bluuebunny/crossref_metadata_2025 huggingface dataset:
In silico Prediction of Human Oral Absorption Based on QSAR Analyses of PAMPA Permeability
Authors: Akamatsu Miki , Fujikawa Masaaki , Nakao Kazuya , Shimizu Ryo
Published: November 2009

The parallel artificial membrane permeation assay (PAMPA) was developed as a model for the prediction of transcellular permeation in the process of drug absorption. Our research group has measured the PAMPA permeability of peptide‐related compounds, diverse drugs, and agrochemicals. This work led to a classical quantitative structure–activity relationship (QSAR) equation for PAMPA permeability coefficients of structurally diverse compounds based on simple physicochemical parameters such as lipophilicity at a particular pH (log Poct and |pKa−pH|), H‐bond acceptor ability (SAHA), and H‐bond donor ability (SAHD). Since the PAMPA permeability of lipophilic compounds decreased with their apparent lipophilicity due to the unstirred water layer (UWL) barrier on membrane surfaces and to membrane retention, a bilinear QSAR model was introduced to explain the permeability of a broader set of compounds using the same physicochemical parameters as those used for the linear model. We also compared PAMPA and Caco‐2 cell permeability coefficients of compounds transported by various absorption mechanisms. The compounds were classified according to their absorption pathway (passively transported compounds, actively transported compounds, and compounds excreted by efflux systems) in the plot of Caco‐2 vs. PAMPA permeability. Finally, based on the QSAR analyses of PAMPA permeability, an in silico prediction model of human oral absorption for possibly transported compounds was proposed, and the usefulness of the model was examined.
Small Chemicals, Bioactivation, and the Immune System – A Fragile Balance of i‐Tox and Benefits?
Authors: Esser Charlotte , Jux Bettina
Published: November 2009

Immunotoxicology concerns actions of chemicals which lead to adverse immune reactions. Current research challenges are the prediction of the immunotoxicologic risk potential of a chemical and a deeper mechanistic understanding of chemical‐induced adverse immune reactions, to develop therapeutic or avoidance strategies. Small chemicals (SCs) can interfere with any cell type or function of the immune system. SCs are ubiquitous as food components, life‐style products, or environmental pollutants. Besides their possible unspecific toxicity, they might form protein adducts, become part of recognized antigens, or they could be disruptors of immune signalling pathways. The incidence of autoimmune and allergic diseases has been rising over the last years, and evidence increases that SCs are important in this. Also, immunopharmacologists actively search for immunomodulating chemicals as urgently needed drugs. The aryl hydrocarbon receptor (AhR) is a SC‐triggered transcription factor, and thus could link environmental signals to cellular responses. Recent research has shown a defined role for AhR in immunotoxicology. Here, we discuss concepts of SC immunotoxicity, and how AhR might be involved in adverse immune responses.
RNA‐Interference Approach to Study Functions of NADPH : Cytochrome P450 Oxidoreductase in Human Hepatocytes
Authors: Feidt Diana M. , Klein Kathrin , Nüssler Andreas , Zanger Ulrich M.
Published: November 2009

Human NADPH : cytochrome P450 oxidoreductase (POR) is encoded by a single gene on chromosome 7q11.2. This flavoprotein donates electrons derived from NADPH to a variety of acceptor proteins, including squalene monooxygenase, heme oxygenase, cytochrome b5, and many microsomal cytochromes P450 (CYPs), which are involved in oxidative drug metabolism, steroidogenesis, and other functions. Numerous aspects related to cellular POR expression have not been systematically investigated. Interestingly, POR expression is lower compared to CYPs and may thus be limiting for monooxygenase activities, but conversely, POR knock‐out in mice resulted in compensatory upregulation of CYPs. POR may also influence intracellular cholesterol and lipid homeostasis. To systematically investigate such effects, we developed specific POR gene silencing in cell lines and primary human hepatocytes by RNA interference using small interfering RNAs (siRNAs). In HepG2 cells, POR mRNA could be reduced by 95% over 4 days accompanied by reduced protein content and activity. In primary human hepatocytes, POR mRNA knock‐down was less effective and more variable. Analysis of CYPs indicated induction of CYP3A4 but not CYP1A2 or CYP2D6. These results demonstrate that POR can be efficiently and almost completely silenced in HepG2 cells and, at least partially, in primary human hepatocytes. This will allow systematic studies of various consequences of POR variability in human cells.
A PAMPA Study of the Permeability‐Enhancing Effect of New Ceramide Analogues
Authors: Sinkó Bálint , Kökösi József , Avdeef Alex , Takács‐Novák Krisztina
Published: November 2009

There is a major need in drug discovery for quick, precise, and cost‐effective high‐throughput screening (HTS) systems in the early stages of drug research. The Parallel Artificial Membrane Permeability Assay (PAMPA) aims at predicting the passive membrane properties of drugs. Since 1998, model membranes have been developed to predict gastro‐intestinal absorption or transport through the blood–brain barrier. This paper presents recent results in a project aiming to improve the prediction of transdermal penetration. Using the PAMPA system, we investigated the effect of four newly synthetized ceramide analogues (certramides) on the permeability of three model compounds (ciprofloxacin, nifedipine, and verapamil). The certramides differ in the length of one alkyl chain, while the other alkyl chain and the head group remained the same. A relationship between the membrane concentration of certramides (from 0 to 100%) and the permeability of compounds was found, and the results of different certramides were compared. The strongest effect on permeability was caused by the ceramide analogue CTR(C12–C16). The reproducibility of the experiments and the impact of presence or absence of organic solvents (dodecane and CHCl3) in the membrane were also investigated.
In silico pKa Prediction and ADME Profiling
Authors: Cruciani Gabriele , Milletti Francesca , Storchi Loriano , Sforna Gianluca , Goracci Laura
Published: November 2009

Improving the ADME profile of drug candidates is a critical step in lead optimization, and because pKa affects most ADME properties such as lipophilicity, solubility, and metabolism, it is extremely advantageous to predict pKa in order to guide the design of new compounds. However, accurately (<0.5 log units) predicting pKa by empirical methods can be challenging especially for novel series, because of lack of knowledge on determinants of pKa (steric effects, ring effects, H‐bonding, etc.), and because of limited experimental data on the effects of specific chemical groups on the ionization of an atom. To address these issues, we recently developed the computational package MoKa, which integrates graphical and command line tools designed for computational and medicinal chemists to predict the pKa values of organic compounds. Here, we present the major issues considered when we developed MoKa, such as the accurate selection of training data, the fundamentals of the methodology (which has also been extended to predict protein pKa), the treatment of multiprotic compounds, and the selection of the dominant tautomer for the calculation. Last, we illustrate some specific applications of MoKa to predict solubility, lipophilicity, and metabolism.
Transporters in Absorption, Distribution, and Elimination
Authors: Scherrmann Jean‐Michel
Published: November 2009

During the past decades, pharmacokinetics has been defined as the study of drug absorption, distribution, metabolism, and excretion (ADME), when the drug is introduced into a biological system, such as the human body. Pharmacokinetics is now challenged by the growing importance of transporters, a relatively new and potentially major factor in drug ADME. The recent intrusion of drug transporters means that there is no single mechanism by which drugs permeate through membranes. The presence of transporters in membranes modulates the traditional theory of ‘diffusional pharmacokinetics’ towards ‘vectorial pharmacokinetics’ in which ADME processes are governed more deterministically. Drug transporters are also clinically important. They can modulate the pharmacological activity of drugs by affecting their intracellular concentrations and causing toxicity in specific organs due to intracellular drug accumulation. Finally, they are key players in drug–drug interactions, where they are as important as the drug metabolizing enzymes.
Oxidation of an Oligonucleotide‐Bound CeIII/Multiphosphonate Complex for Site‐Selective DNA Scission
Authors: Lönnberg Tuomas , Aiba Yuichiro , Hamano Yuya , Miyajima Yoshitaka , Sumaoka Jun , Komiyama Makoto
Published: November 2009

Oligodeoxyribonucleotide conjugates of ethylenediamine‐N,N,N′,N′‐tetrakis(methylenephosphonic acid) (EDTP) have been used to place a CeIII/EDTP complex in close proximity to predetermined phosphodiester linkages of a complementary target oligonucleotide. In the presence of atmospheric oxygen, the CeIII is oxidized into CeIV which, in turn, efficiently cleaves the target phosphodiester linkage. No cleavage occurs at the other single‐stranded regions, which suggests that the catalytic Ce species is strictly localized next to the target phosphodiester linkage. No decrease in the reaction rate is observed upon introduction of scavengers for hydroxyl radicals (such as DMSO or MeOH) or singlet oxygen (such as NaN3) to the system; this indicates that the reaction proceeds via a hydrolytic pathway. Any significant contribution by an oxidative pathway is further ruled out by the observation that nucleosides remain intact after incubation with CeIV/EDTP complex for extended periods.
Bonding Trends in Molecular Compounds of Lanthanides: The Double‐Bonded Carbene Cations LnCH2+ (Ln=Sc, Y, La–Lu)
Authors: Roos Björn O. , Pyykkö Pekka
Published: November 2009

Quasi‐relativistic Douglas–Kroll CASPT2 calculations are reported for the title molecules, mainly to provide primary data for a fit of double‐bond covalent radii. Indeed, a well‐developed σ2π2 double bond is identified in all cases. For Eu and Yb, however, it is an excited state. The main valence orbitals of all Ln ions are 6s and 5d. In the σ bonds, more 5d than 6s character is found at the Ln. The LnC bond lengths show a systematic lanthanide contraction of 13 pm from La to Lu. An agostic symmetry breaking is demonstrated for Ce but its effect on the LnC length is small.
Bioinspired interactions studied by vibrational circular dichroism
Authors: Urbanová Marie
Published: November 2009

Vibrational circular dichroism (VCD) spectra are reliable indicators of the spatial structure of chiral molecules. The specific and characteristic feature of vibrational spectroscopy, and therefore also of VCD, where the energy of some vibrational modes is predominantly focused to a specific part of the molecule, enables monitoring both the structure of the molecule dissolved in different solvents and under different physicochemical conditions and molecular interactions. This minireview deals with recent contributions covering structural information on the bioinspired interactions obtained by means of VCD, especially in the following areas: interaction of DNA with biomolecules and biogenic metals, guanine tetramers and quadruplexes, biointeractions of bile pigments, and polypeptide and protein interactions with other biomolecules. Chirality 21:E215–E230, 2009. © 2009 Wiley‐Liss, Inc.
The extended website stage model: a study of Canadian winery websites
Authors: Zhu Ying , Basil Debra Z. , Hunter M. Gordon
Published: November 2009

Rao, Metts, and Mora Monge (2003) proposed a stage model to reflect the progression small businesses follow in their use of Internet technology. We extend their work in two ways. We introduce marketing integration into this technology‐focused model and further differentiate the transactions stage of the framework. We then use the model to examine differences in the degree of sophistication of websites used by businesses in the Canadian winery sector. Data collection entailed a content analysis on a census of English language Canadian winery websites (N = 206). A supplementary survey was used to distinguish among those sites that were making use of relatively advanced technologies. A multinomial logit analysis was applied to examine a series of research questions based upon our integrated model. Implications of the findings for scholarship and practice are discussed. Copyright © 2009 ASAC. Published by John Wiley & Sons, Ltd.
Amazon's evolving ecosystem: A cyber‐bookstore and Application Service Provider
Authors: Isckia Thierry
Published: November 2009

Amazon.com has been through several stages of development: first as a cyber‐bookstore, then a cyber‐market, and now an Application Service Provider (ASP). I apply the concept of “business ecosystem” to describe the evolution of Amazon.com, and highlight the role of web services in the shaping of its ecosystem. The company plays a central role in the ecosystem, working with a network of partners to bring products and services to customers. By continually trying to improve the health of its ecosystem, Amazon ensures its own survival and prosperity. The mechanisms through which Amazon has created its ecosystem are discussed and ideas for firms looking to create analogous business communities are advanced. Copyright © 2009 ASAC. Published by John Wiley & Sons, Ltd.
Salting‐out crystallisation using NH3 in a laboratory‐scale gas lift reactor
Authors: Jenkins D. H.
Published: November 2009

Despite the advantages offered by gas lift reactors with respect to high gas–liquid mass transfer with a low energy input, their acceptance in the crystallisation field has been slow, especially on an industrial scale. Potassium chloride, potassium sulfate, and magnesium chloride hexammoniate (MgCl2·6NH3) were crystallised in a laboratory‐scale gas lift crystalliser by salting‐out using ammonia gas. Ammonia mass transfer rates were calculated for each test. To achieve maximum crystal growth, the gas rate in these reactors needs to be optimised for each crystallising system to achieve sufficient gas mass transfer as well as providing sufficient crystal slurry agitation.
Effect of gas distributor on hydrodynamics in shallow bubble column reactors
Authors: Lau Raymond , Sim Wei Shan Beverly , Mo Rujuan
Published: November 2009

The effects of gas distributor on hydrodynamics in an air–water shallow bubble column reactor are investigated. Three types of distributors, namely, single nozzle, perforated plate and porous plate are being studied. The overall gas holdup, bubble size distributions and bubble rise velocity distributions are studied over a range of superficial gas velocities. The results show that single nozzle is not suitable for shallow bed operation. While perforated plate and porous plate distributors have comparable behaviour in the absence of solids, the addition of solids particles causes the two distributors to behaviour differently. The presence of solids promotes bubble coalescence for perforated plate distributor while the same inhibits bubble coalescence for porous plate distributor.
Study of nitric acid leachout characteristics from weak base anion exchanger to maintain a specified pH regime during Gd(NO3)3 removal from moderator system of 540 MWe PHWRs
Authors: Tripathi V. S. , Balaji V. , Venkateswaran G. , Dash S. C.
Published: November 2009

Nitric acid leachout characteristics from weak base anion exchanger (WBA) have been experimentally evaluated as a function of total nitric acid loading at a given flow velocity. An empirical first order model is used to explain the column outlet behaviour. Based on the experimental evaluation, a column configuration of a strong acid cation exchanger (SAC) topped mixed bed of SAC and WBA followed by a 5% nitric acid loaded WBA as the bottom layer of the column has been used to remove Gd(NO3)3 from water while maintaining the column outlet pH in the range of 5.0–5.5.
Comparison of Long‐term Outcomes Following Sirolimus‐eluting Stent vs Paclitaxel‐eluting Stent Implantation in Patients with Long Calcified Coronary Lesions
Authors: Hur Seung‐Ho , Cho Yun‐Kyeong , Nam Chang‐Wook , Kim Hyungseop , Han Seong‐Wook , Kim Yoon‐Nyun , Park Hee‐Joon , Park Jong‐Seon , Shin Dong‐Gu , Kim Young‐Jo , Shim Bong‐Sup , Yang Tae‐Hyun , Kim Dae‐Kyeong , Kim Doo‐Il , Kim Dong‐Soo , Kim Kwon‐Bae
Published: November 2009

Background

Although previously reported studies on coronary calcification mainly focused on its presence or absence in discrete focal target lesions, calcified coronary lesions (CCL) angiographically present as diffuse long lesions in some patients. The aim of our study was to evaluate the long‐term efficacy of sirolimus‐eluting stents (SES) and paclitaxel‐eluting stents (PES) on long CCL.

Methods

A total of 122 patients with 134 lesions (77 patients with 88 lesions for SES and 45 patients with 46 lesions for PES) were enrolled from 3 centers. Long CCL was defined visually as a culprit lesion with type B or C that was mainly due to coronary calcification with > 20 mm in total length by coronary angiography. Clinical follow‐up was performed at 1 year and angiographic follow‐up at 6 to 9 months after procedure. Major adverse coronary events (MACE) were defined as all‐cause death, myocardial infarction (MI), and repeat target‐lesion revascularization (TLR).

Results

There were no statistically significant differences in baseline, procedural, or angiographic characteristics and in 1‐year rates of all‐cause death, MI, and TLR between the 2 groups (all P = NS [not significant]). Likewise, the cumulative incidence of MACE at 1 year was similar between the 2 groups (7.8% of patients in the SES group vs 4.4% of patients in the PES group, respectively, P = NS). In patients who underwent follow‐up angiography, the angiographic binary restenosis rate was 6.2% in the SES group vs 12.1% in the PES group, respectively (P = NS).

Conclusion

In patients with long CCL, both SES and PES were comparably effective in either angiographic or clinical long‐term outcomes. Copyright © 2009 Wiley Periodicals, Inc.
Myocardial Revascularization: PCI/Stent or Coronary Artery Bypass Graft—What Is Best for Our Patients?
Authors: Richard Conti C.
Published: November 2009

In my opinion, decisions regarding which type of revascularization is to be performed on a specific patient depends on vessel anatomic pathology, (ie, coronary lesion complexity). Thus, for proper decision‐making regarding the selection of the revascularization procedure, the details of the coronary angiogram, not just the number of vessels involved, must be discussed by the interventional cardiologist as well as the cardiovascular surgeon. Copyright © 2009 Wiley Periodicals, Inc.
Survey on human papillomavirus/p16 screening use in oropharyngeal carcinoma patients in the United States
Authors: Shoushtari Asal N. , Rahimi Nina P. , Schlesinger David J. , Read Paul W.
Published: November 2009

BACKGROUND:

Patients with human papillomavirus (HPV)‐positive oropharyngeal carcinoma (OC) have better prognosis than patients with HPV‐negative OC. The objective of the current study was to assess how different practices across the United States treat patients with OC with respect to screening for HPV DNA or p16.

METHODS:

Five hundred forty‐two randomly selected radiation oncologists were sent an 11‐question survey by email regarding the use of HPV/p16 screening in OC. The questionnaire addressed demographics of the practice, intensity‐modulated radiotherapy (IMRT) use, screening practices for HPV DNA or p16, which year this began, the use of HPV or p16 data to direct patient care, and future plans for its use if it had not already been instituted.

RESULTS:

One hundred ninety‐two responses (39.6%) were received. Thirty‐five percent of respondents (67 of 188) reported screening for HPV DNA routinely, whereas 4.8% of respondents (9 of 188) reported screening for p16. Of the physicians who did not use screening techniques, 37.2% (44 of 118 respondents) reported future plans to institute these screening techniques, 20% (9 of 45 respondents) stated plans to institute these techniques in the next 6 months, 55.5% (25 of 45 respondents) stated plans to institute these techniques within 6 months to 1 year, and 22.2% (10 of 45 respondents) stated plans to institute these techniques within 1 to 2 years. Academic physicians were more likely to use screening techniques (62.7%; P < .001) compared with private practitioners (31.4%). Only 12.4% of respondents reported using HPV or p16 data to direct care.

CONCLUSIONS:

Approximately 40.4% of radiation oncology practices that responded to a survey in the United States screened for HPV DNA or p16 in OC, whereas only 12.4% used it to further direct care. This number appears to be growing rapidly. Clinical trials to further elucidate how HPV or p16 status should direct care in OC are warranted. Cancer 2010. © 2010 American Cancer Society.
Expression of PTPRO in the interneurons of adult mouse olfactory bulb
Authors: Kotani Takenori , Murata Yoji , Ohnishi Hiroshi , Mori Munemasa , Kusakari Shinya , Saito Yasuyuki , Okazawa Hideki , Bixby John L. , Matozaki Takashi
Published: November 2009

PTPRO is a receptor‐type protein tyrosine phosphatase (PTP) with a single catalytic domain in its cytoplasmic region and multiple fibronectin type III‐like domains in its extracellular region. In the chick, PTPRO mRNA has been shown to be particularly abundant in embryonic brain, and PTPRO is implicated in axon growth and guidance during embryonic development. However, the temporal and spatial expression of PTPRO protein in the mammalian CNS, particularly in the juvenile and adult mammalian brain, has not been evaluated in any detail. By immunohistofluorescence analysis with a monoclonal antibody to PTPRO, we show that PTPRO is widely expressed throughout the mouse brain from embryonic day 16 to postnatal day 1, while expression is largely confined to the olfactory bulb (OB) and olfactory tubercle in the adult brain. In the OB, PTPRO protein is expressed predominantly in the external plexiform layer, the granule cell layer, and the glomerular layer (GL). In these regions, expression of PTPRO is predominant in interneurons such as γ‐aminobutyric acid (GABA)‐ergic or calretinin (CR)‐positive granule cells. In addition, PTPRO is expressed in GABAergic, CR‐positive, tyrosine hydroxylase‐positive, or neurocalcin‐positive periglomerular cells in the GL. Costaining of PTPRO with other neuronal markers suggests that PTPRO is likely to be localized to the dendrites or dendritic spines of these olfactory interneurons. Thus, PTPRO might participate in regulation of dendritic morphology or synapse formation of interneurons in the adult mouse OB. J. Comp. Neurol. 518:119–136, 2010. © 2009 Wiley‐Liss, Inc.
Scalable packet classification using a compound algorithm
Authors: Wang Pi‐Chung
Published: November 2009

In next‐generation networks, packet classification is used to categorize incoming packets into multiple forwarding classes based on pre‐defined filters and make information accessible for quality of service or security handling in the network. To pursue better search performance, numerous algorithms of packet classification have been proposed and optimized for certain filter databases; however, these algorithms may not scale in either storage or speed performance or both for the filter databases with different characteristics. This paper presents an efficient algorithm by combining two complementary algorithms,Cross‐productingandPruned Tuple Space Search, to make packet classification both fast and scalable. Unlike the existing algorithms whose performance is contingent on the filter database attributes, our algorithm shows better scalability and feasibility. We evaluate the performance of our scheme with filter databases of varying sizes and characteristics. The experimental results demonstrate that the new algorithm improves the speed and storage performance simultaneously. We also introduce the procedure of incremental updates. Copyright © 2009 John Wiley & Sons, Ltd.
The development of stimulus‐specific auditory responses requires song exposure in male but not female zebra finches
Authors: Maul Kristen K. , Voss Henning U. , Parra Lucas C. , Salgado‐Commissariat Delanthi , Ballon Douglas , Tchernichovski Ofer , Helekar Santosh A.
Published: November 2009

Juvenile male zebra finches develop their song by imitation. Females do not sing but are attracted to males' songs. With functional magnetic resonance imaging and event‐related potentials we tested how early auditory experience shapes responses in the auditory forebrain of the adult bird. Adult male birds kept in isolation over the sensitive period for song learning showed no consistency in auditory responses to conspecific songs, calls, and syllables. Thirty seconds of song playback each day over development, which is sufficient to induce song imitation, was also sufficient to shape stimulus‐specific responses. Strikingly, adult females kept in isolation over development showed responses similar to those of males that were exposed to songs. We suggest that early auditory experience with songs may be required to tune perception toward conspecific songs in males, whereas in females song selectivity develops even without prior exposure to song. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 2010
Amino–Acetone‐Bridged Cyclodextrins ― Artificial Alcohol Oxidases
Authors: Marinescu Lavinia G. , Doyagüez Elisa G. , Petrillo Marta , Fernández‐Mayoralas Alfonso , Bols Mikael
Published: November 2009

A new series of α‐ and β‐cyclodextrin derivatives containing a substituted amino–acetone bridge attached to the 6A and 6D positions of the cyclodextrin are reported. The synthesis starts from the known α‐ or β‐cyclodextrin A,D‐diols, which were either oxidized to α‐ or β‐cyclodextrin A,D‐dicarbaldehydes and then coupled with 1,3‐diamino‐2‐propanol by a reductive amination reaction and further modified to give the final 6A,6D‐diamino‐6A,6D‐dideoxy‐N,N′‐(2‐oxopropa‐1,3‐dienyl)‐N,N′‐acetyl‐α‐ or ‐β‐cyclodextrin or the cyclodextrin‐diol was substituted with azide then reduced and after a few alkylation steps the final 6A,6D‐dideoxy‐N,N′‐(2‐oxopropa‐1,3‐dienyl)‐6A,6D‐(N,N,N′N′‐tetramethyldiammonio)‐α‐cyclodextrin dibromide was obtained. The new compounds display very good enzymatic catalytic properties in the oxidation of benzyl alcohols with a rate increase of up to 18500 but only appreciable catalysis for aniline oxidations. Thus, unlike previously studied cyclodextrin ketones, these new amino–acetone‐bridged cyclodextrins have high substrate selectivity and also exhibit stereoselectivity in the oxidation of different enantiomers.
Sensitized Lanthanide‐Ion Luminescence with Aryl‐Substituted N‐(2‐Nitrophenyl)acetamide‐Derived Chromophores
Authors: Andrews Michael , Ward Benjamin D. , Laye Rebecca H. , Kariuki Benson M. , Pope Simon J. A.
Published: November 2009

The syntheses of the two tetraazamacrocyclic ligands L1 and L2 bearing a [(methoxy‐2‐nitrophenyl)amino]carbonyl chromophore, i.e., an N‐(methoxy‐2‐nitrophenyl)acetamide moiety, together with their corresponding lanthanide‐ion complexes are described. A combined spectroscopic (UV/VIS, 1H‐NMR), structural (X‐ray), and theoretical (DFT) investigation revealed that the absorption properties of the chromophores were dictated by the extent of electronic delocalisation, which in turn was determined by the position of the MeO substituent at the aromatic ring. X‐Ray crystallographic studies showed that when attached to the macrocycle, both isomeric forms of the N‐(methoxy‐2‐nitrophenyl)acetamide unit can participate in coordination, via the CO, to an encapsulated potassium cation. Luminescence measurements confirmed that such a binding mode also exists in solution for the corresponding lanthanide complexes (q ca. ≤1), with the para‐MeO derivative allowing longer wavelength sensitization (λex 330 nm).
Near‐Infrared Luminescence Sensing of Glutamic Acid, Aspartic Acid, and Their Dipeptides with Tris(β‐diketonato)lanthanide Probes
Authors: Tsukube Hiroshi , Yano Keiko , Shinoda Satoshi
Published: November 2009

A series of tris(β‐diketonato)lanthanides with Yb3+, Eu3+, and Nd3+ centers were characterized as luminescent sensing probes specific to glutamic acid, aspartic acid, and their dipeptides, which are important substrates involved in nervous systems, taste receptors, and other biological systems. In particular, tris(6,6,7,7,8,8,8‐heptafluoro‐2,2‐dimethyloctane‐3,5‐dionato)ytterbium(III) exhibited a near‐infrared emission around 980 nm in response to these biological substrates. Near‐infrared‐emissive complexes have several advantages over common luminescent probes; therefore, the proposed lanthanide complexes have potential analytical applications in proteomics, metabolics, food science, astrobiology, and related technologies.
Multiple‐Frequency and Variable‐Temperature EPR Study of Gadolinium(III) Complexes with Polyaminocarboxylates: Analysis and Comparison of the Magnetically Dilute Powder and the Frozen‐Solution Spectra
Authors: Benmelouka Meriem , Van Tol Johan , Borel Alain , Nellutla Saritha , Port Marc , Helm Lothar , Brunel Louis‐Claude , Merbach André E.
Published: November 2009

An electron paramagnetic resonance (EPR) study of glasses and magnetically dilute powders of [Gd(DTPA)(H2O)]2−, [Gd(DOTA)(H2O)]−, and macromolecular gadolinate(1−) complexes P792 was carried out at the X‐ and Q‐bands and at 240 GHz (DTPA=diethylenetriaminepentaacetato; DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetato). The results show that the zero‐field splitting (ZFS) parameters for these complexes are quite different in a powder as compared to the frozen aqueous solution. In several complexes, an inversion of the sign of the axial component D of the zero field splitting is observed, indicating a significant structural change. In contrary to what was expected, powder samples obtained by lyophilization do not allow a more precise determination of the static ZFS parameters. The results obtained in glasses are more relevant to the problem of electron spin relaxation in aqueous solution than those obtained from powders.
Reactivity Towards Europium(III) of the Radiolysis Products of the Ionic Liquid 1‐Methyl‐3‐butyl‐1H‐imidazolium Bis[(trifluoromethyl)sulfonyl]amide (C4‐mimTf2N) and Effect of Water: A TRLFS (Time‐Resolved Laser‐Induced Fluorescence Spectroscopy) Preliminary Study
Authors: Billard Isabelle , Georg Sylvia
Published: November 2009

The effect of laser irradiation at λexc 266 nm onto the fluorescence characteristics of EuIII in solution of the ionic liquid 1‐methyl‐3‐butyl‐1H‐imidazolium bis[(trifluoromethyl)sulfonyl]amide (C4‐mimTf2N) was examined for various amounts of H2O added. Stable radiolytic products that were generated at very low doses (in the range of 4 kGy) were very reactive with EuIII and led to the appearance of a new europium luminescent species that was characterized by lifetime, relative intensity, and emission spectrum. Although the lifetime and the intensity depended on the H2O content, the emission spectrum was not influenced by H2O. It was shown that large amounts of H2O, although not preventing radiolysis of C4‐mimTf2N, inhibited the complexation with EuIII.
Metal‐Ion Sensing Europium(III) Complexes with Bidentate Phosphine Oxide Ligands Containing a 2,2′‐Bipyridine Framework
Authors: Hasegawa Yasuchika , Hieda Ryo , Nakagawa Tetsuya , Kawai Tsuyoshi
Published: November 2009

Novel EuIII complexes with bidentate phosphine oxide ligands containing a bipyridine framework, i.e., [3,3′‐bis(diphenylphosphoryl)‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)3(BIPYPO)]) and [3,3′‐bis(diphenylphosphoryl)‐6,6′‐dimethyl‐2,2′‐bipyridine]tris(hexafluoroacetylacetonato)europium(III) ([Eu(hfa)3(Me‐BIPYPO)]), were synthesized for lanthanide‐based sensor materials having high emission quantum yields and effective chemosensing properties. The emission quantum yields of [Eu(hfa)3(BIPYPO)] and [Eu(hfa)3(Me‐BIPYPO)] were 71 and 73%, respectively. Metal‐ion sensing properties of the EuIII complexes were also studied by measuring the emission spectra of EuIII complexes in the presence of ZnII or CuII ions. The metal‐ion sensing and the photophysical properties of luminescent EuIII complexes with a bidentate phosphine oxide containing 2,2′‐bipyridine framework are demonstrated for the first time.
Luminescent Nanoparticles of Silica‐Encapsulated Cadmium–Tellurium (CdTe) Quantum Dots with a Core–Shell Structure: Preparation and Characterization
Authors: Dong Haitao , Liu Yan , Ye Zhiqiang , Zhang Wenzhu , Wang Guilan , Liu Zhiguang , Yuan Jingli
Published: November 2009

Water‐soluble thioglycolic acid (TGA)‐capped CdTe quantum dots (QDs) were synthesized in aqueous medium, and then encapsulated in a silica nanosphere by copolymerization of the TGA‐capped CdTe conjugated with (3‐aminopropyl)triethoxysilane (APS‐CdTe conjugate), free (3‐aminopropyl)triethoxysilane (=3‐(triethoxysilyl)propan‐1‐amine; APS), and tetraethyl orthosilicate (TEOS) in a H2O‐in‐oil reverse microemulsion consisting of Triton X‐100, octanol, cyclohexane, and H2O in the presence of aqueous NH3 solution. The characterizations by transmission electron microscopy (TEM) and luminescence spectroscopy shows that the luminescent nanoparticles are monodisperse, spherical, and uniform in size, ca. 50 nm in diameter with a regular core–shell structure. In addition, primary amino groups directly introduced to the nanoparticle's surface by using free APS in the nanoparticle preparation enable the nanoparticles to be used easier as a biolabel. The effects of pH and metal cations on the luminescence of the nanoparticles also suggest that the new nanoparticles could be useful probes for luminescent sensings of pH and Cu2+ ion.
Water Stability and Luminescence of Lanthanide Complexes of Tripodal Ligands Derived from 1,4,7‐Triazacyclononane: Pyridinecarboxamide versus Pyridinecarboxylate Donors
Authors: Nocton Grégory , Nonat Aline , Gateau Christelle , Mazzanti Marinella
Published: November 2009

A series of europium(III) and terbium(III) complexes of three 1,4,7‐triazacyclononane‐based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6′,6″‐[1,4,7‐triazacyclononane‐1,4,7‐triyltris(methylene)]tris[pyridine‐2‐carboxylic acid] (H3tpatcn), ‐tris[pyridine‐2‐carboxamide] (tpatcnam), and ‐tris[pyridine‐2‐carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50‐fold decrease for the carboxamide derivative in comparison to the picolinic acid (=pyridine‐2‐carboxylic acid) based ligand. Detailed analysis of the radiative rate constants and the energy of the triplet states for the three ligand systems revealed a less efficient energy transfer for the carboxamide‐based systems. The stability of the three ligand systems in H2O was investigated. Although hydrolysis of the ethyl ester occurred in H2O for the [Ln(tpatcnes)](OTf)3 complexes, the tripositive [Ln(tpatcnam)](OTf)3 complexes and the neutral [Ln(tpatcn)] complexes showed high stability in H2O which makes them suitable for application in biological media. The [Tb(tpatcn)] complex formed easily in H2O and was thermodynamically stable at physiological pH (pTb 14.9), whereas the [Ln(tpatcnam)](OTf)3 complexes showed a very high kinetic stability in H2O, and once prepared in organic solvents, remained undissociated in H2O.
Effects of Zinc(II) on the Luminescence of Europium(III) in Complexes Containing β‐Diketone and Schiff Bases
Authors: Hasegawa Yuko , Saitou Shuhei , Tamaki Sayaka , Yajima Hirofumi , Tadokoro Makoto
Published: November 2009

The UV, excitation, and luminescence spectra of tris(pivaloyltrifluoroacetonato)europium(III) ([Eu(pta)3]; Hpta=1,1,1‐trifluoro‐5,5‐dimethylhexane‐2,4‐dione=HA) were measured in the presence of bis(salicylidene)trimethylenediamine (H2saltn), bis[5‐(tert‐butyl)salicylidene]trimethylenediamine (H2(tBu)saltn), or bis(salicylidene)cyclohexane‐1,2‐diyldiamine (H2salchn), and the corresponding ZnII complexes [ZnB] (B=Schiff base). The excitation and luminescence spectra of the solution containing [Eu(pta)3] and [Zn(salchn)] exhibited much stronger intensities than those of solutions containing the other [ZnB] complexes. The introduction of a tBu group into the Schiff base was not effective in sensitizing the luminescence of [Eu(pta)3]. The luminescence spectrum of [ZnB] showed a band around 450 nm. The intensity decreased in the presence of [Eu(pta)3], reflecting complexation between [Eu(pta)3] and [ZnB]. On the basis of the change in intensity against the concentration of [ZnB], stability constants were determined for [Eu(pta)3Zn(saltn)], [Eu(pta)3Zn{(tBu)saltn}], and [Eu(pta)3Zn(salchn)] as 4.13, 4.9 and 5.56, respectively (log $\rm{\overline \beta }$, where $\rm{\overline \beta }$=[[Eu(pta)3ZnB]]([[Eu(pta)3]][[ZnB]])−1). The quantum yields of these binuclear complexes were determined as 0.15, 0.11, and 0.035, although [Eu(pta)3Zn(salchn)] revealed the strongest luminescence at 613 nm. The results of X‐ray diffraction analysis for [Eu(pta)3Zn(saltn)] showed that ZnII had a coordination number of five and was bridged with EuIII by three donor O‐atoms, i.e., two from the salicylidene moieties and one from the ketonato group pta.
Luminescent Soft Material: Two New Europium‐Based Ionic Liquids
Authors: Tang Sifu , Cybinska Joanna , Mudring Anja‐Verena
Published: November 2009

Two new Eu‐based ionic liquid systems, [C4mim][DTSA] : [Eu(DTSA)3] and 2[C4mim] [DTSA] : [Eu(DTSA)3] were synthesized at 120° under inert conditions from 1‐butyl‐1‐methylimidazolium ditoluenesulfonylamide ([C4mim][DTSA]). The identity and purity of the synthesized compounds were confirmed by elemental analysis, IR, Raman, and 1H‐NMR spectroscopy. As they solidify below 100° as glasses they qualify as ionic liquids. Fluorescence measurements show that the materials exhibit a strong red luminescence of high color purity. Therefore, they have the potential to be used for optical applications such as in emission displays.
Minocycline‐Based Europium(III) Chelate Complexes: Synthesis, Luminescent Properties, and Labeling to Streptavidin
Authors: Nishioka Takuya , Yamamoto Yuji , Hashino Kimikazu , Matsumoto Kazuko
Published: November 2009

Two chelate ligands for europium(III) having minocycline (=(4S,4aS,5aR,12aS)‐4,7‐bis(dimethylamino)‐1,4,4a,5,5a,6,11,12a‐octahydro‐3,10,12,12a‐tetrahydroxy‐1,11‐dioxonaphthacene‐2‐carboxamide; 5) as a VIS‐light‐absorbing group were synthesized as possible VIS‐light‐excitable stable Eu3+ complexes for protein labeling. The 9‐amino derivative 7 of minocycline was treated with H6TTHA (=triethylenetetraminehexaacetic acid=3,6,9,12‐tetrakis(carboxymethyl)‐3,6,9,12‐tetraazatetradecanedioic acid) or H5DTPA (=diethylenetriaminepentaacetic acid=N,N‐bis{2‐[bis(carboxymethyl)amino]ethyl}glycine) to link the polycarboxylic acids to minocycline. One of the Eu3+ chelates, [Eu3+(minocycline‐TTHA)] (13), is moderately luminescent in H2O by excitation at 395 nm, whereas [Eu3+(minocycline‐DTPA)] (9) was not luminescent by excitation at the same wavelength. The luminescence and the excitation spectra of [Eu3+(minocycline‐TTHA)] (13) showed that, different from other luminescent EuIII chelate complexes, the emission at 615 nm is caused via direct excitation of the Eu3+ ion, and the chelate ligand is not involved in the excitation of Eu3+. However, the ligand seems to act for the prevention of quenching of the Eu3+ emission by H2O. The fact that the excitation spectrum of [Eu3+(minocycline‐TTHA)] is almost identical with the absorption spectrum of Eu3+ aqua ion supports such an excitation mechanism. The high stability of the complexes of [Eu3+(minocycline‐DTPA)] (9) and [Eu3+(minocycline‐TTHA)] (13) was confirmed by UV‐absorption semi‐quantitative titrations of H4(minocycline‐DTPA) (8) and H5(minocycline‐TTHA) (12) with Eu3+. The titrations suggested also that an 1 : 1 ligand Eu3+ complex is formed from 12, whereas an 1 : 2 complex was formed from 8 minocycline‐DTPA. The H5(minocycline‐TTHA) (12) was successfully conjugated to streptavidin (SA) (Scheme 5), and thus the applicability of the corresponding Eu3+ complex to label a protein was established.
Synthesis and Relaxometric Properties of Gadolinium(III) Complexes of New Triazine‐Based Polydentate Ligands
Authors: Tei Lorenzo , Benzi Marina , Kielar Filip , Botta Mauro , Cavallotti Camilla , Giovenzana Giovanni Battista , Aime Silvio
Published: November 2009

Two new derivatives based on an s‐triazine structural motif were synthesized by attaching two 2,2′‐hydrazinylidenebis[acetic acid] moieties to the triazine ring to reach an overall heptadenticity for the complexation of lanthanide(III) cations. The remaining reactive site was exploited for the substitution with a functionizable amino group (see H4L1) and a lipophilic moiety (see H4L2). Luminescence‐lifetime determinations revealed the presence of a single H2O molecule coordinated for [Eu(L1)]. A complete 1H‐NMR relaxometric study was carried out for the octacoordinated [Gd(L1)] and [Gd(L2)] complexes. A remarkably long H2O residence lifetime (298τM=5.2 μs) was found by 17O‐NMR in the case of [Gd(L1)]. Micelle formation of the lipophilic complex [Gd(L2)] was evidenced, the critical micellization concentration (cmc) determined, and relaxometric properties of the system investigated.
Homo‐ and Heterovalent Polynuclear Cerium and Cerium/Manganese Aggregates
Authors: Mereacre Valeriu , Ako Ayuk M. , Akhtar Muhammad Nadeem , Lindemann Anja , Anson Christopher E. , Powell Annie K.
Published: November 2009

Reactions of CeIII(NO3)3⋅6 H2O or (NH4)2[CeIV(NO3)6] with Mn‐containing starting materials result in seven novel polynuclear Ce or Ce/Mn complexes with pivalato (tBuCO$\rm{{_{2}^{-}}}$) and, in most cases, auxiliary N,O‐ or N,O,O‐donor ligands. With nuclearities ranging from 6–14, the compounds present aesthetically pleasing structures. Complexes [CeIV6(μ3‐O)4(μ3‐OH)4(μ‐O2CtBu)12] (1), [CeIV6MnIII4(μ4‐O)4(μ3‐O)4(O2CtBu)12(ea)4(OAc)4]⋅4 H2O⋅4 MeCN (ea−=2‐aminoethanolato; 2), [CeIV6MnIII8(μ4‐O)4(μ3‐O)8(pye)4(O2CtBu)18]2[CeIV6(μ3‐O)4(μ3‐OH)4(O2CtBu)10(NO3)4] [CeIII(NO3)5(H2O)]⋅21 MeCN (pye−=pyridine‐2‐ethanolato; 3), and [CeIV6CeIII2MnIII2(μ4‐O)4(μ3‐O)4(tbdea)2(O2CtBu)12(NO3)2(OAc)2]⋅4 CH2Cl2 (tbdea2−=2,2′‐(tert‐butylimino]bis[ethanolato]; 4) all contain structures based on an octahedral {CeIV6(μ3‐O)8} core, in which many of the O‐atoms are either protonated to give (μ3‐OH)− hydroxo ligands or coordinate to further metal centers (MnIII or CeIII) to give interstitial (μ4‐O)2− oxo bridges. The decanuclear complex [CeIV8CeIIIMnIII(μ4‐O)3(μ3‐O)3(μ3‐OH)2(μ‐OH)(bdea)4(O2CtBu)9.5(NO3)3.5(OAc)2]⋅1.5 MeCN (bdea2−=2,2′‐(butylimino]bis[ethanolato]; 5) contains a rather compact CeIV7 core with the CeIII and MnIII centers well‐separated from each other on the periphery. The aggregate in [CeIV4MnIV2(μ3‐O)4(bdea)2(O2CtBu)10(NO3)2]⋅4 MeCN (6) is based on a quasi‐planar {MnIV2CeIV4(μ3‐O)4} core made up of four edge‐sharing {MnIVCeIV2(μ3‐O)} or {CeIV3(μ3‐O)} triangles. The structure of [CeIV3MnIV4MnIII(μ4‐O)2(μ3‐O)7(O2CtBu)12(NO3)(furan)]⋅6 H2O (7⋅6 H2O) can be considered as {MnIV2CeIV2O4} and distorted {MnIV2MnIIICeIVO4} cubane units linked through a central (μ4‐O) bridge. The Ce6Mn8 equals the highest nuclearity yet reported for a heterometallic Ce/Mn aggregate. In contrast to most of the previously reported heterometallic Ce/Mn systems, which contain only CeIV and either MnIV or MnIII, some of the aggregates presented here show mixed valency, either MnIV/MnIII (see 7) or CeIV/CeIII (see 4 and 5). Interestingly, some of the compounds, including the heterovalent CeIV/CeIII 4, could be obtained from either CeIII(NO3)3⋅6 H2O or (NH4)2[CeIV(NO3)6] as starting material.
Optimized reservoir operation to balance human and riverine ecosystem needs: model development, and a case study for the Tanghe reservoir, Tang river basin, China
Authors: Yin Xinan , Yang Zhifeng , Yang Wei , Zhao Yanwei , Chen He
Published: November 2009

Reservoirs impose many negative impacts on riverine ecosystems. To balance human and ecosystem needs, we propose a reservoir operation method that combines reservoir operating rule curves with the regulated minimum water release policy to meet the environmental flow requirements of riverine ecosystems. Based on the relative positions of the reservoir and the water intakes, we consider three scenarios: water used for human needs (including industrial, domestic and agricultural) is directly withdrawn from (1) the reservoir; (2) both reservoirs and downstream river channels and (3) downstream river. The proposed method offers two advantages over traditional methods: First, it can be applied to finding the optimal reservoir operating rule curves with the consideration of environmental flow requirement, which is beneficial to the sustainable water uses. Second, it avoids a problem with traditional approaches, which prescribe the minimum environmental flow requirements as the regulated minimum environmental flow releases from reservoirs, implicitly giving lower priority to the riverine ecosystem. Our method instead determines the optimal regulated minimum releases of water to sustain environmental flows while more effectively balancing human and ecosystem needs. To demonstrate practical use of the model, we present a case study for operation of the Tanghe reservoir in China's Tang river basin for the three above‐mentioned scenarios. The results demonstrate that this approach will help the reservoir's managers satisfy both human and environmental requirements. Copyright © 2009 John Wiley & Sons, Ltd.
Lithological controls on biological activity and groundwater chemistry in Quaternary sediments
Authors: Bartlett Rebecca , Bottrell Simon H. , Sinclair Karen , Thornton Steve , Fielding Ian D. , Hatfield Dave
Published: November 2009

Depth profiles of solute chemistry and sulfate isotopic compositions are presented for groundwater and pore water in a sequence of Quaternary glacial outwash sediments. Sand units show evidence for hydraulic connection to the surface and thus modern sources of solutes. Finer‐grained sediments show a general pattern of increasing solute concentrations with depth, with sulfate derived from ancient rainwater and pyrite oxidation in the soil/drift. In these sediments sulfate has undergone bacterial sulfate reduction (BSR) to produce biogenic sulfide. In clay sediments, with d10 ≤ 1·6 µm, high concentrations of sulfate and acetate now co‐exist, implying that BSR is inhibited. The correlation with smaller sediment grain size indicates that this is due to pore size exclusion of the sulfate reducing bacteria. Mechanical restriction of microbial function thus provides a fundamental limitation on microbial respiration in buried clay‐rich sediments, which acts as a control on the chemical evolution of their pore waters. Copyright © 2009 John Wiley & Sons, Ltd.