Gas adsorption and diffusion in a highly CO2 selective metal–organic framework: molecular simulations

Grand canonical Monte Carlo and equilibrium molecular dynamics simulations were used to assess the performance of an rht-type metal–organic framework (MOF), Cu-TDPAT, in adsorption-based and membrane-based separation of CH₄/H₂, CO₂/CH₄ and CO₂/H₂ mixtures. Adsorption isotherms and self-diffusivities of pure gases and binary gas mixtures in Cu-TDPAT were computed using detailed molecular simulations. Several properties of Cu-TDPAT such as adsorption selectivity, working capacity, diffusion selectivity, gas permeability and permeation selectivity were computed and compared with well-known zeolites and MOFs. Results showed that Cu-TDPAT is a very promising adsorbent and membrane material especially for separation of CO₂ and it can outperform traditional zeolites and MOFs such as DDR, MFI, CuBTC, IRMOF-1 in adsorption-based CO₂/CH₄ and CO₂/H₂ separations.     

New acyclic and cyclie Schiff bases derived from 2,6-diformyl-4-chlorophenol and their interaction with uranyl(Vl), copper(II) and nickel(Il) ions

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

Uranyl(VI), copper(II) and nickel(II) complexes derived from a new compartmental ligand

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

Rhodium(I) and palladium(II) complexes with the Schiff base 2,2-bis((4S)-4-benzyl-2-oxazoline)

The Schiff base 2,2^′-bis((4S)-4-benzyl-2-oxazoline) (I) and its coordination complexes with rhodium(I) and palladium(II) (and with 1,5-cyclo-octadiene and allyl ligands) have been characterised by single-crystal X-ray diffraction, mass spectrometry, ¹³C and ¹H NMR spectroscopy: [Rh(C₂₀H₂₀N₂O₂)(C₈H₁₂)][Rh₂(C₂₀H₂₀N₂O₂)₂](CF₃SO₃)₃ · (CH₃CH₂O) (II) and [Pd(C₂₀H₂₀N₂O₂)(C₃H₅)]CF₃SO₃ (III). We discuss the reasons for the formation of two complex cations for Rh(I), [Rh(C₂₀H₂₀N₂O₂)(C₈H₁₂)]⁺ (IIa) and [Rh₂(C₂₀H₂₀N₂O₂)₂]²⁺ (IIb), and only one for Pd(II).     

Four mononuclear platinum(II) complexes: synthesis,DNA/BSA binding,DNA cleavage and cytotoxicity

Four new platinum(II) complexes: Pt^II L1·H₂O (C1, H₂ L1 = C₂₀H₁₆N₂O₂), Pt^II L2Cl₂ (C2, L2 = C₂₂H₁₆N₂O₂), Pt^II L3Cl₂·H₂O (C3, L3 = C₂₀H₁₆N₂), Pt^II L4Cl₂·0.4H₂O (C4, L4 = C₁₈H₁₄N₄) have been synthesized and characterized by using various physico-chemical techniques. The binding interaction of the four platinum(II) complexes C1–C4 with calf thymus (CT)-DNA has been investigated by UV–Vis and fluorescence emission spectrometry. The apparent binding constant (K _app) values follow the order: C3 > C1 > C2 > C4. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the four platinum(II) complexes C1–C4 showed that the quenching mechanism might be a static quenching procedure. For C1–C4, the number of binding sites was about one for BSA and the binding constants follow the order: C3 (7.08 × 10⁵M^?1) > C1 (2.82 × 10⁵M^?1) > C2 (0.85 × 10⁵M^?1) > C4 (0.15 × 10⁵M^?1). With the single condition change such as absence of an external agent, the DNA cleavage abilities of C3 exhibit remarkable changes. In addition, the cytotoxicity of C3 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) were examined by MTT and showed better antitumor effects on the tested cells.     

Design,synthesis and biological evaluation of N2,N4-disubstituted-1,1,3-trioxo-2H,4H-pyrrolo[1,2-b][1,2,4,6]thiatriazine derivatives as HIV-1 NNRTIs

A series of N₂,N₄-disubstituted-1,1,3-trioxo-2H,4H-pyrrolo[1,2-b][1,2,4,6]thiatriazine derivatives (PTTDs) was designed and synthesized by a facile route. The biological assay results showed that five most potent compounds displayed inhibitory activity against HIV-1 at low micromolar concentrations (EC₅₀ = 5.1–8.9 μM). Structure–activity relationship analysis indicated that N₂-(3-halogenated-benzyl) analogues were more potent than N₂-(unsubstituted-benzyl) analogues. The N₄-substitutions contributed to the antiviral activity in the following order: 2-/3-cyano substituted benzyl > 2-/3-halogenated benzyl > non-substituted benzyl > 4-halogenated benzyl. Docking studies of the representative compound revealed the binding conformation of these compounds and provided critical insights for the further development of PTTD analogues.     

H2O2-Induced Oxidative Stress Affects SO4= Transport in Human Erythrocytes

The aim of the present investigation was to verify the effect of H₂O₂-induced oxidative stress on SO₄⁼ uptake through Band 3 protein, responsible for Cl^-/HCO₃^- as well as for cell membrane deformability, due to its cross link with cytoskeletal proteins. The role of cytoplasmic proteins binding to Band 3 protein has been also considered by assaying H₂O₂ effects on hemoglobin-free resealed ghosts of erythrocytes. Oxidative conditions were induced by 30 min exposure of human erythrocytes to different H₂O₂ concentrations (10 to 300 μM), with or without GSH (glutathione, 2 mM) or curcumin (10 μM), compounds with proved antioxidant properties. Since SO₄⁼ influx through Band 3 protein is slower and better controllable than Cl^- or HCO₃^- exchange, the rate constant for SO₄⁼ uptake was measured to prove anion transport efficiency, while MDA (malondialdehyde) levels and –SH groups were estimated to quantify the effect of oxidative stress. H₂O₂ induced a significant decrease in rate constant for SO₄⁼ uptake at both 100 and 300 μM H₂O₂. This reduction, observed in erythrocytes but not in resealed ghosts and associated to increase in neither MDA levels nor in –SH groups, was impaired by both curcumin and GSH, whereas only curcumin effectively restored H₂O₂-induced changes in erythrocytes shape. Our results show that: i) 30 min exposure to 300 μM H₂O₂ reduced SO₄⁼ uptake in human erythrocytes; ii) oxidative damage was revealed by the reduction in rate constant for SO₄⁼ uptake, but not by MDA or –SH groups levels; iii) the damage was produced via cytoplasmic components which cross link with Band 3 protein; iv) the natural antioxidant curcumin may be useful in protecting erythrocytes from oxidative injury; v) SO₄⁼ uptake through Band 3 protein may be reasonably suggested as a tool to monitor erythrocytes function under oxidative conditions possibly deriving from alcohol consumption, use of drugs, radiographic contrast media administration, hyperglicemia or neurodegenerative diseases.     

Alkaline peroxide pretreatment of corn stover: effects of biomass, peroxide, and enzyme loading and composition on yields of glucose and xylose

Background

Pretreatment is a critical step in the conversion of lignocellulose to fermentable sugars. Although many pretreatment processes are currently under investigation, none of them are entirely satisfactory in regard to effectiveness, cost, or environmental impact. The use of hydrogen peroxide at pH 11.5 (alkaline hydrogen peroxide (AHP)) was shown by Gould and coworkers to be an effective pretreatment of grass stovers and other plant materials in the context of animal nutrition and ethanol production. Our earlier experiments indicated that AHP performed well when compared against two other alkaline pretreatments. Here, we explored several key parameters to test the potential of AHP for further improvement relevant to lignocellulosic ethanol production.

Results

The effects of biomass loading, hydrogen peroxide loading, residence time, and pH control were tested in combination with subsequent digestion with a commercial enzyme preparation, optimized mixtures of four commercial enzymes, or optimized synthetic mixtures of pure enzymes. AHP pretreatment was performed at room temperature (23°C) and atmospheric pressure, and after AHP pretreatment the biomass was neutralized with HCl but not washed before enzyme digestion. Standard enzyme digestion conditions were 0.2% glucan loading, 15 mg protein/g glucan, and 48 h digestion at 50°C. Higher pretreatment biomass loadings (10% to 20%) gave higher monomeric glucose (Glc) and xylose (Xyl) yields than the 2% loading used in earlier studies. An H₂O₂ loading of 0.25 g/g biomass was almost as effective as 0.5 g/g, but 0.125 g/g was significantly less effective. Optimized mixtures of four commercial enzymes substantially increased post-AHP-pretreatment enzymatic hydrolysis yields at all H₂O₂ concentrations compared to any single commercial enzyme. At a pretreatment biomass loading of 10% and an H₂O₂ loading of 0.5 g/g biomass, an optimized commercial mixture at total protein loadings of 8 or 15 mg/g glucan gave monomeric Glc yields of 83% or 95%, respectively. Yields of Glc and Xyl after pretreatment at a low hydrogen peroxide loading (0.125 g H₂O₂/g biomass) could be improved by extending the pretreatment residence time to 48 h and readjusting the pH to 11.5 every 6 h during the pretreatment. A Glc yield of 77% was obtained using a pretreatment of 15% biomass loading, 0.125 g H₂O₂/g biomass, and 48 h with pH adjustment, followed by digestion with an optimized commercial enzyme mixture at an enzyme loading of 15 mg protein/g glucan.

Conclusions

Alkaline peroxide is an effective pretreatment for corn stover. Particular advantages are the use of reagents with low environmental impact and avoidance of special reaction chambers. Reasonable yields of monomeric Glc can be obtained at an H₂O₂ concentration one-quarter of that used in previous AHP research. Additional improvements in the AHP process, such as peroxide stabilization, peroxide recycling, and improved pH control, could lead to further improvements in AHP pretreatment.     

Studies on Mitomycins,Carcinostatic Antibiotics

Mitomycin A (C₁₆H₁₉O₆N₃) and mitomycin C (C₁₅H₁₈O₅N₄) are pigments which have the quinoid structure. When treated with aqueous ammonia, mitomycin A is converted to mitomycin C. Acid hydrolysis of mitomycin C gave three degradation products, namely, C₁₄H₁₅O₅N₄, C₁₄H₁₅O₆N₃ and C₁₃H₁₄O₅N₂. Acetylation with acetic anhydride and pyridine and methylation with methyl iodide gave monoacetyl and monomethyl derivatives of mitomycin C respectively, though diacetate of demethyl derivatives were obtained when boiled with acetic anhydride.     

Growth, denitrification and nitrate ammonification of the rhizobial strain TNAU 14 in presence and absence of C2H4 and C2H2

Soil-N (NO₃ ^?) initiates as far as a threshold concentration is surpassed manifold physiological reactions on N₂-fixation. Organic N and ammonium oxidised to NO₃ ^? means oxygen depletion. Plants suffering under O₂ or infection stress start to excrete ethylene (C₂H₄). C₂H₄ widens the root intercellulars that O₂-respiration will continue. Now microbes may more easily enter the plant interior by transforming the reached methionine into C₂H₄. Surplus nitrate and C₂H₄ inhibit nodulation of leguminous plants. Excess NO₃ ^? in the nodulesphere could be diminished by N₂-fixing bacteria which in addition can denitrify or ammonify nitrate. Consequently, it was asked whether C₂H₄ interferes with the potential of N₂-fixing bacteria to reduce nitrate. The groundnut-nodule isolate TNAU 14, from which it was known that it denitrifies and ammonifies nitrate, served as inoculum of a KNO₃-mannitol-medium that was incubated under N₂-, 1% (v/v) N₂?C₂H₄-, and 1% (v/v) N₂?C₂H₂-atmosphere in the laboratory. C₂H₂ was included into the experiments because it is frequently used to quantify N₂-fixing potentials (acetylene reduction array, ARA). Gene-16S rDNA-sequencing and physiological tests revealed a high affiliation of strain TNAU 14 toRhizobium radiobacter andRhizobium tumefaciens. Strain TNAU 14 released N₂O into the bottle headspace in all treatments, surprisingly significantly less in presence of C₂H₂. Nitrate-ammonification was even completely blocked by C₂H₂. C₂H₄, in contrast rather stimulated growth, denitrification, and nitrate-ammonification of strain TNAU 14 which consumed the released NH₄ ⁺ during continuing incubation.     

Evaluation of phosphorus in forest soils: Comparison of phosphorus uptake,extraction method and soil properties

Summary Phosphorus in soils from plantation of red pine (Pinus resinosa Ait.) was determined using six extractants: 0.002N H₂SO₄ (pH 3.0); 0.025N HCl+ +0.03N NH₄F; 0.5N NaHCO₃ (pH 8.5);N NH₄OAc (pH 4.8); anion exchange resin (Dower –2, Cl-form); H₂O. Correlations of extractable P with Al- and Al-+Fe-P indicated that these fractions are the dominant forms of inorganic P in most of the soils.Uptake of P by corn and Monterey pine seedlings grown in greenhouse culture was correlated with soil P extracted by the different methods. The most successful of the extractants for predicting P uptake was resin extractable P; the simple correlation coefficients were 0.811 and 0.609 for pine and corn respectively. P uptake by pine correlated significantly with 0.002N H₂SO₄ P (r=0.679),N NH₄OAc P (r=0.443), H₂O P (r=0.549) and Al-+Fe-P (r=0.532) while P uptake by corn correlated with 0.002N H₂SO₄ P (r=0.579), H₂O P (r=0.477) and organic P (r=0.460). Per cent P in pine seedling tops correlated significantly with 0.002N H₂SO₄, resin andN NH₄ OAc extractable P. Multiple regressions which included silt+clay and organic P improved correlations of some soil tests with P uptake in corn and pine seedlings respectively.Research supported by the School of Natural Resources, College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison, the Wisconsin Department of Natural Resources and FAO Fellowship to the senior author.     

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.     

Rapid micro Kjeldahl digestion of cereal grains and other biological materials

To accomplish the micro Kjeldahl digestion of cereal grains and other biological materials in approximately 10 minutes, two techniques were developed: (1) digestion in the presence of hydrogen peroxide, K₂SO₄HgOH₂SO₄ mixture, with lauric acid as anti-foaming agent, and (2) precarbonization of sample in K₂SO₄HgOH₂SO₄ mixture to produce foam-forming materials which are immediately destroyed by H₂O₂. Oxidation of the sample is enhanced by H₂O₂ and high digestion temperature resulting from increased salt-acid ratio.     

Treatment of cotton seeds for germination

Summary Effects of H₂SO₄, H₂O₂, C₂H₅OH and of acetone on germination of cotton seeds and on the growth of seedling root were studied under laboratory conditions. H₂SO₄ or H₂O₂ hastened germination but decreased the ultimate number of seeds germinated. Higher temperature (27°C) hastened germination and increased the number of seeds germinated. Root length remained unaffected by treatments at room temperature while H₂SO₄ or H₂SO₄/H₂O₂ substantially decreased it at 27°C.     

Methane and carbon dioxide adsorption and diffusion in amorphous,metal-decorated nanoporous silica

The adsorptive and diffusive behaviour of methane and carbon dioxide in amorphous nanoporous adsorbents composed of spherosilicate building blocks, in which isolated metal sites have been distributed, is examined. The adsorbent contains cubic silicate building blocks (spherosilicate units: Si₈O₂₀), which are cross linked by SiCl₂O₂ bridges and decorated with either –OTiCl₃ or –OSiMe₃ groups of the other cube corners. The model structures were generated to correspond to experimentally synthesised materials, matching physical properties including density, surface area and accessible volume. It is shown that both methane and carbon dioxide adsorb via physisorption only in the modelled materials. Adsorption isotherms and energies at 300 K for pressures up to 100 bar were generated via molecular simulation. The maximum gravimetric capacity of CH₄ is 16.9 wt%, occurring at 300 K and 97 bar. The maximum gravimetric capacity of CO₂ is 50.3 wt%, occurring at 300 K and 51.6 bar. The best performing adsorbent was a low-density (high accessible volume) material with no –OTiCl₃ groups. The presence of –OTiCl₃ did not enhance physisorption even on a volumetric basis, and the high molecular weight of –OTiCl₃ groups is a significant penalty on a gravimetric basis. Based on the pair correlation functions, the most favourable adsorption sites for both adsorbates are located in front of the faces of spherosilicate cubes. The self-diffusivity and activation energy for diffusion are also reported.     

Synthesis, crystal structure and vibrational spectroscopy of a novel mixed ligands Ni(II) pentaborate: [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2

A novel organic-inorganic hybrid pentaborate [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂][B₅O₆(OH)₄]₂ has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻ and nickel complex cation of [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given.     

Isolation of Novel Antifungal Antibiotics,Ezomycins A1, A2, B1 and B2

From ezomycin complex produced by a strain of Streptomyces were isolated four components named ezomycins A₁ (C₂₆H₄₀N₈O₁₆S), A₂ (C₁₉H₂₈N₆O₁₃), B₁ (C₂₆H₃₉N₇O₁₇S) and B₂ (C₁₉H₂₇N₅O₁₄) which are new pyrimidine nucleosides. Ezomycins A₁ and B₁ containing l-cystathionine were found to be responsible for specific antimicrobial activity of the complex against Sclerotinia and Botrytis species.     

Isolation and properties of a unidirectional H2-oxidizing hydrogenase from the strictly anaerobic N2-fixing bacterium Clostridium pasteurianum W5

A unidirectional H₂-oxidizing hydrogenase (H₂ase-HO) has been isolated from the anaerobic N₂-fixer $\text{Clostridium pasteurianum}$ W5. Extensively purified (> 200-fold or > 400–800 μmoles H₂ oxidized/min/mg protein) H₂ase-HO can use ferredoxin (Fd), methyl viologen (MV), benzyl viologen, methylene blue or dichlorophenolindophenol as the sole electron acceptor but does not produce H₂ from reduced Fd or MV. H₂ase-HO has a lower mol. wt., is less negatively charged and less O₂-sensitive than the classical bidirectional H₂ase from the same organism. The level of the H₂-oxidizing enzyme is higher in N₂-fixing cells than in NH₃-grown cells. H₂ase-HO occurs mainly outside the cell membrane and is inhibited by carbon monoxide.     

Joint Action of O(3) and SO(2) in Modifying Plant Gas Exchange

The joint action of O₃ and SO₂ stress on plants was investigated by determining the quantitative relationship between air pollutant fluxes and effects on stomatal conductance. Gas exchange measurements of O₃, SO₂, and H₂O vapor were made for Pisum sativum L. (garden pea). Plants were grown under controlled environments, and O₃, SO₂, and H₂O vapor fluxes were evaluated with a whole-plant gas exchange chamber using the mass-balance approach. Maximum O₃ and SO₂ fluxes per unit area (2 sided) into leaves averaged 8 nanomoles per square meter per second with exposure to either O₃ or SO₂ at 0.1 microliters per liter. Internal fluxes of either O₃ or SO₂ were reduced by up to 50% during exposure to combined versus individual pollutants; the greatest reduction occurred with simultaneous versus sequential combinations of the pollutants. Stomatal conductance to H₂O was substantially altered by the pollutant exposures, with O₃ molecules twice as effective as SO₂ molecules in inducing stomatal closure. Stomatal conductance was related to the integrated dose of pollutants. The regression equations relating integrated dose to stomatal conductance were similar with O₃ alone, O₃ plus added SO₂, and O₃ plus SO₂ simultaneously; i.e. a dose of 100 micromoles per square meter produced a 39 to 45% reduction in conductance over nonexposed plants. With SO₂ alone, or SO₂ plus added O₃, a dose of 100 micromoles per square meter produced a 20 to 25% reduction in conductance. When O₃ was present at the start of the exposure, then stomatal response resembled that for O₃ more than the response for SO₂. This study indicated that stomatal responses with combinations of O₃ and SO₂ are not dependent solely on the integrated dose of pollutants, but suggests that a metabolic synergistic effect exists.     

A nitrogen-balance study using labelled fertilizer in a gas lysimeter

Summary A gas lysimeter study showed negligible losses of gaseous N₂ or N₂O from rhodes grass plants growing in soil fertilized with either (N¹⁵H₄)₂SO₄ or KN¹⁵O₃; isotope recovered from the soil: plant system averaged respectively 100.5% and 98.9%; neither differed significantly from 100%. Small amounts of ammonia were volatilized into lysimeter atmospheres, averaging 0.6% of that applied as labelled ammonium-N and 0.1% of that as nitrate-N. The importance of these findings is discussed in relation to the conduct of N balance studies.