Analytical challenges and the development of biomarkers to measure and to monitor the effects of ocean acidification

Changing ocean-carbonate chemistry caused by oceanic uptake of anthropogenic atmospheric carbon dioxide leads to the formation of carbonic acid, thus lowering the pH of the sea with predictions of a decrease from current levels at 8.15 to 7.82 by the end of the century. The exact measurement of subtle pH changes in seawater over time presents significant analytical challenges, as the equilibrium constants are governed by water temperature and pressure, salinity effects, and the existence of other ionic species in seawater.Here, we review these challenges and how pH also affects dissolved inorganic and organic chemicals that affect biological systems. This includes toxic compounds (xenobiotics) as well as chemicals that are beneficial for marine organisms, such as the chemical signals (i.e. pheromones) that are utilized to coordinate animal behavior. We review how combining analytical, molecular and biochemical tools can lead to the development of biosensors to detect pH effects to enable predictive modeling of the ecological consequences of ocean acidification.     

Oral,Direct Thrombin and Factor Xa Inhibitors: The Replacement for Warfarin,Leeches, and Pig Intestines?

To prevent thromboses after surgery, patients have until now had to inject themselves daily with heparin. For stroke prophylaxis in atrial fibrillation, patients take vitamin K antagonists of the coumarin type, which have a narrow therapeutic window and whose dosage must be regularly monitored. In order to improve the standard of therapy in thromboembolic diseases such as deep‐vein thrombosis, pulmonary embolism, and stroke in atrial fibrillation, intensive research has been carried out over the last decade in the search for new, orally active thrombin and factor Xa inhibitors. A number of these compounds are already on the market or are in advanced clinical development; they could revolutionize the anticoagulant market.     

Elucidation of the Active Conformation of Vancomycin Dimers with Antibacterial Activity against Vancomycin‐Resistant Bacteria

Covalently linked vancomycin dimers have attracted a great deal of attention among researchers because of their enhanced antibacterial activity against vancomycin‐resistant strains. However, the lack of a clear insight into the mechanisms of action of these dimers hampers rational optimization of their antibacterial potency. Here, we describe the synthesis and antibacterial activity of novel vancomycin dimers with a constrained molecular conformation achieved by two tethers between vancomycin units. Conformational restriction is a useful strategy for studying the relationship between the molecular topology and biological activity of compounds. In this study, two vancomycin units were linked at three distinct positions of the glycopeptide (vancosamine residue (V), C terminus (C), and N terminus (N)) to form two types of novel vancomycin cyclic dimers. Active NC‐VV‐linked dimers with a stable conformation as indicated by molecular mechanics calculations selectively suppressed the peptidoglycan polymerization reaction of vancomycin‐resistant Staphylococcus aureus in vitro. In addition, double‐disk diffusion tests indicated that the antibacterial activity of these dimers against vancomycin‐resistant enterococci might arise from the inhibition of enzymes responsible for peptidoglycan polymerization. These findings provide a new insight into the biological targets of vancomycin dimers and the conformational requirements for efficient antibacterial activity against vancomycin‐resistant strains.     

Six Coordination Polymers based on 4‐(1H‐Imidazol‐1‐yl)phthalic Acid: Structural Diversities,Magnetism and Luminescence Properties

The coordination polymers (CPs), [Ni(L)(H₂O)₄]_n ( 1 ), [Co(HL)₂(H₂O)₂]_n ( 2 ), {[Cu(L)(H₂O)₃] · H₂O}_n ( 3 ), [Mn(L)(H₂O)₂]_n ( 4 ), [Cd(L)(H₂O)₂]_n ( 5 ), and {[Zn₂(L)₂] · H₂O}_n ( 6 ), were solvothermally synthesized by employing the imidazol‐carboxyl bifunctional ligand 4‐(1H‐imidazol‐1‐yl) phthalic acid (H₂L). Single‐crystal X‐ray diffraction indicated that the L^2–/HL^– ligands display various coordination modes with different metal ions in 1 – 6 . Complexes 1 and 2 show one‐dimensional (1D) chain structures, whereas complexes 3 – 6 show 2D layered structures. The magnetic properties of these complexes were investigated. Complexes 1 and 3 indicate weak ferromagnetic interactions, whereas complexes 2 and 4 demonstrate antiferromagnetic interactions. In addition, luminescence properties of 5 and 6 were measured and studied in detail.     

Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu‐Porphyrin Prepared Through Single‐Crystal to Single‐Crystal Exchange of a Zn Analogue

A solvothermal reaction of Zn(NO₃)₂ ? 6 H₂O, tetra‐(4‐pyridyl)porphyrin (H₂TPyP), and 4,4′‐oxybis(benzoic acid) (H₂OBA) resulted in a new two‐dimensional Zn‐ porphyrin metal–organic framework compound, [Zn₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₆ ( 1 ; DMA=N,N‐dimethylacetamide). The Zn^II ions present in 1 could be exchanged by using a solution of Cu(NO₃)₂ ? 3 H₂O in DMA at room temperature to give [Cu₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₃ ( Cu∈1 ). The extra‐framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent‐free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO₂ into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent‐free conditions, and 3) the three‐component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5‐exo‐dig cyclization to produce the important pharmacophore imidazopyridine.     

Tuning the Electronic Properties and Acid‐Response Behavior of N‐Heteroacene‐Based π‐Conjugated Liquids by Changing the Number of π‐Conjugated Substituents

We have designed and synthesized two room‐temperature‐fluorescent π‐conjugated liquids based on the N‐heteroacene framework ( 1 and 2 ). These two π‐conjugated liquids, which contained one and two thiophene rings, respectively, exhibited different electronic properties and rheology behaviors. Single‐crystal X‐ray analysis of dithiophene‐appended compound 4 revealed that two thiophene rings hindered the interactions of the imino N atoms with acids through the formation of interactions between the S atoms of the thiophene rings and the imino N atoms of the pyrazine group. On the other hand, monothiophene‐appended molecules 1 and 3 each contained an unhindered imino N atom on the opposite site to the thiophene ring. Upon dissolving various acids with different pK_a values in compounds 1 and 2 , these slight structural differences gave rise to marked differences in their acid‐response behaviors, thereby resulting in the emission of variously colored fluorescence in the liquid state. Furthermore, when acids with lower pK_a values was dissolved in compounds 1 and 2 , phase transition occurred from an isotropic liquid state to a self‐organized liquid‐crystalline phase.     

Chromatographic determination,decline dynamic and risk assessment of sulfoxaflor in Asian pear and oriental melon

The dissipation pattern of sulfoxaflor in Asian pear cultivated in an open field conditions and in oriental melon grown under plastic house conditions was each studied in two different locations. Residues in field‐treated samples were determined using liquid chromatography coupled with an ultraviolet detector and confirmed by liquid chromatography–tandem mass spectrometry. A calibration curve for sulfoxaflor was linear over the concentration range 0.1–5.0 mg/L, with a coefficient of determination of 0.9999. The limits of detection and quantification (LOQ) were 0.007 and 0.02 mg/kg, respectively. Recoveries at three fortification levels (LOQ, 10 × LOQ and maximum residue limit) ranged from 70.5 to 86.2%, with a relative standard deviation ≤5.8%. The dissipation half‐lives were 10.8 and 7.9 days in pear and 5.4 and 5.9 days in oriental melon, at sites 1 and 2, respectively. Based on a pre‐harvest residue limit curve, it was predicted that, if the residues at 10 days before harvest in Asian pear are <0.54/0.61 mg/kg and those in oriental melon are <1.43/1.26 mg/kg, then the residue level will be below the maximum residue limit at harvest. Risk assessment at zero days showed a percentage acceptable daily intake of 10.80% in Asian pear and 1.77 and 1.55% in oriental melon, for sites 1 and 2, respectively. These values indicate that the fruits are safe for consumption.     

Residual level of dimethachlon in rice‐paddy field system and cooked rice determined by gas chromatography with electron capture detector

In this study, a modified quick, easy, cheap, effective, rugged and safe method coupled with gas chromatography with electron capture detection was established to determine dimethachlon residues in paddy soil, rice husk, rice straw, brown rice and cooked rice. The limits of quantification of dimethachlon were 0.01 mg/kg for paddy soil, brown rice and cooked rice and 0.02 mg/kg for rice straw and rice husk. The mean recoveries were in the range 78.59–104.7% with relative standard deviation values of <10% for dimethachlon in the five matrices. For field experiments, the final residues of dimethachlon in paddy soil were < 0.05 mg/kg and were < 1.21 mg/kg in rice straw from six sites. The final residues of dimethachlon in the brown rice at 21, 28 and 35 days after spraying from six sites were 0.08–7.58 mg/kg, and 0.16–30.1 mg/kg in rice husk. Our six test sites covered the main rice–producing areas of China. The routine rice cooking process of a Chinese family could apparently increase the removal of dimethachlon in rice compared with brown rice, and the reduction ratios were > 96%.     

Dissipaton Equation of Motion Theory versus Fokker-Planck Quantum Master Equation

The quest of exact and nonperturbative methods on quantum dissipation with nonlinear coupling environments remains in general a great challenge. In this review we present a comprehensive account on two approaches to the entangled system-and-environment dynamics, in the presence of linear-plus-quadratic coupling bath. One is the dissipaton-equation-ofmotion (DEOM) theory that has been extended recently to treat the nonlinear coupling environment. Another is the extended Fokker-Planck quantum master equation (FP-QME) approach that will be constructed in this work, based on its DEOM correspondence. We closely compare these two approaches, with the focus on the underlying quasi-particle picture, physical implications, and implementations.