bluuebunny/crossref_metadata_2025 huggingface dataset:
The Synthesis of trans‐Perhydroindolic Acids and their Application in Asymmetric Domino Reactions of Aldehyde Esters with β,γ‐Unsaturated α‐Keto Esters
Authors: Shen Jiefeng , Liu Delong , An Qianjin , Liu Yangang , Zhang Wanbin
Published: November 2012

(2S,3aR,7aS)‐Perhydroindolic acid, the key intermediate in the synthesis of trandolapril, and its trans‐isomers, were readily prepared. These proline‐like molecules are unique in that they contain a rigid bicyclic structure, with two hydrogen atoms trans to each other at the bridgehead carbon atoms. These molecules were used successfully as chiral organocatalysts in asymmetric domino Michael addition/cyclization reactions of aldehyde esters with β,γ‐unsaturated α‐keto esters. They proved to have excellent catalytic behavior, allowing for the synthesis of multi‐substituted, enantiomerically enriched hemiacetal esters. Under optimal conditions (using 10 mol% catalyst loading), a series of β,γ‐unsaturated α‐keto esters was examined with up to 99% de, ee and yield, respectively. Additionally, the enantiomerically enriched hemiacetal esters could be readily transformed into their corresponding bioactive pyrano[2,3‐b]pyrans (possessing a multi‐substituted bicyclic backbone).
Efficient Room‐Temperature Oxidation of Hydrocarbons Mediated by Tricopper Cluster Complexes with Different Ligands
Authors: Nagababu Penumaka , Maji Suman , Kumar Manyam Praveen , Chen Peter P.‐Y. , Yu Steve S.‐F. , Chan Sunney I.
Published: November 2012

Six tricopper cluster complexes of the type [CuICuICuI(L)]1+ supported by a series of multidentate ligands (L) have been developed as oxidation catalysts. These complexes are capable of mediating the facile oxygen‐atom transfer to hydrocarbon substrates like cyclohexane, benzene, and styrene (C6H12, C6H6 and C8H8) upon activation by hydrogen peroxide at room temperature. The processes are catalytic with high turnover frequencies (TOF), efficiently oxidizing the substrates to their corresponding alcohols, aldehydes, and ketones in moderate to high yields. The catalysts are robust with turnover numbers (TON) limited only by the availability of hydrogen peroxide used to drive the catalytic turnover. The TON is independent of the substrate concentration and the TOF depends linearly on the hydrogen peroxide concentration when the oxidation of the substrate mediated by the activated tricopper complex is rapid. At low substrate concentrations, the catalytic system exhibits abortive cycling resulting from competing reduction of the activated catalyst by hydrogen peroxide. This behaviour of the system is consistent with activation of the tricopper complex by hydrogen peroxide to generate a strong oxidizing intermediate capable of a facile direct “oxygen‐atom” transfer to the substrate upon formation of a transient complex between the activated catalyst and the substrate. Some substrate specificity has also been noted by varying the ligand design. These properties of the tricopper catalyst are characteristic of many enzyme systems, such as cytochrome P450, which participate in biological oxidations.
Catalytic Electrophilic Halogenation of Silyl‐Protected and Terminal Alkynes: Trapping Gold(I) Acetylides vs. a Brønsted Acid‐Promoted Reaction
Authors: Starkov Pavel , Rota Filippo , D'Oyley Jarryl M. , Sheppard Tom D.
Published: November 2012

In the presence of a cationic gold(I) catalyst and N‐halosuccinimide, both trimethylsilyl‐protected and terminal alkynes are converted into alkynyl halides. Further experiments showed that silyl‐protected alkynes undergo electrophilic iodination and bromination under Brønsted acid catalysis, whilst terminal alkynes require a cationic gold catalyst. The former reactions probably proceed via activation of the electrophile, whilst the latter reactions proceed via a gold(I) acetylide intermediate. Gold‐catalysed halogenation was further combined with gold‐catalysed hydration and subsequent annulation to provide convenient routes to iodomethyl ketones and five‐membered aromatic heterocycles.
Construction of Contiguous Tetrasubstituted Carbon Stereocenters by Intramolecular Crossed Benzoin Reactions Catalyzed by N‐Heterocyclic Carbene (NHC) Organocatalyst
Authors: Ema Tadashi , Akihara Kumiko , Obayashi Ryoko , Sakai Takashi
Published: November 2012

Bicyclic compounds with two contiguous tetrasubstituted carbon stereocenters at bridgehead positions were synthesized by N‐heterocyclic carbene (NHC)‐catalyzed intramolecular crossed benzoin reactions of symmetrical compounds. This desymmetrization strategy was applied to asymmetric synthesis with chiral NHC organocatalysts. Transition‐state models were proposed to explain the enantioselectivity. A tricyclic compound with three contiguous tetrasubstituted carbon stereocenters was synthesized by a stepwise strategy. The molecular structure and absolute configuration of the (+)‐enantiomer of this tricyclic compound were determined by X‐ray crystallographic analysis.
Palladium‐Catalyzed CH Bond Acetoxylation: An Approach to ortho‐Substituted Hydroxy[2.2]paracyclophane Derivatives
Authors: Lennartz Petra , Raabe Gerhard , Bolm Carsten
Published: November 2012

The palladium‐catalyzed direct CH bond acetoxylation of [2.2]paracyclophanes has been investigated. Various mono‐ and disubstituted [2.2]paracyclophanes were subjected to typical Sanford acetoxylation conditions. Oxime ethers, an oxime acetate, a pyridine, and a pyrazole with [2.2]paracyclophane cores underwent direct ortho‐acetoxylation in good to excellent yields using 1–5 mol% of palladium(II) acetate in combination with iodobenzene diacetate as oxidant. The reactions could be performed on a multigram scale, and the ortho‐acetoxylated [2.2]paracyclophanes were suitable for further functionalizations affording a hydroxy[2.2]paracyclophane derivative and a planar chiral benzoxazole.
Step‐Economic and Protecting‐Group‐Free Total Synthesis of (+)‐Cardiobutanolide
Authors: Fernandes Rodney A. , Kattanguru Pullaiah
Published: November 2012

A short protecting‐group‐free synthesis of (+)‐cardiobutanolide is reported. We have modified a one‐pot conversion of D‐glucono‐δ‐lactone into the building block β‐hydroxy‐γ‐lactone. A series of cross‐metathesis reactions and dihydroxylations either under the Sharpless conditions or achiral 4‐methylmorpholine N‐oxide (NMO) conditions were used to synthesize (+)‐cardiobutanolide and its various diastereomers. In this endeavour, we have achieved a step‐economic and protecting‐group‐free synthesis of (+)‐cardiobutanolide in 22.4 % overall yield from D‐glucono‐δ‐lactone. A cross‐metathesis reaction that is compatible with hydroxy groups and a substrate controlled Upjohn dihydroxylation reaction are key steps in the synthesis. The synthesis is highly efficient and competitive with previous reports.
Cyclodextrin functionalization of several cellulosic substrates for prolonged release of antibacterial agents
Authors: Cusola Oriol , Tabary Nicolas , Belgacem Mohamed Naceur , Bras Julien
Published: November 2012

Several cellulosic substrates have been surface‐functionalized with cyclomaltoheptaose (β‐cyclodextrin, β‐CD) using citric acid as a crosslinker agent to obtain new surface‐modified materials able to release antiseptic molecules over a prolonged period, in view of their use in medical domain. Three different commercial cellulosic substrates were used, namely: (i) an uncoated paper, (ii) a crepe paper, and (iii) a medical bandage. They were successfully grafted by a crosslinked polymer consisting on β‐CD molecules as assessed by scanning electron microscopy and Fourier transform infrared spectroscopy analysis. Several time–temperature kinetic cycles were performed to reach the optimum curing parameters. The grafted and nongrafted samples were loaded with chlorhexidine digluconate (digCHX), a widely used antiseptic agent. The drug‐delivery kinetics of the encapsulated digCHX was carried out by immersing the sample under investigation into an aqueous medium, and the quantity of the released digCHX was measured, as a function of time, by UV spectroscopy. The optimal grafting conditions were established on the basis of the highest weight gain. These samples did not give the best release performance. Nevertheless, several grafted substrates were able to uptake an appreciable amount of active molecules and release them over a prolonged time of about 20 days. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
On the brink – investigating biodiversity in endangered crater lakes of the Amber Mountains National Park (Madagascar)
Authors: Schabetsberger R. , Kaiser R. , Rott E. , Lenzenweger R. , Traunspurger W. , Kotov A. A. , Fiers F. , Gaviria S. , Meisch C. , Mahunka S. , Campbell R. D. , Razafindranaivo E. , Sztatecsny M.
Published: November 2012

Madagascar's biodiversity is vanishing at an alarming pace. The documentation of this loss has so far focused on terrestrial habitats and organisms. Eight volcanic crater lakes in the Amber Mountains National Park (Northern Madagascar) and surroundings were investigated for the first time to describe limnological conditions and aquatic biodiversity. Seven of the lakes were affected by deforestation/logging and fish introduction and only one lake was assumed to have remained in pristine condition. In the deeper lakes (> 5 m) steep physico‐chemical gradients and anoxic hypolimnia were observed.

Algae, hydrozoans, nematodes, rotifers, annelids, copepods, cladocerans, ostracods, and mites were identified to genus or species level. The majority were taxa with a cosmopolitan or tropicopolitan distribution. The highest number of afrotropical and endemic species were recorded within the crustaceans.

Multivariate analysis of species communities revealed significant differences between lakes in deforested and forested catchments. Introduced alien fish had no detectable effect on species assemblages.

Illegal harvest of timber was observed within the National Park and drug plantations are less than 1 km away from the last pristine crater lake. If deforestation continues at the current rate, which is likely under the prevailing political situation, the last undisturbed lake communities may be altered in the near future.

There is an urgent need for taxonomic research to assess the biodiversity of algae and micrometazoa. Highest priority should be given to pristine freshwater ecosystems within protected areas.

Copyright © 2012 John Wiley & Sons, Ltd.
Learning and Affect Following Near‐Miss Outcomes in Simulated Gambling
Authors: Clark Luke , Liu Rui , McKavanagh Rebecca , Garrett Alice , Dunn Barnaby D. , Aitken Michael R. F.
Published: November 2012

Gambling near‐misses are non‐rewarded events that resemble a winning configuration. Past research using slot machines has shown that moderate rates of near‐misses increase gambling persistence, but the mechanisms supporting this persistence are unclear. One hypothesis is that near‐misses are mistakenly interpreted as signals of skill acquisition, supporting learning and fuelling the ‘illusion of control’. A slot machine simulation was administered to 60 volunteers, with ratings of the perceived chances of winning, pleasure and motivation to play following particular outcomes. Psychophysiological measures (electrodermal activity and heart rate) were taken, and gambling persistence was measured after 30 trials. Near‐misses were similar to full‐miss outcomes in that they were regarded as unpleasant. However, near‐misses were akin to win outcomes in that they increased motivations to play and electrodermal activity. Learning was evidenced by the expectancy of winning increasing following wins and decreasing after losses. Although there was no overall change in expectancy of winning after near‐misses across all participants, those subjects reporting a greater increase in the expectancy of winning following a near‐miss showed more persistent play, consistent with the learning hypothesis. Greater heart rate acceleration following near‐misses was also associated with persistence. We also observed differential effects of near‐misses where the reel stopped either side of the winning position (‘payline’): motivational effects were restricted to near‐misses stopping before the payline, whereas near‐misses that stopped after the payline were primarily aversive. The payline effects are not predicted by the learning hypothesis and may indicate an affective component to near‐misses, possibly linked to counterfactual processing. Copyright © 2012 John Wiley & Sons, Ltd.
Multicentre study of circumferential margin positivity and outcomes following abdominoperineal excision for rectal cancer
Authors: Kennelly R P , Rogers A C , Winter D C
Published: November 2012

Background

Rectal cancer outcomes following abdominoperineal excision (APE) have been inferior to those for anterior resection, including more positive circumferential resection margins (CRMs). An erroneously conservative interpretation of APE (rather than a radical resection termed ‘extralevator’) has been proposed as the cause. In this multicentre study, factors contributing to CRM positivity were examined following APE according to its original description.

Methods

Data were collected from five hospital databases up to June 2011 including small- and larger-volume units (3 hospitals had 5 or fewer and 2 hospitals had more than 5 APE procedures per year). Primary outcome measures were CRM status; secondary outcomes were local recurrence and death.

Results

Of 327 patients, 302 patients had complete data for analysis. Some 50·0 per cent of patients had neoadjuvant chemoradiotherapy. Histopathological examination showed that 62·9 per cent had tumour category T3 or T4 cancers, 42·1 per cent had node-positive disease and the CRM positivity rate was 13·9 per cent. Multivariable analysis showed only pathological tumour category pT4 (odds ratio 19·92, 95 per cent confidence interval 6·48 to 68·61) and node positivity (odds ratio 3·04, 1·32 to 8·05) to be risk factors for a positive circumferential margin. CRM positivity was a risk factor for local recurrence (P = 0·022) and decreased overall survival (P = 0·001). Hospital volume had no impact on the likelihood of CRM positivity (P = 0·435).

Conclusion

In patients undergoing APE by appropriately trained surgeons using a standardized approach, margin positivity was dictated by tumour stage, but not by centre or surgeon.
A Systematic Review of the Differential Diagnosis of Retinal Haemorrhages in Children with Clinical Features associated with Child Abuse
Authors: Maguire Sabine Ann , Lumb Rebecca Caroline , Kemp Alison Mary , Moynihan Sian , Bunting Howard John , Watts Patrick O. , Adams Gillian Gwendolen
Published: November 2012

Retinal haemorrhages (RH) in a young child suggest child abuse, yet other causes merit consideration. This systematic review addresses non‐traumatic causes of RH in children with one or more overlapping clinical features of abuse (bruising, fractures, intracranial haemorrhage). Searching 12 databases (1950–2009) identified 338 studies for review by two reviewers. Inclusion criteria included: children < 15 years examined by an ophthalmologist detailing retinal findings, confirmed organic cause and exclusion of abuse. Exclusion criteria included: diagnosed coagulopathy, ocular mass lesion and post‐mortem cases. Twenty included studies identified nine relevant conditions (metabolic diseases, bony dysplasias, bleeding disorders and vascular malformations). Where detailed, the RH were bilateral and involved only one area of the retina (the posterior pole). Among proposed confounders of RH, no child with a cough (100 children) or acute life‐threatening event (184 cases) had RH. Just two of 217 children with seizures had posterior pole RH, one unilateral and one bilateral. One cardiopulmonary resuscitation (CPR) study (43 cases) was included where a child with co‐existent clotting abnormalities had tiny (bilateral dot) RH after 60 minutes’ resuscitation. Child abuse remains the commonest cause of RH in young children, although rarer disorders merit consideration. There are insufficient data to conclude that CPR is a confounder in children with RH. Copyright © 2012 John Wiley & Sons, Ltd.

‘Searching 12 databases (1950–2009) identified 338 studies for review’

‘There are insufficient data to conclude that CPR is a confounder in children with RH’

Key Practitioner Message

Retinal Haemorrhages are strongly associated with Abusive Head Trauma, but have been described in certain medical conditions.

Neither cough nor ALTE are associated with RH, which have been found in < 3% of children with seizures. There are inadequate data to conclude that CPR is associated with RH.

Case series have reported RH in children who also have clinical features that may overlap with physical abuse, namely certain metabolic, vascular, haematologic disorders and bony dysplasias (specifically osteogenesis imperfecta).
A Comparison Study between Official Records and Self‐Reports of Childhood Adversity
Authors: Pinto Ricardo J. , Maia Ângela C.
Published: November 2012

The aim of this paper was to assess the degree and nature of any mismatch between officially recognised child maltreatment and adolescent self‐report of adverse child experiences. Participants included 136 adolescents (72 males, 64 females, Mage = 17 years, age range 14–23 years) who had been confirmed as victims of maltreatment prior to age 13 by Child Protective Services. Participants' self‐reports were obtained in adolescence, at least four years after identification. Physical neglect was the most prevalent experience found in the records (87%, n = 118). When this experience was assessed through self‐report, only 36 per cent (n = 49) of participants reported physical neglect. Sexual abuse was self‐reported by 17 per cent (n = 23) of the sample, compared with eight per cent (n = 11) in the records. Only 17 per cent (n = 23), a small number of self‐reports, were consistent with official records. Kappa values show that agreement is low (under 0.40) for seven of the ten categories. Our findings suggest substantial unreliability in the reporting of child abuse and neglect, including household adverse experiences. They also suggest the failure of professionals to discover several adverse experiences during childhood, even after identification by authorities. Copyright © 2012 John Wiley & Sons, Ltd.

‘Only 17 per cent, a small number of self‐reports, were consistent with official records’

Key Practitioner Messages

Child protection practitioners need to be aware of multiple experiences that can co‐occur with the suspicion or situation initially reported to child protection agencies.

Little attention is given to protecting children and young people from later re‐victimisation.

The conclusions from the relationship between childhood maltreatment and later outcomes should be approached with caution when retrospective reports or official data are used alone.

‘Little attention is given to protecting children and young people from later re‐victimisation’
A Luminescent Cyclometalated Iridium(III) Complex Accumulates in Mitochondria and Induces Mitochondrial Shortening by Conjugation to Specific Protein Targets
Authors: Wang Baojiang , Liang Yimin , Dong Hongjuan , Tan Tianfeng , Zhan Bao , Cheng Jinping , Lo Kenneth Kam‐Wing , Lam Yun Wah , Cheng Shuk Han
Published: November 2012

We report the cellular properties of a luminescent cyclometalated iridium(III) complex, [Ir(pq)2(phen‐ITC)](PF6) (Ir‐ITC; Hpq=2‐phenylquinoline, phen‐ITC=5‐isothiocyanate‐1,10‐phenanthroline), that efficiently and specifically labels mitochondria in living mammalian cells. Ir‐ITC can be covalently conjugated to its protein targets, and its luminescence survived cell lysis, protein extraction, and gel electrophoresis under denaturing conditions. The conjugation of Ir‐ITC with live‐cell proteins is rapid and highly selective; the process requires active cellular metabolism, as the conjugation is abolished at nonphysiological temperature or in the presence of sodium azide. Based on measurements of the luminescence intensity, we have devised a biochemical fractionation procedure that allows the enrichment of the conjugated proteins, and their subsequent separation by two‐dimensional gel electrophoresis (2DGE). Luminescent protein spots were picked from the gel and analyzed by mass spectrometry; this resulted in the identification of 46 proteins. Many of the strongly luminescently labeled proteins are mitochondrial proteins. One of the targets is VDAC1 (voltage‐dependent anion channel 1). Consistent with known phenotypes of VDAC1 deregulation, prolonged exposure of cells to Ir‐ITC led to significant mitochondrial shortening and fragmentation. As far as we know, this is the first report on the molecular characterization of the interactions of a luminescent dye with its biological targets. As many biological dyes exhibit specific intracellular staining patterns, the identification of their molecular targets can help elucidate the mechanisms behind their staining specificities and cytotoxicity. We believe our biochemical approach can be applied to identify the targets of a wide range of fluorescent and luminescent probes.
New Insights into the Biosynthesis of Prenylated Xanthones: Xptb from Aspergillus nidulans Catalyses an O‐Prenylation of Xanthones
Authors: Pockrandt Daniel , Ludwig Lena , Fan Aili , König Gabriele M. , Li Shu‐Ming
Published: November 2012

Gene‐inactivation experiments have indicated that the putative prenyltransferase XptB from Aspergillus nidulans was likely to be responsible for the prenylation of 1,7‐dihydroxy‐6‐methyl‐8‐hydroxymethylxanthone. Recently, it was suggested that this enzyme might also accept as substrate the benzophenone arugosin H, which is assumed to be a precursor of prenylated xanthones. In this study, five benzophenones and ten xanthones were incubated with purified recombinant XptB in the presence of dimethylallyl diphosphate (DMAPP). XptB accepted four xanthones as substrates, including the proposed natural substrate, and catalysed regiospecific O‐prenylations at C‐7 of the xanthone core. Km values in the range of 0.081–1.1 mM and turnover numbers (kcat) between 0.02 and 0.5 s−1 were determined for the accepted xanthones. The kinetic parameters for DMAPP were found to be 0.024 mM (Km) and 0.13 s−1 (kcat). Arugosin H was not accepted by XptB under the tested conditions. XptB was relatively specific towards its prenyl donor and did not accept geranyl or farnesyl diphosphate as substrate. Mn2+ and Co2+ strongly enhanced XptB activity (up to eightfold); this has not been reported before for prenyltransferases of the DMATS superfamily.
De Novo Design, Synthesis and Characterisation of MP3, A New Catalytic Four‐Helix Bundle Hemeprotein
Authors: Faiella Marina , Maglio Ornella , Nastri Flavia , Lombardi Angela , Lista Liliana , Hagen Wilfred R. , Pavone Vincenzo
Published: November 2012

A new artificial metalloenzyme, MP3 (MiniPeroxidase 3), designed by combining the excellent structural properties of four‐helix bundle protein scaffolds with the activity of natural peroxidases, was synthesised and characterised. This new hemeprotein model was developed by covalently linking the deuteroporphyrin to two peptide chains of different compositions to obtain an asymmetric helix–loop–helix/heme/helix–loop–helix sandwich arrangement, characterised by 1) a His residue on one chain that acts as an axial ligand to the iron ion; 2) a vacant distal site that is able to accommodate exogenous ligands or substrates; and 3) an Arg residue in the distal site that should assist in hydrogen peroxide activation to give an HRP‐like catalytic process. MP3 was synthesised and characterised as its iron complex. CD measurements revealed the high helix‐forming propensity of the peptide, confirming the appropriateness of the model procedure; UV/Vis, MCD and EPR experiments gave insights into the coordination geometry and the spin state of the metal. Kinetic experiments showed that FeIII–MP3 possesses peroxidase‐like activity comparable to R38A–hHRP, highlighting the possibility of mimicking the functional features of natural enzymes. The synergistic application of de novo design methods, synthetic procedures, and spectroscopic characterisation, described herein, demonstrates a method by which to implement and optimise catalytic activity for an enzyme mimetic.
Tuning Chloride Binding, Encapsulation, and Transport by Peripheral Substitution of Pseudopeptidic Tripodal Small Cages
Authors: Martí Inés , Rubio Jenifer , Bolte Michael , Burguete M. Isabel , Vicent Cristian , Quesada Roberto , Alfonso Ignacio , Luis Santiago V.
Published: November 2012

A highly efficient synthesis of small pseudopeptidic cages from simple precursors has been achieved by the triple SN2 reaction between tripodal tris(amido amines) and several 1,3,5‐tris(bromomethyl)benzene electrophiles. The success of the macrobicyclization strongly depends on the central triamine scaffold, which dictates the correct preorganization of the intermediates. The chloride binding properties of the protonated pseudopeptidic cages have been studied in the solid state (by X‐ray diffraction) as well as in solution (by NMR spectroscopy and ESI‐MS) and in the gas phase (by collision‐induced dissociation (CID)‐MS). The crystal structure of the HCl salts of several cages show a chloride partially or completely caged within the cavity of the macrobicycle. Both the amino acid side chain and the substitution at the aromatic tripodal ring have an effect on the chloride binding ability. The cages derived from the 1,3,5‐benzene moiety show low affinity, whereas the triple substitution in the ring (either with Me or Et) increases the chloride binding by one order of magnitude. Besides, the cages derived from aliphatic amino acids display a stronger interaction than those derived from phenylalanine. The basis for the different mode of binding depending on the receptor structure is proposed according to the structural data (X‐ray and NMR spectroscopy). Finally, the transport of the chloride anion through lipid bilayers has been studied for selected cages. Despite the important differences in the chloride binding, the transport properties are better correlated with the lipophilicity of the molecules. Therefore, the pseudopeptidic cages sharing the same binding motif for chloride rendered very different interaction and transport properties depending on the peripheral substitution.
Change of Boron Substitution Improves the Lasing Performance of Bodipy Dyes: A Mechanistic Rationalisation
Authors: Jagtap Krishna K. , Shivran Neelam , Mula Soumyaditya , Naik Devidas B. , Sarkar Sisir K. , Mukherjee Tulsi , Maity Dilip K. , Ray Alok K.
Published: November 2012

Bodipy laser dyes are highly efficient but degrade rapidly in solution by reacting with in situ generated singlet oxygen (1O2). To increase the lasing lifetimes of these dyes, we have designed and synthesised two different congeners of the widely studied Pyrromethene 567 (PM567) by substitution at the boron centre and/or at both the boron centre and the meso position. The two new dyes showed high lasing efficiencies with increased photostability. The results of theoretical and pulse radiolysis studies revealed that the substitution at the boron centre reduced the 1O2 generation capacity of these dyes as well as their rate of reaction with 1O2, thereby enhancing their lifetimes even under lasing conditions.
Reactivity of a Frustrated Lewis Pair and Small‐Molecule Activation by an Isolable Arduengo CarbeneB{3,5‐(CF3)2C6H3}3 Complex
Authors: Kolychev Eugene L. , Bannenberg Thomas , Freytag Matthias , Daniliuc Constantin G. , Jones Peter G. , Tamm Matthias
Published: November 2012

Tris[3,5‐bis(trifluoromethyl)phenyl]borane reacts with the sterically demanding Arduengo carbenes 1,3‐di‐tert‐butylimidazolin‐2‐ylidene and 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene to form isolable normal adducts. In the case of 1,3‐di‐tert‐butylimidazolin‐2‐ylidene, the adduct exhibits dynamic behaviour in solution and frustrated‐Lewis‐pair (FLP) reactivity. Fast cleavage of dihydrogen and THF, the CH activation of phenylacetylene, and carbon dioxide fixation were achieved by using solutions of this adduct in benzene. This adduct is stable at room temperature in the absence of suitable substrates; however, thermal rearrangement into an abnormal carbene–borane adduct can be observed. In contrast, the 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene adduct exhibits no evidence of FLP reactivity or of dissociation in solution. DFT calculations confirmed the experimental behaviour and stability of these carbene–borane adducts.
Bioprocess Development in Single‐Use Systems for Heterotrophic Marine Microalgae
Authors: Hillig Friederike , Annemüller Steffi , Chmielewska Magdalena , Pilarek Maciej , Junne Stefan , Neubauer Peter
Published: November 2012

The utilization of single‐use systems is more and more common in upstream cultivation in biotechnological processes. The advantages of single‐use bioreactors for the cultivation of the heterotrophic microalgae Crypthecodinium cohnii serves as an example for the feasibility of polymer based orbital shaken systems for shear‐sensitive microorganisms with a high oxygen demand. Experiments in the shake flask scale indicate the advantage of tubes like the TubeSpin Bioreactor 600 in comparison to standard Erlenmeyer flasks. In the screening stage, performed in orbitally shaken deepwell plates, the growth performance is significantly improved by the application of perflourodecalin for the modulation of the gas transfer. The use of orbitally shaken systems from the deepwell plate format over the TubeSpin towards orbitally shaken bioreactors provides a reliable strategy for the consistent bioprocess development and scale up of shear‐sensitive aerobic microorganisms. The consistent scalability of the process up to 200 L is envisaged.
Dynamics and Electronegativity of Oxygen RF Plasmas
Authors: Küllig C. , Dittmann K. , Wegner T. , Sheykin I. , Matyash K. , Loffhagen D. , Schneider R. , Meichsner J.
Published: November 2012

The capacitively coupled radio frequency plasma at 13.56 MHz in oxygen was systematically studied by 160 GHz Gaussian beam microwave interferometry at high temporal resolution (200 ns) and simultaneous laser photodetachment for electron and negative ion density analysis. Additionally, spatio‐temporally resolved electric probe measurements were performed for comparison with microwave interferometry. A high and low electronegative operation mode was found in the asymmetric rf discharge. In the high electronegative mode it was shown the significant role of the metastable excited oxygen molecules in electron attachment and detachment processes. In particular, a temporary electron density increase is observed in the early afterglow of a pulsed rf plasma. The transition between both modes is driven by the rf power and the self‐bias voltage, respectively. In connection with the phase resolved optical emission spectroscopy and the study of the electron heating mechanisms the transition into the low electronegative mode at higher rf power shows a relation to the alpha to gamma mode transition. Furthermore, electron density fluctuations are measured over a wide field of processing parameters, e.g. due to the attachment‐induced ionization instability. PIC‐MCC simulation and fluid model calculation of a symmetric oxygen rf discharge confirm the different electron heating mechanisms and the dominance of negative atomic oxygen ions (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of Sulfite in Hair Waving Products Using Oxygen‐Incorporated Gold‐Modified Screen‐Printed Electrodes
Authors: Chen Pei‐Yen , Huang Chien‐Chang , Chen Mei‐Chin , Hsu Jaw‐Cherng , Shih Ying
Published: November 2012

An electrodeposition oxygen‐incorporated gold‐modified screen‐printed carbon electrode (AuOSPE) was fabricated to determine the sulfite content in hair waving products. The AuOSPE showed an electrocatalytic current for sulfite at +0.4 V (vs. Ag/AgCl). Compared with a gold screen‐printed electrode (AuSPE), the AuOSPE showed a higher electrocatalytic current. The increase in the electrocatalytic current was ascribed to the increase of the oxygen incorporated with gold atom on AuOSPE. The AuOSPE coupled with a flow injection analysis (FIA) system showed excellent oxidation current for sulfite in a 0.1 mol L−1 phosphate buffer solution (PBS), pH 6.0. The linear working range for determining the sulfite content was 0.05 to 1200 mg L−1 (0.625 µmol L−1 to 15.00 mmol L−1) with a calculated detection limit of 0.03 mg L−1 (0.375 µmol L−1) (DL, S/N=3). Relative standard deviations (RSD) of 3.03 %, 2.30 % and 4.26 % were calculated for consecutive injections (n=12) of 20, 300 and 900 mg L−1 sulfite, respectively. The amount of sulfite in two hair waving products was determined by the proposed method and a standard iodometric method. The recoveries ranged from 96.18 % to 105.61 %. The AuOSPE showed high sensitivity, selectivity, stability and reproducibility for sulfite.
Implications of global climate change for the assessment and management of human health risks of chemicals in the natural environment
Authors: Balbus John M. , Boxall Alistair B.A. , Fenske Richard A. , McKone Thomas E. , Zeise Lauren
Published: November 2012

Global climate change (GCC) is likely to alter the degree of human exposure to pollutants and the response of human populations to these exposures, meaning that risks of pollutants could change in the future. The present study, therefore, explores how GCC might affect the different steps in the pathway from a chemical source in the environment through to impacts on human health and evaluates the implications for existing risk-assessment and management practices. In certain parts of the world, GCC is predicted to increase the level of exposure of many environmental pollutants due to direct and indirect effects on the use patterns and transport and fate of chemicals. Changes in human behavior will also affect how humans come into contact with contaminated air, water, and food. Dietary changes, psychosocial stress, and coexposure to stressors such as high temperatures are likely to increase the vulnerability of humans to chemicals. These changes are likely to have significant implications for current practices for chemical assessment. Assumptions used in current exposure-assessment models may no longer apply, and existing monitoring methods may not be robust enough to detect adverse episodic changes in exposures. Organizations responsible for the assessment and management of health risks of chemicals therefore need to be more proactive and consider the implications of GCC for their procedures and processes. Environ. Toxicol. Chem. 2013;32:62–78. © 2012 SETAC
Uptake and toxicity of polycyclic aromatic hydrocarbons in terrestrial springtails—studying bioconcentration kinetics and linking toxicity to chemical activity
Authors: Schmidt Stine Nørgaard , Smith Kilian Eric Christopher , Holmstrup Martin , Mayer Philipp
Published: November 2012

Passive dosing applies a polymer loaded with test compound(s) to establish and maintain constant exposure in laboratory experiments. Passive dosing with the silicone poly(dimethylsiloxane) was used to control exposure of the terrestrial springtail Folsomia candida to six polycyclic aromatic hydrocarbons (PAHs) in bioconcentration and toxicity experiments. Folsomia candida could move freely on the PAH-loaded silicone, resulting in exposure via air and direct contact. The bioconcentration kinetics indicated efficient uptake of naphthalene, anthracene, and pyrene through air and (near) equilibrium partitioning of these PAHs to lipids and possibly the waxy layer of the springtail cuticle. Toxicities of naphthalene, phenanthrene, and pyrene were related to chemical activity, which quantifies the energetic level and drives spontaneous processes including diffusive biouptake. Chemical activity–response relationships yielded effective lethal chemical activities (La50s) well within the expected range for baseline toxicity (0.01–0.1). Effective lethal body burdens for naphthalene and pyrene exceeded the expected range of 2 to 8 mmol kg−1 fresh weight, which again indicated the waxy layer to be a sorbing phase. Finally, chemical activities were converted into equilibrium partitioning concentrations in lipids yielding effective lethal concentrations for naphthalene and phenanthrene in good correspondence with the lethal membrane burden for baseline toxicity (40–160 mmol kg−1 lipid). Passive dosing was a practical approach for tightly controlling PAH exposure, which in turn provided new experimental possibilities and findings. Environ. Toxicol. Chem. 2013;32:361–369. © 2012 SETAC
Relationship of land use and elevated ionic strength in Appalachian watersheds
Authors: Cormier Susan M. , Wilkes Samuel P. , Zheng Lei
Published: November 2012

Coal mining activities have been implicated as sources that increase stream specific conductance in Central Appalachia. The present study characterized potential sources of elevated ionic strength for small subwatersheds within the Coal, Upper Kanawha, Gauley, and New Rivers in West Virginia. From a large monitoring data set developed by the West Virginia Department of Environmental Protection, 162 < 20–km2-watersheds were identified that had detailed land cover information in southwestern West Virginia with at least one water chemistry sample. Scatter plots of specific conductance were generated for nine land cover classifications: open water, agriculture, forest, residential, barren, total mining, valley fill, abandoned mine lands, and mining excluding valley fill and abandoned mine lands. Conductivity was negatively correlated with the percentage of forest area and positively associated with other land uses. In a multiple regression, the percentage of area in valley fill was the strongest contributor to increased ionic strength, followed by percentage of area in urban (residential/buildings) land use and other mining land use. Based on the 10th quantile regression, 300 µS/cm was exceeded at 3.3% of area in valley fill. In most catchments, HCO 3− and SO 42− concentrations were greater than Cl− concentration. These findings confirm coal mining activities as the primary source of high conductivity waters. Such activities might be redressed with the goal of protecting sources of dilute freshwater in the region. Environ. Toxicol. Chem. 2013;32:296–303. © 2012 SETAC
A method for assessing causation of field exposure–response relationships
Authors: Cormier Susan M. , Suter II Glenn W.
Published: November 2012

Because associations between agents and environmental effects are not necessarily causal, it is necessary to assess causation before using such relationships in environmental management. The authors adapted epidemiological methods to assess general causal hypotheses. General causation establishes that an agent is capable of causing an effect. The method uses all relevant and good-quality evidence in a weight-of-evidence system. The system is credible due to its explicit a priori criteria. The evidence is organized in terms of six characteristics of causation: co–occurrence, preceding causation, interaction, alteration, sufficiency, and time order. The causal assessment proceeds through six steps that generate, organize, and score evidence to determine whether causation is adequately supported by the body of evidence. Environ. Toxicol. Chem. 2013;32:272–276. © 2012 SETAC
A method for deriving water-quality benchmarks using field data
Authors: Cormier Susan M. , Suter II Glenn W.
Published: November 2012

The authors describe a methodology that characterizes effects to individual genera observed in the field and estimate the concentration at which 5% of genera are adversely affected. Ionic strength, measured as specific conductance, is used to illustrate the methodology. Assuming some resilience in the population, 95% of the genera are afforded protection. The authors selected an unambiguous effect, the presence or absence of a genus from sampling locations. The absence of a genus, extirpation, is operationally defined as the point above which only 5% of the observations of a genus occurs. The concentrations that cause extirpation of each genus are rank-ordered from least to greatest, and the benchmark is estimated at the 5th percentile of the distribution using two-point interpolation. When a full range of exposures and many taxa are included in the model of taxonomic sensitivity, the model broadly characterizes how species in general respond to a concentration gradient of the causal agent. This recognized U.S. Environmental Protection Agency methodology has many advantages. Observations from field studies include the full range of conditions, effects, species, and interactions that occur in the environment and can be used to model some causal relationships that laboratory studies cannot. Environ. Toxicol. Chem. 2013;32:255–262. © 2012 SETAC
A practical quantification method for Heinz bodies in birds applicable to rapid response field scenarios
Authors: Fallon Jesse A. , Hopkins William A. , Fox Lee
Published: November 2012

Oil-induced oxidative injury to red blood cells results in Heinz body hemolytic anemia. Here, we evaluated three Heinz body staining techniques in brown pelican (Pelecanus occidentalis) blood. Using a range of in vitro acetylphenylhydrazine incubations, we validated a field-adapted technique against laboratory wet-mounts and verified the stability of this technique for one month following preparation. Employing this technique during petrochemical spill responses allows for delays between sample collection and analysis. Environ. Toxicol. Chem. 2013;32:401–405. © 2012 SETAC
Assessing causation of the extirpation of stream macroinvertebrates by a mixture of ions
Authors: Cormier Susan M. , Suter Glenn W. , Zheng Lei , Pond Gregory J.
Published: November 2012

Increased ionic concentrations are associated with the impairment of benthic invertebrate assemblages. However, the causal nature of that relationship must be demonstrated so that it can be used to derive a benchmark for conductivity. The available evidence is organized in terms of six characteristics of causation: co–occurrence, preceding causation, interaction, alteration, sufficiency, and time order. The inferential approach is to weight the lines of evidence using a consistent scoring system, weigh the evidence for each causal characteristic, and then assess the body of evidence. Through this assessment, the authors found that a mixture containing the ions Ca+, Mg+, HCO 3−, and SO 4−, as measured by conductivity, is a common cause of extirpation of aquatic macroinvertebrates in Appalachia where surface coal mining is prevalent. The mixture of ions is implicated as the cause rather than any individual constituent of the mixture. The authors also expect that ionic concentrations sufficient to cause extirpations would occur with a similar salt mixture containing predominately HCO 3−, SO 42−, Ca2+, and Mg2+ in other regions with naturally low conductivity. This case demonstrates the utility of the method for determining whether relationships identified in the field are causal. Environ. Toxicol. Chem. 2013;32:277–287. © 2012 SETAC
Application of multiple geochemical markers to investigate organic pollution in a dynamic coastal zone
Authors: Liu Liang-Ying , Wang Ji-Zhong , Wong Charles S. , Qiu Jian-Wen , Zeng Eddy Y.
Published: November 2012

Multiple geochemical markers, including aliphatic hydrocarbons (n-alkanes), linear alkylbenzenes (LABs), and polycyclic aromatic hydrocarbons (PAHs), were employed to relate sediment organic chemical pollution in the coastal zone off South China to socioeconomic development there. Concentrations of Σn-C15-35 (n-alkanes with 15–35 carbon atoms), ΣLAB (sum of C10 to C13 LABs), and Σ26PAH (sum of 26 PAH compounds) ranged from 110 to 3,160, 11 to 160, and 26 to 600 ng/g, with medians of 730, 40, and 230 ng/g, respectively. Natural hydrocarbons were mainly derived from terrestrial higher plant waxes, and in minor amounts from aquatic plankton and bacteria. Compositions of LABs indicated that considerable amounts of poorly treated wastewater had been directly discharged or transported to the eastern and western coastal areas of Guangdong Province. In addition, anthropogenic hydrocarbons were derived largely from vehicular emissions and combustion of domestic coal and biomass and to a lesser extent from oil spills. Eastern and western coastal sediments contained higher levels of LABs but lower levels of PAHs than those of the Pearl River Estuary, a coastal area of the Pearl River Delta. This spatial pattern of organic pollution was consistent with chemical use patterns. The eastern and western regions of Guangdong Province are economically less developed than the Pearl River Delta region, where more domestic wastewater treatment plants have been built. However, greater amounts of energy are consumed in the latter region to produce more combustion-derived PAH contamination. Environ. Toxicol. Chem. 2013;32:312–319. © 2012 SETAC
Metals and bacteria partitioning to various size particles in Ballona creek storm water runoff
Authors: Brown Jeffrey S. , Stein Eric D. , Ackerman Drew , Dorsey John H. , Lyon Jessica , Carter Patrick M.
Published: November 2012

Many storm water best management practice (BMP) devices function primarily by capturing particulate matter to take advantage of the well-documented association between storm water particles and pollutants. The hydrodynamic separation or settling methods used by most BMP devices are most effective at capturing medium to large particles; however, these may not be the most predominant particles associated with urban runoff. The present study examined particle size distribution in storm water runoff from an urban watershed in southern California and investigated the pollutant–particle associations of metals (Cu, Pb, Ni, and Zn) and bacteria (enterococci and Escherichia coli). During small storm events (≤0.7 cm rain), the highest concentration of pollutants were associated with a <6-µm filter fraction, which accounted for 70% of the per storm contaminant mass but made up more than 20% of the total particle mass. The pollutant–particle association changed with storm size. Most pollutant mass was associated with >35 µm size particles during a 5-cm rain event. These results suggest that much of the contaminant load in storm water runoff will not be captured by the most commonly used BMP devices, because most of these devices (e.g., hydrodynamic separators) are unable to capture particles smaller than 75 µm. Environ. Toxicol. Chem. 2013;32:320–328. © 2012 SETAC