Toxic Ions Research Articles

γ-Aminobutyric acid (GABA) and ectoine (ECT) impacts with and without AMF on antioxidants, gas exchange attributes and nutrients of cotton cultivated in salt affected soil

Salinity stress is one of the major hurdles in agriculture which adversely affects crop production. It can cause osmotic imbalance, ion toxicity that disrupts essential nutrient balance, impaired nutrient uptake, stunted growth, increased oxidative stress, altered metabolism, and diminished crop yield and quality. However, foliar application of osmoprotectant is becoming popular to resolve this issue in crops. These osmoprotectants regulate the cellular osmotic balance and protect plants from the detrimental effects of high salt concentrations. Furthermore, the role of arbuscular mycorrhizae (AMF) is also established in this regard. These AMF effectively reduce the salinity negative effects by improving the essential nutrient balance via the promotion of root growth. That’s why keeping in mind the effectiveness of osmoprotectants current study was conducted on cotton. Total of six levels of γ-Aminobutyric acid (GABA = 0 mM, 0. 5 mM, and 1 mM) and ectoine (ECT = 0 mM, 0.25 mM, and 0.5 mM) were applied as treatments in 3 replications. Results showed that 0.5 mM γ-Aminobutyric acid and ectoine performed significantly best for the improvement in cotton growth attributes. It also caused significant enhancement in K and Ca contents of the leaf, stem, bur, and seeds compared to the control. Furthermore, 0.5 mM γ-Aminobutyric acid and ectoine also caused a significant decline in Cl and Na contents of leaf, stem, bur, and seeds of cotton compared to control under salinity stress. A significant enhancement in chlorophyll contents, gas exchange attributes, and decline in electrolyte leakage validated the effectiveness of 0.5 mM γ-Aminobutyric acid and ectoine over control. In conclusion, 0.5 mM γ-Aminobutyric acid and ectoine have the potential to mitigate the salinity stress in cotton.

B. subtilis CNBG-PGPR-1 induces methionine to regulate ethylene pathway and ROS scavenging for improving salt tolerance of tomato.

Soil salinity severely threatens plant growth and crop yields. The utilization of PGPR is an effective strategy for enhancing plant salt tolerance, but the mechanisms involved in this process have rarely been reported. In this study, we investigated the effects of Bacillus subtilis CNBG-PGPR-1 on improving plant salt tolerance and elucidated the molecular pathways involved. The results showed that CNBG-PGPR-1 significantly improved the cellular homeostasis and photosynthetic efficiency of leaves and reduced ion toxicity and osmotic stress caused by salt in tomato. Transcriptome analysis uncovered that CNBG-PGPR-1 enhanced plant salt tolerance through the activation of complex molecular pathways, with plant hormone signal transduction playing an important role. Comparative analysis and pharmacological experiments confirmed that the ethylene pathway was closely related to the beneficial effect of CNBG-PGPR-1 on improving plant salt tolerance. Furthermore, we found that methionine, a precursor of ethylene synthesis, significantly accumulated in response to CNBG-PGPR-1 in tomato. Exogenous L-methionine largely mimicked the beneficial effects of CNBG-PGPR-1 and activated the expression of ethylene pathway-related genes, indicating CNBG-PGPR-1 induces methionine accumulation to regulate the ethylene pathway in tomato. Finally, CNBG-PGPR-1 reduced salt-induced ROS by activating ROS scavenger-encoding genes, mainly involved in GSH metabolism and POD-related genes, which were also closely linked to methionine metabolism. Overall, our studies demonstrate that CNBG-PGPR-1-induced methionine is a key regulator in enhancing plant salt tolerance through the ethylene pathway and ROS scavenging, providing a novel understanding of the mechanism by which beneficial microbes improve plant salt tolerance.

Irrigation Water – Quality Issues, Limits, and Way Forward

Depending on how groundwater has been collected and used, the severity of the rainfall, and the following aquifer recharge, the quality of irrigation fluids differs between regions, nations, and even towns. In hot, arid regions with limited rainfall, the salinity of groundwater used for agriculture rises, limiting the variety of crops that may be produced. Therefore, determining the quality of the irrigation water is essential. How well water works for irrigation relies on how much and what kinds of soluble salts are present in the solution. In regard to the four fundamental standards of water salinity (electrical conductivity), sodium risk (sodium adsorption ratio-SAR), residual sodium carbonates (RSC), and ion toxicity, the amount and make-up of soluble salts in a solution are reviewed. We talk about the risks associated with boron and chlorides. For convenience, several plant species' boron tolerance levels are given. The updated water quality diagram created by the US Salinity Laboratory Staff in 1954 is the most significant section of this review. The salinity of most irrigation fluids is more than 2250 S cm-1, which is not represented in this picture. The water classification diagram was expanded to include salinities up to 30,000 S cm-1 in order to handle EC values larger than 2250 S cm-1. The categories for salinity and sodicity presented here can be used to select and manage crops in an educated manner. Methods for controlling water sodicity with gypsum and lowering water salinity by combining different waters are described with examples.

The role of melatonin in regulating horticultural crop production under various abiotic stresses

Horticultural crops are very important component of our food chain, and their production is highly sensitive to different soil related abiotic stresses (SRAS). These stresses reduce plant growth and development by reducing seed germination (SG), seedling establishment, photosynthesis, reproduction, thus reduce fruit yield and quality. Nonetheless application of plant growth regulators has been shown a very promising technique to confer SRAS tolerance in horticultural crops. Melatonin (Mel)-a high conserved and stress regulatory molecule regulates a plethora of stress adaptive responses in plants. This paper summarizes the current state of knowledge of Mel involvement in regulating stress adaptive responses under SRAS. The major topic covered in this review included: (i) the effects of exogenous Mel application on seed germination, photosynthesis, flowering, and fruit yield under different SRAS, (ii) Mel crosstalk with stress regulatory mechanism to confer stress tolerance in horticultural crops. Latter topic further discussed the role of Mel in regulating (i) redox regulation, (ii) ionic homeostasis, and (iii) hormonal regulation. We show that Mel regulates stress adaptive responses and improves plant growth by allowing the direct scavenging of ROS, up-regulation of H+-ATPase activity and vacuolar sequestration of toxic ions in cytosol and activation of ROS-Ca2+ hub, which latter prevent the negative effects of ROS and membrane depolarization on the ROS-activated and voltage-activated ion channels. Such Mel mediated desensitization of ion channels may play a crucial role in reducing stress induced efflux of mineral ions such as K, Zn, Mg from cytosol, thereby improving plant growth. Moreover, Mel may operate in tandem with polyamines to regulate the biosynthesis of different phytohormones. However, studies are required to reveal the molecular identity of genes relating to Mel-polyamine tandem and to light signaling that could directly regulate phytohormone biosynthesis and the interaction of Mel with light signaling in regulating SG.

Sub-picosecond laser surface modification of Ti–Ni alloy and its antibacterial activity

Surface modification of titanium nickelide (Ti–Ni) alloy improves its properties, forming a barrier oxidized/carbonized subsurface layer, which blocks the release of toxic nickel ions. We have modified Ti–Ni alloys by structuring the surface with sub-picosecond laser at different radiation parameters. The modified surface was characterized using scanning electron microscopy and layer-by-layer energy dispersive x-ray spectroscopy. The antibacterial properties of structured surfaces were tested against the planktonic culture of Staphylococcus aureus, and the viability was measured by ‘Live/Dead’ microbiological staining method.

Synthesis and catalytic performance of wood cellulose nanofibers grafted with polylactic acid in rare-earth complexes based on tetrazole carboxylic acids

Stannous octanoate [Sn(Oct)2] and 4-dimethylamino pyridine (DMAP) were used to catalyze the synthesis of amphiphilic cellulose-based graft copolymers, but the acute toxicity of tin ions and DMAP prompts the need for the application of less harmful catalysts. Herein, green catalyst complexes 1–3 [M(H0.5L)2(H2O)5]·2(H2O) (M = Sm, 1; M = Nd, 2; M = Eu, 3; H2L = 4-(3-(tetrazol-5-yl)pyridin-5-yl)benzoic acid) were synthesized, and their properties were systematically investigated. Single-crystal X-ray diffraction showed that the complexes possessed a zero-dimensional structure, while the thermogravimetry and scanning electron microscopy results confirmed their stability after heating at 110 °C for 10 h. Using complexes 1–3 and DMAP as the catalysts, CNFs were grafted with l-lactide via homogeneous ring-opening polymerization to form wood cellulose nanofibers grafted with l-lactide (WGLAs), and the effects of the ratio of wood cellulose nanofibers (WCNFs) to l-lactide ([AGU]/[LA]) and catalyst dosage were studied. The polymerization followed the coordination–insertion mechanism. Under comparable reaction conditions, the grafting ratio of WGLA-1 reached 84.7 %, and the grafting ratio of complex 1 was found to be higher than those achieved using DMAP. WGLAs demonstrated good thermal stability without cytotoxicity, and the residual catalysts in the WGLAs exhibited fluorescence characteristics. Overall, amphiphilic cellulose-based materials with fluorescence emission offered a promising modification strategy to prepare high-performance polymer composites for agriculture and biomedical application.

The critical role of nitrogen in plants facing the salinity stress: Review and future prospective

Salinity stress is a serious abiotic stress that negatively affect the crop growth and development. Mineral nutrient supplementation is considered as an effective strategy to mitigate the adverse effects of salinity. Nitrogen (N) is an important nutrient needed for plants and its application also an effective strategy to mitigate adverse impacts of salinity. Salinity stress disturbs plant physiological, and biochemical functions, antioxidant activities, cellular membranes, antioxidant activities and nutrient uptake thereby cause significant reduction in plant growth and development. The application of N maintains membrane stability, plant water relations, leaf gas exchange characteristics, and protect the plants from oxidative damages which induce the salt tolerance in plants. Besides, this N also improves nutrient uptake and it also induce cellular signaling that mitigate the adverse impacts of salinity. Therefore, it is interesting to understand the role of N in inducing salt tolerance in plants. In present review the mechanisms of N uptake and assimilation in plants under saline conditions are discussed. The present review provides information on how N mitigates ionic toxicity, and oxidative damages and maintains nutrient balance to counter the toxic effects of salinity stress in plants. This review will help the readers to learning more about the role of N in inducing salt tolerance in plants.

Mitigating Salinity Stress and Improving Cotton Productivity with Agronomic Practices

In saline and salinity-affected soils, the global productivity and sustainability of cotton are severely affected by soil salinity. High salt concentrations hinder plant growth and yield formation mainly through the occurrence of osmotic stress, specific ion toxicity, and nutritional imbalance in cotton. A number of agronomic practices have been identified as potential solutions to alleviate the adverse effects induced by salinity. While genetic breeding holds promise in enhancing the salinity tolerance of cotton, agronomic practices that improve the root zone environment, ameliorate soil conditions, and enhance salinity tolerance are currently considered to be more practical. This compressive review highlights the effectiveness of agronomic practices, such as furrow seeding, plastic mulching, their combination, densely planting, and the appropriate application of fertilizer and plant growth regulators, in mitigating the negative impact of salinity on cotton. By implementing these agronomic practices, cotton growers can improve the overall performance and resilience of cotton crops in saline and salinity-affected soils. This review provides valuable insights into practical agronomic measures that can be adopted to counteract the adverse consequences of soil salinity on cotton cultivation.

Differential modulation of metabolites induced by salt stress in rice plants

Salinity is one of the abiotic stresses that most limit the growth and development of several crops, such as rice (Oryza sativa L.). According to previous studies, two rice cultivars, São Francisco (SF) and BRS Esmeralda (ES), exhibit contrasting salt stress tolerance in which the SF cultivar is more tolerant to salt stress than the ES cultivar at the pre-tillering stage. However, metabolic adjustments induced by differential tolerance remain to be explored. Hence, this study aimed to evaluate these cultivars under 80 mM NaCl assessing primary metabolism and physiological traits in the tillering stage in a not oxygenated nutrient solution. Salinity caused a significant increase of toxic ions negatively affecting plants' growth and photosynthesis parameters in both cultivars. Salinity reduced the total chlorophyll content, chlorophyll a fluorescence paraments, CO2 assimilation, stomatal conductance, and transpiration of both cultivars. On the other hand, carboxylation efficiency was increased only in SF cultivar. Overall, the physiological traits did not show differential tolerance to salinity in the tillering phase. Nevertheless, the metabolites modulation and activation of the GABA shunt in the SF leaves by salt stress were evident. Besides, 26 metabolites were differentially expressed in leaves and five in roots of the cultivars under salinity. Most of them were amino acids and key-sugars. In addition, glucopyranoside, lysine, ornithine, 2-aminoisobutyric, glutamine, arabitol, and 2-oxoglutaric acid were defined as potential biomarkers of salt stress in rice plants.

Soil acidification and salinity: the importance of biochar application to agricultural soils.

Soil acidity is a serious problem in agricultural lands as it directly affects the soil, crop production, and human health. Soil acidification in agricultural lands occurs due to the release of protons (H+) from the transforming reactions of various carbon, nitrogen, and sulfur-containing compounds. The use of biochar (BC) has emerged as an excellent tool to manage soil acidity owing to its alkaline nature and its appreciable ability to improve the soil's physical, chemical, and biological properties. The application of BC to acidic soils improves soil pH, soil organic matter (SOM), cation exchange capacity (CEC), nutrient uptake, microbial activity and diversity, and enzyme activities which mitigate the adverse impacts of acidity on plants. Further, BC application also reduce the concentration of H+ and Al3+ ions and other toxic metals which mitigate the soil acidity and supports plant growth. Similarly, soil salinity (SS) is also a serious concern across the globe and it has a direct impact on global production and food security. Due to its appreciable liming potential BC is also an important amendment to mitigate the adverse impacts of SS. The addition of BC to saline soils improves nutrient homeostasis, nutrient uptake, SOM, CEC, soil microbial activity, enzymatic activity, and water uptake and reduces the accumulation of toxic ions sodium (Na+ and chloride (Cl-). All these BC-mediated changes support plant growth by improving antioxidant activity, photosynthesis efficiency, stomata working, and decrease oxidative damage in plants. Thus, in the present review, we discussed the various mechanisms through which BC improves the soil properties and microbial and enzymatic activities to counter acidity and salinity problems. The present review will increase the existing knowledge about the role of BC to mitigate soil acidity and salinity problems. This will also provide new suggestions to readers on how this knowledge can be used to ameliorate acidic and saline soils.

The uptake, elimination, and toxicity of silver nanoparticles and silver ions in single-species and natural mixed-species bacterial biofilms

In nature, microorganisms predominantly exist as biofilms, which can reduce the bioavailability of toxic metals in water by adsorbing them. In this study, we investigated the adsorption, elimination, and toxicity of silver nanoparticles (AgNPs) and silver nitrate (AgNO3) in biofilms of the model bacterium Escherichia coli and those composed of natural mixed-species (NMS). Biofilms were exposed to different metal concentrations for 72 h, after which, they were transferred to a clean medium for 7 days to study the elimination of AgNPs and Ag+. We found that pseudo-second order kinetics predominated, and adsorption was jointly governed by external mass transfer and intraparticle diffusion. NMS biofilms were much more tolerant to AgNPs and Ag+ than E. coli biofilms, and Ag+ was much more toxic to both the biofilms than AgNPs. The concentrations of proteins, polysaccharides, and internal metabolites like respiratory chain dehydrogenase and cyclic diguanosine monophosphate were 0.3 to 3.7 fold greater in NMS biofilms than in E. coli biofilms, while those of reactive oxygen species and lactate dehydrogenase were 0.6 to 1.1 fold lower in NMS biofilms, highlighting a significant advantage that metal-exposed NMS biofilms enjoy in terms of both structure and metabolic function. These findings improve our understanding of the potential environmental risks of engineered nanoparticles and provide new insights into the bioremediation of nanoparticles-contaminated aquatic environments using biofilms.

Efficient Removal of Cr(VI) by Protonated Amino-Bamboo Char Prepared via Radiation Grafting: Behavior and Mechanism

Biochar is considered to be the most promising substrate for the preparation of environmentally functional materials. The modification of bamboo char can significantly improve the removal rate of toxic ions from wastewater; however, there are few reports that focus on the radiation grafting method. Here, glyceride methacrylate (GMA) is successfully grafted onto bamboo char through electron beam radiation, followed by amination using the existing epoxide group in diethyltriamine, and finally, treated with hydrochloric acid to obtain protonated diethyltriamine-functionalized bamboo char (CDGBC). The results of IR, TG, XRD, and SEM prove the successful fabrication of a CDGBC biosorbent. The results show that the solution pH has a great effect on the adsorption capacity, and a maximum adsorption capacity of 169.13 mg/g is obtained at pH = 2 for Cr(VI). In addition, the adsorption behavior of Cr(VI) onto CDGBC is demonstrated to obey the pseudo-second-order kinetic and Freundlich isotherm models, and thermodynamic analysis exhibits that Cr(VI) adsorption is an endothermic spontaneous process. A possible adsorption mechanism based on the electrostatic interaction, reduction, and surface complexation is proposed, according to the obtained results. This work confirms that radiation-induced grafting modification can effectively transform biochar into a high-performance adsorbent for Cr(VI) removal, offering a new approach to synthesizing an efficient biosorbent.

Stimuli-Responsive Ion Adsorbents for Sustainable Separation Applications.

Stimuli-responsive ion absorbents (SRIAs) with reversible ion adsorption and desorption properties have recently attracted immense attention due to their outstanding functionalities for sustainable separation applications. Over the past decade, a series of SRIAs that respond to single or multiple external stimuli (e.g., pH, gas, temperature, light, magnetic, and voltage) have been reported to achieve excellent ion adsorption capacity and selectivity while simultaneously allowing for their reusability. In contrast to traditional adsorbents that are mainly regenerated through chemical additives, SRIAs allow for reduced chemical and even chemical-free regeneration capacities, thereby enabling environmentally friendly and energy-efficient separation technologies. In this review, we systematically summarize the materials and strategies reported to date for synthesizing single-, dual-, and multiresponsive ion adsorbents. Following a discourse on the fundamental mechanisms that govern their adsorption and desorption under various external stimuli, we provide a concise discussion of the regeneration capacity and application of these responsive ion adsorbents for sustainable water desalination, toxic ion removal, and valuable ion extract and recovery. Finally, we discuss the challenges in developing and deploying these promising multifunctional responsive ion adsorbents together with strategies to overcome these limitations and provide prospects for their future.

Qualidade da água em áreas de barragens subterrâneas do semiárido potiguar

ABSTRACT The federal public agencies have prioritized the financing of underground dams as a strategy to decrease water scarcity in rural semiarid regions in Brazil. The objective of this work was to evaluated water quality in underground dams, for agricultural irrigation purposes, in Rio Grande do Norte, Brazil, at the end of the dry season in 2018 and at the end of the rainy season in 2019. The variables with the greatest impact on water quality were identified through multivariate analysis, using the software Statistica 7.0. The results showed that concentrations of variables correlated with salinity and ion toxicity in water of the dams decreased after the rainy season, whereas those correlated with clogging of localized irrigation systems increased. Salinity, sodicity, and/or toxicity in areas of underground dams were correlated with natural mineralization of geological components of soils; however, they also were affected by rainfall with marine hygroscopic nuclei, presence of rural clusters and corrals, and decomposition of organic matter in the damming area. The variables correlated with salinity presented higher effect on the hydrochemical variability of water within these dams in both sampling periods; electrical conductivity and chloride ions were the most significant variables.

A cytoplasmic chemoreceptor and reactive oxygen species mediate bacterial chemotaxis to copper

Chemotaxis is a widespread strategy used by unicellular and multicellular living organisms to maintain their fitness in stressful environments. We previously showed that bacteria can trigger a negative chemotactic response to a copper (Cu)-rich environment. Cu ion toxicity on bacterial cell physiology has been mainly linked to mismetallation events and reactive oxygen species (ROS) production, although the precise role of Cu-generated ROS remains largely debated. Here, using inductively coupled plasma optical emission spectrometry on cell fractionates, we found that the cytoplasmic Cu ion content mirrors variations of the extracellular Cu ion concentration. ROS-sensitive fluorescent probe and biosensor allowed us to show that the increase of cytoplasmic Cu ion content triggers a dose-dependent oxidative stress, which can be abrogated by superoxide dismutase and catalase overexpression. The inhibition of ROS production in the cytoplasm not only improves bacterial growth but also impedes Cu chemotaxis, indicating that ROS derived from cytoplasmic Cu ions mediate the control of bacterial chemotaxis to Cu. We also identified the Cu chemoreceptor McpR, which binds Cu ions with low affinity, suggesting a labile interaction. In addition, we demonstrate that the cysteine 75 and histidine 99 within the McpR sensor domain are key residues in Cu chemotaxis and Cu coordination. Finally, we discovered that invitro both Cu(I) and Cu(II) ions modulate McpR conformation in a distinct manner. Overall, our study provides mechanistic insights on a redox-based control of Cu chemotaxis, indicating that the cellular redox status can play a key role in bacterial chemotaxis.

Efficacy of Seed Priming Technique on Seed Germination and Plant Growth Under Salt Stress in Oryza sativa

Salinity stress limits agricultural productivity by adversely affecting seed germination and seedling growth. It negatively impacts essential metabolic processes by imposing osmotic and oxidative stress due to ion toxicity. Seed priming is an innovative approach that can ensure seed germination and seedling establishment for ameliorating salinity stress in plants. In this study, response of two popular rice cultivars, PB 1121 and PB 1718 to various priming treatments was evaluated under salt stress. Out of the two, cultivar PB 1718 performed better and showed improved germination, and plant growth when given a priming treatment with Salicylic acid (1mM), KNO3 (1%), Moringa leaf extract (100%) and Neem leaf extract (50%) under salt stress of NaCl (150 mM). In cultivar PB 1121, no significant change was seen in germination indices under salt stress as compared to control. However, Salicylic acid (1mM), KNO3 (1%), Proline (50mM), Moringa leaf extract (100%), MgSO4 (10mM) and Neem leaf extract (50%) treatments resulted in improved root growth.

Melatonin mitigates adverse effects of salinity in stevia through physiological and biochemical adjustments

Stevia is a valuable medicinal plant known for its abundance of sterols, phytochemicals, natural antioxidants, and glycosides-stevioside. Its traditional use extends to the regulation of blood pressure and diabetes. However, the production of stevia faces challenges due to various abiotic stresses, with salinity being a prominent constraint affecting its sustainable productivity. In light of this, the current study was designed to assess the impact of melatonin (MEL) (100 µM) on stevia plants growing under normal and saline conditions (0, 40, 80 and 120 mM NaCl). The findings of this study highlight the significant effect of MEL sprays on stevia growth and yield under saline conditions. MEL supplementation significantly played a crucial role in regulating photosynthetic pigments, net photosynthesis, and stomatal conductance, effectively mitigating the adverse effect of different salinity levels. MEL improved plant defense system by reducing oxidative stress activities such as H2O2 and MDA, which are known indicators of cellular damage caused by salinity stress. Importantly, MEL supplementation also played a significant role in regulating the uptake of sodium (Na+) and potassium (K+) in stevia plants under saline conditions. This regulation of ion uptake helps maintain ion homeostasis and prevents ion toxicity, thus contributing to the overall improvement of stevia plant health and productivity in saline environments. Overall, the results of this study provide valuable insights into the effectiveness of MEL in promoting sustainable stevia production under saline conditions.

In Silico Simulations Reveal Molecular Mechanism of Uranyl Ion Toxicity towards DNA-Binding Domain of PARP-1 Protein.

The molecular toxicity of the uranyl ion (UO22+) in living cells is primarily determined by its high affinity to both native and potential metal-binding sites that commonly occur in the structure of biomolecules. Recent advances in computational and experimental research have shed light on the structural properties and functional impacts of uranyl binding to proteins, organic ligands, nucleic acids, and their complexes. In the present work, we report the results of the computational investigation of the uranyl-mediated loss of DNA-binding activity of PARP-1, a eukaryotic enzyme that participates in DNA repair, cell differentiation, and the induction of inflammation. The latest experimental studies have shown that the uranyl ion directly interacts with its DNA-binding subdomains, zinc fingers Zn1 and Zn2, and alters their tertiary structure. Here, we propose an atomistic mechanism underlying this process and compute the free energy change along the suggested pathway. Our Quantum Mechanics/Molecular Mechanics (QM/MM) simulations of the Zn2-UO22+ complex indicate that the uranyl ion replaces zinc in its native binding site. However, the resulting state is destroyed due to the spontaneous internal hydrolysis of the U-Cys162 coordination bond. Despite the enthalpy of hydrolysis being +2.8 kcal/mol, the overall reaction free energy change is -0.6 kcal/mol, which is attributed to the loss of domain's native tertiary structure originally maintained by a zinc ion. The subsequent reorganization of the binding site includes the association of the uranyl ion with the Glu190/Asp191 acidic cluster and significant perturbations in the domain's tertiary structure driven by a further decrease in the free energy by 6.8 kcal/mol. The disruption of the DNA-binding interface revealed in our study is consistent with previous experimental findings and explains the loss of PARP-like zinc fingers' affinity for nucleic acids.

A Simple Live Cell Imaging "Turn-On" Fluorescence Probe for the Selective and Sensitive Detection of Aqueous Hg2+ Ions.

A simple, efficient, and reversible fluorescent sensor probe, PBA (2,6-dimethyl pyrone barbituric acid conjugate), comprised of a pro-aromatic donor conjugated with a barbituric acid, was developed for the detection of highly toxic mercuric ions. The probe showed high selectivity and "Turn-On" fluorescence response towards Hg2+ among various metal cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, and Pb2+, in both homogeneous and microheterogeneous micelle medium sodium dodecyl sulphate (SDS). The binding stoichiometry, limit of detection (LOD), and binding constant for the PBA-Hg complex were determined. The mechanism of binding was ascertained using the N,N'-dimethylbarbituric acid conjugate of 2,6-dimethylpyran (PDMBA), where no binding interaction by deprotonation is possible. In the presence of cysteamine hydrochloride and trifluoroacetic acid (TFA), the complexation of Hg2+ with PBA was demonstrated to be reversible, indicating its potential for the development of reusable sensors. Moreover, the practical applicability of PBA in monitoring Hg2+ in living cells was also evaluated.

Improvement of Cu and Zr doped Diamond-like carbon coatings on comprehensive performance of Ni-Ti alloy potentially used in braided vascular stent

Wear and corrosion between braided wires will not only release toxic nickel ions, but also cause fatigue fracture of Ni-Ti alloy-based braided stents. In this study, Cu and Zr doped Diamond-like carbon (DLC) film containing Cr intermediate layer and Cr:C gradient layer were prepared with the total thickness of about 2.17 μm and 2.05 μm, respectively. In order to study the improvement of DLC coating on the comprehensive properties of Ni-Ti based stent, the nano-mechanical, tribological, electrochemical corrosion, nickel ion release and cytotoxicity properties were all evaluated. The results showed that the nano hardness and elastic modulus for Zr-DLC film were 12.32 GPa and 138.49 GPa, respectively increased by 192% and 102% compared with bare NiTi. Cu-DLC and Zr-DLC coatings can not only significantly reduce the friction coefficient, but also greatly reduce the wear rate such as by three orders of magnitude in dry sliding condition compared with bare NiTi. Zr-DLC film reduced the icorr value with a reduction amount of 96.1%, with the values of 8.41 × 10−8 and 3.26 × 10−9 A/cm2 for NiTi and Zr-DLC, respectively. After 28 days of soak experiment in phosphate buffer solution, the total nickel ion release amount was only 5.6 ng/L for Cu-DLC and 6.9 ng/L for Zr-DLC, which was reduced by 96.1% and 95.2%, respectively. The relative cell proliferation rate results showed that NiTi and Zr-DLC were both Grade 0, which indicated good cytotoxicity result. However, the cytotoxicity of Cu-DLC reached grade 2 (the relative cell proliferation rate was 71.73%). Based on the above results, Zr-DLC showed good comprehensive performances and was expected to be used as a protective layer on the surface.