bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of {4‐[Bis(2‐chloroethyl)amino]phenyl}acetic Acid (Phenylacetic Acid Mustard) with 2′‐Deoxyribonucleosides
Authors: Florea‐Wang Diana , Ijäs Inna , Hakala Kristo , Mattinen Jorma , Vilpo Juhani , Hovinen Jari 
Published: March 2007

AbstractPhenylacetic acid mustard (PAM; 2), a major metabolite of the anticancer agent chlorambucil (CLB; 1), was allowed to react with 2′‐deoxyadenosine (dA), 2′‐deoxyguanosine (dG), 2′‐deoxycytidine (dC), 2′‐deoxy‐5‐methylcytidine (dMeC), and thymidine (T) at physiological pH (cacodylic acid, 50% base). The reactions were followed by HPLC and analyzed by HPLC/MS and/or 1H‐NMR techniques. Although the predominant reaction observed was hydrolysis of PAM, 2 also reacted with various heteroatoms of the nucleosides to give a series of products: compounds 5–31. PAM (2) was found to be hydrolytically slightly more stable than CLB (1). The principal reaction sites of 2 with dA, dG, and with all pyrimidine nucleosides were N(1), N(7), and N(3), resp. Also, several other adducts were detected and characterized. There was no significant difference in the reactivity of 1 and 2 with dG, dA or T, but the N(3) dC–PAM adduct was deaminated easier than the corresponding CLB derivative. The role of PAM–2′‐deoxyribonucleoside adducts on the cytotoxic and mutagenic properties of CLB (1) is discussed.
Cytotoxic Withanolides from Physalis angulata L.
Authors: He Qing‐Ping , Ma Lei , Luo Jie‐Ying , He Fu‐Yuan , Lou Li‐Guang , Hu Li‐Hong 
Published: March 2007

AbstractFour new withanolides, physagulins L–O (1–4), were isolated from the MeOH extract of the aerial parts of Physalis angulata L. (Solanaceae), together with seven known withanolides, compounds 5–11. Their structures were determined by spectroscopic techniques, including 1H‐, 13C‐NMR (DEPT), and 2D‐NMR (HMBC, HMQC, 1H,1H‐COSY, NOESY) experiments, as well as by HR‐MS. All eleven compounds were tested for their antiproliferative activities towards human colorectal‐carcinoma (HCT‐116) and human non‐small‐cell lung‐cancer (NCI‐H460) cells. Compound 5 exhibited the highest anticancer activity against the HCT‐116 cell line, with an IC50 value of 1.64±0.06 μM. Compound 9 exhibited the highest cytotoxicity towards the NCI‐H460 cell line, with an IC50 value of 0.43±0.02 μM (Table 3).
A New Cytotoxic Lanostane‐Type Triterpene Glycoside from the Sea Cucumber Holothuria impatiens
Authors: Sun Peng , Liu Bao‐Shu , Yi Yang‐Hua , Li Ling , Gui Min , Tang Hai‐Feng , Zhang Da‐Zhi , Zhang Shi‐Long 
Published: March 2007

AbstractA new lanostane‐type triterpene glycoside, impatienside A (1), was isolated from the sea cucumber Holothuria impatiens, together with a structurally related, known compound, bivittoside D (2). Their structures were elucidated by in‐depth spectroscopic and mass‐spectrometric methods, including 1H‐, 13C‐, and 2D‐NMR, ESI‐MS, and HR‐ESI‐MS experiments, as well as by chemical evidence. Compounds 1 and 2 possess the same hexasaccharide moieties, but differ slightly in their holostane‐type triterpene aglycone. The two glycosides were found to exhibit in vitro cytotoxicities similar to or better than those of the potent anticancer drug etoposide (V‐16) against seven different human tumor cells, with IC50 values of 0.37–2.75 μg/ml.
Synthesis and Analgesic Activities of Endomorphin‐2 and Its Analogues
Authors: Shi Zhi‐Hao , Wei Yun‐Yang , Wang Chuan‐Jin , Yu Li 
Published: March 2007

AbstractEndomorphin‐2 (1; H‐Tyr‐Pro‐Phe‐Phe‐NH2; EM2) and its novel cyclic asparagine (cycloAsn) analogues, H‐Tyr‐cAsn(CHPh)‐Phe‐Phe‐NH2 (2) and H‐Tyr‐cAsn(CHMe2)‐Phe‐Phe‐NH2 (3), were synthesized via liquid‐phase synthesis. The structures of the products and intermediates were characterized by IR, 1H‐NMR, MS, and HR‐MS analyses. The antinociceptive activity of EM2 and its cyclic asparagine analogues were assessed in AcOH‐induced abdominal constriction tests in mice with i.p. injection. The results show that the antinociceptive activities of EM2 and its cyclic asparagine analogue 2 were higher than those of aspirine and meperidine. Analogue 2 was observed to be a stronger analgesic with dose‐dependence than EM2. The test mice did not show any tendency to be addicted while administrated of analogue 2 repeatedly and regularly.
Chemical and Genetic Differentiation of Ligularia tsangchanensis in Yunnan and Sichuan Provinces of China
Authors: Torihata Atsushi , Hanai Ryo , Gong Xun , Shen Yuemao , Kuroda Chiaki 
Published: March 2007

AbstractThe intraspecific diversity in L. tsangchanensis collected in the Chinese Provinces Yunnan and southwestern Sichuan was studied by chemical and genetic approaches. The samples collected in Yunnan were found to contain cacalol (1) as the sole major component, while samples from Sichuan contained 7α‐ and 7β‐eremophila‐9,11‐dien‐8‐one (5 and 6) as well as the 3α‐angeloyloxy derivative 7 as major components. In addition, the sequences of the internal transcribed spacers (ITSs) of the ribosomal RNA gene indicated that the Yunnan and the Sichuan samples constitute separate clades. These results demonstrate that L. tsangchanensis in Yunnan and Sichuan are distinct.
Novel Alkaloids from the Roots of Stemona sessilifolia
Authors: Wang Peng , Liu Ai‐Lin , An Zheng , Li Zhi‐Hong , Du Guan‐Hua , Qin Hai‐Lin 
Published: March 2007

AbstractFour new Stemona alkaloids, sessilistemonamines A–C (1–3, resp.) and dihydrostemoninine (4), were isolated from the roots of Stemona sessilifolia. Their structures and relative configurations were elucidated by means of in‐depth 1D‐ and 2D‐NMR‐spectroscopic as well as mass‐spectrometric experiments; and the structure of 4 was solved by X‐ray single‐crystal diffraction. The stereoisomeric compounds 1–3 share an unprecedented tetracyclic decahydro‐1H‐furo[2′,3′:4,5]cyclopenta[1,2‐b]pyrrolo[1,2‐a]azepine nucleus. Compounds 1 and 2 were found to be moderately active in terms of acetylcholinesterase (AchE) inhibition, with IC50 values of 68.8±9.5 and 17.1±2.5 μM, resp.
Functional [6]Pericyclynes: Aromatization to Substituted carbo‐Benzenes
Authors: Saccavini Catherine , Sui‐Seng Christine , Maurette Luc , Lepetit Christine , Soula Sabine , Zou Chunhai , Donnadieu Bruno , Chauvin Remi 
Published: March 2007

AbstractReductive treatment of stereoisomeric mixtures of variously substituted hexaoxy[6]pericyclynes with SnCl2/HCl led to the corresponding substituted carbo‐benzenes. Tetramethoxyhexaphenyl[6]pericylynediol and dimethoxyhexaphenyl[6]pericyclynetetrol thus proved to be alternative precursors of hexaphenyl‐carbo‐benzene, previously described. Another hexaaryl‐carbo‐benzenic chromophore with 4‐pyridyl and 4‐anisyl substituents was targeted for its second‐order nonlinear optical properties and was obtained by aromatization of a dimethoxy[6]pericyclynetetrol. Two alkynyl substituents in para positions were also found to be compatible with the C18 carbo‐benzene ring, provided that the four remaining vertices are substituted by phenyl groups. In the protected series, bis(trimethylsilylethynyl)hexaphenyl‐carbo‐benzene (C18Ph4(CCTMS)2) could be isolated and fully characterized, even by X‐ray crystallography. In the bis‐terminal series, the diethynylhexaphenyl‐carbo‐benzene C18Ph4(CCH)2 could not be isolated in the pure form. It could, however, be generated by two different methods and identified by the corresponding 1H NMR spectra. Unsubstituted carbo‐benzene C18H6 remains unknown, but tetraphenyl‐carbo‐benzenes C18Ph4H2 with two unsubstituted vertices proved to be viable molecules. Whereas the “para” isomer could be characterized by MS and 1H and 13C NMR spectroscopy only in a mixture with polymeric materials, the “ortho” isomer (with adjacent CH vertices) could be isolated, and its structure was determined by using X‐ray crystallography. The structure calculated at the B3PW91/6‐31G** level of theory turned out to be in excellent agreement with the experimental structure. The 1H and 13C NMR chemical shifts of hexa‐ and tetraphenyl‐carbo‐benzenes were also calculated at the B3LYP/6‐31+G** level of theory and were found to correlate with experimental spectra. The remote NMR deshielding of peripheral protons (through up to five bonds) revealed a very strong diatropic circulation around the C18 ring, regardless of the substitution pattern. In full agreement with theoretical investigations, it has been demonstrated experimentally that the carbo‐benzene ring is “independently” aromatic, in accord with structural–energetic and –magnetic criteria.
Silver versus Gold Catalysis in Tandem Reactions of Carbonyl Functions onto Alkynes: A Versatile Access to Furoquinoline and Pyranoquinoline Cores
Authors: Godet Thomas , Vaxelaire Carine , Michel Carine , Milet Anne , Belmont Philippe 
Published: March 2007

AbstractAn efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1‐alkynyl‐2‐carbonylquinoline substrates. The reaction occurs thanks to AuI and AgI catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT‐B3 LYP/6–31G** calculations to address the 6‐endo and 5‐exo regioselectivities observed.
Highly Potent Fluorescence‐Tagged Nonimidazole Histamine H3 Receptor Ligands
Authors: Amon Michael , Ligneau Xavier , Camelin Jean‐Claude , Berrebi‐Bertrand Isabelle , Schwartz Jean‐Charles , Stark Holger 
Published: March 2007

AbstractDifferent (3‐phenoxypropyl)piperidine derivatives have been coupled to fluorescent moieties (5‐dimethylaminonaphthalene‐1‐sulfonyl, carbazol‐9‐ylcarbonyl, 2‐cyanoisoindol‐1‐yl, 2‐cyanobenzo[f]isoindol‐1‐yl, 2,4‐dinitrobenzen‐1‐yl, 2,4‐diaminophenyl, 7‐nitrobenzofurazan‐4‐yl, 7‐aminosulfonylbenzofurazan‐4‐yl, 4‐methylcoumarin‐6‐yl) as novel histamine H3 receptor ligands. They have been synthesised starting from piperidine in a few steps. The compounds display good to excellent histamine hH3 receptor affinities with Ki values ranging from 13.4 to 0.048 nM. Some of the new compounds belong to the most potent ligands known so far and may act as tools for identification and understanding of the binding site on the histamine H3 receptor. In vivo screening on selected derivatives of Sanger’s reagent showed antagonist potencies with ED50 values from 7.9 to 0.39 mg kg−1, p.o.
Velocity averaging, kinetic formulations, and regularizing effects in quasi‐linear PDEs
Authors: Tadmor Eitan , Tao Terence 
Published: March 2007

AbstractWe prove in this paper new velocity‐averaging results for second‐order multidimensional equations of the general form ℒ︁(∇x,v)f(x, v) =g(x, v) where ℒ︁(∇x,v) :=a(v) · ∇x− ∇·b(v)∇x. These results quantify the Sobolev regularity of the averages, ∫vf(x, v)ϕ(v)dv, in terms of the nondegeneracy of the set {v: |ℒ︁(iξ,v)| ≤ δ} and the mere integrability of the data, (f, g) ∈ (L,L). Velocity averaging is then used to study theregularizing effectin quasi‐linear second‐order equations, ℒ︁(∇x, ρ)ρ =S(ρ), which use their underlying kinetic formulations, ℒ︁(∇x, v)χρ=gS. In particular, we improve previous regularity statements for nonlinear conservation laws, and we derive completely new regularity results for convection‐diffusion and elliptic equations driven by degenerate, nonisotropic diffusion. © 2007 Wiley Periodicals, Inc.
Computing the 1H NMR Spectrum of a Bulk Ionic Liquid from Snapshots of Car–Parrinello Molecular Dynamics Simulations
Authors: Bagno Alessandro , D'Amico Fabio , Saielli Giacomo 
Published: March 2007

AbstractWe have investigated the performance of several computational protocols in predicting the NMR spectrum of a molecular ion in a complex liquid phase such as an ionic liquid. To do this, we computed the proton NMR chemical shifts of the 1‐ethyl‐3‐methylimidazolium cation [emim]+ in [emim][Cl]. Environmental effects on the imidazolium ring proton chemical shifts are quite significant and must be taken into account explicitly. Calculations performed on the isolated imidazolium cation as well as on the [emim][Cl] ion pair grossly fail to reproduce the correct spacing between proton signals. In contrast, calculations performed on clusters extracted from the trajectory of a Car–Parrinello molecular dynamics simulation yield very good results.
Ethanol Adsorption, Decomposition and Oxidation on Ir(111): A High Resolution XPS Study
Authors: Weststrate Cornelis J. , Ludwig Wiebke , Bakker Johan W. , Gluhoi Andreea C. , Nieuwenhuys Bernard E. 
Published: March 2007

AbstractEthanol (C2H5OH) adsorption, decomposition and oxidation is studied on Ir(111) using high‐energy resolution, fast XPS and temperature‐programmed desorption. During heating of an adsorbed ethanol layer a part of the C2H5OHad desorbs molecularly, and another part remains on the surface and decomposes around 200 K; these two decomposition pathways are identified, as via acetyl (H3CCO) and via COad+CH3ad, respectively. Acetyl and CH3ad decompose around 300 K into CHad (and COad). CHad decomposes forming Cx and H2 around 520 K. In the presence of Oad an acetate intermediate is formed around 180 K, as well as a small amount of CH3ad and COad. Acetate decomposes between 400–480 K into CO2, H2(/H2O) and CHad.
Data quality assessment of ungated flow cytometry data in high throughput experiments
Authors: Le Meur Nolwenn , Rossini Anthony , Gasparetto Maura , Smith Clay , Brinkman Ryan R. , Gentleman Robert 
Published: March 2007

AbstractBackground:The recent development of semiautomated techniques for staining and analyzing flow cytometry samples has presented new challenges. Quality control and quality assessment are critical when developing new high throughput technologies and their associated information services. Our experience suggests that significant bottlenecks remain in the development of high throughput flow cytometry methods for data analysis and display. Especially, data quality control and quality assessment are crucial steps in processing and analyzing high throughput flow cytometry data.Methods:We propose a variety of graphical exploratory data analytic tools for exploring ungated flow cytometry data. We have implemented a number of specialized functions and methods in the Bioconductor package rflowcyt. We demonstrate the use of these approaches by investigating two independent sets of high throughput flow cytometry data.Results:We found that graphical representations can reveal substantial nonbiological differences in samples. Empirical Cumulative Distribution Function and summary scatterplots were especially useful in the rapid identification of problems not identified by manual review.Conclusions:Graphical exploratory data analytic tools are quick and useful means of assessing data quality. We propose that the described visualizations should be used as quality assessment tools and where possible, be used for quality control. © 2007 International Society for Analytical Cytology
Analysis of nitrosamines by capillary electrospray‐high‐field asymmetric waveform ion mobility spectrometry‐MS with programmed compensation voltage
Authors: Liu Xin , Zhao Yuan‐Yuan , Chan Kenneth , Hrudey Steve E. , Li Xing‐Fang , Li Jianjun 
Published: March 2007

AbstractEmerging disinfection by‐products (DBPs) in drinking water are an important public health concern. Certain DBPs, such as nitrosamines, are probable carcinogens, and exposure to halogenated DBPs may lead to birth defects. It is difficult to obtain complete separation of nitrosamines by chromatographic techniques. Thus we explored high‐field asymmetric waveform ion mobility spectrometry (FAIMS) as an alternative separation technique for the characterization of individual DBPs in a complex matrix. We first used ESI‐FAIMS‐MS to separate four nitrosamines: N‐nitrosodi‐n‐butylamine (NDBA), N‐nitrosodi‐n‐propylamine (NDPA), N‐nitrosopiperidine (NPip), and N‐nitrosodiethylamine (NDEA) in the compensation voltage (CV) spectra. The optimal CVs with a fixed dispersion voltage of –4000 V were found to be –1.2 V (NDBA), 2.7 V (NDPA), 7.5 V (NPip) and 10.1 V (NDEA). In addition, FAIMS‐MS effectively reduced the chemical noise and dramatically improved the LODs by as much as tenfold compared to the conventional ESI‐MS technique. To further improve sensitivity, an on‐line CE system was used in combination with FAIMS‐MS to take advantage of the higher ionization efficiency. The calibration curves for the four nitrosamines were linear over a range of 5 ng/mL to 1000 ng/mL with an r2 value of 0.9929 to 0.9992. To increase sample throughput, a multiple‐injection strategy was developed, in which the CV values were preprogrammed so that the FAIMS device allowed different nitrosamines to pass through at selected time windows. The potential application of the proposed method was demonstrated for the analysis of drinking water samples spiked with nitrosamines.
Environmental pollution analysis by dynamic structural equation models
Authors: Fontanella Lara , Ippoliti Luigi , Valentini Pasquale 
Published: March 2007

AbstractAs requested by the framework EU Directive on air quality assessment and management (96/62/EC) and related ‘daughter’ directives, air quality standards for specific pollutants are designed to protect public health and environment. Modeling is one of the main activities to evaluate air quality and to prepare future control programs. Of course, this is not an easy task since a variety of pollutants may undergo chemical reactions between themselves and with other species. Nevertheless, in this paper we attempt to discuss a framework to construct a multivariate model which is able to capture the dynamical interactions among pollutants and meteorological variables. Specifically, assuming that latent or background effects underlying the fluctuation of observations can be estimated, a dynamic structural equation model is developed in a state‐space form. A research study on the Milan district for data provided by the Lombardia Environmental Protection Agency (ARPA) is presented. Copyright © 2007 John Wiley & Sons, Ltd.
Clustering composition vectors using uncertainty information
Authors: Christensen William F. , Dillner Ann M. , Schauer James J. , Reese C. Shane 
Published: March 2007

AbstractIn the biological and environmental sciences, interest often lies in using multivariate observations to discover natural clusters of objects. In this manuscript, the incorporation of measurement uncertainty information into a cluster analysis is discussed. This study is motivated by a problem involving the clustering of composition vectors associated with each of several chemical species. The observed abundance of each component is available along with its estimated uncertainty (measurement error standard deviation). An approach is proposed for converting the abundance vectors into composition (relative abundance) vectors, obtaining the covariance matrix associated with each composition vector, and defining a Mahalanobis distance between composition vectors that are suitable for cluster analysis. The approach is illustrated using particle size distributions obtained near Houston, Texas in 2000. Computer simulation is used to compare the performance of Mahalanobis‐distance‐based and Euclidean‐distance‐based clustering approaches. The use of a modified Mahalanobis distance along with Ward's method is recommended for use. Copyright © 2007 John Wiley & Sons, Ltd.
Nonlinear dynamic analysis of complex structures
Authors: Wilson E. L. , Farhoomand I. , Bathe K. J. 
Published: March 2007

AbstractA general step‐by‐step solution technique is presented for the evaluation of the dynamic response of structural systems with physical and geometrical nonlinearities. The algorithm is stable for all time increments and in the analysis of linear systems introduces a predictable amount of error for a specified time step. Guidelines are given for the selection of the time step size for different types of dynamic loadings. The method can be applied to the static and dynamic analysis of both discrete structural systems and continuous solids idealized as an assemblage of finite elements. Results of several nonlinear analyses are presented and compared with results obtained by other methods and from experiments.
A stochastic model for predicting seismic failure in a soil deposit
Authors: Faccioli Ezio 
Published: March 2007

AbstractLiquefaction of saturated sand deposits under seismic excitation is studied on the basis of a fatigue failure approach. The model includes a stochastic treatment of the input, of the soil response and of the cumulative pore pressure effects produced by cycling stresses in the soil. A method of establishing safety factors against liquefaction is also considered. Results obtained from analysis of a case history confirm the applicability of the model for engineering purposes.
Stochastic excitation of a simple system with impact damper
Authors: Masri S. F. , Ibrahim A. M. 
Published: March 2007

AbstractAn approximate analytical solution is obtained for the stationary response of a highly nonlinear auxiliary mass damper (impact damper) attached to a single‐degree‐of‐freedom oscillator that is subjected to an excitation with white power spectral density and Gaussian probability distribution. Experimental measurements with an electronic analogue computer verify the analytical findings both qualitatively and quantitatively. Results are given for the mean‐squared level and the power spectral density of the response. The effects of various damper parameters on the response of the primary system are determined. The impact damper under consideration is shown to be substantially more effective than the conventional dynamic vibration neutralizer in controlling the response of stochastically excited primary systems.
Effects of stiffness degradation on ductility requirements for multistorey buildings
Authors: Chopra Anil K. , Kan Christopher 
Published: March 2007

AbstractThe effect of stiffness degradation in reinforced concrete structural members on the inelastic response of multistorey buildings to earthquakes is investigated. In particular, the following question is examined. How do the ductility requirements for multistorey systems with degrading stiffness behaviour compare with those for structures with ordinary bilinear hysteretic property? Inelastic dynamic responses of two idealized multistorey buildings, one having a long and the other a relatively short fundamental period, to an ensemble of twenty simulated earthquakes representative of moderately intense ground motions in California at moderate epicentral distances on firm ground, are analysed for ordinary bilinear hysteretic behaviour and for bilinear hysteretic behaviour with stiffness degradation property. The conclusions deduced from the results of this investigation include the following(1) It is, in general, not possible to predict the maximum response of a degrading stiffness system from results for the corresponding ordinary bilinear system(2) The differences in ductility requirements due to stiffness degradation are generally smaller than those associated with probabilistic variability from one ground motion to another(3) Stiffness degradation has little influence on the ductility requirements for flexible buildings, but it leads to increased ductility requirements for stiff buildings.