Methane storage in homogeneous armchair open-ended single-walled boron nitride nanotube triangular arrays: a grand canonical Monte Carlo simulation study

The physisorption of methane in homogeneous armchair open-ended SWBNNT triangular arrays was evaluated using grand canonical ensemble Monte Carlo simulation for tubes 11.08, 13.85, 16.62, and 19.41 ? [(8,8), (10,10), (12,12), and (14,14), respectively] in diameter, at temperatures of 273, 298, 323, and 373 K, and at fugacities of 0.5-9.0 Mpa. The intermolecular forces were modeled using the Lennard-Jones potential model. The absolute, excess, and delivery adsorption isotherms of methane were calculated for the various boron nitride nanotube arrays. The specific surface areas and the isosteric heats of adsorption, Q(st), were also studied, different isotherm models were fitted to the simulated adsorption data, and the model parameters were correlated. According to the results, it is possible to reach 108% and 140% of the US Department of Energy's target for CH(4) storage (180 v/v at 298 K and 35 bar) using the SWBNNT array with nanotubes 16.62 and 19.41 ? in diameter, respectively, as adsorbent. The results show that for a van der Waals gap of 3.4 ?, there is no interstitial adsorption except for arrays containing nanotubes with diameters of >15.8 ?. Multilayer adsorption starts to occur in arrays containing nanotubes with diameters of >16.62 ?, and the minimum pressure required for multilayer adsorption is 1.0 MPa. A brief comparison of the methane adsorption capacities of single-walled carbon and boron nitride nanotube arrays was also performed.     

Material strategies for creating artificial cell-instructive niches

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Highlights? Biomaterial selection based on origin, biodegradability, and microstructure. ? Bulk and surface biochemical modification of scaffolds for presentation of cytokines. ? Designing scaffolds with in vivo-like mechanical properties and topography. ? Use of microfluidics to replicate dynamic mechanical and biochemical parameters.     

Computational insights into pH-dependence of structure and dynamics of pyrazinamidase: A comparison of wild type and mutants

The mycobacterial enzyme pyrazinamidase (PZase) is the target of key tuberculosis drug, pyrazinamide. Mutations in PZase cause drug resistance. Herein, three point mutations, W68G, L85P, and V155G, were investigated through over 8 µs of molecular dynamics simulations coupled with essential dynamics and binding pocket analysis at neutral (pH = 7) and acidic (pH = 4) ambient conditions. The 51-71 flap region exhibited drastic displacement leading to enlargement of binding cavity, especially at the lower pH. Accessibility of solvent to the active site of the mutant enzymes was also reduced. The protonation of key surface residues at low pH results in more contribution of these residues to structural stability and integrity of the enzyme and reduced interactions with solvent molecules, which acts as a cage, keeping the enzyme together. The observed results suggest a pattern of structural alterations due to point mutations in PZase, which is consistent with other experimental and theoretical investigations and, can be harnessed for drug design purposes.     

Mapping QTLs for physiological and biochemical traits related to grain yield under control and terminal heat stress conditions in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

In order to detect genomic regions with different effects for some of the physiological and biochemical traits of wheat, four experiments were conducted at Research Farm of Agricultural and Natural Resources Research Center of Zabol in 2015–2016 and 2016–2017 growing seasons. The experiments were carried out using four alpha lattice designs with two replications under non-stress and terminal heat stress conditions. Plant materials used in this study included 167 recombinant inbred lines and their parents (‘SeriM82’ and ‘Babax’). Six traits including grain yield (GY), proline content (PRO), water soluble carbohydrates (WSC), maximum efficiency of photosystem II (Fv/Fm), cytoplasmic membrane stability (CMS) and chlorophyll content (CHL) were evaluated. Genetic linkage map consisted of 211 AFLP marker, 120 SSR marker and 144 DArT markers with 1864 cm length and 4.4 cm mean distance. QTL analysis was carried out using a mixed-model-based composite interval mapping (MCIM) method. By the combined analysis of normal phenotypic values, 27 additive QTLs and five pairs of epistatic effects were identified for studied traits, among which two additive and one epistatic QTL showed significant QTL?×?environment interactions. By the combined analysis of stress phenotypic values, a total of 26 QTLs with additive effects and 5 epistatic QTLs were detected, among which one additive and one epistatic QTL showed QTL?×?environment interactions. Six QTLs with major effects (QGY-2B, QGY-2D, QPro-5B, QWSC-4A, QFv/Fm-6A and QCMS-4B), which were common between two conditions could be useful for marker-assisted selection (MAS) in order to develop heat tolerant and high-performance wheat varieties.     

Carbon Quantum Dots as Multi-Purpose Nanomaterial in Stem Cell Therapy

During stem cell therapy, some issues, such as obscure fate of stem cells or their low survival rate in the body, should be addressed to boost their therapeutic efficiency. Nanotechnology offers a suitable solution to combat such limitations. Carbon quantum dots (CQDs) are carbon-based nanomaterials and may be used as multi-purpose compounds in stem cell therapy. CQDs are excellent choices for stem cell labeling thanks to their special features such as optical properties and good biocompatibility. Besides, they can modulate the biological function of stem cells, such as their proliferation, homing ability, and differentiation properties. Considering the charismatic feature of CQDs and their broad unique effect on stem cells, the current review aims to summarize the most advancements in this field. Hence, we first focused on CQDs synthesis and their applications. In the next section, the stem cell categories will be discussed, and the final part is dedicated to the recent research evaluating the impact of CQDs on stem cell therapy.     

Endothelin-1 increases collagen accumulation in renal mesangial cells by stimulating a chemokine and cytokine autocrine signaling loop

Endothelin-1 (ET-1), a potent vasoconstrictor, has been implicated in the pathogenesis of collagen accumulation, extracellular matrix remodeling, and renal and cardiac fibrosis in diabetes. However, the mechanism by which ET-1 promotes collagen accumulation remains unclear. Here, we analyzed the gene expression profile of ET-1-stimulated mesangial cells to identify determinants of collagen accumulation. In human mesangial cells (a microvascular pericyte that secretes excess collagen in diabetic glomerulosclerosis), ET-1 increased mRNA and protein for MCP-1 (macrophage chemoattractant protein-1) and IL-6. ET-1-induced MCP-1 and IL-6 mRNAs and proteins were blocked by an ET(A) (but not ET(B)) receptor antagonist. ET-1/ET(A) receptor signaling evoked a 7.4-fold increase in collagen accumulation. Exogenous addition of either recombinant MCP-1 or IL-6 increased collagen accumulation by 3.5-fold. Co-stimulation with both MCP-1 and IL-6 did not elevate collagen accumulation further. Neither an MCP-1-neutralizing antibody nor an MCP-1 receptor antagonist inhibited ET-1-induced collagen accumulation. Similarly, neutralizing antibodies against IL-6 or the gp130 subunit of the IL-6 receptor did not attenuate ET-1-induced collagen accumulation. However, co-incubation with MCP-1- and IL-6-neutralizing antibodies inhibited ET-1-induced collagen accumulation by 52%, suggesting a robust autocrine loop wherein MCP-1 and IL-6 are redundant. Taken together, these results demonstrate that an autocrine signaling loop involving MCP-1 and IL-6 contributes to ET-1-induced collagen accumulation.     

Structural and dynamical studies of Humanin in water and TFE/water mixture: a molecular dynamics simulation

The structural and dynamical properties of Humanin, a small peptide with neuroprotective activity against the insults of the Alzheimer's disease-related genes and the neurotoxic amyloid peptide, are studied in two different environments by molecular dynamics simulation. In this study, we have performed comparative molecular dynamics simulations in the absence and in the presence of TFE. The resulting trajectories were analyzed in terms of structural and dynamical properties of peptide and compared to the available NMR data. In water humanin is observed to partly unfold. The peptide is readily stabilized in an ordered helical conformation in the TFE/water mixture. Our simulations show that the peptide is flexible with definite turn point in its structure in water environment. It is free to interact with receptors that mediate its action in polar environment. Humanin may also find an alpha helix structure necessary for passage through biomembranes and/or specific interactions.     

Diurnal variation in CREB phosphorylation and PER1 protein levels in lactotroph cells of melatonin-proficient C3H and melatonin-deficient C57BL mice: similarities and differences

The pineal hormone melatonin plays an important role in the maintenance of rhythmic functions of the hypophyseal pars tuberalis, which controls the lactotroph cells of the pars distalis. To analyze the effects of melatonin deficiency on the activity state of these cells, we have investigated the levels of Ser133-phosphorylated (p)CREB and PER1 protein in immunocytochemically identified lactotroph cells of melatonin-proficient C3H and melatonin-deficient C57BL mice at four different time points of a 12/12 LD cycle. At night, the percentage of lactotroph cells showing a positive nuclear pCREB and PER1 immunoreaction is significantly smaller in C57BL than in C3H mice. In both mouse strains, the percentage of pCREB-immunoreactive cells is minimal in the early morning and gradually increases to reach a maximum in the late night. PER1 levels show a parallel temporal variation in C3H, but in C57BL, they are drastically reduced in the early afternoon. The observation that, during darkness, the percentage of lactotroph cells with nuclear pCREB immunoreaction is significantly higher in C3H than in C57BL mice suggests the existence of a distinct cell population that is under the control of melatonin-dependent intrapituitary signaling. Interestingly, the percentage of pCREB- and PER1-immunoreactive lactotroph cells reaches minimal and maximal values at the same time points. This suggests that the correlation between CREB phosphorylation and PER1 induction differs between these cells and other neuroendocrine centers, e.g., the pineal organ and suprachiasmatic nucleus, displaying a temporal gap between CREB phosphorylation and PER1 induction.This study was supported by grants from the Deutsche Forschungsgemeinschaft (KO758/7-3)     

Using 2H2O to study the influence of feeding on protein synthesis: effect of isotope equilibration in vivo vs. in cell culture

We previously reported that 2H2O can be used to measure rates of protein synthesis during prolonged steady-state conditions (Previs SF, Fatica R, Chandramouli V, Alexander JC, Brunengraber H, and Landau BR. Am J Physiol Endocrinol Metab 286: E665-E672, 2004). The underlying premise of our method is that following the administration of 2H2O, 2H atoms in body water rapidly equilibrate with free alanine before it is incorporated into newly synthesized proteins. We have now directly examined whether 2H2O can be used to measure the influence of a single meal on protein synthesis. In addition, we have compared the use of 2H2O for measuring rates of protein synthesis in vivo vs. in cell culture. Using a rat model, we observed rapid equilibration between 2H in body water and free alanine; therefore we were able to study the response of protein synthesis to a single meal. We observed that approximately 50% of the plasma albumin that is synthesized over the course of 24 h is made within approximately 5 h after eating (in rats trained to eat a complete 24-h ration of food in a single meal). Contrary to what we observed in vivo, feeding (the replenishment of cell culture medium) does influence the use of 2H2O for in vitro studies. In particular, since there can be slow equilibration of 2H between water and alanine in the cell culture medium, special consideration must be made to avoid underestimating the rate of protein synthesis in vitro.