Synthesis, crystal structure, DNA binding and cleavage activities of oximato bridged cationic dinuclear copper(II) complex having labile ligands

Oximato bridged dinuclear copper(II) complex Cu(L)(CH3OH)](2)(ClO4)(2) with an oxime-Schiff base ligand, viz. 3-2-(dimethylamino)ethyl]imino]-2-butanoneoxime (HL), has been synthesized and structurally characterized. The dinuclear copper(II) complex crystallizes in monoclinic space group P2(1)/n with the unit cell parameters, a = 13.3564(9) angstrom, b = 12.0821(8) angstrom, c = 17.5045(11) angstrom, beta = 90.097, V = 2824.8(3) angstrom(3), Z = 4, R = 0.0769. The complex shows quasi-reversible cyclic voltammetric response at 0.844V (Delta E-p = 276 mV) at 100 mVs(-1). The binding studies of the complex with calf thymus DNA has been investigated using absorption spectrophotometry. Cleavage activity of the complex has been carried out on double stranded pBR 322 plasmid DNA by using gel electrophoresis experiments in the absence and in the presence of the oxidant, viz., H2O2.

Heat-labile enterotoxin: beyond G(m1) binding.

Enterotoxigenic Escherichia coli (ETEC) is a significant source of morbidity and mortality worldwide. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which is structurally and functionally similar to cholera toxin. LT consists of five B subunits carrying a single catalytically active A subunit. LTB binds the monosialoganglioside G(M1), the toxin's host receptor, but interactions with A-type blood sugars and E. coli lipopolysaccharide have also been identified within the past decade. Here, we review the regulation, assembly, and binding properties of the LT B-subunit pentamer and discuss the possible roles of its numerous molecular interactions.

Labile coordination dendrimers

Addition of anionic benzylsulfate dendrons to dynamic mixtures of Ag+ and triphosphine ligands results in the assembly of loosely-bonded cage-core dendrimers.

Labile ferroelastic nanodomains in bilayered ferroelectric thin films

Bilayered Pb(Zr((1-x)),Ti(x))O(3) ferroelectric thin film heterostructures show complex ferroelastic nanodomain patterns. These ferroelastic nanodomains exist only in the upper layer, and hence are able to move under the application of an external electric field. Quantitative analysis reveals an enhanced piezoelectric coefficient of similar to 220 pm V(-1), rendering them attractive for a variety of electromechanical devices.

Assessing the Labile Arsenic Pool in Contaminated Paddy Soils by Isotopic Dilution Techniques and Simple Extractions

Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils.

Rapid and nondestructive measurement of labile Mn, Cu, Zn, Pb and As in DGT by using field portable-XRF

The technique of diffusive gradients in thin films (DGT) is often employed to quantify labile metals in situ; however, it is a challenge to perform the measurements in-field. This study evaluated the capability of field-portable X-ray fluorescence (FP-XRF) to swiftly generate elemental speciation information with DGT. Biologically available metal ions in environmental samples passively preconcentrate in the thin films of DGT devices, providing an ideal and uniform matrix for XRF nondestructive detection. Strong correlation coefficients (r > 0.992 for Mn, Cu, Zn, Pb and As) were obtained for all elements during calibration. The limits of quantitation (LOQ) for the investigated elements of FP-XRF on DGT devices are 2.74 for Mn, 4.89 for Cu, 2.89 for Zn, 2.55 for Pb, and 0.48 for As (unit: µg cm(-2)). When Pb and As co-existed in the solution trials, As did not interfere with Pb detection when using Chelex-DGT. However, there was a significant enhancement of the Pb reading attributed to As when ferrihydrite binding gels were tested, consistent with Fe-oxyhydroxide surfaces absorbing large quantities of As. This study demonstrates the value of the FP-XRF technique to rapidly and nondestructively detect the metals accumulated in DGT devices, providing a new and simple diagnostic tool for on-site environmental monitoring of labile metals/metalloids

A cleavable network based on crosslinked star polymers containing acid-labile diacetal crosslinks: Synthesis, characterization and hydrolysis

A hydrolyzable model network comprising interconnected star polymers was prepared by the sequential group transfer polymerization of methyl methacrylate and the acid-labile diacetal-based dimethacrylate crosslinker bis[(2-methacryloyloxy)ethoxymethyl] ether. in contrast to other polymer networks previously synthesized by our group, all the branching points of this polymer network were found to hydrolyze under mildly acidic conditions, giving a linear copolymer with the theoretically expected molecular weight and composition. The ease of hydrolysis of this polymer network renders it a good candidate for use in the biomedical field. The characterization of the synthesized network, its linear and star polymer precursors and the hydrolysis products of the network and its precursors, by a variety of techniques, established the successful synthesis and hydrolysis of this well-defined polymer nanostructure.

In situ, high-resolution imaging of labile phosphorus in sediments of a large eutrophic lake

Understanding the labile status of phosphorus (P) in sediments is crucial for managing a eutrophic lake, but it is hindered by lacking in situ data particularly on a catchment scale. In this study, we for the first time characterized in situ labile P in sediments with the Zr-oxide diffusive gradients in thin films (Zr-oxide DGT) technique at a two-dimensional (2D), submillimeter resolution in a large eutrophic lake (Lake Taihu, China, with an area of 2338km²). The concentration of DGT-labile P in the sediment profiles showed strong variation mostly ranging from 0.01 to 0.35mgL^-1 with a considerable number of hotspots. The horizontal heterogeneity index of labile P varied from 0.04 to 4.5. High values appeared at the depths of 0-30mm, likely reflecting an active layer of labile P under the sediment-water interface (SWI). Concentration gradients of labile P were observed from the high-resolution 1D DGT profiles in both the sediment and overlying water layers close to the SWI. The apparent diffusion flux of P across the SWI was calculated between -21 and 65ngcm^-2d^-1, which showed that the sediments tended to be a source and sink of overlying water P in the algal- and macrophyte-dominated regions, respectively. The DGT-labile P in the 0-30mm active layer showed a better correlation with overlying water P than the labile P measured by ex situ chemical extraction methods. It implies that in situ, high-resolution profiling of labile P with DGT is a more reliable approach and will significantly extend our ability in in situ monitoring of the labile status of P in sediments in the field.

FoodCAP: acid-labile protein adducts of heterocyclic amines in human blood are not viable biomarkers of HCA dietary exposure

Intake of heterocyclic amines (HCAs, carcinogens produced during cooking of meat/fish, the most abundant being PhIP, DiMeIQx and MeIQx) is influenced by many factors including type/thickness of meat and cooking method/temperature/duration. Thus, assessment of HCA dietary exposure is difficult. Protein adducts of HCAs have been proposed as potential medium-term biomarkers of exposure, e.g. PhIP adducted to serum albumin or haemoglobin. However, evidence is still lacking that HCA adducts are viable biomarkers in humans consuming normal diets. The FoodCAP project, supported by World Cancer Research Fund, developed a highly sensitive mass spectrometric method for hydrolysis, extraction and detection of acid-labile HCAs in blood and assessed their validity as biomarkers of exposure. Multiple acid/alkaline hydrolysis conditions were assessed, followed by liquid-liquid extraction, clean-up by cation-exchange SPE and quantification by UPLC-ESI-MS/ MS. Blood was analysed from volunteers who completed food diaries to estimate HCA intake based on the US National Cancer Institute’s CHARRED database. Standard HCAs were recovered quantitatively from fortified blood. In addition, PhIP/MeIQx adducts bound to albumin and haemoglobin prepared in vitro using a human liver microsome system were also detectable in blood fortified at low ppt concentrations. However, except for one sample (5pg/ml PhIP), acid-labile PhIP, 7,8-DiMeIQx, 4,8-DiMeIQx and MeIQx were not observed above the 2pg/ml limit of detection in plasma (n=35), or in serum, whole blood or purified albumin, even in volunteers with high meat consumption (nominal HCA intake >2µg/day). It is concluded that HCA blood protein adducts are not viable biomarkers of exposure. Untargeted metabolomic analyses may facilitate discovery of suitable markers.

Acid-labile protein-adducted heterocyclic aromatic amines in human blood are not viable biomarkers of dietary exposure: A systematic study.

Heterocyclic aromatic amines (HCA) are carcinogenic mutagens formed during cooking of protein-rich foods. HCA residues adducted to blood proteins have been postulated as biomarkers of HCA exposure. However, the viability of quantifying HCAs following hydrolytic release from adducts in vivo and correlation with dietary intake are unproven. To definitively assess the potential of labile HCA-protein adducts as biomarkers, a highly sensitive UPLC-MS/MS method was validated for four major HCAs: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx). Limits of detection were 1e5 pg/ml plasma and recoveries 91e115%. Efficacy of hydrolysis was demonstrated by HCA-protein adducts synthesised in vitro. Plasma and 7-day food diaries were collected from 122 fasting adults consuming their habitual diets. Estimated HCA intakes ranged from 0 to 2.5 mg/day. An extensive range of hydrolysis conditions was examined for release of adducted HCAs in plasma. HCA was detected in only one sample (PhIP, 9.7 pg/ml), demonstrating conclusively for the first time that acid-labile HCA adducts do not reflect dietary HCA intake and are present at such low concentrations that they are not feasible biomarkers of exposure. Identification of biomarkers remains important. The search should concentrate on stabilised HCA peptide markers and use of untargeted proteomic and metabolomic approaches.