bluuebunny/crossref_metadata_2025 huggingface dataset:
Redox activity of tryptophan residues in recombinant cytochrome c peroxidase and its W51F and W191F mutants
Authors: Tsaprailis George , English Ann M.
Published: May 2006

Tryptophan oxidation mediated via the heme was initiated by adding 2, 6, and 20 equivalents of H2O2to 5 μM recombinant CCP (CCP(MI)) and its W51F and W19lF mutants at pH 7.0. Addition of the proteins to 8 M urea (pH 1.5) relieved heme quenching of Trp fluorescence. CCP(MI)-I, W51F-I, and W19lF-I, the two-electron oxidized species (Fe1V=O,R•+) formed on addition of 2 equivalents of H2O2, exhibited decreased fluorescence relative to the FeIIIforms. Loss of 0.7 Trp in CCP(MI)-I and W51F-I, and 0.2 Trp in W19lF-I implies that R•+is located on Trp19l in CCP(MI)-I and W51F-I Spontaneous decay of the Fe1V=O hemes back to FeIII, followed by reaction with 2 more equivalents of H2O2after 24 h, resulted in a combined loss of 2.7 (CCP(MI)), 1.5 (W51F), and ~1 (W19lF) Trp. Also, addition of 6 equivalents of H2O2to the resting FeIIIenzymes resulted in loss of ~2 Trps in CCP(MI) but only ~1 in W51F and W19lF, suggesting that Trp51 becomes redox active in CCP(MI) when > 2 equivalents of H2O2are reduced. Addition of 20 equivalents of H2O2resulted in a total loss of ~4,2.5, and 2 Trp in CCP(MI), W51F, and W19lF, respectively. Activity loss largely paralleled Trp loss, and the residual activity of CCP(MI) and W51F exposed to 20 equivalents of H2O2was 5–19%, while W19lF exhibited ~50% activity. SDS PAGE analysis revealed that oxidized CCP(MI) and W19lF were 60–70% monomeric, and W51F 27% monomeric following its reaction with > 2 equivalents H2O2. Amino acid analyses confirmed Trp loss and also showed significant Tyr, but not Met, loss in the oxidized proteins. Donors to the heme and pathways of electron migration are proposed based on the combined results. Key words: cytochrome c peroxidase, Trp mutants, H2O2oxidation, redox-active residues.
Tungsten and molybdenum oxo complexes of tetrakis(phenyldiazenyl)calix[4]arene substituted derivatives: EHMO calculations, spectroscopic characterization, and perturbations of the photophysical properties by neutral guest molecules
Authors: Harvey Pierre D. , Gagnon Jonathan , Provencher Réjean , Xu Bing , Swager Timothy M.
Published: May 2006

Bowl-shaped chromophores fabricated with tungsten and molybdenum oxo complexes of calix[4]arenes substituted at the para positions with phenyldiazenyl (R2C6H3N2) derivatives are investigated. The nature of the lowest energy excited states has been addressed theoretically using Extended Hückel Molecular Orbital (EHMO) calculations and experimentally using UV-visible, luminescence, and polarized emission spectroscopy at 77 K. The lowest energy excited states are intraligand (azobenzene fragment) ππ* (S2 and T2) and ππ*states (S1, and T1). The compounds are weakly luminescent in the 600–630 nm range exhibiting emissions arising from the 1(ππ*) states [Formula: see text]. The region located above 900 nm was not investigated. Evidence for guest–host chemistry has been demonstrated by1H-NMR spectroscopy, and the binding constants for two of the compounds with pyridine in toluene as a solvent were obtained by UV–visible spectroscopy. The presence of a guest molecule inside the luminescent metal oxo complex of a calix[4]arene hosts decreases the emission lifetimes.Key words: host–guest, photophysics, calix[4]arene, EHMO, fluorescence
Theoretical study of the PSi2 radical
Authors: Elorza Jose M. , Ugalde Jesus M.
Published: May 2006

G2 methodology has been used to characterize minima on both doublet and quartet potential energy surfaces of the PSi2 radical system. We found that for states with doublet spin multiplicity the most stable isomer is the cyclic 2A1. Linear isomers lie more than 24 kcal/mol above in energy. For the quartets the most stable state isomer is the cyclic 4A2, and the most stable linear isomer, i.e., Si-Si-P(4∑−), lies 10.68 kcal/mol higher in energy. The structural features of the various isomers characterized have been rationalized in terms of the bonding features of the molecular orbitals involved. Key words: ab initio, excited states, radical.
Photodecarbonylation of chiral cyclobutanones
Authors: Ramnauth Jailall , Lee-Ruff Edward
Published: May 2006

Triplet photosensitized irradiation of 2(S),3(R)-bis[(benzoyloxy)methyl]cyclobutanone gave optically pure (−)E-1(S),2(S)-bis(benzoyloxymethyl)cyclopropane as a major product in the nonpolar fraction along with its stereoisomer and cycloelimination products. The absolute stereochemistry of the chiral cyclopropane was established by independent synthesis and X-ray crystal structure determination of a synthetic precursor. The distribution of decarbonylation and cycloelimination products was inversely dependent on the concentration of the substrate. Irradiation of the same ketone in tetrahydrofuran or benzene gave mostly cycloelimination products. Addition of Michler's ketone increased the ratio of photodecarbonylation, suggesting a triplet state pathway for this process. This was corroborated by the addition of dicyanoethylene, which showed significant quenching of photodecarbonylation. Irradiation of 2(S)-[(benzoyloxy)methyl]cyclobutane in acetone gave the corresponding cyclopropane as the principal product. Keywords: photodecarbonylation, chiral cyclopropanes, cyclobutanones, triplet sensitization.
Metal hydride mediated reduction of 3-(alkylthio)oxindoles containing other potentially reducible groups
Authors: Connolly Terrence J. , Durst Tony
Published: May 2006

The reduction of several 3-(methylthio)oxindoles bearing ester groups on the benzene ring has been studied. The reaction is very dependent on the substitution of the oxindole, and the position of the ester group. Deprotonation of the C3 center by the metal hydride is the major initial pathway. This deprotonation plays a role in the reduction of the pendant ester group. Ester groups ortho, and presumably para, to C3 are very difficult to reduce, reaction only occurring with excess LiAlH4 at elevated temperatures. Once reduction starts, it is very difficult to stop, with reduction of the ester to a methyl group being observed. When deprotonation at this center is blocked, ester reduction becomes straightforward and can be accomplished at room temperature with LiEt3BH. Keywords: oxindole, reduction, anion.
Design of ligands for the complexation of Fe(II)/Fe(III) in the catalytic oxidation of H2S to sulfur
Authors: Hancock Robert D. , Martell Arthur E. , Chen Dian , Motekaitis Ramunas J. , McManus Derek
Published: May 2006

Examination of the stability constants of Fe(II) and Fe(III) chelates of a wide variety of ligands that contain only acetate and amino groups shows a linear correlation. A separate linear correlation displaced toward the ferric ion was obtained for those ligands that contain more basic phenolate donor groups. The ligands of the latter group generally are unsuited to the oxidation of H2S to sulfur, while ligands in the first correlation are suitable for that purpose. Ligands that do not contain α-methylene groups are relatively resistant to oxidative degradation. Molecular mechanics is employed to compare the Fe(III) complexes of three such ligands, dipicolinic acid (DIPIC), pyridine-2-phosphonic-6-carboxylic acid (2PP6C), and 2-carboxy-8-hydroxyquinoline (CHOX). The calculations show that there is considerable strain in the formation of the Fe(II) and Fe(III) complexes of these ligands, both with respect to the O–O distance and the O-Fe-O angle. The relatively high stability of the CHOX complex compared to that of DIPIC, therefore, is due mainly to the higher basicity of the phenolate oxygen compared to the carboxylate groups of DIPIC. The higher stability of the Fe(III) complex of 2PP6C relative to that of DIPIC is due to the higher basicity and charge of the phosphonate group compared to a carboxylate group of DIPIC that it replaces. In spite of the lack of α-methylene groups in CHOX, the ligand undergoes rapid oxidative degradation when its iron chelate is used as a catalyst for the oxidation of H2S to sulfur by air. However, the oxidation products were found to also be effective catalysts for this process. Keywords: hydrogen sulfide, oxidation catalysis, dipicolinic acid, pyridine-2-phosphonic-6-carboyxlic acid, 2-carboxy-8-hydroxyquinoline.
Further examples of photocycloadditions of 1,3-diketonatoboron difluorides to olefins: a description of the reaction pattern and mechanism
Authors: Chow Yuan L. , Cheng Xianen , Wang Shi S. , Wu Susan P.
Published: May 2006

The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF2) with conjugated nitriles, ketones, and esters occurs more slowly than that with simple olefins and with fair regioselectivity. For these electron-deficient olefins, the cyclic analogues react more slowly than the acyclic ones and the cyano analogues react more slowly than all others; also a β-methyl substituent reverses the regioselectivity in adduct formation. Benzoylacetonatoboron difluoride (BABF2) photocycloadds to simple cyclic olefins from the excited state isomer in which the double bond is conjugated with the phenyl group, and occurs more slowly than that of the corresponding reaction of DBMBF2. The efficiency and regiochemistry of these cycloadditions have been explained with respect to the exciplex as the immediate intermediate. Keywords: photocycloaddition, dibenzoylmethanatoboron difluoride, benzoylacetonatoboron difluoride, exciplex.
Synthesis of sugar-modified 2,6-diaminopurine and guanine nucleosides from guanosine via transformations of 2-aminoadenosine and enzymatic deamination with adenosine deaminase
Authors: Robins Morris J. , Zou Ruiming , Hansske Fritz , Wnuk Stanislaw F.
Published: May 2006

Treatment of 2,6-diaminopurine riboside (2-aminoadenosine) with α-acetoxyisobutyryl bromide in acetonitrile gave mixtures of the trans 2′,3′-bromohydrin acetates 2. Treatment of 2 with zinc–copper couple effected reductive elimination, and deprotection gave 2,6-diamino-9-(2,3-dideoxy-β-D-erythro-pent-2-enofuranosyl)purine (3a). Treatment of 2 with Dowex 1 × 2 (OH−) resin in methanol gave the 2′,3′-anhydro derivative 4. Stannyl radical-mediated hydrogenolysis of 2 and deprotection gave the 2′-deoxy 6a and 3′-deoxy 7a nucleosides. Treatment of the 3′,5′-O-(tetraisopropyldisiloxanyl) derivative (5a) with trifluoromethanesulfonyl chloride – 4-(dimethylamino)pyridine gave 2′-triflate 5c. Displacement with lithium azide–dimethylformamide and deprotection gave the arabino 2′-azido derivative 8a, which was reduced to give 2,6-diamino-9-(2-amino-2-deoxy-β-D-arabinofuranosyl)purine (8b). Sugar-modified 2,6-diaminopurine nucleosides were treated with adenosine deaminase to give the corresponding guanine analogues. Keywords: adenosine deaminase, 2,6-diaminopurine nucleosides, deoxygenation, guanine nucleosides, nucleosides.
Activated cyclooctenones are effective dienophiles
Authors: Liu Hsing-Jang , Wang Dan-Xiong , Kim Jeung Bea , Browne Eric N.C. , Wang Yu
Published: May 2006

The first Diels–Alder addition of a diene to a cyclooctenone dienophile has been observed. Three activated cyclooctenone dienophiles 1, 2, and 3 are studied with a variety of simple and functionalized dienes. Diels–Alder adducts are produced in excellent yields under very mild Lewis acid catalyzed conditions. The usual orientation rules are followed and, as predicted, the products are formed for the most part exclusively by ester-endo addition. The stereoselectivity is influenced by the substitution pattern of the diene in some cases. The factors influencing the stereochemical selectivity of the addition are discussed in some detail. Keywords: 2-carbalkoxy-2-cyclooctenones, Diels–Alder reaction, six–eight fused ring system.
Theoretical study on the insertion reaction of CH(X2Π) with CH4
Authors: Wang Zhi-Xiang , Huang. Ming-Bao , Liu Ruo-Zhuang
Published: May 2006

The CH + CH4 reaction has been studied by means of ab initio molecular orbital calculations incorporating electron correlation with Møller–Plesset perturbation theory up to second and fourth orders with the 6-31G(d,p) and 6-311++G(2d,p) basis sets. An energetically feasible insertion reaction path has been found in the potential energy surface that confirms the experimental proposal for the mechanism of the CH + CH4 reaction. The feature of the mechanism for the CH + CH4 insertion reaction is found to be different from the feature of the mechanisms for the CH + NH3, CH + H2O, and CH + HF insertion reactions, but somewhat similar to that for the CH2 + CH4 insertion reaction. Energetic results for the CH + CH4 reactions are in agreement with experiment. Keywords: CH radical, methane, reaction mechanism.
Diphenylmethane and diphenyl ether — experimental conformations and torsional surfaces calculated with AM1, MNDO, PM3, and density functional theory (Becke3LYP)
Authors: Straßner Thomas
Published: May 2006

The complete energy surfaces of the torsion around the central C—O or C—CH2 bonds in diphenyl ether (DPE) and diphenylmethane (DPM) are calculated with semiempirical methods (AM1, MNDO, PM3) and density functional theory (Becke3LYP/3-21G). Stationary points are optimized at the Becke3LYP/6-31G(d) level of theory. The geometry of a very recently published X-ray structure of 4,4′-bis[N-(2,4,6-trimethyl)benzenesulfonamide]diphenylmethane (1), as well as the solid state structures of many other diphenyl ethers and diphenylmethanes, is found in the low-energy regions of the AM1 surfaces of the parent compounds. Keywords: Conformational analysis, diphenyl ether, diphenylmethane, quantum chemistry (AM1, MNDO, PM3), density functional theory (Becke3LYP).
Information on the noncrystalline phase of nascent iPP given by slow calorimetry
Authors: Zhang X. , Phuong-Nguyen H. , Bernazzani P. , Lapes I. , Delmas G.
Published: May 2006

Nascent isotactic polypropylene (iPP) has a lower crystallinity and a different X-ray pattern than recrystallized iPP. Heat flows during the melting of nascent highly stereoregular iPP samples are recorded with a Setaram C80 calorimeter over a wide T range (30–280 °C). The rate of heating–cooling is 1–3 K/h, i.e., much lower than with conventional DSC. Melting is performed after annealing at 30 < Tannealing < 140 °C and with or without substrate. The main peak, that found by DSC, is associated with melting of monoclinic crystals and gives an enthalpy ΔHDSC. Two other peaks, usually above and below the main peak, are observed. These are associated with a slower process of disordering a physical network, which was produced in the sample during polymerization. The sum of ΔHDSC and ΔHnetwork equals ΔHtotal. When melting is complete ΔHtotal is equal to ΔH0, the heat of fusion of perfect iPP crystals. This work presents new information on: (i) the noncrystalline phase of nascent iPP and the heat content of a semicrystalline polymer; (ii) the modifications of the melting process due to strain development, brought about by expansion in the material during the temperature ramp when a physical network is present; and (iii) the effect of a substrate on the polymer melting process. Keywords: nascent iPP, slow calorimetry, strain-melting, change of enthalpy, substrates.
Thermodynamics of mixtures containing the CO and OH groups. II. DISQUAC predictions on VLE and HE for ternary mixtures containing 1-alkanols, n-alkanones, and one organic solvent
Authors: González Juan Antonio , Fuente I. García De La , Cobos J.C.
Published: May 2006

Thermodynamic properties: vapour–liquid equilibria, VLE, or excess enthalpies, HE, for a set of 21 ternary mixtures of the type 1-alkanol + n-alkanone + organic solvent are studied in the framework of the DISQUAC group contribution model. This treatment is extended to the binaries involved. The DISQUAC analysis is developed on the basis of binary interactions only, that is, ternary interactions are neglected. Most of the interchange coefficients needed are available in the literature. The average relative standard deviations are 0.026 for pressure in the VLE (12 systems) and 0.098 in the HE (9 systems). The discrepancies observed are briefly discussed. Keywords: 1-alkanols, n-alkanones, group contribution, liquids, ternary systems, thermodyamics.
The influence of a non-micelle-forming surfactant on the electrocatalytic hydrogenation of carvone and limonene in aqueous medium at Raney nickel electrodes
Authors: Beraud Valérie , Thomalla Marc , Lessard Jean
Published: May 2006

The electrocatalytic hydrogenation (ECH) of carvone (1) and limonene (8) at a Raney nickel cathode was studied in aqueous solutions containing a non-micelle-forming surfactant (didodecyldimethylammonium bromide, DDAB). The efficiency of ECH of these substrates was markedly increased compared to that observed previously with micelle-forming surfactants, and this for very low DDAB concentrations, as a consequence of the strong adsorption of DDAB on the electrode. For the ECH of 8 in basic medium (pH 10), the major part of organic compounds (60–95%) was shown to be adsorbed on the electrode surface as an organic layer stabilized by an interfacial film of DDAB. Keywords: electrocatalytic hydrogenation, limonene, carvone, surfactant, emulsions, Raney nickel cathodes.
Functionalization and elaboration of ring A taxoid building blocks
Authors: Tjepkema Michael W. , Wong Timothy , Wilson Peter D. , Fallis Alex G.
Published: May 2006

The elaboration of the ring A aldehydes 1, 7, and 11 into more highly functionalized intermediates for taxoid synthesis is described. An improved route to the triene 4 and the adduct 28b is reported. Additional condensations of selected aldehydes (1,7) with the organolithium reagents derived from the substituted halodienes 8 and 14 afforded the allylic alcohols 10 and 15 with a diastereoselectivity of ~5:1. Further manipulation of these products by the installation of an α-keto-acetylenic dienophile provided a taxoid precursor with the C2, C9, C10, C13, and C20 oxygens installed in the case of 23 (from 7), and the less functionalized systems 27 and 27a (from 1). Keywords: taxoid, paclitaxel, Diels–Alder, cyclohexene, dienes.
In situ X-ray absorption fine structure and optical reflectance studies of electrodeposited nickel hydrous oxide films in alkaline electrolytes
Authors: Hu Yining , Bae In Tae , Mo Yibo , Scherson Daniel A. , Antonio Mark R.
Published: May 2006

X-ray absorption fine structure (XAFS) and optical reflectance spectroscopy (RS) have been used to examine in situ electronic and structural aspects of nickel hydrous oxide, α-Ni(OH)2(hyd), electrodes supported on gold in alkaline electrolytes as a function of their state of charge. The extended X-ray absorption fine structure (EXAFS) of α-Ni(OH)2(hyd) electrodes in the uncharged (UC, or discharged) and overcharged (OC, orfully charged) states yielded, in each case, a single set of two distinct nearest-neighbor shells, with distances, d(Ni—O)1 = 2.05 ± 0.02 Å and d(Ni—Ni)1 = 3.11 ± 0.02 Å for UC, and d(Ni—O)1 = 1.87 ± 0.02 Å and d(Ni—Ni)1 = 2.83 ± 0.02 Å for OC. The in situ EXAFS of films allowed to self-discharge following overcharge could be fit with contributions from both sets of shells, suggesting that only two types of nickel sites are sufficient to account for the redox chemistry of this material. These data, in addition to information derived both from quantitative X-ray absorption near-edge structure (XANES) and optical RS in the visible range, indicate that the excess anodic charge, i.e., beyond the one-electron oxidation of Ni2+ sites, observed during the first oxidation of freshly prepared α-Ni(OH)2(hyd) electrodes may not be related to oxidation state changes involving nickel sites in the lattice, and, therefore, do not support the existence of nickel sites with a formal oxidation state higher than three for charged or overcharged electrodes in this media. Keywords: nickel oxide, reflectance spectroscopy, EXAFS, in situ measurements.
Réorganisation de la double couche électrique suivant la désorption réductive d'une monocouche auto-assemblée d'alcanethiols sur l'or<111>
Authors: Yang Dong Fang , Morin Mario
Published: May 2006

We report a vibrational study of the reorganization of the electrical double layer following the reduction of a self-assembled nonanethiol monolayer on a Au <111> electrode. The absence of changes in the vibrational spectra taken in the potential range covering the double layer shows that the nonanethiol monolayer is stable over 800 mV. Important changes in the vibrational spectra of the water molecules are observed when the applied potential is more negative than the reduction potential of the thiol monolayer. The interaction between the water molecules and the gold electrode is modified by the electrode potential. For a potential corresponding to the onset of the reduction of the nonanethiol monolayer the spectroscopic results suggest that the water molecules interact weakly with the gold surface. However, when the potential is sufficiently negative to cause the evolution of hydrogen, the deformation mode of the water molecules moves to a lower energy, indicating a stronger interaction between the water molecule and the gold surface. Time-resolved vibrational measurements suggest that water clusters are formed immediately after the reductive desorption of the thiols and before a significant amount of molecular hydrogen is produced. Keywords: electrochemistry, electrical double layer, vibrational spectroscopy, thiols.
Conformational behavior and electronic structure of silylketenes studied with quantum chemical calculations and photoelectron spectroscopy
Authors: Muchall Heidi M. , Werstiuk Nick H. , Ma Jiangong , Tidwell Thomas T. , Sung Kuangsen
Published: May 2006

The He(I) photoelectron spectra of silylketenes (Me3Si)2C=C=O (1), Me5Si2CH=C=O (2), Me2Si(CH=C=O)2 (3), MeSi(CH=C=O)3 (4), (SiMe2CH=C=O)2 (5), and (CH2SiMe2CH=C=O)2 (6) have been recorded and their structures and orbital energies have been calculated by ab initio methods. Orbital energies for disilanes 2 and 5 are strongly dependent on a Si-Si-C-C torsional angle due to σ–π orbital interaction. Comparisons between experimental and simulated spectra show that 2 and 5 prefer conformations in which the Si—Si bond and ketene group(s) are approximately orthogonal (113° and 111°, respectively). Silylalkenes Me5Si2CH=CH2 (7) and (SiMe2CH=CH2)2 (8), which have been included in the computational study, show the same behavior as their corresponding silylketenes. Silylbis- and trisketenes 3–6 do not exhibit π–π interaction of any significance. For Si—Si containing compounds, the best agreement between experimental and computed data was obtained when Becke3LYP/6-31G*//HF/3-21G* was employed. Keywords: conformational behavior, electronic structure, photoelectron spectroscopy, quantum chemical calculations, silylketenes.
MODELING GENETIC REGULATORY NETWORKS: CONTINUOUS OR DISCRETE?
Authors: IVANOV IVAN , DOUGHERTY EDWARD R.
Published: May 2006

Selecting an appropriate mathematical model to describe the dynamical behavior of a genetic regulatory network plays an important part in discovering gene regulatory mechanisms. Whereas fine-scale models can in principle provide a very accurate description of the real genetic regulatory system, one must be aware of the availability and quality of the data used to infer such models. Consequently, pragmatic considerations motivate the selection of a model possessing minimal complexity among those capable of capturing the level of real gene regulation being studied, particularly in relation to the prediction capability of the model. This paper compares fine-scale stochastic-differential-equation models with coarse-scale discrete models in the context of currently available data and with respect to their description of switch-like behavior among specific groups of genes.
OPTIMAL IMPULSIVE HARVESTING OF A SINGLE-SPECIES WITH GOMPERTZ LAW OF GROWTH
Authors: ZHANG YUJUAN , XIU ZHILONG , CHEN LANSUN
Published: May 2006

In this paper we investigate the optimal harvesting problems of a single species with Gompertz law of growth. Based on continuous harvesting models, we propose impulsive harvesting models with constant harvest or proportional harvest. By using the discrete dynamical systems determined by the stroboscopic map, we discuss existence, stability and global attractivity of positive periodic solutions, and obtain the maximum sustainable yield and the corresponding optimal population level. At last, we compare the maximum sustainable yield of impulsive harvest with that of continuous harvest, and point out that proportional harvest is superior to constant harvest.
Modulation by bradykinin of angiotensin type 1 receptor-evoked RhoA activation of connective tissue growth factor expression in human lung fibroblasts
Authors: Huang Zhenhua , Taylor Linda , Liu Bin , Yu Jun , Polgar Peter
Published: May 2006

The mechanisms regulating the opposing physiological actions of bradykinin (BK) and angiotensin II (AngII) are not well understood. Here we investigate signaling interactions between these two effectors. Connective tissue growth factor (CTGF) expression in IMR-90, human lung fibroblasts, is used as the endpoint target. In these cells the BK B2 receptor (BKB2R) is expressed constitutively, while no binding of AngII is detected. An inducible expression system is used to insert AngII receptor 1 (AT1R) and to obtain a signal level in response to AngII at the magnitude of BK. AngII and BK activate G protein-coupled targets, arachidonate release from cellular phospholipid stores, and intracellular phosphatidylinositol turnover equally. Both activate ERK, JNK, and p38 equally. However, AngII activates, whereas BK inactivates, RhoA. AngII induces a rapid (1 h) CTGF mRNA expression. RhoA siRNA and RhoA activation inhibitor, Y-27632, markedly reduce the AngII effect. Simultaneous treatment with BK and AngII attenuates the AT1R action. Additionally, BK in the absence of AngII lowers CTGF mRNA expression below basal levels over a span of 4 h. An AT1R/BKB2R chimera lacking heterotrimeric G protein coupling continues to activate MAP kinases to the same extent as wild-type (WT) AT1R and BKB2R. However, the increase of CTGF mRNA expression by this mutant is low, almost identical with that obtained by the simultaneous treatment of the WT AT1R-expressing cells with BK and AngII. In this context the chimeric receptor displays the characteristics of both receptors. These data demonstrate that, in human lung fibroblasts, BK modulates the action of AngII through the small G protein RhoA, but in a Gαi/Gαq-independent manner.
Radical Evil in the Lockean State: The Neglect of the Political Emotions
Authors: Nussbaum Martha
Published: May 2006

All modern liberal democracies have strong reasons to support an idea of toleration, understood as involving respect, not only grudging acceptance, and to extend it to all religious and secular doctrines, limiting only conduct that violates the rights of other citizens. There is no modern democracy, however, in which toleration of this sort is a stable achievement. Why is toleration, attractive in principle, so difficult to achieve? The normative case for toleration was well articulated by John Locke in his influential A Letter Concerning Toleration , although his attractive proposal thus rests on a fragile foundation. Kant did much more, combining a Lockean account of the state with a profound diagnosis of ‘radical evil’, the tendencies in all human beings to militate against stable toleration and respect. But Kant proposed no mechanism through which the state might mitigate the harmful influence of ‘radical evil’, thus rendering toleration stable. One solution to this problem was proposed by Rousseau, but it has deep problems. How, then, can a respectful pluralistic society shore up the fragile human basis of toleration, especially in a world in which we need to cultivate toleration not only within each state, but also among peoples and states, in this interlocking world?
Virtue Epistemology and Moral Luck
Authors: Silcox Mark
Published: May 2006

Thomas Nagel has proposed that the existence of moral luck mandates a general attitude of skepticism in ethics. One popular way of arguing against Nagel’s claim is to insist that the phenomenon of moral luck itself is an illusion , in the sense that situations in which it seems to occur may be plausibly re-described so as to show that agents need not be held responsible for the unlucky outcomes of their actions. Here I argue that this strategy for explaining away moral luck fails because it does not take account of the fact that agents in morally unlucky circumstances are uniformly subject to a very specific type of epistemic obligation. I then proceed to sketch out an alternative strategy for blocking the inference to skepticism, one that makes use of the distinctive explanatory resources provided by epistemic virtue theory.
Measuring nasal bacterial load and its association with otitis media
Authors: Smith-Vaughan Heidi , Byun Roy , Nadkarni Mangala , Jacques Nicholas A , Hunter Neil , Halpin Stephen , Morris Peter S , Leach Amanda J
Published: May 2006

Background

Nasal colonisation with otitis media (OM) pathogens, particularly Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, is a precursor to the onset of OM. Many children experience asymptomatic nasal carriage of these pathogens whereas others will progress to otitis media with effusion (OME) or suppurative OM. We observed a disparity in the prevalence of suppurative OM between Aboriginal children living in remote communities and non-Aboriginal children attending child-care centres; up to 60% and <1%, respectively. This could not be explained by the less dramatic difference in rates of carriage of respiratory bacterial pathogens (80% vs 50%, respectively). In this study, we measured nasal bacterial load to help explain the different propensity for suppurative OM in these two populations.

Methods

Quantitative measures (colony counts and real-time quantitative PCR) of the respiratory pathogens S. pneumoniae, H. influenzae and M. catarrhalis, and total bacterial load were analysed in nasal swabs from Aboriginal children from remote communities, and non-Aboriginal children attending urban child-care centres.

Results

In both populations nearly all swabs were positive for at least one of these respiratory pathogens. Using either quantification method, positive correlations between bacterial load and ear state (no OM, OME, or suppurative OM) were observed. This relationship held for single and combined bacterial respiratory pathogens, total bacterial load, and the proportion of respiratory pathogens to total bacterial load. Comparison of Aboriginal and non-Aboriginal children, all with a diagnosis of OME, demonstrated significantly higher loads of S. pneumoniae and M. catarrhalis in the Aboriginal group. The increased bacterial load despite similar clinical condition may predict persistence of middle ear effusions and progression to suppurative OM in the Aboriginal population. Our data also demonstrated the presence of PCR-detectable non-cultivable respiratory pathogens in 36% of nasal swabs. This may have implications for the pathogenesis of OM including persistence of infection despite aggressive therapies.

Conclusion

Nasal bacterial load was significantly higher among Aboriginal children and may explain their increased risk of suppurative OM. It was also positively correlated with ear state. We believe that a reduction in bacterial load in high-risk populations may be required before dramatic reductions in OM can be achieved.
Autoimmune targeting of key components of RNA interference
Authors: Jakymiw Andrew , Ikeda Keigo , Fritzler Marvin J , Reeves Westley H , Satoh Minoru , Chan Edward KL
Published: May 2006

RNA interference (RNAi) is an evolutionarily conserved mechanism that is involved in the post-transcriptional silencing of genes. This process elicits the degradation or translational inhibition of mRNAs based on the complementarity with short interfering RNAs (siRNAs) or microRNAs (miRNAs). Recently, differential expression of specific miRNAs and disruption of the miRNA synthetic pathway have been implicated in cancer; however, their role in autoimmune disease remains largely unknown. Here, we report that anti-Su autoantibodies from human patients with rheumatic diseases and in a mouse model of autoimmunity recognize the human Argonaute (Ago) protein, hAgo2, the catalytic core enzyme in the RNAi pathway. More specifically, 91% (20/22) of the human anti-Su sera were shown to immunoprecipitate the full-length recombinant hAgo2 protein. Indirect immunofluorescence studies in HEp-2 cells demonstrated that anti-Su autoantibodies target cytoplasmic foci identified as GW bodies (GWBs) or mammalian P bodies, structures recently linked to RNAi function. Furthermore, anti-Su sera were also capable of immunoprecipitating additional key components of the RNAi pathway, including hAgo1, -3, -4, and Dicer. Together, these results demonstrate an autoimmune response to components of the RNAi pathway which could potentially implicate the involvement of an innate anti-viral response in the pathogenesis of autoantibody production.
Severe muscular dystrophy in mice that lack dystrophin and α7 integrin
Authors: Rooney Jachinta E. , Welser Jennifer V. , Dechert Melissa A. , Flintoff-Dye Nichole L. , Kaufman Stephen J. , Burkin Dean J.
Published: May 2006

The dystrophin glycoprotein complex links laminin in the extracellular matrix to the cell cytoskeleton. Loss of dystrophin causes Duchenne muscular dystrophy, the most common human X-chromosome-linked genetic disease. The α7β1 integrin is a second transmembrane laminin receptor expressed in skeletal muscle. Mutations in the α7 integrin gene cause congenital myopathy in humans and mice. The α7β1 integrin is increased in the skeletal muscle of Duchenne muscular dystrophy patients and mdx mice. This observation has led to the suggestion that dystrophin and α7β1 integrin have complementary functional and structural roles. To test this hypothesis, we generated mice lacking both dystrophin and α7 integrin (mdx/α7-/-). The mdx/α7-/- mice developed early-onset muscular dystrophy and died at 2-4 weeks of age. Muscle fibers from mdx/α7-/- mice exhibited extensive loss of membrane integrity, increased centrally located nuclei and inflammatory cell infiltrate, greater necrosis and increased muscle degeneration compared to mdx or α7-integrin null animals. In addition, loss of dystrophin and/or α7 integrin resulted in altered expression of laminin-α2 chain. These results point to complementary roles for dystrophin and α7β1 integrin in maintaining the functional integrity of skeletal muscle.
Diamond in the Rough
Authors: Hayward Steven F.
Published: May 2006

This review of Jared Diamond's new book, Collapse, analyses the book in the context of other Malthusian treatments of environmental issues, noting its original and unconventional analysis of the role of environmental factors in the fate of past cultures, but critiquing its lack of imagination for the institutional dimensions of environmental decision-making for our future today.
Divergent Thinking in the Construction of Architectural Models
Authors: Talbott Kyle W.
Published: May 2006

The article examines one little understood but ubiquitous form of divergent thinking achieved intermittently during the act of drawing or modeling. It is argued that this phenomenon, here called intermittent divergence, is rooted in a special kind of interaction between perception and imagination, and that this interaction has specific experiential requirements. Three requirements are defined. The resulting new theory then provides a framework for the critical analysis of conventional digital modeling and parametric modeling. Conventional modeling methods are shown to satisfy the requirements for intermittent divergence, while parametric modeling methods are shown to undermine them. The article concludes that parametric systems, as currently developed, could inhibit rather than augment this important route to creativity. Additionally, the article questions prevailing beliefs about the computer support of creativity, including the premise that sketching is an ideal creative medium and the premise that ambiguity in graphical depictions is key to the support of creativity. The theory offers an alternative view on these issues.
Dimerization of ADAR2 is mediated by the double-stranded RNA binding domain
Authors: Poulsen Hanne , Jorgensen Rasmus , Heding Anders , Nielsen Finn C. , Bonven Bjarne , Egebjerg Jan
Published: May 2006

Members of the family of adenosine deaminases acting on RNA (ADARs) can catalyze the hydrolytic deamination of adenosine to inosine and thereby change the sequence of specific mRNAs with highly double-stranded structures. The ADARs all contain one or more repeats of the double-stranded RNA binding motif (DRBM). By both in vitro and in vivo assays, we show that the DRBMs of rat ADAR2 are necessary and sufficient for dimerization of the enzyme. Bioluminescence resonance energy transfer (BRET) demonstrates that ADAR2 also exists as dimers in living mammalian cells and that mutation of DRBM1 lowers the dimerization affinity while mutation of DRBM2 does not. Nonetheless, the editing efficiency of the GluR2 Q/R site depends on a functional DRBM2. The ADAR2 DRBMs thus serve differential roles in RNA dimerization and GluR2 Q/R editing, and we propose a model for RNA editing that incorporates the new findings.
Upward Slopes and Inf-Convolutions
Authors: Flåm Sjur Didrik
Published: May 2006

Nonsmooth analysis and exact penalty methods give much prominence to functions that exit from certain lower-level sets with positive upward slope. A novel, weak version of such slopes is formalized here and studied in terms of differential properties. Applied to inf-convolutions, those properties help to recover and extend recent results on nonconvex separation, cooperative production (or market) games, and welfare economics.
Ermittlung der Messunsicherheit – Vergleich von Ergebnissen aus Berechnung und Experiment (Determination of Measurement Uncertainty – Comparison of Results from Calculation and Experiment)
Authors: Hinrichs Wilfried
Published: May 2006

In einem Ringversuch wurde die Messung der Maschenweiten und Drahtdicken von Drahtgeweben untersucht. Die experimentell ermittelten Präzisionsdaten wurden berechneten Schätzwerten der Messunsicherheit nach GUM gegenübergestellt. Der Vergleich lieferte plausible Resultate, wenn systematische Komponenten zugelassen und Rahmenbedingungen des Ringversuchs in der Berechnung angenähert wurden. Die Messfähigkeit von Drahtdicken in Geweben wurde nachgewiesen. Die Ermittlung der Maschenweiten war oft nicht hinreichend präzise. Die Quantifizierung bestätigte die qualitativen Praxiserfahrungen.
An evaluation of the use of translocated blanket bog vegetation for heathland restoration
Authors: Standen V. , Owen M.J.
Published: May 2006

Abstract. The decision was taken by an opencast coal mining company to translocate on‐site blanket bog vegetation, on completion of mining, at a site in Co. Durham, UK, both to preserve it and to use it to enhance recolonization. The vegetation of the treatments was monitored for seven years after site completion and this paper reports on the progress of the translocated material and its effect on recolonization. Translocation of large turves of blanket bog into carefully prepared receptor cells preserved most of the vegetation intact, but resulted in severe decline in the frequency of Sphagnum, while the design of the receptor site as strips of translocated vegetation enclosing strips of spread, stored peat accelerated recolonization of the intervening bare peat by Calluna vulgaris, but not of other target species. This attempt to translocate blanket bog vegetation and at the same time use it to accelerate recolonization was only partly successful. It was concluded that the ecological requirements of species known to be significant for ecosystem function, such as Sphagnum, must be fulfilled if translocation of blanket bog is to be attempted in future.
Temperature Relations in Two Species of Tropical West American Littorines
Authors: Markel Raymond P.
Published: May 2006

The intertidal zonation and temperature relationships of two Littorina species which co—occurred over a wide range of latitudes in the West American tropics were studied. It was found that L. aspera lives higher in the intertidal zone, experiences higher tissue temperatures in the field, and has a higher upper lethal temperature than L. modesta. A positive correlation between intertidal height and heat resistance has been observed previously in temperature latitudes. A similar correlation in two high intertidal tropical snails was found in this study. There is a large difference between maximum temperature recorded in the field and thermal tolerance determined in the laboratory, providing the animals with a considerable safety factor. It is suggested that temperature is a major factor influencing the intertidal distribution of these species.
Multivariate Approaches to Algal Stratagems and Tactics in Systems Analysis of Phytoplankton
Authors: Allen T. F. H. , Koonce J. F.
Published: May 2006

Numerical classifications and principal components ordinations were performed on species from 57 weekly samples of photoplankton from Lake Wingra. The data were considered in absolute and relative terms before and after transformation to presence/absence and logarithmic quantities. The data were also analyzed, taking into account growth rates in the samples, by means of a transformation that replaced the scores of species present by the productivity of the sample as determined by C_(14) uptake/biomass. It is shown that different transformations can reveal different but biologically meaningful aspects of the data. These different biological aspects are species similarities based on either short—term survival expedients in particular environmental circumstances, species tactics, or long—range growth patterns, involving breadth of tolerance and place in the community, that is, species stratagems. Most phytoplankton species in Lake Wingra adopt one of three stratagems: either ungrazed, slow—growing and very persistent, or ungrazed, fast—growing and of intermediate duration, or grazed fast—growing and ephemeral. Tactical information is relevant to particular systems, while strategic information is needed in ecosystem comparison and for models applicable to several systems.
Amphipod Amplexus, The Significance of Ecotypic Variation
Authors: Strong Donald R.
Published: May 2006

The proportion of the female molt cycle spent in amplexus varies inheritably among several populations of the talitrid amphipod Hyalella azteca. Duration of amplexus is negatively correlated with an index of the intensity of predation by visually orienting fish. As amplexus renders the amphipods more vulnerable to these fish, I hypothesize that this type of predation selects for an abbreviation selects for an abbreviation of the amplexed phased of the female molt cycle.
Sampling and Ordination Characteristics of Computer‐Simulated Individualistic Communities
Authors: LaFrance Charles R.
Published: May 2006

A set of artificial communities which simulate a series of one—dimensional continua with varying tendencies of species modes to aggregate into species groupings of discrete communities is produced by computer. In one of these, complexity is increased by the inclusion of small—scale pattern on the overall continuum pattern. These communities are sampled with a variety of sample shapes. The sample data show that the detection of large—scale pattern is unaffected by sample shape, but for strong small—scale pattern rectangular quadrats are more efficient as predicted. Both direct on environmental and indirect or vegetational ordinations approximate the underlying parametric species distribution with reasonable accuracy. The sampling and analytic procedures used in ordination do not necessarily bias the interpretation of vegetational data toward the continuum as suggested by some of the critics of the continuum concept.
Ecological Significance of Four Critical Elements in Plants of Raised Spagnum Peat Bogs
Authors: Small Ernest
Published: May 2006

The concentrations of N, P, Mn, and Al in plants of two ombrotrophic bogs and four adjacent environments were examined. The current year's foliage of the evergreen bog species, as contrasted with the older leaves, invariably possessed higher concentrations of N and P and lower concentrations of Al and Mn. Within the bog species, the composition of the current year's foilage of the evergreens was not significantly different for any of the elements from that of the deciduous species. Foliage of the bog species was lower in content of N and P than the foliage of plants of other habitats and reflects the paucity of available N and P in the bog substrate. Broad—leaved evergreen leaves of bog plants appear to manufacture more photosynthate per acquired unit of N or P than do deciduous leaves, primarily because of their longevity. The high occurrence of evergreenness in infertile environments may therefore reflect a decreased need to acquire N and P from a substrate deficient in these elements. Mn and Al contents were comparable in the bog plants to plants of other habitats, despite potentially toxic levels of these elements in acid bogs. Apparently many bogs plants selectively exclude Mn and Al.
Competition for Urea among Estuarine Microorganisms
Authors: Remsen Charles C. , Carpenter Edward J. , Schroeder Brian W.
Published: May 2006

Phytoplankton were responsible for the major part of the urea decomposition in the Savannah—Wilmington—Ogeechee estuaries and adjacent coastal waters in Georgia. This is an exception to the general rule that bacteria are favored of algae in the competition for dissolved organic compounds. Filtration of estuary water through a 20—μ mesh filter did not significantly change the concentration of urea—decomposing bacteria; there was, however, a significant change in phytoplankton cell concentrations, chlorophyll a, and urea decomposition rates. Thus, any differences in the decomposition of urea in filtered and unfiltered aliquots could be attributed to the phytoplankters removed by filtration. Average cell concentrations and chlorophyll a removed by filtration was 15% and 39% of the totals, respectively. However, the removal of urea—decomposing activity average 53% of the total. This indicates that the phytoplankters removed by filtration, mainly diatoms with large cross—sectional areas such as Rhizosolenia, Chaetoceros, Asterionella, Thalassiosira, etc., were responsible for proportionally higher amounts of urea decomposition than would be indicated on a purely cell—number basis. Urea concentrations ranged from 0.6 to 8.9 μM, with the highest values (average 3.41 μM) being found in the more polluted Savannah estuary. Lower values, generally 1—2 μM, were observed in the Wilmington and Ogeeche estuaries. Fresh water generally had slower urea decomposition rates (average 6.2 μmmoles liter—1 hr—1) than brackish waters (average 19.6 μmmoles liter—1 hr—1). Turnover times for urea, calculated from these average values, was 25 days for fresh water and 4 days for brackish water.
Production and Chemical Composition of Saururus Cernuus L. at Sites of Different Fertility
Authors: Boyd Claude E. , Walley W. Wayne
Published: May 2006

Total dry matter standing crops of Saururus cernuus L. at 25 sites in the southeastern United States ranged from 445 to 2,250 g/m2. Aboveground production ranged from 184 to 1.199 g/m2 and averaged 54.9% of the total production. Total and shoot standing crops increased with increasing concentrations of dilute—acid—soluble phosphorus in soils and increasing soil pH. Concentration of inorganic nutrients varied considerably in plants from different sites. The ratio of cell—wall constituents in shoots was greater at sites supporting high shoot standing crops than at sites with lower shoot production. Crude protein comprised from 9.06% to 16.12% of the dry weight of shoots from different stands. Total available carbohydrate in roots averaged 17.1%. Greater quantities of carbohydrate accumulated in roots at productive sites, but the percentage carbohydrate content of roots was not correlated with standing crop.