procedure. The addition or insertion of the methylene group results in a process, where the inclusion of CH₂ into a fullerene bond produces the formation of several geometric deformations. A simulation of these procedures was carried out, taking advantage of the dynamic semi-classical Born-Oppenheimer approximation. Dynamic aspects were analyzed at different speeds, for the interaction between the CH₂ group and the two bonds: CC (6, 6) and CC (6, 5) respectively on the fullerene (C₆₀) rings. All calculations which involved electrons employed DFT as well as exchange and functional correlation. The results indicate a tendency for the CH₂ fragment to attack the CC (6, 5) bond.     

Fullerenes C<Subscript>60</Subscript>, antiamyloid action,the brain,and cognitive processes

A short review of investigations along a new line: the antiamyloid action of fullerenes C₆₀ and correction of disturbed cognitive processes is presented. The prospects for the development of drugs based on fullerenes acting on the key molecular mechanisms at the early stage of Alzheimer’s disease are discussed.     

Simulation and optical spectroscopy of a DC discharge in a CH<Subscript>4</Subscript>/H<Subscript>2</Subscript>/N<Subscript>2</Subscript> mixture during deposition of nanostructured carbon films

Two-dimensional numerical simulations of a dc discharge in a CH₄/H₂/N₂ mixture in the regime of deposition of nanostructured carbon films are carried out with account of the cathode electron beam effects. The distributions of the gas temperature and species number densities are calculated, and the main plasmachemical kinetic processes governing the distribution of methyl radicals above the substrate are analyzed. It is shown that the number density of methyl radicals above the substrate is several orders of magnitude higher than the number densities of other hydrocarbon radicals, which indicates that the former play a dominant role in the growth of nanostructured carbon films. The model is verified by comparing the measured optical emission profiles of the H(n ≡ 3), C ₂ ^* , CH*, and CN* species and the calculated number densities of excited species, as well as the measured and calculated values of the discharge voltage and heat fluxes onto the electrodes and reactor walls. The key role of ion–electron recombination and dissociative excitation of H₂, C₂H₂, CH₄, and HCN molecules in the generation of emitting species (first of all, in the cold regions adjacent to the electrodes) is revealed.     

Transient-state biodegradation behavior of a horizontal biotrickling filter in co-treating gaseous H<Subscript>2</Subscript>S and NH<Subscript>3</Subscript>

A horizontal biotrickling filter (HBTF) was used to inoculate autotrophic sulfide-oxidizing and ammonia-oxidizing microbial consortiums over H₂S-exhausted carbon for co-treating H₂S and NH₃ waste gas in a long-term operation. In this study, several aspects (i.e., pH change, shock loading and starvation) of the dynamic behavior of the HBTF were investigated. The metabolic products of N and S bearing species in recycling liquid and biological activities of the biofilm were analyzed to explain the observed phenomena and further explore the fundamentals behind. In the pH range of 4–8.5, although the removal efficiencies of H₂S and NH₃ remained 96–98% and 100%, respectively, the metabolic products demonstrated different removal mechanisms and pathways. NH₄-N and NO₂/NO₃-N were dominated at pH ≤6 and ≥7, respectively, indicating the differentiated contributions from physical/chemical adsorption and bio-oxidation. Moreover, the HBTF demonstrated a good dynamic stability to withstand shock loadings by recovering immediately to the original. During shock loading, only 15.4% and 17.9% of captured H₂S and NH₃ was biodegraded, respectively. After 2, 11, and 48 days of starvation, the HBTF system reached a full performance within reasonable re-startup times (2–80 h), possibly due to the consumption of reduced S and N species in biomass or activated carbon thus converted into SO₄-S and NO₃-N during starvation period. The results helped to understand the fundamental knowledge by revealing the effects of pH and transient loadings linked with individual removal mechanism for H₂S and NH₃ co-treatment in different conditions.