NEDD4L intramolecular interactions regulate its auto and substrate NaV1.5 ubiquitination.

NEDD4L is a HECT-type E3 ligase that catalyzes the addition of ubiquitin to intracellular substrates such as the cardiac voltage-gated sodium channel, NaV1.5. The intramolecular interactions of NEDD4L regulate its enzymatic activity which is essential for proteostasis. For NaV1.5, this process is critical as alterations in Na+ current is involved in cardiac diseases including arrhythmias and heart failure. In this study, we perform extensive biochemical and functional analyses that implicate the C2 domain and the first WW-linker (1,2-linker) in the autoregulatory mechanism of NEDD4L. Through in vitro and electrophysiological experiments, the NEDD4L 1,2-linker was determined to be important in substrate ubiquitination of NaV1.5. We establish the preferred sites of ubiquitination of NEDD4L to be in the second WW-linker (2,3-linker). Interestingly, NEDD4L ubiquitinates the cytoplasmic linker between the first and second transmembrane domains of the channel (DI-DII) of NaV1.5. Moreover, we design a genetically encoded modulator of Nav1.5 that achieves Na+ current reduction using the NEDD4L HECT domain as cargo of a NaV1.5-binding nanobody. These investigations elucidate the mechanisms regulating the NEDD4 family and furnish a new molecular framework for understanding NaV1.5 ubiquitination.

The C-Terminal of NaV1.7 Is Ubiquitinated by NEDD4L.

NaV1.7, the neuronal voltage-gated sodium channel isoform, plays an important role in the human body's ability to feel pain. Mutations within NaV1.7 have been linked to pain-related syndromes, such as insensitivity to pain. To date, the regulation and internalization mechanisms of the NaV1.7 channel are not well known at a biochemical level. In this study, we perform biochemical and biophysical analyses that establish that the HECT-type E3 ligase, NEDD4L, ubiquitinates the cytoplasmic C-terminal (CT) region of NaV1.7. Through in vitro ubiquitination and mass spectrometry experiments, we identify, for the first time, the lysine residues of NaV1.7 within the CT region that get ubiquitinated. Furthermore, binding studies with an NEDD4L E3 ligase modulator (ubiquitin variant) highlight the dynamic partnership between NEDD4L and NaV1.7. These investigations provide a framework for understanding how NEDD4L-dependent regulation of the channel can influence the NaV1.7 function.

Catalytic ozonation with vanadium oxide-doped TiO2 nanoparticles for the removal of di-2-ethylhexyl phthalate.

Among various plastic additives, di-2-ethylhexyl phthalate (DEHP) has been a great concern due to its high leaching potential and harmful effects on both human and the ecosystem. For the effective oxidation and mineralization of DEHP by ozone in the existing TiO2 catalytic processes, the heterogeneous catalyst, vanadium oxide (V2O5)-incorporated TiO2 (V2O5/TiO2), was synthesized. The generation of hydroxyl radicals was promoted by cyclic redox reactions of vanadium atoms in V2O5/TiO2 via the increase of surface oxygen vacancies by the replacement of V5+ species in the lattice of TiO2. The catalytic ozonation in the presence of V2O5/TiO2 exhibited the significantly higher degradation of DEHP with the pseudo-second-order kinetic constant of 1.7 × 105 mM-1min-1 and the removal efficiency of 58.7% after 60 s in 2 mg/L of ozone. The degradation of DEHP was initiated by the shortening of the alkyl-side chain followed by the opening of esterified benzene moieties.

Novel method for the facile control of molecular weight cut-off (MWCO) of ceramic membranes.

This study demonstrates a simple and novel preparation method to prepare ceramic nanofiltration membranes with a precise and tunable molecular weight cut-off (MWCO) by packing variously sized nanoparticles into existing membrane pores. As a result, ceramic membranes with a MWCO from 1000 Da to 10,000 Da were successfully prepared with the narrow distribution of the pore size after the filtration-coating process. In addition, the effective porosity of the ceramic membranes was calculated from the results of the membrane properties by the Hagen-Poiseuille equation which fit within the range of the sphere packing theory from 17.3% to 41.8%. Furthermore, the results of nonlinear curve fitting between the MWCO and the nanoparticle size show a high accuracy, which implies that the MWCO of the ceramic membranes can be predicted using the curve fitting model with variously sized nanoparticles in the filtration-coating process. In conclusion, the novel filtration-coating method enables precise pore control and provides a tunable MWCO to ceramic membranes by preparing various sizes of nanoparticles.

Enhanced biodegradation of hydrocarbons by Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads.

Pseudomonas aeruginosa-encapsulated alginate/gellan gum microbeads (PAGMs) were prepared at the condition of 10 g/L alginate, 1 g/L gellan gum, and 2.57 mM calcium ions, and investigated for the biodegradation of a diesel-contaminated groundwater. The degradation of diesel with PAGMs reached 71.2% after 10days in the aerobic condition, while that of suspended bacteria was only 32.0% even after 30days. The kinetic analysis showed that PAGMs had more than two-order higher second-order kinetic constant than that of the suspended bacteria. Interestingly, the degradation of diesel was ceased due to the depletion of the dissolved oxygen after 10 day in the PAGM reactor, but the microbial degradation activity was immediately restored after the addition of oxygen to 10.5 mg/L. The change in ATP concentration and the viability of bacteria showed that the microbial activity in PAGMs were maintained (66.4%, and 84.3%, respectively) even after 30days of experiment with PAGMs due to the protective barrier of the microbeads, whereas those of suspended bacteria showed significant decrease to 6.2% and 14.4% of initial value, respectively, due to the direct contact to toxic hydrocarbons. The results suggested that encapsulation of bacterial cells could be used for the enhanced biodegradation of diesel hydrocarbons in aqueous systems.

The impact of gamma-irradiation from radioactive liquid wastewater on polymeric structures of nanofiltration (NF) membranes.

In this study, the impacts of gamma-irradiation from the low- and intermediate-level liquid radioactive wastewaters (LILW) to polyamide (PA) structures of nanofiltration (NF) membranes were investigated. As the gamma-irradiation increased to 300 kGy in the aqueous solution at 5 bar, both the salt rejection and the water permeability of NF membranes were decreased from 95.6 ±â€¯0.1%-74.6 ±â€¯0.5%, and from 33.7 ±â€¯0.3 LMH to 21.4 ±â€¯0.5 LMH, respectively. The surface free energy and Young's modulus of the membrane indicated the decrease in hydrophilicity and the increase in fragility of PA structure after gamma-irradiation. X-ray photoelectron spectroscopy and the streaming potential analysis exhibited that the gamma-irradiation resulted the increase in the cross-linked portion of the amide bonding from 28% to 45% due to the gamma-induced new bonding between unbound carboxylic groups and amine groups. Nuclear magnetic resonance analysis confirmed that the poly(p-phenylene) in polyamide structure were changed to poly(cyclohexane) and poly(cyclohexene) by hydrogen radical disproportionation generated from the gamma-irradiated water, and it is responsible to the increase of the cross-linked PA structures. The decrease in salt rejection and water permeability is attributed to the aging of PA structures by gamma-irradiation, thus, should be carefully monitored during the treatment of LILW using NF membrane processes.

Selective removal of color substances by carbon-based adsorbents in livestock wastewater effluents.

Livestock wastewater effluent generated after the anaerobic treatment process contains the considerable amount of color-causing organic matter. In this study, a quantitative comparison of three carbon-based adsorbents included granular activated carbon (GAC), expanded graphite (EG), and multi-walled carbon nanotubes (MWNTs) was carried out for the potential application to the removal of color substances, and their mechanism was proposed. Although GAC showed the highest specific dissolved organic carbon (DOC) adsorption capacity, the color removal efficiency was the smallest among three adsorbents. The selective color removal ratios of EG and MWNTs reached 22.7 ± 0.1 PtCo/mg-DOC-removed and 21.2 ± 0.1 PtCo/mg-DOC-removed, respectively, while that of GAC was only 12.3 ± 0.1 PtCo/mg-DOC-removed. The selective adsorption of color substances by graphene-based carbon materials was due to the aromatic π-π interaction between organic matter and the hexagonal carbon lattice of graphene. The analysis of molecular weight distribution also confirmed that the exposed surface area and macro-pores were responsible for the adsorption of high molecular weight color substances. The chemical regeneration of three adsorbents was examined using 1% NaOCl solution and MWNTs showed almost complete recovery of the initial color removal capacity. In conclusion, MWNTs were the most suitable carbon nanomaterial for the selective color removal from livestock wastewater effluent.

Increased biodegradability of low-grade coal wastewater in anaerobic membrane bioreactor by adding yeast wastes.

Demineralization is required in upgrading low-grade coal to serve as an alternative energy resource for the production of fuel and valuable chemicals but generates a large amount of low-grade coal wastewater (LCWW). The objective of this study was to investigate the effects of a co-substrate on an anaerobic membrane bioreactor (AnMBR) treating LCWW. CH4 was not produced during the operation fed by LCWW alone. When yeast wastes (YW) were supplemented, there was a gradual increase in the biodegradability of LCWW, achieving 182 CH4 mL/g COD with 58% COD removal efficiency. The analysis of physicochemical characteristics in the effluent of AnMBR, done by excitation-emission matrix (EEM) and size exclusion chromatography (SEC), showed that the proportion of soluble microbial products (SMPs) and aromatic group with high-molecular weight (>1 kDa) increased. Microbial analysis revealed that the increased dominance of bacteria Comamonas, Methanococcus, and Methanosarcina facilitated biodegradation of LCWW in the presence of YW.

Dissolved organic matter characterization of biochars produced from different feedstock materials.

Fluorescence excitation-emission matrix (EEM) spectroscopy coupled with parallel factor analysis (PARAFAC) enables better understanding of the nature of dissolved organic matter (DOM). In the current study, we characterized 10 biochar samples produced from different feedstocks using EEM/PARAFAC analysis. The composition and distribution of DOM substances present in biochar varied significantly according to feedstock, activation, and pyrolysis temperature. The integration of proximate and ultimate analyses of the solid phase together with water extractable organic matter (WEOM) phase of biochar provided new insights into the characterization of biochars, including nature and functionality. Characterization of both WEOM and solid phases is recommended for biochar research before large-scale production for various environmental and industrial applications.