bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using an intensity‐scale technique to assess the added benefit of high‐resolution model precipitation forecasts
Authors: Mittermaier Marion P. 
Published: May 2006

AbstractDeterministic precipitation forecasts from the 12‐ and 4‐km versions of the Unified Model (UM) were compared using an intensity‐scale technique. Averaging raw model output is always recommended to minimise grid‐scale errors. The retained detail in averaged 4‐km forecasts produces an improved prediction of larger accumulations. © Crown Copyright 2006. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd.
The interaction between N‐n‐undecyl‐N′‐(sodium p‐aminobenzenesulfonate) thiourea and serum albumin studied using various spectroscopies and the molecular modeling method
Authors: Cui Fengling , Cui Yanrui , Luo Hongxia , Yao Xiaojun , Fan Jing , Lu Yan 
Published: May 2006

AbstractThe preparation and characteristics of N‐n‐undecyl‐N′‐(sodium‐p‐aminobenzenesulfonate) thiourea (UPT), a new water‐soluble reagent with a saturated fatty hydrocarbon group, were described. The interactions of UPT with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using fluorescence spectroscopy in combination with ultraviolet (UV) absorption spectroscopy, circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and the molecular modeling method. UPT exhibited a strong ability to quench the intrinsic fluorescence of both BSA and HSA through a static quenching procedure. The binding constants of UPT and BSA or HSA were determined at different temperatures based on the relevant fluorescence data. The binding sites were obtained and the acting force was suggested to be mainly hydrophobic interaction, which was consistent with the result of the molecular modeling study, and there were also a number of hydrogen bonds between UPT and HSA. The results of determination of the proteins in bovine serum or human serum by this method were very close to those obtained by using Coomassie Brilliant Blue G‐250 colorimetry. A practical method was proposed for the determination of UPT in bovine serum or human serum samples with satisfactory results. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 170–181, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Muscarinic Receptors: A Comparative Analysis of Structural Features and Binding Modes through Homology Modelling and Molecular Docking
Authors: Pedretti Alessandro , Vistoli Giulio , Marconi Cristina , Testa Bernard 
Published: May 2006

AbstractThree‐dimensional models of the five human muscarinic receptors were obtained from their known sequences. Homology modelling based on the crystallographic structure of bovine rhodopsin yielded models compatible with known results from site‐directed mutagenesis studies. The only exceptions were the cytoplasmic loop 3 (CL3) in the five receptors, and the large C‐terminal domain in M1. Here, homology modelling with other closely related proteins allowed to solve these gaps. A detailed comparative discussion of the five models is given. The second part of the work involved docking experiments with the physiological ligand acetylcholine, again yielding results entirely compatible with results from mutagenesis experiments. The study revealed analogies and differences between the five receptors in the residues, and interactions leading to the recognition and binding of acetylcholine.
Inhibition of Histidine Ammonia Lyase by Heteroaryl‐alanines and Acrylates
Authors: Katona Adrian , Toşa Monica Ioana , Paizs Csaba , Rétey János 
Published: May 2006

AbstractHistidine ammonia lyase (HAL) catalyzes the elimination of ammonia from the substrate to form (E)‐urocanate. The interaction between HAL and acrylic acids or alanines substituted with heteroaryl groups in the β‐position was investigated. These proved to be strong competitive inhibitors when the heteroaryl groups were furanyl, thiophenyl, benzofuranyl, and benzothiophenyl, carrying the alanyl or acrylic side chains either in 2 or 3 positions, with Ki values between 18 and 139 μM. The exception was (furan‐3‐yl)alanine which was found to be inert. Tryptophan and 1‐methyltryptophan, as well as the corresponding acrylates (=prop‐2‐enoates), are strong mixed inhibitors of HAL. Theoretically, L‐histidine can be dissected into 4‐methyl‐1H‐imidazole and glycine. Whereas these two compounds separately are only very weak inhibitors of HAL, equimolar amounts of both show a Ki value of 1.7±0.09 mM which is to be compared with the Km value of 15.6 mM for the normal reaction. We conclude that 5‐methyl‐1H‐imidazole and glycine mimic the substrate and occupy the active site of HAL in a similar orientation.
Nitroimidazoles, Part 2
Authors: Al‐Masoudi Najim A. , Al‐Soud Yaseen A. , Kalogerakis Aris , Pannecouque Christophe , De Clercq Erik 
Published: May 2006

AbstractA series of 5‐alkylamino and 5‐alkylsulfanyl derivatives of 1‐aryl‐2‐alkyl‐4‐nitro‐1H‐imidazoles 12–21, 31, and 34 were synthesized by a simple method with the aim to develop novel HIV non‐nucleoside reverse transcriptase inhibitors (NNRTIs). All the new compounds were tested against HIV‐1 and HIV‐2 in MT‐4 cells. Compound 21, with an arylsulfanyl group at C(5) of the 4‐nitro‐1H‐imidazole backbone showed an EC50 value of 0.22 μg/ml against HIV‐1 with a therapeutic index of 13. This means that compound 21 was cytotoxic to MT‐4 cells at a CC50 value of 2.57 μg/ml; also compounds 8, 22–25, 28, and 29 were cytotoxic to MT‐4 cells within the 0.4–4 μg/ml concentration range. Compounds 8, and 12–21 were evaluated, as a rule, but found inactive at non‐toxic concentrations against hepatitis C virus, herpes simplex type 1 and 2, cytomegalovirus (CMV), varicella‐zoster virus (VZV), vaccinia virus, and vesicular stomatitis virus, and a number of other viruses. Yet, the therapeutic index of compounds 17 and 21 for CMV and VZV approached the tenfold cut‐off point. Compounds 8 and 21 exhibited some cytostatic activity against leukemia and melanoma cell lines.
Use of Phospholipid Transfer Protein as a Probe to Study the Lipid Dynamics and Alkaline Phosphatase Activity in the Brush Border Membrane of Human Term Placenta
Authors: Sanyal Sankar N. , Goyal Meenakshi , Kanwar Shailender S. , Kaushal Shivani 
Published: May 2006

AbstractIncubation of placental brush border membrane (BBM) along with sonicated vesicles of exogenous lipids (egg yolk PC) in the presence of phospholipid‐transfer protein (PL‐TP) showed a decrease in the alkaline phosphatase activity due to the change in the membrane micro‐environment, such as fluidity. Effect of substrate concentration was tested by Lineweaver–Burk plot, which showed decreased Vmax and KM. The effect of temperature was probed by the Arrhenius plot, which showed no change in transition temperature, but a decline in the energy of activation both below and above the transition temperature. The protein‐catalyzed transfer of phospholipid from the donor unilamellar vesicles resulted in a substantial increase in the BBM phospholipid and a net decrease in cholesterol/phospholipid molar ratio. The change in membrane fluidity was assessed by translational as well as rotational diffusion of membrane extrinsic fluorescent probes, pyrene and diphenyl‐hexatriene. An increased lateral mobility was recorded by the increased pyrene excimer formation. A decrease in fluorescent polarization of diphenyl‐hexatriene was observed, which led to the decrease in fluorescence anisotropy and order parameter, and therefore, an increase in membrane fluidity (rotational diffusion). Mean anisotropy parameter was also decreased in the presence of PL‐TP. Thus, the placental BBM alkaline phosphatase activity showed a distinct lipid dependence which may have important physiological consequences.
A Fatal Effect of Hornet Venom on Rat‐Brain Cortical Neurons
Authors: Cohen‐Armon Malka , Visochek Leonid , Priel Esther , Ishay Jacob S. 
Published: May 2006

AbstractIn a previous study, it was shown that the hornet venom or, more specifically, its venom sac extract (VSE) possesses deoxyribonuclease activity that exerts an effect both on insects as well as on mammals. We have now examined the effect of hornet VSE on primary culture of rat cortical neurons. Judging on the basis of our results, VSE induces a rapid cell death by a) permeabilizing the cell membrane, b) inducing DNA breaks, and c) cleaving the nuclear protein poly‐ADP‐ribose polymerase (PARP‐1), thereby preventing DNA repair.
Syntheses and Odor Descriptions of Cyclopropanated Compounds, Part 6
Authors: Sakauchi Hiroyuki , Asao Hiroki , Hasaba Tsutomu , Kuwahara Shigefumi , Kiyota Hiromasa 
Published: May 2006

AbstractAnalogs of aliphatic monoterpene dienols (geraniol, nerol, linalool, and lavandulol) and non‐branched alcohols (norleaf alcohol, matsutake alcohol, etc.) bearing a cyclopropane ring were synthesized, and their odor characteristics were examined. Most of the analogs show odor properties different from their parent compounds.
Synthesis of New Phytogrowth‐Inhibitory Substituted Aryl‐p‐Benzoquinones
Authors: de Almeida Barbosa Luiz Cláudio , de Alvarenga Elson Santiago , Demuner Antônio Jacinto , Virtuoso Luciano Sindra , Silva Antônio Alberto 
Published: May 2006

AbstractReaction of [(2‐alkyloxy)methyl]‐1,4‐dimethoxybenzene 10 (alkyl=butyl, hexyl, decyl, tridecyl, tetradecyl, hexadecyl, and octadecyl) with ceric ammonium nitrate in order to produce p‐benzoquinones (=cyclohexa‐2,5‐diene‐1,4‐diones) afforded 5‐[(alkyloxy)methyl]‐2‐(4‐formyl‐2,5‐dimethoxyphenyl)benzo‐1,4‐quinones 12a–12g in yields that varied from 46 to 97%, accompanied by 2‐[(alkyloxy)methyl]benzo‐1,4‐quinones 11a–11g in only small quantities (≤5%). These quinones resemble the natural phytotoxic compound sorgoleone, found in Sorghum bicolor. This reaction exemplifies a general procedure for the synthesis of novel aryl‐substituted p‐benzoquinones. The selective effects of compounds 12a–12g, at the concentration of 5.5 ppm, on the growth of Cucumis sativus, Sorghum bicolor, Euphorbia heterophylla, and Ipomoea grandifolia were evaluated. All compounds caused some inhibition upon the aerial parts and root growth of the tested plants. The most active compound, 2‐(4‐formyl‐2,5‐dimethoxyphenyl)‐5‐[(tridecyloxy)methyl]‐benzo‐1,4‐quinone (12d), caused between 3 and 18%, and 12 and 29% inhibition on the roots and aerial parts development of Cucumis sativus and Sorghum bicolor, respectively, and between 77 and 85%, and 34 and 52% inhibition on the roots and aerial parts growth of Euphorbia heterophylla and Ipomoea grandifolia, respectively.
Preliminary Investigation on Mgbede‐20 Oil‐Polluted Site in Niger Delta, Nigeria
Authors: Osuji Leo C. , Idung Iniobong D. , Ojinnaka Chukwunnoye M. 
Published: May 2006

AbstractSoil physicochemical properties (pH, electrical conductivity (EC), % moisture, total organic carbon (TOC), total organic matter (TOM)), total extractable hydrocarbon content (THC), and micronutrient (Mn, Fe, Cu, Zn) levels of the Mgbede‐20 oil‐impacted site in Niger Delta, Nigeria, were investigated. Both oil‐impacted and their background control soils were found to be acidic especially at surface depth. A slightly higher EC value of 107.4±15.0 μS cm−1 was obtained for the subsurface‐polluted soils. Of the micronutrients investigated, only Fe exceeded its acceptable limit (>100 mg/kg). The observed increase in moisture content resulting from the oil's aggregation of soil particles may lower soil porosity, and increase resistance to penetration and hydrophobicity. Soil pH can be adjusted by aeration to complete the microbially mediated oxidation of the organic acids, followed by the addition of agricultural lime to provide some buffering capacity to the soil.
Lewis Acid Stabilized OPI3: Implications for the Nature of Free OPI3
Authors: Gonsior Marcin , Müller Lutz , Krossing Ingo 
Published: May 2006

AbstractWhile reinvestigating the published synthesis of OPI3, it became evident from the experiments that phosphoryl triodide may only be formed as an intermediate and that the end products of the reaction of OPCl3 with LiI are PV oxides, PI3, I2, and LiCl. This is also in agreement with MP2/TZVPP calculations, which assign ΔrH° (ΔrG°) [ΔrG° in CHCl3] for the disproportionation of OPI3 as −7 (−18) [−17 kJ mol−1] (assuming P4O10 as the PV oxide). The first products of this reaction visible in a low‐temperature in situ 31P NMR experiment are P2I4 and PI3, as well as traces of a compound that may be OPCl2I. By contrast, it was possible to prepare and structurally characterize Lewis acid [A] stabilized [A]←OPX3 adducts, where [A] is Al(ORF)3 for X=Br and Al(ORF)2(μ‐F)Al(ORF)3 for X=I (RF=C(CF3)3). These adducts are formed on decomposition of PX4+[Al(ORF)4]−; high yields of Br3PO→Al(ORF)3 (δ(31P)=−65) were obtained, while I3PO→Al(ORF)3 (δ(31P)=−337) and I3PO→Al(ORF)2(μ‐F)Al(ORF)3 (δ(31P)=−332) are only formed as by‐products. The main product of the room‐temperature decomposition of PI4+[Al(ORF)4]− is PI4+[(RFO)3Al(μ‐F)Al(ORF)3]−, which was also characterized by X‐ray crystallography and was independently prepared from Ag+[(RFO)3Al(μ‐F)Al(ORF)3]−, PI3, and I2.
Self‐Assembly of Semifluorinated Dendrons Attached to Electron‐Donor Groups Mediates Their π‐Stacking via a Helical Pyramidal Column
Authors: Percec Virgil , Glodde Martin , Peterca Mihai , Rapp Almut , Schnell Ingo , Spiess Hans W. , Bera Tushar K. , Miura Yoshiko , Balagurusamy Venkatachalapathy S. K. , Aqad Emad , Heiney Paul A. 
Published: May 2006

AbstractSemifluorinated first‐generation self‐assembling dendrons attached via a flexible spacer to electron‐donor molecules induce π‐stacking of the donors in the center of a supramolecular helical pyramidal column. These helical pyramidal columns self‐organize in various columnar liquid crystal phases that mediate self‐processing of large single crystal liquid crystal domains of columns and self‐repair their intracolumnar structural defects. In addition, all supramolecular columns exhibit a columnar phase at lower temperatures that maintains the helical pyramidal columnar supramolecular structure and displays higher intracolumnar order than that in the liquid crystals phases. The results described here demonstrate the universality of this concept, the power of the fluorous phase or the fluorophobic effect in self‐assembly and the unexpected generality of pyramidal liquid crystals.
Formation of Rack‐ and Grid‐Type Metallosupramolecular Architectures and Generation of Molecular Motion by Reversible Uncoiling of Helical Ligand Strands
Authors: Stadler Adrian‐Mihail , Kyritsakas Nathalie , Graff Roland , Lehn Jean‐Marie 
Published: May 2006

AbstractThe interaction of appropriate metal ions (PbII, ZnII) with helical ligand strands, obtained by hydrazone polycondensation, generates polymetallic supramolecular architectures of rack and grid types, by uncoiling of the ligand. The interconversion between the helical free ligand and the linearly extended ligand in the complexes produces reversible ion‐induced, nanomechanical molecular motions of large amplitude. It has been integrated in an acid–base neutralisation fuelled process, which links the extension/contraction of the ligand strands to alternating changes in pH.
Gold Catalysis: Phenol Synthesis in the Presence of Functional Groups
Authors: Hashmi A. Stephen K. , Weyrauch Jan P. , Kurpejović Elzen , Frost Tanja M. , Miehlich Burkhard , Frey Wolfgang , Bats Jan W. 
Published: May 2006

AbstractThe effect of different substituents, such as bromo, chloromethyl, hydroxymethyl, formyl, acetyl, carboxy, and acylated hydroxymethyl and ammonium groups, on the furan ring of substrates in gold‐catalyzed phenol synthesis has been investigated. The furan ring was also replaced by different heterocycles, such as pyrroles, thiophenes, oxazoles, and a 2,4‐dimethoxyphenyl group; gold catalysis then delivered no phenols, but occasionally other products were obtained. [Ru3(CO)12] also catalyzed the conversion of 1 at a low rate, [Os3(CO)12] failed as a catalyst, and with [Co2(CO)8] the alkyne complex 19 can be obtained, it does not lead to any phenol but reacts with norbornene to give the product of a Pauson–Khand reaction. Efforts to prepare vinylidene complexes of 1 provided the only evidence for these species; in the presence of a phosphane ligand with ruthenium an interesting deoxygenation to 22 was observed. The phenol 2 c was converted to the allyl ether, a building block for para‐Claisen rearrangements, and to the aryl triflate, a building block for cross‐coupling reactions.
Aromaticity of Giant Polycyclic Aromatic Hydrocarbons with Hollow Sites: Super Ring Currents in Super‐Rings
Authors: Hajgató Balázs , Deleuze Michael S. , Ohno Koichi 
Published: May 2006

AbstractWe present a systematic theoretical study based on semi‐empirical, Hartree–Fock (HF), and density functional theory (DFT) models of a series of polycyclic aromatic hydrocarbons (PAHs) that exhibit hollow sites. In this study we focus particularly on the magnetic criteria of aromaticity, namely 1H NMR and nucleus‐independent chemical shifts (NICS), and on their relationships with other electronic properties. The computed shifts and NICS indices indicate that an external magnetic field induces exceptionally strong ring currents in even‐layered PAH doughnuts, in particular in the layer directly adjacent to the central hole of double‐layered compounds. These exceptionally strong ring currents also correlate with particularly small HOMO–LUMO gaps and electronic excitation energies and to abnormally high polarizabilities, indicating in turn that these compounds have a more pronounced metallic character. Comparison is made with further depictions of aromaticity in these systems and in [18]–[66]annulene rings by employing topological, structural, and energetic criteria.
Chiral Phosphane Alkenes (PALs): Simple Synthesis, Applications in Catalysis, and Functional Hemilability
Authors: Piras Elisabetta , Läng Florian , Rüegger Heinz , Stein Daniel , Wörle Michael , Grützmacher Hansjörg 
Published: May 2006

AbstractA simple synthesis of a chiral phosphane alkene (PAL) involves: 1) palladium‐catalyzed Suzuki coupling of 10‐bromo‐5H‐dibenzo[a,d]cyclohepten‐5‐ol (1) with phenylboronic acid to give quantitatively 10‐phenyl‐5H‐dibenzo[a,d]cyclohepten‐5‐ol (2); 2) reaction of 2 with Ph2PCl under acidic conditions to give a racemic mixture of the phosphane oxide (10‐phenyl‐5H‐dibenzo[a,d]cyclohepten‐5‐yl)diphenylphosphane oxide (PhtroppoPh, 3), which is separated into enantiomers by using high‐pressure liquid chromatography (HPLC) on a chiral column; 3) reduction with trichlorosilane to give the enantiomerically pure phosphanes (R)‐ and (S)‐(10‐phenyl‐5H‐dibenzo[a,d]cyclohepten‐5‐yl)diphenylphosphane (PhtroppPh, 4). This highly rigid, concave‐shaped ligand serves as a bidentate ligand in RhI and IrI complexes. Catalysts prepared from [Rh2(μ2‐Cl)2(C2H4)4] and (S)‐4 have allowed the efficient enantioselective 1,4‐addition of arylboronic acids to α,β‐unsaturated carbonyls (Hayashi–Miyaura reaction) (5–0.1 mol % catalyst, up to 95 % ee). The iridium complex (S,S)‐[Ir(PhtroppPh)2]OTf ((S,S)‐6; OTf=SO3CF3) has been used as a catalyst in the hydrogenation of various nonfunctionalized and functionalized olefins (turnover frequencies (TOFs) of up to 4000 h−1) and moderate enantiomeric excesses have been achieved (up to 67 % ee). [Ir(PhtroppPh)2]OTf reversibly takes up three equivalents of H2. The highly reactive octahedral [Ir(H)2(OTf)(CH2Cl2)(H2‐PhtroppPh)2] could be isolated and contains two hydrogenated monodentate H2‐PhtroppPh phosphanes, one CH2Cl2 molecule, one triflate anion, and two hydrides. Based on this structure and extensive NMR spectroscopic studies, a mechanism for the hydrogenation reactions is proposed.
Stereoelectronic Effects on Type I 1,2‐Dyotropic Rearrangements in Vicinal Dibromides
Authors: Fernández Israel , Sierra Miguel A. , Cossío Fernando P. 
Published: May 2006

AbstractThe effects of different substituents on type I‐dyotropic rearrangements of open‐chain and cyclic 1,2‐dibromo hydrocarbons have been studied by means of DFT calculations. The activation energy (Ea) of this transformation decreases with the π‐donor ability of the substituent attached to the reacting ethylenic system. This is due to donation of electronic density by conjugation or hyperconjugation. This donation leads to longer CC and CBr bond lengths in the corresponding four‐membered transition states (TSs). Linear relationships between the Ea and either the σp Hammett substituent constants and the CC bond length of the TSs were also found. In all cases, the processes have a high value of synchronicity, which is mainly independent on the substituents. A model based on the second‐order perturbational analysis for one ethylene unit with two apical bromine radicals accounts for all the computed results.
Divergent Synthesis of L‐Sugars and L‐Iminosugars from D‐Sugars
Authors: Takahashi Hideyo , Shida Tomomi , Hitomi Yuko , Iwai Yoshinori , Miyama Namisa , Nishiyama Kazusa , Sawada Daisuke , Ikegami Shiro 
Published: May 2006

AbstractAn efficient divergent synthesis of L‐sugars and L‐iminosugars from D‐sugars is described. The important intermediate, δ‐hydroxyalkoxamate, prepared from D‐glucono‐/galactono‐1,5‐lactone, was cyclized under Mitsunobu conditions to give the O‐cyclized oxime compound and the N‐cyclized lactam compound as mixtures. A more detailed investigation revealed that the appropriate protecting groups and solvents controlled the specificity for the O‐/N‐cyclization of the δ‐hydroxyalkoxamate. Suitable protection at the 6‐position of δ‐hydroxyalkoxamate, derived from D‐glucono‐1,5‐lactone, afforded the corresponding O‐alkylation product alone. Thus we succeeded in applying this to the total synthesis of L‐iduronic acid. In contrast, with both TBDMS as the protecting group and RCN as the solvent the efficient conversion of D‐glucono/galactono‐1,5‐lactone into the corresponding L‐iminosugars (L‐idonolactam and L‐altronolactam) was achieved.
Steric Effects in the Uncatalyzed and DMAP‐Catalyzed Acylation of Alcohols—Quantifying the Window of Opportunity in Kinetic Resolution Experiments
Authors: Fischer Christian B. , Xu Shangjie , Zipse Hendrik 
Published: May 2006

AbstractThe kinetics of the reaction of several alcohols (benzyl alcohol, ethanol, 1‐phenylethanol, cyclohexanol, and 1‐methyl‐1‐phenylethanol) with a selection of anhydrides (acetic anyhydride, propionic anhydride, isobutyric anhydride, isovaleric anhydride, and pivalic anhydride) as catalyzed by 4‐(N,N‐dimethylamino)pyridine (DMAP)/triethyl amine have been studied in CH2Cl2 at 20 °C. In all cases the reaction kinetics can be described by rate laws containing a DMAP‐catalyzed term and an uncatalyzed (background) term. The rate constants for the background reaction respond sensitively to changes in the steric demand of the alcohol and the anhydride substrates, making the reaction of cyclohexanol with acetic anhydride 526 times faster than the reaction with pivalic anhydride. Steric effects are even larger for the catalyzed reaction and the reactivity difference between acetic and pivalic anhydride exceeds a factor of 8000 for the reaction of cyclohexanol. There is, however, no linear correlation between the steric effects on the catalyzed and the uncatalyzed part. As a consequence there are substrate combinations with dominating catalytic terms (such as the reaction of benzyl alcohol with isobutyric anhydride), while other substrate combinations (such as the reaction of cyclohexanol with pivalic anhydride) are characterized through a dominating background process. The implications of these findings for the kinetic resolution of alcohols are discussed.
Pericyclic Transition‐State‐Like Aromaticity in the Inorganic Ions Se2I42+ and S2O42‐
Authors: Zhang Qin , Lu Xin , Huang Rong‐Bin , Zheng Lan‐Sun 
Published: May 2006

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