Synthesis of Protein-Inorganic Nanohybrids with Improved Catalytic Properties Using Co<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

In the present study, a method for easy and rapid synthesis of lipase nanohybrids was evaluated using cobalt chloride as an encapsulating agent. The synthesized nanohybrids exhibited higher activity (181%) compared to free lipase and improved catalytic properties at higher temperature and in harsh conditions. The nanohybrids retained 84% of their residual activity at 25 °C after 10 days. In addition, these nanohybrids also exhibited high storage stability and reusability. Collectively, the synthesis of carrier-free immobilized biocatalysts was performed rapidly within 24 h at 4 °C. Their high reusability and catalytic activities highlight the broad applicability of this method for catalysis in organic and aqueous media.     

Immobilization of glucose oxidase on Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> magnetic nanoparticles

Glucose oxidase (GOD) was covalently immobilized onto Fe₃O₄/SiO₂ magnetic nanoparticles (FSMNs) using glutaraldehyde (GA). Optimal immobilization was at pH 6 with 3-aminopropyltriethoxysilane at 2% (v/v), GA at 3% (v/v) and 0.143 g GOD per g carrier. The activity of immobilized GOD was 4,570 U/g at pH 7 and 50°C. The immobilized GOD retained 80% of its initial activity after 6 h at 45°C while free enzyme retained only 20% activity. The immobilized GOD maintained 60% of its initial activity after 6 cycles of repeated use and retained 75% of its initial activity after 1 month at 4°C whereas free enzymes retained 62% of its activity.     

Bonding,aromaticity, and planar tetracoordinated carbon in Si<Subscript>2</Subscript>CH<Subscript>2</Subscript> and Ge<Subscript>2</Subscript>CH<Subscript>2</Subscript>

Natural bond orbital (NBO) analyses and dissected nucleus-independent chemical shifts (NICS _{π z z} ) were computed to evaluate the bonding (bond type, electron occupation, hybridization) and aromatic character of the three lowest-lying Si₂CH₂ (1-Si, 2-Si, 3-Si) and Ge₂CH₂ (1-Ge, 2-Ge, 3-Ge) isomers. While their carbon C₃H₂ analogs favor classical alkene, allene, and alkyne type bonding, these Si and Ge derivatives are more polarizable and can favor “highly electron delocalized”? and “non-classical”? structures. The lowest energy Si ₂CH₂ and Ge ₂CH₂ isomers, 1-Si and 1-Ge, exhibit two sets of 3–center 2–electron (3c-2e) bonding; a π-3c-2e bond involving the heavy atoms (C–Si–Si and C–Ge–Ge), and a σ-3c-2e bond (Si–H–Si, Ge–H–Ge). Both 3-Si and 3-Ge exhibit π and σ-3c-2e bonding involving a planar tetracoordinated carbon (ptC) center. Despite their highly electron delocalized nature, all of the Si₂CH₂ and Ge₂CH₂ isomers considered display only modest two π electron aromatic character (NICS(0) _{π z z} =--6.2 to –8.9 ppm, computed at the heavy atom ring center) compared to the cyclic-C ₃H₂ (–13.3 ppm).

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Graphical Abstract The three lowest Si2CH2 and Ge2CH2 isomers.

     

The subcommissural organ expresses D<Subscript>2</Subscript>, D<Subscript>3</Subscript>, D<Subscript>4</Subscript>, and D<Subscript>5</Subscript> dopamine receptors

Dopamine receptors have been found in certain populations of non-neuronal cells in the brain, viz., discrete areas of ciliated ependyma and the ependymal cells of the choroid plexus. We have studied the presence of both tyrosine-hydroxylase-immunoreactive nerve fibers and dopamine receptors in the subcommissural organ (SCO), an ependymal brain gland that is located in the roof of the third ventricle and that secretes, into the cerebrospinal fluid, glycoproteins that aggregate to form Reissners fiber (RF). Antibodies against D₂, D₃, D₄, and D₅ dopamine receptors were used in immunoblots of bovine striatum, fresh SCO, and organ-cultured SCO, and in immunocytochemistry of the bovine, rat, and mouse SCO. Only a few tyrosine-hydroxylase fibers appeared to reach the SCO. However, virtually all the secretory ependymal and hypendymal cells of the SCO immunoreacted with antibodies against D₂, D₄, and D₅ receptors, with the last-mentioned rendering the strongest reaction, especially at the ventricular cell pole of the secretory ependymocytes, suggesting that dopamine might reach the SCO via the cerebrospinal fluid. The antibodies against the four subtypes of receptors revealed corresponding bands in immunoblots of striatum and fresh SCO. Although the cultured SCO displayed dopamine receptors, dopamine had no apparent effect on the expression of the SCO-spondin gene/protein or on the release of RF-glycoproteins (SCO-spondin included) by SCO explants, suggesting that dopamine affects the function(s) of the SCO differently from the secretion of RF-glycoproteins.Financial support was provided by grants PI 030756 and Red CIEN, Instituto de Salud Carlos III, Spain (to J.M.P.F.), and 1030265 from Fondecyt, Chile (to E.M.R.)     

Emissions of CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O from undisturbed,drained and mined peatlands in Estonia

The aim of this study is to estimate emissions of greenhouse gases CO₂, CH₄ and N₂O, and the effects of drainage and peat extraction on these processes, in Estonian transitional fens and ombrotrophic bogs. Closed-chamber-based sampling lasted from January to December 2009 in nine peatlands in Estonia, covering areas with different land-use practices: natural (four study sites), drained (six sites), abandoned peat mining (five sites) and active peat mining areas (five sites). Median values of soil CO₂ efflux were 1,509, 1,921, 2,845 and 1,741 kg CO₂-C ha^?1 year^?1 from natural, drained, abandoned and active mining areas, respectively. Emission of CH₄-C (median values) was 85.2, 23.7, 0.07 and 0.12 kg ha^?1 year^?1, and N₂O-N ?0.05, ?0.01, 0.18 and 0.19 kg ha^?1 year^?1, respectively. There were significantly higher emissions of CO₂ and N₂O from abandoned and active peat mining areas, whereas CH₄ emissions were significantly higher in natural and drained areas. Significant Spearman rank correlation was found between soil temperature and CO₂ flux at all sites, and CH₄ flux with high water level at natural and drained areas. Significant increase in CH₄ flux was detected for groundwater levels above 30 cm.     

DFT study of isomers of the ruthenium dihydride complex RuH<Subscript>2</Subscript>(CO)<Subscript>2</Subscript>(AsMe<Subscript>2</Subscript>Ph)<Subscript>2</Subscript>

A density functional theory (DFT) study of cct-As, ccc, and cct-CO isomers of the ruthenium dihydride complex RuH₂(CO)₂(AsMe₂Ph)₂ is reported (see Scheme for the labeling isomer 34 structures of RuH₂(CO)₂(AsMe₂Ph)₂). Complex geometries and relative energies of different isomers have been calculated with both B3LYP and M06-2X functionals. The results show that the B3LYP calculated Boltzmann populations of cct-As, ccc, and cct-CO isomers are 65.5, 34.2, and 0.3%, respectively. These are in better agreement with the experimental data than those calculated at the M06-2X level. However, the calculations of ¹H NMR chemical shifts were found to be better described with M06-2X than with B3LYP or with HF level of theories. In addition, a transition state between the two most stable isomers was determined through DFT/(B3LYP or M06-2X) calculations.

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Graphical Abstract Scheme: Labeling structure of RuH₂(CO)₂(AsMe₂Ph)₂

     

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.     

Production of bioethanol from sugarcane bagasse using NH<Subscript>4</Subscript>OH-H<Subscript>2</Subscript>O<Subscript>2</Subscript> pretreatment and simultaneous saccharification and co-fermentation

In this study, we investigated the production of bioethanol from sugarcane bagasse (SCB) using an NH₄OH-H₂O₂ pretreatment and simultaneous saccharification and co-fermentation (SScF). Response surface methodology and a 2³ Box-Behnken design were used to evaluate the effect of different liquid mixture concentrations, liquid-to-solid ratios (LSRs) and pretreatment temperatures on the production of ethanol. The liquid mixture concentration and LSR significantly influenced the fermentation efficiency. Based on ridge max analysis, the following pretreatment conditions resulted in a fermentation efficiency of 95.79 ± 0.01%: liquid mixture concentration 53%, LSR 28, and a temperature of 63°C. A morphological analysis performed using scanning electron microscopy (SEM) and chemical characterization revealed that these pretreatment conditions were effective in disrupting the sugarcane fibers and removing lignin. Ethanol fermentation with the pretreated SCB using SScF in yeast SHY 07-1 resulted in an ethanol concentration of 14.65 ± 0.17 g/L, an ethanol yield of 0.48 ± 0.01 g/g, and an ethanol productivity of 0.12 ± 0.01 g/(L/h), which represents increases of 106.02, 89.98, and 107.02%, respectively, over the values obtained from SScF with untreated SCB.     

Prostaglandin E<Subscript>2</Subscript> (PGE<Subscript>2</Subscript>) suppresses natural killer cell function primarily through the PGE<Subscript>2</Subscript> receptor EP4

The COX-2 product prostaglandin E₂ (PGE₂) contributes to the high metastatic capacity of breast tumors. Our published data indicate that inhibiting either PGE₂ production or PGE₂-mediated signaling through the PGE₂ receptor EP4 reduces metastasis by a mechanism that requires natural killer (NK) cells. It is known that NK cell function is compromised by PGE₂, but very little is known about the mechanism by which PGE₂ affects NK effector activity. We now report the direct effects of PGE₂ on the NK cell. Endogenous murine splenic NK cells express all four PGE₂ receptors (EP1-4). We examined the role of EP receptors in three NK cell functions: migration, cytotoxicity, and cytokine release. Like PGE₂, the EP4 agonist PGE₁-OH blocked NK cell migration to FBS and to four chemokines (ITAC, MIP-1α, SDF-1α, and CCL21). The EP2 agonist, Butaprost, inhibited migration to specific chemokines but not in response to FBS. In contrast to the inhibitory actions of PGE₂, the EP1/EP3 agonist Sulprostone increased migration. Unlike the opposing effects of EP4 vs. EP1/EP3 on migration, agonists of each EP receptor were uniformly inhibiting to NK-mediated cytotoxicity. The EP4 agonist, PGE₁-OH, inhibited IFNγ production from NK cells. Agonists for EP1, EP2, and EP3 were not as effective at inhibiting IFNγ. Agonists of EP1, EP2, and EP4 all inhibited TNFα; EP4 agonists were the most potent. Thus, the EP4 receptor consistently contributed to loss of function. These results, taken together, support a mechanism whereby inhibiting PGE₂ production or preventing signaling through the EP4 receptor may prevent suppression of NK functions that are critical to the control of breast cancer metastasis.     

Hydrothermal Stability of Adenine Under Controlled Fugacities of N<Subscript>2</Subscript>, CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>

An experimental study has been carried out on the stability of adenine (one of the five nucleic acid bases) under hydrothermal conditions. The experiments were performed in sealed autoclaves at 300 degrees C under fugacities of CO(2), N(2) and H(2) supposedly representative of those in marine hydrothermal systems on the early Earth. The composition of the gas phase was obtained from the degradation of oxalic acid, sodium nitrite and ammonium chloride, and the oxidation of metallic iron. The results of the experiments indicate that after 200 h, adenine is still present in detectable concentration in the aqueous phase. In fact, the concentration of adenine does not seem to be decreasing after approximately 24 h, which suggests that an equilibrium state may have been established with the inorganic constituents of the hydrothermal fluid. Such a conclusion is corroborated by independent thermodynamic calculations.     

Effects of elevated atmospheric CO<Subscript>2</Subscript> on the nutritional ecology of C<Subscript>3</Subscript> and C<Subscript>4</Subscript> grass-feeding caterpillars

It is plausible that the nutritional quality of C₃ plants will decline more under elevated atmospheric CO₂ than will the nutritional quality of C₄ plants, causing herbivorous insects to increase their feeding on C₃ plants relative to C₄ plants. We tested this hypothesis with a C₃ and C₄ grass and two caterpillar species with different diet breadths. Lolium multiflorum (C₃) and Bouteloua curtipendula (C₄) were grown in outdoor open top chambers at ambient (370 ppm) or elevated (740 ppm) CO₂. Bioassays compared the performance and digestive efficiencies of Pseudaletia unipuncta (a grass-specialist noctuid) and Spodoptera frugiperda (a generalist noctuid). As expected, the nutritional quality of L. multiflorum changed to a greater extent than did that of B. curtipendula when grown in elevated CO₂; levels of protein (considered growth limiting) declined in the C₃ grass, while levels of carbohydrates (sugar, starch and fructan) increased. However, neither insect species increased its feeding rate on the C₃ grass to compensate for its lower nutritional quality when grown in an elevated CO₂ atmosphere. Consumption rates of P. unipuncta and S. frugiperda were higher on the C₃ grass than the C₄ grass, the opposite of the result expected for a compensatory response to the lower nutritional quality of the C₄ grass. Although our results do not support the hypothesis that grass-specialist insects compensate for lower nutritional quality by increasing their consumption rates more than do generalist insects, the performance of the specialist was greater than that of the generalist on each grass species and at both CO₂ levels. Mechanisms other than compensatory feeding, such as increased nutrient assimilation efficiency, appear to determine the relative performance of these herbivores. Our results also provide further evidence against the hypothesis that C₄ grasses would be avoided by insect herbivores because a large fraction of their nutrients is unavailable to herbivores. Instead, our results are consistent with the hypothesis that C₄ grasses are poorer host plants primarily because of their lower nutrient levels, higher fiber levels, and greater toughness.     

Effects of salinity on chlorophyll fluorescence and CO<Subscript>2</Subscript> fixation in C<Subscript>4</Subscript> estuarine grasses

The effects of salinity (sea water at 0 ‰ versus 30 ‰) on gross rates of O₂ evolution (J _O2) and net rates of CO₂ uptake (P _N) were measured in the halotolerant estuarine C₄ grasses Spartina patens, S. alterniflora, S. densiflora, and Distichlis spicata in controlled growth environments. Under high irradiance, salinity had no significant effect on the intercellular to ambient CO₂ concentration ratio (C _i/C _a). However, during photosynthesis under limiting irradiance, the maximum quantum efficiency of CO₂ fixation decreased under salinity across species, suggesting there is increased leakage of the CO₂ delivered to the bundle sheath cells by the C₄ pump. Growth under salinity did not affect the maximum intrinsic efficiency of photosystem 2, PS2 (F_V/F_M) in these species, suggesting salinity had no effect on photosynthesis by inactivation of PS2 reaction centers. Under saline conditions and high irradiance, P _N was reduced by 75 % in Spartina patens and S. alterniflora, whereas salinity had no effect on P _N in S. densiflora or D. spicata. This inhibition of P _N in S. patens and S. alterniflora was not due to an effect on stomatal conductance since the ratio of C _i/C _a did not decrease under saline conditions. In growth with and without salt, P _N was saturated at ∼500 μmol(quantum) m⁻² s⁻¹ while J _O2 continued to increase up to full sunlight, indicating that carbon assimilation was not tightly coupled to photochemistry in these halophytic species. This increase in alternative electron flow under high irradiance might be an inherent function in these halophytes for dissipating excess energy.     

Chromotoxic effects of exogenous hydrogen peroxide (H<Subscript>2</Subscript>O<Subscript>2</Subscript>) in barley seeds exposed to salt stress

The effect of exogenous hydrogen peroxide (H₂O₂) on mitotic activity and chromosomal aberrations in root tip meristems of barley (Hordeum vulgare L. var. Tokak 157/37) germinated under salinity was analyzed. The inhibitory effect of salinity on mitotic index and the frequency of chromosomal aberrations increased with increasing salt concentration (0.00 control, 0.35, 0.40, 0.45 M, molal NaCl). The frequency of chromosomal aberrations of seeds germinated in medium with 0.40 M NaCl after pretreatment with H₂O₂ (30 μM, micromolal) was significantly higher than the control group. The highest concentration of NaCl (0.45 M) together with H₂O₂ caused total inhibition of germination. In this study, the intention was to determine the performance of H₂O₂ in alleviating detrimental effect of salt stress on mitotic activity and chromosomal aberrations. However, H₂O₂ did not reduce the detrimental effect of NaCl on these parameters. Also, it caused higher chromotoxic effect compared to those of control groups.     

The encapsulated lithium effect on the first hyperpolarizability of C<Subscript>60</Subscript>Cl<Subscript>2</Subscript> and C<Subscript>60</Subscript>F<Subscript>2</Subscript>

In this paper, we report a study on the structure and first hyperpolarizability of C₆₀Cl₂ and C₆₀F₂. The calculation results show that the first hyperpolarizabilities of C₆₀Cl₂ and C₆₀F₂ were 172 au and 249 au, respectively. Compared with the fullerenes, the first hyperpolarizability of C₆₀Cl₂ increased from 0 au to 172 au, while the first hyperpolarizability of C₆₀F₂ increased from 0 au to 249 au. In order to further increase the first hyperpolarizability of C₆₀Cl₂ and C₆₀F₂, Li@C₆₀Cl₂ and Li@C₆₀F₂ were obtained by introducing a lithium atom to C₆₀Cl₂ and C₆₀F₂. The first hyperpolarizabilities of Li@C₆₀Cl₂ and Li@C₆₀F₂ were 2589 au and 985 au, representing a 15-fold and 3.9-fold increase, respectively, over those of C₆₀Cl₂ and C₆₀F₂. The transition energies of four molecules (C₆₀Cl₂, Li@C₆₀Cl₂, C₆₀F₂, Li@C₆₀F₂) were calculated, and were found to be 0.17866 au, 0.05229 au, 0.18385 au, and 0.05212 au, respectively. A two-level model explains why the first hyperpolarizability increases for Li@C₆₀Cl₂ and Li@C₆₀F₂.     

Spatial Variation of Soil CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O Fluxes Across Topographical Positions in Tropical Forests of the Guiana Shield

The spatial variation of soil greenhouse gas fluxes (GHG; carbon dioxide—CO₂, methane—CH₄ and nitrous oxide—N₂O) remains poorly understood in highly complex ecosystems such as tropical forests. We used 240 individual flux measurements of these three GHGs from different soil types, at three topographical positions and in two extreme hydric conditions in the tropical forests of the Guiana Shield (French Guiana, South America) to (1) test the effect of topographical positions on GHG fluxes and (2) identify the soil characteristics driving flux variation in these nutrient-poor tropical soils. Surprisingly, none of the three GHG flux rates differed with topographical position. CO₂ effluxes covaried with soil pH, soil water content (SWC), available nitrogen and total phosphorus. The CH₄ fluxes were best explained by variation in SWC, with soils acting as a sink under drier conditions and as a source under wetter conditions. Unexpectedly, our study areas were generally sinks for N₂O and N₂O fluxes were partly explained by total phosphorus and available nitrogen concentrations. This first study describing the spatial variation of soil fluxes of the three main GHGs measured simultaneously in forests of the Guiana Shield lays the foundation for specific studies of the processes underlying the observed patterns.     

Optothermally Controlled Charge Transfer Plasmons in Au-Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript> Core-Shell Dimers

Functional and reversible plasmonic resonances across the visible and near-infrared spectrum have opened new avenues for developing advanced next-generation nanophotonic devices. In this study, by using optothermally controlled phase-change material (PCM) for plasmonic nanostructures, we successfully induced highly tunable charge transfer plasmon (CTP) resonance modes. To this end, we have chosen a two-member dimer assembly consisting of gold cores and Ge₂Sb₂Te₅ (GST) shells in distant, touching, and overlapping regimes. We show that switching between amorphous (dielectric) and crystalline (conductive) phases of GST allows for achieving tunable dipolar and CTP resonances and enables an effective interplay between these modes along the near-infrared spectrum. By analyzing electromagnetically calculated spectral responses for the dimer antenna in tunneling and direct charge transfer regimes, we confirmed that the induced CTPs in touching and overlapping regimes are highly controllable and pronounced in comparison to the quantum tunneling regime. We also use the precise, fast, and controllable switching between dipolar and CTP resonant modes to develop a telecommunication switch based on a simple metallodielectric dimer. The proposed structures can help designing optothermally controlled devices without morphological variations in the geometry of the design, and having strong potential for advanced plasmon modulation and fast data routing.     

Production of fumonisins B<Subscript>2</Subscript> and B<Subscript>4</Subscript> in <Emphasis Type="Italic">Tolypocladium</Emphasis> species

Tolypocladium inflatum is known primarily for its production of the cyclosporines that are used as an immunosuppressive drug. However, we report here the production of the carcinogenic fumonisins B₂ and B₄ by this biotechnologically relevant fungal genus. These mycotoxins were detected in 11 strains tested from three species: Tolypocladium inflatum, T. cylindrosporum, and T. geodes. Production of fumonisins by Fusarium spp. and Aspergillus niger is highly medium- and temperature-dependent, so the effect of these parameters on fumonisin production by three T. inflatum strains was studied. Maximum production was achieved on media with high sugar content incubated at 25–30°C. Since these results demonstrate that fumonisin production could be widespread within the genus Tolypocladium, the potential contamination of commercial cyclosporine preparations with fumonisins needs to be investigated.     

Influence of cis-[PtCl<Subscript>2</Subscript>(Me<Subscript>2</Subscript>SO)<Subscript>2</Subscript>] on thermal denaturation of albumin

The interaction of cis-[PtCl₂(Me₂SO)₂] with human serum albumin (HSA) and the sensitivity of the complex to heat denaturation as dependent on the duration of incubation have been studied by UV absorption and fluorescence spectroscopy. Optimal conditions for cis-[PtCl₂(Me₂SO)₂] binding to HSA have been determined. The results are compared with the data for the HSA-cisplatin complex. It has been found that binding of HSA with cis-[PtCl₂(Me₂SO)₂] does not result in significant structural changes of the protein.     

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.