bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Short‐term and Long‐term Aluminium Stress on Photosynthesis, Respiration, and Reproductive Capacity in a Unicellular Green Flagellate (Euglena gracilis)
Authors: Danilov Roman A. , Ekelund Nils G. A. 
Published: January 2003

AbstractEffects of short‐term (1 h exposure) and long‐term (7 d exposure) aluminium stress on photosynthesis and reproductive capacity have been studied in Euglena gracilis strain Z. Following concentrations of Altot (added as AlCl3) were tested: 0.5 mg L‐1, 1.0 mg L‐1, 1.5 mg L‐1, 2.5 mg L‐1, 5.0 mg L‐1, 7.5 mg L‐1, 10.0 mg L‐1, and 15.0 mg L‐1 Al, respectively. Growth rates at different aluminium concentrations did not show significant differences, except at 15.0 mg L‐1Al. Initial respiration was higher in long‐term than in the short‐term experiments. It is supposed that an energy‐dependent mechanism of excretion of aluminium ions has been active in the stressed cells. Consequently, the cells of E. gracilis after long‐term exposure to aluminium are believed to be more acclimatised to the aluminium stress. Photosynthetic efficiency (PE) has been negatively affected by aluminium in all experiments performed. Differences between control algae and those treated with aluminium were significant in all cases. PE in long‐term experiments was in general significantly higher at all concentrations of aluminium studied, compared to the short‐term experiments. The aluminium concentrations tested led only to a general decrease in PE while the level of decrease was not especially concentration‐dependent. In general, aluminium tolerance of E. gracilis can be estimated as low, especially by short‐term exposure. However, good acclimatisation capacity of this green flagellate to aluminium doses by long‐term exposure can be supposed.
Scum in Nutrient Removal Plants: The Role of Carbon Sources in “Microthrix parvicella” Growth
Authors: Lemmer Hilde , Müller Elisabeth , Schade Margit 
Published: January 2003

AbstractScum formation is a widespread problem in activated sludge nutrient removal plants. It often comes along with an excessive development of the filamentous bacterium “Microthrix parvicella” stabilizing the flotation process. As “M. parvicella” was found to depend on long‐chain fatty acids (LCFA) as sole carbon source not only in vitro but also in situ, some options of in‐situ substrate supply are discussed. Wastewater concentrations of fatty acids in the range of 2 to 15 mg L‐1 and homologue concentrations from synthetic surfactant degradation below 10 mg L‐1 rule out these substrates as source for excessive biomass production. They might, however, well be suitable for start‐up of a “M. parvicella” population. Build‐up of excessive biomass might rely on fatty acid supply originating in cell walls of lysed stationary phase bacteria of long residence time sludge fractions such as scum layers. Moreover, biogenic surfactants such as rhamnolipids have been proved to be an excellent carbon source for excessive biomass production in vitro.
The Delocalization Index as an Electronic Aromaticity Criterion: Application to a Series of Planar Polycyclic Aromatic Hydrocarbons
Authors: Poater Jordi , Fradera Xavier , Duran Miquel , Solà Miquel 
Published: January 2003

AbstractThis work introduces a new local aromaticity measure, defined as the mean of Bader's electron delocalization index (DI) ofpara‐related carbon atoms in six‐membered rings. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized distribution of π‐electrons. We have found that this DI and the harmonic oscillator model of aromaticity (HOMA) index are strongly correlated for a series of six‐membered rings in eleven planar polycyclic aromatic hydrocarbons. The correlation between the DI and the nucleus‐independent chemical shift (NICS) values is less remarkable, although in general six‐membered rings with larger DI values also have more negative NICS indices. We have shown that this index can also be applied, with some modifications, to study of the aromaticity in five‐membered rings.
3,3′‐ and 4,4′‐Dimethoxy‐2,2′‐bipyrroles: Highly Electron‐Rich Model Compounds for Polypyrrole Formation.
Authors: Merz Andreas , Anikin Sergiy , Lieser Bernd , Heinze Jürgen , John Hermann 
Published: January 2003

Abstract3,3′‐Dimethoxy‐2,2′‐bipyrrole (1) and 4,4′‐dimethoxy‐2,2′‐bipyrrole (2) were obtained in short sequences and good yields fromN‐benzyl‐3‐hydroxypyrrole‐2,4‐dicarboxylic acid. The key intermediate leading to1is anN‐benzyl‐3‐methoxypyrrole, which is dimerized by lithiation and oxidation with NiCl2. The formation of2is achieved by a classical Ullmann coupling of diethyl 1‐benzyl‐2‐bromo‐4‐methoxypyrrole‐3,5‐dicarboxylate. TheN‐benzyl protection groups of1and2are cleaved under reducing conditions with sodium in liquid ammonia. Both isomeric bipyrroles are extremely sensitive toward air. Compound1has a very low oxidation potential of 0.09 V against AgCl but film formation hardly occurs. On the other hand, compound2with a potential of 0.35 V readily forms stable polypyrrole films with anodic waves at −0.51 and −0.35 V and a cathodic wave at −0.77 V, the lowest potential ever observed for a p‐doped polymer.
Theoretical and Photoluminescence Studies on the d10–s2 AuI–TlI Interaction in Extended Unsupported Chains
Authors: Fernández Eduardo J. , Laguna Antonio , López‐de‐Luzuriaga José M. , Mendizabal Fernando , Monge Miguel , Olmos M. Elena , Pérez Javier 
Published: January 2003

AbstractThe reactions of solutions of TlPF6 and OPPh3 in tetrahydrofuran or acetone with NBu4[AuR2] (R=C6Cl5, C6F5) gave the new complexes [Au(C6Cl5)2]2[Tl(OPPh3)][Tl(OPPh3)(L)] (L=THF (1), acetone (2)) and the previously reported [Tl(OPPh3)2][Au(C6F5)2] (3). The crystal structures of complexes 1 and 2 display extended unsupported chains with short intermolecular interactions between alternating gold(I) and thallium(I) centres. Moreover, the TlI centres show two different types of geometrical environments, such as pseudotetrahedral and distorted trigonal‐bipyramidal, due to the presence of solvent molecules that act as ligands in the solid‐state structure. Quasirelativistic and nonrelativistic ab initio calculations were performed to study the nature of the intermetallic AuI–TlI interactions and are consistent with the presence of a high ionic contribution (80 %) and dispersion‐type (van der Waals) interaction with a charge‐transfer contribution (20 %) when relativistic effects are taken into account. All complexes are luminescent in the solid state at room temperature and at 77 K. Complexes 1 and 2 show site‐selective excitation, probably due to the different environments around the TlI centres. The DFT and time‐dependent (TD)‐DFT calculations are in agreement with the experimental excitation spectra for all complexes and confirm the site‐selective excitation behaviour as a function of the TlI geometrical environment.
Synthesis, Photophysical and Electrochemical Properties, and Biological Labeling Studies of Cyclometalated Iridium(III) Bis(pyridylbenzaldehyde) Complexes: Novel Luminescent Cross‐Linkers for Biomolecules
Authors: Lo Kenneth Kam‐Wing , Chung Chi‐Keung , Zhu Nianyong 
Published: January 2003

AbstractWe report the synthesis, characterization, photophysical, and electrochemical properties of a series of luminescent cyclometalated iridium(III) complexes containing two aldehyde functional groups [Ir(pba)2(N–N)](PF6) (Hpba=4‐(2‐pyridyl)benzaldehyde; N–N=2,2′‐bipyridine, bpy (1), 1,10‐phenanthroline, phen (2), 3,4,7,8‐tetramethyl‐1,10‐phenanthroline, 3,4,7,8‐Me4‐phen (3), 4,7‐diphenyl‐1,10‐phenanthroline, 4,7‐Ph2‐phen (4)). The X‐ray crystal structure of complex 1 has been investigated. Upon photoexcitation, complexes 1–4 exhibit intense and long‐lived emission in fluid solutions at 298 K and in low‐temperature glass. The luminescence is assigned to a triplet intra‐ligand (3IL) excited state associated with the pba− ligand, probably with mixing of some triplet metal‐to‐ligand charge‐transfer (3MLCT) (dπ(Ir)→π*(pba−)) character. Since each of these complexes possesses two aldehyde groups, which can react with the primary amine groups of biomolecules to form stable secondary amines after reductive amination, we have investigated the possibility of these complexes as novel luminescent cross‐linkers for biological substrates. L‐Alanine has been labeled with complexes 1–4 to give the luminescent bioconjugates 1‐(Ala)2–4‐(Ala)2. These conjugates show strong photoluminescence with long emission lifetimes under ambient conditions. On the basis of the emission energy trend, the excited state of these luminescent bioconjugates is likely to bear a high parentage of 3MLCT (dπ(Ir)→π*(N–N)) character. In addition, the glycoprotein avidin (Av) has also been conjugated with complexes 1–4 to give the bioconjugates 1‐Av–4‐Av. Upon photoexcitation, these bioconjugates also display intense and long‐lived 3MLCT (dπ(Ir)→π*(N–N)) emission in aqueous buffer at 298 K. Furthermore, a heterogeneous competitive assay for biotin has been developed using 2‐Av and biotinylated microspheres. We have shown that complexes 1–4 represent a new class of multicolor luminescent cross‐linkers for biomolecular species.
Substituent Effects on OH Bond Dissociation Enthalpies and Ionization Potentials of Catechols: A DFT Study and Its Implications in the Rational Design of Phenolic Antioxidants and Elucidation of Structure–Activity Relationships for Flavonoid Antioxidants
Authors: Zhang Hong‐Yu , Sun You‐Min , Wang Xiu‐Li 
Published: January 2003

AbstractDensity functional theory (DFT) on B3LYP/6‐31G(d,p) level was employed to investigate the substituent effects on OH bond dissociation enthalpies (BDEs) and ionization potentials (IPs) of catechols. It was revealed that the ortho hydroxyl of catechol was effective for the reduction of the OH BDE; however, the group had little influence on the IP. The para substituent effects upon OH BDEs and IPs for catechols were roughly the same as those for monophenols, and this gave the catechol moiety more potential than monophenol to be used as a lead compound in rational design of phenolic antioxidants. In addition, the 1,4‐pyrone effects on OH BDEs of catecholic rings A or B of flavonoids were also investigated. Although 1,4‐pyrone extended the conjugation system of flavonoids, it was not beneficial to reduce the OH BDE as a result of its electron‐withdrawing property. Thus, 1,4‐pyrone was unlikely to be favorable to enhance the H‐abstraction activity of flavonoids.
Synthesis and Structural Analysis of the Polymetallated Alkali Calixarenes [M4(p‐tert‐butylcalix[4]arene‐4H)(thf)x]2⋅n THF (M=Li, K; n=6 or 1; x=4 or 5) and [Li2(p‐tert‐butylcalix[4]arene‐2H)(H2O)(μ‐H2O)(thf)]⋅3 THF
Authors: Gueneau Estelle D. , Fromm Katharina M. , Goesmann H. 
Published: January 2003

AbstractTo study the structures and reactivities of alkali metallated intermediates of calix[4]arenes, three compounds were isolated: [Li4(p‐tert‐butylcalix[4]arene‐4H)(thf)4]2⋅6 THF (1), [Li2(p‐tert‐butylcalix[4]arene‐2H)(H2O)(μ‐H2O)(thf)]⋅3 THF (2), and [K4(p‐tert‐butylcalix[4]arene‐4H)(thf)5]2⋅THF (3). The structure of 1 is shown to be dependent on the coordinating solvent. Partial hydrolysis of 1 leads to the formation of 2. The potassium compound 3 features a different structure to that of 1, due to a higher coordination number as well as stronger cation–π‐bonding interactions.
Reagent‐Controlled Stereoselectivity in Titanocene‐Catalyzed Epoxide Openings: Reductions and Intermolecular Additions to α,β‐Unsaturated Carbonyl Compounds
Authors: Gansäuer Andreas , Bluhm Harald , Rinker Björn , Narayan Sanjay , Schick Michael , Lauterbach Thorsten , Pierobon Marianna 
Published: January 2003

AbstractThe generation and addition reactions of metal bound radicals derived from normal and meso epoxides by electron transfer from titanocene(III) reagents is described. The control of enantioselectivity and diastereoselectivity of these transformations is investigated by variation of the ligands of the metal complex. The reaction can lead to unprecedented and highly selective reactions, in which synthetically useful alcohols may be prepared. The synthesis presented also circumvents the use of toxic metals. Another advantage is that there is no loss of two functional groups as usually observed in reductive radical chain reactions.
Dynamic Chirality: Keen Selection in the Face of Stereochemical Diversity in Mechanically Bonded Compounds
Authors: Tseng Hsian‐Rong , Vignon Scott A. , Celestre Paul C. , Stoddart J. Fraser , White Andrew J. P. , Williams David J. 
Published: January 2003

AbstractThe template‐directed syntheses, employing bisparaphenylene‐[34]crown‐10 (BPP34C10), 1,5‐dinaphthoparaphenylene‐[36]crown‐10 (1/5NPPP36C10), and 1,5‐dinaphtho‐[38]crown‐10 (1/5DNP38C10) as templates, of three [2]catenanes, whereby one of the two bipyridinium units in cyclobis(paraquat‐p‐phenylene) is replaced by a bipicolinium unit, are described. The crude reaction mixtures comprising the [2]catenanes all contain slightly more of the homologous [3]catenanes, wherein a “dimeric” octacationic cyclophane has the crown ether macrocycles encircling the alternating bipyridinium units with the bipicolinium units completely unfettered. X‐ray crystallography, performed on all three [2]catenanes and two of the three [3]catenanes reveals co‐conformational and stereochemical preferences that are stark and pronounced. Both the [3]catenanes crystallize as mixtures of diastereoisomers on account of the axial chirality associated with the picolinium units in the solid state. Dynamic 1H NMR spectroscopy is employed to probe in solution the relative energy barriers for rotations by the phenylene and pyridinium rings in the tetracationic cyclophane component of the [2]catenanes. Where there are co‐conformational changes that are stereochemically “allowed”, crown ether circumrotation and rocking processes are also investigated for the relative rates of their occurrence. The outcome is one whereby the three [2]catenanes containing BPP34C10, 1/5NPPP36C10, and 1/5DNP38C10 exist as one major enantiomeric pair of diastereoisomers amongst two, four, and eight diastereoisomeric pairs of enantiomers, respectively. The diastereoisomerism is a consequence of the presence of axial chirality together with helical and/or planar chirality in the same interlocked molecule. These [2]catenanes constitute a rich reserve of new stereochemical types that might be tapped for their switching and mechanical properties.
Expression of PTPRO during mouse development suggests involvement in axonogenesis and differentiation of NT‐3 and NGF‐dependent neurons
Authors: Beltran Pedro J. , Bixby John L. , Masters Brian A. 
Published: January 2003

AbstractCompetition and cooperation between type II and type III receptor protein tyrosine phosphatases (RPTPs) regulate axon extension and pathfinding in Drosophila. The first step to investigate whether RPTPs influence axon growth in the more complex vertebrate nervous system is to identify which neurons express a particular RPTP. We studied the expression of mouse PTPRO, a type III RPTP with an extracellular region containing eight fibronectin type III domains, during embryogenesis and after birth. Mouse PTPRO mRNA is expressed exclusively in two cell types: neurons and kidney podocytes. Maximal expression in the brain was coincident with mid to late gestation and axonogenesis in the brain. We cloned two cDNAs, including a splice variant without sequence coding of 28 amino acids within the juxtamembrane domain that was found mostly in kidney. In situ hybridization detected mPTPRO mRNA in the cerebral cortex, olfactory bulb and nucleus, hippocampus, motor neurons, and the spinal cord midline. In addition, mPTPRO mRNA was found throughout dorsal root, cranial, and sympathetic ganglia and within kidney glomeruli. Mouse PTPRO mRNA was observed in neuron populations expressing TrkA, the high‐affinity nerve growth factor receptor, or TrkC, the neurotrophin‐3 receptor, and immunoreactive mPTPRO and TrkC colocalized in large dorsal root ganglia proprioceptive neurons. Our results suggest that mPTPRO is involved in the differentiation and axonogenesis of central and peripheral nervous system neurons, where it is in a position to modulate intracellular responses to neurotrophin‐3 and/or nerve growth factor. J. Comp. Neurol. 456:384–395, 2003. © 2003 Wiley‐Liss, Inc.
Tenascin‐R–deficient mice show structural alterations of symmetric perisomatic synapses in the CA1 region of the hippocampus
Authors: Nikonenko Alexander , Schmidt Sandra , Skibo Galina , Brückner Gert , Schachner Melitta 
Published: January 2003

AbstractAccumulating evidence suggests that extracellular matrix (ECM) molecules play important roles in formation of synapses. Our previous electrophysiologic study of mice deficient in the extracellular matrix glycoprotein tenascin‐R (TN‐R) showed an impaired γ‐aminobutyric acid release at perisomatic inhibitory synapses in the CA1 pyramidal cell layer of the hippocampus. The present study investigated possible ultrastructural correlates of abnormal perisomatic inhibition. Topographic, morphometric, and stereologic methods were applied at the light and electron microscopic levels to quantify the density and spatial arrangement of cell bodies of CA1 pyramidal neurons and density and architecture of symmetric synapses formed on them in TN‐R−/− and wild‐type mice of different ages. The spatial arrangement of neuronal cell bodies in the CA1 pyramidal cell layer was found more diffuse and disordered in TN‐R−/− mice than in wild‐type animals. The coverage of the plasma membrane of pyramidal cell bodies by active zones of symmetric synapses was reduced by at least 40% in TN‐R−/− animals compared with control animals. Further, the length of active zone profiles of perisomatic inhibitory synapses in the CA1 pyramidal cell layer was 8–14% smaller, whereas the number of active zones calculated per length unit of cell body profile was 30–40% smaller in TN‐R mutants than in wild‐type animals. The density and spatial arrangement of synaptic vesicles in the synaptic terminals provided ultrastructural evidence for reduced synaptic activity in TN‐R mutants. Thus, TN‐R appears to play an important role in the regulation of the number and architecture of perisomatic inhibitory synapses, which play crucial roles in the synchronization of neuronal activity and modulation of synaptic plasticity in the hippocampus. J. Comp. Neurol. 456:338–349, 2003. © 2003 Wiley‐Liss, Inc.
Quantifying subjective assessment of sleep and life‐quality in antidepressant‐treated depressed patients
Authors: Mayers Andrew G. , van Hooff Johanna C. , Baldwin David S. 
Published: January 2003

AbstractThis study sought to establish a method of quantifying subjective perceptions of sleep against perceptions of life‐quality and mood, using amended versions of the Pittsburgh sleep diary (PghSD) and quality of life of insomniacs (QOLI) questionnaire. Diaries and questionnaires were self‐completed in participants' homes. Outpatients with a DSM‐IV diagnosis of major depressive disorder were compared with a healthy control group (with no history, or family history, of depression). Poorer sleepers, as determined by the sleep diary, were significantly more likely to report poorer life‐quality and mood perceptions on the subsequent questionnaire. Furthermore, the depressed group reported significantly poorer perceptions of sleep quality and poorer perceptions of life‐quality and mood than the control group, even though estimates of sleep disturbance were similar. This may indicate that depressed individuals experience more ‘sleep distress’ than healthy individuals. These results confirm the extent of subjectively reported sleep disruption in depression and demonstrate the merit of combining the amended PghSD and QOLI to quantify sleep perceptions. Copyright © 2002 John Wiley & Sons, Ltd. Copyright © 2002 John Wiley & Sons, Ltd.
Subjective assessment of the effects of CNS‐active drugs on sleep by the Leeds sleep evaluation questionnaire: a review
Authors: Zisapel N. , Laudon M. 
Published: January 2003

AbstractThe Leeds sleep evaluation questionnaire (LSEQ) comprises ten self‐rating 100 mm line analogue questions concerned with sleep and early morning behaviour. A literature search identified 83 studies in peer‐reviewed journals that reported the use of the LSEQ for psychopharmacological investigations of drug effects on self‐reported aspects of sleep. High internal consistency and reliability of the questionnaire have been demonstrated. Findings from studies involving a variety of psychoactive agents indicated that the LSEQ was able to quantify subjective impressions of sleep and waking and the effects of drugs in healthy volunteers, depressed and insomnia patients.In accordance with their known activity profile nocturnal administration of sedative hypnotic agents and antihistamines induced dose‐related improvements in self‐reported ease of getting to sleep, and quality of sleep but a decrease in alertness and behavioural integrity the following morning. Psychostimulants, on the other hand, impaired subjective ratings of sleep and increased early morning alertness. Antidepressants and certain anxiolytic agents improved both self‐reported sleep aspects and early morning alertness. Treatment effects measured by the LSEQ corresponded to those measured for the same drugs by other assessment methods.These data indicate that the LSEQ is a robust and reliable instrument for psychopharmacological evaluations. Self‐evaluations of sleep, as obtained by the LSEQ, can therefore provide consistent and meaningful measures for estimating the effectiveness of sleep modulators and sedative‐hypnotic drugs. Copyright © 2003 John Wiley & Sons, Ltd.
8q24 Copy number gains and expression of the c‐myc mRNA stabilizing protein CRD‐BP in primary breast carcinomas
Authors: Ioannidis Panayotis , Mahaira Louisa , Papadopoulou Anna , Teixeira Manuel R. , Heim Sverre , Andersen Johan A. , Evangelou Evangelos , Dafni Urania , Pandis Nikos , Trangas Theoni 
Published: January 2003

AbstractThe coding region determinant binding protein (CRD‐BP) was isolated by virtue of its high affinity to the c‐myc mRNA coding region stability determinant and shown to shield this message from nucleolytic attack, prolonging its half‐life. CRD‐BP is normally expressed during fetal life but is also activated de novo in tumors. Considering that aberrant CRD‐BP expression may represent an additional mechanism interfering with c‐myc regulation, we screened 118 primary breast carcinomas for CRD‐BP expression, 60 of which had also been analyzed by comparative genomic hybridization (CGH). Copy number gains encompassing 8q24, the chromosome band that contains the c‐myc locus, were detected in 48.3% (29/60) of tumors, whereas gains involving band 17q21, which contains the CRD‐BP locus, were observed in 18.3% (11/60) of tumors. CRD‐BP expression was detected in 58.5% (69/118) of tumors, implying mechanisms of activation alternative to gene amplification. Altogether, some 75% of the tumors had alterations pertaining to c‐myc since they either harbored 8q24 gains and/or expressed CRD‐BP. Significant associations were detected between CRD‐BP expression and the absence of estrogen receptors (p = 0.005) and between the presence of 8q24 gains and an increased number of genomic changes as measured by CGH (p = 0.0017). Tumors were divided into 4 groups according to CRD‐BP expression and 8q24 gains. The odds for tumors having both characteristics to be classified as poorly differentiated (grade III vs. grade I and II) were 19.6 times the corresponding odds for tumors neither expressing CRD‐BP nor harboring 8q24 gains. For tumors either harboring 8q24 gains only or expressing CRD‐BP alone, the corresponding odds were 6.4 and 3, respectively. © 2002 Wiley‐Liss, Inc.