Enhanced selectivity for acidic contaminants in drinking water: From suspect screening to toxicity prediction

A novel analytical workflow for suspect screening of organic acidic contaminants in drinking water is presented, featuring selective extraction by silica-based strong anion-exchange solid-phase extraction, mixed-mode liquid chromatography-high resolution accurate mass spectrometry (LC-HRMS), peak detection, feature reduction and compound identification. The novel use of an ammonium bicarbonate-based elution solvent extended strong anion-exchange solid-phase extraction applicability to LC-HRMS of strong acids. This approach performed with consistently higher recovery and repeatability (88 ± 7 % at 500 ng L^-1), improved selectivity and lower matrix interference (mean = 12 %) over a generic mixed-mode weak anion exchange SPE method. In addition, a novel filter for reducing full-scan features from fulvic and humic acids was successfully introduced, reducing workload and potential for false positives. The workflow was then applied to 10 London municipal drinking water samples, revealing the presence of 22 confirmed and 37 tentatively identified substances. Several poorly investigated and potentially harmful compounds were found which included halogenated hydroxy-cyclopentene-diones and dibromomethanesulfonic acid. Some of these compounds have been reported as mutagenic in test systems and thus their presence here requires further investigation. Overall, this approach demonstrated that employing selective extraction improved detection and helped shortlist suspects and potentially toxic chemical contaminants with higher confidence.

Hand-portable HPLC with broadband spectral detection enables analysis of complex polycyclic aromatic hydrocarbon mixtures

Polycyclic aromatic hydrocarbons (PAHs) are considered priority hazardous substances due to their carcinogenic activity and risk to public health. Strict regulations are in place limiting their release into the environment, but enforcement is hampered by a lack of adequate field-testing procedure, instead relying on sending samples to centralised analytical facilities. Reliably monitoring levels of PAHs in the field is a challenge, owing to the lack of field-deployable analytical methods able to separate, identify, and quantify the complex mixtures in which PAHs are typically observed. Here, we report the development of a hand-portable system based on high-performance liquid chromatography incorporating a spectrally wide absorption detector, capable of fingerprinting PAHs based on their characteristic spectral absorption profiles: identifying 100% of the 24 PAHs tested, including full coverage of the United States Environmental Protection Agency priority pollutant list. We report unsupervised methods to exploit these new capabilities for feature detection and identification, robust enough to detect and classify co-eluting and hidden peaks. Identification is fully independent of their characteristic retention times, mitigating matrix effects which can preclude reliable determination of these analytes in challenging samples. We anticipate the platform to enable more sophisticated analytical measurements, supporting real-time decision making in the field.

Stereoselective Assembly of Gigantic Chiral Molybdenum Blue Wheels Using Lanthanide Ions and Amino Acids

The synthesis of chiral polyoxometalates (POMs) is a challenge because of the difficulty to induce the formation of intrinsically chiral metal-oxo frameworks. Herein we report the stereoselective synthesis of a series of gigantic chiral Mo Blue (MB) POM clusters 1-5 that are formed by exploiting the synergy between coordinating lanthanides ions as symmetry breakers to produce MBs with chiral frameworks decorated with amino acids ligands; these promote the selective formation of enantiopure MBs. All the compounds share the same framework archetype, based on {Mo₁₂₄Ce₄}, which forms an intrinsically chiral Δ or Λ configurations, controlled by the configurations of functionalized chiral amino acids. The chirality and stability of 1-5 in solution are confirmed by circular dichroism, ¹H NMR, and electrospray ion mobility-mass spectrometry studies. In addition, the framework of the {Mo₁₂₄Ce₄} MB not only behaves as a host able to trap a chiral {Mo₈} cluster that is not accessible by traditional synthesis but also promotes the transformation of tryptophan to kynurenine in situ. This work demonstrates the potential and applicability of our synthetic strategy to produce gigantic chiral POM clusters capable of host-guest chemistry and selective synthetic transformations.

Miller-Urey Spark-Discharge Experiments in the Deuterium World

We designed and conducted a series of primordial-soup Miller-Urey style experiments with deuterated gases and reagents to compare the spark-discharge products of a "deuterated world" with the standard reaction in the "hydrogenated world". While the deuteration of the system has little effect on the distribution of amino acid products, significant differences are seen in other regions of the product-space. Not only do we observe about 120 new species, we also see significant differences in their distribution if the two hydrogen isotope worlds are compared. Several isotopologue matches can be identified in both, but a large proportion of products have no equivalent in the corresponding isotope world with ca. 43 new species in the D world and ca. 39 new species in the H world. This shows that isotopic exchange (the addition of only one neutron) may lead to significant additional complexity in chemical space under otherwise identical reaction conditions.

Spontaneous Assembly of an Organic-Inorganic Nucleic Acid Z-DNA Double-Helix Structure

Herein, we report a hybrid polyoxometalate organic-inorganic compound, Na₂ [(HGMP)₂ Mo₅ O₁₅ ]⋅7 H₂ O (1; where GMP=guanosine monophosphate), which spontaneously assembles into a structure with dimensions that are strikingly similar to those of the naturally occurring left-handed Z-form of DNA. The helical parameters in the crystal structure of the new compound, such as rise per turn and helical twist per dimer, are nearly identical to this DNA conformation, allowing a close comparison of the two structures. Solution circular dichroism studies show that compound 1 also forms extended secondary structures in solution. Gel electrophoresis studies demonstrate the formation of non-covalent adducts with natural plasmids. Thus we show a route by which simple hybrid inorganic-organic monomers, such as compound 1, can spontaneously assemble into a double helix without the need for a covalently connected linear sequence of nucleic acid base pairs.

Overcoming the Crystallization Bottleneck: A Family of Gigantic Inorganic {Pdx }(L) (x=84, 72) Palladium Macrocycles Discovered using Solution Techniques

The {Pd₈₄}^Ac wheel, initially discovered serendipitously, is the only reported giant palladium macrocycle—a unique structure that spontaneously assembles from small building blocks. Analogues of this structure are elusive. A new modular route to {Pd₈₄}^Ac is described, allowing incorporation of other ligands, and a new screening approach to cluster discovery. Structural assignments were made of new species from solution experiments, overcoming the need for crystallographic analysis. As a result, two new palladium macrocycles were discovered: a structural analogue of the existing {Pd₈₄}^Ac wheel with glycolate ligands, {Pd₈₄}^Gly, and the next in a magic number series for this cluster family—a new {Pd₇₂}^Prop wheel decorated with propionate ligands. These findings confirm predictions of a magic number rule for the family of {Pd_x} macrocycles. Furthermore, structures with variable fractions of functional ligands were obtained. Together these discoveries establish palladium clusters as a new class of tunable nanostructures. In facilitating the discovery of species that would not have been discovered by orthodox crystallization approaches, this work also demonstrates the value of solution‐based screening and characterization in cluster chemistry, as a means to decouple cluster formation, discovery, and isolation.

Self-Templating and In Situ Assembly of a Cubic Cluster-of-Clusters Architecture Based on a {Mo24 Fe12 } Inorganic Macrocycle

Engineering self‐templating inorganic architectures is critical for the development of bottom‐up approaches to nanoscience, but systems with a hierarchy of templates are elusive. Herein we describe that the cluster‐anion‐templated (CAT) assembly of a {CAT}⊂{Mo₂₄Fe₁₂} macrocycle forms a giant ca. 220 nm³ unit cell containing 16 macrocycles clustered into eight face‐shared tetrahedral cluster‐of‐clusters assemblies. We show that {CAT}⊂{Mo₂₄Fe₁₂} with different CATs gives the compounds 1–4 for CAT=Anderson {FeMo₆} (1), Keggin {PMo₁₂} (2), Dawson {P₂W₁₈} (3), and {Mo₁₂O₃₆(HPO₃)₂} (4) polyoxometalates. “Template‐free” assembly can be achieved, whereby the macrocycle components can also form a template in situ allowing template to macrocycle to superstructure formation and the ability to exchange the templates. Furthermore, the transformation of template clusters within the inorganic macrocycle {Mo₂₄Fe₁₂} allows the self‐generation of an uncapped {Mo₁₂O₃₆(HPO₃)₂} in compound 4.

Exploring the symmetry, structure, and self-assembly mechanism of a gigantic seven-fold symmetric {Pd₈₄} wheel

The symmetry, structure and formation mechanism of the structurally self-complementary {Pd84} = [Pd84O42(PO4)42(CH3CO2)28](70-) wheel is explored. Not only does the symmetry give rise to a non-closest packed structure, the mechanism of the wheel formation is proposed to depend on the delicate balance between reaction conditions. We achieve the resolution of gigantic polyoxopalladate species through electrophoresis and size-exclusion chromatography, the latter has been used in conjunction with electrospray mass spectrometry to probe the formation of the ring, which was found to proceed by the stepwise aggregation of {Pd6}(-) = [Pd6O4(CH3CO2)2(PO4)3Na(6-n)H(n)](-) building blocks. Furthermore, the higher-order assembly of these clusters into hollow blackberry structures of around 50 nm has been observed using dynamic and static light scattering.

A pyrophosphate-responsive gadolinium(III) MRI contrast agent

This study shows that the relaxivity and optical properties of functionalised lanthanide-DTPA-bis-amide complexes (lanthanide=Gd(3+) and Eu(3+) , DTPA=diethylene triamine pentaacetic acid) can be successfully modulated by addition of specific anions, without direct Ln(3+) /anion coordination. Zinc(II)-dipicolylamine moieties, which are known to bind strongly to phosphates, were introduced in the amide "arms" of these ligands, and the interaction of the resulting Gd-Zn(2) complexes with a range of anions was screened by using indicator displacement assays (IDAs). Considerable selectivity for polyphosphorylated species (such as pyrophosphate and adenosine-5'-triphosphate (ATP)) over a range of other anions (including monophosphorylated anions) was apparent. In addition, we show that pyrophosphate modulates the relaxivity of the gadolinium(III) complex, this modulation being sufficiently large to be observed in imaging experiments. To establish the binding mode of the pyrophosphate and gain insight into the origin of the relaxometric modulation, a series of studies including UV/Vis and emission spectroscopy, luminescence lifetime measurements in H(2) O and D(2) O, (17) O and (31) P NMR spectroscopy and nuclear magnetic resonance dispersion (NMRD) studies were carried out.

Loss of maximum attenuation and receptor reserve for isoprenaline at the beta 2-adrenoceptors of the portal veins of hypertensive rats

OBJECTIVE

To test the hypothesis that vascular beta 2-adrenoceptor hyporesponsiveness in spontaneously hypertensive rats (SHR) is not induced by increased blood pressure or venous hypertrophy.

DESIGN

We compared the attenuating effects or isoprenaline, sodium nitroprusside and verapamilon the portal veins from Wistar-Kyoto (WKY) rats and SHR. studied the effects of slowly reversible beta-adrenoceptor antagonists, bromoacetylalprenololmenthane (BAAM) and ICI 147798, on the isoprenaline responses in order to determine the affinity and fractional beta 2-adrenoceptor occupancy-response relationships for isoprenaline.

RESULTS

The SHR portal veins did not develop hypertrophy. There was a small reduction in the sensitivity to isoprenaline and a marked reduction in the maximum attenuation of hypertension caused by isoprenaline. The sensitivity and efficacy of sodium nitroprusside and verapamil were not altered by hypertension. BAAM and ICI 147798 inhibited the isoprenaline responses and reduced the maximum attenuation to isoprenaline. In the WKY rat portal vein the dissociation constant (KA) values for isoprenaline were independent of BAAM concentration, and was 1.78 +/- 0.32 x 10(-7) mol/l. Similar isoprenaline KA values were obtained from the ICI 147798 data and in the SHR portal vein. In the WKY rat portal vein, from the BAAM data, it was calculated that isoprenaline produced 50, 95 and 100% maximum responses by occupying 6 +/- 1, 20 +/- 3 and 43 +/- 5% (n = 21) of the available beta 2-adrenoceptors, respectively. Similar occupancy-response relationships were obtained in the WKY rat portal vein from the ICI 147798 data. At each level of isoprenaline response the receptor reserve was significantly smaller in the SHR than it was in the WKY rat portal vein. Thus, from the BAAM data, isoprenaline produced 50, 95 and 100% maximum responses by occupying 14 +/- 3, 33 +/- 6 and 58 +/- 7% (n = 15) of the available SHR portal vein beta 2-adrenoceptors, respectively.

CONCLUSIONS

The SHR portal vein displays a selective beta 2-adrenoceptor hyporesponsiveness in the absence of a raised blood pressure or hypertrophy. This beta 2-adrenoceptor-associated hyporesponsiveness consisted of a marked loss of maximum attenuation in response to isoprenaline and of beta 2-adrenoceptor reserve for isoprenaline responses.

Functional beta-adrenoceptors in the left atrium of normotensive and hypertensive rats

1. The aim of the study was to characterize the functional beta 1-and beta 2-adrenoceptors of the rat left atrium and to investigate how these functional beta-adrenoceptor responses were altered in hypertension. The contractile responses of the left atrium from Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats to isoprenaline, T-0509 and procaterol were characterized. Subsequently, the effects of selective beta 1-(bisoprolol) and beta 2 (ICI 118,551)-adrenoceptor antagonists were investigated on these responses. 2. The maximal combined contractile responses of the rat left atrium to cardiac stimulation and CaCl2, isoprenaline, T-0509 or procaterol were not altered by hypertension. 3. The sensitivities to CaCl2 (pD2 on WKY left atrium = 2.99), isoprenaline (8.82) and T-0509 (8.84) were not altered by hypertension. There was an increase in sensitivity to procaterol from a pD2 value of 7.21 to 7.61 in the left atrium of the SH rat. 4. The basal tension induced by cardiac stimulation alone was inhibited by bisoprolol at > or = 10(-8) M and by ICI 118,551 at > or = 10(-7) M and this inhibitory effect is probably due to membrane stabilizing activity. 5. The pKB values for bisoprolol against isoprenaline, T-0509 and procaterol on the WKY were 8.43, 8.68 and 8.18, respectively, and were not different from SH rat left atrium. 6. The pKB value for ICI 118,551 against isoprenaline was increased from 7.06 on the WKY to 7.44 on the SH rat left atrium. The pKB values for ICI 118,551 against T-0509 and procaterol on the WKY were 7.18 and 8.14, respectively and were not significantly different from the SH rat left atrium values. 7. These results suggest that: (a) procaterol stimulates the beta 1-, in addition to, the beta 2-adrenoceptors of the rat left atrium; (b) functional beta 1-adrenoceptors are not altered in hypertension, and (c) there is probably an increase in the affinity of procaterol and isoprenaline for the beta 2-adrenoceptors which underlies the small increase in the functional beta 2-adrenoceptor response in hypertension.

Alprenolol and bromoacetylalprenololmenthane are competitive slowly reversible antagonists at the beta 1-adrenoceptors of rat left atria

We studied the effects of alprenolol and bromoacetylalprenololmenthane (BAAM) on rat left atria. Alprenolol and BAAM at 10(-7), 3 x 10(-7), and 10(-6) M inhibited the cardiac stimulation response slightly, which is indicative of membrane-stabilizing activity independent of beta-adrenoceptor blockade. This membrane-stabilizing activity was readily reversible. Alprenolol and BAAM also caused surmountable antagonism of isoprenaline responses, and this beta 1-adrenoceptor antagonism was slowly reversible. Inhibition of the isoprenaline responses with alprenolol and BAAM at 10(-6) M was at equilibrium after 60 min, which is indicative of reversible antagonism. We conclude that alprenolol and BAAM are competitive slowly reversible beta 1-adrenoceptor antagonists on rat left atria.

Characterization of the antagonism with metoprolol, ICI 147,798, pindolol, mepindolol and bopindolol on the responses of the rat left atria to isoprenaline

The aim of the study was to determine whether the antagonism with pindolol, mepindolol and bopindolol at the beta 1-adrenoceptor of the rat left atria, a tissue with plenty of spare beta 1-adrenoceptors for isoprenaline maximum responses, was readily reversible or not. The effects of these drugs were compared to those of metoprolol, a readily reversible, and of ICI 147,798, an irreversible beta-adrenoceptor antagonist. Metoprolol at 10(-7) and 10(-6) M, ICI 147,798, pindolol, bopindolol (all at 10(-8) and 10(-7) M) and mepindolol at 10(-9) and 10(-8) M inhibited the cardiac stimulation responses to a small extent, which is indicative of membrane stabilizing activity, and also caused surmountable antagonism of isoprenaline responses. The inhibitory effects on the isoprenaline responses of metoprolol and pindolol were readily reversible, that of mepindolol was slowly reversible and those of ICI 147,798 and bopindolol were not reversed in 3 h. The inhibitory effects on isoprenaline responses of metoprolol at 10(-6) M, pindolol and bopindolol at 10(-7) M and mepindolol at 10(-8) M were at equilibrium, which is indicative of reversible, whereas the inhibitory effects of ICI 147,798 were increased, which is indicative of irreversible antagonism, when the beta-blocker treatment time was increased from 1 to 2 h. We conclude that the antagonism with pindolol at the beta 1-adrenoceptors of the rat left atria is readily reversible, that of mepindolol is slowly reversible and that of bopindolol is very slowly reversible.