Preparation of lignosulfonate‐based nanofiltration membranes with improved water desalination performance

Pulping and papermaking generate large amounts of waste in the form of lignosulfonates which have limited valorized applications so far. Herein, we report a novel lignosulfonate‐based nanofiltration membrane, prepared by using polyethylenimine (PEI) and sodium lignosulfonate (SL) via a layer‐by‐layer (LbL) self‐assembly. As a low‐cost and renewable natural polyelectrolyte, SL is selected to replace the synthetic polyelectrolyte commonly used in the conventional LbL fabrication for composite membranes. The prepared LbL (PEI/SL)₇ membranes were crosslinked by glutaraldehyde (GA) to obtain (PEI/SL)₇‐GA membranes with compact selective layer. We characterized (PEI/SL)₇ and (PEI/SL)₇‐GA membranes to study the chemical compositions, morphologies, and surface hydrophilicity. To improve the nanofiltration performances of the (PEI/SL)₇‐GA membranes for water desalination, we investigated the effects of the crosslinking time, GA concentration and the NaCl supporting electrolyte on membrane structure and performance. The optimized (PEI/SL)₇‐GA membrane exhibited a permeating flux up to 39.6 L/(m²·h) and a rejection of 91.7% for the MgSO₄ aqueous solution 2.0 g/L concentration, showing its promising potential for water desalination. This study provides a new approach to applying the underdeveloped lignin‐based biomass as green membrane materials for water treatment.     

Hydrogen sulphide reduces hyperhomocysteinaemia-induced endothelial ER stress by sulfhydrating protein disulphide isomerase to attenuate atherosclerosis

Hyperhomocysteinaemia (HHcy)-impaired endothelial dysfunction including endoplasmic reticulum (ER) stress plays a crucial role in atherogenesis. Hydrogen sulphide (H₂S), a metabolic production of Hcy and gasotransmitter, exhibits preventing cardiovascular damages induced by HHcy by reducing ER stress, but the underlying mechanism is unclear. Here, we made an atherosclerosis with HHcy mice model by ApoE knockout mice and feeding Pagien diet and drinking L-methionine water. H₂S donors NaHS and GYY4137 treatment lowered plaque area and ER stress in this model. Protein disulphide isomerase (PDI), a modulation protein folding key enzyme, was up-regulated in plaque and reduced by H₂S treatment. In cultured human aortic endothelial cells, Hcy dose and time dependently elevated PDI expression, but inhibited its activity, and which were rescued by H₂S. H₂S and its endogenous generation key enzyme-cystathionine γ lyase induced a new post-translational modification-sulfhydration of PDI. Sulfhydrated PDI enhanced its activity, and two cysteine-terminal CXXC domain of PDI was identified by site mutation. HHcy lowered PDI sulfhydration association ER stress, and H₂S rescued it but this effect was blocked by cysteine site mutation. Conclusively, we demonstrated that H₂S sulfhydrated PDI and enhanced its activity, reducing HHcy-induced endothelial ER stress to attenuate atherosclerosis development.     

Cyanobacterial phytochrome-like PixJ1 holoprotein shows novel reversible photoconversion between blue- and green-absorbing forms

The gene, pixJ1 (formerly pisJ1), is predicted to encode a phytochrome-like photoreceptor that is essential for positive phototaxis in the unicellular cyanobacterium Synechocystis sp. PCC 6803 [Yoshihara et al. (2000) Plant Cell Physiol. 41: 1299]. The PixJ1 protein was overexpressed as a fusion with a poly-histidine tag (His-PixJ1) and isolated from Synechocystis cells. A zinc-fluorescence assay suggested that a linear tetrapyrrole was covalently attached to the His-PixJ1 protein as a chromophore. His-PixJ1 showed novel photoreversible conversion between a blue light-absorbing form (Pb, lambdaAmax=425-435 nm) and a green light-absorbing form (Pg, lambdaAmax=535 nm). Dark incubation led Pg to revert to Pb, indicative of stability of the Pb form in darkness. Red or far-red light irradiation, which is effective for photochemical conversion of the known phytochromes, produced no change in the spectra of Pb and Pg forms. Site-directed mutagenesis revealed that a Cys-His motif in the second GAF domain of PixJ1 is responsible for binding of the chromophore. Possible chromophore species are discussed with regard to the novel photoconversion spectrum.     

Length‐length and length‐weight relationships for four fish species from Naolihe National Nature Reserve,Heilongjiang, China

In this study the length‐length and length‐weight relationships for four fish species from Naolihe National Nature Reserve in China belonging to three families and four genera were analyzed. They are Perccottus glenii Dybowski, 1877; Rhodeus sericeus Pallas, 1776; Cobitis lutheri Rendahl, 1935; and Misgurnus mohoity Dybowski, 1869. Fish samples were collected in May 2017 from Naolihe National Nature Reserve by fish catching cage (31*41 cm caliber, 16 m length, 3–5 mm mesh diameter), and identified as to species in the laboratory according to S. Q. Zhu (Synopsis of freshwater fishes of China, Jiangsu Science and Technology Publishing House, Nanjing, China, 1995).     

Bis-Fe(IV): nature’s sniper for long-range oxidation

Iron-dependent enzymes are prevalent in nature and participate in a wide range of biological redox activities. Frequently, high-valence iron intermediates are involved in the catalytic events of iron-dependent enzymes, especially when the activation of peroxide or molecular oxygen is involved. Building on the fundamental framework of iron–oxygen chemistry, these reactive intermediates constantly attract significant attention from the enzymology community. During the past few decades, tremendous efforts from a number of laboratories have been dedicated to the capture and characterization of these intermediates to improve mechanistic understandings. In 2008, an unprecedented bis-Fe(IV) intermediate was reported in a c-type diheme enzyme, MauG, which is involved in the maturation of a tryptophan tryptophylquinone cofactor of methylamine dehydrogenase. This intermediate, although chemically equivalent to well-characterized high-valence iron intermediates, such as compound I, compound ES, and intermediate Q in methane monooxygenase, as well as the hypothetical Fe(V) species in Rieske non-heme oxygenases, is orders of magnitude more stable than these other high-valence species in the absence of its primary substrate. It has recently been discovered that the bis-Fe(IV) intermediate exhibits a unique near-IR absorption feature which has been attributed to a novel charge-resonance phenomenon. This review compares the properties of MauG with structurally related enzymes, summarizes the current knowledge of this new high-valence iron intermediate, including its chemical origin and structural basis, explores the formation and consequences of charge resonance, and recounts the long-range catalytic mechanism in which bis-Fe(IV) participates. Biological strategies for storing oxidizing equivalents with iron ions are also discussed.     

Modulation of Self-Esteem in Self- and Other-Evaluations Primed by Subliminal and Supraliminal Faces

Background

Past research examining implicit self-evaluation often manipulated self-processing as task-irrelevant but presented self-related stimuli supraliminally. Even when tested with more indirect methods, such as the masked priming paradigm, participants'' responses may still be subject to conscious interference. Our study primed participants with either their own or someone else''s face, and adopted a new paradigm to actualize strict face-suppression to examine participants'' subliminal self-evaluation. In addition, we investigated how self-esteem modulates one''s implicit self-evaluation and validated the role of awareness in creating the discrepancy on past findings between measures of implicit self-evaluation and explicit self-esteem.

Methodology/Principal Findings

Participants'' own face or others'' faces were subliminally presented with a Continuous Flash Suppression (CFS) paradigm in Experiment 1, but supraliminally presented in Experiment 2, followed by a valence judgment task of personality adjectives. Participants also completed the Rosenberg Self-Esteem Scale in each experiment. Results from Experiment 1 showed a typical bias of self-positivity among participants with higher self-esteem, but only a marginal self-positivity bias and a significant other-positivity bias among those with lower self-esteem. However, self-esteem had no modulating effect in Experiment 2: All participants showed the self-positivity bias.

Conclusions/Significance

Our results provide direct evidence that self-evaluation manifests in different ways as a function of awareness between individuals with different self-views: People high and low in self-esteem may demonstrate different automatic reactions in the subliminal evaluations of the self and others; but the involvement of consciousness with supraliminally presented stimuli may reduce this dissociation.     

Characterization of a novel melamine-degrading bacterium isolated from a melamine-manufacturing factory in China

Melamine (2,4,6-triamino-1,3,5-triazine, C₃H₆N₆), belonging to the s-triazine family, is an anthropogenic and versatile raw material for a large number of consumer products and its extensive use has resulted in the contamination of melamine in the environment. A novel melamine-degrading bacterium strain CY1 was isolated from a melamine-manufacturing factory in China. The strain is phylogenetically different from the known melamine-degrading bacteria. Approximately, 94 % melamine (initial melamine concentration 4.0 mM, initial cell OD 0.05) was degraded in 10 days without the addition of additional carbon source. High-performance liquid chromatography showed the production of degradation intermediates including ammeline, ammelide, cyanuric acid, biuret, and urea. Kinetic simulation analysis indicated that transformation of urea into ammonia was the rate-limiting step for the degradation process. The melamine–cyanurate complex was formed due to self-assembly of melamine and cyanuric acid during the degradation. The tracking experiment using CY1 cells and ¹³C₃-melamine showed that the CY1 could mineralize s-triazine ring carbon to CO₂. The strain CY1 could also catalyze partial transformation of cyromazine, a cyclopropyl derivative of melamine, to 6-(cyclopropylamino)-[1,3,5]triazine-2,4-diol.     

Neutrophil recognition requires a Ca(2+)-induced conformational change in the lectin domain of GMP-140.

GMP-140, a receptor for myeloid cells that is expressed on surfaces of thrombin-activated platelets and endothelial cells, is a member of the selectin family of adhesion molecules that regulate leukocyte interactions with the blood vessel wall. Each selectin contains an N-terminal domain homologous to Ca(2+)-dependent lectins and mediates cell-cell contact by binding to oligosaccharide ligands in a Ca(2+)-dependent manner. The mechanisms by which Ca2+ promotes selectin-dependent cellular interactions have not been defined. We demonstrate that purified GMP-140 contains two high affinity binding sites for Ca2+ as measured by equilibrium dialysis (Kd = 22 +/- 2 microM). Occupancy of these sites by Ca2+ alters the conformation of the protein as detected by a reduction in intrinsic fluorescence emission intensity (Kd = 4.8 +/- 0.2 microM). This Ca(2+)-dependent conformational change exposes an epitope spanning residues 19-34 of the lectin domain that is recognized by a monoclonal antibody capable of blocking neutrophil adhesion to GMP-140 (half-maximal antibody binding at approximately 20 microM Ca2+). Furthermore, a synthetic peptide encoding this epitope, CQNRYTDLVAIQNKNE, inhibits neutrophil binding to GMP-140. Mg2+ also alters the conformation of the protein, but not in a manner that will support leukocyte recognition in the absence of Ca2+. There is a strong correlation between the Ca2+ levels required for neutrophil adhesion to GMP-140, for occupancy of the two Ca(2+)-binding sites, for the fluorescence-detected conformational change, and for exposure of the antibody epitope in the lectin domain. We conclude that binding of Ca2+ to high affinity sites on GMP-140 modulates the conformation of the lectin domain in a manner that is essential for leukocyte recognition.