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The formal cycloaddition adduct of 1,4-benzoquinone with two equivalents of cyclopentadiene is a scaffold with two non-conjugated alkenes. Both alkenes undergo endo [4+2] cycloaddition with a diene to form a rigid U-shaped molecular cleft. Here we show experimental, computational and structural evidence that π interactions between the alkenes affect structural rigidity, Diels–Alder reactivity, cleft formation and host–guest capture.

The core purpose of the current study is to explore the use of Moringa oleifera leaves, to produce a herbal tea with acceptable sensory properties and nutritional properties by utilizing the steam blanching technique, different dehydration temperatures and time, which can be accepted in the Sri Lankan market. Six sets of samples were prepared where temperature and time combinations were 55°C—6 h, 60°C—4.30 h, 65°C—3 h for the unblanched samples & 55°C—6 h, 60°C—5.30 h & 65°C—4 h for the steam blanched samples. These samples were evaluated, employing a trained panel of 5 tea tasters and a semi trained panel of 35 members. The sample code 706 (steam blanched, 65°C—4 h) was selected as the sample with best sensory attributes. The blanched and unblanched samples dried at 65°C were tested for their proximate, mineral, vitamin, antioxidant and phytochemical contents. The effects of steam blanching on these two samples were evaluated & compared. This study highlights that steam blanching significantly increased the carbohydrates, fat, Mn, Fe, vitamin A, vitamin E and the DPPH scavenging activity whereas steam blanching significantly reduced the protein, fiber, Na, K, Ca, Total phenolic contents and flavonoids content but vitamin C, Zn, Cu and Mg contents were unaffected by steam blanching.

The cyanobacterial toxin cylindrospermospin (CYN) was shown to inhibit the eukaryotic protein synthesis apparatus with similar potency in plant and mammalian cell extracts, IC(50) of 334 nM in wheat germ extract and 110 nM in reticulocyte lysate. [(14)C] CYN binding was assessed in reticulocyte lysates, following separation of ribosomes from free toxin on Sephadex G-50 size exclusion columns. While toxin binding was shown to be concentration-dependent (60-600 nM [(14)C] CYN), it did not correlate with ribosome content. The molar ratio of toxin to ribosomes was 0.02:1 at the binding plateau. Significant binding of [(14)C] CYN was identified in both the ribosome fraction (90% total ribosomes) and the first wash fraction eluting from the Sephadex G-50 column, despite the low ribosome content (10% total ribosomes) in the latter. Bound [(14)C] CYN could be partially displaced by incubation with an excess of unlabelled CYN in both the ribosome and wash fractions, indicating a non-covalent linkage. Molecular weight cut-off filters identified that [(14)C] CYN was associated with high molecular weight material100 kDa. These results suggest that CYN's target may not be the ribosome itself, but rather one of the soluble proteins associated with the eukaryotic translation system.

Lyngbya wollei (Farlow ex Gomont) Speziale and Dyck is a common mat-forming benthic cyanobacterium from freshwater habitats. We found that two populations from southeast Queensland (Australia) produce the potent cyanotoxin cylindrospermopsin (CYN) and its analogue, deoxy-cylindrospermopsin (deoxy-CYN). The highest concentrations in environmental samples were 20 and 550 m gg � 1 dry weight for CYN and deoxy-CYN, respectively. A sub-sample maintained in culture for over 16 months yielded concentrations of 33 and 308 m gg � 1 dry weight for CYN and deoxy-CYN, respectively. The concentration of deoxy-CYN in L. wollei was 10–300 times higher than CYN, suggesting that, unlike many other CYN-producing cyanobacteria, the primary compound produced byL. wollei is deoxy-CYN. The production of CYN and deoxy-CYN byL. wollei represents a potential human health risk and an additional source of these toxins in freshwaters. This is the first report of the production of CYN and deoxy-CYN by L. wollei or any species of the Oscillatoriales. # 2006 Elsevier B.V. All rights reserved.

The potentially bis-bidentate ligand 1,4-di-2′-pyridylaminophthalazine (pap), forms mononuclear (Ni(II)), dinuclear (Ni(II), Co(III)) and trinuclear (Ni(II)) complexes, with combined N–N diazine and OH (Ni(II), Co(III)), and H2O (Ni(II)) bridges. The dinuclear and trinuclear Ni(II) complexes exhibit intramolecular antiferromagnetic exchange interactions, from a combination of the exchange effects of both the N–N and `O' bridge groups.

Extracellular copper regulates the DNA binding activity of the CopY repressor of Enterococcus hirae and thereby controls expression of the copper homeostatic genes encoded by the cop operon. CopY has a CxCxxxxCxC metal binding motif. CopZ, a copper chaperone belonging to a family of metallochaperones characterized by a MxCxxC metal binding motif, transfers copper to CopY. The copper binding stoichiometries of CopZ and CopY were determined by in vitro metal reconstitutions. The stoichiometries were found to be one copper(I) per CopZ and two copper(I) per CopY monomer. X-ray absorption studies suggested a mixture of two- and three-coordinate copper in Cu(I)CopZ, but a purely three-coordinate copper coordination with a Cu-Cu interaction for Cu(I)2CopY. The latter coordination is consistent with the formation of a compact binuclear Cu(I)-thiolate core in the CxCxxxxCxC binding motif of CopY. Displacement of zinc, by copper, from CopY was monitored with 2,4-pyridylazoresorcinol. Two copper(I) ions were required to release the single zinc(II) ion bound per CopY monomer. The specificity of copper transfer between CopZ and CopY was dependent on electrostatic interactions. Relative copper binding affinities of the proteins were investigated using the chelator, diethyldithiocarbamic acid (DDC). These data suggest that CopY has a higher affinity for copper than CopZ. However, this affinity difference is not the sole factor in the copper exchange; a charge-based interaction between the two proteins is required for the transfer reaction to proceed. Gain-of-function mutation of a CopZ homologue demonstrated the necessity of four lysine residues on the chaperone for the interaction with CopY. Taken together, these results suggest a mechanism for copper exchange between CopZ and CopY.

High-resolution crystal structures are described for seven macrocycles complexed with HIV-1 protease (HIVPR). The macrocycles possess two amides and an aromatic group within 15-17 membered rings designed to replace N- or C-terminal tripeptides from peptidic inhibitors of HIVPR. Appended to each macrocycle is a transition state isostere and either an acyclic peptide, nonpeptide, or another macrocycle. These cyclic analogues are potent inhibitors of HIVPR, and the crystal structures show them to be structural mimics of acyclic peptides, binding in the active site of HIVPR via the same interactions. Each macrocycle is restrained to adopt a P-strand conformation which is preorganized for protease binding. An unusual feature of the binding of C-terminal macrocyclic inhibitors is the interaction between a positively charged secondary amine and a catalytic aspartate of HIVPR. A bicyclic inhibitor binds similarly through its secondary amine that lies between its component N-terminal and C-terminal macrocycles. In contrast, the corresponding tertiary amine of the N-terminal macrocycles does not interact with the catalytic aspartates. The amine-aspartate interaction induces a 1.5 Angstrom N-terminal translation of the inhibitors in the active site and is accompanied by weakened interactions with a water molecule that bridges the ligand to the enzyme, as well as static disorder in enzyme flap residues. This flexibility may facilitate peptide cleavage and product dissociation during catalysis. Proteases [Aba(67,95)]HIVPR and [Lys(7),Ile(33),Aba(67,95)]- HIVPR used in this work were shown to have very similar crystal structures.

Benzylmercaptan (benzylthiol) and its oxidised product dibenzyldisulphide have been isolated and characterised from the marine sponge Crella spinulata (Hentschel) found in the Great Barrier Reef, northern Australia. The structures of the two compounds were determined on the basis of their spectral and chemical properties. These two compounds were found only in gravid females collected during the reproductive season. The biochemical interest of these sulphur-containing compounds in the gravid females is briefly discussed in relation to the role of sulphydryl groups in biological systems.

Syntheses and properties of isomeric(diethylenetriamine)platinum(II) complexes of 1,1-dimethylurea (DMU)bound through oxygen or nitrogen are reported. Isomers were distinguished by a combination of NMR (H-1, C-13) and IR spectroscopy, acidity and reactivity measurements, and an isomer selective synthetic route. The oxygen-bonded DMU compound, [dienPtOC(NH2)NMe2]2+, is the kinetically preferred product from the stoichiometric reaction of DMU with [dienPtOH2]2+ in acetone. This oxygen-bonded form then rearranges (t1/2 approximately 18 min, 22-degrees-C) to the slightly more thermodynamically stable nitrogen-bonded linkage isomer (K(NO) = [N-isomer]/[0-isomer] approximately 3). The reverse isomerization from N-bonding to O-bonding was also detected. NMR(H-1, C-13) and IR spectroscopy proved that the N-bonded DMU complex, which was also independently and selectively synthesized through base hydrolysis of the cyanamide precursor [dienPtN = CNMe2]2+, exists in solution and in the solid state as the unusual amide tautomer [dienPtNH2COR]2+ (R = NMe2), rather than the imidol tautomer [dienPtNH:C(OH)R]2+ observed for acetamide (R = Me). The N-bonded DMU ligand was much more acidic (pK(a) 5.6, H20,20-degrees-C) than the 0-bonded DMU linkage isomer (pK(a) greater-than-or-equal-to 11 (est)), indicating greater resonance stabilization for the deprotonated urea of [dienPtNHCONMe2]+ versus [dienPtOC(NMe2)NH]+, but less acidic than the N-bonded acetamide of [dienPtNH: C(OH)Me]2+ (pK(a) 3.8), where the acidic proton is on oxygen instead of nitrogen. Both the approximately 50-fold faster solvolysis of the N-bonded DMU versus the N-bonded acetamide (R = NMe2, k = 5 x 10(-4) S-1; R = Me, k = 1 X 10(-5) S-1; H2O, pH 2.5, 40.0-degrees-C) and the approximately 100-fold rate difference in linkage isomerization from O-bonding to N-bonding DMU (R = NMe2, k = 6.4 x 10(-4) s-1; R = Me, k = 6.8 x 10(-6) s-1; acetone, 22-degrees-C) are attributed to the requirement for proton migration between imidol and amide tautomers of the N-bonded form. Both isomerization and solvolysis likely proceed via the amide tautomer only. The O-bonded DMU ligand is displaced much faster (water, DMSO; t1/2 < 1 min, 22-degrees-C) than the N-bonded DMU ligand from platinum by coordinating solvents.

A concise synthesis of the yellow pigment benzylthiocrellidone 1, based on a Michael addition–elimination of dimedone 2 to the ketene thioacetal 7 derived from dimedone, benzyl bromide and carbon disulfide, is described. The synthetic pigment had an X-ray crystal structure identical to that measured for the natural product.

This study was undertaken to evaluate the protective efficacy of the antioxidants vitamin E and Trolox (a water-soluble vitamin E derivative) against the toxicity of microcystin-LR (MC-LR), Microcystis aeruginosa aqueous extract (CE), and a reference toxin, menadione sodium bisulfite (MSB), in Artemia franciscana nauplii. This was achieved by using the well-established brine shrimp bioassay. The experiment was conducted in 2 stages, with (1) 12-h mortality time course and (2) LC50 determination for 12- and 24-h exposures. Treatments consisted of MC-LR, CE, and MSB alone and with 4-h pretreatments of either vitamin E or Trolox. Sensitivity of A. franciscana nauplii with 24-h LC50 values of 11 (10.1-12.1) microg/ml for MSB and 9.5 (8.8-10.4) microg/ml for MC-LR were in general agreement with values reported for Artemia sp. Both antioxidant pretreatments resulted in significant reductions in mortality of approximately 50% at 9 h postexposure when challenged by either 40 microg/ml MC-LR or 20 microg/ml MSB. In contrast, the antioxidant pretreatments offered little to no protection from CE, suggesting that other uncharacterized bioactive compounds contributed to overall toxicity. The described bioassay is easily accessible, inexpensive, rapid, and complies with animal ethics guidelines of many countries, and thus provides a potential alternative to the mouse bioassay for the initial screening for chemoprotectants against MC-LR toxicity.

A referee analysis method for the detection and quantification of Pacific ciguatoxins in fish flesh has recently been established by the public health analytical laboratory for the State of Queensland, Australia. Fifty-six fish samples were analysed, which included 10 fillets purchased as negative controls. P-CTX-1 was identified in 27 samples, and P-CTX-2 and P-CTX-3 were found in 26 of those samples. The range of P-CTX-1 concentrations was 0.04-11.4 microg/kg fish flesh; coefficient of variation from 90 replicate analyses was 7.4%. A liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method utilising a rapid methanol extraction and clean-up is reliable and reproducible, with the detection limit at 0.03 microg/kg fish flesh. Some matrix effects are evident, with fish oil content a likely signal suppression factor. Species identification of samples by DNA sequence analysis revealed some evidence of fish substitution or inadvertent misidentification, which may have implications for the management and prevention of ciguatera poisoning. Blinded inspection of case notes from suspect ciguatera poisoning cases showed that reporting of ciguatera-related paraesthesias was highly predictable for the presence of ciguatoxins in analysed fish, with 13 of 14 expected cases having consumed fish that contained P-CTX-1 (p

The 1,3-diene 2,3-dimethylene-5,6,7,8-dibenzobicyclo[2.2.2] octane (ddbo, C18H14, 6) forms complexes Ir(eta-C5H5)(C18H14) (7), M(eta-C5Me5)(C18H14) [M = Rh (8), Ir (9)], and M(eta-1,3,5-C6H3Me3)(C18H14) [M = Ru (10), Os (11)], which react with aqueous HPF6 or triflic acid to give fluxional monoprotonated cations [Ir(eta-C5H5)(C18H15)]+ (14), [Rh(eta-C5Me5)(C18H15)]+ (12), [Ru(eta-C6H3Me3)(C18H15)]+ (13), and [Os(eta-C6H3Me3)(C18H15)]+ (15). Crystals of 13.PF6 are orthorhombic, space group P2(1)2(1)2(1), with a = 14.243 (2) angstrom, b = 13.554 (2) angstrom, c = 12.894 (2) angstrom, and Z = 4. The structure was solved by heavy-atom methods and refined by least-squares analysis to R = 0.034 and R(w) = 0.043 for 2020 unique observed reflections. The C18H15 moiety is bound to a (eta-6-mesitylene)ruthenium unit through a eta-3-enyl linkage [Ru-C(1) = 2.180 (8) angstrom, Ru-C(2) = 2.196 (7) angstrom, Ru-C(17) = 2.148 (7) angstrom] and a two-electron, three-center interaction Ru-H(18C)-C(18) to the terminal methyl group of the butenyl moiety [Ru-C(18) = 2.357 (9) angstrom, C(18)-H(18C) = 0.98 (8) angstrom, Ru-H(18C) = 1.81 (8) angstrom, angle C(17)-C(18)-H(18C) = 108 (5)-degrees, angle C(18)-H(18C)-Ru = 112 (6)-degrees]. The NMR (H-1, C-13) spectra of the rhodium complex 12 at-60-degrees-C are consistent with a similar ground-state agostic eta-3-methallyl structure, but unexpectedly, the H-1 NMR spectrum of 13 at -100-degrees-C resembles that expected for a hydrido (1,3-diene) structure. It is suggested that in 13 reversible C-H bond cleavage occurs more easily than M-H bond cleavage, whereas 12 shows the more usual reverse behavior. The NMR and IR spectra of 14 show this complex to have a hydrido 1,3-diene structure; the same is probably true for 15, although a eta-3-methallyl structure with a strong agostic interaction cannot be excluded. Treatment of 13 and 15 with tert-butyl isocyanide causes irreversible hydride transfer to ddbo, giving [M(eta-C6H3Me3)(C18H15)(CN-t-Bu)]PF6 [M = Ru (17), Os (16)].

Chlorination was investigated as a treatment option for degrading and thus removing saxitoxins (paralytic shellfish poisons, PSPs) produced by cyanobacteria (blue-green algae) from water. It was found to be effective with the order of ease of degradation of the saxitoxins being GTX5 (B1) approximately dcSTX > STX > GTX3 approximately C2 > C1 > GTX2. However the effectiveness of chlorine was pH dependent. Degradation as a function of pH was not linear with the degree of degradation increasing rapidly at around pH 7.5. At pH 9 > 90% removal was possible provided a residual of 0.5 mg l(-1) free chlorine was present after 30 min contact time. The more effective degradation at higher pH was unexpected as chlorine is known to be a weaker oxidant under these conditions. The more effective degradation, then, must be due to the toxins, which are ionisable molecules, being present in a form at higher pH which is more susceptible to oxidation. The feasibility of using chlorine to remove saxitoxins during water treatment will therefore depend strongly on the pH of the water being chlorinated. Degradation may be improved by pH adjustment but may not be a practical solution. Although saxitoxins were degraded in that the parent compounds were not detected by chemical analysis, there is no indication as to the nature of the degradation products. However, acute toxicity as determined by the mouse bioassay was eliminated.

Cylindrospermopsin (CYN), a potent cyanobacterial hepatotoxin produced by Cylindrospermopsis raciborskii and other cyanobacteria, is regularly found in water supplies in many parts of the world, and has been associated with the intoxication of humans and livestock. In this study, Balb/c mice were injected via the intraperitoneal (IP) route with a single dose of 0.2 mg/kg CYN. Animals were sacrificed at 6, 12, 24, 48 and 72 h. DNA was isolated from the mouse livers, and examined for strand breakage by alkaline gel electrophoresis (pH 12). Significant DNA strand breakage was observed in the mouse liver exposed to CYN, suggesting that induction of DNA strand breakage is probably one of the key mechanisms for CYN genotoxicity.

Higher plants, algae and some yeasts respond to potentially toxic heavy metals such as cadmium by synthesizing phytochelatins and related cysteine-rich polypeptides. We have used X-ray absorption spectroscopy to study the nature of cadmium binding in such peptides isolated from maize (Zea mays) exposed to low levels of cadmium, and in two synthetic cadmium-peptide complexes, Cd-(gamma-Glu-Cys)(3)Gly and Cd-(a-Glu-Cys)3Gly. We have used the synthetic ions [Cd(SPh)(4)](2-), [Cd-4(SPh)(10)](2-) and [S4Cd10(SPh)(16)](4-) as crystallographically defined models for the cadmium site. The Cd K-edge extended X-ray absorption fine structure (EXAFS) data, together with the Cd K, L-I, L-II and L-III near-edge spectra, reveal a predominantly tetrahedral coordination of cadmium by sulfur in both the phytochelatin and synthetic peptide complexes. In particular, the Cd Lm-edge lacks a peak at 3534.9 eV which was found to be prominent for oxygen- or nitrogen-coordinated species. The Cd-S distance in the phytochelatin complex is 2.54 Angstrom. The Cd K-edge EXAFS does not show any isolated, well-defined Cd-Cd interactions; however, contrary to the conclusion of previous work, their absence is not necessarily indicative of isolated cadmium-thiolate ligation. Evidence from other studies suggests that high static disorder, combined with a large vibrational component, serve to effectively wash out this contribution to the EXAFS. The sulfur K-edge, moreover, shows a low-energy feature both in the phytochelatin and in the synthetic cadmium-peptide complexes which is consistent with sulfide bound in a cluster with cadmium as found for [S4Cd10(SPh)(16)](4-) This feature strongly suggests the presence of a polynuclear cadmium cluster in maize phytochelatin. (C) 1999 Published by Elsevier Science B.V, All rights reserved.

Background: In October 2004, Manam Island volcano in Papua New Guinea erupted, causing over 10 000 villagers to flee to internally displaced person (IDP) camps, including 550 from Dugulaba village. Following violence over land access in March 2010, the IDPs fled the camps, and four months later concurrent outbreaks of acute watery diarrhea and unusual neurological complaints were reported in this population. Materials and Methods: A retrospective case-control study was conducted to identify the risk factors for peripheral neuropathy. Rectal swabs were collected from cases of acute watery diarrhea. Hair and serum metals and metalloids were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Results: There were 17 deaths among the 550 village inhabitants during the outbreak period at a crude mortality rate 21-fold that of a humanitarian crisis. Vibrio cholerae O1 El Tor Ogawa was confirmed among the population. Access tocommunity-level rehydration was crucial to mortality. Peripheral neuropathy was diagnosed among cases with neurological symptoms. A balanced diet was significantly protective against neuropathy. A dose-response relationship was seen between peripheral neuropathy and a decreasing number of micronutrient- rich foods in the diet. Deficiencies in copper, iron, selenium and zinc were identified among the cases of peripheral neuropathy. Conclusions: Cholera likely caused the mostly preventable excess mortality. Peripheral neuropathy was not caused by cholera, but cholera may worsen existing nutritional deficiencies. The peripheral neuropathy was likely caused by complex micronutrient deficiencies linked to non-diversified diets that potentially increased the vulnerability of this population, however a new zinc-associated neuropathy could not be ruled out. Reoccurrence can be prevented by addressing the root cause of displacement and ensuring access to arable land and timely resettlement.

A concise synthesis of the yellow pigment benzylthiocrellidone 1, based on a Michael addition–elimination of dimedone 2 to the ketene thioacetal 7 derived from dimedone, benzyl bromide and carbon disulfide, is described. The synthetic pigment had an X-ray crystal structure identical to that measured for the natural product.

The title compound is prepared by the consecutive reaction of MoOCl4, with THF and then the bismacrocyclic compound 1,4-bis(1-oxa-4,10-dithia-7-azacyclododecan-7-ylmethyl) benzene. The crystals are triclinic, space group [Formula: see text]a = 11.993(7), b = 13.196(8), c = 7.928(5) Å, α = 104.54(4), β = 94.89(3), γ = 81.59(1)°, V = 1199.9 Å3,Z = 1. The final R factor was 0.059 for 2846 reflections where I > 3σ(I). The compound is ionic with the macrocycles protonated on both the nitrogen atoms while the anions are octahedral [MoOCl4(THF)]− units. These units have the oxo group (Mo=O, 1.655(7) Å) trans to THF (Mo—O, 2.331(5) Å). The cations adopt a centrosymmetric trans conformation with no strong interactions with the molybdenum.

Carbon monoxide reacts at atmospheric pressure and temperature with trans-Pt(OH)(C6H5)(PEt3)2 (1) to give a metallacarboxylic acid, trans-Pt(CO2H)(C6H5)(PEt3) 2 (2). Crystals of 2 are monoclinic, space group C2/c, a = 15.006 (2) A, b = 11.520 (2) A, c = 27.135 (6) A, b = 89.90 (1)d, Z = 8, at 175 K. The structure was solved by heavy atom methods and refined by least-squares techniques to R = 0.033 (Rw = 0.038) for 3070 unique data (I g 3s(I)). It consists of a dimer in which two planar trans-Pt(CO2H)(C6H5)(PEt3) 2 units are joined by hydrogen bonding between the carboxylate groups. This structure, the O-H⋯O distance of 2.695 A, and the metrical data for the carboxylate group [r(C=O) = 1.238 (11) A, r(C-O) = 1.334 (10) A, and O-Ĉ-O = 117.7 (8) A] are similar to those found for many organic carboxylic acids. Solutions of 2 in organic solvents contain monomer and dimer in equilibrium; in formamide and N-methylformamide, dissociation to [Pt(C6H5)(CO)(PEt3)2]OH takes place. This dissociation accounts for many of the reactions of 2, e.g., facile exchange in the CO2H group with CO and reaction with HBF4, HCl, CH3OH, and (CH3)2NH to give, respectively, [Pt(C6H5)(CO)(PEt3)2]BF4, [Pt(C6H5)(CO)(PEt3)2]Cl, Pt(CO2Me)(C6H5)(PEt3)2, (3), and Pt(CONMe2)(C6H5)(PEt3)2 (4) (trans isomers in all cases). Although 2 does not form salts with KOH, KHCO3, or tertiary amines, it does react reversibly with its precursor 1 in a kind of acid-base or esterification reaction to give a dinuclear platinum(II) complex containing a m2-CO2 ligand, [trans-Pt(C6H5)(PEt3)2]2 (m2-CO2) (5), which has been identified by its NMR (13C, 31P, and 195Pt) and IR spectra. Complex 5 is also formed, together with ca. 0.5 mol of CO, when 2 is heated at ca. 100dC. This mode of decomposition contrasts with that normally observed for metallacarboxylic acids, viz. formation of a metal hydride and loss of CO2.

Attempts to prepare the complexes cis-L2Pt(SH)2, where L = PPh3, PMePh2, and PMePh by treatment of the appropriate dichloro complexes with NaSH in the presence of CH2Cl2 have resulted in the isolation of the complexes L2Pt(S2CH2). The X-ray structure determination of the compound for which L = PMe2Ph confirms the presence of the CH2S22−ligand.

[PtC12{P2(C3H6)(C6Hs)4}], Mr=678.4 , triclinic, Pi, a= 14.424 (1), b= 10.686 (1), c=8.580 (1)A, e= 72.61 (1), t= 79.80 (1), y=88.31 (1) °, U-- 1241.6,~ 3, Z=2, Din- 1.80(1), D x= 1.81 gcm -3, MoK~, 2 = 0.71069/~, g = 63.0 cm -1, F(000) = 660, T = 294 (1) K, R = 0.025, wR = 0.029 for 6195 unique reflections [I>3o(I)]. Crystals are isomorphous with those of their palladium analogue and molecular dimensions differ only in detail. The Pt--P bond distances are equivalent to within experimental error [av. 2.2321 (6)A] but the Pt-C1 distances are inequivalent [2.3559 (8) and 2.3687 (8)A]. The alkyl backbone of the phospineligand exhibits substantial angular strain.

A single-crystal X-ray structural study of the ClO4– salt of the title cation demonstrates this species contains neither a monodentate nor a covalently hydrated bipyridine ligand; all three bipyridine ligands are chelated to iridium(III) but one bipyridine ligand is ligated via the nitrogen of one ring and the C(3) carbon of the other ring, reminiscent of orthometallated compounds.

Carbon monoxide reacts at atmospheric pressure and temperature with trans-Pt(OH)(C6H5)(PEt3)2 (1) to give a metallacarboxylic acid, trans-Pt(CO2H)(C6H5)(PEt3) 2 (2). Crystals of 2 are monoclinic, space group C2/c, a = 15.006 (2) A, b = 11.520 (2) A, c = 27.135 (6) A, b = 89.90 (1)d, Z = 8, at 175 K. The structure was solved by heavy atom methods and refined by least-squares techniques to R = 0.033 (Rw = 0.038) for 3070 unique data (I g 3s(I)). It consists of a dimer in which two planar trans-Pt(CO2H)(C6H5)(PEt3) 2 units are joined by hydrogen bonding between the carboxylate groups. This structure, the O-H⋯O distance of 2.695 A, and the metrical data for the carboxylate group [r(C=O) = 1.238 (11) A, r(C-O) = 1.334 (10) A, and O-Ĉ-O = 117.7 (8) A] are similar to those found for many organic carboxylic acids. Solutions of 2 in organic solvents contain monomer and dimer in equilibrium; in formamide and N-methylformamide, dissociation to [Pt(C6H5)(CO)(PEt3)2]OH takes place. This dissociation accounts for many of the reactions of 2, e.g., facile exchange in the CO2H group with CO and reaction with HBF4, HCl, CH3OH, and (CH3)2NH to give, respectively, [Pt(C6H5)(CO)(PEt3)2]BF4, [Pt(C6H5)(CO)(PEt3)2]Cl, Pt(CO2Me)(C6H5)(PEt3)2, (3), and Pt(CONMe2)(C6H5)(PEt3)2 (4) (trans isomers in all cases). Although 2 does not form salts with KOH, KHCO3, or tertiary amines, it does react reversibly with its precursor 1 in a kind of acid-base or esterification reaction to give a dinuclear platinum(II) complex containing a m2-CO2 ligand, [trans-Pt(C6H5)(PEt3)2]2 (m2-CO2) (5), which has been identified by its NMR (13C, 31P, and 195Pt) and IR spectra. Complex 5 is also formed, together with ca. 0.5 mol of CO, when 2 is heated at ca. 100dC. This mode of decomposition contrasts with that normally observed for metallacarboxylic acids, viz. formation of a metal hydride and loss of CO2.

Cyanobacteria can produce groups of structurally and functionally unrelated but highly potent toxins. Cyanotoxins are used in multiple research endeavours, either for direct investigation of their toxicologic properties, or as functional analogues for various biochemical and physiological processes. This paper presents occupational safety guidelines and recommendations for personnel working in field, laboratory or industrial settings to produce and use purified cyanotoxins and toxic cyanobacteria, from bulk harvesting of bloom material, mass culture of laboratory isolates, through routine extraction, isolation and purification. Oral, inhalational, dermal and parenteral routes are all potential occupational exposure pathways during the various stages of cyanotoxin production and application. Investigation of toxicologic or pharmacologic properties using in vivo models may present specific risks if radiolabelled cyanotoxins are employed, and the potential for occupational exposure via the dermal route is heightened with the use of organic solvents as vehicles. Inter- and intra-national transport of living cyanobacteria for research purposes risks establishing feral microalgal populations, so disinfection of culture equipment and destruction of cells by autoclaving, incineration and/or chlorination is recommended in order to prevent viable cyanobacteria from escaping research or production facilities.

We surveyed the occurrence of toxigenic cyanobacteria, the mcyA component of the microcystin synthetase gene and microcystin in aquatic systems in temperate Australia and tropical Thailand. The survey methods, microscopy, protein phosphatase inhibition assay, enzyme linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), were evaluated for screening raw water for public health risk from microcystin producing toxigenic cyanobacteria. Three tests, ELISA, PCR and protein phosphatase inhibition (PPi), were judged very useful because of their sensitivity and speed of analysis. ELISA ranked slightly higher because of its superior specificity for microcystin. The PCR was highly sensitive, but there were three false negative results, whilst the PPi was cheap but less specific than ELISA. Some of the microcystin quantifications results were validated by high performance liquid chromatography (HPLC). The combination of a gene probe for the mcy gene complex with an ELISA or PPi assay for microcystin is proposed as a powerful screening technique for raw waters that can provide multi-level risk assessment including ‘incipient risk’, when microcystin producing cyanobacterial strains are rare and microcystin concentrations are below the detection limit for biochemical or chromatographic analyses.