Search Results (270)

Molecular dynamics (MD) simulations have been performed on the energetics, mechanical properties, and irradiation response of seventy-three 3C-SiC symmetric tilt grain boundaries (STGBs) with three tilt axes (<100>, <110> and <111>). The effect of GB characteristics on the STGB properties has been investigated. The GB energy is positively and linearly correlated with the excess volume, but the linearity in SiC is not as good as in metals, which stems from the inhomogeneous structural relaxation near GBs induced by orientation-sensitive covalent bonding. For <110>STGBs, the shear strength exhibits symmetry with respect to the misorientation angle of 90°, which is consistent with ab initio calculations for Al in similar shear orientations. Cascades are performed with 8 keV silicon as the primary knock-on atom (PKA). No direct correlation is found between the sink efficiency of GBs for defects and GB characteristics, which comes from the complexity of the diatomic system during the recovery phase. For GBs with smaller values of Σ, the GBs exhibit a weaker blocking effect on the penetration of irradiated defects, resulting in a lower number of defects in GBs and a higher number of total surviving defects. In particular, it is seen that the percentage decrease in tensile strength after irradiation is positively correlated with the Σ value. Taken together, these results help to elucidate the impact of GB behavior on the mechanical properties of as well as the primary irradiation damage in SiC and provide a reference for creating improved materials through GB engineering. Full article

An important property of arylboronic acids, particularly when considering their use in medicinal chemistry, is their pK_a in aqueous solution. The results of computational determination of absolute pK_as of arylboronic acids can be very disappointing in comparison to available experimental results, particularly in the case of large substituents. In this paper, the main origin of this problem is identified. It is shown that in order to obtain accurate pK_a values for arylboronic acids from computational quantum chemistry, it is necessary to consider the effect of different possible conformations of the hydroxyl groups in the acid and its conjugate base together with the low-energy conformations of their substituents. An improved practical procedure for the computational determination of the pK_as of arylboronic acids is proposed and applied to a set of recently synthesized arylboronic acids, yielding consistent results. Full article

Incorporation of lanthanide (Ln) and actinide (An) ions into the human body poses significant chemotoxic and radiotoxic risks, necessitating effective decorporation strategies. This study investigates the displacement of biologically relevant ligands from trivalent ions of europium, Eu(III), and curium, Cm(III), in artificial biofluids by various complexing agents, i.e., ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), and spermine-based hydroxypyridonate chelator 3,4,3-LI(1,2-HOPO) (HOPO). Utilizing a modified unified bioaccessibility method (UBM) to simulate gastrointestinal conditions, we conducted concentration-dependent displacement experiments at both room and body temperatures. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) supported by ²H nuclear magnetic resonance (NMR) spectroscopy and thermodynamic modelling revealed the complexation efficacy of the agents under physiological conditions. Results demonstrate that high affinity, governed by complex stability constants and ligand pK_a values, is critical to overcome cation and anion competition and leads to effective decorporation. Additionally, there is evidence that cyclic ligands are inferior to linear ligands for this application. HOPO and DTPA exhibited superior displacement efficacy, particularly in the complete gastrointestinal tract simulation. This study highlights the utility of in vitro workflows for evaluating decorporation agents and emphasizes the need for ligands with optimal binding characteristics for enhanced chelation therapies. Full article

In this study, kaolinite-based clay (Ka-Clay) was used as an adsorbent for the efficient removal of Pb(II), Cd(II) and Hg(II) ions from aqueous media. The selection of Pb(II), Cd(II) and Hg(II) ions for experimental studies took into account their high toxicity, while the choice of Ka-Clay, the ease of preparation and high availability of this material were the most important arguments. Ka-Clay exhibits high adsorption performance, with removal percents over 98% for Pb(II) and 93% for Cd(II), even at high concentrations of metal ions (over 150 mg/L, pH = 6.5, 4 g adsorbent/L, 21 ± 1 °C). For Hg(II) ions, the adsorption percent does not exceed 55%, and this moderate value is mainly due to the significant change in pH. The adsorption behavior was in accordance with the Langmuir model (R² > 0.95) and the pseudo-second order kinetic model (R² > 0.99), indicating an adsorption process that occurs mainly through chemical interactions at the adsorbent surface between the metal ions and the functional groups. Adsorption processes are spontaneous (ΔG = −8.66 ÷ −15.76 kJ/mol) and endothermic (ΔH = 7.09 ÷ 21.81 kJ/mol), and the adsorption mechanism is the results of elementary processes of electrostatic attraction, ion exchange and superficial complexation. The insignificant effect of other ions (Ca(II), Mg(II), Na(I), K(I)) present in real wastewater samples as well as the desorption behavior of exhausted adsorbent highlight the practical utility of this adsorbent on a large scale. The experimental results included in this study suggest that Ka-Clay can be used as a promising adsorbent for the removal of high concentrations of toxic heavy metals with low cost and high efficiency, and this can contribute to the design of a sustainable wastewater treatment method. Full article

Soil carbon is a crucial component of the global carbon cycle, and carbon mineralization is influenced by various factors. However, there is a lack of systematic analyses on the responses of carbon mineralization in different soil types to the addition of exogenous organic matter. This study investigates the effects of compost addition on the mineralization and kinetic characteristics of soil carbon across three typical agricultural soils: paddy soil, black soil, and cinnamon soil. A 210-day incubation study was conducted with four treatments: Control (un-amended soil), R (soil + straw), R1M (soil + straw + low compost application rate), R2M (soil + straw + high compost application rate). The results showed that the CO₂ emission rates of the three soils were higher during the early stage (1–37 days) and decreased afterward. The CO₂ emission rates of the paddy soil and the black soil were significantly higher than those of the cinnamon soil. The addition of compost significantly increased both the CO₂ emission rate and the cumulative release of CO₂, especially in the R2M treatment. At the end of the incubation, the SOC contents were higher in the R2M treatment than in the Control for all three soils (p < 0.05), with the most notable increase in the cinnamon soil (60.93%). Compost addition significantly enhanced the active carbon pool (C_a), slow carbon pool (C_s), and potentially mineralizable carbon pool (C_p), while decreasing the mineralization rate (k_a) of the C_a, but the effect on the mineralization rate (k_s) of the C_s and mineralization entropy (C_m) varied by soil types. The k_s of the paddy soil was significantly reduced by 23.08% under the R1M and R2M treatments compared with the Control and R treatment. The k_s of the black soil was significantly increased by 59.52% under the R2M treatment compared with the Control. The k_s of the cinnamon soil was elevated considerably by 79.31% under the R2M treatment compared with the Control, R, and R1M treatments (averaging 0.29 × 10⁻² d), and the k_s of the paddy soil and black soil were significantly higher than those of the cinnamon soil under the R2M treatment. The C_m was significantly higher in the organic material added treatments than in the Control for the black soil and the paddy soil, but showed a higher value in the R treatment than in the R2M and Control for the cinnamon soil. In conclusion, compost addition stimulated soil carbon mineralization and improved the SOC content, especially in the cinnamon soil, while reducing the mineralization rate of the active carbon pool across the three soils. The mineralization rate of the slow carbon pool and the changes in mineralization entropy were dependent on soil types, primarily related to the initial soil nutrient contents, pH, and particle compositions. These findings offer valuable insights for managing the soil carbon pool in agricultural ecosystems. Full article

The large yellow croaker, or Larimichthys crocea, is highly prized for its golden color and nutritional content. The purpose of this study was to investigate the differences in body composition, mucus biochemical indices and body color in five strains of large yellow croakers (body weight: 347.01 ± 5.86 g). To conduct genetic diversity analyses of the populations, a total of 50 tailfin samples were randomly chosen from the following populations of large yellow croakers: wild (LYC1), Dai-qu population (LYC2), Yongdai 1 (LYC3), Min-yuedong population (LYC4), and Fufa 1 (LYC5). The findings demonstrated that the LYC3 group’s pigment contents, crude protein, crude lipid, and chromatic values were comparable to those of the LYC1 group (p > 0.05). There was no significant difference between the LYC1 and LYC5 groups’ mucus superoxide dismutase (SOD) and catalase (CAT) activities (p > 0.05). The alkaline phosphatases (ALP), acid phosphatases (ACP), and lysozyme (LYS) activities of the mucus in the LYC1 group were not significantly different from the LYC3 group (p > 0.05). The back skin mRNA expressions of tyrosinase (tyr), tyrosinase-related protein 1 (tyrp1), dopachrome tautomerase (dct), microphtalmia-associated transcription factor (mitf), and melanocortin 1 receptor (mc1r) were significantly up-regulated in the LYC2 and LYC4 groups compared to the LYC1, LYC3, and LYC5 groups (p < 0.05). Forkhead box d3 (foxd3), paired box 3 (pax3), purine nucleoside phosphorylase 4a (pnp4a), aristaless-like homeobox 4a (alx4a), cAMP dependent protein kinase (pka), anaplastic lymphoma kinase (alk), leukocyte receptor tyrosine kinase (ltk), and colony stimulating factor (fms) were among the mRNA expressions of the abdominal skin in the LYC1, LYC3, and LYC5 groups significantly higher than those in the LYC2 and LYC4 groups (p < 0.05). In conclusion, the LYC3 group’s crude protein, crude lipid, carotenoid, and lutein contents were most similar to those of the large yellow croaker found in the wild. Furthermore, the molecular mechanism underlying the variations in body color among the various strains of large yellow croakers was supplied for additional research. Full article

Tarantulas represent a highly diverse taxonomic group and play a crucial role in ecosystems. To gain a deeper understanding of the evolutionary relationships within the family Theraphosidae, in this study, we characterized the mitochondrial genome (mitogenome) of Phormictopus cancerides for the first time. The mitogenome is a typical circular double-stranded molecule, with a size of 13,776 bp. P. cancerides exhibited an A/T nucleotide preference (61.9–68.5% A + T content), with their rRNAs and tRNAs showing higher values than PCGs and the CR. The genes and the gene order were consistent with other Theraphosidae mitogenomes. The mitogenome was compacted and showed a bias for A/T. Ka/Ks analyses showed that the ND3 gene had the highest evolutionary rate, while the COX1 gene displayed a relatively slower evolution. Our phylogenetic analysis based on mitogenomes showed the subfamily Theraphosinae is closely related to the subfamily Harpactirinae and the subfamily Selenocosmiinae. Our results could contribute to the study of relationships within the family Theraphosidae and lay the foundation for further studies on tarantulas. Full article

Background/Objectives: Mango, which is known as the “King of Tropical Fruits”, is an evergreen plant belonging to the Anacardiaceae family. It belongs to the genus Mangifera, which comprises 69 species of plants found in tropical and subtropical regions, including India, Indonesia, the Malay Peninsula, Thailand, and South China. However, research on the structural information of complete chloroplast genomes of Mangifera is limited. Methods: The rapid advancement of high-throughput sequencing technology enables the acquisition of the entire chloroplast (cp) genome sequence, providing a molecular foundation for phylogenetic research. This work sequenced the chloroplast genomes of six Mangifera samples, performed a comparative analysis of the cp genomes, and investigated the evolutionary relationships within the Mangifera genus. Results: All six Mangifera samples showed a single circular molecule with a quadripartite structure, ranging from 157,604 bp to 158,889 bp in length. The number of RNA editing sites ranged from 60 to 61, with ndhB exhibiting the highest number of RNA editing sites across all species. Seven genes—namely, atpB, cemA, clpP, ndhD, petB, petD, and ycf15—exhibited a Ka/Ks value > 1, suggesting they may be under positive selection. Phylogenetic analysis revealed that Mangifera siamensis showed a close relationship between Mangifera indica and Mangifera sylvatica. Conclusions: Our comprehensive analysis of the whole cp genomes of the five Mangifera species offers significant insights regarding their phylogenetic reconstruction. Moreover, it elucidates the evolutionary processes of the cp genome within the Mangifera genus. Full article

Gas-phase basicity and basicity in acetonitrile solvent were investigated for a series of proton sponges derived from phosphazenyl phosphines. A range of aromatic and aliphatic scaffolds bearing phosphazenyl phosphine substituents were employed to modulate the basicity of these compounds, primarily by varying the distance between the phosphazenyl phosphine units. These proton sponges were shown to be exceptionally strong organic bases, with pK_a values in acetonitrile reaching up to 42.0 units and gas-phase proton affinities (PA) up to 307.0 kcal mol⁻¹. However, none exhibited higher basicity than the closely related phosphazenylphosphine systems, for which a pK_a value of 43.8 and PA value of 307.5 kcal mol⁻¹ was previously reportedIt was found that the proton-chelating effect, typically defined as the difference in proton affinity between bis- and mono-substituted systems (ΔPA), moderately influences basicity. However, it was also established that ΔPA should not be attributed exclusively to the elimination of electron-pair repulsion and the formation of hydrogen bond upon protonation, as has been commonly assumed in most previous studies of proton sponges, but must also account for mesomeric and inductive effects, as well as dispersion interactions. Full article

This study employed computational methods to investigate the basicity of a series of polyfluorinated phosphanes. Results revealed an exceptionally low basicity, with the computed pK_aH values in acetonitrile approaching −30, a value significantly lower than anticipated. The good agreement between the SMD and COSMO-RS methods provided confidence in the reliability of these values. This unexpected behavior challenges conventional perceptions of phosphane basicity and deepens our understanding of the electronic effects of fluorination. The findings hold important implications for catalysis, ligand design, and main-group chemistry, where a precise comprehension of phosphane electronic properties is crucial. pK_aH(MeCN) values, gas-phase basicities, and steric parameters are reported for 14 phosphanes. Full article

The kynurenine pathway is a significant metabolic route involved in the catabolism of tryptophan, producing various bioactive metabolites with crucial roles as antioxidants in immune regulation and neurobiology. This study investigates the acid-base properties of picolinic acid, kynurenic acid, kynurenine, and 3-hydroxykynurenine, utilizing computational simulations and experimental techniques, including potentiometric and nuclear magnetic resonance titrations. The results reveal distinct pK_a values, with kynurenic acid exhibiting a single dissociation step around 2.4, while kynurenine displays three dissociation steps governed by interactions between its functional groups. Additionally, 3-hydroxykynurenine shows overlapping dissociations in two separate pH regions, suggesting nuanced behavior influenced by its molecular structure. The analysis of intramolecular hydrogen bonding in protonation microspecies across varying pH highlights the relevance of the charge state and hydrogen transfer potential of these metabolites in the context of their radical scavenging ability. At physiological pH, most kynurenine and 3-hydroxykynurenine entities exist in zwitterionic form, with hydrogen bonding stabilizing the aromatic amino group, which may significantly influence their interactions with proteins and reactive oxygen species. This study provides critical insights into the acid-base equilibria of kynurenine pathway metabolites. Full article

cAMP (cyclic adenosine-3′,5′-monophosphate) has extensive physiological functions and nutritional value for living organisms, and it regulates cellular metabolism mainly by modulating PKA (protein kinase A) activity. The current yields of cAMP synthesized by microbial fermentation are still low, which is arousing interest in developing high-yield cAMP strains. In this work, two baker’s yeasts with high cAMP content were constructed by knocking out BCY1, TPK3, and TPK2 genes, and truncating the promoter of the TPK1 gene. The content of cAMP in BN5-126 and BN5-310 (with the TPK1 gene promoter truncated by 126 and 310 bp in BN5) was improved by 30- and 9-fold, respectively, relative to the wild strain. The TPK1 gene mRNA levels of BN5-126 and BN5-310 were decreased by 18% and 40%, respectively, without significant changes in growth performance. The results of heat shock tolerance of engineered strains also reflected the enhanced PKA activity. This work demonstrates a novel strategy for regulating gene expression to boost cAMP biosynthesis in yeast, providing a promising platform for producing nutritionally enriched and functional fermented products. Full article

The DC global electric circuit, GEC, was conceived by C.T.R. Wilson more than a century ago. Powered by thunderstorms and electrified shower clouds, an electric current I ~1 kA flows up into the ionosphere, maintaining the ionospheric potential V ~250 kV with respect to the Earth’s surface. The circuit is formed by the current I, flowing through the ionosphere all around the world, down through the atmosphere remote from the current sources (J ~2 pA/m² through a resistance R ~250 Ω), through the land and sea surface, and up to the thunderstorms as point discharge currents. This maintains a downward electric field E of magnitude ~130 V/m at the Earth’s surface away from thunderstorms and a charge Q ~−6.10⁵ C on the Earth’s surface. The theoretical modelling of ionospheric currents and the miniscule geomagnetic field perturbations (ΔB ~0.1 nT) which they cause, as derived by Denisenko and colleagues in recent years, are reviewed. The time constant of the GEC, τ = RC, where C is the capacitance of the global circuit capacitor, is estimated via three different methods to be ~7 to 12 min. The influence of stratus clouds in determining the value of τ is shown to be significant. Sudden excitations of the GEC by volcanic lightning in Iceland in 2011 and near the Tonga eruption in 2022 enable τ to be determined, from experimental observations, as ~10 min and 8 min, respectively. It has been suggested that seismic activity, or earthquake precursors, could produce large enough electric fields in the ionosphere to cause detectable effects, either by enhanced radon emission or by enhanced thermal emission from the earthquake region; a review of the quantitative estimates of these mechanisms shows that they are unlikely to produce sufficiently large effects to be detectable. Finally, some possible links between the topics discussed and human health are considered briefly. Full article

Background: This study compared the early rehabilitation progress of patients undergoing robotic-assisted medial unicompartmental knee arthroplasty (mUKA) and robotic-assisted kinematically aligned total knee arthroplasty (rKA-TKA), focusing on daily activity by step-count measurements. Methods: A retrospective analysis of prospectively collected data from 88 patients (53 rKA-TKA and 35 mUKA) was conducted. Patients wore Garmin Vivofit^® 4 activity trackers pre and postoperatively. Daily step counts were analyzed, and clinical outcomes were assessed using various scores, including the Knee Society Score (KSS) and Forgotten Joint Score (FJS). Results: Preoperative median daily step counts were comparable between groups (rKA-TKA: 3988 and mUKA: 4315; p = 0.128). At 6 and 7 weeks post-surgery, the mUKA group showed significantly higher median step counts (3741 and 4730) compared to the rKA-TKA group (2370 and 2910), with p-values of 0.015 and 0.048, respectively. The mUKA group reached 86.7% of their preoperative step count at week 6 and 100% at week 7, while the rKA-TKA group achieved 59.4% and 73%, respectively. Both groups surpassed their preoperative activity levels by week 9. Clinical outcomes at 2 months and 1 year post-surgery showed no significant differences between groups. Conclusions: While both the mUKA and rKA-TKA patients achieved their preoperative daily activity levels within nine weeks post-surgery, the mUKA patients reached this milestone approximately two weeks earlier. This study demonstrates a clinical benefit of mUKA in terms of faster postoperative remobilization, even when compared to kinematically aligned robotic-assisted TKA. Full article

Equine follicle-stimulating hormone receptor (eFSHR) contains four extracellular N-linked glycosylation sites, which play important roles in agonist-induced signal transduction. Glycosylation regulates G protein-coupled receptor mechanisms by influencing folding, ligand binding, signaling, trafficking, and internalization. Here, we examined whether the glycosylated sites in eFSHR are necessary for cyclic adenosine monophosphate (cAMP) signal transduction and the phosphate extracellular signal-regulated kinase 1/2 (pERK1/2) response. We constructed mutants (N191Q, N199Q, N268Q, and N293Q) of the four N-linked glycosylation sites in eFSHR using site-directed mutagenesis. In wild-type (wt) eFSHR, the cAMP response gradually increased dose-dependently, displaying a strong response at the EC₅₀ and Rmax. Two mutants (N191Q and N199Q) considerably decreased the cAMP response. Both EC₅₀ values were approximately 0.46- and 0.44-fold compared to that of the eFSHR-wt, whereas Rmax levels were 0.29- and 0.45-fold compared to eFSHR-wt because of high-ligand treatment. Specifically, the EC₅₀ and Rmax values in the N268Q mutant were increased 1.23- and 1.46-fold, respectively, by eFSHR-wt. pERK1/2 activity in eFSHR-wt cells was rapid, peaked within 5 min, consistently sustained until 15 min, and then sharply decreased. pERK1/2 activity in the N191Q mutant showed a pattern similar to that of the wild type, despite impaired cAMP responsiveness. The N199Q mutant showed low pERK1/2 activity at 5 and 15 min. Interestingly, pERK1/2 activity in the N268Q and N298Q mutants was similar to that of eFSHR-wt at 5 min, but neither mutant showed any signaling at 15 min, despite displaying high cAMP responsiveness. Overall, eFSHR N-linked glycosylation sites can signal to pERK1/2 via PKA and the other signals, dependent on G protein coupling and β-arrestin-dependent recruitment. Our results provide strong evidence for a new paradigm in which cAMP signaling is not activated, yet pERK1/2 cascade remains strongly induced. Full article