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IntroductionLow voltage-activated T-type calcium channels (T-type ICa), CaV3.1, CaV3.2, and CaV3.3 are opened by small depolarizations from the resting membrane potential in many cells and have been associated with neurological disorders including absence epilepsy and pain. Δ9-tetrahydrocannabinol (THC) is the principal psychoactive compound in Cannabis and also directly modulates T-type ICa, however, there is no information about functional activity of most phytocannabinoids on T-type calcium channels, including Δ9-tetrahydrocannabinol acid (THCA), the natural non-psychoactive precursor of THC. The aim of this work was to characterize THCA effects on T-type calcium channels.Materials and MethodsWe used HEK293 Flp-In-TREx cells stably expressing CaV3.1, 3.2 or 3.3. Whole-cell patch clamp recordings were made to investigate cannabinoid modulation of ICa.ResultsTHCA and THC inhibited the peak current amplitude CaV3.1 with a pEC50s of 6.0 ± 0.7 and 5.6 ± 0.4, respectively. 1μM THCA or THC produced a significant negative shift in half activation and inactivation of CaV3.1 and both drugs prolonged CaV3.1 deactivation kinetics. THCA (10 μM) inhibited CaV3.2 by 53% ± 4 and both THCA and THC produced a substantial negative shift in the voltage for half inactivation and modest negative shift in half activation of CaV3.2. THC prolonged the deactivation time of CaV3.2 while THCA did not. THCA inhibited the peak current of CaV3.3 by 43% ± 2 (10μM) but did not notably affect CaV3.3 channel activation or inactivation, however, THC caused significant hyperpolarizing shift in CaV3.3 steady state inactivation.DiscussionTHCA modulated T-type ICa currents in vitro, with significant modulation of kinetics and voltage dependence at low μM concentrations. This study suggests that THCA may have potential for therapeutic use in pain and epilepsy via T-type channel modulation without the unwanted psychoactive effects associated with THC.

A Single-Event MicroKinetic (SEMK) model has been extended towards the simulation of Steady State Isotopic Transient Kinetic Analysis (SSITKA) data for Co catalyzed Fischer-Tropsch Synthesis (FTS). The extended model considers two types of sites and both direct and H-assisted CO dissociation. Regression of the model parameters to the data obtained from 17 steady state and 11 SSITKA experiments resulted in physicochemically meaningful estimates for the activation energies and atomic chemisorption enthalpies. The application of the phenomenological UBI-QEP method allows to physically interpret the nature of the two site types considered in the model, i.e., terrace and step sites. A reaction path analysis shows that over 80 percent of the CO reacts on the step sites. Furthermore, chain growth exclusively occurs on these sites. The terrace sites are less reactive for CO dissociation and are identified as responsible for methane production. A fraction of the alkenes, produced on the step sites, is hydrogenated to alkanes on the terrace sites. Based on model simulations, the metal particle size effect, i.e., a lower TOF, higher methane selectivity and increasing alkane to alkene ratio with decreasing metal particle size, is attributed to an increasing relative importance of the terrace sites on the reaction kinetics.

The study of the equilibrium concentrations for the extraction separation of cobalt from mixed sulfate solution with N-salicylideneaniline in membrane contactors is investigated. The reaction equilibrium constant (Kex) of 4.7 L2mol−2 was obtained from the modeling of the equilibrium distribution curves, which is carried out from the mass action law. A separation factor of 30,74 of cobalt was obtained. The calculation of the distribution coefficient (D) in the membrane contactors is carried out from global mass balances (operating line) and linear extraction isotherms in membrane contactors. The extraction kinetics of cobalt in the aqueous and organic phases in hollow fiber membrane contactors became slow and steady state is quickly reached. The steady state experimental concentration in aqueous and organic phase does not correspond to the concentration predicted by the calculation this deviation between the steady state concentration and calculated data could be explained that the diffusion of metal complex in the microporous is the main limiting step of mass transfer..

The search of new organic emitters is receiving a strong motivation by the development of ORTP materials. In the present study we report on the preparation, optical and photophysical characterization, by both steady state and time resolved techniques, of two pyrene-functionalized cyclic triimidazole derivatives. Together with the already reported mono-substituted derivative, the di- and tri-substituted members of the family have revealed as intriguing emitters characterized by impressive quantum yields in solution and RTP properties in the solid state. In particular, phosphorescence lifetimes increase from 5.19 to 20.54 and 40.62 ms for mono-, di- and trisubstituted compounds, respectively. Based on spectroscopical results and theoretical DFT/TDDFT calculations on the di-pyrene molecule, differences in photophysical performances of the three compounds have been assigned to intermolecular interactions increasing with the number of pyrene moieties appended to the cyclic triimidazole scaffold.

We employed an approach combining reaction kinetics measurements at steady state conditions, electronic structure calculations employing density functional theory, and microkinetic modeling for acetone hydrogenation to provide insights into the effects of water on metal catalyst surfaces for the hydrogenation of oxygenates over a wide range of reaction conditions. Elucidation of the repulsive interactions due to adsorbed water molecules at various reaction conditions provides a basis to formulate rate expressions for heterogeneous catalytic processes of biomass oxygenates. Reaction kinetics experiments were carried out at partial pressures of H2, acetone, water and helium in the range of 0.51–0.79, 0.02–0.13, 0.08–0.23, 0–0.28 atm, respectively. We show that the addition of water enhances the hydrogenation rate at 353 K and 1 atm on oxophilic metal catalysts such as Ru/C, whereas the same promotional effect of water is not observed for Pt-based catalysts. Microkinetic model predictions for the hydrogenation of acetone on Ru in the absence and presence of water, using enthalpies and entropies obtained from DFT calculations, were in agreement with the experimentally observed reaction orders and activation barriers. The model shows that a water-assisted hydroxypropyl path is expected to be the favored path on Ru with a rate-determining step of H-OH-mediated hydrogenation of C3H6OH (i.e., the hydroxypropyl intermediate formed by H2O-mediated initial hydrogenation of acetone) to produce isopropyl alcohol (IPA). Furthermore, hydrogen, acetone, hydroxypropyl intermediate and hydroxyl species were predicted to be abundant on the Ru surface with a high coverage of nearly 85%. The combined studies of computational and experimental catalysis on hydrogenation reactions help to elucidate the mechanistic role of water on metal catalyzed reactions for producing chemical building blocks from biomass-derived oxygenates.

Bloating of metal droplets in the BOF is important in developing fundamental models of the process. Bloating is controlled by the decarburization behavior of individual metal droplets in oxidizing slag. In this paper, a detailed investigation has been performed to elucidate the mechanism and rate controlling steps for decarburization of droplets over a range of droplet carbon concentration, droplet mass, slag basicity and slag FeO concentration. Four different carbon levels and three droplet masses were tested. Droplets typically exhibited three stages of decarburization: incubation period, where decarburization was mostly on the outer surface of the droplet, followed by a steady state reaction period where most decarburization was internal, and finally the end decarburization period. The rate of decarburization was found to be a mixed controlled process; the contributions of resistance from slag transport, interfacial chemical reaction, internal nucleation and growth of bubbels varied based on slag and metal chemistry. A mixed controlled kinetic model has been developed for steady state decarburization period and a partial validation of the mixed controlled kinetic model has been presented here. By varying slag FeO concentration and basicity for droplets containing 2.5 wt pct C, mixed controlled kinetics of decarburization reaction were explored.

Past studies have established mesophyll diffusion conductance to CO2 (gm ) as a variable and significant limitation to plant photosynthesis under steady-state conditions. However, the role of gm in influencing photosynthesis (A) during the transient period of light induction is largely unknown. We combined gas exchange measurements with laser-enabled carbon isotope discrimination measurements to assess gm during photosynthetic induction, using Arabidopsis as the measurement species. Our measurements revealed three key findings: (1) we found that the rate at which gm approached steady state during induction was not necessarily faster than the induction rate of the carboxylation process, contradictory to what has been suggested in previous studies; (2) gm displayed a strong and consistent coordination with A under both induction and steady-state settings, hinting that the mechanism driving gm -A coupling does not require physiological stability as a prerequisite; and (3) photosynthetic limitation analysis of our data revealed that when integrated over the entire induction period, the relative limitation of A imposed by gm can be as high as > 35%. The present study provides the first demonstration of the important role of gm in limiting CO2 assimilation during photosynthetic induction, thereby pointing to a need for more research attention to be devoted to gm in future induction studies.

Tubulin self-association is a critical process in microtubule dynamics. The early intermediate structures, energetics, and their regulation by fluxes of chemical energy, associated with guanosine triphosphate (GTP) hydrolysis, are poorly understood. We reconstituted an in vitro minimal model system, mimicking the key elements of the nontemplated tubulin assembly. To resolve the distribution of GTP- and guanosine diphosphate (GDP)-tubulin structures, at low temperatures (∼10 °C) and below the critical concentration for the microtubule assembly, we analyzed in-line size-exclusion chromatography-small-angle X-ray scattering (SEC-SAXS) chromatograms of GTP- and GDP-tubulin solutions. Both solutions rapidly attained steady state. The SEC-SAXS data were consistent with an isodesmic thermodynamic model of longitudinal tubulin self-association into 1D oligomers, terminated by the formation of tubulin single rings. The analysis showed that free dimers coexisted with tetramers and hexamers. Tubulin monomers and lateral association between dimers were not detected. The dimer-dimer longitudinal self-association standard Helmholtz free energies were -14.2 ± 0.4 kBT (-8.0 ± 0.2 kcal mol-1) and -13.1 ± 0.5 kBT (-7.4 ± 0.3 kcal mol-1) for GDP- and GTP-tubulin, respectively. We then determined the mass fractions of dimers, tetramers, and hexamers as a function of the total tubulin concentration. A small fraction of stable tubulin single rings, with a radius of 19.2 ± 0.2 nm, was detected in the GDP-tubulin solution. In the GTP-tubulin solution, this fraction was significantly lower. Cryo-TEM images and SEC-multiangle light-scattering analysis corroborated these findings. Our analyses provide an accurate structure-stability description of cold tubulin solutions.

We showed in the present study that, not unlike in adult patients with sickle cell disease (SCD), Townes mice exhibit increases in serum intestinal fatty acid binding proteins and lipopolysaccharides (LPS), together with a breach in the intestinal barrier. These abnormalities increased rapidly after the induction of vaso-occlusive crisis (VOC). We also confirmed higher intestinal microbial density in SCD. These findings support the concept that SCD and/or its complications, and not hospitalisation or medications, are responsible for the intestinal pathophysiological changes. The present results provide the basis for use of Townes mice to further elucidate the mechanistic relationship between intestinal pathophysiology and VOC.

Dynamic information of intracellular transcripts is essential to understand their functional roles. Routine RNA-sequencing (RNA-seq) methods only measure RNA species at a steady state and do not provide RNA dynamic information. Here, we develop addition-elimination mechanism-activated nucleotide transition sequencing (AENT-seq) for transcriptome-wide profiling of RNA dynamics. In AENT-seq, nascent transcripts are metabolically labeled with 4-thiouridine (4sU). The total RNA is treated with N2H4·H2O under aqueous conditions. N2H4·H2O is demonstrated to convert 4sU to 4-hydrazino cytosine (C*) based on an addition-elimination chemistry. C* is regarded as cytosine (C) during the DNA extension process. This 4sU-to-C transition marks nascent transcripts, so it enables sequencing analysis of RNA dynamics. We apply our AENT-seq to investigate transcript dynamic information of several genes involved in cancer progression and metastasis. This method uses a simple chemical reaction in aqueous solutions and will be rapidly disseminated with extensive applications.

Hypercontractility of the cardiac sarcomere may be essential for the underlying pathological hypertrophy and fibrosis in genetic hypertrophic cardiomyopathies. Aficamten (CK-274) is a novel cardiac myosin inhibitor that was discovered from the optimization of indoline compound 1. The important advancement of the optimization was discovery of an Indane analogue (12) with a less restrictive structure-activity relationship that allowed for the rapid improvement of drug-like properties. Aficamten was designed to provide a predicted human half-life (t1/2) appropriate for once a day (qd) dosing, to reach steady state within two weeks, to have no substantial cytochrome P450 induction or inhibition, and to have a wide therapeutic window in vivo with a clear pharmacokinetic/pharmacodynamic relationship. In a phase I clinical trial, aficamten demonstrated a human t1/2 similar to predictions and was able to reach steady state concentration within the desired two-week window.

In this study, the physical states of cellulose in 1-allyl-3-methylimidazolium chloride (AmimCl) were analyzed via rheological observations under three different conditions: namely, steady state, small amplitude oscillatory shear, and large amplitude oscillatory shear conditions. The physical state of the solution changed from an isotropic phase to a gel structure via a liquid crystalline (LC) phase as the concentration increased. The rheological analysis showed that the 16 wt% solution was physically gelled in the anisotropic phase. This instantaneous gelation at the LC phase markedly enhanced the mechanical performance of the film obtained from the solution. This study provides a fundamental strategy for significant improvement in the mechanical properties of cellulose fibers or films.

Oxidatively generated DNA damage is of paramount importance in a wide range of physiological and pathophysiological processes. Urinary 8-oxo-7,8-dihydro-2-deoxyguanosine (8-oxodG) is often used as an outcome marker in studies on the role of oxidatively generated DNA damage, but its exact relation to intracellular damage levels and variations in DNA repair have been unclear. Using a new approach of quantitative kinetic modeling inspired by pharmacokinetics, we find evidence that in steady state - i.e. when systemic consequences of given change in damage or cellular removal rates have stabilized - the urinary excretion of 8-oxodG is closely correlated to rates of damage and intracellular 8-oxodG levels, but independent of the rate of cellular removal. Steady state was calculated to occur within approximately 12 h. A similar pattern was observed in a model of the corresponding RNA marker 8-oxo-7,8-dihydroguanosine (8-oxoGuo), but with steady-state occurring slower (up to 5 d). These data have significant implications for the planning of studies and interpretation of data involving urinary 8-oxodG/8-oxoGuo excretion as outcome.HighlightsThe kinetics of 8-oxodG/8-oxoGuo formation, removal and excretion were simulated in silico.The model was based on existing data on 8-oxodG/8-oxoGuo levels and removal/excretion rates.Intracellular 8-oxodG/8-oxoGuo was closely correlated with urinary excretion in steady state.Changes in removal rates did not influence urinary excretion of 8-oxodG/8-oxoGuo.

The photosynthesis of vitamin D3 in mammalian skin results from UV-B irradiation of provitamin D3 (7-dehydrocholesterol, DHC) at ca. 290 nm. Upon return to the ground state, the hexatriene product, previtamin D3, undergoes a conformational equilibration between helical gZg and more planar tZg and tZt forms. The helical gZg forms provide a pathway for the formation of vitamin D3 via a [1,7]-sigmatropic hydrogen shift. Steady state photolysis and UV transient absorption spectroscopy are combined to explore the conformational relaxation of previtamin D3 formed from DHC in isotropic solution and confined to lipid bilayers chosen to model the biological cell membrane. The results are compared with measurements for two analogues: previtamin D2 formed from ergosterol (provitamin D2) and previtamin D3 acetate formed from DHC acetate. The resulting spectral dynamics are interpreted in the context of simulations of optical excitation energy and oscillator strength as a function of conformation. In solution, the relaxation dynamics and steady state product distributions of the three compounds are nearly identical, favoring tZg forms. When confined to lipid bilayers, the heterogeneity and packing forces alter the conformational distributions and enhance the population of a gZg conformer capable of vitamin D formation.

This is the first account of the kinetics of free radical scavenging by bacterioruberin obtained from cells of Haloferax alexandrinus GUSF-1(KF796625), grown at optimum conditions of 25% NaCl, pH 7, 42 °C, 150 rpm in NaCl Tryptone yeast extract medium and light. Bacterioruberin separated from methanolic extract displayed characteristics absorption peaks at 368, 386, 463, 492 and 525 nm and gave an m/z value of 740.4 (C50H76O4) in Liquid Chromatography-Mass Spectroscopy validating its purity. Bacterioruberin (13 µM) decolorized and decayed 0.2 mM 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•) monitored at 517 nm and reached a steady state within 30 min. An EC50 of 6.50 µM ± 0.27 (4.81 µg/mL ± 0.2) was deduced for the 0.2 mM DPPH•-bacterioruberin reaction using the GraphPad Prism 9 statistical software and employing the right-angled triangle technique. The study also revealed a comprehensive information of the total kinetic activity of bacterioruberin with DPPH•: the antioxidant activity index was 16.38 ± 0.67; time needed to reach the steady state with the added EC50—30 min; the antiradical power 30.77 ± 1.27 and the antiradical efficiency of 54.7 × 10–3 ± 2.24, thus reflecting the strong antioxidant nature of bacterioruberin. Scavenging of DPPH• by bacterioruberin was a pseudo-first-order reaction with a rate constant k2 of 2.76 × 10–5 ± 0.001 µM−1 s−1 calculated at t = 0 or initial time and t = 30 min. The knowledge of the kinetics of bacterioruberin to scavenge DPPH• adds to its effective application as an antioxidant in medicinal use, pharmaceutical products and others. Additionally, the use of simple conventional method of DPPH• free radical scavenging, monitored using an easily available laboratory spectrophotometer, will certainly help in the effective use of any antioxidant compound.

Modeling the flow and level of prostaglandins in open systems under the action of prostaglandin H synthase (PGHS) inhibitors (nonsteroidal anti-inflammatory drugs, NSAIDs) was carried out. These open systems included a steady PGHS input, fast inactivation of PGHS during the reaction, degradation of all PGHS forms, conversion of prostaglandin (PG) to biologically inactive substances, and various types of delivery of inhibitors and substrate (arachidonic acid, AA). A slow reversible inhibitor of PGHS (indomethacin) and a slow irreversible inhibitor of PGHS (aspirin) were considered as inhibitors. The explicit analytical expressions for flows and concentrations in steady state and transient mode were obtained. In steady state the dependences of flow and level of PG on the concentration of AA were described by the Michaelis–Menten-type equation. The values of the maximum flows, maximum levels, and Michaelis constant in these equations are inversely proportional to the constant of inactivation of the enzyme during the reaction. In the closed systems, slow PGHS inhibitors are manifested as non-competitive with respect to AA, but in open systems, their behavior is fully competitive with respect to AA, so the presence of inhibitor increases the range of changes of PG level under the change of AA concentration. The reversible inhibitor (indomethacin), in contrast to the irreversible inhibitor (aspirin), in transient mode has been shown to manifest itself as the repository for the active enzyme because of the formation of enzyme-inhibitory complexes. The system disturbance under the rapid increase of indomethacin concentration leads to the biphasic change of the PG level: after the initial rapid decrease it increases gradually to the new steady state. In the presence of indomethacin, the system disturbance under the rapid increase of AA concentration leads to the release of the enzyme from enzyme-inhibitory complexes, and the PG level for a certain period significantly increases compared with the absence of inhibitor. The results of modeling of the regulation of the level of prostaglandins in different states of the open systems undoubtedly need to be used in the study of NSAIDs in vivo.

The method combining density functional theory (DFT) calculations with microkinetic modeling has attracted increasing attention in obtaining a deeper understanding of catalytic reactions. While product desorption is conventionally regarded as an equilibrated process in the microkinetic modeling, it might be influential to product selectivity when competing reactions should be considered. In this work, a complex reaction network is established first for the methane steam reforming reaction using the equilibrium and immobile models over Ni, Pd, and Pt surfaces. This provides a basis to further investigate the reaction mechanism and kinetic modeling results. The results show that when different desorption models are considered, the total activity regarding methane conversion and the coverage and DRC value of the main species at the steady state are the same on each surface. In contrast, the mechanism of CO2 formation is varied based on different desorption models. Consequently, the rate and selectivity of CO2 generation on each metal catalyst are significantly improved when the barrier of CO desorption is considered in the microkinetic modeling compared with the modeling only with barrierless CO desorption.

Xanthan gum (XG) is widely used in cosmetic and pharmaceutic products (creams, pastes) and in oil industry (drilling fluids) as a stabilizing and/or thickening agent. In literature, its rheological behavior is mainly presented as that of a shear-thinning or a yield stress fluid. Here, in order to clarify this rheological behavior, we study in detail the flow characteristics during continued flow under given conditions (i.e., controlled stress) for a mass concentration ranging from 0.2 to 5%. We are thus able to identify the apparent flow curve of the material after a short flow duration and the flow curve in steady state (i.e., after a long flow duration). The validity of this flow curve, determined from standard rheometry, is confirmed by magnetic resonance velocimetry. These materials start to exhibit a yield stress behavior beyond some critical xanthan or salt concentration. In that case, a significant increase (by a factor up to 5) of the apparent viscosity is observed during flow in some range of stresses, before reaching a steady state. This original rheopectic effect might be due, after some time of flow associated with deformation and reconfiguration of the XG molecules, to the progressive formation of intermolecular links such as hydrogen bonds and/or intermolecular association due to acetate residues.

Excited state deactivation properties and the effects of solvent hydrogen bonding (HB) on the photophysical behavior of 2,2'-dypyridylamine (DPyA) were investigated by steady state and time-resolved fluorescence experiments, molecular docking, and density functional theory (DFT) calculations. In addition to the polarity effect, the contributions of solvent HB donation (HBD) acidity and HB acceptance (HBA) basicity to modulate the solvatochromic spectral properties were estimated from multiparametric linear regression analysis using Kamlet-Taft (KT) and Catalan formalisms. The importance of C-N bond torsion, leading to the trans → cis conversion, was manifested by substantial increase in DPyA fluorescence yield in the presence of cyclodextrin (CD) and glycerol. The unusually low fluorescence yield in aqueous medium was explained on the basis of synergistic effect of solvent hydrogen bonding combined with excited state conformational isomerization, which renders DPyA to be an excellent environment sensitive fluorescence reporter. The experimental results were verified with structural insights obtained from DFT calculations at B3LYP/6-311++G(d,p) level and construction of potential energy surface (PES) in the ground state as well as in the excited states.

The metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P P $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

BACKGROUND Aripiprazole is regarded as the first-line antipsychotic medication. Long-term aripiprazole therapy can cause hypoprolactinemia, which may result from its activity as a dopamine agonist. However, there is little information on hypoprolactinemia and steady-state aripiprazole concentrations. METHODS The subjects included 66 male and 177 female patients diagnosed with schizophrenia who were treated with aripiprazole. The plasma concentrations of aripiprazole and dehydroaripiprazole and the plasma concentration of prolactin were measured using high-performance liquid chromatography and enzyme immunoassay, respectively. A prolactin concentration of

In the context of the anaerobic digestion of slowly biodegradable substrates for energy and chemicals production, this study investigated the anaerobic digestion of cellulose without any chemical pre-treatments using open (undefined) mixed microbial cultures. The anaerobic conversion of cellulose was investigated in extended-length (run length in the range 518–734 days) batch and semi-continuous runs (residence time 20–80 days), at high cellulose concentration (20–40 g L−1), at temperatures of 25 and 35 °C. The maximum cellulose removal was 77% in batch (after 412 days) and 60% (at 80 days residence time) in semi-continuous experiments. In semi-continuous experiments, cellulose removal increased as the residence time increased however the cellulose removal rate showed a maximum (0.17 g L−1 day−1) at residence time 40–60 days. Both cellulose removal and removal rate decreased when cellulose concentration in the feed was increased from 20 to 40 g L−1. Liquid-phase products (ethanol and short chain organic acids) were only observed under transient conditions but not at the steady state of semi-continuous runs. Most of the observed results were well described by a mathematical model which included cellulose hydrolysis and growth on the produced glucose. The model provided insight into the physical phenomena behind the observed results.

The direct synthesis reaction (H2 + O2 → H2O2) may provide a low-cost method to form H2O2 if catalytic systems with sufficient selectivities and stabilities are developed. Here, we examine how sodium bromide, a ubiquitous promoter for direct synthesis, impacts steady-state rates and apparent barriers for H2O2 and H2O formation in water and relate changes to the effect of NaBr on surface and bulk properties of Pd nanoparticle catalysts. Comparisons of turnover rates and selectivities measured over an extended period (>80 h) demonstrate that these systems require more than 10 h to reach steady-state, whereupon, H2O2 selectivities depend strongly upon [NaBr] and increase from 17% in pure water to ~65% at 10−4 M NaBr (55 kPa H2, 200 kPa O2). Contact with these NaBr solutions irreversibly modifies Pd nanoparticles, such that H2O2 selectivities remain at 40% in pure water, due to irreversible uptake of Br*-atoms. Bromide adsorption isotherms measured show that reduced Pd nanoparticles adsorb several monolayers of Br*-atoms, which suggests Br saturates surfaces but also resides within the near-surface region of Pd nanoparticles. Ex situ X-ray photoelectron spectroscopy indicates that Br*-atoms withdraw charge from Pd atoms and yield greater fractions of Pd2+. Comparisons among infrared spectra of adsorbed CO imply that persistent Br atoms preferentially bind to undercoordinated sites. H2O2 and H2O formation rates, both in the presence and absence of Br*-atoms, change with H2 and O2 pressures in ways consistent with elementary steps that involve H2O-mediated proton-electron transfer (PET). Therefore, increased selectivities on Br*-modified surfaces reflect differences in apparent activation enthalpies for H2O2 ( Δ H ‡ H 2 O 2 ) and H2O ( Δ H ‡ H 2 O ) formation. Δ H ‡ H 2 O 2 and Δ H ‡ H 2 O increase systematically with [NaBr], although with different sensitivities. Comparisons of activation enthalpies alongside ex situ characterization provide compelling evidence that Br atoms adsorb onto and intercalate beneath the surfaces of Pd nanoparticles and increase steady-state H2O2 selectivities, which persist without further addition of liquid-phase bromide for at least 15 h. These findings indicate H2O2 selectivities for a continuous catalytic process may be increased by a one-time (or infrequent) addition of halide promoters, which can reduce the complexity of subsequent product purification for many applications of H2O2.

SPI‐62 is a selective and potent small‐molecule inhibitor of 11β‐hydroxysteroid dehydrogenase type 1 (HSD‐1). SPI‐62 has demonstrated substantial and complex nonlinear pharmacokinetics (PK) in humans that is characterized by unusually low plasma exposure at low doses, dose‐dependent volume of distribution, nonlinear PK following the first dose, and dose‐proportional PK at steady state, as well as unusually high accumulation ratios at low doses. The most likely explanation for the observed nonlinearity of SPI‐62 is the saturable binding of SPI‐62 to its pharmacological target HSD‐1, a phenomenon known as target‐mediated drug disposition (TMDD). Because of the nonlinear and complex PK of SPI‐62, the relationship among SPI‐62 dose, exposure, and response is no longer intuitive and consequently dose selection can be challenging. To facilitate dose selection and clinical trial design, in the current study population PK analysis was performed to characterize SPI‐62 dose‐exposure relationship in humans quantitatively. SPI‐62 PK was best characterized by a 2‐compartment TMDD model with 3 transit absorption compartments. The model was successfully established to explain the substantial and unusual nonlinear PK of SPI‐62 in humans, and it provided adequate fitting for both single‐ and multiple‐dose data. Our modeling work has provided a strong foundation for dose selection in future SPI‐62 clinical trials.

This paper reports about the production of syngas from dry reforming of ethanol (EDR) upon LaCuO3 and CeCuO3 catalysts that were prepared by using citrate sol-gel method. EDRs were run with fresh catalyst at each varied variable and 42 L/gcat/h of feed in a tubular reactor under atmospheric pressure. At equal feed pressure of reactants, steady state CO2 conversion increased exponentially from 700 to 800 °C while H2 and CO yields were increasing differently in sigmoid trend rendering H2/CO ratios to drop linearly from 1.7 to 1.0. However, these reaction results except the latter are otherwise when ethanol-CO2 ratio was increased (reducing CO2 pressure) at 750 °C. A minimum H2/CO ratio was evidenced at the ethanol-CO2 ratio of 1.48. LaCuO3 catalyst was more superior in producing syngas owing to its relatively low reduction temperature, high surface area and crystallinity, many active sites, good surface morphology and many C–O, C–H and hydroxyl groups.

Anaerobic digestion (AD) is a sustainable technology that combines biogas production with proper waste management. However, the operation of an anaerobic reactor under the stress of nanoparticles (NPs) is unknown. Therefore, this study assessed the disadvantages and advantages of adding two NPs to 11 L semi-continuous stirred-biodigesters and examined their contributions to biogas generation. Iron oxide NPs (INPs) and titanium oxide NPs (TNPs) were mixed daily with manure from dairy cattle and added to the biodigesters daily at concentrations of 100 mg/L (D1) and 500 mg/L (D2), respectively. In addition, a control with no NP supplementation was studied (D0). The results revealed that the generation rates of biogas and CH4 increased by 25.43 and 62.43%, respectively, for D1 during the first 7-day retention time, as compared with the D0. Conversely, TNP addition reduced the generation rates by 28.76 and 56.92%, respectively, during the same period. Overall, for D1, the biogas and CH4 yields over the study period increased by 5.48 and 12.35%, respectively, whereas for D2, the rates were reduced by 11.36 and 18.58%, respectively. Therefore, the presence of INPs had a stimulatory influence while that of the TNPs had an inhibitory effect.

Silsesquioxane-based materials are garnering considerable attention due to their unique structural and electronic properties which enable use in diverse fields of study. In this article, we investigate a series of hybrid oligomeric materials comprising a silsesquioxane (SQ) backbone linked by conjugated organic cross-linkers and assess their photophysical properties in the steady state absorption and emission realms. Silsesquioxanes improve the thermal and photo stabilities of the organic components, offer enhancements in the molar extinction coefficients of absorption, and have a significant influence on their emission properties. We used Heck cross-coupling reactions to build oligomers with a vinyl/phenylSQ cage backbone linked with a series of different cross-linkers including 2,7-dibromo-9-fluorenone, 2,7-dibromo-9,9-dimethylfluorene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-dibromopyridine, 2,6-dibromopyridine, 2,3-dibromothiophene, 2,5-dibromothiophene, and 2,5- dibromothieno [3,2-b]thiophene. Each of these linkers showed reasonable conversion to oligomers and exhibited a wide array of fluorescence quantum yield and shifts in the absorption and emission spectra dependent on the variations in substitution position. We confined the study to explore the overall steady state spectral properties of these synthesized hybrid materials in their solution phases. Understanding the basic photophysical processes in these materials will pave the way towards their use in photovoltaic or electroluminescence applications.

While photoredox catalysis continues to transform modern synthetic chemistry, detailed mechanistic studies involving direct observation of reaction intermediates and rate constants are rare. By use of a combination of steady state photochemical measurements, transient laser spectroscopy, and electrochemical methods, an α-aminoarylation mechanism that is the inspiration for a large number of photoredox reactions was rigorously characterized. Despite high product yields, the external quantum yield (QY) of the reaction remained low (15-30%). By use of transient absorption spectroscopy, productive and unproductive reaction pathways were identified and rate constants assigned to develop a comprehensive mechanistic picture of the reaction. The role of the cyanoarene, 1,4-dicyanobenzne, was found to be unexpectedly complex, functioning both as initial proton acceptor in the reaction and as a neutral stabilizer for the 1,4-dicyanobenzene radical anion. Finally, kinetic modeling was utilized to analyze the reaction at an unprecedented level of understanding. This modeling demonstrated that the reaction is limited not by the kinetics of the individual steps but instead by scattering losses and parasitic absorption by a photochemically inactive donor-acceptor complex.

The purpose of the present study was to evaluate de influence of protein–sugar complexation on the stability and functionality of C-reactive protein, after exposure to constant high temperatures, in order to develop highly stable positive controls for in-vitro diagnostic tests. C-reactive protein is a plasmatic protein used as a biomarker for the diagnosis of a series of health problems such as ulcerative colitis, cardiovascular diseases, metabolic syndrome, due to its essential role in the evolution of chronic inflammation. The sugar–protein interaction was investigated using steady state and time resolved fluorescence. The results revealed that there are more than two classes of tryptophan, with different degree of accessibility for the quencher molecule. Our study also revealed that sugar–protein complexes have superior thermostability, especially after gamma irradiation at 2 kGy, the protein being stable and functional even after 22 days exposure to 40 °C.

Understanding of the plant uptake of ionizable organic compounds is critical to the evaluation of crop contamination, plant protection, and phytoremediation. This study investigated the time-dependent uptake of 2,4-dichlorophenol (DCP) by intact wheat seedling roots and subsequent translocation to shoots at pH 5.0 and 8.0. Sorption of DCP by cut roots and shoots at these two pHs was conducted to provide the uptake limits and the Donnan charge. For comparison, sorption was also conducted for 1,3-dichlorobenzene (DCB), a nonionizable compound having a structure similar to that of DCP. The DCB sorption isotherms were linear and independent of pH, yielding a consistent log Klip of 3.56 with both roots and shoots, reflective of the essential dominant role of lipids in plant partition uptake. Whereas the DCP sorption also showed a linear isotherm at pH 5.0 with log Klip = 2.88, the sorption at pH 8.0 was nonlinear with a concave downward shape, especially at low concentrations. With live wheat seedlings, the DCB uptake by roots and the DCB translocation to shoots rapidly approached a steady state, showing no obvious pH effect. On the DCP uptake by live plants, there was a rapid attainment of a steady state in roots at pH 5.0 coupled with a retarded transport to shoots due presumably to the polarity of DCP. At pH 8.0, the root uptake of DCP was comparatively slower and the translocation to shoots was completely inhibited due presumably to DCP ionization. At high pH, DCP was supposedly accumulated in an ionized form in root cells via an ion-trapping mechanism.

Proton-coupled electron transfer (PCET) is a fundamental step in a wide range of electrochemical processes, including those of interest in energy conversion and storage. Despite its importance, several mechanistic details of such reactions remain unclear. Here, we have combined a proton donor (tertiary ammonium) with a vibrational Stark-shift probe (benzonitrile), to track the process from the entry of the reactants into the electrical double layer (EDL), to the PCET reaction associated with proton donation to the electrode, and the formation of products. We have used operando vibrational spectroscopy and periodic density functional theory under electrochemical bias to assign the reactant and product peaks and their Stark shifts. We have identified three main stages for the progress of the PCET reaction as a function of applied potential. First, we have determined the potential necessary for desolvation of the reactants and their entry into the polarizing environment of the EDL. Second, we have observed the appearance of product peaks prior to the onset of steady state electrochemical current, indicating formation of a stationary population of products that does not turn over. Finally, more negative of the onset potential, the electrode attracts additional reactants, displacing the stationary products and enabling steady state current. This work shows that the integration of a vibrational Stark-shift probe with a proton donor provides critical insight into the interplay between interfacial electrostatics and heterogeneous chemical reactions. Such insights cannot be obtained from electrochemical measurements alone.

Patients with primary immunodeficiency diseases often require lifelong immunoglobulin (IG) therapy. Most clinical trials investigating IG therapies characterize serum immunoglobulin G (IgG) pharmacokinetic (PK) profiles by serially assessing serum IgG levels. This retrospective analysis evaluated whether steady-state serum IgG trough level measurement alone is adequate for PK assessment. Based on individual patient serum IgG trough levels from two pivotal trials (phase 2/3 European [NCT01412385] and North American [NCT01218438]) of weekly 20% subcutaneous IG (SCIG; Cuvitru, Ig20Gly), trough level-predicted IgG AUC (AUCτ,tp) were calculated and compared with the reported AUC calculated from serum IgG concentration-time profiles (AUCτ). In both studies, mean AUCτ,tpvalues for Ig20Gly were essentially equivalent to AUCτwith point estimates of geometric mean ratio (GMR) of AUCτ,tp/AUCτnear 1.0 and 90% CIs within 0.80–1.25. In contrast, for IVIG, 10%, mean AUCτ,tpvalues were lower than AUCτby >20%, (GMR [90% CI]: 0.74 [0.70–0.78] and 0.77 [0.73–0.81] for the two studies, respectively). Mean AUCτ,tpvalues calculated for 4 other SCIG products (based on mean IgG trough levels reported in the literature/labels) were also essentially equivalent to the reported AUCτ(differences 20%. In conclusion, steady-state serum IgG levels following weekly SCIG remain stable, allowing for reliable prediction of AUC over the dosing interval using trough IgG levels. These findings indicate that measuring steady-state serum IgG trough levels alone may be adequate for PK assessment of weekly SCIG.

Immune-based metabolic reprogramming of arginine utilization in the brain contributes to the neuronal pathology associated with Alzheimer's disease (AD). To enable our long-term goals of differentiation of AD mouse model genotypes, ages, and sexes based on activity of this pathway, we describe here the novel dosing (using uniformly labeled (13C615N4) arginine) and analysis methods using capillary electrophoresis high-resolution accurate-mass mass spectrometry for isotope tracing of metabolic products of arginine. We developed a pseudoprimed infusion-dosing regimen, using repeated injections, to achieve a steady state of uniformly labeled arginine in 135-195 min post bolus dose. Incorporation of stable isotope labeled carbon and nitrogen from uniformly labeled arginine into a host of downstream metabolites was measured in vivo in mice using serially sampled dried blood spots from the tail. In addition to the dried blood spot time course samples, total isotope incorporation into arginine-related metabolites was measured in the whole brain and plasma after 285 min. Preliminary demonstration of the technique identified differences isotope incorporation in arginine metabolites between male and female mice in a mouse-model of sporadic Alzheimer's disease (APOE4/huNOS2). The technique described herein will permit arginine pathway activity differentiation between mouse genotypes, ages, sexes, or drug treatments in order to elucidate the contribution of this pathway to Alzheimer's disease.

Here, we present a conceptual and quantitative model to describe the role of the Cytochrome $$\hbox {b}_{6}\hbox {f}$$ b 6 f complex in controlling steady-state electron transport in $$\hbox {C}_{3}$$ C 3 leaves. The model is based on new experimental methods to diagnose the maximum activity of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f in vivo, and to identify conditions under which photosynthetic control of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f is active or relaxed. With these approaches, we demonstrate that Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f controls the trade-off between the speed and efficiency of electron transport under limiting light, and functions as a metabolic switch that transfers control to carbon metabolism under saturating light. We also present evidence that the onset of photosynthetic control of Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f occurs within milliseconds of exposure to saturating light, much more quickly than the induction of non-photochemical quenching. We propose that photosynthetic control is the primary means of photoprotection and functions to manage excitation pressure, whereas non-photochemical quenching functions to manage excitation balance. We use these findings to extend the Farquhar et al. (Planta 149:78–90, 1980) model of $$\hbox {C}_{3}$$ C 3 photosynthesis to include a mechanistic description of the electron transport system. This framework relates the light captured by PS I and PS II to the energy and mass fluxes linking the photoacts with Cyt $$\hbox {b}_{6}\hbox {f}$$ b 6 f , the ATP synthase, and Rubisco. It enables quantitative interpretation of pulse-amplitude modulated fluorometry and gas-exchange measurements, providing a new basis for analyzing how the electron transport system coordinates the supply of Fd, NADPH, and ATP with the dynamic demands of carbon metabolism, how efficient use of light is achieved under limiting light, and how photoprotection is achieved under saturating light. The model is designed to support forward as well as inverse applications. It can either be used in a stand-alone mode at the leaf-level or coupled to other models that resolve finer-scale or coarser-scale phenomena.

Steady-state enzyme kinetics is a cornerstone technique of biochemistry and related sciences since it allows the characterization and quantification of enzyme behaviour. Enzyme kinetics is widely used to investigate the physiological role of enzymes, determine the effects of mutations and characterize enzyme inhibitors. Well-known examples of enzyme inhibitors used to treat diseases include anti-infectives (e.g., penicillin, clavulanic acid and HIV protease inhibitors); anti-inflammatories (e.g., aspirin and ibuprofen); cholesterol-lowering statins; tyrosine kinase inhibitors used to treat cancer; and Viagra. Commonly, new disease treatments are discovered by using enzyme kinetics to identify the few active compounds residing within a large compound collection (‘high-throughput screening’). The subject of enzyme kinetics is typically introduced to first-year undergraduates with a mathematical description of behaviour. This Beginners Guide will give a brief overview of experimental enzyme kinetics and the characterization of enzyme inhibitors. Colorimetric assays using a microtitre plate will be considered, although most principles also apply to other assays.

Numerous volatile organic compounds and odors are generated when municipal solid wastes decompose in landfill sites. Three biofilters (BF-1, BF-2, and BF-3) were deployed to remove H2S and NH3 accumulated under high density polyethylene films in a 30,000 m2 area landfill site in North China. Results showed that the inlet concentrations of H2S and NH3 were 16.4–220.3 mg/m3 and 2.0–56.4 mg/m3, respectively. Outlet concentrations were reduced to 1.0–33.1 mg/m3 for H2S and 0–9.2 mg/m3 for NH3. The H2S removal efficiencies were around 91.1 % for BF-1, 87.0 % for BF-2, and 82.6 % for BF-3 in a steady state. The respective removals of NH3 were 92.0 %, 89.3 %, and 81.1 %. Thus, H2S and NH3 were both treated effectively by the biofilters. The intake load presented a seasonal variation. A high elimination capacity was obtained in the biofilter harvesting high inlet load. High throughput sequencing technology was utilized to assay the microbial populations in the biofilters. Pseudomonas sp., Alicyclobacillus sp., Sphingomonas sp., and Rhodanobacter sp, which were linked to the degradation of H2S and NH3, were isolated and identified. Their characteristics and distributions in the biofilters depended on the inlet concentration of substrates and the microenvironment within the packing materials. The results from this bio-product analysis indicated that most of H2S was bio-oxidized into sulfur and sulfate while NH3 was converted into nitrate or dissolved into the liquid phase mainly by absorption or chemical neutralization in the biofilters.

Aim: To assess the pharmacokinetics of once-daily oral lenvatinib 24 mg in Chinese patients. Material & methods: Patients had any solid tumor (except hepatocellular carcinoma) that was resistant to standard antitumor therapies or for which no appropriate treatment was available. Results: Twelve patients were enrolled. Maximum plasma concentrations of lenvatinib were observed at 2 and 4 h (median) after single and multiple doses (day 15), respectively. Steady state was achieved within 8 days. The geometric mean maximum observed concentration at steady state was 258 ng/ml (coefficient of variance: 49.2%); and the geometric mean area under the concentration–time curve from zero to 24 h at steady state was 3090 ng•h/ml (coefficient of variance: 44.7%). No accumulation was seen after 15 days. Conclusion: Lenvatinib pharmacokinetic data in Chinese patients are consistent with data in multinational trials, supporting usage of the 24-mg dose. Clinical trial registration: NCT03009292 (ClinicalTrials.gov)

Deoxythymidine triphosphate analogs with various 3′ sugar groups (-OH (dTTP), -H, -N3, -NH2, -F, -O-CH3, no group (2′,3′-didehydro-2′,3′-dideoxythymidine triphosphate (d4TTP)), and those retaining the 3′-OH but with 4′ additions (4′-C-methyl, 4′-C-ethyl) or sugar ring modifications (D-carba dTTP) were evaluated using pre-steady-state kinetics in low (0.5 mM) and high (6 mM) Mg2+ with HIV reverse transcriptase (RT). Analogs showed diminished incorporation rates (k) compared to dTTP ranging from about 2-fold (3′-H, -N3, and d4TTP with high Mg2+) to >10-fold (3′-NH2 and 3′-F with low Mg2+), while 3′-O-CH3 dTTP incorporated much slower than other analogs. Illustrating the importance of interactions between Mg2+ and the 3′-OH, k using 5 μM dTTP and 0.5 mM Mg2+ was only modestly slower (1.6-fold) than with 6 mM Mg2+, while analogs with 3′ alterations incorporated 2.8-5.1-fold slower in 0.5 mM Mg2+. In contrast, 4′-C-methyl and D-carb dTTP, which retain the 3′-OH, were not significantly affected by Mg2+. Consistent with these results, analogs with 3′ modifications were better inhibitors in 6 mM vs. 0.5 mM Mg2+. Equilibrium dissociation constant (Kd) and kpol determinations for dTTP and analogs lacking a 3′-OH indicated that low Mg2+ caused a several-fold greater reduction in kpol with the analogs but had little effect on Kd, results consistent with a role for 3′-OH/Mg2+ interactions in catalysis rather than nucleotide binding. Overall, results emphasize the importance previously unreported interactions between Mg2+ and the 3′-OH of the incoming nucleotide and suggest inhibitors with 3′-OH groups may have advantages in the low free Mg2+ in physiological settings.

The roles of nitrate and nitrite ions as nitric oxide (NO) sources in mammals, complementing NOS enzymes, have recently been the focus of much research. We previously reported that rat skeletal muscle serves as a nitrate reservoir, with the amount of stored nitrate being highly dependent on dietary nitrate availability, as well as its synthesis by NOS1 enzymes and its subsequent utilization. We showed that at conditions of increased NO need, this nitrate reservoir is used in situ to generate nitrite and NO, at least in part via the nitrate reductase activity of xanthine oxidoreductase (XOR). We now further investigate the dynamics of nitrate/nitrite fluxes in rat skeletal muscle after first increasing nitrate levels in drinking water and then returning to the original intake level. Nitrate/nitrite levels were analyzed in liver, blood and several skeletal muscle samples, and expression of proteins involved in nitrate metabolism and transport were also measured. Increased nitrate supply elevated nitrate and nitrite levels in all measured tissues. Surprisingly, after high nitrate diet termination, levels of both ions in liver and all muscle samples first declined to lower levels than the original baseline. During the course of the overall experiment there was a gradual increase of XOR expression in muscle tissue, which likely led to enhanced nitrate to nitrite reduction. We also noted differences in basal levels of nitrate in the different types of muscles. These findings suggest complex control of muscle nitrate levels, perhaps with multiple processes to preserve its intracellular levels.

The aim of this work was to study the homogeneous oxidation process of Fenton for the decolorization of methyl orange (MO) using experimental design methodology. The efficiency of this process was evaluated according to the effect of each of the most influential parameters such as concentrations of Fe2+, H2O2, MO and the pH, also their combined effects using three responses: the decolorization yield (R), the amount of dye removed per gram of catalyst (Q) and the time required to reach steady state (tss). The ANOVA showed that about 99% of the variations in R and Q responses and 92% of the tss response could be explained by these linear models with interactions. To ensure maximum yield of MO degradation (100%) with minimum residence time (less than 1 min) in the batch reactor, the Fenton process should be carried out in MO diluted medium ([MO] = 2 mg/L) and under the following optimal conditions: [H2O2] = 3.53 mM, [Fe2+] = 0.067 g/L and pH 2. These conditions were verified experimentally, enabling these three regression equations to be used for modeling the Fenton process and predicting future responses.

In this study, the effect of natural zeolite on the ammonium ion removal from landfill fresh leachate (LFL) was investigated. The effect of different parameters such as pH, contact time (CT) and zeolite concentration (ZC) in a batch system were studied to optimize ammonium ion removal from LFL by natural zeolite. Firstly, the effect of variable pH values (5–9) was investigated. In the next step, at the optimal pH condition (7), the effect of ZCs of 10–200 g/L was studied. It is indicated that, from 10 up to 80 g/L, the amount of ammonium ion removed is increased. Meanwhile, increasing of the ZC from 80 until 200 g/L resulted in decreasing removal efficiency. Finally, in the previous optimal conditions, the role of CTs (5–300 min) is inspected. With increasing CT from 5 up to 30 min the amount of removal rate was increased. Following with increasing CT, the intensity of the uptrend decreased and the removal rate reached a steady state. Results of the experiments indicate optimal conditions for ammonium ion removal from LFL (44.49%) occur at pH, 7, ZC of 80 g/L and CT of 30 min. In addition, the adsorption isotherm and kinetics confirmed that the Langmuir isotherm (R2 = 0.9451) was more consistent than the Freundlich isotherm (R2 = 0.9211). This study indicates that clinoptilolite zeolite (CZ) as an inexpensive and suitable adsorbent, has a good potential for removing ammonium ions from LFL solution.

Fat from Capra hircus (goat fat) has been widely used for drug delivery. In this work, 1:1, 1:2, and 2:1 of goat fat and Softisan® 142 were melted together, cooled at room temperature, and the resultant matrix further modified with Phospholipon 90G (4:1) to obtain solidified reverse micellar solutions (SRMS). SRMS were used to prepare solid lipid microparticles (SLMs) loaded with or without glibenclamide, a poorly water soluble antidiabetic drug by hot melt homogenization. Particle size, morphology, thermal behavior, drug encapsulation efficiency, in vitro release study, and in vivo fate in diabetogenic rats were investigated. We report here an improved drug holding capacity (70.35%) of the lipid matrix of SRMS 2:1 due to imperfection of the lipid mixtures showing lower transition temperatures (117.0 °C) and enthalpies (−12.5 mW/mg). In vitro drug diffusion showed 66.98% drug release from SLM 2:1 exhibiting non-Fickian diffusion model (anomalous behavior) and almost zero-order kinetic. SLM 2:1 also gradually released 56.98% of glibenclamide under 16 h and maintained a steady state till 24 h; generally lowering blood glucose from 600 to 120 mg/dL unlike SLM 1:2 which showed burst glibenclamide release of 22.66% within 30 min with consequent rise in blood sugar. The 2:1 micellar solution (SRMS) of homolipids could deliver glibenclamide in a sustained form better than the conventional tablet form.

This study aims to investigate the effect of substrate concentration and hydraulic retention time (HRT) on hydrogen production in a continuous anaerobic bioreactor from unhydrolyzed common reed (Phragmites australis) an invasive wetland and perennial grass. The bioreactor has capacity of 1 L and working volume of 600 mL. It was operated at pH 5.5, temperature at 37 °C, hydraulic retention time (HRT) 12 h, and variation of substrate concentration from 40, 50, and 60 g COD/L, respectively. Afterward, the HRT was then varied from 12, 8, to 4 h for checking the optimal biohydrogen production. Each condition was run until reach steady state on hydrogen production rate (HPR) which based on hydrogen percentage and daily volume. The results were obtained the peak of substrate concentration was at the 50 g COD/L with HRT 12 h, average HPR and H2 concentration were 28.71 mL/L/h and 36.29%, respectively. The hydrogen yield was achieved at 106.23 mL H2/g CODre. The substrate concentration was controlled at 50 g COD/L for the optimal HRT experiments. It was found that the maximum of average HPR and H2 concentration were 43.28 mL/L/h and 36.96%, respectively peak at HRT 8 h with the corresponding hydrogen yield of 144.35 mL H2/g CODre. Finally, this study successful produce hydrogen from unhydrolyzed common reed by enriched mixed culture in continuous anaerobic bioreactor.

Earlier studies developed a steady-state model to predict the brightness and/or bleach consumption during the chlorine dioxide brightening (D1) of softwood pulps produced by conventional elemental-chlorine-free (ECF) sequences. This model relates the chlorine dioxide consumed to the brightness gains predicated upon an asymptotic D1 brightness limit, an incoming D1 pulp brightness, and an equation parameter (β11). The current investigation examines the application of this model to ECF sequences that use ozone delignification (Z-ECF). Literature D1 data from various Z-ECF bleaching studies, which investigated OZ, OD0/Z, and OZ/D0 delignification, were fitted to the model. The β11 parameter was found to be linearly correlated to the entering kappa number. Interestingly, this linear relationship was found to be identical to the relationships observed when modeling the D1 stage for conventional ECF and chlorine-based bleach sequences. Subtle differences in D1 brightening response in the model among the various bleach sequences are reflected by incoming pulp brightness (at the same kappa number). The current model is used to illustrate how alterations to Z-ECF delignification affect D1 brightening and chlorine dioxide consumption.

During photosynthesis, energy is transiently stored as an electrochemical proton gradient across the thylakoid membrane. The resulting proton motive force (pmf) is composed of a membrane potential (ΔΨ) and a proton concentration gradient (ΔpH) and powers the synthesis of ATP. Light energy availability for photosynthesis can change very rapidly and frequently in nature. Thylakoid ion transport proteins buffer the effects that light fluctuations have on photosynthesis by adjusting pmf and its composition. Ion channel activities dissipate ΔΨ, thereby reducing charge recombinations within photosystem II. The dissipation of ΔΨ allows for increased accumulation of protons in the thylakoid lumen, generating the signal that activates feedback downregulation of photosynthesis. Proton export from the lumen via the thylakoid K+ exchange antiporter 3 (KEA3), instead, decreases the ΔpH fraction of the pmf and thereby reduces the regulatory feedback signal. Here, we reveal that the Arabidopsis (Arabidopsis thaliana) KEA3 protein homo-dimerizes via its C-terminal domain. This C-terminus has a regulatory function, which responds to light intensity transients. Plants carrying a C-terminus-less KEA3 variant show reduced feed-back downregulation of photosynthesis and suffer from increased photosystem damage under long-term high light stress. However, during photosynthetic induction in high light, KEA3 deregulation leads to an increase in carbon fixation rates. Together, the data reveal a trade-off between long-term photoprotection and a short-term boost in carbon fixation rates, which is under the control of the KEA3 C-terminus., The regulatory C-terminus of the thylakoid Kexchange antiporter 3 (KEA3) is required for mitigating high light stress and protein dimerization.

Ultrasmall nanoparticles (US-NPs

This study aims to extend, the recently developed, heat polynomial based modified method of fundamental (MFS) solutions to a steady state anisotropic problem. We successfully extend the method to t...

The cell culture is the central piece of a biotechnological industrial process. It includes upstream (e.g. media preparation, fixed costs, etc.) and downstream steps (e.g. product purification, waste disposal, etc.). In the continuous mode of cell culture, a constant flow of fresh media replaces culture fluid until the system reaches a steady state. This steady state is the standard operation mode which, under very general conditions, is a function of the ratio between the cell density and the dilution rate and depends on the media supplied to the culture. To optimize the production process it is widely accepted that the concentration of the metabolites in this media should be carefully tuned. A poor media may not provide enough nutrients to the culture, while a media too rich in nutrients may be a waste of resources because, either the cells do not use all of the available nutrients, or worse, they over-consume them producing toxic byproducts. In this work, we show how an in-silico study of a genome scale metabolic network coupled to the dynamics of a chemostat could guide the strategy to optimize the media to be used in a continuous process. Given a known media we model the concentrations of the cells in a chemostat as a function of the dilution rate. Then, we cast the problem of optimizing the production process within a linear programming framework in which the goal is to minimize the cost of the media keeping fixed the cell concentration for a given dilution rate in the chemostat. We evaluate our results in two metabolic models: first a simplified model of mammalian cell metabolism, and then in a realistic genome-scale metabolic network of mammalian cells, the Chinese Hamster Ovary (CHO) cell line. We explore the latter in more detail given specific meaning to the predictions of the concentrations of several metabolites. This article is protected by copyright. All rights reserved.

The control of nutrient availability is critical to large-scale manufacturing of biotherapeutics. However, the quantification of proteinogenic amino acids is time-consuming and thus is difficult to implement for real-time in situ bioprocess control. Genome-scale metabolic models describe the metabolic conversion from media nutrients to proliferation and recombinant protein production, and therefore are a promising platform for in silico monitoring and prediction of amino acid concentrations. This potential has not been realized due to unresolved challenges: (1) the models assume an optimal and highly efficient metabolism, and therefore tend to underestimate amino acid consumption, and (2) the models assume a steady state, and therefore have a short forecast range. We address these challenges by integrating machine learning with the metabolic models. Through this we demonstrate accurate and time-course dependent prediction of individual amino acid concentration in culture medium throughout the production process. Thus, these models can be deployed to control nutrient feeding to avoid premature nutrient depletion or provide early predictions of failed bioreactor runs.

The kinetics of higher alcohol synthesis was investigated using a hydrotalcite-derived Co-Cu-based catalyst aiming at a deeper understanding of the complex reaction network. At steady state similar chain growth probabilities of about 0.4 according to the Anderson-Schulz-Flory distribution were observed for alcohols, hydrocarbons and olefins indicating common intermediates. Alkanes were found to be formed consecutively from primarily formed olefins. The observed decrease of the selectivities to alcohols with increasing CO conversion at higher temperatures and higher residence times is ascribed to an increased availability of adsorbed atomic hydrogen, which decreases the saturated coverage of CO-derived CxHyOz species favoring hydrocarbon formation. Correspondingly, reaction orders of 0 and 0.8 for CO and H2, respectively, were derived based on a power-law approach including an apparent activation energy of 140 kJ mol−1. A reaction network based on the CO insertion factor was established, in which the competing reactions β-hydrogen elimination, chain growth and CO insertion proceed from common adsorbed CxHy intermediates. Selective higher alcohol formation was favored at low temperatures and short residence times, high pressures and a moderate H2:CO ratio of 1 requiring a compromise between conversion and selectivity.