Quantifying Stochastic Processes in Shaping Dissolved Organic Matter Pool with High-Resolution Mass Spectrometry.

Natural dissolved organic matter (DOM) represents a ubiquitous molecular mixture, progressively characterized by spatiotemporal resolution. However, an inadequate comprehension of DOM molecular dynamics, especially the stochastic processes involved, hinders carbon cycling predictions. This study employs ecological principles to introduce a neutral theory to elucidate the fundamental processes involving molecular generation, degradation, and migration. A neutral model is thus formulated to assess the probability distribution of DOM molecules, whose frequencies and abundances follow a ß-distribution relationship. The neutral model is subsequently validated with high-resolution mass spectrometry (HRMS) data from various waterbodies, including lakes, rivers, and seas. The model fitting highlights the prevalence of molecular neutral distribution and quantifies the stochasticity within DOM molecular dynamics. Furthermore, the model identifies deviations of HRMS observations from neutral expectations in photochemical and microbial experiments, revealing nonrandom molecular transformations. The ecological null model further validates the neutral modeling results, demonstrating that photodegradation reduces molecular stochastic dynamics at the surface of an acidic pit lake, while random distribution intensifies at the river surface compared with the porewater. Taken together, the DOM molecular neutral model emphasizes the significance of stochastic processes in shaping a natural DOM pool, offering a potential theoretical framework for DOM molecular dynamics in aquatic and other ecosystems.

Molecular insights into the impacts of acid mine drainage on dissolved organic matter dynamics in pit lakes.

Pit lakes are artificial hydrological features created by mining operations that typically suffer from acid mine drainage (AMD), which not only endangers water quality but also exacerbates carbon loss. However, the impacts of AMD on the fate and role of dissolved organic matter (DOM) in pit lakes remain unclear. This study employed negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with biogeochemical analysis to examine DOM molecular variations and environmental controls across the AMD-induced acidic and metalliferous gradients in five pit lakes. The results demonstrated distinct DOM pools in pit lakes characterized by the prevalence of smaller aliphatic compounds compared to other waterbodies. AMD-induced geochemical gradients promoted DOM heterogeneity among pit lakes, with acidic pit lakes containing more lipid-like compounds. Acidity and metals enhanced DOM photodegradation, reducing the content, chemo-diversity and aromaticity. Organic sulfur was detected in high abundance, potentially from sulfate photo-esterification and mineral flotation agent. Furthermore, microbial involvements in carbon cycling were revealed by DOM-microbe correlation network, but microbial contributions to the DOM pools decreased under acidic and metal stresses. These findings highlight abnormal carbon dynamics caused by AMD pollution and integrate DOM fate into pit lake biogeochemistry, thereby contributing to management and remediation.

Optimization of Extraction Process, Structure Characterization, and Antioxidant Activity of Polysaccharides from Different Parts of Camellia oleifera Abel.

The flowers, leaves, seed cakes and fruit shells of Camellia oleifera are rich in bioactive polysaccharides, which can be used as additives in food and other industries. In this study, a Box-Behnken design was used to optimize the extraction conditions of polysaccharides from C. oleifera flowers (P-CF), leaves (P-CL), seed cakes (P-CC), and fruit shells (P-CS). Under the optimized extraction conditions, the polysaccharide yields of the four polysaccharides were 9.32% ± 0.11 (P-CF), 7.57% ± 0.11 (P-CL), 8.69% ± 0.16 (P-CC), and 7.25% ± 0.07 (P-CS), respectively. Polysaccharides were mainly composed of mannose, rhamnose, galacturonic acid, glucose, galactose, and xylose, of which the molecular weights ranged from 3.31 kDa to 128.06 kDa. P-CC had a triple helix structure. The antioxidant activities of the four polysaccharides were determined by Fe2+ chelating and free radical scavenging abilities. The results showed that all polysaccharides had antioxidant effects. Among them, P-CF had the strongest antioxidant activity, of which the highest scavenging ability of DPPH•, ABTS•+, and hydroxyl radical could reach 84.19% ± 2.65, 94.8% ± 0.22, and 79.97% ± 3.04, respectively, and the best chelating ability of Fe2+ could reach 44.67% ± 1.04. Overall, polysaccharides extracted from different parts of C. oleifera showed a certain antioxidant effect, and could be developed as a new type of pure natural antioxidant for food.

A peroxidase coordinating to Zn (II) preventing heme bleaching and resistant to the interference of H2 O2.

Dehaloperoxidase (DHP) catalyzes detoxifying halophenols. It is a heme-containing enzyme using H2 O2 as the oxidant. Heme bleaching from the active site is of great concern. In addition, the interference of DHP by H2 O2 leads to the inactivation of the enzyme. To solve these two problems, DHP is coordinated to Zn (II) in PBS buffer to form a biomineralized composite (DHP&Zn-CP). DHP&Zn-CP was characterized by measuring SEM and confocal images, as well as energy dispersive X-ray spectrometry mapping. Fluorescence spectra demonstrated that DHP&Zn-CP can prevent heme bleaching. Two-dimensional FTIR spectra were measured, dynamically providing insight into the structural change of DHP along the coordination process. Raman spectra were performed to analyze the structural change. The optical spectra confirmed that the forming of DHP&Zn-CP had a little effect on the structures of DHP. For the dehalogenation of 2,4,6-trichlorophenol, DHP&Zn-CP can tolerate the presence of H2 O2 and is resistant to the interference by H2 O2 . The catalytic efficiency of DHP&Zn-CP is much higher than that of free DHP.

Combination treatment with tenapanor and sevelamer synergistically reduces urinary phosphorus excretion in rats.

The majority of patients with chronic kidney disease (CKD) receiving dialysis do not achieve target serum phosphorus concentrations, despite treatment with phosphate binders. Tenapanor is a nonbinder, sodium/hydrogen exchanger isoform 3 (NHE3) inhibitor that reduces paracellular intestinal phosphate absorption. This preclinical study evaluated the effect of tenapanor and varying doses of sevelamer carbonate on urinary phosphorus excretion, a direct reflection of intestinal phosphate absorption. We measured 24-h urinary phosphorus excretion in male rats assigned to groups dosed orally with vehicle or tenapanor (0.3 mg/kg/day) and provided a diet containing varying amounts of sevelamer [0-3% (wt/wt)]. We also evaluated the effect of the addition of tenapanor or vehicle on 24-h urinary phosphorus excretion to rats on a stable dose of sevelamer [1.5% (wt/wt)]. When administered together, tenapanor and sevelamer decreased urinary phosphorus excretion significantly more than either tenapanor or sevelamer alone across all sevelamer dose levels. The Bliss statistical model of independence indicated that the combination was synergistic. A stable sevelamer dose [1.5% (wt/wt)] reduced mean ± SE urinary phosphorus excretion by 42 ± 3% compared with vehicle; together, tenapanor and sevelamer reduced residual urinary phosphorus excretion by an additional 37 ± 6% (P < 0.05). Although both tenapanor and sevelamer reduce intestinal phosphate absorption individually, administration of tenapanor and sevelamer together results in more pronounced reductions in intestinal phosphate absorption than if either agent is administered alone. Further evaluation of combination tenapanor plus phosphate binder treatment in patients receiving dialysis with hyperphosphatemia is warranted.

Fabrication of a Fibrous Metal-Organic Framework and Simultaneous Immobilization of Enzymes.

A nanorod-like lanthanum metal-organic framework (LaMOF) was synthesized in aqueous solution by coordinating La(III) to the ligand 1,3,5-benzenetricarboxylic acid. The fibrous LaMOF was fabricated by splitting the nanorod-like LaMOF in a solution of d-amino acid oxidase, and the enzyme was immobilized simultaneously. Based on SEM and TEM images, STEM mapping, and spectra of XPS and FTIR, the mechanism of formation of the fibrous LaMOF and the distinct interfacial phenomena have been elucidated. The fabrication of the fibrous LaMOF and simultaneous immobilization of the enzyme were carried out in aqueous solutions at room temperature, without using any organic solvent. It is a clean and time- and energy-effective process. This work presents a distinct and clean methodology for the fabrication of the fibrous MOF. Potentially, the environmentally benign methodology can be extended to immobilize other enzymes.

Intestinal TGR5 agonism improves hepatic steatosis and insulin sensitivity in Western diet-fed mice.

Takeda G protein-coupled receptor 5 (TGR5) agonists induce systemic release of glucagon-like peptides (GLPs) from intestinal L cells, a potentially therapeutic action against metabolic diseases such as nonalcoholic steatohepatitis (NASH), nonalcoholic fatty liver disease (NAFLD), and Type 2 diabetes. Historically, TGR5 agonist use has been hindered by side effects, including inhibition of gallbladder emptying. Here, we characterize RDX8940, a novel, orally administered TGR5 agonist designed to have minimal systemic effects and investigate its activity in mice fed a Western diet, a model of NAFLD and mild insulin resistance. Agonist activity, binding selectivity, toxicity, solubility, and permeability of RDX8940 were characterized in standard in vitro models. RDX8940 pharmacokinetics and effects on GLP secretion, insulin sensitivity, and liver steatosis were assessed in C57BL/6 mice fed normal or Western diet chow and given single or repeated doses of RDX8940 or vehicle, with or without dipeptidyl peptidase-4 (DPP4) inhibitors. Gallbladder effects were assessed in CD-1 mice fed normal chow and given RDX8940 or a systemic TGR5 agonist or vehicle. Our results showed that RDX8940 is minimally systemic, potent, and selective, and induces incretin (GLP-1, GLP-2, and peptide YY) secretion. RDX8940-induced increases in plasma active GLP-1 (aGLP-1) levels were enhanced by repeated dosing and by coadministration of DPP4 inhibitors. RDX8940 increased hepatic exposure to aGLP-1 without requiring coadministration of a DPP4 inhibitor. In mice fed a Western diet, RDX8940 improved liver steatosis and insulin sensitivity. Unlike systemic TGR5 agonists, RDX8940 did not inhibit gallbladder emptying. These results indicate that RDX8940 may have therapeutic potential in patients with NAFLD/NASH. NEW & NOTEWORTHY Takeda G protein-coupled receptor 5 (TGR5) agonists have potential as a treatment for nonalcoholic steatohepatitis and nonalcoholic fatty liver disease (NAFLD) but have until now been associated with undesirable side effects associated with systemic TGR5 agonism, including blockade of gallbladder emptying. We demonstrate that RDX8940, a potent, selective, minimally systemic oral TGR5 agonist, improves liver steatosis and insulin sensitivity in a mouse model of NAFLD and does not inhibit gallbladder emptying in mice.

Halomonas shengliensis sp. nov., a moderately halophilic, denitrifying, crude-oil-utilizing bacterium.

A moderately halophilic bacterium, designated strain SL014B-85(T), was isolated from a crude-oil-contaminated saline soil from Shengli oilfield, Shandong Province, China. Cells were Gram-negative, aerobic, short rods with lateral flagella. Growth occurred at NaCl concentrations of 0-15 % (optimum 5-15 %), at 10-42 degrees C (optimum 30 degrees C) and at pH 8.0-9.0 (optimum pH 8.5). The only respiratory quinone was Q9, and the main cellular fatty acids were C(18 : 1)omega7c, C(16 : 0) and C(19 : 0) cyclo omega8c. The G+C content of the DNA was 66.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SL014B-85(T) belonged to the genus Halomonas in the Gammaproteobacteria, with highest sequence similarity of 98.1 and 97.8 % to Halomonas alimentaria DSM 15356(T) and Halomonas ventosae DSM 15911(T), respectively. DNA-DNA relatedness values were below 40 % with members of closely related Halomonas species. Results of phenotypic, biochemical and phylogenetic analyses revealed that strain SL014B-85(T) could be classified as representing a novel species of the genus Halomonas, for which the name Halomonas shengliensis sp. nov. is proposed. The type strain is SL014B-85(T) (=CGMCC 1.6444(T)=LMG 23897(T)).