Effect of cations on the structure of mung bean cytoplasmic ribosomes

The importance of the absolute and relative concentrations of monovalent and divalent cations and centrifugal speed (pressure) in the dissociation of mung bean 80S ribosomes has been examined. In the absence of Mg²⁺ ions, ribosome monomers yield 47S and 34S particles. Fixation with glutaraldehyde, however, indicates that this dissociation pattern is largely dependent upon high pressures developed during centrifugation and that in the absence of such artifacts the immediate product of Mg-free conditions is a 74S particle. Since 74S particles rapidly revert to the 80S form when Mg is replaced, this would appear to be a conformational change. Ribosomes were also dissociated in the presence of Mg²⁺ ions if the K⁺ ion concentration was raised. Three major particles were produced, 38S and 49S from the small ribosomal sub-unit and 60S from the large sub-unit. A proportion of the 80S monomer population is more resistant to dissociation. Experiments with puromycin indicate that the more resistant fraction probably represents ribosomes completed with nascent polypeptide resulting from polysome breakdown.     

Hill coefficient-based stochastic switch-like signal directly governs damage-recovery dynamics in freshwater fish in response to pulse copper

Growing evidence demonstrates that fluctuating metal stressors can have profound impact on the ecophysiological responses in aquatic species. However, how environmental stochasticity affects the complex damage-recovery dynamics in organisms remains difficult to predict. The objective of this paper was to investigate the stochastic behavior in the damage-recovery dynamics in tilapia in response to pulse waterborne copper (Cu). We developed a mathematical framework that allows discrimination between damage and recovery processes in tilapia exposed to designed pulse Cu scenarios. We built deterministic nonlinear models for the damage-recovery dynamics that produce response surfaces describing killing/recovery rate–Cu-pulse interval interactions. Here we showed that the stochastic switching behavior arose from competition among killing, recovery rates, and Cu pulse frequency. This competition resulted in an ultrasensitivity appeared in whole body, gills, muscle, liver, and kidney with Hill coefficients of ≥7, 4, 7, 5, and 5, respectively, at Cu 3 mg L⁻¹, dilution rate 0.05 h⁻¹, and pulse interval 72 h, indicating that a stochastic switch-like response was generated. We argue that the role of gill-associated Hill coefficient as a direct signal of the stochastic switch-like response in the damage-recovery dynamics in response to pulse metal stressor can serve as a sensitive indicator for risk detection in fluctuating environments. Our approach constitutes a general method to identify the stochastic switch-like response for aquatic species exposed to fluctuating metal stressors, which may help to predict and, eventually, expand our understanding of the damage-recovery dynamics. Finally, we implicate that Hill coefficient-based switch-like signal and its damage with hazard response can be linked in an information theoretic framework to handle environmental stochasticity.     

Human Health Risk Assessment of Soils Contaminated with Metal(loid)s by Using DGT Uptake: A Case Study of a Former Korean Metal Refinery Site

The human health risk of soils contaminated with As, Pb, Cu, and Zn was evaluated based on pseudo-total concentrations of metal(loid)s, the physiologically based extraction test (PBET), and diffusive gradients in thin films (DGT). Non-carcinogenic (NCR) and carcinogenic (CR) risks exceeded the U.S. Environmental Protection Agency criteria under both the residential and non-residential scenarios. Human bioavailable concentrations (PBET) were much lower than pseudo-total concentrations. The Hazardous Index of NCR (HI (NCR)) for the PBET in the studied soils was 67% and 94% less than that for pseudo-total concentration, respectively, under the non-residential and residential scenarios. Similarly, CR for the PBET was also 65% and 93% less for the two soils. The concentration of metal(loid)s accumulated in the DGT resin was highly correlated with the PBET-extractable concentration (R² > 0.649). Therefore, for both the CR and HI (NCR), the DGT-calculated risk was linearly related to the PBET-calculated risk for the studied soils under both scenarios. The results suggest that DGT uptake and PBET-extracted concentrations are good surrogates for risk estimation and that both J1 and J2 soils require remediation before their use for residential or non-residential purposes.     

X-Ray Diffractometric Studies on Starches

A linear amylodextrin (average degree of polymerization 12.6) from sweetpotato was crystallized at different temperatures and from different concentrations of solution, and the crystalline type of the recrystallized amylodextrin was examined by X-ray diffraction. It was shown that the crystal type was dependent on the crystallization conditions. The conditions required for the formation of A-, C- and B-type crystals were limited by the following functional relations: 2.5T+C>84, 72<2.5T+C<84, and 2.5T+C<72, respectively, where T is the temperature (°C) at which the amylodextrin was crystallized and C is the concentration (%) of the amylodextrin solution. This relation showed that high temperatures and high concentrations of amylodextrin were favorable for A-type crystal formation and low temperatures and concentrations for B-type crystals, and that the type of crystals formed was more affected by temperature than concentration of the solution.     

Insight towards the conserved water mediated recognition of catalytic and structural Zn+2 ions in human Matrix Metalloproteinase-8 enzyme: A study by MD-simulation methods

Human matrix metalloproteinase-8 (hMMP-8) plays a important role in the progression of colorectal cancer, metastasis, multiple sclerosis and rheumetoid arthritis. Extensive MD-simulation of the PDB and solvated structures of hMMP-8 has revealed the presence of few conserved water molecules around the catalytic and structural zinc (ZnC and ZnS) ions. The coordination of two conserved water molecules (W and WS) to ZnS and the H-bonding interaction of WS to S151 have indicated the plausible involvement of that metal ion in the catalytic process. Beside this the coupling of ZnC and ZnS metal ions (ZnC – W_H (W₁)…..W₂ ….H₁₆₂ - ZnS) through two conserved hydrophilic centers (occupied by water molecules) may also provide some rational on the recognition of two zinc ions which were separated by ~13 Å in their X-ray structures. This unique recognition of both the Zn⁺² ions in the enzyme through conserved water molecules may be implemented/ exploited for the design of antiproteolytic agent using water mimic drug design protocol.     

Yeasts and yeast-like fungi in tap water and groundwater,and their transmission to household appliances

In the present study we describe the occurrence of fungi in 100 tap water and 16 groundwater samples from Slovenia. We used culture-dependent and culture-independent techniques. 28 fungal species belonging to 16 genera were isolated with selected culturing conditions, targeting human opportunistic yeasts and yeast-like fungi. Of special concern was the detection of Aureobasidium melanogenum, Exophiala dermatitidis, Rhinocladiella similis, Candida parapsilosis and Rhodotorula mucilaginosa. The DGGE analysis of ITS1 rDNA revealed from 6 to 16 bands hypothetically corresponding to different taxa, while pyrosequencing showed the presence of Aspergillus and Exophiala. According to the statistic machine learning methodology, the profile of fungi in water is determined by the concentration of calcium and magnesium ions and the presence of nitrate. Exophiala spp., C. parapsilosis and R. mucilaginosa are known as dominant contaminants of household appliances. It appears that they are transferred with water to dishwashers and washing machines, where they subsequently proliferate.     

Tracing the toxic ions of an endodontic tricalcium silicate-based sealer in local tissues and body organs

BackgroundThis study aimed to track the toxic ions released by MTA Fillapex, BioRoot RCS, and an experimental tricalcium silicate-based sealer (CEO) into local and distant tissues as well as to investigate their potential adverse effects. In addition, the chemical constituents of the sealers were also evaluated. The main components of the dry powders, pastes, and mixed sealers were characterized.Material and methodsDry powder and sealer discs were each set for 72 h and their main components were characterized by energy dispersive X-ray spectroscopy. Polyethylene tubes filled with sealers were used to measure silicon and calcium ions. Polyethylene tubes filled with sealers or empty tubes were implanted into the dorsal connective tissue of Wistar rats. On days 7, 15, 30, and 45, the animals were euthanized and their brains, livers, kidneys, and subcutaneous tissues were removed and processed to determine the concentrations of chromium, cobalt, copper, lead, iron, magnesium and nickel using an inductively coupled plasma optical emission spectrometer.ResultsThe main compounds in all sealers were carbon, oxygen, silicon, and calcium. MTA Fillapex release more Si while highest levels of Si were found in presence of BioRoot. The release of Si and Ca ions promoted by MTA Fillapex raise by time. No traces of cobalt, chromium, or magnesium were detected in any tissue. Irrespective of the sealer, no traces of copper and lead were found in the subcutaneous tissue; however, they were observed in the organs. The highest concentration of iron was identified in the liver. All sealers exhibited similar nickel traces in the brain, kidney, and liver except for MTA Fillapex, which demonstrated levels higher than CEO in the subcutaneous tissue on day 7. Tracing nickel ions over time revealed that lowest concentrations were found in subcutaneous tissue.ConclusionTaken together, our data demonstrate that CEOs have chemical compositions similar to those of other commercial sealers. Furthermore, none of them exhibited a threat to systemic health. Moreover, the minimal amounts of iron and nickel detected were not related to the sealers.     

Effect of some extrinsic factors on the respiratory metabolism of the freshwater Leech,Poecilobdella viridis: Oxygen tension,pH and salt concentrations

The effect of oxygen tension, pH and salt concentrations on the respiratory metabolism of the freshwater leech, Poecilobdella viridis has been studied. The respiratory rate increased significantly (p < 0.05) with progressive elevation of the oxygen tension of the medium and decreased significantly (p < 0.05) in both acidic and alkaline media. The respiratory rate was enhanced significantly (p < 0.05) as the salt concentration of the medium increased. Functional significance of these trends to the leech in counteracting the environmental eddies is briefly discussed.     

栽培条件对灵芝子实体中四种重金属含量的影响

以不同灵芝品种、不同栽培基质、不同栽培方式、不同生长时期获得的菌草灵芝和木屑灵芝为原料,对栽培基质及灵芝子实体中铅、砷、汞、镉4种重金属的含量参照国际标准进行检测,结果表明虽然菌草栽培基质中重金属含量高于木屑栽培基质,但菌草灵芝对重金属富集率远低于木屑灵芝,成熟期的菌草灵芝与木屑灵芝中的重金属含量均低于农业行业标准和国家标准。因此菌草可以替代木屑用作灵芝栽培的营养来源。     

Retarded Charge–Carrier Recombination in Photoelectrochemical Cells from Plasmon‐Induced Resonance Energy Transfer

N‐type metal oxides such as hematite (α‐Fe₂O₃) and bismuth vanadate (BiVO₄) are promising candidate materials for efficient photoelectrochemical water splitting; however, their short minority carrier diffusion length and restricted carrier lifetime result in undesired rapid charge recombination. Herein, a 2D arranged globular Au nanosphere (NS) monolayer array with a highly ordered hexagonal hole pattern (hereafter, Au array) is introduced onto the surface of photoanodes comprised of metal oxide films via a facile drying and transfer‐printing process. Through plasmon‐induced resonance energy transfer, the Au array provides a strong electromagnetic field in the near‐surface area of the metal oxide film. The near‐field coupling interaction and amplification of the electromagnetic field suppress the charge recombination with long‐lived photogenerated holes and simultaneously enhance the light harvesting and charge transfer efficiencies. Consequently, an over 3.3‐fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) is achieved for the Au array/α‐Fe₂O₃. Furthermore, the high versatility of this transfer printing of Au arrays is demonstrated by introducing it on the molybdenum‐doped BiVO₄ film, resulting in 1.5‐fold higher photocurrent density at 1.23 V versus RHE. The tailored metal film design can provide a potential strategy for the versatile application in various light‐mediated energy conversion and optoelectronic devices.