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Sample records for intramolecular em trans-2-clorocicloexanol

  1. Intramolecular and nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.J. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Research in this program focuses on three interconnected areas. The first involves the study of intramolecular dynamics, particularly of highly excited systems. The second area involves the use of nonlinear dynamics as a tool for the study of molecular dynamics and complex kinetics. The third area is the study of the classical/quantum correspondence for highly excited systems, particularly systems exhibiting classical chaos.

  2. Symmetry of intramolecular quantum dynamics

    CERN Document Server

    Burenin, Alexander V

    2012-01-01

    The main goal of this book is to give a systematic description of intramolecular quantum dynamics on the basis of only the symmetry principles. In this respect, the book has no analogs in the world literature. The obtained models lead to a simple, purely algebraic, scheme of calculation and are rigorous in the sense that their correctness is limited only to the correct choice of symmetry of the internal dynamics. The book is basically intended for scientists working in the field of molecular spectroscopy, quantum and structural chemistry.

  3. Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond

    Indian Academy of Sciences (India)

    Ultrafast Dynamics of Chemical Reactions in Condensed Phase: Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond. Dipak K. Palit Radaition & Photochemistry Division Bhabha Atomic Research Centre Mumbai 400 085, India.

  4. Intramolecular Association within the SAFT Framework

    DEFF Research Database (Denmark)

    Avlund, Ane Søgaard; Kontogeorgis, Georgios; Chapman, Walter G.

    2011-01-01

    the contribution to the Helmholtz free energy from association (inter- as well as intramolecularly) at equilibrium. Sear and Jackson rederived the contribution to the Helmholtz free energy from association from the theory by Wertheim [J. Stat. Phys. 42 (3–4), 459 (1986)] with inclusion of intramolecular...... association, and using this approach we obtain an expression for the Helmholtz free energy that is valid also at non-equilibrium states (with respect to hydrogen bonds), which is very useful when calculating derivatives.......A general theory for modelling intramolecular association within the SAFT framework is proposed. Sear and Jackson [Phys. Rev. E. 50 (1), 386 (1994)] and Ghonasgi and Chapman [J. Chem. Phys. 102 (6), 2585 (1995)] have previously extended SAFT to include intramolecular association for chains with two...

  5. Structural, intramolecular hydrogen bonding and vibrational studies ...

    Indian Academy of Sciences (India)

    The harmonic oscillator model of aromaticity (HOMA) index elucidated the impact of hydrogen bond- ing in the ring. Intramolecular hydrogen bonding energy has been calculated from topological study. The low wavenumber vibrational modes obtained from experimental FT-Raman spectrum also supported the presence.

  6. Solvent control of intramolecular proton transfer

    DEFF Research Database (Denmark)

    Manolova, Y.; Marciniak, Heinz; Tschierlei, S.

    2017-01-01

    of molecules in the enol and zwitterionic proton transfer (PT) form exists in the ground state. However, the zwitterion is the energetically favored one in the electronically excited state. Optical excitation of the enol form results in intramolecular proton transfer and formation of the PT form within 1.4 ps...

  7. Structural, intramolecular hydrogen bonding and vibrational studies ...

    Indian Academy of Sciences (India)

    An extensive theoretical study on the molecular structure and vibrational analysis of 3-amino-4- methoxy benzamide (3A4MBA) was undertaken using density functional theoretical (DFT) method. The possibility of formation of intramolecular hydrogen bonding was identified from structural parameter analysis and confirmed ...

  8. Structural, intramolecular hydrogen bonding and vibrational studies

    Indian Academy of Sciences (India)

    An extensive theoretical study on the molecular structure and vibrational analysis of 3-amino-4- methoxy benzamide (3A4MBA) was undertaken using density functional theoretical (DFT) method. The possibility of formation of intramolecular hydrogen bonding was identified from structural parameter analysis and confirmed ...

  9. Photoswitchable Intramolecular H-Stacking of Perylenebisimide

    NARCIS (Netherlands)

    Wang, Jiaobing; Kulago, Artem; Browne, Wesley R.; Feringa, Ben L.

    2010-01-01

    Dynamic control over the formation of H- or J-type aggregates of chromophores is of fundamental importance for developing responsive organic optoelectronic materials. In this study, the first example of photoswitching between a nonstacked and an intramolecularly H-stacked arrangement of

  10. Structural, intramolecular hydrogen bonding and vibrational studies ...

    Indian Academy of Sciences (India)

    The harmonic oscillator model of aromaticity (HOMA) index elucidated the impact of hydrogen bond- ing in the ring. Intramolecular hydrogen ... (Figure 3). The total ener- gies obtained for these possible conformers are listed in Table 1. ..... Structure, Reactivity and Intermolecular Forces: An. Euristic Interpretation by Means of ...

  11. Intramolecular and Transannular Diels-Alder Reactions

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Ascic, Erhad

    2014-01-01

    Few reactions can compete with the Diels-Alder (DA) [4+2] cycloaddition for the rapid and efficient generation of molecular complexity. The DA reaction is atom-economic and stereospecific, as well as diastereo- and regioselective. The intramolecular version (IMDA) of the DA cycloaddition and its...... and dienophile, methods for acceleration of IMDA reactions (such as use of high pressure) and catalysis (using oxophilic or carbophilic metal complexes, Brønsted acids, and enzymes). The use of furans as diene components (IMDAF), intramolecular hetero-DA (IMHDA) and IMDA reactions with inverse electron demand...... are also covered. Applications of IMDA to asymmetric synthesis (from substrate control through to enantioselective catalysis, including organocatalysis) are presented, along with tandem sequences involving IMDA cycloaddition. A theme pervading the whole chapter is the use of IMDA reactions for the total...

  12. Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond

    Indian Academy of Sciences (India)

    Ultrafast Dynamics of Chemical Reactions in Condensed Phase: Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond · PowerPoint Presentation · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19.

  13. Intramolecular Energy Relaxation and Statistical Rate Theory

    OpenAIRE

    Okitsugu, KAJIMOTO; Department of Chemistry, Kyoto University

    1994-01-01

    Statistical rate theory is essentially based on the state counting without any restrictions other than the energy and the angular momentum conservation. In this work, two kinds of restrictions are introduced into the statistical theory. The first restriction is related to the intramolecular energy flow within the reacting molecular system. The excess energy of reaction is made distributed with some bias favoring a specific degree of freedom. That is, the statistical weight of each product sta...

  14. Ciclização intramolecular de 2-(w-Bromoalquiloxi) anilinas /

    OpenAIRE

    Martendal, Adriano

    1999-01-01

    Dissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Ciclizações intramoleculares podem ser estudadas como modelos miméticos de catálise enzimática. Esses modelos fundamentam-se no princípio de que os parâmetros físico-químicos que governam a reatividade entre dois grupamentos funcionais em uma reação intramolecular, estejam presentes também no mecanismo da ação enzimática. Os brometos de 2-(w-bromoalquiloxi)anilínio e 2-(w-bromoalquilo...

  15. Intramolecular Barbier reaction in water: cyclopentane and cyclohexane ring closure

    Directory of Open Access Journals (Sweden)

    RADOMIR N. SAICIC

    2002-03-01

    Full Text Available Zinc or indium promoted intramolecular Barbier reactions of aldehydes containing a suitably positioned allylic or propargylic halide unit afford unsaturated cyclic alcohols in moderate yields.

  16. Excited state Intramolecular Proton Transfer in Anthralin

    DEFF Research Database (Denmark)

    Møller, Søren; Andersen, Kristine B.; Spanget-Larsen, Jens

    1998-01-01

    Quantum chemical calculations performed on anthralin (1,8-dihydroxy-9(10H)-anthracenone) predict the possibility of an excited-state intramolecular proton transfer process. Fluorescence excitation and emission spectra of the compound dissolved in n-hexane at ambient temperature results...... in an unusually large fluorescence Stokes shift of 10500 cm−1. The emission appears as a broad band with a maximum at 17500 cm−1 and is characterized by a low and nearly temperature-independent quantum yield. The results are interpreted as an indication of a large equilibrium geometry change upon excitation...

  17. Femtosecond laser studies of ultrafast intramolecular processes

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, C. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

    The goal of this research is to better understand the detailed mechanisms of chemical reactions by observing, directly in time, the dynamics of fundamental chemical processes. In this work femtosecond laser pulses are used to initiate chemical processes and follow the progress of these processes in time. The authors are currently studying ultrafast internal conversion and subsequent intramolecular relaxation in unsaturated hydrocarbons. In addition, the authors are developing nonlinear optical techniques to prepare and monitor the time evolution of specific vibrational motions in ground electronic state molecules.

  18. Intramolecular energy transfer reactions in polymetallic

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, J.

    1990-11-01

    This report is concerned with intramolecular, energy-transfer reactions. The concept of preparing synthetically a complex molecular species, capable of absorbing a photon at one metal center (antenna fragment), transferring that energy to a second metal center (reactive fragment) via a bridging ligand was first reported by our group in 1979. It is now apparent that a major emphasis in inorganic chemistry in the future will involve these types of molecular ensembles. Complexes discussed include Rh, Ru, and Cu complexes. 23 refs., 14 tabs.

  19. Influence of Intramolecular Charge Transfer and Nuclear Quantum Effects on Intramolecular Hydrogen Bonds in Azopyrimidines.

    Science.gov (United States)

    Bártová, Kateřina; Čechová, Lucie; Procházková, Eliška; Socha, Ondřej; Janeba, Zlatko; Dračínský, Martin

    2017-10-06

    Intramolecular hydrogen bonds (IMHBs) in 5-azopyrimidines are investigated by NMR spectroscopy and DFT computations that involve nuclear quantum effects. A series of substituted 5-phenylazopyrimidines with one or two hydrogen bond donors able to form IMHBs with the azo group is prepared by azo coupling. The barrier of interconversion between two rotamers of the compounds with two possible IMHBs is determined by variable temperature NMR spectroscopy and it is demonstrated that the barrier is significantly affected by intramolecular charge transfer. Through-hydrogen-bond scalar coupling is investigated in 15 N labeled compounds and the stability of the IMHBs is correlated with experimental NMR parameters and rationalized by path integral molecular dynamics simulations that involve nuclear quantum effects. Detailed information on the hydrogen bond geometry upon hydrogen-to-deuterium isotope exchange is obtained from a comparison of experimental and calculated NMR data.

  20. Fluorescence and Intramolecular Energy Transfer in Polyphenylene Dendrimers

    NARCIS (Netherlands)

    Liu, Daojun; Feyter, Steven De; Cotlet, Mircea; Stefan, Alina; Wiesler, Uwe-Martin; Herrmann, Andreas; Grebel-Koehler, Dörthe; Qu, Jianqiang; Müllen, Klaus; Schryver, Frans C. De

    2003-01-01

    The fluorescence of polyphenylene dendrimers and the intramolecular energy transfer in polyphenylene dendrimers containing a perylenediimide core have been investigated in this paper. Polyphenylene dendrimers composed of tens or hundreds of out-of-plane twisted phenyl units exhibit strong

  1. Intramolecularly Hydrogen-Bonded Polypyrroles as Electro-Optical Sensors

    National Research Council Canada - National Science Library

    Nicholson, Jesse

    2001-01-01

    We have developed a new class of polypyrroles bearing both hydrogen-bond acceptor and hydrogen-donor groups such that the intramolecular hydrogen bonding holds the system planar enhancing conjugation...

  2. Evaluation of intramolecular charge transfer state of 4-N, N ...

    Indian Academy of Sciences (India)

    intermediate charge transfer (TICT) model.2 Evidence suggests that the intramolecular TICT process from a donor to an acceptor could be achieved by a twist- ing motion of the donor moiety that promotes initially generated locally excited (LE) state to an energeti- cally relaxed charge transfer state (CT).2–6,8,13 Besides.

  3. Excited state intramolecular charge transfer reaction in 4-(1 ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several.

  4. Excited state intramolecular charge transfer reaction of 4 ...

    Indian Academy of Sciences (India)

    An intramolecular charge transfer (ICT) molecule with an extra hetero atom in its donor moiety has been synthesized in order to investigate how ICT reaction is affected by hetero atom replacement. Photo-physical and photo-dynamical properties of this molecule, 4-(morpholenyl)benzonitrile (M6C), have been studied in 20 ...

  5. Preparation of CN x /Carbon Nanotube Intramolecular Junctions by ...

    African Journals Online (AJOL)

    Preparation of CN x /Carbon Nanotube Intramolecular Junctions by Switching Gas Sources in Continuous Chemical Vapour Deposition. ... nanotubes were observed, and such different structures at both sides of the junctions indicated some interesting properties and offered potential applications for future nanodevices.

  6. and Di-hydration on the Intramolecular Proton Transfers and ...

    Indian Academy of Sciences (India)

    of the isomers did not change the stability trend, so that the tri-keto isomer was the most stable isomer among the hydrated and non-hydrated isomers. The activation energies (Ea) of the intramolecular proton transfers. (tautomerisms) and energy barriers of H-rotations around its C-O axis in enolic isomers were calculated.

  7. The intramolecular electron transfer between copper sites of nitrite reductase

    DEFF Research Database (Denmark)

    Farver, O; Eady, R R; Abraham, Z H

    1998-01-01

    The intramolecular electron transfer (ET) between the type 1 Cu(I) and the type 2 Cu(II) sites of Alcaligenes xylosoxidans dissimilatory nitrite reductase (AxNiR) has been studied in order to compare it with the analogous process taking place in ascorbate oxidase (AO). This internal process is in...

  8. Excited state intramolecular charge transfer reaction in 4-(1 ...

    Indian Academy of Sciences (India)

    Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several other ...

  9. Effects of acid concentration on intramolecular charge transfer ...

    Indian Academy of Sciences (India)

    of P4C molecule.7 Temperature-assisted aggregation of alcohol has also been observed by following the fluo- rescence response of the same solute.20 Electrolyte- induced modulation of intramolecular charge transfer rate of P4C molecule in pure solvent has been explored and a non-monotonic dependence observed.18.

  10. Excited state intramolecular proton transfer in some tautomeric azo dyes and Schiff bases containing an intramolecular hydrogen bond

    NARCIS (Netherlands)

    Joshi, H.C.; Kamounah, F.S.; Gooijer, C.; van der Zwan, G.; Antonov, L.

    2002-01-01

    Photophysical properties of several basically important aromatic azodyes (1-phenylazo-2-naphthol and 2-phenylazo-1-naphthol) and Schiff bases (N-(2-hydroxy-1-naphthylmethylidene) aniline and N-(1-hydroxy-2-naphthylmethylidene) aniline) all containing an intramolecular hydrogen bond were studied by

  11. Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

    KAUST Repository

    Vummaleti, Sai V. C.

    2015-11-13

    Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

  12. Structure and Intramolecular Proton Transfer of Alanine Radical Cations

    International Nuclear Information System (INIS)

    Lee, Gab Yong

    2012-01-01

    The structures of the four lowest alanine conformers, along with their radical cations and the effect of ionization on the intramolecular proton transfer process, are studied using the density functional theory and MP2 method. The energy order of the radical cations of alanine differs from that of the corresponding neutral conformers due to changes in the basicity of the NH 2 group upon ionization. Ionization favors the intramolecular proton transfer process, leading to a proton-transferred radical-cation structure, [NH 3 + -CHCH 3 -COO·], which contrasts with the fact that a proton-transferred zwitterionic conformer is not stable for a neutral alanine in the gas phase. The energy barrier during the proton transfer process is calculated to be about 6 kcal/mol

  13. Specific Features of Intramolecular Proton Transfer Reaction in Schiff Bases

    Directory of Open Access Journals (Sweden)

    Aleksander Koll

    2003-06-01

    Full Text Available Abstract: The differences between the intramolecular proton transfer in Mannich and Schiff bases are discussed. The tautomeric forms being in equilibrium in both types of molecules are seriously different. In Mannich bases there are in equilibrium the forms of phenols and phenolates. In Schiff bases each of tautomers is strongly influenced by resonance between zwitterionic and keto structures. Despite the common opinion that the proton transfer forms in compounds with internal π-electronic coupling are mainly keto forms it is shown in this work, that in Schiff bases the content of keto structure is slightly less than zwitterionic one. Almost equal participation of both forms leads to effective resonance between them and stabilization of intramolecular hydrogen bond in this way.

  14. Intramolecular hydrogen bonding and tautomerism in Schiff bases ...

    Indian Academy of Sciences (India)

    N and keto-amine, O…H-N forms) in this series. The molecular structure of 8 has been determined crystallographically, and observed that the compound is in the form of phenol-imine, defined by the strong intramolecular [O-H…N = 1.72(3), 1.81(2) Å] hydrogen bonds. Compound 8 crystallizes in the monoclinic space group ...

  15. Application to processing system using intra-molecular BRET

    Science.gov (United States)

    Otsuji, Tomomi; Okuda-Ashitaka, Emiko; Kojima, Satoshi; Akiyama, Hidehumi; Ito, Seiji; Ohmiya, Yoshihiro

    2003-07-01

    Luciferases are used as the reporter gene for promoter activity, whereas a green fluorescent protein (GFP) is used as marker for cellular function and localization. Recently, bioluminescence resonance energy transfer (BRET) between luciferase and YFP is used for analysis of inter-molecular reaction such as ligand-receptor in the living cells. The neuropeptides nocistatin (NST) and nociceptin/orphanin FQ (Noc/OFQ) are derived from the same precursor protein, while NST exhibits antagonism against Noc/OFQ-actions. In this study, we attempt an intra-molecular BRET system for monitoring dynamic biological process of the production of NST and Noc/OFQ in the living cells. At first, we constructed a fusion protein (Rluc-GFP) covalently linking luciferase (Renilla luciferase; Rluc) to Aequorea GFP as an intra-molecular BRET partner. Furthermore, we inserted constructs of mouse NST and Noc/OFQ (Rluc-m-GFP) or bovine NST and Noc/OFQ (Rluc-b-GFP) containing a proteolytic cleavage motif (Lys-Arg) within Rluc-GFP. When these constructions were transfected into Cos7 cells, all fusion proteins had luciferase activity and specific fluorescence. Luminescence spectra of Rluc-GFP, Rluc-m-GFP and Rluc-b-GFP fusion proteins with DeepBlueC as a substrate showed two peaks centered at 400 nm and 510 nm, whereas Rluc showed one peak centered at 400 nm. These results indicate that the proteolytic cleavage motif inserted fusion proteins between luciferase and GFP are available for intra-molecular BRET systems at first step.

  16. Intramolecular Hydrogen Bonding in (2-Hydroxybenzoyl)benzoylmethane Enol

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Winther, Morten; Spanget-Larsen, Jens

    2014-01-01

    , and the dienol form of 1,3-dibenzoylacetone. But in these examples the two H-bonds are equivalent, while in the case of OHDBM they are chemically different, involving one enolic and one phenolic hydroxy group. OHDBM is thus an interesting model compound with two competing H-bonds to the same carbonyl group......In the stable enol tautomer of the title compound (OHDBM), one carbonyl group is flanked by two β-hydroxy groups, giving rise to bifold intramolecular H-bonding. A similar situation is found in other β,β'-dihydroxy carbonyl compounds like chrysazin, anthralin, 2,2'-dihydroxybenzophenone...

  17. Recording Intramolecular Mechanics during the Manipulation of a Large Molecule

    Energy Technology Data Exchange (ETDEWEB)

    Moresco, Francesca; Meyer, Gerhard; Rieder, Karl-Heinz; Tang, Hao; Gourdon, Andre; Joachim, Christian

    2001-08-20

    The technique of single atom manipulation by means of the scanning tunneling microscope (STM) applies to the controlled displacement of large molecules. By a combined experimental and theoretical work, we show that in a constant height mode of manipulation the STM current intensity carries detailed information on the internal mechanics of the molecule when guided by the STM tip. Controlling and time following the intramolecular behavior of a large molecule on a surface is the first step towards the design of molecular tunnel-wired nanorobots.

  18. Human ceruloplasmin. Intramolecular electron transfer kinetics and equilibration

    DEFF Research Database (Denmark)

    Farver, O; Bendahl, L; Skov, L K

    1999-01-01

    Pulse radiolytic reduction of disulfide bridges in ceruloplasmin yielding RSSR(-) radicals induces a cascade of intramolecular electron transfer (ET) processes. Based on the three-dimensional structure of ceruloplasmin identification of individual kinetically active disulfide groups and type 1 (T1...... and indeed electron equilibration between T1A and the trinuclear copper center in the domain 1-6 interface takes place with a rate constant of 2.9 +/- 0.6 s(-1). The equilibrium constant is 0.17. Following reduction of T1A Cu(II), another ET process takes place between RSSR(-) and T1B copper(II) of domain 4...

  19. Ciclização intramolecular: uma estratégia promissora no desenvolvimento de pró-fármacos Intramolecular cyclization: a promising strategy in the prodrug conception

    Directory of Open Access Journals (Sweden)

    Cledir Santos

    2008-09-01

    Full Text Available Muitos fármacos estão associados a vários efeitos adversos e limitada biodisponibilidade. A resolução destes problemas continua sendo um alvo importante para a comunidade científica. O desenvolvimento de pró-fármacos que conduzam a uma liberação controlada in vivo é um caminho atrativo para resolver estes problemas. Um pró-fármaco clássico é molécula inativa, em que o princípio ativo é ligado covalentemente a uma unidade transportadora, de modo que o fármaco pode ser liberado através de uma reação química ou enzimática. Um sistema novo e interessante de pró-fármaco, que tem sido apresentado para fármacos possuidores de grupos amino, álcool e tiol, é aquele no qual o princípio ativo é liberado através de uma ciclização intramolecular. Neste caso, o processo de ciclização, dependendo da cadeia da unidade transportadora e do próprio fármaco, pode controlar a velocidade de liberação do princípio ativo. Desta forma, este trabalho apresenta uma revisão do desenvolvimento de pró-fármacos baseados na liberação do princípio ativo através de uma ciclização intramolecular.Many drugs used for the treatment of common diseases are associated with various adverse effects and limited bioavailability. The suppression of such problems continues to be a very important target for scientists. The development of prodrugs for controlled release in vivo is an attractive way to overcome these problems. Classical in prodrug is an inactive molecule which the parent drug is covalently bonded to a carrier unit, and which can liberate the drug through chemical or enzymatic pathways. A new and interesting prodrug system for amine, alcohol, and thiol drugs takes advantage of several easy intramolecular cyclization reactions. So, the cyclization process can control the release rate of the parent drug. In this paper is a review about the prodrug strategies based on intramolecular cyclization reactions is presented.

  20. Intramolecularly coordinated azobenzene selenium derivatives: effect of strength of the Se···N intramolecular interaction on luminescence.

    Science.gov (United States)

    Srivastava, Kriti; Chakraborty, Tapash; Singh, Harkesh B; Butcher, Ray J

    2011-05-07

    A series of selenium derivatives (6-12) of 2-phenylazophenyl have been synthesized using o-lithiation route. The effect of the strength of the intramolecular Se···N interaction on the absorption spectra as well as emission spectra has been studied. The studies suggest that the secondary bonding Se···N interaction give rise to fluorescence, however, the strength of Se···N interaction cannot be directly correlated with the intensity of the fluorescence. TD-DFT calculations show that the main transition involved in the absorption spectra of the compound is the ligand based π-π* type.

  1. Heterocycles by Transition Metals Catalyzed Intramolecular Cyclization of Acetylene Compounds

    International Nuclear Information System (INIS)

    Vizer, S.A.; Yerzhanov, K.B.; Dedeshko, E.C.

    2003-01-01

    Review shows the new strategies in the synthesis of heterocycles, having nitrogen, oxygen and sulfur atoms, via transition metals catalyzed intramolecular cyclization of acetylenic compounds on the data published at the last 30 years, Unsaturated heterocyclic compounds (pyrroles and pyrroline, furans, dihydro furans and benzofurans, indoles and iso-indoles, isoquinolines and isoquinolinones, aurones, iso coumarins and oxazolinone, lactams and lactones with various substitutes in heterocycles) are formed by transition metals, those salts [PdCl 2 , Pd(OAc) 2 , HgCl 2 , Hg(OAc) 2 , Hg(OCOCF 3 ) 2 , AuCl 3 ·2H 2 O, NaAuCl 4 ·2H 2 O, CuI, CuCl], oxides (HgO) and complexes [Pd(OAc) 2 (PPh 3 )2, Pd(PPh 3 ) 4 , PdCl 2 (MeCN) 2 , Pd(OAc ) 2 /TPPTS] catalyzed intramolecular cyclization of acetylenic amines, amides, ethers, alcohols, acids, ketones and βdiketones. More complex hetero polycyclic systems typical for natural alkaloids can to obtain similar. Proposed mechanisms of pyrroles, isoquinolines, iso indoles and indoles, benzofurans and iso coumarins, thiazolopyrimidinones formation are considered. (author)

  2. Excited state intramolecular proton transfer (ESIPT) in dihydroxyphenyl anthracenes.

    Science.gov (United States)

    Wang, Yu-Hsuan; Wan, Peter

    2011-12-01

    The photochemistry of three 9-(dihydroxyphenyl)anthracenes 6-8 was studied in neat CH(3)CN and selected organic solvents, to investigate excited state intramolecular proton transfer (ESIPT) from the phenol to the anthracene moiety. In D(2)O-CH(3)CN mixtures, the observed deuterium exchange of 6-8 is consistent with water-mediated (formal) ESIPT process from the ortho phenolic OH to the 10'-position of the anthracene ring, giving rise to quinone methide (QM) intermediates 12-14. There is no ESIPT for the corresponding methoxy-substituted compounds. Introduction of an extra hydroxyl group onto the phenol ring at different positions led to a range of deuterium exchange quantum yields (Φ = 0.03 to 0.15). In addition to the anticipated ESIPT process to the 10'-position, in neat CH(3)CN and other organic solvents, 6 (but not 7 or 8) undergoes a clean photocyclization to give bridged product 19 in quantitative yield. The mechanism of this unique photocyclization may involve a direct ESIPT or a 1,4-hydrogen transfer from the ortho phenolic OH to the 9'-position of the anthracene ring, generating a zwitterion (20) or diradical (21) intermediate, respectively, followed by ring closure. Fluorescence studies of 6 in various solvents show the existence of both local excited and intramolecular charge transfer states whereas only the former was present for 7 and 8, offering a possible rationalization for the photocyclization pathway.

  3. Reações intramoleculares como modelos não miméticos de catálise enzimática Intramolecular reactions as non mimetic models of enzyme catalysis

    Directory of Open Access Journals (Sweden)

    José Carlos Gesser

    1997-12-01

    Full Text Available This review gives a critical idea on the importance of intramolecular reactions as models for enzymatic catalysis. Intramolecular lactonizations, ester and amide hydrolysis studies result in theories which try to explain the difference between intermolecular, intramolecular and enzyme reactions and rationalize the enhancement promoted by these biological catalyst.

  4. The Nature of the Intramolecular Charge Transfer State in Peridinin

    Science.gov (United States)

    Wagner, Nicole L.; Greco, Jordan A.; Enriquez, Miriam M.; Frank, Harry A.; Birge, Robert R.

    2013-01-01

    Experimental and theoretical evidence is presented that supports the theory that the intramolecular charge transfer (ICT) state of peridinin is an evolved state formed via excited-state bond-order reversal and solvent reorganization in polar media. The ICT state evolves in ICT state are generated via mixing of the “11Bu+” ionic state and the lowest-lying “21Ag–” covalent state. The resulting ICT state is primarily 1Bu+-like in character and exhibits not only a large oscillator strength but an unusually large doubly excited character. In most solvents, two populations exist in equilibrium, one with a lowest-lying ICT ionic state and a second with a lowest-lying “21Ag–” covalent state. The two populations are separated by a small barrier associated with solvent relaxation and cavity formation. PMID:23528091

  5. Intramolecular electron transfer in single-site-mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; Pascher, T

    1993-01-01

    . Natl. Acad. Sci. U.S.A. 86, 6968-6972]. The RSSR- radical produced in the above reaction was reoxidized in a slower intramolecular electron-transfer process (30-70 s-1 at 298 K) concomitant with a further reduction of the Cu(II) ion. The temperature dependence of the latter rates was determined...... and used to derive information on the possible effects of the mutations. The substitution of residue Phe114, situated on the opposite side of Cu relative to the disulfide, by Ala resulted in a rate increase by a factor of almost 2. By assuming that this effect is only due to an increase in driving force......Single-site mutants of the blue, single-copper protein, azurin, from Pseudomonas aeruginosa were reduced by CO2- radicals in pulse radiolysis experiments. The single disulfide group was reduced directly by CO2- with rates similar to those of the native protein [Farver, O., & Pecht, I. (1989) Proc...

  6. Intramolecular electron transfer in Pseudomonas aeruginosa cd(1) nitrite reductase

    DEFF Research Database (Denmark)

    Farver, Ole; Brunori, Maurizio; Cutruzzolà, Francesca

    2009-01-01

    The cd(1) nitrite reductases, which catalyze the reduction of nitrite to nitric oxide, are homodimers of 60 kDa subunits, each containing one heme-c and one heme-d(1). Heme-c is the electron entry site, whereas heme-d(1) constitutes the catalytic center. The 3D structure of Pseudomonas aeruginosa...... nitrite reductase has been determined in both fully oxidized and reduced states. Intramolecular electron transfer (ET), between c and d(1) hemes is an essential step in the catalytic cycle. In earlier studies of the Pseudomonas stutzeri enzyme, we observed that a marked negative cooperativity...... is controlling this internal ET step. In this study we have investigated the internal ET in the wild-type and His369Ala mutant of P. aeruginosa nitrite reductases and have observed similar cooperativity to that of the Pseudomonas stutzeri enzyme. Heme-c was initially reduced, in an essentially diffusion...

  7. Detection of a transient intramolecular hydrogen bond using 1JNH scalar couplings

    Science.gov (United States)

    Xiang, ShengQi; Zweckstetter, Markus

    2014-06-01

    Hydrogen bonds are essential for the structure, stability and folding of proteins. The identification of intramolecular hydrogen bonds, however, is challenging, in particular in transiently folded states. Here we studied the presence of intramolecular hydrogen bonds in the folding nucleus of the coiled-coil structure of the GCN4 leucine zipper. Using one-bond 1JNH spin-spin coupling constants and hydrogen/deuterium exchange, we demonstrate that a transient intramolecular hydrogen bond is present in the partially helical folding nucleus of GCN(16-31). The data demonstrate that 1JNH couplings are a sensitive tool for the detection of transient intramolecular hydrogen bonds in challenging systems where the effective/useable protein concentration is low. This includes peptides at natural abundance but also uniformly labeled biomolecules that are limited to low concentrations because of precipitation or aggregation.

  8. Enantioselective synthesis of almorexant via iridium-catalysed intramolecular allylic amidation

    NARCIS (Netherlands)

    Fananas Mastral, Martin; Teichert, Johannes F.; Fernandez-Salas, Jose Antonio; Heijnen, Dorus; Feringa, Ben L.

    2013-01-01

    An enantioselective synthesis of almorexant, a potent antagonist of human orexin receptors, is presented. The chiral tetrahydroisoquinoline core structure was prepared via iridium-catalysed asymmetric intramolecular allylic amidation. Further key catalytic steps of the synthesis include an oxidative

  9. Dynamics of intramolecular spin exchange interaction of a nitronyl nitroxide diradical in solution and on surfaces

    OpenAIRE

    Lloveras Montserrat, Vega; Badetti, Elena; Veciana Miró, Jaume; Vidal-Gancedo, José

    2016-01-01

    In this paper we report the study of the dynamics of a thermally modulated intramolecular spin exchange interaction of a novel diradical nitronyl nitroxide-substituted disulfide in solution and when it is grafted on a gold surface. The structure of this diradical was designed to have flexible chains leading to intramolecular collisions and hence spin exchange interaction, and with an appropriate binding group to be grafted on the gold surface to study its behavior on the surface. In solution,...

  10. Intramolecular distribution of carbon isotopes in fatty acids

    International Nuclear Information System (INIS)

    von Unruh, G.E.; Hayes, J.M.

    1975-01-01

    It is well known that biochemical reactions fractionate the stable isotopes of carbon, distributing them unevenly among their products. For amino acids and biosynthesized acetate, it has been shown that the isotopes are fractionated on an intramolecular basis, with some carbon positions being enriched in 13 C relative to others. With the goal of eventually determining the extent to which the isotopic distribution pattern in acetate is carried over into alkyl chains, we are working to develop methods for determining isotopic distributions within fatty acids. Because there are no purely instrumental approaches with sufficient precision to allow isotopic measurements on the intact fatty acid, chemical degradation must be applied in order to prepare CO 2 from each position of interest. Kinetic isotope effects during the chemical reactions and vapor pressure isotope effects during sample preparation and handling can significantly affect the results, and must be very carefully controlled and investigated. Thus far, suitable methods have been developed for determination of the isotopic composition of the carboxyl carbon in fatty acids. The isotopic composition of the aliphatic portion of the molecule can then be determined by the difference after the overall 13 C content has been determined by combustion

  11. Intramolecular charge transfer effects on 3-aminobenzoic acid

    Energy Technology Data Exchange (ETDEWEB)

    Stalin, T. [Department of Chemistry, Annamalai University, Annamalainagar, Chidambaram 608 002, Tamil Nadu (India); Rajendiran, N. [Department of Chemistry, Annamalai University, Annamalainagar, Chidambaram 608 002, Tamil Nadu (India)], E-mail: drrajendiran@rediffmail.com

    2006-03-20

    Effect of solvents, buffer solutions of different pH and {beta}-cyclodextrin on the absorption and fluorescence spectra of 3-aminobenzoic acid (3ABA) have been investigated. The solid inclusion complex of 3ABA with {beta}-CD is discussed by UV-Vis, fluorimetry, semiempirical quantum calculations (AM1), FT-IR, {sup 1}H NMR and Scanning Electron Microscope (SEM). The thermodynamic parameters ({delta}H, {delta}G and {delta}S) of the inclusion process are also determined. The experimental results indicated that the inclusion processes is an exothermic and spontaneous. The large Stokes shift emission in solvents with 3ABA are correlated with different solvent polarity scales suggest that, 3ABA molecule is more polar in the S{sub 1} state. Solvent, {beta}-CD studies and excited state dipole moment values confirms that the presence of intramolecular charge transfer (ICT) in 3ABA. Acidity constants for different prototropic equilibria of 3ABA in the S{sub 0} and S{sub 1} states are calculated. {beta}-Cyclodextrin studies shows that 3ABA forms a 1:1 inclusion complex with {beta}-CD. {beta}-CD studies suggest COOH group present in non-polar part and amino group present in hydrophilic part of the {beta}-CD cavity. A mechanism is proposed to explain the inclusion process.

  12. Intramolecular Crosstalk between Catalytic Activities of Receptor Kinases

    KAUST Repository

    Kwezi, Lusisizwe

    2018-01-22

    Signal modulation is important for the growth and development of plants and this process is mediated by a number of factors including physiological growth regulators and their associated signal transduction pathways. Protein kinases play a central role in signaling, including those involving pathogen response mechanisms. We previously demonstrated an active guanylate cyclase (GC) catalytic center in the brassinosteroid insensitive receptor (AtBRI1) within an active intracellular kinase domain resulting in dual enzymatic activity. Here we propose a novel type of receptor architecture that is characterized by a functional GC catalytic center nested in the cytosolic kinase domain enabling intramolecular crosstalk. This may be through a cGMP-AtBRI1 complex forming that may induce a negative feedback mechanism leading to desensitisation of the receptor, regulated through the cGMP production pathway. We further argue that the comparatively low but highly localized cGMP generated by the GC in response to a ligand is sufficient to modulate the kinase activity. This type of receptor therefore provides a molecular switch that directly and/or indirectly affects ligand dependent phosphorylation of downstream signaling cascades and suggests that subsequent signal transduction and modulation works in conjunction with the kinase in downstream signaling.

  13. Intramolecular Schmidt reaction of acyl chlorides with alkyl azides: preparation of pyrrolizine by intramolecular capture of intermediates with alkenes or alkynes.

    Science.gov (United States)

    Wang, Bao-Juan; Xue, Ping; Gu, Peiming

    2015-02-11

    The preparation of substituted pyrrolizines through the Schmidt reaction of acyl chlorides with alkyl azides has been realized. Intramolecular capture of the isocyanate ion and N-acyliminium ion intermediates from the Schmidt process with alkene or alkyne units was achieved, and the efficiency of the conversion with respect to ring construction and bond formation was demonstrated.

  14. Dynamics of the excited state intramolecular charge transfer

    International Nuclear Information System (INIS)

    Joo, T.; Kim, C.H.

    2006-01-01

    The 6-dodecanoyl-2-dimethylaminonaphtalene (laurdan), a derivative of 6-propanoyl- 2-dimethylaminonaphthalene (prodan), has been used as a fluorescent probe in cell imaging, especially in visualizing the lipid rafts by the generalized polarization (GP) images, where GP=(I 440 -I 490 )/(I 440 +I 490 ) with I being the fluorescence intensity. The fluorescence spectrum of laurdan is sensitive to its dipolar environment due to the intramolecular charge transfer (ICT) process in S 1 state, which results in a dual emission from the locally excited (LE) and the ICT states. The ICT process and the solvation of the ICT state are very sensitive to the dipolar nature of the environment. In this work, the ICT of laurdan in ethanol has been studied by femtosecond time resolved fluorescence (TRF), especially TRF spectra measurement without the conventional spectral reconstruction method. TRF probes the excited states exclusively, a unique advantage over the pump/probe transient absorption technique, although time resolution of the TRF is generally lower than transient absorption and the TRF spectra measurement was possible only though the spectral reconstruction. Over the years, critical advances in TRF technique have been made in our group to achieve <50 fs time resolution with direct full spectra measurement capability. Detailed ICT and the subsequent solvation processes can be visualized unambiguously from the TRF spectra. Fig. 1 shows the TRF spectra of laurdan in ethanol at several time delays. Surprisingly, two bands at 433 and 476 nm are clearly visible in the TRF spectra of laurdan even at T = 0 fs. As time increases, the band at 476 nm shifts to the red while its intensity increases. The band at 433 nm also shifts slightly to the red, but loses intensity as time increases. The intensity of the 476 nm band reaches maximum at around 5 ps, where it is roughly twice as intense as that at 0 fs, and stays constant until lifetime decay is noticeable. The spectra were fit by

  15. New fast organic scintillators using intramolecular bromine quenching

    Science.gov (United States)

    Berlman, I. B.; Lutz, S. S.; Flournoy, J. M.; Ashford, C. B.; Franks, L. A.; Lyons, P. B.

    1984-08-01

    Organic scintillator solutions with decay times as fast as 500 ps and with relatively high conversion efficiencies have been developed. The intramolecular quenching was achieved through the novel approach of adding a bromine atom to the 3- or 4-position of para-oligophenylenes, the fluorescent solutes in these binary solutions. The bromine serves to enhance singlet-to-triplet intersystem crossing in the chromophore, causing a reduction in the scintillation yield and a conconitant reduction in the decay time. The very fast value given above probably also involves some intermolecular self-quenching at high concentration. In addition, the bromine reduces the symmetry of the molecules, thereby increasing their solubility. Finally, an alkyl chain on the opposite para position further increases the solubility and also increases the immunity of the chromophore to quenching. The following solutes were studied in binary liquid solutions and to a limited extent in plastics: 4-bromo-4″-(5-hexadecyl)-p-terphenyl: (4-BHTP), 3-bromo-4″-(5-hexadecyl)-p-terphenyl: (3-BHTP), 4-bromo-p-terphenyl: (4-BTP), 3-bromo-p-terphenyl: (3-BTP), 4-bromo-4‴-(5-hexadecyl)-p-quaterphenyl: (4-BHQP). The decay times for binary liquid solutions in toluene (at the indicated concentrations) were 0.51 ns for 4-BHTP (0.14 M), 0.75 ns for 3-BHTP (0.14 M), 0.57 ns for 3-BTP (0.14 M), and 1.3 ns for 4-BHQP (0.06 M). Binary plastics with 4-BHTP as the solute in concentrations up to 0.14 M were cast in polystyrene. The shortest decay time, 0.40 ns, was measured for the 0.14 M concentration. A plastic scintillator containing 3-BTP (0.11 M in polystyrene) had a decay time of 0.85 ns. These results compare favorably with the plastic scintillator BC-422 whose decay time is about 1.4 ns.

  16. New fast organic scintillators using intramolecular bromine quenching

    International Nuclear Information System (INIS)

    Berlman, I.B.; Lutz, S.S.; Flournoy, J.M.; Ashford, C.B.; Franks, L.A.

    1984-01-01

    Organic scintillator solutions with decay times as fast as 500 ps and with relatively high conversion efficiencies have been developed. The intramolecular quenching was achieved through the novel approach of adding a bromine atom to the 3- or 4-position of para-oligophenylenes, the fluorescent solutes in these binary solutions. The bromine serves to enhance singlet-to-triplet intersystem crossing in the chromophore, causing a reduction in the scintillation yield and a concomitant reduction in the decay time. The very fast value given above probably also involves some intermolecular self-quenching at high concentration. In addition, the bromine reduces the symmetry of the molecules, thereby increasing their solubility. Finally, an alkyl chain on the opposite para position further increases the solubility and also increases the immunity of the chromophore to quenching. The decay times for binary liquid solutions in toluene (at the indicated concentrations) were 0.51 ns for 4-BHTP (0.14 M), 0.75 ns for 3-BHTP (0.14 M), 0.57 ns for 3-BTP (0.14 M), and 1.3 ns for 4-BHQP (0.06 M). Binary plastics with 4-BHTP as the solute in concentrations up to 0.14 M were cast in polystyrene. The shortest decay time, 0.40 ns, was measured for the 0.14 M concentration. A plastic scintillator containing 3-BTP (0.11 M in polystyrene) had a decay time of 0.85 ns. These results compare favorably with the plastic scintillator BC-422 whose decay time is about 1.4 ns. (orig./HSI)

  17. Conductance and activation energy for electron transport in series and parallel intramolecular circuits.

    Science.gov (United States)

    Hsu, Liang-Yan; Wu, Ning; Rabitz, Herschel

    2016-11-30

    We investigate electron transport through series and parallel intramolecular circuits in the framework of the multi-level Redfield theory. Based on the assumption of weak monomer-bath couplings, the simulations depict the length and temperature dependence in six types of intramolecular circuits. In the tunneling regime, we find that the intramolecular circuit rule is only valid in the weak monomer coupling limit. In the thermally activated hopping regime, for circuits based on two different molecular units M a and M b with distinct activation energies E act,a > E act,b , the activation energies of M a and M b in series are nearly the same as E act,a while those in parallel are nearly the same as E act,b . This study gives a comprehensive description of electron transport through intramolecular circuits from tunneling to thermally activated hopping. We hope that this work can motivate additional studies to design intramolecular circuits based on different types of building blocks, and to explore the corresponding circuit laws and the length and temperature dependence of conductance.

  18. Accounting for intra-molecular vibrational modes in open quantum system description of molecular systems.

    Science.gov (United States)

    Roden, Jan; Strunz, Walter T; Whaley, K Birgitta; Eisfeld, Alexander

    2012-11-28

    Electronic-vibrational dynamics in molecular systems that interact with an environment involve a large number of degrees of freedom and are therefore often described by means of open quantum system approaches. A popular approach is to include only the electronic degrees of freedom into the system part and to couple these to a non-Markovian bath of harmonic vibrational modes that is characterized by a spectral density. Since this bath represents both intra-molecular and external vibrations, it is important to understand how to construct a spectral density that accounts for intra-molecular vibrational modes that couple further to other modes. Here, we address this problem by explicitly incorporating an intra-molecular vibrational mode together with the electronic degrees of freedom into the system part and using the Fano theory for a resonance coupled to a continuum to derive an "effective" bath spectral density, which describes the contribution of intra-molecular modes. We compare this effective model for the intra-molecular mode with the method of pseudomodes, a widely used approach in simulation of non-Markovian dynamics. We clarify the difference between these two approaches and demonstrate that the respective resulting dynamics and optical spectra can be very different.

  19. Surprisingly Mild Enolate-Counterion-Free Pd(0)-Catalyzed Intramolecular Allylic Alkylations

    DEFF Research Database (Denmark)

    Madec, David; Prestat, Guillaume; Martini, Elisabetta

    2005-01-01

    Palladium-catalyzed intramolecular allylic alkylations of unsaturated EWG-activated amides can take place under phase-transfer conditions or in the presence of a crown ether. These new reaction conditions are milder and higher yielding than those previously reported. A rationalization for such an......Palladium-catalyzed intramolecular allylic alkylations of unsaturated EWG-activated amides can take place under phase-transfer conditions or in the presence of a crown ether. These new reaction conditions are milder and higher yielding than those previously reported. A rationalization...

  20. Gold versus silver catalyzed intramolecular hydroarylation reactions of [(3-arylprop-2-ynyl)oxy]benzene derivatives.

    Science.gov (United States)

    Arcadi, Antonio; Blesi, Federico; Cacchi, Sandro; Fabrizi, Giancarlo; Goggiamani, Antonella; Marinelli, Fabio

    2012-12-28

    The scope and the generality of gold versus silver catalyzed intramolecular hydroarylation reactions of 3-[(3-arylprop-2-ynyl)oxy]benzene derivatives in terms of rings substitution were investigated. Only products deriving from 6-endo cyclization were exclusively formed. The features of substituents had a considerable effect on the reaction outcome in the presence of silver catalysis, whereas gold catalysis revealed a unique blend of reactivity and selectivity and represented the only choice for the intramolecular hydroarylation reaction of the starting substrates bearing electron deficient arenes.

  1. The effect of intramolecular quantum modes on free energy relationships for electron transfer reactions

    DEFF Research Database (Denmark)

    Ulstrup, Jens; Jortner, Joshua

    1975-01-01

    -frequency intramolecular degrees of feedom on the free energy relationship for series of closely related reactions was investigated for various model systems involving displacement of potential energy surfaces, frequency shift, and anharmonicity effects. The free energy plots are generally found to pass through a maximum...... and to be asymmetric with a slower decrease in the transition probability with increasing energy of reaction. For high-frequency intramolecular modes this provides a rationalization of the experimental observation of ''activationless'' regions. Isotope effects are discussed as also are the oscillatory free energy...

  2. Influence of intramolecular and intermolecular hydrogen bonding on the fluorescence decay time of indigo derivatives

    International Nuclear Information System (INIS)

    Schneider, S.; Lill, E.; Hefferle, P.; Doerr, F.

    1981-01-01

    It is well known that both intramolecular and intermolecular hydrogen bonding can lead to drastic changes in the lifetime of the first excited singlet state. By employing a synchronously pumped, mode-locked dye-laser for excitation in connection with a continuously operated streak camera for detection, the solvent-dependent fluorescence decay times of several indigo derivatives were determined with high temporal resolution (approx. 5 ps with deconvolution). It is found that in indigo dyes intramolecular hydrogen bonding gives rise to a strong fluorescence quenching; intermolecular hydrogen bonding can also provide a channel for fast radiationless deactivation in those derivatives in which the former are not present. (author)

  3. Failures of TDDFT in describing the lowest intramolecular charge-transfer excitation in <em>para>-nitroaniline

    DEFF Research Database (Denmark)

    Eriksen, Janus J.; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin

    2013-01-01

    We investigate the failure of Time{Dependent Density Functional Theory (TDDFT) with the CAM{B3LYP exchange{correlation (xc) functional coupled to the Polarizable Embedding (PE) scheme (PE-CAM-B3LYP) in reproducing the solvatochromic shift of the lowest intense charge{transfer excitation in para{n...

  4. Intramolecular Diels-Alder reactions of pyrimidines, a synthetic and computational study

    NARCIS (Netherlands)

    Stolle, W.A.W.

    1992-01-01

    This thesis deals with an investigation on the ringtransformation reactions of 2and 5-(ω-alkynyl)pyrimidine derivatives, which undergo upon heating an intramolecular Diels-Alder reaction and subsequently a spontaneous retro Diels- Alder reaction. To get a better insight into the

  5. Potassium hydroxide/dimethyl sulfoxide promoted intramolecular cyclization for the synthesis of benzimidazol-2-ones.

    Science.gov (United States)

    Beyer, Astrid; Reucher, Christine M M; Bolm, Carsten

    2011-06-03

    A new protocol for intramolecular N-arylations of ureas to form benzimidazol-2-ones has been developed. The cyclization reaction occurs in the presence of KOH and DMSO at close to ambient temperature. Under these conditions the yields are high and a wide range of functional groups are tolerated.

  6. Optimized measurements of separations and angles between intra-molecular fluorescent markers

    DEFF Research Database (Denmark)

    Mortensen, Kim; Sung, Jongmin; Flyvbjerg, Henrik

    2015-01-01

    We demonstrate a novel, yet simple tool for the study of structure and function of biomolecules by extending two-colour co-localization microscopy to fluorescent molecules with fixed orientations and in intra-molecular proximity. From each colour-separated microscope image in a time-lapse movie...

  7. Symmetry-breaking intramolecular charge transfer in the excited state of meso-linked BODIPY dyads

    KAUST Repository

    Whited, Matthew T.

    2012-01-01

    We report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both molecules undergo symmetry-breaking intramolecular charge transfer in the excited state, and the directly linked dyad serves as a visible-light-absorbing analogue of 9,9′-bianthryl.

  8. Intramolecular hydrogen bond: Can it be part of the basis set of ...

    Indian Academy of Sciences (India)

    IMHB appears in one of the equivalent complete VIC basis sets, its RFC could be used as a measure of bond strength parameter. Keywords. Hydrogen bond; intramolecular; relaxed force constant; normal mode analysis; bond strength parameter. 1. Introduction. The advantages of the compliance constants (the inverse.

  9. Neutral versus cationic Group 3 metal alkyl catalysts : performance in intramolecular hydroamination/cyclisation

    NARCIS (Netherlands)

    de Araujo Bambirra, Sergio; Tsurugi, H; van Leusen, D; Hessen, B

    2006-01-01

    The relative catalytic activity of neutral dialkyl versus cationic monoalkyl Group 3 metal catalysts in the intramolecular hydroamination/cyclisation of the 2,2-dimethyl-4-pentenylamine reference substrate was investigated. This was found to depend strongly on the nature of the monoanionic ancillary

  10. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik

    2015-01-01

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static” ...

  11. Regio-Selective Intramolecular Hydrogen/Deuterium Exchange in Gas-Phase Electron Transfer Dissociation

    Science.gov (United States)

    Hamuro, Yoshitomo

    2017-05-01

    Protein backbone amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) typically utilizes enzymatic digestion after the exchange reaction and before MS analysis to improve data resolution. Gas-phase fragmentation of a peptic fragment prior to MS analysis is a promising technique to further increase the resolution. The biggest technical challenge for this method is elimination of intramolecular hydrogen/deuterium exchange (scrambling) in the gas phase. The scrambling obscures the location of deuterium. Jørgensen's group pioneered a method to minimize the scrambling in gas-phase electron capture/transfer dissociation. Despite active investigation, the mechanism of hydrogen scrambling is not well-understood. The difficulty stems from the fact that the degree of hydrogen scrambling depends on instruments, various parameters of mass analysis, and peptide analyzed. In most hydrogen scrambling investigations, the hydrogen scrambling is measured by the percentage of scrambling in a whole molecule. This paper demonstrates that the degree of intramolecular hydrogen/deuterium exchange depends on the nature of exchangeable hydrogen sites. The deuterium on Tyr amide of neurotensin (9-13), Arg-Pro-Tyr-Ile-Leu, migrated significantly faster than that on Ile or Leu amides, indicating the loss of deuterium from the original sites is not mere randomization of hydrogen and deuterium but more site-specific phenomena. This more precise approach may help understand the mechanism of intramolecular hydrogen exchange and provide higher confidence for the parameter optimization to eliminate intramolecular hydrogen/deuterium exchange during gas-phase fragmentation.

  12. Intramolecular 13C analysis of tree rings provides multiple plant ecophysiology signals covering decades.

    Science.gov (United States)

    Wieloch, Thomas; Ehlers, Ina; Yu, Jun; Frank, David; Grabner, Michael; Gessler, Arthur; Schleucher, Jürgen

    2018-03-22

    Measurements of carbon isotope contents of plant organic matter provide important information in diverse fields such as plant breeding, ecophysiology, biogeochemistry and paleoclimatology. They are currently based on 13 C/ 12 C ratios of specific, whole metabolites, but we show here that intramolecular ratios provide higher resolution information. In the glucose units of tree-ring cellulose of 12 tree species, we detected large differences in 13 C/ 12 C ratios (>10‰) among carbon atoms, which provide isotopically distinct inputs to major global C pools, including wood and soil organic matter. Thus, considering position-specific differences can improve characterisation of soil-to-atmosphere carbon fluxes and soil metabolism. In a Pinus nigra tree-ring archive formed from 1961 to 1995, we found novel 13 C signals, and show that intramolecular analysis enables more comprehensive and precise signal extraction from tree rings, and thus higher resolution reconstruction of plants' responses to climate change. Moreover, we propose an ecophysiological mechanism for the introduction of a 13 C signal, which links an environmental shift to the triggered metabolic shift and its intramolecular 13 C signature. In conclusion, intramolecular 13 C analyses can provide valuable new information about long-term metabolic dynamics for numerous applications.

  13. Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

    Directory of Open Access Journals (Sweden)

    Valentin A. Rassadin

    2017-09-01

    Full Text Available A new and efficient approach to five- and six-membered benzannelated sultams by intramolecular C-arylation of tertiary 1-(methoxycarbonylmethanesulfonamides under palladium catalysis is described. In case of the α-toluenesulfonamide derivative, an unexpected formation of a 2,3-diarylindole was observed under the same conditions.

  14. Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides.

    Science.gov (United States)

    Rassadin, Valentin A; Scholz, Mirko; Klochkova, Anastasiia A; de Meijere, Armin; Sokolov, Victor V

    2017-01-01

    A new and efficient approach to five- and six-membered benzannelated sultams by intramolecular C -arylation of tertiary 1-(methoxycarbonyl)methanesulfonamides under palladium catalysis is described. In case of the α-toluenesulfonamide derivative, an unexpected formation of a 2,3-diarylindole was observed under the same conditions.

  15. Intramolecular butenolide allene photocycloadditions and ensuing retro-ene reactions of some photoadducts

    NARCIS (Netherlands)

    Lutteke, G.; Kleinnijenhuis, R.A.; Jacobs, I.; Wrigstedt, P.J.; Correia, A.C.A.; Nieuwenhuizen, R.; Hue, B.T.B.; Goubitz, K.; Peschar, R.; van Maarseveen, J.H.; Hiemstra, H.

    2011-01-01

    This report describes intramolecular [2+2] photocycloadditions of several butenolides with an allenylmethyl substituent at the 5-position. These photosubstrates were prepared from 2-(silyloxy)furans through silver-mediated reactions with allenylmethyl bromides. Two cases were studied where the

  16. Intramolecular Morita-Baylis-Hillman reaction as a strategy for the construction of tricyclic sesquiterpene cores.

    Science.gov (United States)

    Peter, Clovis; Geoffroy, Philippe; Miesch, Michel

    2018-02-21

    Starting from a common polyfunctionalized bicyclo[3.2.1]octane-6,8-dione intermediate, a concise synthetic route to tricyclic cores found in quadrane, suberosane, cedrane and related sesquiterpenes was developed using a Morita-Baylis-Hillman intramolecular reaction as a key step.

  17. Synthesis of neplanocin A and its 3'-epimer via an intramolecular Baylis-Hillman reaction.

    Science.gov (United States)

    Tan, Yun Xuan; Santhanakrishnan, Sridhar; Yang, Hai Yan; Chai, Christina L L; Tam, Eric Kwok Wai

    2014-09-05

    The key cyclopentenyl intermediate 11b was synthesized in 4 steps from d-ribose in 41% overall yield via an efficient intramolecular Baylis-Hillman reaction. This novel key intermediate can be modified easily and transformed to neplanocin A (1a) and its 3'-epimer (1b).

  18. Recent applications of intramolecular Diels-Alder reactions to natural product synthesis

    DEFF Research Database (Denmark)

    Juhl, M.; Tanner, David Ackland

    2009-01-01

    This tutorial review presents some recent examples of intramolecular Diels-Alder (IMDA) reactions as key complexity-generating steps in the total synthesis of structurally intricate natural products. The opportunities afforded by transannular (TADA) versions of the IMDA reaction in complex molecule...

  19. Effect of intramolecular hydrogen bonding and electron donation on substituted anthrasemiquinone characteristics

    International Nuclear Information System (INIS)

    Pal, H.; Mukherjee, T.

    1994-01-01

    The acid-base and redox characteristics of the semiquinones of a number of hydroxy and amino-substituted anthraquinones have been investigated. Results are explained on the basis of electron-donating properties and intramolecular hydrogen bond forming capabilities of the substituents. (author). 4 refs., 1 tab., 1 fig

  20. 1 H NMR-Based Kinetic-Mechanistic Study of the Intramolecular ...

    African Journals Online (AJOL)

    A 1H NMR study of the acid-catalyzed, intramolecular trans-esterification between isomeric 2-exo-3-exo-dihydroxybornane monoacrylate esters has afforded insights into the reaction mechanism and permitted the determination of kinetic and thermodynamic parameters for the pseudo-first-order processes. KEYWORDS ...

  1. The first strand transfer during HIV-1 reverse transcription can occur either intramolecularly or intermolecularly

    NARCIS (Netherlands)

    van Wamel, J. L.; Berkhout, B.

    1998-01-01

    Reverse transcription is a complicated process that involves at least two cDNA transfer reactions to produce a full-length copy DNA of the retroviral RNA genome. Because one retrovirus particle contains two identical genomic RNA molecules, the transfers can occur in an intramolecular or

  2. Intramolecular Transannulation of Alkynyl Triazoles via Alkyne-Carbene Metathesis Step: Access to Fused Pyrroles

    Science.gov (United States)

    Shi, Yi; Gevorgyan, Vladimir

    2013-01-01

    An intramolecular Rh-catalyzed transannulation reaction of alkynyl triazoles has been developed. This method allows efficient construction of various 5,5-fused pyrroles, including tetrahydropyrrolo and spiro systems. The method demonstrates excellent functional group compatibility. A rhodium carbene-alkyne metathesis mechanism is proposed for this transformation. PMID:24093728

  3. On prediction of OH stretching frequencies in intramolecularly hydrogen bonded systems

    DEFF Research Database (Denmark)

    Hansen, Poul Erik; Spanget-Larsen, Jens

    2012-01-01

    OH stretching frequencies are investigated for a series of non-tautomerizing systems with intramolecular hydrogen bonds. Effective OH stretching wavenumbers are predicted by the application of empirical correlation procedures based on the results of B3LYP/6-31G(d) theoretical calculations in the ...

  4. Rationalizing Ring-Size Selectivity in Intramolecular Pd-Catalyzed Allylations of Resonance-Stabilized Carbanions

    DEFF Research Database (Denmark)

    Norrby, Per-Ola; Mader, Mary M.; Vitale, Maxime

    2003-01-01

    Computational methods were applied to the Pd-catalyzed intramolecular allylations of resonance-stabilized carbanions obtained from amide and ketone substrates, with the aim of rationalizing the endo- vs. exo-selectivity in the cyclizations. In addition, ester substrates were prepared and subjecte...

  5. Intramolecular Pnicogen Interactions in PHF(CH2)nPHF (n=26) Systems

    Czech Academy of Sciences Publication Activity Database

    Sanchez-Sanz, Goar; Alkorta, I.; Trujillo, Cristina; Elguero, J.

    2013-01-01

    Roč. 14, č. 8 (2013), s. 1656-1665 ISSN 1439-4235 Institutional support: RVO:61388963 Keywords : electron density shift * intramolecular interactions * ab initio calculations * pnicogens * electrostatic interactions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.360, year: 2013

  6. Theoretical Investigation of Intramolecular Hydrogen Shift Reactions in 3-Methyltetrahydrofuran (3-MTHF) Oxidation.

    Science.gov (United States)

    Parab, Prajakta R; Sakade, Naoki; Sakai, Yasuyuki; Fernandes, Ravi; Heufer, K Alexander

    2015-11-05

    3-Methyltetrahydrofuran (3-MTHF) is proposed to be a promising fuel component among the cyclic oxygenated species. To have detailed insight of its combustion kinetics, intramolecular hydrogen shift reactions for the ROO to QOOH reaction class are studied for eight ROO isomers of 3-MTHF. Rate constants of all possible reaction paths that involve formation of cyclic transition states are computed by employing the CBS-QB3 composite method. A Pitzer-Gwinn-like approximation has been applied for the internal rotations in reactants, products, and transition states for the accurate treatment of hindered rotors. Calculated relative barrier heights highlight that the most favorable reaction channel proceeds via a six membered transition state, which is consistent with the computed rate constants. Comparing total rate constants in ROO isomers of 3-MTHF with the corresponding isomers of methylcyclopentane depicts faster kinetics in 3-MTHF than methylcyclopentane reflecting the effect of ring oxygen on the intramolecular hydrogen shift reactions.

  7. Long-range intramolecular electron transfer in aromatic radical anions and binuclear transition metal complexes

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    1981-01-01

    radicals containing two aromatic end groups connected by a flexible polymethylene chain or a rigid cyclohexane frame is thus trapped on either aromatic end group, and ET between these groups can be detected by ESR techniques. Intramolecular ET also occurs in binuclear transition metal complexes in which......, and for intramolecular and inner sphere ET for transition metal complexes. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....... the coupling between the metal centers [(Ru(II)/Ru(III) and Ru(II)/Co(III) couples] is sufficiently weak (class I or II mixed valence compounds). The ET mechanism can involve either direct transfer between the donor and acceptor groups or a higher order mechanism in which ET proceeds through intermediate...

  8. Communication: Practical intramolecular symmetry adapted perturbation theory via Hartree-Fock embedding.

    Science.gov (United States)

    Parrish, Robert M; Gonthier, Jérôme F; Corminbœuf, Clémence; Sherrill, C David

    2015-08-07

    We develop a simple methodology for the computation of symmetry-adapted perturbation theory (SAPT) interaction energy contributions for intramolecular noncovalent interactions. In this approach, the local occupied orbitals of the total Hartree-Fock (HF) wavefunction are used to partition the fully interacting system into three chemically identifiable units: the noncovalent fragments A and B and a covalent linker C. Once these units are identified, the noninteracting HF wavefunctions of the fragments A and B are separately optimized while embedded in the HF wavefunction of C, providing the dressed zeroth order wavefunctions for A and B in the presence of C. Standard two-body SAPT (particularly SAPT0) is then applied between the relaxed wavefunctions for A and B. This intramolecular SAPT procedure is found to be remarkably straightforward and efficient, as evidenced by example applications ranging from diols to hexaphenyl-ethane derivatives.

  9. Fast and versatile microwave-assisted intramolecular Heck reaction in peptide macrocyclization using microwave energy.

    Science.gov (United States)

    Byk, Gerardo; Cohen-Ohana, Mirit; Raichman, Daniel

    2006-01-01

    We have revisited the intramolecular Heck reaction and investigated the microwave-assisted macrocyclization on preformed peptides using a model series of ring-varying peptides acryloyl-Gly-[Gly](n)-Phe(4-I)NHR; n = 0-4. The method was applied to both solution and solid supported cyclizations. We demonstrate that the intramolecular Heck reaction can be performed in peptides both in solution and solid support using a modified domestic microwave within 1 to 30 minutes in DMF under reflux with moderate yields ranging from 15 to 25% for a scale between 2-45 mg of linear precursors. The approach was applied to the synthesis of a constrained biologically relevant peptidomimetic bearing an Arg-Gly-Asp (RGD) sequence. These results make the microwave-assisted Heck reaction an attractive renovated approach for peptidomimetics. Copyright 2006 Wiley Periodicals, Inc.

  10. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  11. Enantioselective intramolecular hydroarylation of alkenes via directed C-H bond activation.

    Science.gov (United States)

    Harada, Hitoshi; Thalji, Reema K; Bergman, Robert G; Ellman, Jonathan A

    2008-09-05

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe)2]2 and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  12. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C–H Bond Activation

    Science.gov (United States)

    Harada, Hitoshi; Thalji, Reema K.; Bergman, Robert G.; Ellman, Jonathan A.

    2008-01-01

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe)2]2 and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer. PMID:18681407

  13. EVAPORATION: a new vapour pressure estimation methodfor organic molecules including non-additivity and intramolecular interactions

    Science.gov (United States)

    Compernolle, S.; Ceulemans, K.; Müller, J.-F.

    2011-09-01

    We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects), a method to predict (subcooled) liquid pure compound vapour pressure p0 of organic molecules that requires only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log10p0(T) is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: aldehydes, ketones, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA).

  14. A colorimetric and ratiometric fluorescent probe for sulfite based on an intramolecular cleavage mechanism.

    Science.gov (United States)

    Hou, Peng; Chen, Song; Voitchovsky, Kislon; Song, Xiangzhi

    2014-11-01

    A colorimetric and ratiometric fluorescent sulfite probe, the levulinate of 4-hydroxynaphthalimide, was successfully synthesized from 4-hydroxy-naphthalimide and levulinic acid. Through sulfite-mediated intramolecular cleavage, the probe was converted into 4-hydroxynaphthalimide, which when excited at 450 nm, displayed a large Stokes shift due to the intramolecular charge transfer process. The probe exhibited high selectivity and sensitivity towards sulfite over other typical anionic species (F(-), Cl(-), Br(-), I(-), HPO(4)(2-), SO(4)(2-), NO(3)(-), AcO(-), ClO(4)(-), HCO(3)(-)) in HEPES-buffered solution (25 mm, pH 7.4, 50% acetonitrile, v/v). Copyright © 2013 John Wiley & Sons, Ltd.

  15. Some kinetic and spectroscopic evidence on intramolecular relaxation processes in polyatomic molecules

    International Nuclear Information System (INIS)

    Quack, M.

    1983-01-01

    The description and definition of intramolecular vibrational relaxation processes is discussed within the framework of the quantum mechanical and statistical mechanical equations of motion. The evidence from quite different experimental sources is summarized under the common aspect of vibrational relaxation. Although much of the evidence remains ambiguous, there is good indication that a localized vibrational excitation relaxes typically in 0.1 to 10 picoseconds, which is long compared to many optical and reactive processes

  16. A Concomitant Allylic Azide Rearrangement/Intramolecular Azide–Alkyne Cycloaddition Sequence

    Science.gov (United States)

    2015-01-01

    An intramolecular Huisgen cycloaddition of an interconverting set of isomeric allylic azides with alkynes affords substituted triazoles in high yield. The stereoisomeric vinyl-substituted triazoloxazines formed depend on the rate of cycloaddition of the different allylic azide precursors when the reaction is carried out under thermal conditions. In contrast, dimerized macrocyclic products were obtained when the reaction was done using copper(I)-catalyzed conditions, demonstrating the ability to control the reaction products through changing conditions. PMID:24635056

  17. Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines

    Directory of Open Access Journals (Sweden)

    Karl Hemming

    2014-10-01

    Full Text Available The coupling of proline- and azetidinone-substituted alkenes to 2-azidobenzoic and 2-azidobenzenesulfonic acid gives precursors that undergo intramolecular azide to alkene 1,3-dipolar cycloadditions to give imine-, triazoline- or aziridine-containing pyrrolo[1,4]benzodiazepines (PBDs, pyrrolo[1,2,5]benzothiadiazepines (PBTDs, and azetidino[1,4]benzodiazepines. The imines and aziridines are formed after loss of nitrogen from a triazoline cycloadduct. The PBDs are a potent class of antitumour antibiotics.

  18. Efficient intramolecular cyclizations of phenoxyethynyl diols into multisubstituted α,β-unsaturated lactones.

    Science.gov (United States)

    Egi, Masahiro; Ota, Yuya; Nishimura, Yuka; Shimizu, Kaori; Azechi, Kenji; Akai, Shuji

    2013-08-16

    AgOTf-catalyzed intramolecular cyclization of phenoxyethynyl diols proceeded under mild conditions to afford the multisubstituted α,β-unsaturated-γ-lactones in 55-98% yields. This method was also applicable to the synthesis of α,β-unsaturated-δ-lactones. A similar cyclization proceeded when AgOTf was replaced with a stoichiometric amount of N-bromosuccinimide to furnish the α-bromo-substituted α,β-unsaturated lactones.

  19. An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

    Directory of Open Access Journals (Sweden)

    Zhiyuan Ma

    2012-06-01

    Full Text Available Intramolecular inverse electron demand cycloadditions of isatin-derived 1,2,4-triazines with acetylenic dienophiles tethered by amidations or transesterifications proceed in excellent yields to produce lactam- or lactone-fused α-carbolines. Beginning with various isatins and alkynyl dienophiles, a pilot-scale library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation.

  20. Intramolecular electron transfer through a bridging carboxylate group coordinated to two cobalt(III)-ions

    International Nuclear Information System (INIS)

    Wieghardt, K.

    1978-01-01

    Reduction of the binuclear μ-p-nitrobenzoato -di-μ-hydroxo -bis[triammine cobalt(III)] cation with (CH 3 ) 2 COH radicals yields a radical cation with the p-nitrobenzoato radical being coordinated to two cobalt(III) ions at the carboxylic group. The unprotonated form of this species undergoes intramolecular electron transfer producing Co(II) (k = (3.3 +- 0.3). x 10 3 s -1 ). The role of the carboxylate group in the intramolecular electron transfer process is tentatively assessed in terms of an intramolecular outer-sphere reaction because of lack of overlap of the donor orbitals (π) and the acceptor orbital (sigma). The protonated form of the radical cation (pKsub(a) = 2.5) disproportionates via a bimolecular process without production of Co(II). The effect of two coordinated Co(III) ions as compared to only one on the properties of the nitrobenzoate radical anion are discussed. (orig.) 891 HK 892 GM [de

  1. THE ROLE OF INTRAMOLECULAR TIES ENERGY IN THE PYROLYSIS PROCESS OF PET

    Directory of Open Access Journals (Sweden)

    P. Iu. Salikov

    2014-01-01

    Full Text Available Summary. Recycling plastic waste to focus on. The main type of used products made of polyethylene terephthalate (PET is a container from the various types of beverages. There was considered a possibility of waste of PET (bottles, bottles, packaging containers by pyrolysis. Most of the proposed methods are not suitable for recycling (recycling of waste consumption contamination. Purpose - to develop technological foundations and optimum modes waste PET to obtain useful secondary products, taking into account the energy of chemical intramolecular bonds. Applied scientific basis of recycling PET into useful forms of secondary products, in particular the establishment of the collapse of the intramolecular bonds, depending on the temperature of the pyrolysis method of mathematical processing - differentiation of polynomial equations change in the degree of pyrolysis temperature-dependent. The optimum modes of processing. The block diagram of apparatus for processing contaminated waste PET pyrolysis methods of control processing in accordance with the specified composition of secondary products. The possibility of controlling the amount and types of fuel components of secondary products due to measurable parameters of the pyrolysis process. The effective temperature pyrolysis of waste PET with the CCA-tures energy intramolecular bonds.

  2. Time-Resolved Signatures across the Intramolecular Response in Substituted Cyanine Dyes

    Science.gov (United States)

    Nairat, Muath; Webb, Morgan; Esch, Michael; Lozovoy, Vadim V.; Levine, Benjamin G.; Dantus, Marcos

    2017-06-01

    The optically populated excited state wave packet propagates along multidimensional intramolecular coordinates soon after photoexcitation. This action occurs alongside an intermolecular response from the surrounding solvent. Disentangling the multidimensional convoluted signal enables the possibility to separate and understand the initial intramolecular relaxation pathways over the excited state potential energy surface. Here we track the initial excited state dynamics by measuring the fluorescence yield from the first excited state as a function of time delay between two color femtosecond pulses for several cyanine dyes, having different electronic configurations. We find that when the high frequency pulse precedes the low frequency one and for timescales up to 200 fs, the excited state can be depleted through stimulated emission with efficiency that is dependent on the molecular electronic structure. A similar observation at even shorter times was made by scanning the chirp (frequencies ordering) of a femtosecond pulse. These changes reflect the rate at which the nuclear coordinates of the excited state leave the Franck-Condon (FC) region and progress towards achieving equilibrium. Through functional group substitution, we explore these dynamic changes as a function of dipolar change following photoexcitation. We show that with proper knowledge and control over the phase of the excitation pulses, we can extract the relative energy relaxation rates through which the early intramolecular modes are populated at the FC geometry soon after excitation

  3. Intramolecular stable isotope distributions detect plant metabolic responses on century time scales

    Science.gov (United States)

    Schleucher, Jürgen; Ehlers, Ina; Augusti, Angela; Betson, Tatiana

    2014-05-01

    Plants respond to environmental changes on a vast range of time scales, and plant gas exchanges constitute important feedback mechanisms in the global C cycle. Responses on time scales of decades to centuries are most important for climate models, for prediction of crop productivity, and for adaptation to climate change. Unfortunately, responses on these timescale are least understood. We argue that the knowledge gap on intermediate time scales is due to a lack of adequate methods that can bridge between short-term manipulative experiments (e.g. FACE) and paleo research. Manipulative experiments in plant ecophysiology give information on metabolism on time scales up to years. However, this information cannot be linked to results from retrospective studies in paleo research, because little metabolic information can be derived from paleo archives. Stable isotopes are prominent tools in plant ecophysiology, biogeochemistry and in paleo research, but in all applications to date, isotope ratios of whole molecules are measured. However, it is well established that stable isotope abundance varies among intramolecular groups of biochemical metabolites, that is each so-called "isotopomer" has a distinct abundance. This intramolecular variation carries information on metabolic regulation, which can even be traced to individual enzymes (Schleucher et al., Plant, Cell Environ 1999). Here, we apply intramolecular isotope distributions to study the metabolic response of plants to increasing atmospheric [CO2] during the past century. Greenhouse experiments show that the deuterium abundance among the two positions in the C6H2 group of photosynthetic glucose depends on [CO2] during growth. This is observed for all plants using C3 photosynthesis, and reflects the metabolic flux ratio between photorespiration and photosynthesis. Photorespiration is a major C flux that limits assimilation in C3 plants, which encompass the overwhelming fraction of terrestrial photosynthesis and the

  4. Syntheses of strychnine, norfluorocurarine, dehydrodesacetylretuline, and valparicine enabled by intramolecular cycloadditions of Zincke aldehydes.

    Science.gov (United States)

    Martin, David B C; Nguyen, Lucas Q; Vanderwal, Christopher D

    2012-01-06

    A full account of the development of the base-mediated intramolecular Diels-Alder cycloadditions of tryptamine-derived Zincke aldehydes is described. This important complexity-generating transformation provides the tetracyclic core of many indole monoterpene alkaloids in only three steps from commercially available starting materials and played a key role in short syntheses of norfluorocurarine (five steps), dehydrodesacetylretuline (six steps), valparicine (seven steps), and strychnine (six steps). Reasonable mechanistic possibilities for this reaction, a surprisingly facile dimerization of the products, and an unexpected cycloreversion to regenerate Zincke aldehydes under specific conditions are also discussed.

  5. Deuterium isotope effect on the intramolecular electron transfer in Pseudomonas aeruginosa azurin

    DEFF Research Database (Denmark)

    Farver, O.; Zhang, Jingdong; Chi, Qijin

    2001-01-01

    rather than negative. Isotope effects are, however, also inherent in the nuclear reorganization Gibbs free energy and in the tunneling factor for the electron transfer process. A slightly larger thermal protein expansion in H2O than in D2O (0.001 nm K-1) is sufficient both to account for the activation......Intramolecular electron transfer in azurin in water and deuterium oxide has been studied over a broad temperature range. The kinetic deuterium isotope effect, k(H)/k(D), is smaller than unity (0.7 at 298 K), primarily caused by the different activation entropies in water (-56.5 J K-1 mol(-1...

  6. A concise, efficient synthesis of sugar-based benzothiazoles through chemoselective intramolecular C-S coupling

    KAUST Repository

    Shen, Chao

    2012-01-01

    Sugar-based benzothiazoles are a new class of molecules promising for many biological applications. Here, we have synthesized a wide range of sugar-based benzothiazoles from readily accessible glycosyl thioureas by chemoselective, palladium-catalyzed C-S coupling reactions. Corroborated by theoretical calculations, a mechanistic investigation indicates that the coordination to the palladium by a pivaloyl carbonyl group and the presence of intramolecular hydrogen bonding play important roles in the efficiency and chemoselectivity of reaction. These fluorescent glycoconjugates can be observed to readily enter mammalian tumor cells and exhibit potential in vitro antitumor activity. This journal is © The Royal Society of Chemistry 2012.

  7. Path-integral calculation of the second virial coefficient including intramolecular flexibility effects

    Energy Technology Data Exchange (ETDEWEB)

    Garberoglio, Giovanni, E-mail: garberoglio@fbk.eu [Interdisciplinary Laboratory for Computational Science (LISC), FBK-CMM and University of Trento, via Sommarive 18, I-38123 Povo (Italy); Jankowski, Piotr [Department of Quantum Chemistry, Faculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, PL-87-100 Toruń (Poland); Szalewicz, Krzysztof [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Harvey, Allan H. [Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305-3337 (United States)

    2014-07-28

    We present a path-integral Monte Carlo procedure for the fully quantum calculation of the second molecular virial coefficient accounting for intramolecular flexibility. This method is applied to molecular hydrogen (H{sub 2}) and deuterium (D{sub 2}) in the temperature range 15–2000 K, showing that the effect of molecular flexibility is not negligible. Our results are in good agreement with experimental data, as well as with virials given by recent empirical equations of state, although some discrepancies are observed for H{sub 2} between 100 and 200 K.

  8. Dynamics of excited-state intramolecular proton transfer reactions in piroxicam. Role of triplet states

    Science.gov (United States)

    Cho, Dae Won; Kim, Yong Hee; Yoon, Minjoong; Jeoung, Sae Chae; Kim, Dongho

    1994-08-01

    The picosecond time-resolved fluorescence and transient absorption behavior of piroxicam at room temperature are reported. The keto tautomer in the excited singlet state ( 1K*) formed via the fast intramolecular proton transfer (≈ 20 ps) is observed. The short-lived (7.5 ns) triplet state of keto tauomer ( 3K*) is generated from 1K * in toluene whereas it is hardly observed in ethanol. Consequently, rapid reverse proton transfer takes place from 3K * to the enol triplet state ( 3E *.

  9. The Preparation and Intramolecular Radical Cyclisation Reactions of Chiral Oxime Ethers

    Directory of Open Access Journals (Sweden)

    Booth Susan E.

    1998-01-01

    Full Text Available Chiral oxime ether 2 and Oxime ester 4 have been prepared by alkylation and esterification of the oxime 1. Racemic hydroxylamine 6 and chiral hydroxylamine 10 have been synthesised from N-hydroxysuccinimide and the corresponding alcohol in the presence of diethylazodicarboxylate, the two products were converted into the oxime ethers 7 and 11 respectively. The intramolecular radical cyclisation reactions of these oxime ethers and esters has been studied, successful reaction was observed to produce alkyl hydroxylamines 3, 8 and 12.

  10. Some Brief Notes on Theoretical and Experimental Investigations of Intramolecular Hydrogen Bonding

    Directory of Open Access Journals (Sweden)

    Lucjan Sobczyk

    2016-12-01

    Full Text Available A review of selected literature data related to intramolecular hydrogen bonding in ortho-hydroxyaryl Schiff bases, ortho-hydroxyaryl ketones, ortho-hydroxyaryl amides, proton sponges and ortho-hydroxyaryl Mannich bases is presented. The paper reports on the application of experimental spectroscopic measurements (IR and NMR and quantum-mechanical calculations for investigations of the proton transfer processes, the potential energy curves, tautomeric equilibrium, aromaticity etc. Finally, the equilibrium between the intra- and inter-molecular hydrogen bonds in amides is discussed.

  11. Use of ionic model for analysis of intramolecular movement in alkali metal metaborate molecules

    International Nuclear Information System (INIS)

    Ezhov, Yu.S.; Vinogradov, V.S.

    1978-01-01

    To clear out the peculiarities of intramolecular movement in MBO 2 (where M=Li, Na, K, Rb, Cs) molecules the energy dependence of cation electrostatic interaction with BO 2 anion on the charge value of oxygen, values of the MOB valence angle and internuclear distance r(M-O) is calculated. The calculation results on the base of ionic model show that the minimum of potential energy function corresponds to angular configuration of the MBO 2 molecules. Parameters of potential function of deformation oscillation connected with the change of MOB angle, are evaluated

  12. Samarium(II) iodide-mediated intramolecular conjugate additions of alpha,beta-unsaturated lactones.

    Science.gov (United States)

    Molander, Gary A; St Jean, David J

    2002-05-31

    Samarium(II) iodide, in the presence of catalytic amounts of nickel(II) iodide, has been used to promote intramolecular conjugate additions of alkyl halides onto alpha,beta-unsaturated lactones. This process has been shown to be applicable to a number of alpha,beta-unsaturated lactones, including tetrasubstituted olefins, and has been demonstrated to be quite general for the formation of saturated bicyclic and tricyclic lactones. The method presented herein provides a mild, efficient process to form structurally complex lactones from simple precursors.

  13. Intramolecular hydrogen bond in molecular and proton-transfer forms of Schiff bases

    Energy Technology Data Exchange (ETDEWEB)

    Filarowski, A.; Koll, A.; Karpfen, A.; Wolschann, P

    2004-02-16

    The force field and structural parameters modifications upon the formation of intramolecular hydrogen bond and proton transfer reaction in N-methyl-2-hydroxybenzylidene amine (HBZA) are determined on the basis of ab initio and DFT calculations. Reliability of the calculations is verified by comparing of the theoretical vibrational spectra with those experimentally determined in the gas phase. A model of resonance interactions is applied and the quantitative contribution of ortho-quinoid structure in the particular conformers is estimated. A comparison is also made to the systems without {pi}-electron coupling (Mannich bases)

  14. Cooperative Metal–Ligand Catalyzed Intramolecular Hydroamination and Hydroalkoxylation of Allenes Using a Stable Iron Catalyst

    KAUST Repository

    El-Sepelgy, Osama

    2018-01-18

    A new iron-catalyzed chemoselective intramolecular hydroamination and hydroalkoxylation of the readily available α-allenic amines and alcohols to valuable unsaturated 5-membered heterocycles, 2,3-dihydropyrrole and 2,3-dihydrofuran, is reported. Effective selectivity control is achieved by a metal–ligand cooperative activation of the substrates. The mild reaction conditions and the use of low amounts of an air and moisture stable iron catalyst allow for the hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.

  15. Pulse radiolytic and electrochemical investigations of intramolecular electron transfer in carotenoporphyrins and carotenoporphyrin-quinone triads

    International Nuclear Information System (INIS)

    Land, E.J.; Lexa, D.; Bensasson, R.V.; Gust, D.; Moore, T.A.; Moore, A.L.; Liddell, P.A.; Nemeth, G.A.

    1987-01-01

    Thermodynamic and kinetic aspects of intramolecular electron-transfer reactions in carotenoporphyrin dyads and carotenoid-porphyrin-quinone triads have been studied by using pulse radiolysis and cyclic voltammetry. Rapid (<1 μs) electron transfer from carotenoid radical anions to attached porphyrins has been inferred. Carotenoid cations, on the other hand, do not readily accept electrons from attached porphyrins or pyropheophorbides. Electrochemical studies provide the thermodynamic basis for these observations and also allow estimation of the energetics of photoinitiated two-step electron transfer and two-step charge recombination in triad models for photosynthetic charge separation

  16. Approach to Interfacial and Intramolecular Electron Transfer of the Diheme Protein Cytochrome c(4) Assembled on Au(111) Surfaces

    DEFF Research Database (Denmark)

    Chi, Qijin; Zhang, Jingdong; Taner, Arslan

    2010-01-01

    protein Pseudomonas stutzeri cytochrome c(4) has been a target for intramolecular, interheme ET. We report here voltammetric and in situ scanning tunneling microscopy (STM) data for P. stutzeri cyt c(4) at single-crystal, atomically planar Au(111)-electrode surfaces modified by variable-length omega...... direction and a single two-ET peak in the anodic direction. Intramolecular, interheme ET with high, 8,000-30,000 s(-1), rate constants is notably an essential part of this mechanism. The high rate constants are in striking contrast to ET reactions of P. stutzeri cyt c4 with small reaction partners...... in homogeneous solution for which kinetic analysis clearly testifies to electrostatic cooperative effects but no intramolecular, interheme ET higher than 0.1-10 s(-1). This difference suggests a strong gating feature of the process. On the basis of the three-dimensional structure of P. stutzeri cyt c(4), gating...

  17. Intramolecular Hydrogen Bonding Involving Organic Fluorine: NMR Investigations Corroborated by DFT-Based Theoretical Calculations

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar Mishra

    2017-03-01

    Full Text Available The combined utility of many one and two dimensional NMR methodologies and DFT-based theoretical calculations have been exploited to detect the intramolecular hydrogen bond (HB in number of different organic fluorine-containing derivatives of molecules, viz. benzanilides, hydrazides, imides, benzamides, and diphenyloxamides. The existence of two and three centered hydrogen bonds has been convincingly established in the investigated molecules. The NMR spectral parameters, viz., coupling mediated through hydrogen bond, one-bond NH scalar couplings, physical parameter dependent variation of chemical shifts of NH protons have paved the way for understanding the presence of hydrogen bond involving organic fluorine in all the investigated molecules. The experimental NMR findings are further corroborated by DFT-based theoretical calculations including NCI, QTAIM, MD simulations and NBO analysis. The monitoring of H/D exchange with NMR spectroscopy established the effect of intramolecular HB and the influence of electronegativity of various substituents on the chemical kinetics in the number of organic building blocks. The utility of DQ-SQ technique in determining the information about HB in various fluorine substituted molecules has been convincingly established.

  18. Organometallic copper I, II or III species in an intramolecular dechlorination reaction

    KAUST Repository

    Poater, Albert

    2013-03-15

    The present paper gives insight into an intramolecular dechlorination reaction involving Copper (I) and an ArCH2Cl moiety. The discussion of the presence of a CuIII organometallic intermediate becomes a challenge, and because of the lack of clear experimental detection of this proposed intermediate, and due to the computational evidence that it is less stable than other isomeric species, it can be ruled out for the complex studied here. Our calculations are completely consistent with the key hypothesis of Karlin et al. that TMPA-CuI is the substrate of intramolecular dechlorination reactions as well as the source to generate organometallic species. However the organometallic character of some intermediates has been refused because computationally these species are less stable than other isomers. Thus this study constitutes an additional piece towards the full understanding of a class of reaction of biological relevance. Further, the lack of high energy barriers and deep energy wells along the reaction pathway explains the experimental difficulties to trap other intermediates. © Springer-Verlag Berlin Heidelberg 2013.

  19. Effect of Hartree-Fock exact exchange on intramolecular magnetic coupling constants of organic diradicals.

    Science.gov (United States)

    Cho, Daeheum; Ko, Kyoung Chul; Ikabata, Yasuhiro; Wakayama, Kazufumi; Yoshikawa, Takeshi; Nakai, Hiromi; Lee, Jin Yong

    2015-01-14

    The intramolecular magnetic coupling constant (J) of diradical systems linked with five- or six-membered aromatic rings was calculated to obtain the scaling factor (experimental J/calculated J ratio) for various density functional theory (DFT) functionals. Scaling factors of group A (PBE, TPSSh, B3LYP, B97-1, X3LYP, PBE0, and BH&HLYP) and B (M06-L, M06, M06-2X, and M06-HF) were shown to decrease as the amount of Hartree-Fock exact exchange (HFx) increases, in other words, overestimation of calculated J becomes more severe as the HFx increases. We further investigated the effect of HFx fraction of DFT functional on J value, spin contamination, and spin density distributions by comparing the B3LYP analogues containing different amount of HFx. It was revealed that spin contamination and spin densities at each atom increases as the HFx increases. Above all, newly developed BLYP-5 functional, which has 5% of HFx, was found to have the scaling factor of 1.029, indicating that calculated J values are very close to that of experimental values without scaling. BLYP-5 has potential to be utilized for accurate evaluation of intramolecular magnetic coupling constant (J) of diradicals linked by five- or six-membered aromatic ring couplers.

  20. Discovery of intramolecular signal transduction network based on a new protein dynamics model of energy dissipation.

    Directory of Open Access Journals (Sweden)

    Cheng-Wei Ma

    Full Text Available A novel approach to reveal intramolecular signal transduction network is proposed in this work. To this end, a new algorithm of network construction is developed, which is based on a new protein dynamics model of energy dissipation. A key feature of this approach is that direction information is specified after inferring protein residue-residue interaction network involved in the process of signal transduction. This enables fundamental analysis of the regulation hierarchy and identification of regulation hubs of the signaling network. A well-studied allosteric enzyme, E. coli aspartokinase III, is used as a model system to demonstrate the new method. Comparison with experimental results shows that the new approach is able to predict all the sites that have been experimentally proved to desensitize allosteric regulation of the enzyme. In addition, the signal transduction network shows a clear preference for specific structural regions, secondary structural types and residue conservation. Occurrence of super-hubs in the network indicates that allosteric regulation tends to gather residues with high connection ability to collectively facilitate the signaling process. Furthermore, a new parameter of propagation coefficient is defined to determine the propagation capability of residues within a signal transduction network. In conclusion, the new approach is useful for fundamental understanding of the process of intramolecular signal transduction and thus has significant impact on rational design of novel allosteric proteins.

  1. Dynamic intramolecular regulation of the histone chaperone nucleoplasmin controls histone binding and release.

    Science.gov (United States)

    Warren, Christopher; Matsui, Tsutomu; Karp, Jerome M; Onikubo, Takashi; Cahill, Sean; Brenowitz, Michael; Cowburn, David; Girvin, Mark; Shechter, David

    2017-12-20

    Nucleoplasmin (Npm) is a highly conserved histone chaperone responsible for the maternal storage and zygotic release of histones H2A/H2B. Npm contains a pentameric N-terminal core domain and an intrinsically disordered C-terminal tail domain. Though intrinsically disordered regions are common among histone chaperones, their roles in histone binding and chaperoning remain unclear. Using an NMR-based approach, here we demonstrate that the Xenopus laevis Npm tail domain controls the binding of histones at its largest acidic stretch (A2) via direct competition with both the C-terminal basic stretch and basic nuclear localization signal. NMR and small-angle X-ray scattering (SAXS) structural analyses allowed us to construct models of both the tail domain and the pentameric complex. Functional analyses demonstrate that these competitive intramolecular interactions negatively regulate Npm histone chaperone activity in vitro. Together these data establish a potentially generalizable mechanism of histone chaperone regulation via dynamic and specific intramolecular shielding of histone interaction sites.

  2. EVAPORATION: a new vapour pressure estimation methodfor organic molecules including non-additivity and intramolecular interactions

    Directory of Open Access Journals (Sweden)

    S. Compernolle

    2011-09-01

    Full Text Available We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects, a method to predict (subcooled liquid pure compound vapour pressure p0 of organic molecules that requires only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log10p0(T is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: aldehydes, ketones, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA.

  3. The role of hydrogen bonding in excited state intramolecular charge transfer.

    Science.gov (United States)

    Chipem, Francis A S; Mishra, Anasuya; Krishnamoorthy, G

    2012-07-07

    Intramolecular charge transfer (ICT) that occurs upon photoexcitation of molecules is a vital process in nature and it has ample applications in chemistry and biology. The ICT process of the excited molecules is affected by several environmental factors including polarity, viscosity and hydrogen bonding. The effect of polarity and viscosity on the ICT processes is well understood. But, despite the fact that hydrogen bonding significantly influences the ICT process, the specific role of hydrogen bonding in the formation and stabilization of the ICT state is not unambiguously established. Some literature reports predicted that the hydrogen bonding of the solvent with a donor promotes the formation of a twisted intramolecular charge transfer (TICT) state. Some other reports stated that it inhibits the formation of the TICT state. Alternatively, it was proposed that the hydrogen bonding of the solvent with an acceptor favors the TICT state. It is also observed that a dynamic equilibrium is established between the free and the hydrogen bonded ICT states. This perspective focuses on the specific role played by hydrogen bonding of the solvent with the donor and the acceptor, and by proton transfer in the ICT process. The utility of such influence in molecular recognition and anion sensing is discussed with a few recent literature examples in the end.

  4. Visible absorbing croconium dyes with intramolecular hydrogen bonding: A combined experimental and computational study

    Science.gov (United States)

    Prabhakar, Ch.; Promila; Tripathi, Anuj; Bhanuprakash, K.; Jayathirtharao, V.

    2017-10-01

    Croconium molecules CR1-CR4 with break-in conjugation (Csbnd N Bonding) was synthesized by condensation of croconic acid and arylamines. By using combined experimental and theoretical methods like UV-visible spectra, DFT and TDDFT studies, we have characterized electronic absorption properties. The reported molecules are having absorption in visible region ranging from 450 to 550 nm with large extinction coefficient (2.5-5.0 × 104 M-1 cm-1). We find that CR2 and CR4 are showing 50 to 100 nm red shifted absorption than CR1 and CR3. This red shift is possibly due to presence of intramolecular hydrogen bonding in CR2 and CR4. Further this is supported by DFT studies, in case of CR2 and CR4 shows strong intramolecular hydrogen bonding between oxygen of carboxylate group (at ortho position of phenyl ring) and hydrogen of nitrogen attached to the central croconate ring. It is also observed that, there is small diradicaloid character in these molecules. This study is helpful in design and synthesis of new croconium dyes which are useful in materials applications.

  5. Regioselective Synthesis of Procyanidin B6, A 4-6-Condensed (+-Catechin Dimer, by Intramolecular Condensation

    Directory of Open Access Journals (Sweden)

    Yusuke Higashino

    2018-01-01

    Full Text Available Proanthocyanidins, also known as condensed tannins or oligomeric flavonoids, are found in many edible plants and exhibit interesting biological activities. Herein, we report a new, simple method for the stereoselective synthesis of procyanidin B6, a (+-catechin-(4-6-(+-catechin dimer, by Lewis acid-catalyzed intramolecular condensation. The 5-O-t-butyldimethylsilyl (TBDMS group of 5,7,3′4′-tetra-O-TBDMS-(+-catechin was regioselectively removed using trifluoroacetic acid, leading to the “regio-controlled” synthesis of procyanidin B6. The 5-hydroxyl group of the 7,3′,4′-tri-O-TBDMS-(+-catechin nucleophile and the 3-hydroxyl group of 5,7,3′,4′-tetra-O-benzylated-(+-catechin electrophile were connected with an azelaic acid. The subsequent SnCl4-catalyzed intramolecular condensation proceeded smoothly to give the 4-6-condensed catechin dimer. This is the first report on the complete regioselective synthesis of a 4-6-connected oligomer without modifying the 8-position.

  6. Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view

    Science.gov (United States)

    Chen, Yu-Chun; Tang, Ping-Han; Wu, Ten-Ming

    2013-11-01

    By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given.

  7. Redox-Tag Processes: Intramolecular Electron Transfer and Its Broad Relationship to Redox Reactions in General.

    Science.gov (United States)

    Okada, Yohei; Chiba, Kazuhiro

    2017-12-08

    Explosive growth in the use of open shell reactivity, including neutral radicals and radical ions, in the field of synthetic organic chemistry has been observed in the past decade, particularly since the advent of ruthenium complexes in 2008. These complexes generally induce single-electron transfer (SET) processes via visible-light absorption. Additionally, recent significant advancements in organic electrochemistry involving SET processes to provide open shell reactivity offer a complementary method to traditional polarity-driven reactions described by two-electron transfer processes. In this Review, we highlight the importance of intramolecular SET processes in the field of synthetic organic chemistry, which seem to be more elusive than the intermolecular versions, since they are net redox-neutral and thus cannot simply be regarded as oxidations or reductions. Such intramolecular SET processes can rationally be understood in combination with concomitant bond formations and/or cleavages, and are regulated by a structural motif that we call a "redox tag." In order to describe modern radical-driven reactions involving SET processes, we focus on a classical formalism in which electrons are treated as particles rather than waves, which offers a practical yet powerful approach to explain and/or predict synthetic outcomes.

  8. Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view.

    Science.gov (United States)

    Chen, Yu-Chun; Tang, Ping-Han; Wu, Ten-Ming

    2013-11-28

    By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given.

  9. Vibrational Spectroscopy of Intramolecular Hydrogen Bonds in the Infrared and Near-Infrared Regions

    DEFF Research Database (Denmark)

    Schrøder, Sidsel Dahl

    and 1,4-diaminobutane). Experimentally, the hydrogen bonds have been studied with vibrational spectroscopy in the infrared and near-infrared regions. The focus is primarily on spectra recorded in the near-infrared regions, which in these studies are dominated by O-H and N-H stretching overtones....... Overtone spectra have been recorded with intracavity laser photoacoustic laser spectroscopy and conventional long path absorption spectroscopy. Theoretically, a combination of electronic structure calculations and local mode models have been employed to guide the assignment of bands in the vibrational......,4-diaminobutane, no sign of intramolecular N-H···N hydrogen bonds were identified in the overtone spectra. However, theoretical analyzes indicate that intramolecular N-H···N hydrogen bonds are present in all three diamines if two hydrogen atoms on one of the methylene groups are substituted with triuoromethyl...

  10. On the nature of intramolecular vibrational energy transfer in dense molecular environments

    Energy Technology Data Exchange (ETDEWEB)

    Benten, Rebekka S. von [Institut fuer Physikalische Chemie der Universitaet Goettingen, Tammannstrasse 6, D-37077 Goettingen (Germany); Abel, Bernd, E-mail: Bernd.Abel@uni-lepzig.de [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Universitaet Leipzig, Linne-Strasse 2, D-04103 Leipzig (Germany)

    2010-12-09

    Graphical abstract: Mechanisms of IVR in multi-tiers of intramolecular energy levels in different molecular environments are investigated. - Abstract: Transient femtosecond-IR-pump-UV-absorption probe-spectroscopy has been employed to shed light on the nature of intramolecular vibrational energy transfer (IVR) in dense molecular environments ranging from the diluted gas phase to the liquid. A general feature in our experiments and those of others is that IVR proceeds via multiple timescales if overtones or combination vibrations of high frequency modes are excited. It has been found that collisions enhance IVR if its (slower) timescales can compete with collisions. This enhancement is, however, much more weaker and rather inefficient as opposed to the effect of collisions on intermolecular energy transfer which is well known. In a series of experiments we found that IVR depends not significantly on the average energy transferred in a collision but rather on the number of collisions. The collisions are much less efficient in affecting IVR than VET. We conclude that collision induced broadening of vibrational energy levels reduces the energy gaps and enhances existing couplings between tiers. The present results are an important step forward to rationalize and understand apparently different and not consistent results from different groups on different molecular systems between gas and liquid phases.

  11. Multiwall nanotubes with intramolecular junctions (CNx/C): Preparation, rectification, logic gates, and application

    Science.gov (United States)

    Hu, Ping'an; Xiao, Kai; Liu, Yunqi; Yu, Gui; Wang, Xianbao; Fu, Lei; Cui, Guanglei; Zhu, Daoben

    2004-06-01

    We prepared a large quantity of multiwall nanotubes with intramolecular junctions (CNx/C) by pyrolysis of iron phthalocyanine with or without an inlet of ammonia gas. The nanotubes consist of two sections, one section made of carbon nitride featuring bamboo-like structure and the other one made of carbon featuring empty hollow cylinder structure, and thus the intramolecular junctions were formed in the middle as a result of being doped or undoped with nitrogen. Nanodiode based on a single CNx/C junction shows reproducible rectifying behavior with a rectification ratio of 1.3×103 at ±2 V. In addition, the nanodiode demonstrated as a half-wave rectifier worked at an input sine wave of 1 kHz. Two CNx/C junctions were configured together to exhibit functions of OR and AND logic gates. Moreover, after substituting the wave-detection silicon diode in common transistor radio set with our nanodiode, the radio set still worked normally, representing an important step toward the potential application for nano-scale devices.

  12. An excited-state intramolecular photon transfer fluorescence probe for localizable live cell imaging of cysteine

    Science.gov (United States)

    Liu, Wei; Chen, Wen; Liu, Si-Jia; Jiang, Jian-Hui

    2017-03-01

    Small molecule probes suitable for selective and specific fluorescence imaging of some important but low-concentration intracellular reactive sulfur species such as cysteine (Cys) pose a challenge in chemical biology. We present a readily available, fast-response fluorescence probe CHCQ-Ac, with 2-(5‧-chloro-2-hydroxyl-phenyl)-6-chloro-4(3 H)-quinazolinone (CHCQ) as the fluorophore and acrylate group as the functional moiety, that enables high-selectivity and high-sensitivity for detecting Cys in both solution and biological system. After specifically reacted with Cys, the probe undergoes a seven-membered intramolecular cyclization and released the fluorophore CHCQ with excited-state intramolecular photon transfer effect. A highly fluorescent, insoluble aggregate was then formed to facilitate high-sensitivity and high-resolution imaging. The results showed that probe CHCQ-Ac affords a remarkably large Stokes shift and can detect Cys under physiological pH condition with no interference from other analytes. Moreover, this probe was proved to have excellent chemical stability, low cytotoxicity and good cell permeability. Our design of this probe provides a novel potential tool to visualize and localize cysteine in bioimaging of live cells that would greatly help to explore various Cys-related physiological and pathological cellular processes in cell biology and diagnostics.

  13. Estimating the energy of intramolecular hydrogen bonds from1H NMR and QTAIM calculations.

    Science.gov (United States)

    Afonin, Andrei V; Vashchenko, Alexander V; Sigalov, Mark V

    2016-11-29

    The values of the downfield chemical shift of the bridge hydrogen atom were estimated for a series of compounds containing an intramolecular hydrogen bond O-HO, O-HN, O-HHal, N-HO, N-HN, C-HO, C-HN and C-HHal. Based on these values, the empirical estimation of the hydrogen bond energy was obtained by using known relationships. For the compounds containing an intramolecular hydrogen bond, the DFT B3LYP/6-311++G(d,p) method was used both for geometry optimization and for QTAIM calculations of the topological parameters (electron density ρ BCP and the density of potential energy V in the critical point of the hydrogen bond). The calculated geometric and topological parameters of hydrogen bonds were also used to evaluate the energy of the hydrogen bond based on the equations from the literature. Comparison of calibrating energies from the 1 H NMR data with the energies predicted by calculations showed that the most reliable are the linear dependence on the topological ρ BCP and V parameters. However, the correct prediction of the hydrogen bond energy is determined by proper fitting of the linear regression coefficients. To obtain them, new linear relationships were found between the calculated ρ BCP and V parameters and the hydrogen bond energies obtained from empirical 1 H NMR data. These relationships allow the comparison of the energies of different types of hydrogen bonds for various molecules and biological ensembles.

  14. Characteristics of Intramolecular Charge Transfer by J-Aggregates in Merocyanine Dye LB Films.

    Science.gov (United States)

    Yang, Chang Heon; Kwon, Young-Soo; Shin, Hoon-Kyu

    2016-06-01

    In this study, for the development of future molecular electronic devices, we have investigated the characteristics of the aggregates of Langmuir-Blodgett films. The characteristics of intramolecular charge transfer by J-aggregates in merocyanine dye LB films have been studied experimentally by using UV irradiation and heat treatment. In addition to intramolecular charge transfer, we also studied the conjugation and energy changes of the molecules. In case a dye is thinned by LB method, the alkyl chain is often displaced in order to form a mono-molecular film with ease. Since the molecular association form is often made by self-organization of molecules themselves, in case the dye and the alkyl chain are strongly bonded by the covalent bond, it may be said that the properties of the LB film to be built up are almost determined at the time of synthesis of film-forming molecules. Meanwhile, since, in case LB film is fabricated by the diffusion absorption method, the cohesive force between the water-soluble dye and the surface-active mono-molecular film is electrostatic, the dye molecule can move relatively freely on the air/water interface, which may be regarded as a two-dimensional crystal growth process.

  15. Intramolecular proton transfer and tunnelling reactions of hydroxyphenylbenzoxazole derivatives in Xenon at 15 K

    Energy Technology Data Exchange (ETDEWEB)

    Walla, Peter J. [Max-Planck-Institute for Biophysical Chemistry, Department 010, Spectroscopy and Photochemical Kinetics, Am Fassberg 11, D-37077 Goettingen (Germany) and Department for Biophysical Chemistry, Technical University of Brunswick, Institute for Physical and Theoretical Chemistry, Hans-Sommerstr. 10, D-38106 Braunschweig (Germany)]. E-mail: pwalla@gwdg.de; Nickel, Bernhard [Max-Planck-Institute for Biophysical Chemistry, Department 010, Spectroscopy and Photochemical Kinetics, Am Fassberg 11, D-37077 Goettingen (Germany)

    2005-06-06

    We investigated the site dependence and the tunnelling processes of the intramolecular proton and deuteron transfer in the triplet state of the compounds 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and 2-(2'-hydroxy-3'-methylphenyl)benzoxazoles (o-MeHBO) and their deuterio-oxy analogues in a solid xenon matrix. After singlet excitation there occurs an ultrafast intramolecular enol {yields} keto proton transfer and subsequent intersystem crossing mainly to the keto triplet state. In the triplet state of m-MeHBO, the proton transfer back to the lower enol triplet state is governed by tunnelling processes. In o-MeHBO, however, the enol triplet state is higher and therefore normally no tunnel reaction can be observed. Because of the external heavy atom-effect in a xenon matrix, we were able to investigate the reverse enol-keto-tunnelling after exciting directly the enol triplet state of deuterated o-MeHBO. The time constants of the reverse enol-keto tautomerization are similar to those of the normal keto-enol tautomerization. In a xenon matrix, the observed site-selective phosphorescence spectra are very well-resolved vibrationally. This allowed the study of the tunnel rates in different well-defined sites. The vibrational energies obtained in the spectra are in good agreement with vibrational energies found in resonant Raman and IR spectra of 2-(2'-hydroxyphenyl)benzoxazole (HBO)

  16. Hydroxyalkoxy radicals: importance of intramolecular hydrogen bonding on chain branching reactions in the combustion and atmospheric decomposition of hydrocarbons.

    Science.gov (United States)

    Davis, Alexander C; Francisco, Joseph S

    2014-11-20

    During both the atmospheric oxidation and combustion of volatile organic compounds, sequential addition of oxygen can lead to compounds that contain multiple hydrogen-bonding sites. The presence of two or more of these sites on a hydrocarbon introduces the possibility of intramolecular H-bonding, which can have a stabilizing effect on the reactants, products, and transition states of subsequent reactions. The present work compares the absolute energies of two sets of conformations, those that contain intramolecular H-bonds and those that lack intramolecular H-bonds, for each reactant, product, and transition state species in the 1,2 through 1,7 H-migrations and Cα-Cβ, Cα-H, and Cα-OH-bond scission reactions in the n-hydroxyeth-1-oxy through n-hydroxyhex-1-oxy radicals, for n ranging from 1 to 6. The difference in energy between the two conformations represents the balance between the stabilizing effects of H-bonds and the steric cost of bringing the two H-bonding sites together. The effect of intramolecular H-bonding and the OH group is assessed by comparing the net intramolecular H-bond stabilization energies, the reaction enthalpies, and barrier heights of the n-hydroxyalkoxy radical reactions with the corresponding alkoxy radicals values. The results suggest that there is a complex dependence on the location of the two H-bonding groups, the location of the abstraction or bond scission, and the shape of the transition state that dictates the extent to which intramolecular H-bonding effects the relative importance of H-migration and bond scission reactions for each n-hydroxyalkoxy radical. These findings have important implications for future studies on hydrocarbons with multiple H-bonding sites.

  17. Modeling and computations of the intramolecular electron transfer process in the two-heme protein cytochrome c4

    DEFF Research Database (Denmark)

    Natzmutdinov, Renat R.; Bronshtein, Michael D.; Zinkicheva, Tamara T.

    2012-01-01

    ligands in both low- and high-spin states by structure-optimized DFT. The computations enable estimating the intramolecular reorganization energy of the ET process for different combinations of low- and high-spin heme couples. Environmental reorganization free energies, work terms (‘‘gating’’) and driving...... performed computational modeling of the intramolecular ET process by a combination of density functional theory (DFT) and quantum mechanical charge transfer theory to disclose reasons for this difference. We first address the electronic structures of the model heme core with histidine and methionine axial...

  18. Enantiodivergent synthesis of either enantiomer of ABCDE-ring analogue of antitumor antibiotic fredericamycin A via intramolecular [4 + 2] cycloaddition approach.

    Science.gov (United States)

    Akai, S; Tsujino, T; Fukuda, N; Iio, K; Takeda, Y; Kawaguchi Ki, K; Naka, T; Higuchi, K; Kita, Y

    2001-12-13

    [reaction: see text] An intramolecular enantiodivergent synthesis of both enantiomers of the ABCDE-ring analogue 22 of fredericamycin A is reported. Key steps involve an intramolecular [4 + 2] cycloaddition of 17 and an aromatic Pummerer-type reaction of 19. A lipase-catalyzed enantioselective desymmetrization of prochiral diol 2 using 1-ethoxyvinyl 2-furoate 3 led to the pivotal intermediate (R)-4.

  19. Structural effects on the electronic characteristics of intramolecularly intercalated alkali-rubrene complexes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tsung-Lung, E-mail: quantum@mail.ncyu.edu.tw [Department of Electrophysics, National Chia-Yi University, 300 Hsueh-Fu Road, Chiayi, 60004, Taiwan, ROC (China); Lu, Wen-Cai, E-mail: wencailu@jlu.edu.cn [Laboratory of Fiber Materials and Modern Textile, Growing Base for State Key Laboratory, College of Physics, Qingdao University, Qingdao, Shandong 266071 (China); State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, Jilin 130021 (China)

    2016-11-01

    The geometric and electronic structures of neutral monolithium- and monosodium-rubrene (Li{sub 1} Rub and Na{sub 1} Rub) isomers are investigated and compared with monopotassium-rubrene (K{sub 1} Rub). Based on the alkali binding site, all isomers of these alkali-rubrene complexes can be subdivided into two types: intramolecularly intercalated and extramolecularly adsorbed. The minimum-energy Li{sub 1} Rub and Na{sub 1} Rub are intercalated structures, whereas the minimum-energy K{sub 1} Rub is adsorbed. The fact that the intercalated Li{sub 1} Rub and Na{sub 1} Rub structures are energetically favorable over the adsorbed ones can be explained by two energy rules. First, “double” proximity of the intercalating alkali element to a pair of phenyl side groups enormously reduces the total energy. Second, accommodation of a minuscule intercalant does not significantly deform the carbon frame and, thus, increases the energy only by a small amount. Additionally, the peculiar effects of intramolecular intercalation on the electronic structures of molecules are also studied in this simulation of monoalkali intercalation. In the monoalkali-intercalated rubrene complex, only one of the two pairs of phenyl groups of rubrene is intercalated, intentionally leaving another pair pristine, which facilitates the comparison of electronic structures between the intercalated and pristine pairs of phenyl side groups in a single molecule. The uniformity of chemical environments of the phenyl groups of the intercalated Li{sub 1} Rub/Na{sub 1} Rub is deteriorated by the incorporation of the intercalant, and leads to their spectral characteristics in contrast to K{sub 1} Rub. In particular, the introduction of the intercalant promotes the carbon 2p orbitals of the intercalated phenyl pair to take part in the electronic structures of the HOMO and LUMO peaks of Li{sub 1} Rub/Na{sub 1} Rub. The unpaired electron in the HOMO is delocalized over the backbone with higher probability of

  20. Structural effects on the electronic characteristics of intramolecularly intercalated alkali-rubrene complexes

    International Nuclear Information System (INIS)

    Li, Tsung-Lung; Lu, Wen-Cai

    2016-01-01

    The geometric and electronic structures of neutral monolithium- and monosodium-rubrene (Li 1 Rub and Na 1 Rub) isomers are investigated and compared with monopotassium-rubrene (K 1 Rub). Based on the alkali binding site, all isomers of these alkali-rubrene complexes can be subdivided into two types: intramolecularly intercalated and extramolecularly adsorbed. The minimum-energy Li 1 Rub and Na 1 Rub are intercalated structures, whereas the minimum-energy K 1 Rub is adsorbed. The fact that the intercalated Li 1 Rub and Na 1 Rub structures are energetically favorable over the adsorbed ones can be explained by two energy rules. First, “double” proximity of the intercalating alkali element to a pair of phenyl side groups enormously reduces the total energy. Second, accommodation of a minuscule intercalant does not significantly deform the carbon frame and, thus, increases the energy only by a small amount. Additionally, the peculiar effects of intramolecular intercalation on the electronic structures of molecules are also studied in this simulation of monoalkali intercalation. In the monoalkali-intercalated rubrene complex, only one of the two pairs of phenyl groups of rubrene is intercalated, intentionally leaving another pair pristine, which facilitates the comparison of electronic structures between the intercalated and pristine pairs of phenyl side groups in a single molecule. The uniformity of chemical environments of the phenyl groups of the intercalated Li 1 Rub/Na 1 Rub is deteriorated by the incorporation of the intercalant, and leads to their spectral characteristics in contrast to K 1 Rub. In particular, the introduction of the intercalant promotes the carbon 2p orbitals of the intercalated phenyl pair to take part in the electronic structures of the HOMO and LUMO peaks of Li 1 Rub/Na 1 Rub. The unpaired electron in the HOMO is delocalized over the backbone with higher probability of distributing over the central two fused rings than over the outer two

  1. Intramolecular Valence and Spin Interaction in meso and rac Diastereomers of a p-Quinonoid-Bridged Diruthenium Complex

    Czech Academy of Sciences Publication Activity Database

    Kumbhakar, D.; Sarkar, B.; Maji, S.; Mobin, S. M.; Fiedler, Jan; Urbanos, F. A.; Jimenez-Aparicio, R.; Kaim, W.; Lahiri, G. K.

    2008-01-01

    Roč. 130, č. 51 (2008), s. 17575-17583 ISSN 0002-7863 R&D Projects: GA MŠk OC 139; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : intramolecular valence * spin interaction * diruthenium complex Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.091, year: 2008

  2. On Hydrogen Bonding in the Intramolecularly Chelated Taitomers of Enolic Malondialdehyde and its Mono- and Dithio-Analogues

    DEFF Research Database (Denmark)

    Carlsen, Lars; Duus, Fritz

    1980-01-01

    The intramolecular hydrogen bondings in enolic malondialdehyde and it mono- and dithio-analogues have been evaluated by a semiempricial SCF–MO–CNDO method. The calculations predict that the hydrogen bonds play an important part in the stabilities of malondialdehyde and monothiomalondialdehyde...

  3. Modeling and computations of the intramolecular electron transfer process in the two-heme protein cytochrome c4

    DEFF Research Database (Denmark)

    Natzmutdinov, Renat R.; Bronshtein, Michael D.; Zinkicheva, Tamara T.

    2012-01-01

    The di-heme protein Pseudomonas stutzeri cytochrome c4 (cyt c4) has emerged as a useful model for studying long-range protein electron transfer (ET). Recent experimental observations have shown a dramatically different pattern of intramolecular ET between the two heme groups in different local...

  4. Enantioselective synthesis of benzofurans and benzoxazines via an olefin cross-metathesis-intramolecular oxo-Michael reaction.

    Science.gov (United States)

    Zhang, Jun-Wei; Cai, Quan; Gu, Qing; Shi, Xiao-Xin; You, Shu-Li

    2013-09-11

    Chiral phosphoric acid and Hoveyda-Grubbs II were found to catalyze an olefin cross-metathesis-intramolecular oxo-Michael cascade reaction of the ortho-allylphenols and enones to provide a variety of benzofuran and benzoxazine derivatives in moderate to good yields and enantioselectivity.

  5. The effect of driving force on intramolecular electron transfer in proteins. Studies on single-site mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; van de Kamp, M

    1992-01-01

    An intramolecular electron-transfer process has previously been shown to take place between the Cys3--Cys26 radical-ion (RSSR-) produced pulse radiolytically and the Cu(II) ion in the blue single-copper protein, azurin [Farver, O. & Pecht, I. (1989) Proc. Natl Acad. Sci. USA 86, 6868-6972]. To fu...

  6. Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Andy; Bergman, Robert; Ellman, Jonathan

    2008-02-18

    An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.

  7. Environment-sensitive quinolone demonstrating long-lived fluorescence and unusually slow excited-state intramolecular proton transfer kinetics

    Czech Academy of Sciences Publication Activity Database

    Zamotaiev, O. M.; Shvadchak, Volodymyr; Sych, T. P.; Melnychuk, N. A.; Yushchenko, Dmytro A.; Mely, Y.; Pivovarenko, V. G.

    2016-01-01

    Roč. 4, č. 3 (2016), č. článku 034004. ISSN 2050-6120 Institutional support: RVO:61388963 Keywords : quinolone * fluorescent probes * local polarity * hydration * excited-state intramolecular proton transfer * kinetics Subject RIV: CC - Organic Chemistry Impact factor: 2.656, year: 2016

  8. Bifunctional ferrocene-based squaramide-phosphine as an organocatalyst for highly enantioselective intramolecular Morita-Baylis-Hillman reaction.

    Science.gov (United States)

    Zhang, Xiaorui; Ma, Pengfei; Zhang, Dongxu; Lei, Yang; Zhang, Shengyong; Jiang, Ru; Chen, Weiping

    2014-04-21

    This work demonstrates that, in accord with metal catalysis, ferrocene could be an excellent scaffold for organocatalysts. The simple and easily accessible bifunctional ferrocene-based squaramide-phosphine shows high enantioselectivity in the intramolecular Morita-Baylis-Hillman reaction of 7-aryl-7-oxo-5-heptenals, giving a variety of 2-aroyl-2-cyclohexenols in up to 96% ee.

  9. Intramolecular TAT triplex in (dA).sub.58. (dT).sub.58. Influence of ions

    Czech Academy of Sciences Publication Activity Database

    Pečinka, Petr; Huertas, D.; Azorín, F.; Paleček, Emil

    1995-01-01

    Roč. 13, č. 1 (1995), s. 029-046 ISSN 0739-1102 R&D Projects: GA AV ČR IAA504402; GA ČR GA204/93/2336 Keywords : intramolecular triplex * H-DNA * chemical probing * osmium tetroxide complex * DEPC Impact factor: 1.528, year: 1995

  10. Deuterium isotope effect on the intramolecular electron transfer in Pseudomonas aeruginosa azurin

    DEFF Research Database (Denmark)

    Farver, O.; Zhang, Jingdong; Chi, Qijin

    2001-01-01

    -0' is also different, yielding entropy changes of -57 J K-1 mol-l in water and -84 J K-1 mol(-1) in deuterium oxide. The driving force difference of 10 mV is in keeping with the kinetic isotope effect, but the contribution to DeltaS(double dagger) from the temperature dependence of E-0' is positive......Intramolecular electron transfer in azurin in water and deuterium oxide has been studied over a broad temperature range. The kinetic deuterium isotope effect, k(H)/k(D), is smaller than unity (0.7 at 298 K), primarily caused by the different activation entropies in water (-56.5 J K-1 mol(-1...... entropy difference and to compensate for the different temperature dependencies of E-0'. Thus, differences in driving force and thermal expansion appear as the most straightforward rationale for the observed isotope effect....

  11. Cp*Rh(III)/Bicyclic Olefin Cocatalyzed C-H Bond Amidation by Intramolecular Amide Transfer.

    Science.gov (United States)

    Wang, Xiaoming; Gensch, Tobias; Lerchen, Andreas; Daniliuc, Constantin G; Glorius, Frank

    2017-05-10

    A bicyclic olefin was discovered as a cocatalyst in a Cp*Rh(III)-catalyzed C-H bond amidation proceeding by an intramolecular amide transfer in N-phenoxyacetamide derivatives. Combining experimental and theoretical studies, we propose that the olefin promotes a Rh(III) intermediate to undergo oxidative addition into the O-N bond to form a Rh(V) nitrenoid species and subsequently direct the nitrenoid to add to the ortho position. The amide directing group plays a dual role as a cleavable coordinating moiety as well as an essential coupling partner for the C-H amidation. This methodology was successfully applied to the late-stage diversification of natural products and a marketed drug under mild conditions.

  12. GTP binding to the ROC domain of DAP-kinase regulates its function through intramolecular signalling

    Science.gov (United States)

    Carlessi, Rodrigo; Levin-Salomon, Vered; Ciprut, Sara; Bialik, Shani; Berissi, Hanna; Albeck, Shira; Peleg, Yoav; Kimchi, Adi

    2011-01-01

    Death-associated protein kinase (DAPk) was recently suggested by sequence homology to be a member of the ROCO family of proteins. Here, we show that DAPk has a functional ROC (Ras of complex proteins) domain that mediates homo-oligomerization and GTP binding through a defined P-loop motif. Upon binding to GTP, the ROC domain negatively regulates the catalytic activity of DAPk and its cellular effects. Mechanistically, GTP binding enhances an inhibitory autophosphorylation at a distal site that suppresses kinase activity. This study presents a new mechanism of intramolecular signal transduction, by which GTP binding operates in cis to affect the catalytic activity of a distal domain in the protein. PMID:21738225

  13. Di- and sesquiterpenoids from Cystoseira genus: structure, intra-molecular transformations and biological activity.

    Science.gov (United States)

    Gouveia, Vera; Seca, Ana M L; Barreto, M Carmo; Pinto, Diana C G A

    2013-06-01

    Natural products have been the single most productive source of leads for the development of drugs, because of the great variety of their chemical structures. Previous chemical investigation of members of the genus Cystoseira resulted in the discovery of various bioactive secondary metabolites. The secondary metabolites isolated and characterized are very interesting, both from the biological activity and structural complexity points of view, which make this genus an attractive target for further investigations. The present review covers the research progress on natural products isolated from this genus since January 1995 until now, concerning the isolation and structural elucidation of the secondary metabolites from Cystoseira species. In this contribution significant biological properties are briefly discussed. Simultaneously, we gradually construct an intra-molecular pathway that logically interrelates the isolated compounds.

  14. Electron capture dissociation proceeds with a low degree of intramolecular migration of peptide amide hydrogens

    DEFF Research Database (Denmark)

    Rand, Kasper D; Adams, Christopher M; Zubarev, Roman A

    2008-01-01

    ECD using peptides with a unique selective deuterium incorporation. Our results show that only limited amide hydrogen migration occurs upon ECD, provided that vibrational excitation prior to the electron capture event is minimized. Peptide ions that are excessively vibrationally excited......Hydrogen (1H/2H) exchange combined with mass spectrometry (HX-MS) has become a recognized method for the analysis of protein structural dynamics. Presently, the incorporated deuterons are typically localized by enzymatic cleavage of the labeled proteins and single residue resolution is normally...... only obtained for a few residues. Determination of site-specific deuterium levels by gas-phase fragmentation in tandem mass spectrometers would greatly increase the applicability of the HX-MS method. The biggest obstacle in achieving this goal is the intramolecular hydrogen migration (i.e., hydrogen...

  15. Photophysical Model of 10-Hydroxybenzo[h]quinoline: Internal Conversion and Excited State Intramolecular Proton Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Junghwa; Joo, Taiha [Pohang Univ. of Science and Technology, Pohang (Korea, Republic of)

    2014-03-15

    Photophysics of 10-hydroxybenzo[h]quinoline (HBQ) has been in controversy, in particular, on the nature of the electronic states before and after the excited state intramolecular proton transfer (ESIPT), even though the dynamics and mechanism of the ESIPT have been well established. We report highly time resolved fluorescence spectra over the full emission frequency regions of the enol and keto isomers and the anisotropy in time domain to determine the accurate rates of the population decay, spectral relaxation and anisotropy decay of the keto isomer. We have shown that the ∼300 fs component observed frequently in ESIPT dynamics arises from the S{sub 2}→S{sub 1} internal conversion in the reaction product keto isomer and that the ESIPT occurs from the enol isomer in S{sub 1} state to the keto isomer in S{sub 2} state.

  16. Intramolecular synergistic effect of glutamic acid, cysteine and glycine against copper corrosion in hydrochloric acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Daquan, E-mail: zhdq@sh163.net [Department of Environmental Engineering, Shanghai University of Electric Power, Shanghai 200090 (China); Xie Bin; Gao Lixin; Cai Qirui [Department of Environmental Engineering, Shanghai University of Electric Power, Shanghai 200090 (China); Joo, Hyung Goun; Lee, Kang Yong [Stress Analysis and Failure Design Laboratory, School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2011-10-31

    The corrosion protection of copper by glutamic acid, cysteine, glycine and their derivative (glutathione) in 0.5 M hydrochloric acid solution has been studied by the electrochemical impedance spectroscopy and cyclic voltammetry. The inhibition efficiency of the organic inhibitors on copper corrosion increases in the order: glutathione > cysteine > cysteine + glutamic acid + glycine > glutamic acid > glycine. Maximum inhibition efficiency for cysteine reaches about 92.9% at 15 mM concentration level. The glutathione can give 96.4% inhibition efficiency at a concentration of 10 mM. The molecular structure parameters were obtained by PM3 (Parametric Method 3) semi-empirical calculation. The intramolecular synergistic effect of glutamic acid, cysteine and glycine moieties in glutathione is attributed to the lower energy of the lowest unoccupied molecular orbital (E{sub LUMO}) level and to the excess hetero-atom adsorption centers and the bigger coverage on the copper surface.

  17. Intramolecular migration of amide hydrogens in protonated peptides upon collisional activation

    DEFF Research Database (Denmark)

    Jørgensen, Thomas J D; Gårdsvoll, Henrik; Ploug, Michael

    2005-01-01

    if collision-induced dissociation (CID) should provide reliable site-specific information from (1)H/(2)H exchange experiments. We have explored a series of unique, regioselectively deuterium-labeled peptides as model systems to probe for intramolecular amide hydrogen migration under low-energy collisional...... are protected against exchange with the solvent, while the amide hydrogens of the nonbinding sequences exchange rapidly with the solvent. We have utilized such long-lived complexes to generate peptides labeled with deuterium in either the binding or nonbinding region, and the expected regioselectivity...... of this labeling was confirmed after pepsin proteolysis. CID of such deuterated peptides, [M + 2H](2+), yielded fragment ions (b- and y-ions) having a deuterium content that resemble the theoretical values calculated for 100% scrambling. Thus, complete randomization of all hydrogen atoms attached to nitrogen...

  18. Unusual NHC-Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes

    KAUST Repository

    Sipos, Gellért

    2016-04-10

    N-heterocyclic carbene (NHC) ligands with naphthyl side chains were employed for the synthesis of unsaturated, yet isolable [(NHC)Ir(cod)]+ (cod=1,5-cyclooctadiene) complexes. These compounds are stabilised by an interaction of the aromatic wingtip that leads to a sideways tilt of the NHC-Ir bond. Detailed studies show how the tilting of such N-heterocyclic carbenes affects the electronic shielding properties of the carbene carbon atom and how this is reflected by significant upfield shifts in the 13CNMR signals. When employed in the intramolecular hydroamination, these [(NHC)Ir(cod)]+ species show very high catalytic activity under mild reaction conditions. An enantiopure version of the catalyst system produces pyrrolidines with excellent enantioselectivities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

    KAUST Repository

    Pace, Natalie A.

    2017-11-30

    The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. In this paper, we investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically, and is strongly dependent on side-chain identity. These results show that it may be necessary to carefully engineer the solid-state microstructure of these “singlet fission polymers” in order to produce the long-lived triplets needed to realize efficient photovoltaic devices.

  20. Intramolecular stabilization of a catalytic [FeFe]-hydrogenase mimic investigated by experiment and theory.

    Science.gov (United States)

    Pandey, Indresh Kumar; Natarajan, Mookan; Faujdar, Hemlata; Hussain, Firasat; Stein, Matthias; Kaur-Ghumaan, Sandeep

    2018-04-03

    The mono-substituted complex [Fe2(CO)5(μ-naphthalene-2-thiolate)2(P(PhOMe-p)3)] was prepared taking after the structural principles from both [NiFe] and [FeFe]-hydrogenase enzymes. Crystal structures are reported for this complex and the all carbonyl analogue. The bridging naphthalene thiolates resemble μ-bridging cysteine amino acids. One of the naphthyl moieties forms π-π stacking interactions with the terminal bulky phosphine ligand in the crystal structure and in calculations. This interaction stabilizes the reduced and protonated forms during electrocatalytic proton reduction in the presence of acetic acid and hinders the rotation of the phosphine ligand. The intramolecular π-π stabilization, the electrochemistry and the mechanism of the hydrogen evolution reaction were investigated using computational approaches.

  1. Inter- and intramolecular aldol reactions promiscuously catalyzed by a proline-based tautomerase.

    Science.gov (United States)

    Rahimi, Mehran; Geertsema, Edzard M; Miao, Yufeng; van der Meer, Jan-Ytzen; van den Bosch, Thea; de Haan, Pim; Zandvoort, Ellen; Poelarends, Gerrit J

    2017-03-28

    The enzyme 4-oxalocrotonate tautomerase (4-OT), which in nature catalyzes a tautomerization step as part of a catabolic pathway for aromatic hydrocarbons, was found to promiscuously catalyze different types of aldol reactions. These include the self-condensation of propanal, the cross-coupling of propanal and benzaldehyde, the cross-coupling of propanal and pyruvate, and the intramolecular cyclizations of hexanedial and heptanedial. Mutation of the catalytic amino-terminal proline (P1A) greatly reduces 4-OT's aldolase activities, whereas mutation of another active site residue (F50A) strongly enhances 4-OT's aldolase activities, indicating that aldolization is an active site process. This catalytic promiscuity of 4-OT could be exploited as starting point to create tailor-made, artificial aldolases for challenging self- and cross-aldolizations.

  2. Voltage Losses in Organic Solar Cells: Understanding the Contributions of Intramolecular Vibrations to Nonradiative Recombinations

    KAUST Repository

    Chen, Xiankai

    2017-12-18

    The large voltage losses usually encountered in organic solar cells significantly limit the power conversion efficiencies (PCEs) of these devices, with the result that the current highest PCE values in single-junction organic photovoltaic remain smaller than for other solar cell technologies, such as crystalline silicon or perovskite solar cells. In particular, the nonradiative recombinations to the electronic ground state from the lowest-energy charge-transfer (CT) states at the donor-acceptor interfaces in the active layer of organic devices, are responsible for a significant part of the voltage losses. Here, to better comprehend the nonradiative voltage loss mechanisms, a fully quantum-mechanical rate formula is employed within the framework of time-dependent perturbation theory, combined with density functional theory. The objective is to uncover the specific contributions of intramolecular vibrations to the CT-state nonradiative recombinations in several model systems, which include small-molecule and polymer donors as well as fullerene and nonfullerene acceptors.

  3. Intramolecular synergistic effect of glutamic acid, cysteine and glycine against copper corrosion in hydrochloric acid solution

    International Nuclear Information System (INIS)

    Zhang Daquan; Xie Bin; Gao Lixin; Cai Qirui; Joo, Hyung Goun; Lee, Kang Yong

    2011-01-01

    The corrosion protection of copper by glutamic acid, cysteine, glycine and their derivative (glutathione) in 0.5 M hydrochloric acid solution has been studied by the electrochemical impedance spectroscopy and cyclic voltammetry. The inhibition efficiency of the organic inhibitors on copper corrosion increases in the order: glutathione > cysteine > cysteine + glutamic acid + glycine > glutamic acid > glycine. Maximum inhibition efficiency for cysteine reaches about 92.9% at 15 mM concentration level. The glutathione can give 96.4% inhibition efficiency at a concentration of 10 mM. The molecular structure parameters were obtained by PM3 (Parametric Method 3) semi-empirical calculation. The intramolecular synergistic effect of glutamic acid, cysteine and glycine moieties in glutathione is attributed to the lower energy of the lowest unoccupied molecular orbital (E LUMO ) level and to the excess hetero-atom adsorption centers and the bigger coverage on the copper surface.

  4. Comparative analysis of intramolecular parameters of nitrocompounds: crystalline and gas phases

    Science.gov (United States)

    Arnautova, Elena A.; Pivina, Tatyana S.; Gladkikh, Olga P.; Vilkov, Lev V.

    1996-01-01

    The results of a study of intramolecular parameters for chemical classes of nitrocompounds in different states of aggregation are collected and analyzed: electron-diffraction experiments and microwave spectroscopy for the gas phase, and X-ray diffraction (from the Cambridge Bank of X-ray and neutron-diffraction data) for molecules in crystals. Systematic analysis of molecular structural parameters for valence bonds and angles of the nitrogroups in these compounds shows these properties to be conserved. This allows us to use the calculated geometrical molecular parameters of nitrocompounds (obtained theoretically by quantum-chemical schemes) when building models of base (rigid) molecules for constructing elementary cells within different structural classes, with the aim of a subsequent computer search for dense packing in the corresponding molecular crystals.

  5. Mechanisms of intramolecular communication in a hyperthermophilic acylaminoacyl peptidase: a molecular dynamics investigation.

    Science.gov (United States)

    Papaleo, Elena; Renzetti, Giulia; Tiberti, Matteo

    2012-01-01

    Protein dynamics and the underlying networks of intramolecular interactions and communicating residues within the three-dimensional (3D) structure are known to influence protein function and stability, as well as to modulate conformational changes and allostery. Acylaminoacyl peptidase (AAP) subfamily of enzymes belongs to a unique class of serine proteases, the prolyl oligopeptidase (POP) family, which has not been thoroughly investigated yet. POPs have a characteristic multidomain three-dimensional architecture with the active site at the interface of the C-terminal catalytic domain and a β-propeller domain, whose N-terminal region acts as a bridge to the hydrolase domain. In the present contribution, protein dynamics signatures of a hyperthermophilic acylaminoacyl peptidase (AAP) of the prolyl oligopeptidase (POP) family, as well as of a deletion variant and alanine mutants (I12A, V13A, V16A, L19A, I20A) are reported. In particular, we aimed at identifying crucial residues for long range communications to the catalytic site or promoting the conformational changes to switch from closed to open ApAAP conformations. Our investigation shows that the N-terminal α1-helix mediates structural intramolecular communication to the catalytic site, concurring to the maintenance of a proper functional architecture of the catalytic triad. Main determinants of the effects induced by α1-helix are a subset of hydrophobic residues (V16, L19 and I20). Moreover, a subset of residues characterized by relevant interaction networks or coupled motions have been identified, which are likely to modulate the conformational properties at the interdomain interface.

  6. Tether-directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

    Directory of Open Access Journals (Sweden)

    Cox Liam R

    2007-02-01

    Full Text Available Abstract Background Using a silyl tether to unite an aldehyde electrophile and allylsilane nucleophile into a single molecule allows a subsequent Lewis-acid-mediated allylation to proceed in an intramolecular sense and therefore receive all the benefits associated with such processes. However, with the ability to cleave the tether post allylation, a product that is the result of a net intermolecular reaction can be obtained. In the present study, four diastereoisomeric β-silyloxy-α-methyl aldehydes, which contain an allylsilane tethered through the β-carbinol centre, have been prepared, in order to probe how the relative configuration of the two stereogenic centres affects the efficiency and selectivity of the intramolecular allylation. Results Syn-aldehydes, syn-4a and syn-4b, both react poorly, affording all four possible diastereoisomeric oxasilacycle products. In contrast, the anti aldehydes anti-4a and anti-4b react analogously to substrates that lack substitution at the α-site, affording only two of the four possible allylation products. Conclusion The outcome of the reaction with anti-aldehydes is in accord with reaction proceeding through a chair-like transition state (T.S.. In these systems, the sense of 1,3-stereoinduction can be rationalised by the aldehyde electrophile adopting a pseudoaxial orientation, which will minimise dipole-dipole interactions in the T.S. The 1,4-stereoinduction in these substrates is modest and seems to be modulated by the R substituent in the starting material. In the case of the syn-substrates, cyclisation through a chair T.S. is unlikely as this would require the methyl substituent α to the reacting carbonyl group to adopt an unfavourable pseudoaxial position. It is therefore proposed that these substrates react through poorly-defined T.S.s and consequently exhibit essentially no stereoselectivity.

  7. Reaction Coordinate, Free Energy, and Rate of Intramolecular Proton Transfer in Human Carbonic Anhydrase II.

    Science.gov (United States)

    Paul, Sanjib; Paul, Tanmoy Kumar; Taraphder, Srabani

    2018-03-22

    The role of structure and dynamics of an enzyme has been investigated at three different stages of its function including the chemical event it catalyzes. A one-pot computational method has been designed for each of these stages on the basis of classical and/or quantum mechanical-molecular mechanical molecular dynamics and transition path sampling simulations. For a pair of initial and final states A and B separated by a high free-energy barrier, using a two-stage selection process, several collective variables (CVs) are identified that can delineate A and B. However, these CVs are found to exhibit strong cross-coupling over the transition paths. A set of mutually orthogonal order parameters is then derived from these CVs and an optimal reaction coordinate, r, determined applying half-trajectory likelihood maximization along with a Bayesian information criterion. The transition paths are also used to project the multidimensional free energy surface and barrier crossing dynamics along r. The proposed scheme has been applied to the rate-determining intramolecular proton transfer reaction of the well-known enzyme human carbonic anhydrase II. The potential of mean force, F( r), in the absence of the chemical step is found to reproduce earlier results on the equilibrium population of two side-chain orientations of key residue His-64. Estimation of rate constants, k, from mean first passage times for the three different stages of catalysis shows that the rate-determining step of intramolecular proton transfer occurs with k ≃ 1.0 × 10 6 s -1 , in close agreement with known experimental results.

  8. Structural and biochemical characterizations of an intramolecular tandem coiled coil protein.

    Science.gov (United States)

    Shin, Donghyuk; Kim, Gwanho; Kim, Gyuhee; Zheng, Xu; Kim, Yang-Gyun; Lee, Sangho

    2014-12-12

    Coiled coil has served as an excellent model system for studying protein folding and developing protein-based biomaterials. Most designed coiled coils function as oligomers, namely intermolecular coiled coils. However, less is known about structural and biochemical behavior of intramolecular coiled coils where coiled coil domains are covalently linked in one polypeptide. Here we prepare a protein which harbors three coiled coil domains with two short linkers, termed intramolecular tandem coiled coil (ITCC) and characterize its structural and biochemical behavior in solution. ITCC consists of three coiled coil domains whose sequences are derived from Coil-Ser and its domain swapped dimer. Modifications include positioning E (Glu) residue at "e" and K (Lys) at "g" positions throughout heptad repeats to enhance ionic interaction among its constituent coiled coil domains. Molecular modeling of ITCC suggests a compact triple helical bundle structure with the second and the third coiled coil domains forming a canonical coiled coil. ITCC exists as a mixture of monomeric and dimeric species in solution. Small-angle X-ray scattering reveals ellipsoidal molecular envelopes for both dimeric and monomeric ITCC in solution. The theoretically modeled structures of ITCC dock well into the envelopes of both species. Higher ionic strength shifts the equilibrium into monomer with apparently more compact structure while secondary structure remains unchanged. Taken together, our results suggest that our designed ITCC is predominantly monomeric structure through the enhanced ionic interactions, and its conformation is affected by the concentration of ionic species in the buffer. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Intra-molecular Charge Transfer and Electron Delocalization in Non-Fullerene Organic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qinghe; Zhao, Donglin; Goldey, Matthew B.; Filatov, Alexander S.; Sharapov, Valerii; Colon, Yamil; Cai, Zhengxu; Jiang, Xuanfeng; Wang, Junpeng; Chen, Wei; de Pablo, Juan; Galli, Giulia; Yu, Luping

    2018-03-28

    Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the a position. With fully aromatic cores, TPB and TPSe have pi-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space. Further, the LUMO of TPB shows a greater contribution from the orbitals belonging to the connective core of the molecules than that of TPC. Overall, the properties of the HOMO and LUMO point at increased intra-molecular delocalization of negative charge carriers for TPB and TPSe than for TPC and TPSi and hence at a more facile intra-molecular charge transfer for the former. The film absorption and emission spectra showed evidences for the inter -molecular electron delocalization in TPB and TPSe, which is consistent with the network structure revealed by X-ray diffraction studies on single crystals of TPB. These features benefit the formation of charge transfer states and/or facilitate charge transport. Thus, higher electron mobility and higher charge dissociation probabilities under J(sc) condition were observed in blend films of TPB:PTB7-Th and TPSe:PTB7-Th than those in TPC:PTB7Th and TPSi:PTB7-Th blend films. As a result, the J(sc) and fill factor values of 15.02 mA/cm(2), 0.58 and 14.36 mA/cm(2), 0.55 for TPB- and TPSe-based solar cell are observed, whereas those for TPC and TPSi are 11.55 mA/cm2, 0.47 and 10.35 mA/cm(2), 0.42, respectively.

  10. An intramolecular bond at cluster of differentiation 81 ectodomain is important for hepatitis C virus entry.

    Science.gov (United States)

    Yang, Wei; Zhang, Meng; Chi, Xiaojing; Liu, Xiuying; Qin, Bo; Cui, Sheng

    2015-10-01

    Hepatitis C virus (HCV) infection is one of the leading causes of chronic liver diseases; however, HCV vaccine remains unavailable to date. One main obstacle is the lack of an efficient small animal model. Cluster of differentiation 81 (CD81) is an essential entry coreceptor for HCV species specificity to humans, though the underlying mechanisms are yet to be fully elucidated. We performed structural, biophysical, and virologic studies on HCV nonpermissive CD81s from mice and African green monkeys [mouse cluster of differentiation 81 (mCD81) and African green monkey cluster of differentiation 81 (agmCD81)] and compared with human cluster of differentiation 81 (hCD81). We discovered an intramolecular hydrogen bond (Gln188-Nε2-H: Glu196-Oε2, 2 Å, 124°) within the large extracellular loop (LEL) of mCD81 and a salt bridge (Lys188-Nζ: Asp196-Oδ2, 2.4 Å) within agmCD81-LEL between residues 188 and 196. This structural feature is missing in hCD81. We demonstrated that the introduction of a single 188-196 bond to hCD81 impaired its binding affinity to HCV envelope glycoprotein 2 (HCV E2) and significantly decreased HCV pseudoviral particle (HCVpp) entry efficiency (4.92- to 8.42-fold) and cell culture-grown HCV (HCVcc) infectivity (4.55-fold), despite the availability of Phe186. For HCV nonpermissive CD81s, the introduction of Phe186 by Leu186F substitution alone was insufficient to confer HCV permissiveness. The disruption of the original 188-196 bond and Leu186F substitution were both required for potent binding to HCV E2 HCVpp entry efficiency and HCVcc infectivity. Our structural and biophysical analyses suggest that the intramolecular 188-196 bond restricts the intrinsic conformational dynamics of D-helix of CD81-LEL, which is essential for HCV entry, thus impairs HCV permissiveness. Our findings reveal a novel molecular determinant for HCV entry in addition to the well-characterized Phe186 and provide further guideline for selecting an HCV small animal model

  11. Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer

    Science.gov (United States)

    Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

    2017-12-01

    Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

  12. Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

    International Nuclear Information System (INIS)

    Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

    2013-01-01

    Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

  13. EVAPORATION: a new vapor pressure estimation method for organic molecules including non-additivity and intramolecular interactions

    Science.gov (United States)

    Compernolle, S.; Ceulemans, K.; Müller, J.-F.

    2011-04-01

    We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects), a method to predict vapour pressure p0 of organic molecules needing only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log10p0(T) is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: carbonyls, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA).

  14. Use of Alkyl Ethers as Traceless Hydride Donors in Brønsted Acid-Catalyzed Intramolecular Hydrogen Atom Transfer.

    Science.gov (United States)

    Gandamana, Dhika Aditya; Wang, Bin; Tejo, Ciputra; Bolte, Benoit; Gagosz, Fabien; Chiba, Shunsuke

    2018-03-25

    A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Brønsted acid catalysis has been developed. The method is based on the use of a benzyl or an isopropyl ether as a traceless hydrogen atom donor and involves an intramolecular hydride transfer as a key step that can be achieved in regio- and stereoselective manners. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. An efficient and green synthesis of 1-indanone and 1-tetralone via intramolecular Friedel-Crafts acylation reaction

    DEFF Research Database (Denmark)

    Tran, Phuong Hoang; Huynh, Vy Hieu; Hansen, Poul Erik

    2015-01-01

    Metal-triflate-catalyzed intramolecular Friedel–Crafts acylation of 3-arylpropanoic and 4-arylbutanoic acids in triflate-anion ionic liquids under monomodal microwave irradiation is reported. The environmentally benign synthetic procedure allows the formation of cyclic ketones in good yields with...... a short reaction time. The catalytic metal triflate in triflate-anion ionic liquids can be easily recovered and reused several times without significant loss of the catalytic performance....

  16. Synthesis of Amidines from Amides Using a Nickel-Catalyzed Decarbonylative Amination through CO Extrusion Intramolecular Recombination Fragment Coupling.

    Science.gov (United States)

    Liu, Xiangqian; Yue, Huifeng; Jia, Jiaqi; Guo, Lin; Rueping, Magnus

    2017-09-04

    A catalytic synthesis of amidines from amides has been established for the first time. The newly developed CO extrusion recombination process takes advantage of an inexpensive nickel(II) catalyst and provides the corresponding amidines with high efficiency. The intramolecular fragment coupling shows excellent chemoselectivity, starts from readily available amides, and provides a valuable alternative amidine synthesis protocol. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Synthesis of 2,3-dihydro-1H-pyrroles by intramolecular cyclization of N-(3-butynyl)-sulfonamides.

    Science.gov (United States)

    Chung, Min-Ching; Chan, Yung-Hsiang; Chang, Wen-Jung; Hou, Duen-Ren

    2017-05-03

    Hydroamination of 3-butynamine derivatives to give non-aromatic 2,3-dihydropyrroles was achieved by using PdCl 2 or AuCl as the catalyst. With microwave-assisted heating, up to 92% isolated yield was obtained from this intramolecular 5-endo-dig cyclisation. The cyclopentane- and cyclohexane-fused 2,3-dihydropyrroles were transformed into the corresponding N-tosyl-pyrrolidine-2-carboxylic acids.

  18. An enantioselective organocatalytic intramolecular Morita-Baylis-Hillman (IMBH) reaction of dienones, and elaboration of the IMBH adducts to fluorenones.

    Science.gov (United States)

    Satpathi, Bishnupada; Wagulde, Siddhant V; Ramasastry, S S V

    2017-07-13

    An enantioselective organocatalytic intramolecular Morita-Baylis-Hillman (IMBH) reaction of dienones is reported for the first time. This has been achieved by incorporating entropy and synergy considerations during the substrate design. The reaction conditions are thoroughly verified for an efficient synthesis of highly functionalised cyclopenta-fused arenes and heteroarenes in excellent yields and enantioselectivities. The synthetic utility of the IMBH-adducts has been demonstrated by transforming them into 3,4-disubstituted fluorenones in a serendipitous manner.

  19. On the Possibility of Uphill Intramolecular Electron Transfer in Multicopper Oxidases: Electrochemical and Quantum Chemical Study of Bilirubin Oxidase

    Czech Academy of Sciences Publication Activity Database

    Shleev, S.; Andoralov, V.; Falk, M.; Reimann, C. T.; Ruzgas, T.; Srnec, Martin; Ryde, U.; Rulíšek, Lubomír

    2012-01-01

    Roč. 24, č. 7 (2012), s. 1524-1540 ISSN 1040-0397 Grant - others:7th Framework Program(XE) NMP4-SL-2009-229255 Institutional research plan: CEZ:AV0Z40550506 Keywords : bilirubin oxidase * intramolecular electron transfer * rate-limiting catalytic step * reorganization energy * QM/MM calculations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.817, year: 2012

  20. A Critical Check for the Role of Resonance in Intramolecular Hydrogen Bonding.

    Science.gov (United States)

    Jiang, Xiaoyu; Zhang, Huaiyu; Wu, Wei; Mo, Yirong

    2017-11-27

    Although resonance-assisted H-bonds (RAHBs) are well recognized, the role of π resonance in RAHBs is controversial, as the seemingly enhanced H-bonds in unsaturated compounds may result from the constraints imposed by the σ skeleton. Herein the block-localized wave function (BLW) method, which can derive optimal yet resonance-quenched structures with related physiochemical properties, was employed to examine the correlation between π resonance and the strength of intramolecular RAHBs. Examination of a series of paradigmatic molecules with RAHBs and their saturated analogues showed that it is inappropriate to compare a conjugated system with its saturated counterpart, as they may have quite different σ frameworks. Nevertheless, comparison between a conjugated system and its resonance-quenched (i.e., electron-localized) state, which have identical σ skeletons, shows that in all studied cases, π resonance unanimously reduces the bonding distance by 0.111-0.477 Å, strengthens the bonding by 40-56 %, and redshifts the D-H vibrational frequency by 104-628 cm -1 . Furthermore, there is an excellent correlation between hydrogen-bonding strength and the classical Coulomb attraction between the hydrogen-bond donor and the acceptor, which suggests that the dominant role of the electrostatic interaction in H-bonds and RAHBs originates from the charge flow from H-bond donors to acceptors through π conjugation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Mechanochemical Preparation of Cobalt Nanoparticles through a Novel Intramolecular Reaction in Cobalt(II Complexes

    Directory of Open Access Journals (Sweden)

    Seyed Abolghasem Kahani

    2015-01-01

    Full Text Available A novel solid state reaction involving a series of cobalt(II hydrazine-azides has been used to prepare metallic cobalt nanoparticles. The reactions of [Co(N2H4(N32], [Co(N2H42(N32], and [Co(N2H4(N3Cl]·H2O via NaOH, KOH as reactants were carried out in the solid state. These complexes undergo an intramolecular two-electron oxidation-reduction reaction at room temperature, producing metallic cobalt nanoparticles (Co1–Co6. The aforementioned complexes contain cobalt(II that is an oxidizing agent and also hydrazine ligand as a reducing agent. Other products produced include sodium azide and ammonia gas. The cobalt metal nanoparticles were characterized using X-ray powder diffraction (XRD, scanning electron microscopy (SEM, and vibrating sample magnetometer (VSM. The synthesized cobalt nanoparticles have similar morphologies; however, their particle size distributions are different.

  2. NMR investigation of intramolecular dynamics of heteroleptic triple-decker (porphyrinato)(phthalocyaninato) lanthanides.

    Science.gov (United States)

    Birin, Kirill P; Gorbunova, Yulia G; Tsivadze, Aslan Yu

    2011-11-21

    Intramolecular dynamics of meso-aryl substituents of porphyrin deck in the triple-decker lanthanide (porphyrinato)(phthalocyaninates) of symmetrical type [Br(4)TPP]Ln[(15C5)(4)Pc]Ln[Br(4)TPP] (Ln = La, Nd, Eu; [Br(4)TPP] = tetrakis-5,10,15,20-(4-bromophenyl)-porphyrinato-ligand; [(15C5)(4)Pc] = tetrakis-(15-crown-5)-phthalocyaninato-ligand) are investigated. Attempts to achieve coalescence were not successful, although the trend of exchanging protons to coalescence point was observed in the case of Nd and Eu complexes. The analysis of NOESY cross-peaks between exchanging protons allowed to evaluate the rotation rate constants at different temperatures. The activation barrier of the meso-aryl substituent rotation was calculated with Arrhenius equation based on determined rate constants. The rate constants are lower and activation barriers are higher than ones found previously for related compounds. This journal is © The Royal Society of Chemistry 2011

  3. Spectroscopic and theoretical investigations on intramolecular charge transfer phenomenon in 1-3-dioxolane derivative

    Science.gov (United States)

    Zhang, Zhiyong; Zhang, Zhongzhi; Luo, Yijing; Sun, Shanshan; Zhang, Guangqing

    2018-02-01

    High fluorescence quantum yield (FQY) and large Stokes shift (SS) cannot be easily achieved simultaneously by traditional PICT or TICT fluorescent probe. However, an 1-3-dioxolane derivative named 5-methyl-8,9-dihydro-5H-[1,3]dioxolo[4,5-b]carbazol-6(7H)-one (MDDCO) features both high FQY and large SS. The purpose of this study is to search the mechanism behind this phenomenon by theoretical method. Simulated structure changes and charge transfer suggest ICT process in MDDCO is similar to PLICT (Planarized Intramolecular Charge Transfer) process. Calculated UV-Vis spectra and fluorescence spectra show that PLICT-like state (S1 state) of MDDCO leads to large SS. Computed transient-absorption spectra and radiative decay rates indicate that PLICT-like state is key factor for high FQY of MDDCO. These findings suggest that PLICT-like state in 1,3-dioxolane derivatives can achieve both large SS and high FQY, which presents a new method for high-performance fluorescent probe design.

  4. Dynamics of intramolecular spin exchange interaction of a nitronyl nitroxide diradical in solution and on surfaces

    Science.gov (United States)

    Lloveras, V.; Badetti, E.; Veciana, J.; Vidal-Gancedo, J.

    2016-02-01

    In this paper we report the study of the dynamics of a thermally modulated intramolecular spin exchange interaction of a novel diradical nitronyl nitroxide-substituted disulfide in solution and when it is grafted on a gold surface. The structure of this diradical was designed to have flexible chains leading to intramolecular collisions and hence spin exchange interaction, and with an appropriate binding group to be grafted on the gold surface to study its behavior on the surface. In solution, this diradical shows a strong spin exchange interaction between both radicals which is modulated by temperature, but also gold nanoparticles (AuNPs) functionalized with this diradical permit investigation of such a phenomenon in surface-grafted radicals. The spin-labelled AuNP synthesis was optimized to obtain high coverage of spin labels to lead to high spin exchange interaction. The obtained AuNPs were studied by Electron Paramagnetic Resonance (EPR), UV-Vis, and IR spectroscopies, HR-TEM microscopy, Cyclic Voltammetry (CV), Energy Dispersive X-ray analysis (EDX) and Thermogravimetric Analysis (TGA). This inorganic-organic hybrid material also showed dipolar interactions between its radicals which were confirmed by the appearance in the EPR spectra of an |Δms| = 2 transition at half-field. This signal gives direct evidence of the presence of a high-spin state and permitted us to study the nature of the magnetic coupling between the spins which was found to be antiferromagnetic. Self-Assembled Monolayers (SAMs) of these radicals on the Au (111) substrate were also prepared and studied by contact angle, X-Ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Cyclic Voltammetry and EPR. The magnetic as well as the electrochemical properties of the hybrid surfaces were studied and compared with the properties of this diradical in solution. Analogies between the properties of AuNPs with high coverage of radicals and those of SAM were

  5. Contribution of inter- and intramolecular energy transfers to heat conduction in liquids.

    Science.gov (United States)

    Torii, Daichi; Nakano, Takeo; Ohara, Taku

    2008-01-28

    The molecular dynamics expression of heat flux, originally derived by Irving and Kirkwood [J. Chem. Phys. 18, 817 (1950)] for pairwise potentials, is generalized in this paper for systems with many-body potentials. The original formula consists of a kinetic part and a potential part, and the latter term is found in the present study to be expressible as a summation of contributions from all the many-body potentials defined in the system. The energy transfer among a set of sites for which a many-body potential is defined is discussed and evaluated by the rate of increase in the kinetic energy of each site due to the potential, and its accumulation over all the potentials in the system is shown to make up the potential part of the generalized expression. A molecular dynamics simulation for liquid n-octane was performed to demonstrate the applicability of the new expression obtained in this study to measure the heat flux and to elucidate the contributions of inter- and intramolecular potentials to heat conduction.

  6. Discovery of intramolecular trans-sialidases in human gut microbiota suggests novel mechanisms of mucosal adaptation

    Science.gov (United States)

    Tailford, Louise E.; Owen, C. David; Walshaw, John; Crost, Emmanuelle H.; Hardy-Goddard, Jemma; Le Gall, Gwenaelle; de Vos, Willem M.; Taylor, Garry L.; Juge, Nathalie

    2015-07-01

    The gastrointestinal mucus layer is colonized by a dense community of microbes catabolizing dietary and host carbohydrates during their expansion in the gut. Alterations in mucosal carbohydrate availability impact on the composition of microbial species. Ruminococcus gnavus is a commensal anaerobe present in the gastrointestinal tract of >90% of humans and overrepresented in inflammatory bowel diseases (IBD). Using a combination of genomics, enzymology and crystallography, we show that the mucin-degrader R. gnavus ATCC 29149 strain produces an intramolecular trans-sialidase (IT-sialidase) that cleaves off terminal α2-3-linked sialic acid from glycoproteins, releasing 2,7-anhydro-Neu5Ac instead of sialic acid. Evidence of IT-sialidases in human metagenomes indicates that this enzyme occurs in healthy subjects but is more prevalent in IBD metagenomes. Our results uncover a previously unrecognized enzymatic activity in the gut microbiota, which may contribute to the adaptation of intestinal bacteria to the mucosal environment in health and disease.

  7. Polarization of emission from asymmetric rotors. II. Vector reorientation through intramolecular coupling and inelastic collisions

    Science.gov (United States)

    Truhins, Kaspars; McCaffery, Anthony J.; Alwahabi, Zeyad T.; Rawi, Zaid

    1997-07-01

    We report measurements of the linear and circular polarization ratios from fully resolved rotational levels of the asymmetric rotor NH2 populated by collisions with H atoms. The results compare well with a theoretical model that includes the depolarizing effects of intramolecular coupling of rotational angular momentum N to nuclear and to electron spin. These have a very significant influence on fluorescence polarization. The model also incorporates the tilting of the N vector in the molecule frame that occurs when inter-k stack transitions take place. Changes in N vector orientation are described with the aid of the angular momentum sphere, a classical representation of the motion of the N vector in a molecule fixed frame. The theoretical treatment assumes the classically impulsive limit for the collisional interaction with conservation of the m quantum number along the kinematic apse. This description of the fate of the N vector under the influence of intra- and intermolecular interactions allows stereodynamical conclusions to be drawn from experimental observations of fluorescence polarization.

  8. C—C bond formation in the intramolecular Diels-Alder reaction of triene amides

    Directory of Open Access Journals (Sweden)

    Abdelilah Benallou

    2018-02-01

    Full Text Available The mechanism nature of the intramolecular Diels–Alder reaction has been performed; and thus, the changes of C—C bond forming/breaking along IRC are characterized in this study. Conceptual DFT analyses of the most favorable adduct fused/exo shows that the flux electronic will take place from diene to dienophile moiety. Moreover, ELF topological analysis based on the electron density predicts that C—C bond is formed by the coupling of two pseudoradical centers generated at the most significant atoms of the molecules. However, C2 vs C3, also C1 and C4 interaction comes mainly from the global electron density transfer which takes place along the reaction. Two- stage one-step is the proposed mechanism of this reaction, the first stage aims for the formation of C2—C3 σ bond while the second stage aims for C1—C4 σ bond formation. Interestingly, the observed asynchronicity of this IMDA reaction due principally to the asymmetric reorganization of electron density at the most attractive centers.

  9. Absence of Intramolecular Singlet Fission in Pentacene-Perylenediimide Heterodimers: The Role of Charge Transfer State.

    Science.gov (United States)

    Wang, Long; Wu, Yishi; Chen, Jianwei; Wang, Lanfen; Liu, Yanping; Yu, Zhenyi; Yao, Jiannian; Fu, Hongbing

    2017-11-16

    A new class of donor-acceptor heterodimers based on two singlet fission (SF)-active chromophores, i.e., pentacene (Pc) and perylenediimide (PDI), was developed to investigate the role of charge transfer (CT) state on the excitonic dynamics. The CT state is efficiently generated upon photoexcitation. However, the resulting CT state decays to different energy states depending on the energy levels of the CT state. It undergoes extremely rapid deactivation to the ground state in polar CH 2 Cl 2 , whereas it undergoes transformation to a Pc triplet in nonpolar toluene. The efficient triplet generation in toluene is not due to SF but CT-mediated intersystem crossing. In light of the energy landscape, it is suggested that the deep energy level of the CT state relative to that of the triplet pair state makes the CT state actually serve as a trap state that cannot undergoes an intramolecular singlet fission process. These results provide guidance for the design of SF materials and highlight the requisite for more widely applicable design principles.

  10. Ruthenium-modified cytochrome c: temperature dependence of the rate of intramolecular electron transfer

    International Nuclear Information System (INIS)

    Isied, S.S.; Kuehn, C.; Worosila, G.

    1984-01-01

    The ruthenium-modified horse heart cytochrome c, Ru(III)-cyt c(III), where the ruthenium is bound to the histidines-33 residue has been synthesized and characterized by ruthenium analysis, UV-vis and CD spectra, and differential pulse polarography and cyclic voltammetry. The intermediate Ru(III)-cyt c(III) has been generated by pulse-radioanalysis with use of four different radicals, CO 2 -., (CH 3 )COH., (CH 2 OH) 3 CCHOH, and -OCCH(OH)C(OH)CO 2 -. The rate of intramolecular electron transfer within the Ru(III)-cyt c(III) complex and its temperature dependence were determined over a 40 0 C temperature range with the CO 2 -. radical. At 25 0 C, these values are k/sub u/=53 +/- s/sup -1/ (pH 7.01 M phosphate buffer, 0.1 M NaHCO 2 ), ΔH/sup +/=3.5 +/- 0.2 kcal mol/sup -1/, and ΔS/sup +/=-39 +/- 1 eu

  11. Structural factors influencing the intramolecular charge transfer and photoinduced electron transfer in tetrapyrazinoporphyrazines.

    Science.gov (United States)

    Novakova, Veronika; Hladík, Petr; Filandrová, Tereza; Zajícová, Ivana; Krepsová, Veronika; Miletin, Miroslav; Lenčo, Juraj; Zimcik, Petr

    2014-03-21

    A series of unsymmetrical tetrapyrazinoporphyrazines (TPyzPzs) from the group of azaphthalocyanines with one peripherally attached amino substituent (donor) were synthesized, and their photophysical properties (fluorescence quantum yield and singlet oxygen quantum yield) were determined. The synthesized TPyzPzs were expected to undergo intramolecular charge transfer (ICT) as the main pathway for deactivating their excited states. Several structural factors were found to play a critical role in ICT efficiency. The substituent in the ortho position to the donor center significantly influences the ICT, with tert-butylsulfanyl and butoxy substituents inducing the strongest ICTs, whereas chloro, methyl, phenyl, and hydrogen substituents in this position reduce the efficiency. The strength of the donor positively influences the ICT efficiency and correlates well with the oxidation potential of the amines used as the substituents on the TPyzPz as follows: n-butylamine ICT (with conjugated donors and acceptors) in the TPyzPz also proved to be much stronger than a photoinduced electron transfer in which the donor and the acceptor are connected through an aliphatic linker.

  12. Intramolecular Cooperativity in the Reaction of Diacyl Phosphates with Serine ß-Lactamases

    Science.gov (United States)

    Majumdar, Sudipta; Pratt, R.F.

    2010-01-01

    Asymmetric diaroyl phosphates (ArCOOPO2−OCOAr′, where Ar = Ph, Ar′ = 4-biphenyl, 2-benzothiophenyl and 2-benzofuranyl), have been prepared, evaluated as serine (classes A, C, D) β-lactamase inhibitors, and compared with respect to the latter with their symmetric “parents”, where Ar = Ar′. The asymmetric compounds, in general, were found to react with the β-lactamases in two modes, corresponding to different orientations with respect to the active site, whereby either of the two aroyl groups may acylate the enzyme to form two different inert acyl-enzymes, E-COAr and E-COAr′. In all cases, the asymmetric compounds, in one orientation, react more rapidly with the enzymes tested than one symmetrical “parent” but not both. From comparisons of activation free energy differences, it was found that the changes in free energy on changing from one aryl group to another, in either the acyl group or the leaving group, were not additive, i.e. that the effect of changing one aroyl group to another depended on the leaving group and vice versa. Thus, intramolecular cooperativity between the aroyl groups must exist, arising either from direct interaction between them or from protein-mediated interaction, or from a combination of both. Such cooperativity brings fresh opportunities and challenges to the search for novel ß-lactamase inhibitors. PMID:19678666

  13. Intramolecular hydrogen bonding in 5-nitrosalicylaldehyde: IR spectrum and quantum chemical calculations

    Science.gov (United States)

    Moosavi-Tekyeh, Zainab; Taherian, Fatemeh; Tayyari, Sayyed Faramarz

    2016-05-01

    The structural parameters, and vibrational frequencies of 5-nitrosalicylaldehyde (5NSA) were studied by the FT-IR and Raman spectra and the quantum chemical calculations carried out at the B3LYP/6-311++G(d,p) level of theory in order to investigate the intramolecular hydrogen bonding (IHB) present in its structure. The strength and nature of IHB in the optimized structure of 5NSA were studied in detail by means of the atoms in molecules (AIM) and the natural bond orbital (NBO) approaches. The results obtained were then compared with the corresponding data for its parent molecule, salicylaldehyde (SA). Comparisons made between the geometrical structures for 5NSA and SA, their OH/OD stretching and out-of-plane bending modes, their enthalpies for the hydrogen bond, and their AIM parameters demonstrated a stronger H-bonding in 5NSA compared with that in SA. The calculated binding enthalpy (ΔHbind) for 5NSA was -10.92 kcal mol-1. The observed νOH and γOH appeared at about 3120 cm-1 and 786 cm-1 respectively. The stretching frequency shift of H-bond formation was 426 cm-1 which is consistent with ΔHbind and the strength of H-bond in 5NSA. The delocalization energies and electron delocalization indices derived by the NBO and AIM approaches indicate that the resonance effects were responsible for the stronger IHB in 5NSA than in SA.

  14. Intramolecular interactions contributing for the conformational preference of bioactive diphenhydramine: Manifestation of the gauche effect

    Science.gov (United States)

    de Rezende, Fátima M. P.; Andrade, Laize A. F.; Freitas, Matheus P.

    2015-08-01

    Diphenhydramine is an antihistamine used to treat some symptoms of allergies and the common cold. It is usually marketed as the hydrochloride salt, and both the neutral and cation forms have the O-C-C-N fragment. The gauche effect is well known in fluorine-containing chains, because its main origin is hyperconjugative and the σ∗C-F is a low-lying acceptor orbital, allowing electron delocalization in the conformation where F and an adjacent electronegative substituent in an ethane fragment are in the gauche orientation. Our experimental (NMR) and theoretical findings indicate that diphenhydramine exhibits the gauche effect, since the preferential conformations have the O-C-C-N moiety in this orientation due especially to antiperiplanar σC-H → σ∗C-O and σC-H → σ∗C-N interactions. This conformational preference is strengthened in the protonated form due to an incremental electrostatic gauche effect. Because the gauche conformation matches the bioactive structure of diphenhydramine complexed with histamine methyltransferase, it is suggested that intramolecular interactions, and not only induced fit, rule its bioactive form.

  15. Hydrogen-deuterium exchange in spiro cyclic ketones: a search for intramolecular catalysis

    International Nuclear Information System (INIS)

    Hsu, R.C.L.

    1979-01-01

    The synthesis and characterization of 1'-hydroxy-3',3'-dimethylspiro[cyclohexane-1,2'-indan]-4-one (17b), 1'-amino-3',3'-dimethylspiro[cyclohexane-1,2'-indan]4-one (6a), 1'-N,N-dimethylamino-3',3'-dimethylspiro[cyclohexane-1,2'-indan]-4-one (6c) and 1'-[N-ethyl-α(d 2 )-amino]-3'-3'-dimethylspiro[cyclohexane-1,2'-indan]-4-one (6b) are described. The hydrogen-deuterium exchange reactions of aminoketones 6b and 6c with CH 3 OD are too fast to be followed by the mass spectrometric methodology. However, the H/D exchange between hydroxyketone 17b and CH 3 OD is shown to be intramolecularly catalyzed under both basic and neutral conditions. The rate constant for the exchange of C(3)-axial-H in 17b is 35 times greater than the rate constant for the exchange of an axial α-H in 4-t-butylcyclohexanone

  16. Constraints from protein structure and intra-molecular coevolution influence the fitness of HIV-1 recombinants.

    Science.gov (United States)

    Woo, Jeongmin; Robertson, David L; Lovell, Simon C

    2014-04-01

    A major challenge for developing effective treatments for HIV-1 is the viruses' ability to generate new variants. Inter-strain recombination is a major contributor to this high evolutionary rate, since at least 20% of viruses are observed to be recombinant. However, the patterns of recombination vary across the viral genome. A number of factors influence recombination, including sequence identity and secondary RNA structure. In addition the recombinant genome must code for a functional virus, and expressed proteins must fold to stable and functional structures. Any intragenic recombination that disrupts internal residue contacts may therefore produce an unfolded protein. Here we find that contact maps based on protein structures predict recombination breakpoints observed in the HIV-1 pandemic. Moreover, many pairs of contacting residues that are unlikely to be disrupted by recombination are coevolving. We conclude that purifying selection arising from protein structure and intramolecular coevolutionary changes shapes the observed patterns of recombination in HIV-1. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Intermolecular and very strong intramolecular C-SeO/N chalcogen bonds in nitrophenyl selenocyanate crystals.

    Science.gov (United States)

    Wang, Hui; Liu, Ju; Wang, Weizhou

    2018-02-14

    Single-crystal X-ray diffraction reveals that polymorphic ortho-nitrophenyl selenocyanate (o-NSC, crystals 1a and 1b) and monomorphic para-nitrophenyl selenocyanate (p-NSC, crystal 2) crystals are all stabilized mainly by intermolecular and very strong intramolecular C-SeO/N chalcogen bonds, as well as by other different interactions. Thermogravimetric (TG) and differential scanning calorimetry thermogram (DSC) analyses show that the starting decomposition temperatures and melting points of the three crystals are different, following the order 1b > 1a > 2, which is consistent with the structural characteristics of the crystals. In addition, atoms in molecules (AIM) and natural bond orbital (NBO) analyses indicate that the total strengths of the C-SeO and C-SeN chalcogen bonds decrease in the order 1b > 1a > 2. This study could be significant for engineering functional crystals based on robust C-SeO and C-SeN chalcogen bonds, and for designing drugs containing selenium as well as understanding their interaction in biosystems.

  18. Suppression of human immunodeficiency virus type 1 activity in vitro by oligonucleotides which form intramolecular tetrads.

    Science.gov (United States)

    Rando, R F; Ojwang, J; Elbaggari, A; Reyes, G R; Tinder, R; McGrath, M S; Hogan, M E

    1995-01-27

    An oligonucleotide (I100-15) composed of only deoxyguanosine and thymidine was able to inhibit human immunodeficiency virus type-1 (HIV-1) in culture assay systems. I100-15 did not block virus entry into cells but did reduce viral-specific transcripts. As assessed by NMR and polyacrylamide gel methods, I100-15 appears to form a structure in which two stacked guanosine tetrads are connected by three two-base long loops. Structure/activity experiments indicated that formation of intramolecular guanosine tetrads was necessary to achieve maximum antiviral activity. The single deoxyguanosine nucleotide present in each loop was found to be extremely important for the overall antiviral activity. The toxicity of I100-15 was determined to be well above the 50% effective dose (ED50) in culture which yielded a high therapeutic index (> 100). The addition of a cholesterol moiety to the 3' terminus of I100-15 (I100-23) reduced the ED50 value to less than 50 nM (from 0.12 microM for I100-15) and increased the duration of viral suppression to greater than 21 days (versus 7-10 days for I100-15) after removal of the drug from infected cell cultures. The favorable therapeutic index of such molecules coupled with the prolonged suppression of HIV-1, suggest that such compounds further warrant investigation as potential therapeutic agents.

  19. Intramolecular energy transfer at donor-acceptor interactions in model and biological membranes

    International Nuclear Information System (INIS)

    Umarova, Fatima T.

    2011-01-01

    Intramolecular triplet-triplet energy transfer between molecules of sensibilisator and photochrome for registration of protein interactions in the membrane preparation of Na,K-ATPase was investigated. Erythrosinithiocyanate (ERITC) was used as the triplet label of sensibilisator, and 4-acetoamido-4 -isothiocyanatostilbene-2,2 disullfonic acid (SITS) was used as the photochrome label. Na,K-ATPase preparations were covalently bound with ERITC in active centre of enzyme, and SITS molecules were covalently bound by NH2-groups. In model system, in chymotrypsinogene molecule, SITS and ERITC labels were used also. The cis-trans-isomerization of SITS was initiated by triplet-triplet energy transfer from light excited ERITC molecule to photochrome. The kinetics of isomerization was recorded by the SITS fluorescence measurements. The constant of rate of triplet-triplet energy transfer from ERITC to cis-isomers of SITS in Na,K-ATPase was determined as (3-7)x10 3 M -1 s -1 , and in model system it equals 1x 10 7 M 1 s -1 . The value of energy transfer between loos molecules of erythrosine and SITS in buffer solution equaled to 7x10 7 M -1 s -1 . This drop of R m y in the membrane preparation of Na,K-ATPase at 10 4 reflected the decrease in the frequency of label collisions caused by the increase in the media viscosity and steric hindrances. (author)

  20. Fluorescent sensors for selective detection of thiols: expanding the intramolecular displacement based mechanism to new chromophores.

    Science.gov (United States)

    Niu, Li-Ya; Zheng, Hai-Rong; Chen, Yu-Zhe; Wu, Li-Zhu; Tung, Chen-Ho; Yang, Qing-Zheng

    2014-03-21

    Biological thiols, including cysteine (Cys), homocystein (Hcy) and glutathione (GSH), play crucial roles in maintaining the appropriate redox status of biological systems. An abnormal level of biothiols is associated with different diseases, therefore, the discrimination between them is of great importance. Herein, we present two fluorescent sensors for selective detection of biothiols based on our recently reported intramolecular displacement mechanism. We expanded this mechanism to commercially available chromophores, 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) and heptamethine cyanine dye IR-780. The sensors operate by undergoing displacement of chloride by thiolate. The amino groups of Cys/Hcy further replace the thiolate to form amino-substituted products, which exhibit dramatically different photophysical properties compared to sulfur-substituted products from the reaction with GSH. NBD-Cl is highly selective towards Cys/Hcy and exhibits significant fluorescence enhancement. IR-780 showed a variation in its fluorescence ratio towards Cys over other thiols. Both of the sensors can be used for live-cell imaging of Cys. The wide applicability of the mechanism may provide a powerful tool for developing novel fluorescent sensors for selective detection of biothiols.

  1. NIR Phosphorescent Intramolecularly Bridged Benzoporphyrins and Their Application in Oxygen-Compensated Glucose Optode.

    Science.gov (United States)

    Zach, Peter W; Hofmann, Oliver T; Klimant, Ingo; Borisov, Sergey M

    2018-02-20

    A glucose optode measuring the internal oxygen gradient is presented. The multilayer biosensor is composed of (i) analyte-impermeable transparent support, (ii) first oxygen-sensing layer combined with an enzymatic layer, (iii) diffusion barrier, and (iv) second oxygen-sensing layer. To make this design suitable for measurement in subcutaneous tissue, a pair of NIR phosphorescent indicators with very different spectral properties is chosen. Combination of a conventional Pt(II) tetrabenzoporphyrin dye (absorption and emission maxima at 617 and 772 nm, respectively) used in the first layer and a new intramolecularly bridged Pt(II) complex (absorption and emission maxima at 673 and 872 nm, respectively) in the second layer enables efficient separation of both emission signals. This specially designed dye class is accessible via Scholl-reaction from tetraphenyltetrabenzoporphyrin complexes. For the first time, the new optode allows simultaneous glucose and oxygen measurement in a single spot and therefore accurate compensation of oxygen heterogeneities resulting from fluctuations in the tissue. The presented material covers the dynamic ranges from 0 to 150 hPa O 2 and from 0 to 360 mg/dL (20 mM) glucose (at 37 °C).

  2. Photoinduced symmetry-breaking intramolecular charge transfer in a quadrupolar pyridinium derivative.

    Science.gov (United States)

    Carlotti, Benedetta; Benassi, Enrico; Spalletti, Anna; Fortuna, Cosimo G; Elisei, Fausto; Barone, Vincenzo

    2014-07-21

    We report here a joint experimental and theoretical study of a quadrupolar, two-branched pyridinium derivative of interest as a potential non-linear optical material. The spectral and photophysical behaviour of this symmetric system is greatly affected by the polarity of the medium. A very efficient photoinduced intramolecular charge transfer, surprisingly more efficient than in the dipolar asymmetric analogue, is found to occur by femtosecond resolved transient absorption spectroscopy. TD-DFT calculations are in excellent agreement with these experimental findings and predict large charge displacements in the molecular orbitals describing the ground state and the lowest excited singlet state. The theoretical study also revealed that in highly polar media the symmetry of the excited state is broken giving a possible explanation to the fluorescence and transient absorption spectra resembling those of the one-branched analogous compound in the same solvents. The present study may give an important insight into the excited state deactivation mechanism of cationic (donor-π-acceptor-π-donor)(+) quadrupolar compounds characterised by negative solvatochromism, which are expected to show significant two-photon absorption (TPA). Moreover, the water solubility of the investigated quadrupolar system may represent an added value in view of the most promising applications of TPA materials in biology and medicine.

  3. The Intramolecular Hydrogen Bond N-H···S in 2,2'-Diaminodiphenyl Disulfide: Experimental and Computational Thermochemistry.

    Science.gov (United States)

    Ramos, Fernando; Flores, Henoc; Hernández-Pérez, Julio M; Sandoval-Lira, Jacinto; Camarillo, E Adriana

    2018-01-11

    The intramolecular hydrogen bond of the N-H···S type has been investigated sparingly by thermochemical and computational methods. In order to study this interaction, the standard molar enthalpies of formation in gaseous phase of diphenyl disulfide, 2,2'-diaminodiphenyl disulfide and 4,4'-diaminodiphenyl disulfide at T = 298.15 K were determined by experimental thermochemical methods and computational calculations. The experimental enthalpies of formation in gas-phase were obtained from enthalpies of formation in crystalline phase and enthalpies of sublimation. Enthalpies of formation in crystalline phase were obtained using rotatory bomb combustion calorimetry. By thermogravimetry, enthalpies of vaporization were obtained, and by combining them with enthalpies of fusion, the enthalpies of sublimation were calculated. The Gaussian-4 procedure and the atomization method were applied to obtain enthalpies of formation in gas-phase of the compounds under study. Theoretical and experimental values are in good agreement. Through natural bond orbital (NBO) analysis and a topological analysis of the electronic density, the intramolecular hydrogen bridge (N-H···S) in the 2,2'-diaminodiphenyl disulfide was confirmed. Finally, an enthalpic difference of 11.8 kJ·mol -1 between the 2,2'-diaminodiphenyl disulfide and 4,4'-diaminodiphenyl disulfide was found, which is attributed to the intramolecular N-H···S interaction.

  4. Emission Spectroscopy as a Probe into Photoinduced Intramolecular Electron Transfer in Polyazine Bridged Ru(II,Rh(III Supramolecular Complexes

    Directory of Open Access Journals (Sweden)

    Karen J. Brewer

    2010-08-01

    Full Text Available Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy and electron transfer. Changes in emission intensity, energy or band-shape, as well as excited state lifetime, provide insight into excited state dynamics. Photophysical processes such as intramolecular electron transfer between electron donor and electron acceptor sub-units may be investigated using these methods. This review investigates the use of steady-state and time-resolved emission spectroscopy to measure excited state intramolecular electron transfer in polyazine bridged Ru(II,Rh(III supramolecular complexes. Intramolecular electron transfer in these systems provides for conversion of the emissive 3MLCT (metal-to-ligand charge transfer excited state to a non-emissive, but potentially photoreactive, 3MMCT (metal-to-metal charge transfer excited state. The details of the photophysics of Ru(II,Rh(III and Ru(II,Rh(III,Ru(II systems as probed by steady-state and time-resolved emission spectroscopy will be highlighted.

  5. Heat conduction in chain polymer liquids: molecular dynamics study on the contributions of inter- and intramolecular energy transfer.

    Science.gov (United States)

    Ohara, Taku; Yuan, Tan Chia; Torii, Daichi; Kikugawa, Gota; Kosugi, Naohiro

    2011-07-21

    In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7T(c)), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors' previous study [J. Chem. Phys. 128, 044504 (2008)], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water.

  6. Intramolecular energy transfer and the driving mechanisms for large-amplitude collective motions of clusters

    Science.gov (United States)

    Yanao, Tomohiro; Koon, Wang Sang; Marsden, Jerrold E.

    2009-04-01

    This paper uncovers novel and specific dynamical mechanisms that initiate large-amplitude collective motions in polyatomic molecules. These mechanisms are understood in terms of intramolecular energy transfer between modes and driving forces. Structural transition dynamics of a six-atom cluster between a symmetric and an elongated isomer is highlighted as an illustrative example of what is a general message. First, we introduce a general method of hyperspherical mode analysis to analyze the energy transfer among internal modes of polyatomic molecules. In this method, the (3n-6) internal modes of an n-atom molecule are classified generally into three coarse level gyration-radius modes, three fine level twisting modes, and (3n-12) fine level shearing modes. We show that a large amount of kinetic energy flows into the gyration-radius modes when the cluster undergoes structural transitions by changing its mass distribution. Based on this fact, we construct a reactive mode as a linear combination of the three gyration-radius modes. It is shown that before the reactive mode acquires a large amount of kinetic energy, activation or inactivation of the twisting modes, depending on the geometry of the isomer, plays crucial roles for the onset of a structural transition. Specifically, in a symmetric isomer with a spherical mass distribution, activation of specific twisting modes drives the structural transition into an elongated isomer by inducing a strong internal centrifugal force, which has the effect of elongating the mass distribution of the system. On the other hand, in an elongated isomer, inactivation of specific twisting modes initiates the structural transition into a symmetric isomer with lower potential energy by suppressing the elongation effect of the internal centrifugal force and making the effects of the potential force dominant. This driving mechanism for reactions as well as the present method of hyperspherical mode analysis should be widely applicable to

  7. Short Intramolecular N–H⋯C(carbonyl Interactions in Mixed-Ligand Molybdenum Hexacarbonyl Derivatives

    Directory of Open Access Journals (Sweden)

    Matthew G. Budge

    2011-06-01

    Full Text Available The syntheses and single-crystal structures of Mo(CO3(phen(dipy (1, Mo(CO3(biquin(dipy (2 and Mo(CO3(dpme(dipy (3, (phen = 1,10-phenanthroline, C12H8N2; dipy = 2,2'-dipyridylamine, C10H9N3; biquin = 2,2'-biquinoline, C18H12N2; dpme = 2,2'-dipyridylmethane, C11H10N2 are described. In each case, distorted fac-MoC3N3 octahedral coordination geometries arise for the metal atoms. Short intramolecular N–H…C interactions from the dipy N–H group to a carbonyl carbon atom occur in each structure. Crystal data: 1 (C25H17MoN5O3, Mr = 531.38, monoclinic, P21/n (No. 14, Z = 4, a = 11.0965 (5 Å, b = 13.0586 (6 Å, c = 16.6138 (8 Å, b = 108.324 (1°, V = 2285.31 (18 Å3, R(F = 0.035, wR(F2 = 0.070. 2 (C31H21MoN5O3, Mr = 607.47, monoclinic, P21/n (No. 14, Z = 4, a = 11.4788 (6 Å, b = 19.073 (1 Å, c = 11.9881 (6 Å, b = 95.179 (1°, V = 2613.9 (2 Å3, R(F = 0.030, wR(F2 = 0.076. 3 (C24H19MoN5O3, Mr = 521.38, monoclinic, P21/n (No. 14, Z = 4, a = 8.4222 (3 Å, b = 21.5966 (9 Å, c = 12.5011 (5 Å, b = 94.065 (1°, V = 2268.12 (15 Å3, R(F = 0.025, wR(F2 = 0.065.

  8. Euglena gracilis ascorbate peroxidase forms an intramolecular dimeric structure: its unique molecular characterization.

    Science.gov (United States)

    Ishikawa, Takahiro; Tajima, Naoko; Nishikawa, Hitoshi; Gao, Yongshun; Rapolu, Madhusudhan; Shibata, Hitoshi; Sawa, Yoshihiro; Shigeoka, Shigeru

    2010-02-09

    Euglena gracilis lacks a catalase and contains a single APX (ascorbate peroxidase) and enzymes related to the redox cycle of ascorbate in the cytosol. In the present study, a full-length cDNA clone encoding the Euglena APX was isolated and found to contain an open reading frame encoding a protein of 649 amino acids with a calculated molecular mass of 70.5 kDa. Interestingly, the enzyme consisted of two entirely homologous catalytic domains, designated APX-N and APX-C, and an 102 amino acid extension in the N-terminal region, which had a typical class II signal proposed for plastid targeting in Euglena. A computer-assisted analysis indicated a novel protein structure with an intramolecular dimeric structure. The analysis of cell fractionation showed that the APX protein is distributed in the cytosol, but not the plastids, suggesting that Euglena APX becomes mature in the cytosol after processing of the precursor. The kinetics of the recombinant mature FL (full-length)-APX and the APX-N and APX-C domains with ascorbate and H2O2 were almost the same as that of the native enzyme. However, the substrate specificity of the mature FL-APX and the native enzyme was different from that of APX-N and APX-C. The mature FL-APX, but not the truncated forms, could reduce alkyl hydroperoxides, suggesting that the dimeric structure is correlated with substrate recognition. In Euglena cells transfected with double-stranded RNA, the silencing of APX expression resulted in a significant increase in the cellular level of H2O2, indicating the physiological importance of APX to the metabolism of H2O2.

  9. Microsolvation and the Effects of Non-Covalent Interactions on Intramolecular Dynamics

    Science.gov (United States)

    Foguel, Lidor; Vealey, Zachary; Vaccaro, Patrick

    2017-06-01

    Physicochemical processes brought about by non-covalent interactions between neighboring molecules are undeniably of crucial importance in the world around us, being responsible for effects ranging from the subtle (yet precise) control of biomolecular recognition events to the very existence of condensed phases. Of particular interest is the differential ability of distinct non-covalent forces, such as those mediated by dispersion-dominated aryl (π-π) coupling and electrostatically-driven hydrogen bonding, to affect unimolecular transformations by altering potential surface topographies and the nature of reaction coordinates. A concerted experimental and computational investigation of "microsolvation" (solvation at the molecular level) has been undertaken to elucidate the site-specific coupling between solute and solvent degrees of freedom, as well as attendant consequences for the efficiency and pathway of intrinsic proton-transfer dynamics. Targeted species have been synthesized in situ under "cold" supersonic free-jet expansion conditions (T_{rot} ≈ 1-2K) by complexing an active (proton-transfer) substrate with various ligands (e.g., water isotopologs and benzene derivatives) for which competing interaction mechanisms can lead to unique binding motifs. A series of fluorescence-based spectroscopic measurements have been performed on binary adducts formed with the prototypical 6-hydroxy-2-formylfulvene (HFF) system, where a quasi-linear intramolecular O-H...O bond and a zero-point energy that straddles the proton-transfer barrier crest synergistically yield the largest tunneling-induced splitting ever reported for the ground electronic state of an isolated neutral molecule. Such characteristics afford a localized metric for unraveling incipient changes in unimolecular reactivity, with comparison of experimentally observed and quantum-chemical predicted rovibronic landscapes serving to discriminate complexes built upon electrostatic (hydrogen-bonding) and

  10. Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: temperature dependence.

    Science.gov (United States)

    Pradhan, Tuhin; Gazi, Harun Al Rasid; Biswas, Ranjit

    2009-08-07

    Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO(4)) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-DeltaG(r)) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO(4) concentrations, and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-DeltaG(r)), the former in ethanol and ACN increases only linearly with the increase in driving force (-DeltaG(r)). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.

  11. Mechanically induced intramolecular electron transfer in a mixed-valence molecular shuttle

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, J. C.; Fahrenbach, A. C.; Dyar, S. M.; Frasconi, M.; Giesener, M. A.; Zhu, Z.; Liu, Z.; Hartlieb, K. J.; Carmieli, R.; Wasielewski, M. R.; Stoddart, J. F.

    2012-06-08

    The kinetics and thermodynamics of intramolecular electron transfer (IET) can be subjected to redox control in a bistable [2]rotaxane comprised of a dumbbell component containing an electron-rich 1,5-dioxynaphthalene (DNP) unit and an electron-poor phenylene-bridged bipyridinium (P-BIPY2+) unit and a cyclobis (paraquat-p-phenylene) (CBPQT4+) ring component. The [2]rotaxane exists in the ground-state co-conformation (GSCC) wherein the CBPQT4+ ring encircles the DNP unit. Reduction of the CBPQT4+ leads to the CBPQT2(•+) diradical dication while the P-BIPY2+ unit is reduced to its P-BIPY•+ radical cation. A radical-state co-conformation (RSCC) results from movement of the CBPQT2(•+) ring along the dumbbell to surround the P-BIPY•+ unit. This shuttling event induces IET to occur between the pyridinium redox centers of the P-BIPY•+ unit, a property which is absent between these redox centers in the free dumbbell and in the 1:1 complex formed between the CBPQT2(•+) ring and the radical cation of methyl-phenylene-viologen (MPV•+). Using electron paramagnetic resonance (EPR) spectroscopy, the process of IET was investigated by monitoring the line broadening at varying temperatures and determining the rate constant (kET = 1.33 × 107 s-1) and activation energy (ΔG‡ = 1.01 kcal mol-1) for electron transfer. These values were compared to the corresponding values predicted, using the optical absorption spectra and Marcus–Hush theory.

  12. Weak intramolecular interaction effects on the torsional spectra of ethylene glycol, an astrophysical species

    Energy Technology Data Exchange (ETDEWEB)

    Boussessi, R., E-mail: rahma.boussesi@iem.cfmac.csic.es [Departamento de Química y Física Teóricas, I. Estructura de la Materia, IEM-CSIC, Serrano 121, Madrid 28006 (Spain); Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Senent, M. L., E-mail: ml.senent@csic.es [Departamento de Química y Física Teóricas, I. Estructura de la Materia, IEM-CSIC, Serrano 121, Madrid 28006 (Spain); Jaïdane, N. [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia)

    2016-04-28

    An elaborate variational procedure of reduced dimensionality based on explicitly correlated coupled clusters calculations is applied to understand the far infrared spectrum of ethylene-glycol, an astrophysical species. This molecule can be classified in the double molecular symmetry group G{sub 8} and displays nine stable conformers, gauche and trans. In the gauche region, the effect of the potential energy surface anisotropy due to the formation of intramolecular hydrogen bonds is relevant. For the primary conformer, stabilized by a hydrogen bond, the ground vibrational state rotational constants are computed to be A{sub 0} = 15 369.57 MHz, B{sub 0} = 5579.87 MHz, and C{sub 0} = 4610.02 MHz corresponding to differences of 6.3 MHz, 7.2 MHz, and 3.5 MHz from the experimental parameters. Ethylene glycol displays very low torsional energy levels whose classification is not straightforward and requires a detailed analysis of the torsional wavefunctions. Tunneling splittings are significant and unpredictable due to the anisotropy of the potential energy surface PES. The ground vibrational state splits into 16 sublevels separated ∼142 cm{sup −1}. The splitting of the “G1 sublevels” was calculated to be ∼0.26 cm{sup −1} in very good agreement with the experimental data (0.2 cm{sup −1} = 6.95 MHz). Transitions corresponding to the three internal rotation modes allow assignment of previously observed Q branches. Band patterns, calculated between 362.3 cm{sup −1} and 375.2 cm{sup −1}, 504 cm{sup −1} and 517 cm{sup −1}, and 223.3 cm{sup −1} and 224.1 cm{sup −1}, that correspond to the tunnelling components of the v{sub 21} fundamental (v{sub 21} = OH-torsional mode), are assigned to the prominent experimental Q branches.

  13. Tunable excited-state intramolecular proton transfer reactions with Nsbnd H or Osbnd H as a proton donor: A theoretical investigation

    Science.gov (United States)

    Li, Yuanyuan; Wen, Keke; Feng, Songyan; Yuan, Huijuan; An, Beibei; Zhu, Qiuling; Guo, Xugeng; Zhang, Jinglai

    2017-12-01

    Excited-state intramolecular proton transfer (ESIPT) reactions occurring in the S1 state for five molecules, which possess five/six-membered ring intramolecular Nsbnd H···N or Osbnd H···N hydrogen bonds bearing quinoline or 2-phenylpyridine moiety, have been described in detail by the time-dependent density functional theory (TD-DFT) approach using the B3LYP hybrid functional. For the five molecules, the constrained potential energy profiles along the ESIPT reactions show that proton transfer is barrierless in molecules possessing six-membered ring intramolecular H-bonds, which is smoother than that with certain barriers in five-membered ring H-bonding systems. For the latter, chemical modification by a more strong acid group can lower the ESIPT barrier significantly, which harnesses the ESIPT reaction from a difficult type to a fast one. The energy barrier of the ESIPT reaction depends on the intensity of the intramolecular H-bond, which can be measured with the topological descriptors by topology analysis of the bond critical point (BCP) of the intramolecular H-bond. It is found that when the value of electron density ρ(r) at BCP is bigger than 0.025 a.u., the corresponding molecule might go through an ultrafast and barrierless ESIPT process, which opens a new scenario to explore the ESIPT reactions.

  14. EL APRENDIZAJE DE LOS CONCEPTOS DE FUERZAS INTERMOLECULARES E INTRAMOLECULARES MEDIANTE LA MODELIZACIÓN DIDÁCTICA

    OpenAIRE

    CHRISTIAN FERNNEY GIRALDO MACÍAS

    2013-01-01

    La modelización está siendo usada para la enseñanza y el aprendizaje en las Ciencias Naturales en diferentes contextos y para atender a diferentes problemáticas. En este caso será utilizada para explorar y analizar la relevancia que puede tener su uso en el aprendizaje de los conceptos Fuerzas Intramoleculares e Intermolecualres, partiendo de la aplicación de una serie de actividades basadas en el Ciclo Didáctico (Jorba y Sanmartí, 1996). Los datos se discuten mediante tres aspectos principal...

  15. Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

    Directory of Open Access Journals (Sweden)

    Takeshi Fujita

    2017-12-01

    Full Text Available 1,1-Difluoro-1-alkenes bearing a biaryl-2-yl group effectively underwent site-selective intramolecular iodoarylation by the appropriate cationic iodine species. Iodoarylation of 2-(2-aryl-3,3-difluoroallylbiaryls proceeded via regioselective carbon–carbon bond formation at the carbon atoms in β-position to the fluorine substituents, thereby constructing dibenzo-fused six-membered carbocycles bearing a difluoroiodomethyl group. In contrast, 2-(3,3-difluoroallylbiaryls underwent a similar cyclization at the α-carbon atoms to afford ring-difluorinated seven-membered carbocycles.

  16. Effect of structural changes in sesquifulvalene on the intramolecular charge transfer and nonlinear polarizations a theoretical study

    Science.gov (United States)

    Nandi, P. K.; Mandal, K.; Kar, T.

    2003-11-01

    Ab initio HF calculations of the ground state structural parameters, and the time dependent HF (TDHF) calculations of static nonlinear polarizabilities have been performed for a number of sesquifulvalene derivatives. The calculated NLO parameters show a good correlation with the hardness parameters. The nature of hetero-atoms and their positions can strongly influence the intramolecular charge transfer (ICT) interactions and the nonlinear polarizations of sesquifulvalene. Nonlinear polarizabilities in the twisted structures have been found to depend both on the energy barrier to twist and the transition energy corresponding to the twisted ICT (TICT) state characterized by the HOMO → LUMO transition.

  17. Tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR. An easy entry to linear bicyclic scaffolds

    Directory of Open Access Journals (Sweden)

    Javier Miró

    2015-08-01

    Full Text Available A new tandem cross enyne metathesis (CEYM–intramolecular Diels–Alder reaction (IMDAR has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.

  18. Pd(II)-catalyzed ortho-hydroxylation and intramolecular oxidative C-C coupling of N- benzylbenzene sulfonamides

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Eun Joo; Jo, Yoon Hyung; Jang, Min Jung; Youn, So Won [Dept. of Chemistry and Research Institute for Natural Sciences, Center for New Directions in Organic Synthesis, Hanyang University, Seoul (Korea, Republic of)

    2015-02-15

    We reported highly effective Pd-catalyzed C-C and/or C-N bond formations via C-H activation of aniline derivatives. Considering the lack of regioselective C(sp{sup 2}) H hydroxylation of benzylamines, our continued interest in Pd-catalyzed C-H bond functionalization prompted us to investigate the possibility of a Pd-catalyzed ortho-hydroxylation of NH-containing benzylamines. We have developed the Pd-catalyzed ortho-hydroxylation and/or intramolecular oxidative C-C coupling of N-benzyl sulfonamides, which operate through two different postulated mechanistic routes, as depicted in Scheme 2, depending on the reaction conditions.

  19. Unprecedented twofold intramolecular hydroamination in diam(m)ine-dicarboxylatodichloridoplatinum(IV) complexes - ethane-1,2-diamine vs. ammine ligands.

    Science.gov (United States)

    Reithofer, Michael R; Galanski, Markus; Arion, Vladimir B; Keppler, Bernhard K

    2008-03-07

    Reaction of (OC-6-13)-bis(2Z-3-carboxyacrylato)dichlorido(ethane-1,2-diamine)platinum(IV) and (OC-6-13)-diamminebis(2Z-3-carboxyacrylato)dichloridoplatinum(IV) with propylamine in the presence of 1,1'-carbonyl diimidazole afforded not the expected amides; instead, beside amide formation, a twofold intramolecular attack of the am(m)ine ligand at the C[double bond, length as m-dash]C bonds was observed involving either both (ethane-1,2-diamine) or only one (ammine) coordinated nitrogen atom(s).

  20. Probe development for detection of TERRA 1 intramolecular G-quadruplex formation using a fluorescent adenosine derivative.

    Science.gov (United States)

    Kim, In Sun; Seo, Young Jun

    2014-03-15

    We developed a probing system to detect the intramolecular G-quadruplex of telomeric repeat-containing RNA (TERRA 1). We used a fluorescent adenosine derivative rA(py) as a fluorophore and incorporated it into the dangling position of the parallel-type G-quadruplex sequence of TERRA 1. The rA(py)-modified G-quadruplex structure exhibited a strong fluorescence emission signal, while the emission signals of the single-strand and duplex structures were much lower. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. A classical trajectory study of the intramolecular dynamics, isomerization, and unimolecular dissociation of HO2.

    Science.gov (United States)

    Perry, Jamin W; Dawes, Richard; Wagner, Albert F; Thompson, Donald L

    2013-08-28

    The classical dynamics and rates of isomerization and dissociation of HO2 have been studied using two potential energy surfaces (PESs) based on interpolative fittings of ab initio data: An interpolative moving least-squares (IMLS) surface [A. Li, D. Xie, R. Dawes, A. W. Jasper, J. Ma, and H. Guo, J. Chem. Phys. 133, 144306 (2010)] and the cubic-spline-fitted PES reported by Xu, Xie, Zhang, Lin, and Guo (XXZLG) [J. Chem. Phys. 127, 024304 (2007)]. Both PESs are based on similar, though not identical, internally contracted multi-reference configuration interaction with Davidson correction (icMRCI+Q) electronic structure calculations; the IMLS PES includes complete basis set (CBS) extrapolation. The coordinate range of the IMLS PES is limited to non-reactive processes. Surfaces-of-section show similar generally regular phase space structures for the IMLS and XXZLG PESs with increasing energy. The intramolecular vibrational energy redistribution (IVR) at energies above and below the threshold of isomerization is slow, especially for O-O stretch excitations, consistent with the regularity in the surfaces-of-section. The slow IVR rates lead to mode-specific effects that are prominent for isomerization (on both the IMLS and XXZLG) and modest for unimolecular dissociation to H + O2 (accessible only on the XXZLG PES). Even with statistical distributions of initial energy, slow IVR rates result in double exponential decay for isomerization, with the slower rate correlated with slow IVR rates for O-O vibrational excitation. The IVR and isomerization rates computed for the IMLS and XXZLG PESs are quantitatively, but not qualitatively, different from one another with the largest differences ascribed to the ~2 kcal/mol difference in the isomerization barrier heights. The IMLS and XXZLG results are compared with those obtained using the global, semi-empirical double-many-body expansion DMBE-IV PES [M. R. Pastrana, L. A. M. Quintales, J. Brandão, and A. J. C. Varandas, J. Chem

  2. Controlling the ambiphilic nature of σ-arylpalladium intermediates in intramolecular cyclization reactions.

    Science.gov (United States)

    Solé, Daniel; Fernández, Israel

    2014-01-21

    the metal center with the carbonyl group. Second, the additive phenol exchanges the iodide ligand to give an arylpalladium(II) phenoxide complex, which has a beneficial effect on the arylation. The formation of this transient intermediate not only stabilizes the arylpalladium moiety, thus preventing the nucleophilic attack at the carbonyl group, but also assists the enolization reaction, which takes place in a more favorable intramolecular manner. The azapalladacycle intermediate is, in the words of J. R. R. Tolkien, "the one ring to bring them all and in the darkness to bind them." With this intermediate, we can easily achieve the synthesis of a variety of heterocyclic systems by selectively promoting electrophilic α-arylation or nucleophilic addition reactions from the same precursors.

  3. Relaxation dynamics in quantum dissipative systems: The microscopic effect of intramolecular vibrational energy redistribution

    Energy Technology Data Exchange (ETDEWEB)

    Uranga-Piña, L. [Facultad de Física, Universidad de la Habana, San Lázaro y L, Vedado, 10400 Havana (Cuba); Institute for Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 3, D-14195 Berlin (Germany); Tremblay, J. C., E-mail: jean.c.tremblay@gmail.com [Institute for Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 3, D-14195 Berlin (Germany)

    2014-08-21

    We investigate the effect of inter-mode coupling on the vibrational relaxation dynamics of molecules in weak dissipative environments. The simulations are performed within the reduced density matrix formalism in the Markovian regime, assuming a Lindblad form for the system-bath interaction. The prototypical two-dimensional model system representing two CO molecules approaching a Cu(100) surface is adapted from an ab initio potential, while the diatom-diatom vibrational coupling strength is systematically varied. In the weak system-bath coupling limit and at low temperatures, only first order non-adiabatic uni-modal coupling terms contribute to surface-mediated vibrational relaxation. Since dissipative dynamics is non-unitary, the choice of representation will affect the evolution of the reduced density matrix. Two alternative representations for computing the relaxation rates and the associated operators are thus compared: the fully coupled spectral basis, and a factorizable ansatz. The former is well-established and serves as a benchmark for the solution of Liouville-von Neumann equation. In the latter, a contracted grid basis of potential-optimized discrete variable representation is tailored to incorporate most of the inter-mode coupling, while the Lindblad operators are represented as tensor products of one-dimensional operators, for consistency. This procedure results in a marked reduction of the grid size and in a much more advantageous scaling of the computational cost with respect to the increase of the dimensionality of the system. The factorizable method is found to provide an accurate description of the dissipative quantum dynamics of the model system, specifically of the time evolution of the state populations and of the probability density distribution of the molecular wave packet. The influence of intra-molecular vibrational energy redistribution appears to be properly taken into account by the new model on the whole range of coupling strengths. It

  4. Reference Gene Selection in the Desert Plant <em>Eremosparton songoricuem>m>

    Directory of Open Access Journals (Sweden)

    Dao-Yuan Zhang

    2012-06-01

    Full Text Available <em>Eremosparton songoricum em>(Litv. Vass. (<em>E. songoricumem> is a rare and extremely drought-tolerant desert plant that holds promise as a model organism for the identification of genes associated with water deficit stress. Here, we cloned and evaluated the expression of eight candidate reference genes using quantitative real-time reverse transcriptase polymerase chain reactions. The expression of these candidate reference genes was analyzed in a diverse set of 20 samples including various <em>E. songoricumem> plant tissues exposed to multiple environmental stresses. GeNorm analysis indicated that expression stability varied between the reference genes in the different experimental conditions, but the two most stable reference genes were sufficient for normalization in most conditions.<em> EsEFem> and <em>Esα-TUB> were sufficient for various stress conditions, <em>EsEF> and <em>EsACT> were suitable for samples of differing germination stages, and <em>EsGAPDH>and <em>Es>UBQ em>were most stable across multiple adult tissue samples. The <em>Es18Sem> gene was unsuitable as a reference gene in our analysis. In addition, the expression level of the drought-stress related transcription factor <em>EsDREB2em>> em>verified the utility of<em> E. songoricumem> reference genes and indicated that no single gene was adequate for normalization on its own. This is the first systematic report on the selection of reference genes in <em>E. songoricumem>, and these data will facilitate future work on gene expression in this species.

  5. The effect of intramolecular donor–acceptor moieties with donor–π-bridge–acceptor structure on the solar photovoltaic performance

    Directory of Open Access Journals (Sweden)

    T. L. Wang

    2015-10-01

    Full Text Available A series of intramolecular donor–acceptor polymers containing different contents of (E-1-(2-ethylhexyl-6,9-dioctyl-2-(2-(thiophen-3-ylvinyl-1H-phenanthro[9,10-d]imidazole (thiophene-DOPI moiety and 4,4-diethylhexylcyclopenta[ 2,1-b:3,4-b']dithiophene (CPDT unit was synthesized via Grignard metathesis (GRIM polymerization. The synthesized random copolymers and homopolymer of thiophene-DOPI contain the donor–π-bridge–acceptor conjugated structure to tune the absorption spectra and energy levels of the resultant polymers. UV-vis spectra of the three polymer films exhibit panchromatic absorptions ranging from 300 to 1100 nm and low band gaps from 1.38 to 1.51 eV. It is found that more thiophene-DOPI moieties result in the decrease of band gap and lower the highest occupied molecular orbital (HOMO and lowest unoccupied molecular orbital (LUMO values of polymers. Photovoltaic performance results indicate that if the content of the intramolecular donor–acceptor moiety is high enough, the copolymer structure may be better than homopolymer due to more light-harvesting afforded by both monomer units.

  6. Intramolecular Immunological Signal Hypothesis Revived - Structural Background of Signalling Revealed by Using Congo Red as a Specific Tool

    Science.gov (United States)

    Jagusiak, A.; Konieczny, L.; Król, M.; Marszałek, P.; Piekarska, B.; Piwowar, P.; Roterman, I.; Rybarska, J.; Stopa, B.; Zemanek, G.

    2014-01-01

    Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into functionrelated unstable packing areas. Here, we have used Congo red - a supramolecular protein ligand to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold. PMID:25429660

  7. Intramolecular immunological signal hypothesis revived--structural background of signalling revealed by using Congo Red as a specific tool.

    Science.gov (United States)

    Jagusiak, A; Konieczny, L; Krol, M; Marszalek, P; Piekarska, B; Piwowar, P; Roterman, I; Rybarska, J; Stopa, B; Zemanek, G

    2015-01-01

    Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into function-related unstable packing areas. Here, we have used Congo red--a supramolecular protein ligand--to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

  8. Intramolecular cyclization of diketopiperazine formation in solid-state enalapril maleate studied by thermal FT-IR microscopic system.

    Science.gov (United States)

    Lin, Shan-Yang; Wang, Shun-Li; Chen, Ting-Fang; Hu, Ting-Chou

    2002-09-01

    The pathway of diketopiperazine (DKP) formation of solid-state enalapril maleate has been studied by using a novel Fourier transform infrared microspectroscope equipped with a thermal analyzer (thermal FT-IR microscopic system). The thermogram of the conventional differential scanning calorimetry (DSC) method was also compared. The results show new evidence of IR peaks at 3250 cm(-1) (the broad O-H stretching mode of water), and at 1738 and 1672 cm(-1) (the carbonyl band of DKP), indicating DKP formation in enalapril maleate via intramolecular cyclization. Moreover, the disappearance of IR peaks from enalapril maleate at 3215 cm(-1) (the secondary amine), 1728 cm(-1) (the carbonyl group of carboxylic acid), and 1649 cm(-1) (the carbonyl stretching of tertiary amide) also confirmed the DKP formation. The thermal FT-IR microscopic system clearly evidenced that the DKP formation in enalapril maleate started from 129 degrees C, and reached a maximum at 137 degrees C. This result was also confirmed by the conventional DSC thermogram of the compressed mixture of KBr powder and enalapril maleate, in which an endothermic peak at 144 degrees C with an extrapolated onset temperature at 137 degrees C was observed. This strongly suggests that the thermal FT-IR microscopic system was able to qualitatively detect the formation of DKP derivatives in solid-state enalapril maleate via intramolecular cyclization.

  9. Molecular simulation of caloric properties of fluids modelled by force fields with intramolecular contributions: Application to heat capacities

    Science.gov (United States)

    Smith, William R.; Jirsák, Jan; Nezbeda, Ivo; Qi, Weikai

    2017-07-01

    The calculation of caloric properties such as heat capacity, Joule-Thomson coefficients, and the speed of sound by classical force-field-based molecular simulation methodology has received scant attention in the literature, particularly for systems composed of complex molecules whose force fields (FFs) are characterized by a combination of intramolecular and intermolecular terms. The calculation of a thermodynamic property for a system whose molecules are described by such a FF involves the calculation of the residual property prior to its addition to the corresponding ideal-gas property, the latter of which is separately calculated, either using thermochemical compilations or nowadays accurate quantum mechanical calculations. Although the simulation of a volumetric residual property proceeds by simply replacing the intermolecular FF in the rigid molecule case by the total (intramolecular plus intermolecular) FF, this is not the case for a caloric property. We describe the correct methodology required to perform such calculations and illustrate it in this paper for the case of the internal energy and the enthalpy and their corresponding molar heat capacities. We provide numerical results for cP, one of the most important caloric properties. We also consider approximations to the correct calculation procedure previously used in the literature and illustrate their consequences for the examples of the relatively simple molecule 2-propanol, CH3CH(OH)CH3, and for the more complex molecule monoethanolamine, HO(CH2)2NH2, an important fluid used in carbon capture.

  10. TDDFT study on excited state intramolecular proton transfer mechanism in 2-amino-3-(2‧-benzazolyl)-quinolines

    Science.gov (United States)

    Jia, Xueli; Li, Chaozheng; Li, Donglin; Liu, Yufang

    2018-03-01

    The intramolecular proton transfer reaction of the 2-amino-3-(2‧-benzoxazolyl)-quinoline (ABO) and 2-amino-3-(2‧-benzothiazolyl)-quinoline (ABT) molecules in both S0 and S1 states at B3LYP/6-311 ++G(d,p) level in ethanol solvent have been studied to reveal the deactivation mechanism of the tautomers of the two molecules from the S1 state to the S0 state. The results show that the tautomers of ABO and ABT molecules may return to the S0 state by emitting fluorescence. In addition, the bond lengths, angles and infrared spectra are analyzed to confirm the hydrogen bonds strengthened upon photoexcitation, which can facilitate the proton transfer process. The frontier molecular orbitals (MOs) and natural bond orbital (NBO) are also calculated to indicate the intramolecular charge transfer which can be used to explore the tendency of ESIPT reaction. The potential energy surfaces of the ABO and ABT molecules in the S0 and S1 states have been constructed. According to the energy potential barrier of 9.12 kcal/mol for ABO molecule and 5.96 kcal/mol for ABT molecule, it can be indicated that the proton transfer may occur in the S1 state.

  11. Intramolecular photoinduced proton transfer in 2-(2′-hydroxyphenyl)benzazole family: A TD-DFT quantum chemical study

    Energy Technology Data Exchange (ETDEWEB)

    Roohi, Hossein, E-mail: hroohi@guilan.ac.ir; Mohtamedifar, Nafiseh; Hejazi, Fahemeh

    2014-11-24

    Highlights: • PBE1PBE/TD method was used to study the ESIPT process in the benzazole family. • Potential energy curves in ground and excited states were calculated. • Effect of substitution in benzazole ring on the ESIPT process was investigated. • In contrast to S{sub 0} state, keto form of the molecules can be formed at the S{sub 1} state. • The photophysical properties of the compounds were calculated. - Abstract: In this work, intramolecular photoinduced proton transfer in 2-(2′-hydroxyphenyl)benzazole family (HBO, HBI and HBT) was investigated using TD-DFT calculations at PBE1PBE/6-311++G(2d,2p) level of theory. The potential energy surfaces were employed to explore the proton transfer reactions in both states. In contrast to the ground state, photoexcitation from S{sub 0} state to S{sub 1} one encourages the operation of the excited-state intramolecular proton transfer process. Structural parameters, H-bonding energy, absorption and emission bands, vertical excitation and emission energies, oscillator strength, fluorescence rate constant, dipole moment, atomic charges and electron density at critical points were calculated. Molecular orbital analysis shows that vertical S{sub 0} → S{sub 1} transition in the studied molecules corresponds essentially to the excitation from HOMO (π) to LUMO (π{sup ∗}). Our calculated results are in good agreement with the experimental observations.

  12. Síntese de novas bases de tröger, fluorescentes via transferência protônica intramolecular no estado excitado (ESIPT)

    OpenAIRE

    Carlos Alberto Miranda Abella

    2003-01-01

    Neste trabalho, realizou-se a síntese e a caracterização de quatro novas bases de Tröger. Estes compostos pertencem à classe de heterociclos 2-hidroxifenibenzazóis, que caracterizam-se por apresentar uma forte emissão de fluorescência, devido à reação de transferência protônica intramolecular no estado excitado -ESIPT- por eles sofrrida quando excitados por luz ultravioleta. Os heterociclos sintetizadosapesentam ligações de hidrogênio intramolecular entrte o nitrogênio azólico e a hidroxila f...

  13. Synthesis, Crystal Structure and Luminescent Property of Cd (II Complex with <em>N-Benzenesulphonyl-L>-leucine

    Directory of Open Access Journals (Sweden)

    Xishi Tai

    2012-09-01

    Full Text Available A new trinuclear Cd (II complex [Cd3(L6(2,2-bipyridine3] [L =<em> Nem>-phenylsulfonyl-L>-leucinato] has been synthesized and characterized by elemental analysis, IR and X-ray single crystal diffraction analysis. The results show that the complex belongs to the orthorhombic, space group<em> Pem>212121 with<em> aem> = 16.877(3 Å, <em>b> em>= 22.875(5 Å, <em>c em>= 29.495(6 Å, <em>α> em>= <emem>= <emem>= 90°, <em>V> em>= 11387(4 Å3, <em>Z> em>= 4, <em>Dc>= 1.416 μg·m−3, <emem>= 0.737 mm−1, <em>F> em>(000 = 4992, and final <em>R>1 = 0.0390, <em>ωR>2 = 0.0989. The complex comprises two seven-coordinated Cd (II atoms, with a N2O5 distorted pengonal bipyramidal coordination environment and a six-coordinated Cd (II atom, with a N2O4 distorted octahedral coordination environment. The molecules form one dimensional chain structure by the interaction of bridged carboxylato groups, hydrogen bonds and p-p interaction of 2,2-bipyridine. The luminescent properties of the Cd (II complex and <em>N-Benzenesulphonyl-L>-leucine in solid and in CH3OH solution also have been investigated.

  14. Molecular Cloning and Functional Analysis of Three <em>FLOWERING LOCUS T (FTem> Homologous Genes from Chinese <em>Cymbidium>

    Directory of Open Access Journals (Sweden)

    Jaime A. Teixeira da Silva

    2012-09-01

    Full Text Available The <em>FLOWERING LOCUS Tem> (<em>FT> gene plays crucial roles in regulating the transition from the vegetative to reproductive phase. To understand the molecular mechanism of reproduction, three homologous <em>FT> genes were isolated and characterized from <em>Cymbidium sinenseem> “Qi Jian Bai Mo”, <em>Cymbidium goeringiiem> and <em>Cymbidium ensifoliumem> “Jin Si Ma Wei”. The three genes<em> em>contained 618-bp nucleotides with a 531-bp open reading frame (ORF of encoding 176 amino acids (AAs. Alignment of the AA sequences revealed that CsFT, CgFT and CeFT contain a conserved domain, which is characteristic of the<em> em>PEBP-RKIP superfamily, and which share high identity with FT of other plants in GenBank: 94% with OnFT<em> em>from <em>Oncidium em>Gower Ramsey, 79% with Hd3a from <em>Oryza sativaem>, and 74% with FT from <em>Arabidopsis thalianaem>. qRT-PCR analysis showed a diurnal expression pattern of <em>CsFT>, <em>CgFT> and <em>CeFT> following both long day (LD, 16-h light/8-h dark and short day (SD, 8-h light/16-h dark treatment. While the transcripts of both <em>CsFT em>and <em>CeFT em>under LD were significantly higher than under SD, those of <em>CgFT em>were> em>higher under SD. Ectopic expression of <em>CgFT> in transgenic <em>Arabidopsis> plants resulted in early flowering compared to wild-type plants and significant up-regulation of <em>APETALA1em> (<em>AP1em> expression. Our data indicates that CgFT is a putative phosphatidylethanolamine-binding protein gene in <em>Cymbidium> that may regulate the vegetative to reproductive transition in flowers, similar to its <em>Arabidopsis> ortholog.

  15. Characterization by time-resolved UV/Vis and infrared absorption spectroscopy of an intramolecular charge-transfer state in an organic electron-donor-bridge-acceptor system

    NARCIS (Netherlands)

    Hviid, L.; Verhoeven, J.W.; Brouwer, A.M.; Paddon-Row, M.N.; Yang, J.

    2004-01-01

    A long-lived intramolecular charge-separated state in an electron-donor-acceptor molecule is characterized by time-resolved visible and infrared absorption spectroscopy. Bands that can be assigned to the negatively charged acceptor chromophore can be clearly observed in the time-resolved IR

  16. Cobalt-Porphyrin-Catalysed Intramolecular Ring-Closing C-H Amination of Aliphatic Azides: A Nitrene-Radical Approach to Saturated Heterocycles

    NARCIS (Netherlands)

    Kuijpers, P.F.; Tiekink, M.J.; Breukelaar, W.B.; Broere, D.L.J.; van Leest, N.P.; van der Vlugt, J.I.; Reek, J.N.H.; de Bruin, B.

    2017-01-01

    Cobalt-porphyrin-catalysed intramolecular ring-closing C−H bond amination enables direct synthesis of various N-heterocycles from aliphatic azides. Pyrrolidines, oxazolidines, imidazolidines, isoindolines and tetrahydroisoquinoline can be obtained in good to excellent yields in a single reaction

  17. Ready synthesis of free N-H 2-arylindoles via the copper-catalyzed amination of 2-bromo-arylacetylenes with aqueous ammonia and sequential intramolecular cyclization.

    Science.gov (United States)

    Wang, Huifeng; Li, Yaming; Jiang, Linlin; Zhang, Rong; Jin, Kun; Zhao, Defeng; Duan, Chunying

    2011-07-07

    A wide range of free N-H 2-arylindoles were synthesised via the copper(II)-catalyzed amination of 2-bromo-arylacetylenes with aqueous ammonia and sequential intramolecular cyclization. The convenience and atom economy of aqueous ammonia, and the low cost of the copper catalytic system make this protocol readily superior in practical application.

  18. Discovery of molluscicidal and cercaricidal activities of 3-substituted quinazolinone derivatives by a scaffold hopping approach using a pseudo-ring based on the intramolecular hydrogen bond formation.

    Science.gov (United States)

    Guo, Wei; Zheng, Lv-Yin; Li, Yong-Dong; Wu, Ren-Miao; Chen, Qiang; Yang, Ding-Qiao; Fan, Xiao-Lin

    2016-06-10

    Discovery of novel topological agents against Oncomelania hupensis snails and cercariae remains a significant challenge in current Schistosomiasis control. A pseudo-ring formed from salicylanilide by an intramolecular hydrogen bond led to the discovery of 3-substituted quinazolinone derivatives which showed a potent molluscicidal and cercaricidal activities. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  19. Diastereoselective Synthesis of Novel Heterocyclic Scaffolds through Tandem Petasis 3-Component/Intramolecular Diels-Alder and ROM-RCM Reactions

    DEFF Research Database (Denmark)

    Ishøy, Mette; Petersen, Rico; Petersen, Michael Åxman

    2017-01-01

    A high-yielding, stereoselective and extraordinarily complexity generatingPetasis 3-component/intramolecular Diels-Alderreaction has been developed. In combination with ROM-RCM, rapid access to complex sp3-rich heterocyclic scaffolds amenableto subsequent functionalization and library synthesis...

  20. Photoinduced Ultrafast Intramolecular Excited-State Energy Transfer in the Silylene-Bridged Biphenyl and Stilbene (SBS) System: A Nonadiabatic Dynamics Point of View.

    Science.gov (United States)

    Wang, Jun; Huang, Jing; Du, Likai; Lan, Zhenggang

    2015-07-09

    The photoinduced intramolecular excited-state energy-transfer (EET) process in conjugated polymers has received a great deal of research interest because of its important role in the light harvesting and energy transport of organic photovoltaic materials in photoelectric devices. In this work, the silylene-bridged biphenyl and stilbene (SBS) system was chosen as a simplified model system to obtain physical insight into the photoinduced intramolecular energy transfer between the different building units of the SBS copolymer. In the SBS system, the vinylbiphenyl and vinylstilbene moieties serve as the donor (D) unit and the acceptor (A) unit, respectively. The ultrafast excited-state dynamics of the SBS system was investigated from the point of view of nonadiabatic dynamics with the surface-hopping method at the TDDFT level. The first two excited states (S1 and S2) are characterized by local excitations at the acceptor (vinylstilbene) and donor (vinylbiphenyl) units, respectively. Ultrafast S2-S1 decay is responsible for the intramolecular D-A excitonic energy transfer. The geometric distortion of the D moiety play an essential role in this EET process, whereas the A moiety remains unchanged during the nonadiabatic dynamics simulation. The present work provides a direct dynamical approach to understand the ultrafast intramolecular energy-transfer dynamics in SBS copolymers and other similar organic photovoltaic copolymers.

  1. Formal synthesis of solanoeclepin A: enantioselective allene diboration and intramolecular [2+2] photocycloaddition for the construction of the tricyclic core

    NARCIS (Netherlands)

    Kleinnijenhuis, R.A.; Timmer, B.J.J.; Lutteke, G.; Smits, J.M.M.; de Gelder, R.; van Maarseveen, J.H.; Hiemstra, H.

    2016-01-01

    An enantioselective synthesis of an intermediate in the Tanino total synthesis of solanoeclepin A has been developed. The key step was an intramolecular [2+2] photocycloaddition, which led to the tricyclo[5.2.1.0(1,6)]decane core in six steps. The first photosubstrate, prepared through an

  2. INFLUENCE OF SOLVENT ON INTRAMOLECULAR PROTON-TRANSFER IN HYDROGEN MALONATE - MOLECULAR-DYNAMICS SIMULATION STUDY OF TUNNELING BY DENSITY-MATRIX EVOLUTION AND NONEQUILIBRIUM SOLVATION

    NARCIS (Netherlands)

    MAVRI, J; BERENDSEN, HJC; VANGUNSTEREN, WF

    1993-01-01

    A density matrix evolution (DME) method (Berendsen, H. J. C.; Mavri, J. J. Phys. Chem. the preceding paper in this issue) in combination with classical molecular dynamics simulation was applied to calculate the rate of proton tunneling in the intramolecular double-well hydrogen bond of hydrogen

  3. An Efficient Synthesis of Substituted Furans by Cupric Halide-Mediated Intramolecular Halocyclization of 2-(1-Alkynyl)-2-alken-1-ones

    International Nuclear Information System (INIS)

    Fu, Weijun; Guo, Wenbo; Zhu, Mei; Xu, Chen; Xu, Fengjuan

    2013-01-01

    An efficient synthesis of 3-halofurans by the intramolecular cyclization of 2-(1-alkynyl)-2-alken-1-ones with cupric halide has been developed. A broad range of 3-chloro- and 3-bromofuran derivatives could be obtained in the present method in moderate to good yields. The 3-halofuran derivatives are potential synthetic intermediates for amplification of molecular complexity

  4. Remarkable phosphine-effect on the intramolecular aldol reactions of unsaturated 1,5-diketones: highly regioselective synthesis of cross-conjugated dienones.

    Science.gov (United States)

    Thalji, Reema K; Roush, William R

    2005-12-07

    We report a phosphine-mediated intramolecular aldol cyclization of unsaturated diketones that proceeds with extremely high levels of regioselectivity for the cross-conjugated bicyclic dienone products. The sense of regioselectivity observed in this reaction is complementary to that obtained using traditional aldol conditions. Experimental evidence that supports the involvement of a phosphine Michael adduct is described.

  5. γ‐ and δ-Lactams through Palladium-Catalyzed Intramolecular Allylic Alkylation: Enantioselective Synthesis, NMR Investigation, and DFT Rationalization

    DEFF Research Database (Denmark)

    Bantreil, Xavier; Prestat, Guillaume; Moreno, Aitor

    2011-01-01

    The Pd-catalyzed intramolecular allylic alkylation of unsaturated amides to give gamma- and delta-lactams has been studied in the presence of chiral ligands. Ligand (R)-3,5-tBu-MeOBIPHEP (MeOBIPHEP=6,6'-dimethoxybiphenyl-2,2-diyl)bis(diphenylphosphine)) afforded the best results and allowed the c...

  6. Approximate constants of motion for classically chaotic vibrational dynamics - Vague tori, semiclassical quantization, and classical intramolecular energy flow

    Science.gov (United States)

    Shirts, R. B.; Reinhardt, W. P.

    1982-01-01

    Substantial short time regularity, even in the chaotic regions of phase space, is found for what is seen as a large class of systems. This regularity manifests itself through the behavior of approximate constants of motion calculated by Pade summation of the Birkhoff-Gustavson normal form expansion; it is attributed to remnants of destroyed invariant tori in phase space. The remnant torus-like manifold structures are used to justify Einstein-Brillouin-Keller semiclassical quantization procedures for obtaining quantum energy levels, even in the absence of complete tori. They also provide a theoretical basis for the calculation of rate constants for intramolecular mode-mode energy transfer. These results are illustrated by means of a thorough analysis of the Henon-Heiles oscillator problem. Possible generality of the analysis is demonstrated by brief consideration of classical dynamics for the Barbanis Hamiltonian, Zeeman effect in hydrogen and recent results of Wolf and Hase (1980) for the H-C-C fragment.

  7. Collisional activation by MALDI tandem time-of-flight mass spectrometry induces intramolecular migration of amide hydrogens in protonated peptides

    DEFF Research Database (Denmark)

    Jørgensen, Thomas J D; Bache, Nicolai; Roepstorff, Peter

    2005-01-01

    -specific information about the incorporation of deuterium into peptides and proteins in solution. Using a unique set of peptides with their carboxyl-terminal half labeled with deuterium we have shown unambiguously that hydrogen (1H/2H) scrambling is such a dominating factor during low energy collisional activation...... of doubly protonated peptides that the original regioselective deuterium pattern of these peptides is completely erased (Jørgensen, T. J. D., Gårdsvoll, H., Ploug, M., and Roepstorff, P. (2005) Intramolecular migration of amide hydrogens in protonated peptides upon collisional activation. J. Am. Chem. Soc...... randomization among all exchangeable sites (i.e. all N- and O-linked hydrogens) also occurs upon high energy collisional activation of singly protonated peptides. This intense proton/deuteron traffic precludes the use of MALDI tandem time-of-flight mass spectrometry to obtain reliable information...

  8. Palladium-Catalyzed Intramolecular Trost-Oppolzer-Type Alder-Ene Reaction of Dienyl Acetates to Cyclopentadienes.

    Science.gov (United States)

    Bankar, Siddheshwar K; Singh, Bara; Tung, Pinku; Ramasastry, S S V

    2018-02-05

    A new approach to the synthesis of highly substituted cyclopentadienes, indenes, and cyclopentene-fused heteroarenes by means of the Pd-catalyzed Trost-Oppolzer-type intramolecular Alder-ene reaction of 2,4-pentadienyl acetates is described. This unprecedented transformation combines the electrophilic features of the Tsuji-Trost reaction with the nucleophilic features of the Alder-ene reaction. The overall outcome can be perceived as a hitherto unknown "acid-free" iso-Nazarov-type cyclization. The versatility of this strategy was further demonstrated by the formal synthesis of paucifloral F, a resveratrol-based natural product. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Visualizing the non-equilibrium dynamics of photoinduced intramolecular electron transfer with femtosecond X-ray pulses

    DEFF Research Database (Denmark)

    Canton, Sophie E.; Kjær, Kasper S.; Vankó, György

    2015-01-01

    Ultrafast photoinduced electron transfer preceding energy equilibration still poses many experimental and conceptual challenges to the optimization of photoconversion since an atomic-scale description has so far been beyond reach. Here we combine femtosecond transient optical absorption spectrosc...... states is a key mechanistic feature. The present study demonstrates the extensive potential of femtosecond X-ray techniques as diagnostics of non-adiabatic electron transfer processes in synthetic and biological systems, and some directions for future studies, are outlined....... as compared with storage ring facilities, these measurements constitute the first X-ray-based visualization of a non-equilibrated intramolecular electron transfer process over large interatomic distances. Experimental and theoretical results establish that mediation through electronically excited molecular...

  10. A non-adiabatic quantum-classical dynamics study of the intramolecular excited state hydrogen transfer in ortho-nitrobenzaldehyde.

    Science.gov (United States)

    Leyva, Verónica; Corral, Inés; Feixas, Ferran; Migani, Annapaola; Blancafort, Lluís; González-Vázquez, Jesús; González, Leticia

    2011-08-28

    Ab initio surface-hopping dynamics calculations have been performed to simulate the intramolecular excited state hydrogen transfer dynamics of ortho-nitrobenzaldehyde (o-NBA) in the gas phase from the electronic S(1) excited state. Upon UV excitation, the hydrogen is transferred from the aldehyde substituent to the nitro group, generating o-nitrosobenzoic acid through a ketene intermediate. The semiclassical propagations show that the deactivation from the S(1) is ultrafast, in agreement with the experimental measurements, which detect the ketene in less than 400 fs. The trajectories show that the deactivation mechanism involves two different conical intersections. The first one, a planar configuration with the hydrogen partially transferred, is responsible for the branching between the formation of a biradical intermediate and the regeneration of the starting material. The conversion of the biradical to the ketene corresponds to the passage through a second intersection region in which the ketene group is formed.

  11. Insights into the Intramolecular Properties of η6-Arene-Ru-Based Anticancer Complexes Using Quantum Calculations

    Directory of Open Access Journals (Sweden)

    Adebayo A. Adeniyi

    2013-01-01

    Full Text Available The factors that determine the stability and the effects of noncovalent interaction on the η6-arene ruthenium anticancer complexes are determined using DFT method. The intramolecular and intra-atomic properties were computed for two models of these half-sandwich ruthenium anticancer complexes and their respective hydrated forms. The results showed that the stability of these complexes depends largely on the network of hydrogen bonds (HB, strong nature of charge transfer, polarizability, and electrostatic energies that exist within the complexes. The hydrogen bonds strength was found to be related to the reported anticancer activities and the activation of the complexes by hydration. The metal–ligand bonds were found to be closed shell systems that are characterised by high positive Laplacian values of electron density. Two of the complexes are found to be predominantly characterised by LMCT while the other two are predominately characterised by MLCT.

  12. The Effect of Substituent Position on Excited State Intramolecular Proton Transfer in Benzoxazinone Derivatives: Experiment and DFT Calculation.

    Science.gov (United States)

    Bian, Gao-Feng; Guo, Yun; Lv, Xiao-Jing; Zhang, Cheng

    2017-01-01

    The preparation and the photophysical behaviour of two benzoxazinone derivatives isomers 2-(1-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(1) and 2-(3-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(2) designed for displaying were reported. The effect of substituent position and solvent effect on the excited state intramolecular proton transfer (ESIPT) dynamics and the spectroscopic properties were investigated using a combined theoretical (i.e., time-dependent density function theory (DFT)) and experimental (i.e., steady-state absorption and emission spectra and time-resolved fluorescence spectra) study. The results showed that compound 1 would facilitate ESIPT process and favored the keto tautomer emission, while compound 2 suppressed the ESIPT process and favored the enol emission.

  13. <em>α>-Glucosidase Inhibitory Constituents from <em>Acanthopanax senticosusem> Harm Leaves

    Directory of Open Access Journals (Sweden)

    Hai-Xue Kuang

    2012-05-01

    Full Text Available A new triterpene glycoside, 3-<em>O-[(α>-L-rhamnopyranosyl(1→2]-[<em>β>-D-glucuronopyranosyl-6-<em>O>-methyl ester]-olean-12-ene-28-olic acid (1 and a new indole alkaloid, 5-methoxy-2-oxoindolin-3-acetic acid methyl ester (5 were isolated from the leaves of <em>Acanthopanax senticosusem> Harms along with six known compounds. The structures of the new compounds were determined by means of 2D-NMR experiments and chemical methods. All the isolated compounds were evaluated for their glycosidase inhibition activities and compound 6 showed significant <em>α>-glucosidase inhibition activity.

  14. Intra-molecular electron communication, spectroscopic and conformational stability of the newly developed urethane modified polyetheramide coatings: Computational methods.

    Science.gov (United States)

    Adeniyi, Adebayo A; Akintayo, Cecilia O; Akintayo, Emmanuel T; Conradie, Jeanet

    2017-11-01

    There have been constant research efforts towards the development of new and thermally stable resins, containing properties to outdoor usage, such as high quality of adhesion, as well as resistance to water and acid, amongst others. In this computational study, the spectroscopic properties were calculated, also the intramolecular electronic communication, susceptibility, as well as conformational changes in two monomers of potential resins, namely Albiziabenth oil polyetheramide (ABOPEtA) and urethanated Albiziabenth oil polyetheramide (UABOPEtA), as well as their precursor, namely hydroxylethyl albiziabenth oil amide (HEABOA). Many of these computed properties clearly show that the urethane linkage group in UABOPEtA acts as a strong electron withdrawing group, consequently causing the rest of the molecule to be more nucleophilic. This leads to an increase in the stability of UABOPEtA, as compared the rest of the molecules, as evidenced by an increase in the intramolecular energy of interaction, as well as negative values of the polarizability exaltation index (Γ). Further UABOPEtA is also associated with higher non-linear optical properties, in terms of the hyperpolarizabilities (β) and increased aromaticity, than for molecules ABOPEtA and HEABOA. The conformational folding of molecule UABOPEtA is characterized by larger values of the bisphenol-A linkage bond angle C⋯C⋯C, contrary to the angle observed in molecule ABOPEtA. This is a direct effect of hiding the urethane unit in the cleft of the folded UABOPEtA, which clearly leads to an increase in the hydrophobicity of UABOPEtA. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. In vivo distribution and elimination of hemoglobin modified by intramolecular cross-linking with 2-nor-2-formylpyridoxal 5'-phosphate

    International Nuclear Information System (INIS)

    Bleeker, W.K.; van der Plas, J.; Feitsma, R.I.; Agterberg, J.; Rigter, G.; de Vries-van Rossen, A.; Pauwels, E.K.; Bakker, J.C.

    1989-01-01

    Modified hemoglobin solutions have potential application as plasma expanders with oxygen-transporting capacity. In a previous study it was found that modification of hemoglobin by intramolecular cross-linking with 2-nor-2-formylpyridoxal 5'-phosphate (NFPLP) improves the vascular retention time by a factor of three, and it also improves the oxygen-transporting properties. In the present study we investigated in rats how, after exchange transfusion of a clinically relevant dose, the modified hemoglobin (HbNFPLP) was distributed in the body compared with how the unmodified hemoglobin was distributed. By using a new technetium 99m labeling technique, we found in a scintigraphic study that accumulation of hemoglobin in the kidneys was greatly diminished by the intramolecular cross-linking with NFPLP. These findings were confirmed by light-microscopic observations after diaminobenzidine staining. It was concluded that the impairment of kidney function caused by blockade of the tubuli is not to be expected from HbNFPLP. In the liver and spleen, where the free HbNFPLP is possibly eliminated, some accumulation of 99mTc label was observed, but the major part of the extravascular label was diffusely spread throughout the body. This led to the conclusion that important accumulation of undegraded HbNFPLP does not occur in the liver and spleen. Rapid appearance of both hemoglobin and HbNFPLP in the lymph showed that cross-linking with NFPLP does not prevent the distribution of hemoglobin over the interstitial space in the first hours after administration. However, pharmacokinetic analysis demonstrated that transcapillary transfer contributes only to a limited extent to the disappearance from the circulation. During 24-hour infusions of HbNFPLP, a steady state with a constant plasma concentration was easily reached

  16. Intramolecular telomeric G-quadruplexes dramatically inhibit DNA synthesis by replicative and translesion polymerases, revealing their potential to lead to genetic change.

    Directory of Open Access Journals (Sweden)

    Deanna N Edwards

    Full Text Available Recent research indicates that hundreds of thousands of G-rich sequences within the human genome have the potential to form secondary structures known as G-quadruplexes. Telomeric regions, consisting of long arrays of TTAGGG/AATCCC repeats, are among the most likely areas in which these structures might form. Since G-quadruplexes assemble from certain G-rich single-stranded sequences, they might arise when duplex DNA is unwound such as during replication. Coincidentally, these bulky structures when present in the DNA template might also hinder the action of DNA polymerases. In this study, single-stranded telomeric templates with the potential to form G-quadruplexes were examined for their effects on a variety of replicative and translesion DNA polymerases from humans and lower organisms. Our results demonstrate that single-stranded templates containing four telomeric GGG runs fold into intramolecular G-quadruplex structures. These intramolecular G quadruplexes are somewhat dynamic in nature and stabilized by increasing KCl concentrations and decreasing temperatures. Furthermore, the presence of these intramolecular G-quadruplexes in the template dramatically inhibits DNA synthesis by various DNA polymerases, including the human polymerase δ employed during lagging strand replication of G-rich telomeric strands and several human translesion DNA polymerases potentially recruited to sites of replication blockage. Notably, misincorporation of nucleotides is observed when certain translesion polymerases are employed on substrates containing intramolecular G-quadruplexes, as is extension of the resulting mismatched base pairs upon dynamic unfolding of this secondary structure. These findings reveal the potential for blockage of DNA replication and genetic changes related to sequences capable of forming intramolecular G-quadruplexes.

  17. Neonatal Phosphate Nutrition Alters <em>in em>Vivo> and <em>in em>Vitro> Satellite Cell Activity in Pigs

    Directory of Open Access Journals (Sweden)

    Chad H. Stahl

    2012-05-01

    Full Text Available Satellite cell activity is necessary for postnatal skeletal muscle growth. Severe phosphate (PO4 deficiency can alter satellite cell activity, however the role of neonatal PO4 nutrition on satellite cell biology remains obscure. Twenty-one piglets (1 day of age, 1.8 ± 0.2 kg BW were pair-fed liquid diets that were either PO4 adequate (0.9% total P, supra-adequate (1.2% total P in PO4 requirement or deficient (0.7% total P in PO4 content for 12 days. Body weight was recorded daily and blood samples collected every 6 days. At day 12, pigs were orally dosed with BrdU and 12 h later, satellite cells were isolated. Satellite cells were also cultured <em>in vitroem> for 7 days to determine if PO4 nutrition alters their ability to proceed through their myogenic lineage. Dietary PO4 deficiency resulted in reduced (<em>P> < 0.05 sera PO4 and parathyroid hormone (PTH concentrations, while supra-adequate dietary PO4 improved (<em>P> < 0.05 feed conversion efficiency as compared to the PO4 adequate group. <em>In vivoem> satellite cell proliferation was reduced (<em>P> < 0.05 among the PO4 deficient pigs, and these cells had altered <em>in vitroem> expression of markers of myogenic progression. Further work to better understand early nutritional programming of satellite cells and the potential benefits of emphasizing early PO4 nutrition for future lean growth potential is warranted.

  18. Constituents from <em>Vigna em>vexillata> and Their Anti-Inflammatory Activity

    Directory of Open Access Journals (Sweden)

    Guo-Feng Chen

    2012-08-01

    Full Text Available The seeds of <em>Vigna em>genus are important food resources and there have already been many reports regarding their bioactivities. In our preliminary bioassay, the chloroform layer of methanol extracts of<em> V. vexillata em>demonstrated significant anti-inflammatory bioactivity. Therefore, the present research is aimed to purify and identify the anti-inflammatory principles of <em>V. vexillataem>. One new sterol (1 and two new isoflavones (2,3 were reported from the natural sources for the first time and their chemical structures were determined by the spectroscopic and mass spectrometric analyses. In addition, 37 known compounds were identified by comparison of their physical and spectroscopic data with those reported in the literature. Among the isolates, daidzein (23, abscisic acid (25, and quercetin (40 displayed the most significant inhibition of superoxide anion generation and elastase release.

  19. Application of the generator coordinates method to the intra-molecular proton tunneling in the malonaldehyde molecule; Aplicacao do metodo das coordenadas geradoras ao processo de tunelamento do proton intramolecular na molecula de malonaldeido

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Andre Campos Kersten

    1995-12-31

    The effects of different vibrational modes on the isomerization process of polyatomic molecules, or solvent`s effects on reaction rates are object of up-to-date interest. In general, such many body phenomena are, in principle, multidimensional, and they first require a reduction of relevant degrees of freedom. In order to investigated, some aspects of the intra-molecular proton tunneling on a malonaldehyde molecule, we use the Generator Coordinate Method. The model used to describe such a process is the so-called System-Bath model, where the system is the reaction coordinate and the bath are the intrinsic degrees of freedom (vibrational modes of the molecule), which are described by a harmonic oscillator set linearly coupled to the system. The reduction of the multidimensional problem to the effective unidimensional one is done using a energy related variational principle on the intrinsic degrees of freedom. we obtained analytically a effective Hamiltonian where the effects of the various degrees of freedom reveal themselves in the appearance of a effective mass and in changes of the shape of the potential barrier. The analyticity of the method was crucial on identifying clearly the roles played by the different physical parameters involved. (author) 17 refs., 29 figs.

  20. Excited-state intramolecular proton transfer in 3-hyroxyflavone isolated in solid argon: fluorescence and fluorescence-excitation spectra and tautomer fluorescence rise time

    Energy Technology Data Exchange (ETDEWEB)

    Dick, B.; Ernsting, N.P.

    1987-07-30

    The fluorescence properties of 3-hydroxyflavone isolated in solid argon at 15 K have been investigated. Upon electronic excitation the molecules undergo rapid intramolecular proton transfer. No fluorescence from the excited state of the normal form of the molecule could be detected. Perturbations due to hydrogen-bonding impurities which produce serious experimental problems in hydrocarbon glasses are largely suppressed in argon matrices. The rise of the green fluorescence of the tautomer was studied with excitation pulses of 230-fs duration and streak camera detection. An apparent tautomer fluorescence rise time of 2.7 ps was obtained by deconvolution. A comparative measurement of the dye coumarine 6 yielded an apparent fluorescence rise time of 2.5 ps, which can be entirely attributed to the group velocity dispersion of the streak camera optics. This indicates a rate constant for excited-state intramolecular proton transfer in 3-hydroxyflavone of greater than 10/sup 12/ s/sup -1/.

  1. Formation of an Intramolecular Periplasmic Disulfide Bond in TcpP Protects TcpP and TcpH from Degradation in Vibrio cholerae.

    Science.gov (United States)

    Morgan, Sarah J; French, Emily L; Thomson, Joshua J; Seaborn, Craig P; Shively, Christian A; Krukonis, Eric S

    2016-02-01

    TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP and ToxR are membrane-localized transcription factors, each with a periplasmic domain containing two cysteines. In ToxR, these cysteines form an intramolecular disulfide bond and a cysteine-to-serine substitution affects activity. We determined that the two periplasmic cysteines of TcpP also form an intramolecular disulfide bond. Disruption of this intramolecular disulfide bond by mutation of either cysteine resulted in formation of intermolecular disulfide bonds. Furthermore, disruption of the intramolecular disulfide bond in TcpP decreased the stability of TcpP. While the decreased stability of TcpP-C207S resulted in a nearly complete loss of toxT activation and cholera toxin (CT) production, the second cysteine mutant, TcpP-C218S, was partially resistant to proteolytic degradation and maintained ∼50% toxT activation capacity. TcpP-C218S was also TcpH independent, since deletion of tcpH did not affect the stability of TcpP-C218S, whereas wild-type TcpP was degraded in the absence of TcpH. Finally, TcpH was also unstable when intramolecular disulfides could not be formed in TcpP, suggesting that the single periplasmic cysteine in TcpH may assist with disulfide bond formation in TcpP by interacting with the periplasmic cysteines of TcpP. Consistent with this finding, a TcpH-C114S mutant was unable to stabilize TcpP and was itself unstable. Our findings demonstrate a periplasmic disulfide bond in TcpP is critical for TcpP stability and virulence gene expression. The Vibrio cholerae transcription factor TcpP, in conjunction with ToxR, regulates transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP is a membrane-localized transcription factor with a periplasmic domain containing two cysteines. We determined that the two periplasmic cysteines of TcpP form an intramolecular disulfide bond

  2. Highly asymmetric intramolecular cyclopropanation of acceptor-substituted diazoacetates by Co(II)-based metalloradical catalysis: iterative approach for development of new-generation catalysts.

    Science.gov (United States)

    Xu, Xue; Lu, Hongjian; Ruppel, Joshua V; Cui, Xin; Lopez de Mesa, Silke; Wojtas, Lukasz; Zhang, X Peter

    2011-10-05

    3,5-Di(t)Bu-QingPhyrin, a new D(2)-symmetric chiral porphyrin derived from a chiral cyclopropanecarboxamide containing two contiguous stereocenters, has been developed using an iterative approach based on Co(II)-catalyzed asymmetric cyclopropanation of alkenes. The Co(II) complex of 3,5-Di(t)Bu-QingPhyrin, [Co(P2)], has proved to be a general and effective catalyst for asymmetric intramolecular cyclopropanation of various allylic diazoacetates (especially including those with α-acceptor substituents) in high yields with excellent stereoselectivities. The [Co(P2)]-based intramolecular metalloradical cyclopropanation provides convenient access to densely functionalized 3-oxabicyclo[3.1.0]hexan-2-one derivatives bearing three contiguous quaternary and tertiary chiral centers with high enantiomeric purity.

  3. Intramolecular Rotation through Proton Transfer: [Fe(eta(5)-C5H4CO2-)(2)] Versus [(eta(5)-C5H4CO2-)Fe(eta(5)-C5H4CO2H)

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue B.; Dai, Bing; Woo, Hin-koon; Wang, Lai S.

    2005-08-12

    We report a photoelectron spectroscopic study of doubly charged (?5C5H4CO2-)Fe(?5-C5H4CO2-) (1) and singly charged (?5C5H4CO2-)Fe(?5C5H4CO2H) (2). It is shown that strong intramolecular coulomb repulsion keeps 1 in the trans-form, in which the two ?CO2- groups on the cyclopentadienyl ligands are oriented opposite to each other, whereas 2 assumes the cis-form owing to a strong intramolecular H-bond. We estimate a rotational barrier of 1.4 eV for 1 and 0.6 eV for 2. A proton transfer to 1 would result in a 112? intramolecular rotation, whereas deportation of 2 would result in a similar intramolecular rotation. Thus 1 and 2 form a model molecular rotor system, controlled by a proton transfer.

  4. CMPO-calix[4]arenes with spacer containing intramolecular hydrogen bonding: effect of local rigidification on solvent extraction toward f-block elements.

    Science.gov (United States)

    Chu, Hongzhu; He, Lutao; Jiang, Qian; Fang, Yuyu; Jia, Yiming; Yuan, Xiangyang; Zou, Shuliang; Li, Xianghui; Feng, Wen; Yang, Yuanyou; Liu, Ning; Luo, Shunzhong; Yang, Yanqiu; Yang, Liang; Yuan, Lihua

    2014-01-15

    To understand intramolecular hydrogen bonding in effecting liquid-liquid extraction behavior of CMPO-calixarenes, three CMPO-modified calix[4]arenes (CMPO-CA) 5a-5c with hydrogen-bonded spacer were designed and synthesized. The impact of spacer rotation that is hindered by introduction of intramolecular hydrogen bonding upon extraction of La(3+), Eu(3+), Yb(3+), Th(4+), and UO2(2+) has been examined. The results show that 5b and 5c containing only one hydrogen bond with a less hindered rotation spacer extract La(3+) more efficiently than 5a containing two hydrogen bonds with a more hindered rotation spacer, demonstrating the importance of local rigidification of spacer in the design of extractants in influencing the coordination environment. The large difference in extractability between La(3+) and Yb(3+) (or Eu(3+)) by 5b (or 5c), and the small difference by 5a, suggests intramolecular hydrogen bonding do exert pronounced influence upon selective extraction of light and heavy lanthanides. Log-log plot analysis indicates a 1:1, 2:1 and 1:1 stoichiometry (ligand/metal) for the extracted complex formed between 5b and La(3+), Th(4+), UO2(2+), respectively. Additionally, their corresponding acyclic analogs 7a-7c exhibit negligible extraction toward these metal ions. These results reveal the possibility of selective extraction via tuning local chelating surroundings of CMPO-CA by aid of intramolecular hydrogen bonding. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Rh2(II)-catalyzed intramolecular aliphatic C-H bond amination reactions using aryl azides as the N-atom source.

    Science.gov (United States)

    Nguyen, Quyen; Sun, Ke; Driver, Tom G

    2012-05-02

    Rhodium(II) dicarboxylate complexes were discovered to catalyze the intramolecular amination of unactivated primary, secondary, or tertiary aliphatic C-H bonds using aryl azides as the N-atom precursor. While a strong electron-withdrawing group on the nitrogen atom is typically required to achieve this reaction, we found that both electron-rich and electron-poor aryl azides are efficient sources for the metal nitrene reactive intermediate. © 2012 American Chemical Society

  6. Rh2(II)-Catalyzed Intramolecular Aliphatic C–H Bond Amination Reactions Using Aryl Azides as the N-Atom Source

    Science.gov (United States)

    Nguyen, Quyen; Sun, Ke; Driver, Tom G.

    2012-01-01

    Rhodium(II) dicarboxylate complexes were discovered to catalyze the intramolecular amination of unactivated primary-, secondary-, or tertiary aliphatic C–H bonds using aryl azides as the N-atom precursor. While a strong electron-withdrawing group on the nitrogen atom is typically required to achieve this reaction, we found that both electron-rich- and electron-poor aryl azides are efficient sources for the metal nitrene reactive intermediate. PMID:22519742

  7. Tandem Cu-catalyzed ketenimine formation and intramolecular nucleophile capture: Synthesis of 1,2-dihydro-2-iminoquinolines from 1-(o-acetamidophenylpropargyl alcohols

    Directory of Open Access Journals (Sweden)

    Gadi Ranjith Kumar

    2014-05-01

    Full Text Available The copper-catalyzed ketenimine formation reaction of 1-(o-acetamidophenylpropargyl alcohols with various sulfonyl azides is found to undergo a concomitant intramolecular nucleophile attack to generate 1,2-dihydro-2-iminoquinolines after aromatization (via elimination of acetyl and hydroxy groups and tautomerization. The reaction produces 4-substituted and 3,4-unsubstituted title compounds in moderate to good yields under mild reaction conditions.

  8. New and concise syntheses of the bicyclic oxamazin core using an intramolecular nitroso Diels-Alder reaction and ring-closing olefin metathesis.

    Science.gov (United States)

    Watson, Kyle D; Carosso, Serena; Miller, Marvin J

    2013-01-18

    Herein two new and concise synthetic approaches for making an unsaturated bicyclic oxamazin core are reported. The first involves the use of an intramolecular Diels-Alder reaction to form both of the fused rings in one step. The second approach incorporates ring-closing olefin metathesis in the final step to form the second fused ring of the core. The scope of the second approach was also expanded further to afford larger ringed bicyclic systems.

  9. Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan

    Directory of Open Access Journals (Sweden)

    Wafa Gati

    2012-12-01

    Full Text Available We have developed a general synthesis of polysubstituted 1,4-dihydropyridines and pyridines based on a highly regioselective lithiation/6-endo-dig intramolecular carbolithiation from readily available N-allyl-ynamides. This reaction, which has been successfully applied to the formal synthesis of the anti-dyskinesia agent sarizotan, further extends the use of ynamides in organic synthesis and further demonstrates the synthetic efficiency of carbometallation reactions.

  10. Magnesium-mediated intramolecular reductive coupling: a stereoselective synthesis of C(2)-symmetric 3,4-bis-silyl-substituted adipic acid derivatives.

    Science.gov (United States)

    Kundu, Pintu K; Ghosh, Sunil K

    2009-11-21

    Chiral C(2)-symmetric 3,4-bis-silyl-substituted adipic acid derivatives have been synthesised by a Mg/trimethylsilyl chloride-mediated intramolecular reductive coupling of symmetrical disiloxanes of beta-silylacrylic acid N-oxazolidinone derivatives. Efficient and short syntheses of enantiomerically pure enantiomers of 2,6-dioxabicyclo[3.3.0]octane-3,7-dione have been achieved from the bis-silylated adipic acid derivatives using Fleming-Tamao oxidation as the key step.

  11. Palladium-catalyzed intramolecular asymmetric C-H functionalization/cyclization reaction of metallocenes: an efficient approach toward the synthesis of planar chiral metallocene compounds.

    Science.gov (United States)

    Deng, Ruixian; Huang, Yunze; Ma, Xinna; Li, Gencheng; Zhu, Rui; Wang, Bin; Kang, Yan-Biao; Gu, Zhenhua

    2014-03-26

    A palladium-catalyzed asymmetric synthesis of planar chiral metallocene compounds is reported. The reaction stereoselectively functionalized one of the ortho C-H bonds of Cp rings by intramolecular cyclization to form indenone derivatives in high yields with excellent enantioselectivity. The mild set of reaction conditions allowed a wide variety of chiral metallocene compounds to be synthesized with broad functional group tolerance. The influences of preinstalled chiralities on the other Cp-ring were also investigated.

  12. Nickel-Catalyzed C-S Bond Formation via Decarbonylative Thioetherification of Esters, Amides and Intramolecular Recombination Fragment Coupling of Thioesters

    KAUST Repository

    Lee, Shao-Chi

    2018-01-15

    A nickel catalyzed cross-coupling protocol for the straightforward C-S bond formation has been developed. Various mercaptans and a wide range of ester and amide substrates bearing various substituents were tolerated in this process which afforded products in good to excellent yields. Furthermore, an intramolecular protocol for the synthesis of thioethers starting from thioesters has been developed. The utility of this protocol has been demonstrated in the synthesis of benzothiophene on the bench top.

  13. Iodine-Mediated Intramolecular Dehydrogenative Coupling: Synthesis of N-Alkylindolo[3,2-c]- and -[2,3-c]quinoline Iodides.

    Science.gov (United States)

    Volvoikar, Prajesh S; Tilve, Santosh G

    2016-03-04

    An I2/TBHP-mediated intramolecular dehydrogenative coupling reaction is developed for the synthesis of a library of medicinally important 5,11-dialkylindolo[3,2-c]quinoline salts and 5,7-dimethylindolo[2,3-c]quinoline salts. The annulation reaction is followed by aromatization to yield tetracycles in good yield. This protocol is also demonstrated for the synthesis of the naturally occurring isocryptolepine in salt form.

  14. EL APRENDIZAJE DE LOS CONCEPTOS DE FUERZAS INTERMOLECULARES E INTRAMOLECULARES MEDIANTE LA MODELIZACIÓN DIDÁCTICA

    Directory of Open Access Journals (Sweden)

    CHRISTIAN FERNNEY GIRALDO MACÍAS

    2013-07-01

    Full Text Available La modelización está siendo usada para la enseñanza y el aprendizaje en las Ciencias Naturales en diferentes contextos y para atender a diferentes problemáticas. En este caso será utilizada para explorar y analizar la relevancia que puede tener su uso en el aprendizaje de los conceptos Fuerzas Intramoleculares e Intermolecualres, partiendo de la aplicación de una serie de actividades basadas en el Ciclo Didáctico (Jorba y Sanmartí, 1996. Los datos se discuten mediante tres aspectos principales: las ideas previas de los estudiantes, el trabajo con nuevo material (nuevos conceptos, experimentos sencillos y uso de herramientas informáticas y los argumentos finales, mediante el uso de situaciones problemas. Los resultados muestran, como los estudiantes (14 y 16 años de edad evidencian un progreso conceptual al argumentar con mayor claridad las situaciones problema abordadas en el transcurso del trabajo y en la construcción de modelos más cercanos al campo científico.

  15. Rubrene: The interplay between intramolecular and intermolecular interactions determines the planarization of its tetracene core in the solid state

    KAUST Repository

    Sutton, Christopher

    2015-06-15

    Rubrene is one of the most studied molecular semiconductors; its chemical structure consists of a tetracene backbone with four phenyl rings appended to the two central fused rings. Derivatization of these phenyl rings can lead to two very different solid-state molecular conformations and packings: One in which the tetracene core is planar and there exists substantive overlap among neighboring π-conjugated backbones; and another where the tetracene core is twisted and the overlap of neighboring π-conjugated backbones is completely disrupted. State-of-the-art electronic-structure calculations show for all isolated rubrene derivatives that the twisted conformation is more favorable (by -1.7 to -4.1 kcal mol-1), which is a consequence of energetically unfavorable exchange-repulsion interactions among the phenyl side groups. Calculations based on available crystallographic structures reveal that planar conformations of the tetracene core in the solid state result from intermolecular interactions that can be tuned through well-chosen functionalization of the phenyl side groups, and lead to improved intermolecular electronic couplings. Understanding the interplay of these intramolecular and intermolecular interactions provides insight into how to chemically modify rubrene and similar molecular semiconductors to improve the intrinsic materials electronic properties.

  16. Tunable differentiation of tertiary C-H bonds in intramolecular transition metal-catalyzed nitrene transfer reactions.

    Science.gov (United States)

    Corbin, Joshua R; Schomaker, Jennifer M

    2017-04-13

    Metal-catalyzed nitrene transfer reactions are an appealing and efficient strategy for accessing tetrasubstituted amines through the direct amination of tertiary C-H bonds. Traditional catalysts for these reactions rely on substrate control to achieve site-selectivity in the C-H amination event; thus, tunability is challenging when competing C-H bonds have similar steric or electronic features. One consequence of this fact is that the impact of catalyst identity on the selectivity in the competitive amination of tertiary C-H bonds has not been well-explored, despite the potential for progress towards predictable and catalyst-controlled C-N bond formation. In this communication, we report investigations into tunable and site-selective nitrene transfers between tertiary C(sp 3 )-H bonds using a combination of transition metal catalysts, including complexes based on Ag, Mn, Rh and Ru. Particularly striking was the ability to reverse the selectivity of nitrene transfer by a simple change in the identity of the N-donor ligand supporting the Ag(i) complex. The combination of our Ag(i) catalysts with known Rh 2 (ii) complexes expands the scope of successful catalyst-controlled intramolecular nitrene transfer and represents a promising springboard for the future development of intermolecular C-H N-group transfer methods.

  17. Intramolecular C(sp(3))H amination of arylsulfonyl azides with engineered and artificial myoglobin-based catalysts.

    Science.gov (United States)

    Bordeaux, Melanie; Singh, Ritesh; Fasan, Rudi

    2014-10-15

    The direct conversion of aliphatic CH bonds into CN bonds provides an attractive approach to the introduction of nitrogen-containing functionalities in organic molecules. Following the recent discovery that cytochrome P450 enzymes can catalyze the cyclization of arylsulfonyl azide compounds via an intramolecular C(sp(3))H amination reaction, we have explored here the CH amination reactivity of other hemoproteins. Various heme-containing proteins, and in particular myoglobin and horseradish peroxidase, were found to be capable of catalyzing this transformation. Based on this finding, a series of engineered and artificial myoglobin variants containing active site mutations and non-native Mn- and Co-protoporphyrin IX cofactors, respectively, were prepared to investigate the effect of these structural changes on the catalytic activity and selectivity of these catalysts. Our studies showed that metallo-substituted myoglobins constitute viable CH amination catalysts, revealing a distinctive reactivity trend as compared to synthetic metalloporphyrin counterparts. On the other hand, amino acid substitutions at the level of the heme pocket were found to be beneficial toward improving the stereo- and enantioselectivity of these Mb-catalyzed reactions. Mechanistic studies involving kinetic isotope effect experiments indicate that CH bond cleavage is implicated in the rate-limiting step of myoglobin-catalyzed amination of arylsulfonyl azides. Altogether, these studies indicate that myoglobin constitutes a promising scaffold for the design and development of CH amination catalysts. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Intramolecular C(sp3)—H amination of arylsulfonyl azides with engineered and artificial myoglobin-based catalysts

    Science.gov (United States)

    Bordeaux, Melanie; Singh, Ritesh; Fasan, Rudi

    2014-01-01

    The direct conversion of aliphatic C—H bonds into C—N bonds provides an attractive approach to the introduction of nitrogen-containing functionalities in organic molecules. Following our recent discovery that cytochrome P450 enzymes can catalyze the cyclization of arylsulfonyl azide compounds via an intramolecular C(sp3)—H amination reaction, we have explored here the C—H amination reactivity of other hemoproteins. Various heme-containing proteins, and in particular myoglobin and horseradish peroxidase, were found to be capable of catalyzing this transformation. Based on this finding, a series of engineered and artificial myoglobin variants containing active site mutations and non-native Mn- and Co-protoporphyrin IX cofactors, respectively, were preparedWmvestigate the effect of these structural changes on the catalytic activity and selectivity of to these catalysts. Our studies showed that metallo-substituted myoglobins constitute viable C—H amination catalysts, revealing a distinctive reactivity trend as compared to synthetic metalloporphyrin counterparts. On the other hand, amino acid substitutions at the level of the heme pocket were found to be beneficial toward improving the stereo- and enantioselectivity of these Mb-catalyzed reactions. Mechanistic studies involving kinetic isotope effect experiments indicate that C—H bond cleavage is implicated in the rate-limiting step of myoglobin-catalyzed amination of arylsulfonyl azides. Altogether, these studies indicate that myoglobin constitutes a promising scaffold for the design and development of C— H amination catalysts. PMID:24890656

  19. Conformational properties of oxazole-amino acids: effect of the intramolecular N-H···N hydrogen bond.

    Science.gov (United States)

    Siodłak, Dawid; Staś, Monika; Broda, Małgorzata A; Bujak, Maciej; Lis, Tadeusz

    2014-03-06

    Oxazole ring occurs in numerous natural peptides, but conformational properties of the amino acid residue containing the oxazole ring in place of the C-terminal amide bond are poorly recognized. A series of model compounds constituted by the oxazole-amino acids occurring in nature, that is, oxazole-alanine (L-Ala-Ozl), oxazole-dehydroalanine (ΔAla-Ozl), and oxazole-dehydrobutyrine ((Z)-ΔAbu-Ozl), was investigated using theoretical calculations supported by FTIR and NMR spectra and single-crystal X-ray diffraction. It was found that the main feature of the studied oxazole-amino acids is the stable conformation β2 with the torsion angles φ and ψ of -150°, -10° for L-Ala-Ozl, -180°, 0° for ΔAla-Ozl, and -120°, 0° for (Z)-ΔAbu-Ozl, respectively. The conformation β2 is stabilized by the intramolecular N-H···N hydrogen bond and predominates in the low polar environment. In the case of the oxazole-dehydroamino acids, the π-electron conjugation that is spread on the oxazole ring and C(α)═C(β) double bond is an additional stabilizing interaction. The tendency to adopt the conformation β2 clearly decreases with increasing the polarity of environment, but still the oxazole-dehydroamino acids are considered to be more rigid and resistant to conformational changes.

  20. The effect of driving force on intramolecular electron transfer in proteins. Studies on single-site mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; van de Kamp, M

    1992-01-01

    these substitutions are not in the microenvironment separating the electron donor and acceptor, they were expected to affect the LRET rate because of their effect on the redox potential of the copper site and thus on the driving force of the reaction, as well as on the reorganization energies of the copper site....... The rate of intramolecular electron transfer from RSSR- to Cu(II) in the wild-type P. aeruginosa azurin (delta G degrees = -68.9 kJ/mol) has previously been determined to be 44 +/- 7 s-1 at 298 K, pH 7.0. The [M44K]azurin mutant (delta G degrees = -75.3 kJ/mol) was now found to react considerably faster (k...... = 134 +/- 12 s-1 at 298 K, pH 7.0) while the [H35Q]azurin mutant (delta G degrees = -65.4 kJ/mol) exhibits, within experimental error, the same specific rate (k = 52 +/- 11 s-1, 298 K, pH 7.0) as that of the wild-type azurin. From the temperature dependence of these LRET rates the following activation...

  1. Transition Metal Donor-Peptide-Acceptor Complexes: From Intramolecular Electron Transfer Reactions to the Study of Reactive Intermediates

    Energy Technology Data Exchange (ETDEWEB)

    Isied, Stephan S.

    2003-03-11

    The trans-polyproline (PII) oligomers (Figure 1) are unusually rigid peptide structures which have been extensively studied by our group for peptide mediated intramolecular electron transfer (ET) at long distances. We have previously studied ET across a series of metal ion donor (D) acceptor (A) oligoproline peptides with different distances, driving forces and reorganizational energies. The majority of these experiments involve generating the ET intermediate using pulse radiolysis methods, although more recently photochemical methods are also used. Results of these studies showed that ET across peptides can vary by more than twelve orders of magnitude. Using ruthenium bipyridine donors, ET reaction rate constants across several proline residues (n = 4 - 9) occurred in the millisecond (ms) to {micro}s timescale, thus limiting the proline peptide conformational motions to only minor changes (far smaller than the large changes that occur on the ms to sec timescale, such as trans to cis proline isomerization). The present report describes our large data base of experimental results for D-peptide-A complexes in terms of a model where the involvement of both superexchange and hopping (hole and electron) mechanisms account for the long range ET rate constants observed. Our data shows that the change from superexchange to hopping mechanisms occurs at different distances depending on the type of D and A and their interactions with the peptides. Our model is also consistent with generalized models for superexchange and hopping which have been put forward by a number of theoretical groups to account for long range ET phenomena.

  2. Intramolecular circularization increases efficiency of RNA sequencing and enables CLIP-Seq of nuclear RNA from human cells

    Science.gov (United States)

    Chu, Yongjun; Wang, Tao; Dodd, David; Xie, Yang; Janowski, Bethany A.; Corey, David R.

    2015-01-01

    RNA sequencing (RNA-Seq) is a powerful tool for analyzing the identity of cellular RNAs but is often limited by the amount of material available for analysis. In spite of extensive efforts employing existing protocols, we observed that it was not possible to obtain useful sequencing libraries from nuclear RNA derived from cultured human cells after crosslinking and immunoprecipitation (CLIP). Here, we report a method for obtaining strand-specific small RNA libraries for RNA sequencing that requires picograms of RNA. We employ an intramolecular circularization step that increases the efficiency of library preparation and avoids the need for intermolecular ligations of adaptor sequences. Other key features include random priming for full-length cDNA synthesis and gel-free library purification. Using our method, we generated CLIP-Seq libraries from nuclear RNA that had been UV-crosslinked and immunoprecipitated with anti-Argonaute 2 (Ago2) antibody. Computational protocols were developed to enable analysis of raw sequencing data and we observe substantial differences between recognition by Ago2 of RNA species in the nucleus relative to the cytoplasm. This RNA self-circularization approach to RNA sequencing (RC-Seq) allows data to be obtained using small amounts of input RNA that cannot be sequenced by standard methods. PMID:25813040

  3. Gel formation and low-temperature intramolecular conformation transition of a triple-helical polysaccharide lentinan in water.

    Science.gov (United States)

    Zhang, Yangyang; Xu, Xiaojuan; Zhang, Lina

    2008-10-01

    The gelation behavior of the triple-helical polysaccharide lentinan fractions having different molecular weights in water at 25 degrees C were studied by using a rheometer. The analysis of concentration and molecular weight dependence of shear stress and shear viscosity showed that aqueous lentinan is a typical shear-thinning fluid, possessing potential as a viscosity control agent, and that a weak gel with entangled network structure formed. The dynamic oscillatory behavior of lentinan in the temperature range of 1-15 degrees C was also investigated by rheologic method. The storage modulus G' and complex viscosity eta* increased first with decreasing temperature, and underwent a maximum centered at 7-9 degrees C, and then decreased with further decreasing temperature. This abnormal phenomenon was ascribed to formation of rigid structure in the gel state, which was confirmed by the experimental results from micro-DSC. The micro-DSC curves showed that an endothermic peak appeared at 7-9 degrees C for lentinan in water upon heating, which was attributable to the intramolecular order-disorder structure transition similar to triple-helical polysaccharide schizophyllan. Namely, at lower temperature, the side glucose residues of lentinan (triplix II) formed a well-organized triple-helical structure (triplix I) through hydrogen-bonding with the surrounding water molecules. Moreover, this conformation transition was proved to be thermally reversible. (c) 2008 Wiley Periodicals, Inc.

  4. Role of intramolecular interaction in connexin50: mediating the Ca2+-dependent binding of calmodulin to gap junction.

    Science.gov (United States)

    Zhang, Xianrong; Qi, Yipeng

    2005-08-15

    Gap junction channels formed by connexin50 (Cx50) are critical for maintenance of eye lens transparency. Cleavage of the carboxyl terminus (CT) of Cx50 to produce truncated Cx50 (Cx50trunc) occurred naturally during maturation of lens fiber cells. The mechanism of its altered properties is under confirmation. It has been suggested that calmodulin (CaM) participates in gating some kinds of gap junction. Here, we performed confocal colocalization and co-immunoprecipitation experiments to study the relationships between Cx50 and CaM. Results exhibited that the CaM could colocalize Ca2+ dependently with CT in the linear area of cell-to-cell contact formed by Cx50trunc, while it could not localize in the linear area without expression of CT. Further study indicated that the CT could interact Ca2+ independently with the cytoplasmic loop (CL) of Cx50. These data put forward the importance of Ca2+-independent intramolecular interaction between CT and CL of Cx50, which mediate the Ca2+-dependent binding of CaM to Cx50. These intra- and intermolecular interactions may further improve our understanding of biological significance of the Cx50 in the eye lens.

  5. Protection of the Queuosine Biosynthesis Enzyme QueF from Irreversible Oxidation by a Conserved Intramolecular Disulfide

    Directory of Open Access Journals (Sweden)

    Adeba Mohammad

    2017-03-01

    Full Text Available QueF enzymes catalyze the nicotinamide adenine dinucleotide phosphate (NADPH-dependent reduction of the nitrile group of 7-cyano-7-deazaguanine (preQ0 to 7-aminomethyl-7-deazaguanine (preQ1 in the biosynthetic pathway to the tRNA modified nucleoside queuosine. The QueF-catalyzed reaction includes formation of a covalent thioimide intermediate with a conserved active site cysteine that is prone to oxidation in vivo. Here, we report the crystal structure of a mutant of Bacillus subtilis QueF, which reveals an unanticipated intramolecular disulfide formed between the catalytic Cys55 and a conserved Cys99 located near the active site. This structure is more symmetric than the substrate-bound structure and exhibits major rearrangement of the loops responsible for substrate binding. Mutation of Cys99 to Ala/Ser does not compromise enzyme activity, indicating that the disulfide does not play a catalytic role. Peroxide-induced inactivation of the wild-type enzyme is reversible with thioredoxin, while such inactivation of the Cys99Ala/Ser mutants is irreversible, consistent with protection of Cys55 from irreversible oxidation by disulfide formation with Cys99. Conservation of the cysteine pair, and the reported in vivo interaction of QueF with the thioredoxin-like hydroperoxide reductase AhpC in Escherichia coli suggest that regulation by the thioredoxin disulfide-thiol exchange system may constitute a general mechanism for protection of QueF from oxidative stress in vivo.

  6. A computational investigation of the solvent-dependent enantioselective intramolecular Morita-Baylis-Hillman reaction of enones.

    Science.gov (United States)

    Singh, Nitin Kumar; Satpathi, Bishnupada; Balanarayan, P; Ramasastry, S S V

    2017-12-13

    The intramolecular Morita-Baylis-Hillman reaction of β-mono and β,β-disubstituted enones shows high yields and stereo-selective products when the reaction is performed in the presence of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as a solvent. In this work, we carried out a computational study using the density functional Becke 3-(B3) parameter exchange and the Lee-Yang-Parr (LYP) correlation functional and 6-31+G* basis set. Two major steps i.e. C-C bond formation and proton transfer were analysed using different pathways. The calculations show a very low barrier (ΔG † = 0.23 kcal mol -1 ) for C-C bond formation in the case of an experimentally dominant product. For this pathway the subsequent proton transfer via the HFIP step has a barrier of 26.98 kcal mol -1 . The same has been confirmed using a Molecular Electrostatic Potential (MESP), which shows a negative region in between CC in the transition state. In spite of high barriers for proton transfer, the intermediate products formed in this reaction pathway are thermodynamically more stable in comparison with other pathways. The thermodynamic stability of the final product in this pathway is observed to surpass all other effects in the presence of HFIP, thereby corroborating the experimentally observed enantioselectivity.

  7. The low-lying πσ* state and its role in the intramolecular charge transfer of aminobenzonitriles and aminobenzethyne

    International Nuclear Information System (INIS)

    Lee, Jae-Kwang; Fujiwara, Takashige; Kofron, William G.; Zgierski, Marek Z.; Lim, Edward C.

    2008-01-01

    Electronic absorption spectra of the low-lying ππ* and πσ* states of several aminobenzonitriles and 4-dimethylaminobenzethyne have been studied by time-resolved transient absorption and time-dependent density functional theory calculation. In acetonitrile, the lifetime of the πσ*-state absorption is very short (picoseconds or subpicosecond) for molecules that exhibit intramolecular charge transfer (ICT), and very long (nanoseconds) for those that do not. Where direct comparison of the temporal characteristics of the πσ*-state and the ICT-state transients could be made, the formation rate of the ICT state is identical to the decay rate of the πσ* state within the experimental uncertainty. These results are consistent with the πσ*-mediated ICT mechanism, L a (ππ*)→πσ*→ICT, in which the decay rate of the πσ* state is determined by the rate of the solvent-controlled πσ*→ICT charge-shift reaction. The ππ*→πσ* state crossing does not occur in 3-dimethylaminobenzonitrile or 2-dimethylaminobenzonitrile, as predicted by the calculation, and 4-aminobenzonitrile and 4-dimethylaminobenzethyne does not exhibit the ICT reaction, consistent with the higher energy of the ICT state relative to the πσ* state

  8. Spectroscopic studies of the intramolecular hydrogen bonding in o-hydroxy Schiff bases, derived from diaminomaleonitrile, and their deprotonation reaction products

    Science.gov (United States)

    Szady-Chełmieniecka, Anna; Kołodziej, Beata; Morawiak, Maja; Kamieński, Bohdan; Schilf, Wojciech

    2018-01-01

    The structural study of five Schiff bases derived from diaminomaleonitrile (DAMN) and 2-hydroxy carbonyl compounds was performed using 1H, 13C and 15N NMR methods in solution and in the solid state as well. ATR-FTIR and X-Ray spectroscopies were used for confirmation of the results obtained by NMR method. The imine obtained from DAMN and benzaldehyde was synthesized as a model compound which lacks intramolecular hydrogen bond. Deprotonation of all synthesized compounds was done by treating with tetramethylguanidine (TMG). NMR data revealed that salicylidene Schiff bases in DMSO solution exist as OH forms without intramolecular hydrogen bonds and independent on the substituents in aromatic ring. In the case of 2-hydroxy naphthyl derivative, the OH proton is engaged into weak intramolecular hydrogen bond. Two of imines (salDAMN and 5-BrsalDAMN) exist in DMSO solution as equilibrium mixtures of two isomers (A and B). The structures of equilibrium mixture in the solid state have been studied by NMR, ATR-FTIR and X-Ray methods. The deprotonation of three studied compounds (salDAMN, 5-BrsalDAMN, and 5-CH3salDAMN) proceeded in two different ways: deprotonation of oxygen atom (X form) or of nitrogen atom of free primary amine group of DAMN moiety (Y form). For 5-NO2salDAMN and naphDAMN only one form (X) was observed.

  9. Theoretical study on the excited-state intramolecular proton-transfer reaction of 10-hydroxybenzo[h]quinoline in methanol and cyclohexane

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Meng [Department of Chemistry, Liaoning University, Shenyang 110036 (China); State Key Lab of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Zhao, Jinfeng [Department of Physics, Liaoning University, Shenyang 110036 (China); State Key Lab of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Cui, Yanling; Wang, Qianyu [Department of Physics, Liaoning University, Shenyang 110036 (China); Dai, Yumei [Normal College, Shenyang University, Shenyang 110044 (China); Song, Peng, E-mail: songpeng@lnu.edu.cn [Department of Physics, Liaoning University, Shenyang 110036 (China); Xia, Lixin, E-mail: lixinxia@lnu.edu.cn [Department of Chemistry, Liaoning University, Shenyang 110036 (China)

    2015-05-15

    The dynamics of the excited-state intramolecular proton-transfer (ESIPT) reaction of 10-hydroxybenzoquinoline (HBQ) in different solvents, have been investigated based on the time-dependent density functional theory (TD-DFT) in detail. Upon excitation, the intramolecular hydrogen bond between the hydroxyl and phenanthrene functionality is significantly strengthened in the S{sub 1} state, which can be used as a reasonable tendency for facilitating the ESIPT process. In addition, the calculated vertical excitation energies in the S{sub 0} state and S{sub 1} state reproduce the experimental UV–vis absorbance and fluorescence emission spectra well. Through calculating the fluorescence spectra of the HBQ chromophore, two outcomes for this chromophore were found in the S{sub 1} state, which demonstrates that the ESIPT process occurs. The potential energy curves have been calculated to account for the mechanism of the proton-transfer process in the excited-state. As a result, the barrierless ESIPT process can occur in the S{sub 1} state with proton transfer from the O atom to the N atom. And maybe the ESIPT process is easier in methanol solvent due to the higher potential energy difference. - Highlights: • The hydrogen bond between the hydroxyl and phenanthrene is strengthened. • The hydrogen bond facilitates the proton transfer from the hydroxyl group to the N atom. • The spontaneous excited-state intramolecular proton transfer reaction can be observed.

  10. A theoretical investigation on the regioselectivity of the intramolecular hetero Diels-Alder and 1,3-dipolar cycloaddition of 2-vinyloxybenzaldehyde derivatives

    Directory of Open Access Journals (Sweden)

    Hamzehloueian Mahshid

    2014-01-01

    Full Text Available The present study reports a systematic computational analysis of the two possible pathways, fused and bridged, for an intramolecular hetero Diels-Alder (IMHDA and an intramolecular 1,3-dipolar cycloaddition (IMDCA of 2-vinyloxybenzaldehyde derivatives. The potential energy surface analysis for both reactions is in agreement with experimental observations. The activation energies associated with the two regioisomeric channels in IMHDA reaction show that the bridged product is favored, although in IMDCA, the most stable TS results the fused product. The global electronic properties of fragments within each molecule were studied to discuss the reactivity patterns and charge transfer direction in the intramolecular processes. The asynchronicity of the bond formation and aromaticity of the optimized TSs in the Diels-Alder reaction as well as cycloaddition reaction were evaluated. Finally, 1H NMR chemical shifts of the possible regioisomers have been calculated using the GIAO method which of the most stable products are in agreement with the experimental data in the both reaction.

  11. Photochromism in <em>p>-methylbenzoylthioacetone and related <em>β>-thioxoketones

    DEFF Research Database (Denmark)

    Gorski, Alexander; Posokhov, Yevgen; Hansen, Bjarke Knud Vilster

    2007-01-01

    Irradiation of p-methylbenzoylthioacetone with UV or visible light brings about spectral changes characteristic for the photochromic behavior of β-thioxoketones. The nature of the initial species and of the photochromic product can be assigned based on spectral studies of the electronic and IR...... with the results previously obtained for three related molecules: thioacetylacetone, p-methyl(thiobenzoyl)acetone, and monothiodibenzoylmethane reveals a common pattern of the photochromic reaction. In all four molecules, the initial species corresponds to an intramolecularly hydrogen-bonded enolic molecular...

  12. Dermatoses em renais cronicos em terapia dialitica

    Directory of Open Access Journals (Sweden)

    Luis Alberto Batista Peres

    2014-03-01

    Full Text Available Objetivo: As desordens cutâneas e das mucosas são comuns em pacientes em hemodiálise a longo prazo. A diálise prolonga a expectativa de vida, dando tempo para a manifestação destas anormalidades. Os objetivos deste estudo foram avaliar a prevalência de problemas dermatológicos em pacientes com doença renal crônica (DRC em hemodiálise. Métodos: Cento e quarenta e cinco pacientes com doença renal crônica em hemodiálise foram estudados. Todos os pacientes foram completamente analisados para as alterações cutâneas, de cabelos, mucosas e unhas por um único examinador e foram coletados dados de exames laboratoriais. Os dados foram armazenados em um banco de dados do Microsolft Excel e analisados por estatística descritiva. As variáveis contínuas foram comparadas pelo teste t de Student e as variáveis categóricas utilizando o teste do qui-quadrado ou o teste Exato de Fischer, conforme adequado. Resultados: O estudo incluiu 145 pacientes, com idade média de 53,6 ± 14,7 anos, predominantemente do sexo masculino (64,1% e caucasianos (90,0%. O tempo médio de diálise foi de 43,3 ± 42,3 meses. As principais doenças subjacentes foram: hipertensão arterial em 33,8%, diabetes mellitus em 29,6% e glomerulonefrite crônica em 13,1%. As principais manifestações dermatológicas observadas foram: xerose em 109 (75,2%, equimose em 87 (60,0%, prurido em 78 (53,8% e lentigo em 33 (22,8% pacientes. Conclusão: O nosso estudo mostrou a presença de mais do que uma dermatose por paciente. As alterações cutâneas são frequentes em pacientes em diálise. Mais estudos são necessários para melhor caracterização e manejo destas dermatoses.

  13. Definition of an intramolecular Eu-to-Eu energy transfer within a discrete [Eu2L] complex in solution.

    Science.gov (United States)

    Nonat, Aline; Regueiro-Figueroa, Martín; Esteban-Gómez, David; de Blas, Andrés; Rodríguez-Blas, Teresa; Platas-Iglesias, Carlos; Charbonnière, Loïc J

    2012-06-25

    Ligand L, based on two do3a moieties linked by the methylene groups of 6,6'-dimethyl-2,2'-bipyridine, was synthesized and characterized. The addition of Ln salts to an aqueous solution of L (0.01 M Tris-HCl, pH 7.4) led to the successive formation of [LnL] and [Ln(2)L] complexes, as evidenced by UV/Vis and fluorescence titration experiments. Homodinuclear [Ln(2)L] complexes (Ln = Eu, Gd, Tb, Yb, and Lu) were prepared and characterized. The (1)H and (13)C NMR spectra of the Lu and Yb complexes in D(2)O solution (pD = 7.0) showed C(1) symmetry of these species in solution, pointing to two different chemical environments for the two lanthanide cations. The analysis of the chemical shifts of the Yb complex indicated that the two coordination sites present square antiprismatic (SAP) coordination environments around the metal ions. The spectroscopic properties of the [Tb(2)L] complex upon ligand excitation revealed conventional behavior with τ(H2O) = 2.05(1) ms and ϕ(H2O) = 51%, except for the calculation of the hydration number obtained from the luminescent lifetimes in H(2)O and D(2)O, which pointed to a non-integer value of 0.6 water molecules per Tb(III) ion. In contrast, the Eu complex revealed surprising features such as: 1) the presence of two and up to five components in the (5)D(0)→(7)F(0) and (5)D(0)→(7)F(1) emission bands, respectively; 2) marked differences between the normalized spectra obtained in H(2)O and D(2)O solutions; and 3) unconventional temporal evolution of the luminescence intensity at certain wavelengths, the intensity profile first displaying a rising step before the occurrence of the expected decay. Additional spectroscopic experiments performed on [Gd(2-x)Eu(x)L] complexes (x = 0.1 and 1.9) confirmed the presence of two distinct Eu sites with hydration numbers of 0 (site I) and 2 (site II), and showed that the unconventional temporal evolution of the emission intensity is the result of an unprecedented intramolecular Eu

  14. Quantum dynamics study of fulvene double bond photoisomerization: The role of intramolecular vibrational energy redistribution and excitation energy

    Energy Technology Data Exchange (ETDEWEB)

    Blancafort, Lluis [Institut de Quimica Computacional, Department de Quimica, Universitat de Girona, Campus de Montilivi, 17071 Girona (Spain); Gatti, Fabien [CTMM, Institut Charles Gerhardt Montpellier (UMR 5253), CC 1501, Universite Montpellier 2, 34095 Montpellier Cedex 05 (France); Meyer, Hans-Dieter [Theoretische Chemie, Ruprecht-Karls-Universitaet, Im Neuenheimer Feld 229, 69120 Heidelberg (Germany)

    2011-10-07

    The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.

  15. Quantum dynamics study of fulvene double bond photoisomerization: The role of intramolecular vibrational energy redistribution and excitation energy

    International Nuclear Information System (INIS)

    Blancafort, Lluis; Gatti, Fabien; Meyer, Hans-Dieter

    2011-01-01

    The double bond photoisomerization of fulvene has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method. Fulvene is a test case to develop optical control strategies based on the knowledge of the excited state decay mechanism. The decay takes place on a time scale of several hundred femtoseconds, and the potential energy surface is centered around a conical intersection seam between the ground and excited state. The competition between unreactive decay and photoisomerization depends on the region of the seam accessed during the decay. The dynamics are carried out on a four-dimensional model surface, parametrized from complete active space self-consistent field calculations, that captures the main features of the seam (energy and locus of the seam and associated branching space vectors). Wave packet propagations initiated by single laser pulses of 5-25 fs duration and 1.85-4 eV excitation energy show the principal characteristics of the first 150 fs of the photodynamics. Initially, the excitation energy is transferred to a bond stretching mode that leads the wave packet to the seam, inducing the regeneration of the reactant. The photoisomerization starts after the vibrational energy has flowed from the bond stretching to the torsional mode. In our propagations, intramolecular energy redistribution (IVR) is accelerated for higher excess energies along the bond stretch mode. Thus, the competition between unreactive decay and isomerization depends on the rate of IVR between the bond stretch and torsion coordinates, which in turn depends on the excitation energy. These results set the ground for the development of future optical control strategies.

  16. The KIM-family protein-tyrosine phosphatases use distinct reversible oxidation intermediates: Intramolecular or intermolecular disulfide bond formation.

    Science.gov (United States)

    Machado, Luciana E S F; Shen, Tun-Li; Page, Rebecca; Peti, Wolfgang

    2017-05-26

    The kinase interaction motif (KIM) family of protein-tyrosine phosphatases (PTPs) includes hematopoietic protein-tyrosine phosphatase (HePTP), striatal-enriched protein-tyrosine phosphatase (STEP), and protein-tyrosine phosphatase receptor type R (PTPRR). KIM-PTPs bind and dephosphorylate mitogen-activated protein kinases (MAPKs) and thereby critically modulate cell proliferation and differentiation. PTP activity can readily be diminished by reactive oxygen species (ROS), e.g. H 2 O 2 , which oxidize the catalytically indispensable active-site cysteine. This initial oxidation generates an unstable sulfenic acid intermediate that is quickly converted into either a sulfinic/sulfonic acid (catalytically dead and irreversible inactivation) or a stable sulfenamide or disulfide bond intermediate (reversible inactivation). Critically, our understanding of ROS-mediated PTP oxidation is not yet sufficient to predict the molecular responses of PTPs to oxidative stress. However, identifying distinct responses will enable novel routes for PTP-selective drug design, important for managing diseases such as cancer and Alzheimer's disease. Therefore, we performed a detailed biochemical and molecular study of all KIM-PTP family members to determine their H 2 O 2 oxidation profiles and identify their reversible inactivation mechanism(s). We show that despite having nearly identical 3D structures and sequences, each KIM-PTP family member has a unique oxidation profile. Furthermore, we also show that whereas STEP and PTPRR stabilize their reversibly oxidized state by forming an intramolecular disulfide bond, HePTP uses an unexpected mechanism, namely, formation of a reversible intermolecular disulfide bond. In summary, despite being closely related, KIM-PTPs significantly differ in oxidation profiles. These findings highlight that oxidation protection is critical when analyzing PTPs, for example, in drug screening. © 2017 by The American Society for Biochemistry and Molecular Biology

  17. Dimerization of HNO in aqueous solution: an interplay of solvation effects, fast acid-base equilibria, and intramolecular hydrogen bonding?

    Science.gov (United States)

    Fehling, Carsten; Friedrichs, Gernot

    2011-11-09

    The recent unraveling of the rather complex acid-base equilibrium of nitroxyl (HNO) has stimulated a renewed interest in the significance of HNO for biology and pharmacy. HNO plays an important role in enzymatic mechanisms and is discussed as a potential therapeutic agent against heart failure. A cumbersome property for studying HNO reactions, its fast dimerization leading to the rapid formation of N(2)O, is surprisingly far from being well understood. It prevents isolation and limits intermediate concentrations of nitroxyl in solution. In this study, a new mechanism for the HNO dimerization reaction in aqueous solution has been theoretically derived on the basis of DFT calculations. Detailed analysis of the initial reaction step suggests a reversal of the cis-trans isomer preference in solution compared to the corresponding gas phase reaction. In contrast to a gas phase derived model based on intramolecular rearrangement steps, an acid-base equilibrium model is in agreement with previous experimental findings and, moreover, explains the fundamental differences between the well studied gas phase reaction and the solvent reaction in terms of polarity, cis-trans isomerizations, and acidities of the intermediates. In the case of cis-hyponitrous acid, the calculated pK(a) values of the acid-base equilibria were found to be significantly different from the corresponding experimental value of the stable trans isomer. Under physiological conditions, N(2)O formation is dominated by the decomposition of the unstable monoanion cis-N(2)O(2)H(-) rather than that of the commonly stated cis-HONNOH.

  18. A Reversible, Charge-Induced Intramolecular C4a-S-Cysteinyl-Flavin in Choline Oxidase Variant S101C.

    Science.gov (United States)

    Su, Dan; Yuan, Hongling; Gadda, Giovanni

    2017-12-26

    Choline oxidase serves as a paradigm for alcohol oxidation catalyzed by flavin-dependent enzymes. In its active site, S101 is 4 Å from the flavin C4a atom on an extended loop. Enzyme variants substituted at S101 were generated in a previous study and investigated mechanistically [Yuan, H., and Gadda, G. (2011) Biochemistry 50, 770-779]. In this study, the typical ultraviolet-visible (UV-vis) absorption spectrum of oxidized flavin was observed for the S101C enzyme in HEPES, TES, or sodium phosphate, whereas an absorption spectrum suggesting the presence of a C4a-flavin adduct with cysteine was obtained in Tris-HCl at pH 8.0. pH titrations of the UV-vis absorption spectrum of the wild-type, S101A, S101C, and H99N enzymes in the presence and absence of Tris allowed for the determination of two pK a values that define a pH range in which the C4a-S-cysteinyl flavin is stabilized. Inhibition studies and stopped-flow kinetics demonstrated that binding of protonated Tris in the active site of the S101C enzyme is required to form the C4a-S-cysteinyl flavin. Deuterium kinetic isotope effects and proton inventories of the S101C enzyme mixed in a stopped-flow spectrophotometer with Tris established a mechanism for the reversible formation of the C4a-S-cysteinyl flavin. This study provides a detailed mechanistic analysis of the reversible formation of a bicovalent C4a-S-cysteinyl-8α-N 3 -histidyl flavin in choline oxidase, identifying an optimal pH range and a mechanistic rationale for the stabilization of de novo C4a-S-cysteinyl-flavins. Moreover, it presents an example of an intramolecular reaction of an enzyme-bound flavin without a substrate.

  19. Intramolecular structures in a single copolymer chain consisting of flexible and semiflexible blocks: Monte Carlo simulation of a lattice model

    International Nuclear Information System (INIS)

    Martemyanova, Julia A; Ivanov, Victor A; Paul, Wolfgang

    2014-01-01

    We study conformational properties of a single multiblock copolymer chain consisting of flexible and semiflexible blocks. Monomer units of different blocks are equivalent in the sense of the volume interaction potential, but the intramolecular bending potential between successive bonds along the chain is different. We consider a single flexible-semiflexible regular multiblock copolymer chain with equal content of flexible and semiflexible units and vary the length of the blocks and the stiffness parameter. We perform flat histogram type Monte Carlo simulations based on the Wang-Landau approach and employ the bond fluctuation lattice model. We present here our data on different non-trivial globular morphologies which we have obtained in our model for different values of the block length and the stiffness parameter. We demonstrate that the collapse can occur in one or in two stages depending on the values of both these parameters and discuss the role of the inhomogeneity of intraglobular distributions of monomer units of both flexible and semiflexible blocks. For short block length and/or large stiffness the collapse occurs in two stages, because it goes through intermediate (meta-)stable structures, like a dumbbell shaped conformation. In such conformations the semiflexible blocks form a cylinder-like core, and the flexible blocks form two domains at both ends of such a cylinder. For long block length and/or small stiffness the collapse occurs in one stage, and in typical conformations the flexible blocks form a spherical core of a globule while the semiflexible blocks are located on the surface and wrap around this core.

  20. Intramolecular localization and effect on conformational stability in vitro of irreversible interphase phosphorylation of Physarum histone H1

    International Nuclear Information System (INIS)

    Jerzmanowski, A.; Krezel, A.M.

    1986-01-01

    To elucidate the intramolecular localization of irreversible interphase phosphorylation of Physarum histone H1 and its effect on H1,s conformational properties, the circular dichroism spectra, the pH- and salt-dependent folding, and the products of trypsin digestion for the interphase phosphorylated (with five to nine phosphates per molecule) and enzymatically dephosphorylated H1 were compared. Both phosphorylated and dephosphorylated H1 show similar amounts of helicity at high ionic strength and upon limited digestion with trysin form identical trypsin-resistant peptides of the size slightly larger than the analogous peptide from calf thymus H1. The circular dichroism analysis of the pH-dependent folding of Physarum H1 in water shows a strong effect of phosphorylation on the folding process in both the acidic and alkaline pH region. The analysis of the products of trypsin digestion of [ 32 P] PO 4 -labeled Physarum H1 before and after enzymatic dephosphorylation is consistent with the interpretation that the interphase phosphorylation occurs predominantly within the 50-70 amino acid sequence directly adjacent to the trypsin-resistant peptide on its C-terminal side and that this sequence is itself involved in some kind of loose folding at high ionic strength. The studies of the formation of the trypsin-resistant peptide (the globular domain) as a function of salt concentration show that it is induced at 300 mM lower NaCl concentration for phosphorylated than for dephosphorylated H1. These results indicate that the stable, interphase phosphorylation of Physarum H1 enhances the salt-induced formation of the folded globular region in vitro. This conclusion together with the finding that only nonphosphorylated H1 occurs in the DNase I solubilized fraction of Physarum chromatin may be relevant for a mechanism of chromatin activation in Physarum

  1. Combining short- and long-range fluorescence reporters with simulations to explore the intramolecular dynamics of an intrinsically disordered protein

    Science.gov (United States)

    Zosel, Franziska; Haenni, Dominik; Soranno, Andrea; Nettels, Daniel; Schuler, Benjamin

    2017-10-01

    Intrinsically disordered proteins (IDPs) are increasingly recognized as a class of molecules that can exert essential biological functions even in the absence of a well-defined three-dimensional structure. Understanding the conformational distributions and dynamics of these highly flexible proteins is thus essential for explaining the molecular mechanisms underlying their function. Single-molecule fluorescence spectroscopy in combination with Förster resonance energy transfer (FRET) is a powerful tool for probing intramolecular distances and the rapid long-range distance dynamics in IDPs. To complement the information from FRET, we combine it with photoinduced electron transfer (PET) quenching to monitor local loop-closure kinetics at the same time and in the same molecule. Here we employed this combination to investigate the intrinsically disordered N-terminal domain of HIV-1 integrase. The results show that both long-range dynamics and loop closure kinetics on the sub-microsecond time scale can be obtained reliably from a single set of measurements by the analysis with a comprehensive model of the underlying photon statistics including both FRET and PET. A more detailed molecular interpretation of the results is enabled by direct comparison with a recent extensive atomistic molecular dynamics simulation of integrase. The simulations are in good agreement with experiment and can explain the deviation from simple models of chain dynamics by the formation of persistent local secondary structure. The results illustrate the power of a close combination of single-molecule spectroscopy and simulations for advancing our understanding of the dynamics and detailed mechanisms in unfolded and intrinsically disordered proteins.

  2. Intramolecular interactions stabilizing compact conformations of the intrinsically disordered kinase-inhibitor domain of Sic1: a molecular dynamics investigation.

    Directory of Open Access Journals (Sweden)

    Matteo eLambrughi

    2012-11-01

    Full Text Available Cyclin-dependent kinase inhibitors (CKIs are key regulatory proteins of the eukaryotic cell cycle, which modulate cyclin-dependent kinase (Cdk activity. CKIs perform their inhibitory effect by the formation of ternary complexes with a target kinase and its cognate cyclin. These regulators generally belong to the class of intrinsically disordered proteins (IDPs, which lack a well-defined and organized three-dimensional structure in their free state, undergoing folding upon binding to specific partners. Unbound IDPs are not merely random-coil structures, but can present intrinsically folded structural units (IFSUs and collapsed conformations. These structural features can be relevant to protein function in vivo.The yeast CKI Sic1 is a 284-amino acid IDP that binds to Cdk1 in complex with the Clb5,6 cyclins, preventing phosphorylation of G1 substrates and, therefore, entrance to the S phase. Sic1 degradation, triggered by multiple phosphorylation events, promotes cell-cycle progression. Previous experimental studies pointed out a propensity of Sic1 and its isolated domains to populate both extended and compact conformations. The present contribution provides models of the compact conformations of the Sic1 kinase-inhibitory domain (KID by all-atom molecular-dynamics simulations in explicit solvent and in the absence of interactors. The results are integrated by spectroscopic and spectrometric data. Helical IFSUs are identified, along with networks of intramolecular interactions. The results identify a group of hub residues and electrostatic interactions which are likely to be involved in the stabilization of globular states.

  3. EM International. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    1993-07-01

    It is the intent of EM International to describe the Office of Environmental Restoration and Waste Management`s (EM`s) various roles and responsibilities within the international community. Cooperative agreements and programs, descriptions of projects and technologies, and synopses of visits to international sites are all highlighted in this semiannual journal. Focus on EM programs in this issue is on international collaboration in vitrification projects. Technology highlights covers: in situ sealing for contaminated sites; and remote sensors for toxic pollutants. Section on profiles of countries includes: Arctic contamination by the former Soviet Union, and EM activities with Germany--cooperative arrangements.

  4. Mitochondrial cytochrome <em>B> sequence divergence among Spanish, Alpine and Abruzzo chamois (genus <em>Rupicapra>

    Directory of Open Access Journals (Sweden)

    Nadia Mucci

    1998-12-01

    Full Text Available Abstract We have studied genetic divergence and phylogenetic relationships of Alpine, Spanish and Abruzzo chamois (genus <em>Rupicapra> by sequencing a region of 330 nucleotides within the mitochondrial DNA cytochrome <em>b> gene (mtDNA cyt <em>b>. These sequences were aligned with additional homologous sequences of Caprinae: Japanese serow, Chinese goral, Canadian mountain goat, Mishmi takin, muskox, Sardinian mouflon and domestic goat. Results suggest that, using representatives of the Bovini as outgroups, the Caprinae constitute a monophyletic clade. However, inferred phylogenetic relationships among and within tribes of Caprinae were poorly defined and did not reflect current evolutionary and taxonomical views. In fact, the Asian Rupicaprini goral and serow constituted a strongly supported clade, which included the muskox, while the takin grouped with <em>Ovis>. Therefore, the monophyly of Ovibovini was not supported by cyt <em>b> sequences. Species of <em>Rupicapra> joined a strongly supported monophyletic clade, which was distantly related to the Asian rupicaprins and <em>Oreamnos>. Therefore, the monophyly of the Rupicaprini was not supported by these cyt <em>b> sequences. There were sister species relationships within <em>Rupicapra>, Spanish and Alpine chamois and the Abruzzo chamois (<em>Rupicapra pyrenaica ornataem> was strictly related to the Spanish chamois (<em>Rupicapra pyrenaica parvaem>, as previously suggested by allozyme data and biogeographic reconstructions.

  5. New Trifluoromethyl Triazolopyrimidines as Anti-<em>Plasmodium> <em>falciparum> Agents

    Directory of Open Access Journals (Sweden)

    Núbia Boechat

    2012-07-01

    Full Text Available According to the World Health Organization, half of the World’s population, approximately 3.3 billion people, is at risk for developing malaria. Nearly 700,000 deaths each year are associated with the disease. Control of the disease in humans still relies on chemotherapy. Drug resistance is a limiting factor, and the search for new drugs is important. We have designed and synthesized new 2-(trifluoromethyl[1,2,4]triazolo[1,5-<em>a>]pyrimidine derivatives based on bioisosteric replacement of functional groups on the anti-malarial compounds mefloquine and amodiaquine. This approach enabled us to investigate the impact of: (i ring bioisosteric replacement; (ii a CF3 group substituted at the 2-position of the [1,2,4]triazolo[1,5-<em>a>]pyrimidine scaffold and (iii a range of amines as substituents at the 7-position of the of heterocyclic ring; on <em>in vitroem> activity against <em>Plasmodium falciparumem>. According to docking simulations, the synthesized compounds are able to interact with <em>P. falciparumem> dihydroorotate dehydrogenase (<em>Pf>DHODH through strong hydrogen bonds. The presence of a trifluoromethyl group at the 2-position of the [1,2,4]triazolo[1,5-<em>a>]pyrimidine ring led to increased drug activity. Thirteen compounds were found to be active, with IC50 values ranging from 0.023 to 20 µM in the anti-HRP2 and hypoxanthine assays. The selectivity index (SI of the most active derivatives 5, 8, 11 and 16 was found to vary from 1,003 to 18,478.

  6. Evidence of lactim-lactam photo-tautomerization through four-member intramolecular hydrogen bonded network in 5-(4-fluorophenyl)-2-hydroxy-nicotinonitrile

    International Nuclear Information System (INIS)

    Samanta, Anuva; Guchhait, Nikhil

    2014-01-01

    Lactim-lactam isomerisation behavior through proton transfer process at the strained four-member intramolecular H-bonded ring in 5-(4-fluorophenyl)-2-hydroxy-nicotinonitrile (FP2HN) has been elaborately investigated by steady state absorption and emission, time-resolved fluorescence spectroscopy and quantum chemical calculations by the Density Functional Theory (DFT) method. Irrespective of the nature of the solvents, FP2HN exists as lactim (FP2HN) and lactam form (FP3PN) in the ground state. The observed large Stokes shifted emission band corresponds to the spectroscopic signature of lactim→lactam conversion by excited state intramolecular proton transfer (ESIPT) reaction across the four member H-bonded network. The ESIPT reaction is found to be suppressed in the basic medium due to the formation of anionic species. The effect of increase of temperature on the spectral behavior and hence the calculated thermodynamic parameters (K tau 0 , ΔG 0 , ΔH 0 , ΔS 0 ) indicate spontaneous lactim→lactam isomerisation process. The spectral behavior of the studied molecule has been compared with its parent molecule, 2-hydroxypyridine (2HP) and 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP). Structural calculations and potential energy curves along the proton transfer coordinate by the DFT method have been successfully employed to correlate the experimental findings. - Highlights: • Lactim lactam photo-isomerisation across four-member intramolecular hydrogen bond. • ESIPT reaction in 5-(4-fluorophenyl)-2-hydroxy-nicotinonitrile. • Steady state and time resolved spectroscopy. • Suppression of ESIPT in the basic medium. • Experimental spectral findings corroborate well DFT calculation results

  7. Genotoxicity of <em>Euphorbia hirtaem>: An <em>Allium cepaem> Assay

    Directory of Open Access Journals (Sweden)

    Kwan Yuet Ping

    2012-06-01

    Full Text Available The potential genotoxic effects of methanolic extracts of <em>Euphorbia hirta em>which is commonly used in traditional medicine to treat a variety of diseased conditions including asthma, coughs, diarrhea and dysentery was investigated using <em>Allium cepaem> assay. The extracts of 125, 250, 500 and 1,000 µg/mL were tested on root meristems of <em>A. cepaem>. Ethylmethanesulfonate was used as positive control and distilled water was used as negative control. The result showed that mitotic index decreased as the concentrations of <em>E. hirtaem> extract increased. A dose-dependent increase of chromosome aberrations was also observed. Abnormalities scored were stickiness, c-mitosis, bridges and vagrant chromosomes. Micronucleated cells were also observed at interphase. Result of this study confirmed that the methanol extracts of <em>E. hirta em>exerted significant genotoxic and mitodepressive effects at 1,000 µg/mL.

  8. Synthesis of strigolactones analogues by intramolecular [2+2] cycloaddition of ketene-iminium salts to olefins and their activity on Orobanche cumana seeds.

    Science.gov (United States)

    Lachia, Mathilde; Wolf, Hanno Christian; De Mesmaeker, Alain

    2014-05-01

    Strigolactones have been the latest identified phytohormones. Among the strigolactones analogues described recently, GR-24 remains the most studied derivative which is used as standard in this field. In order to improve several properties of GR-24 for potential agronomical applications, we investigated the effect of substituents on the B and C-rings on the activity for seed germination induction. We report here the synthesis of 9 GR-24 analogues via a [2+2] intramolecular cycloaddition of ketene-iminium salts and a summary of their activity for the germination of Orobanche cumana (broomrape) seeds. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. BINDING OF THE RESPIRATORY CHAIN INHIBITOR ANTIMYCIN TO THE MITOCHONDRIAL bc1 COMPLEX: A NEW CRYSTAL STRUCTURE REVEALS AN ALTERED INTRAMOLECULAR HYDROGEN-BONDING PATTERN.

    OpenAIRE

    Huang, Li-shar; Cobessi, David; Tung, Eric Y.; Berry, Edward A.

    2005-01-01

    Antimycin A (antimycin), one of the first known and most potent inhibitors of the mitochondrial respiratory chain, binds to the quinone reduction site of the cytochrome bc1 complex. Structure-activity-relationship studies have shown that the N-formylamino-salicyl-amide group is responsible for most of the binding specificity, and suggested that a low pKa for the phenolic OH group and an intramolecular H-bond between that OH and the carbonyl O of the salicylamide linkage are important. Tw...

  10. Experimental Evidence for Heavy-Atom Tunneling in the Ring-Opening of Cyclopropylcarbinyl Radical from Intramolecular 12C/13C Kinetic Isotope Effects

    Science.gov (United States)

    Gonzalez-James, Ollie M.; Zhang, Xue; Datta, Ayan; Hrovat, David A.; Borden, Weston Thatcher; Singleton, Daniel A.

    2010-01-01

    The intramolecular 13C kinetic isotope effects for the ring-opening of cyclopropylcarbinyl radical were determined over a broad temperature range. The observed isotope effects are unprecedentedly large, ranging from 1.062 at 80 °C to 1.163 at −100 °C. Semi-classical calculations employing canonical variational transition state theory drastically underpredict the observed isotope effects, but the predicted isotope effects including tunneling by a small-curvature tunneling model match well with experiment. These results and a curvature in the Arrhenius plot of the isotope effects support the recently predicted importance of heavy-atom tunneling in cyclopropylcarbinyl ring-opening. PMID:20722415

  11. Intramolecular Nicholas reactions in the synthesis of dibenzocycloheptanes. Synthesis of allocolchicine NSC 51046 and analogues and the formal synthesis of (-)-allocolchicine.

    Science.gov (United States)

    Djurdjevic, Sinisa; Yang, Fei; Green, James R

    2010-12-03

    The preparation of dibenzocycloheptyne-Co(2)(CO)(6) complexes by intramolecular Nicholas reactions of biaryl-2-propargyl alcohol-Co(2)(CO)(6) derivatives is described. Reductive decomplexation of the dibenzocycloheptyne-Co(2)(CO)(6) complexes affords the corresponding dibenzocycloheptenes, individual members of which have been employed in a formal total synthesis of (-)-allocolchicine, the preparation of 6,7-dihydro-3,4,9,10,11-pentamethoxy-5H-dibenzo[a,c]cyclohepten-5-one, and the enantioselective total syntheses of NSC 51046 and its 3,8,9,10-tetramethoxy regioisomer.

  12. Mild one-pot Horner-Wadsworth-Emmons olefination and intramolecular N-arylation for the syntheses of indoles, all regio-isomeric azaindoles, and thienopyrroles.

    Science.gov (United States)

    Choi, Ji Hye; Lim, Hwan Jung

    2015-05-14

    The syntheses of various N-protected aromatic-ring fused pyrrole-2-carboxylate derivatives have been accomplished using mild one-pot Horner-Wadsworth-Emmons olefination and Cu-catalyzed intramolecular N-arylation reactions. The optimized mild one-pot reaction conditions of various 2-bromo arylcarboxaldehydes with commercially available N-protected phosphonoglycine trimethylesters gave the desired aromatic-ring fused pyrrole-2-carboxylates, such as substituted indole-, all regio-isomeric azaindole-, and thienopyrrole-2-carboxylates, in good to excellent yields. These conditions showed broad substrate compatibility, without the loss of the protecting group.

  13. Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

    Directory of Open Access Journals (Sweden)

    Hideto Ito

    2011-07-01

    Full Text Available The gold-catalyzed, seven-membered ring forming, intramolecular hydroamination of alkynic sulfonamides has been investigated. The protocol, with a semihollow-shaped triethynylphosphine as a ligand for gold, allowed the synthesis of a variety of azepine derivatives, which are difficult to access by other methods. Both alkynic sulfoamides with a flexible linear chain and the benzene-fused substrates underwent 7-exo-dig cyclization to afford the nitrogen-containing heterocyclic seven-membered rings, such as tetrahydroazepine and dihydrobenzazepine, in good yields.

  14. Hg/Pt-catalyzed conversion of bromo alkynamines/alkynols to saturated and unsaturated γ-butyrolactams/lactones via intramolecular electrophilic cyclization.

    Science.gov (United States)

    Kiran Kumar, Yalla; Ranjith Kumar, Gadi; Sridhar Reddy, Maddi

    2016-01-28

    Convenient and general Hg(ii)/Pt(iv) catalyzed syntheses of γ-butyrolactams and α,β-unsaturated γ-butyrolactones/lactams are described via intramolecular electrophilic cyclizations of bromoalkynes with tosylamino and hydroxyl tethers. The reaction features the use of wet solvents, the exclusion of any base and additive, mild conditions and practical yields. We also synthesised few chiral lactams through this pathway. Additionally, it is shown that the NHTs group distanced further from the homopropargylic position assists regioselective bromoalkyne hydration to yield useful α-bromoketones. Furthermore, Boc protected bromo homo propargyl amines undergo 6-endo-dig cyclization through Boc oxygen to give bromomethylene substituted oxazinones.

  15. The origin of enantioselectivity in the l-threonine-derived phosphine-sulfonamide catalyzed aza-Morita-Baylis-Hillman reaction: Effects of the intramolecular hydrogen bonding

    KAUST Repository

    Lee, Richmond

    2013-01-01

    l-Threonine-derived phosphine-sulfonamide 4 was identified as the most efficient catalyst to promote enantioselective aza-Morita-Baylis-Hillman (MBH) reactions, affording the desired aza-MBH adducts with excellent enantioselectivities. Density functional theory (DFT) studies were carried out to elucidate the origin of the observed enantioselectivity. The importance of the intramolecular N-H⋯O hydrogen-bonding interaction between the sulfonamide and enolate groups was identified to be crucial in inducing a high degree of stereochemical control in both the enolate addition to imine and the subsequent proton transfer step, affording aza-MBH reactions with excellent enantioselectivity. © 2013 The Royal Society of Chemistry.

  16. New organoselenium compounds with intramolecular Se⋯O/ Se⋯H interactions: NMR and theoretical studies

    Science.gov (United States)

    Fragoso, Erick; Azpiroz, Ramón; Sharma, Pankaj; Espinosa-Pérez, Georgina; Lara-Ochoa, Francisco; Toscano, Alfredo; Gutierrez, Rene; Portillo, Oscar

    2018-03-01

    New 1,3-bis(phenylselanylmethyl)benzene (1, 2 and 4) and butyl phenylselane derivatives (3 and 5) are synthesized and full heteronuclear NMR characterization of these compounds are reported. Interestingly, NMR spectrum of compounds 2-5 show coupling of 1H and 13C signals of groups involved in intramolecular nonbonding interactions with 77Se. The coupling constants JH-Se and JC-Se are in the range 13.6-21.6 Hz and 28-49 Hz, respectively. For compounds 4 and 5, JH-Se coupling constants of formyl proton are smaller than their respective acetal sbnd CH protons for compounds 2 and 3. However, this trend is opposite for JC-Se coupling constants, indicating that in formyl group containing compounds 4 and 5, Se⋯O interactions are present while in compounds 2 and 3 with acetal fragments, Se⋯H interactions also could be present because of steric constraints. To confirm these interactions, quantum chemical analyses were performed for 2, 4 and 5. The minimal energy conformation for these compounds present Se⋯O/Se⋯H interactions and are at lower energy in comparison to different conformers which do not show any interaction. For compounds 4 and 5, minimal energy conformation present Se⋯O interactions and for compound 2, Se⋯H is the favored conformation. These results are in accordance with the NMR data for these compounds. X-ray crystal structure of compound 1,3-bis(phenylselanylmethyl)benzene (1) was also determined during this work. In order to understand the effect of the Se⋯O/Se⋯H interactions and the position of phenylselanylmethyl groups, quantum chemical analyses were also carried out for 1,4-bis(phenylselanylmethyl)benzene derivatives (6 and 7). Interestingly, minimal energy conformers of 1,3-bis(phenylselanylmethyl)benzene derivatives 2 and 4 are more stable than their corresponding conformers of 1,4-bis-(phenylselanylmethyl)benzene derivatives 6 and 7.1,3-bis[{(2-(diethoxymethyl)phenyl)selanyl}methyl]benzene (2) with an

  17. The roles of polycarboxylates in Cr(VI)/sulfite reaction system: Involvement of reactive oxygen species and intramolecular electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Bo, E-mail: bjiang86upc@163.com [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033 (China); Wang, Xianli; Liu, Yukun [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); Wang, Zhaohui [College of Environmental Science and Engineering, Donghua University, Shanghai 201620 (China); Southern Cross GeoScience, Southern Cross University, Lismore, NSW 2480 (Australia); Zheng, Jingtang, E-mail: jtzheng03@163.com [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China); Wu, Mingbo, E-mail: wumb@upc.edu.cn [State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, Shandong (China)

    2016-03-05

    Highlights: • The formations of SO{sub 4}·{sup −} and OH·, involve in Cr(VI) reduction induced by S(IV). • Affinity of polycarboxylate to Cr(VI) accelerates Cr(VI) reduction rate. • Polycarboxylates can act as electron donors for Cr(VI) reduction retrenching S(IV). • Only oxalate can enhance the formations of SO{sub 4}·{sup −} and OH· in Cr(VI)/S(IV) system. - Abstract: In this study, the effects of polycarboxylates on both Cr(VI) reduction and S(IV) consumption in Cr(VI)/S(IV) system was investigated in acidic solution. Under aerobic condition, the productions of reactive oxygen species (ROS), i.e., SO{sub 4}·{sup −} and OH·, have been confirmed in S(IV) reducing Cr(VI) process by using electron spin resonance and fluorescence spectrum techniques, leading to the excess consumption of S(IV). However, when polycarboxylates (oxalic, citric, malic and tartaric acid) were present in Cr(VI)/S(IV) system, the affinity of polycarboxylates to CrSO{sub 6}{sup 2−} can greatly promote the reduction of Cr(VI) via expanding the coordination of Cr(VI) species from tetrahedron to hexahedron. Besides, as alternatives to S(IV), these polycarboxylates can also act as electron donors for Cr(VI) reduction via intramolecular electron transfer reaction, which is dependent on the energies of the highest occupied molecular orbital of these polycarboxylates. Notably, the variant electron donating capacity of these polycarboxylates resulted in different yield of ROS and therefore the oxidation efficiencies of other pollutants, e.g., rhodamine B and As(III). Generally, this study does not only shed light on the mechanism of S(IV) reducing Cr(VI) process mediated by polycarboxylates, but also provides an escalated, cost-effective and green strategy for the remediation of Cr(VI) using sulfite as a reductant.

  18. Intramolecular hydrogen bonding

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Winther, Morten; Spanget-Larsen, Jens

    2006-01-01

    The vibrational structure of the title compound (DBM) was investigated by FTIR spectroscopy in liquid solutions, by FTIR linear dichroism (LD) measurements, and by Raman spectroscopy. The results were supported by the application of theoretical model calculations and analyzed with particular atte...

  19. Binding of the Respiratory Chain Inhibitor Antimycin to theMitochondrial bc1 Complex: A New Crystal Structure Reveals an AlteredIntramolecular Hydrogen-Bonding Pattern

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Li-shar; Cobessi, David; Tung, Eric Y.; Berry, Edward A.

    2005-05-10

    Antimycin A (antimycin), one of the first known and most potent inhibitors of the mitochondrial respiratory chain, binds to the quinone reduction site of the cytochrome bc1 complex.Structure-activity-relationship studies have shown that the N-formylamino-salicyl-amide group is responsible for most of the binding specificity, and suggested that a low pKa for the phenolic OH group and an intramolecular H-bond between that OH and the carbonyl O of the salicylamide linkage are important. Two previous X-ray structures of antimycin bound to vertebrate bc1 complex gave conflicting results. A new structure reported here of the bovine mitochondrial bc1 complex at 2.28Angstrom resolution with antimycin bound, allows us for the first time to reliably describe the binding of antimycin and shows that the intramolecular hydrogen bond described in solution and in the small-molecule structure is replaced by one involving the NH rather than carbonyl O of the amide linkage, with rotation of the amide group relative to the aromatic ring. The phenolic OH and formylamino N form H-bonds with conserved Asp228 of cyt b, and the formylamino O H-bonds via a water molecule to Lys227. A strong density the right size and shape for a diatomic molecule is found between the other side of the dilactone ring and the alpha-A helix.

  20. Binding of the respiratory chain inhibitor antimycin to the mitochondrial bc1 complex: a new crystal structure reveals an altered intramolecular hydrogen-bonding pattern.

    Science.gov (United States)

    Huang, Li-Shar; Cobessi, David; Tung, Eric Y; Berry, Edward A

    2005-08-19

    Antimycin A (antimycin), one of the first known and most potent inhibitors of the mitochondrial respiratory chain, binds to the quinone reduction site of the cytochrome bc1 complex. Structure-activity relationship studies have shown that the N-formylamino-salicyl-amide group is responsible for most of the binding specificity, and suggested that a low pKa for the phenolic OH group and an intramolecular H-bond between that OH and the carbonyl O of the salicylamide linkage are important. Two previous X-ray structures of antimycin bound to vertebrate bc1 complex gave conflicting results. A new structure reported here of the bovine mitochondrial bc1 complex at 2.28 A resolution with antimycin bound, allows us for the first time to reliably describe the binding of antimycin and shows that the intramolecular hydrogen bond described in solution and in the small-molecule structure is replaced by one involving the NH rather than carbonyl O of the amide linkage, with rotation of the amide group relative to the aromatic ring. The phenolic OH and formylamino N form H-bonds with conserved Asp228 of cytochrome b, and the formylamino O H-bonds via a water molecule to Lys227. A strong density, the right size and shape for a diatomic molecule is found between the other side of the dilactone ring and the alphaA helix.

  1. Double Intramolecular Transacetalization of Polyhydroxy Acetals: Synthesis of Conformationally-Restricted 1,3-Dioxanes with Axially-Oriented Phenyl Moiety

    Directory of Open Access Journals (Sweden)

    Samuel Asare-Nkansah

    2016-11-01

    Full Text Available The synthesis of conformationally-restricted 1,3-dioxanes with a phenyl moiety fixed in an axial orientation at the acetalic center is described. Starting with diethyl 3-hydroxyglutarate (15, benzaldehyde acetal 12a and acetophenone ketal 12b bearing a protected 1,3,5-trihydroxypentyl side chain in the o-position were prepared. The first acid-catalyzed intramolecular transacetalization gave a mixture of diastereomeric 2-benzofurans 18 (ratio of diastereomers 2:2:1:1. After OH group deprotection, the second intramolecular transacetalization afforded tricyclic alcohol 14a (2-(1,5-epoxy-1,3,4,5-tetrahydro-2-benzoxepin-3-yl]ethan-1-ol. Analogous cyclizations led to the corresponding silyl ether 22a (19% and azide 23a (13%. Whereas tricyclic alcohol 14a was obtained as a 1:1 mixture of diastereomers, the silyl ether 22a and the azide 23a afforded only one diastereomer. This observation indicates a faster cyclization of the minor diastereomers providing the thermodynamically-favored compounds with equatorially-oriented substituents in the 3-position of the tricyclic 1,5-epoxy-2-benzoxepine system. In general, acetophenone-derived ketalic compounds (b-series required very mild reaction conditions and gave lower yields than the corresponding acetalic compounds (a-series.

  2. Synthesis, spectral behaviour and photophysics of donor-acceptor kind of chalcones: Excited state intramolecular charge transfer and fluorescence quenching studies

    Science.gov (United States)

    Pannipara, Mehboobali; Asiri, Abdullah M.; Alamry, Khalid A.; Arshad, Muhammad N.; El-Daly, Samy A.

    2015-02-01

    The spectral and photophysical properties of two chalcones containing electron donating and accepting groups with intramolecular charge transfer characteristics were synthesized and characterized by 1H NMR, 13C NMR and X-ray crystallography. Both compounds show very strong solvent polarity dependent changes in their photophysical characteristics, namely, remarkable red shift in the emission spectra with increasing solvent polarity, large change in Stokes shift, significant reduction in the fluorescence quantum yield; indicating that the fluorescence states of these compounds are of intramolecular charge transfer (ICT) character. The solvent effect on the photophysical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment, fluorescence spectra, and fluorescence quantum yield of both compounds have been investigated comprehensively. For both dyes, Lippert-Mataga and Reichardt's correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). The interactions of dyes with colloidal silver nanoparticles (Ag NPs) were also studied in ethanol using steady state fluorescence quenching measurements. The fluorescence quenching data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching of dyes by Ag NPs.

  3. Twisted intramolecular charge transfer investigation of semi organic L-Glutamic acid hydrochloride single crystal for organic light-emitting and optical limiting applications

    Science.gov (United States)

    Joy, Lija K.; George, Merin; Alex, Javeesh; Aravind, Arun; Sajan, D.; Vinitha, G.

    2018-03-01

    Single crystals of L-Glutamic acid hydrochloride (LGHCl) were grown by slow evaporation solution technique and good crystalline perfection was confirmed by Powder X-ray diffraction studies. The complete vibrational studies of the compound were analyzed by FT-IR, FT-Raman and UV-visible spectra combined with Normal Coordinate Analysis (NCA) following the scaled quantum mechanical force field methodology and density functional theory (DFT). Twisted Intramolecular Charge Transfer (ICT) occurs due to the presence of strong ionic intra-molecular Nsbnd H⋯O hydrogen bonding was confirmed by Hirshfeld Surface analysis. The existence of intermolecular Nsbnd H⋯Cl hydrogen bonds due to the interaction between the lone pair of oxygen with the antibonding orbital was established by NBO analysis. The Z-scan result indicated that the title molecule exhibits saturable absorption behavior. The attractive third-order nonlinear properties suggest that LGHCl can be a promising candidate for the design and development devices for optical limiting applications. LGHCL exhibits distinct emission in the blue region of the fluorescence lifetime which proves to be a potential candidate for blue- Organic light-emitting diodes (OLEDs) fabrication.

  4. Strategies to enhance the excitation energy-transfer efficiency in a light-harvesting system using the intra-molecular charge transfer character of carotenoids

    Energy Technology Data Exchange (ETDEWEB)

    Yukihira, Nao [Department of Applied Chemistry for Environment; School of Science and Technology; Kwansei Gakuin University; Sanda; Japan; Sugai, Yuko [Department of Applied Chemistry for Environment; School of Science and Technology; Kwansei Gakuin University; Sanda; Japan; Fujiwara, Masazumi [Department of Applied Chemistry for Environment; School of Science and Technology; Kwansei Gakuin University; Sanda; Japan; Kosumi, Daisuke [Institute of Pulsed Power Science; Kumamoto University; Kumamoto; Japan; Iha, Masahiko [South Product Co. Ltd.; Uruma-shi; Japan; Sakaguchi, Kazuhiko [Department of Chemistry; Graduate School of Science; Osaka City University; Osaka 558-8585; Japan; Katsumura, Shigeo [Department of Chemistry; Graduate School of Science; Osaka City University; Osaka 558-8585; Japan; Gardiner, Alastair T. [Glasgow Biomedical Research Centre; University of Glasgow; 126 University Place; Glasgow, G12 8QQ; UK; Cogdell, Richard J. [Glasgow Biomedical Research Centre; University of Glasgow; 126 University Place; Glasgow, G12 8QQ; UK; Hashimoto, Hideki [Department of Applied Chemistry for Environment; School of Science and Technology; Kwansei Gakuin University; Sanda; Japan

    2017-01-01

    Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (~95%) energy-transfer from fucoxanthin to chlorophyllain the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium,Rhodospirillum rubrumG9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to bacteriochlorophyllawhen they are bound to the light-harvesting 1 apo-proteins.

  5. Modulation of dual fluorescence in a 3-hydroxyquinolone dye by perturbation of its intramolecular proton transfer with solvent polarity and basicity.

    Science.gov (United States)

    Yushchenko, Dmytro A; Shvadchak, Volodymyr V; Bilokin', Mykhailo D; Klymchenko, Andrey S; Duportail, Guy; Mély, Yves; Pivovarenko, Vasyl G

    2006-11-01

    A representative of a new class of dyes with dual fluorescence due to an excited state intramolecular proton transfer (ESIPT) reaction, namely 1-methyl-2-(4-methoxy)phenyl-3-hydroxy-4(1H)-quinolone (QMOM), has been studied in a series of solvents covering a large range of polarity and basicity. A linear dependence of the logarithm of its two bands intensity ratio, log(I(N*)/I(T*)), upon the solvent polarity expressed as a function of the dielectric constant, (epsilon- 1)/(2epsilon + 1), is observed for a series of protic solvents. A linear dependence for log(I(N*)/I(T*)) is also found in aprotic solvents after taking into account the solvent basicity. In contrast, the positions of the absorption and the two emission bands of QMOM do not noticeably depend on the solvent polarity and basicity, indicating relatively small changes in the transition moment of QMOM upon excitation and emission. Time-resolved experiments in acetonitrile, ethyl acetate and dimethylformamide suggest an irreversible ESIPT reaction for this dye. According to the time-resolved data, an increase of solvent basicity results in a dramatic decrease of the ESIPT rate constant, probably due to the disruption of the intramolecular H-bond of the dye by the basic solvent. Due to this new sensor property, 3-hydroxyquinolones are promising candidates for the development of a new generation of environment-sensitive fluorescence dyes for probing interactions of biomolecules.

  6. Emergency Medical Service (EMS) Stations

    Data.gov (United States)

    Kansas Data Access and Support Center — EMS Locations in Kansas The EMS stations dataset consists of any location where emergency medical services (EMS) personnel are stationed or based out of, or where...

  7. Ultrafast intramolecular charge transfer with N-(4-cyanophenyl)carbazole. Evidence for a LE precursor and dual LE + ICT fluorescence.

    Science.gov (United States)

    Galievsky, Victor A; Druzhinin, Sergey I; Demeter, Attila; Mayer, Peter; Kovalenko, Sergey A; Senyushkina, Tamara A; Zachariasse, Klaas A

    2010-12-09

    The photophysics of N-(4-cyanophenyl)carbazole (NP4CN) was investigated by using absorption and fluorescence spectra, picosecond fluorescence decays, and femtosecond transient absorption. In the nonpolar n-hexane as well as in the polar solvent acetonitrile (MeCN), a locally excited (LE) state is detected, as a precursor for the intramolecular charge transfer (ICT) state. A LE → ICT reaction time τ(2) at 22 °C of 0.95 ps in ethyl cyanide (EtCN) and 0.32 ps in MeCN is determined from the decay of the LE excited state absorption (ESA) maximum around 620 nm. In the ESA spectrum of NP4CN in n-hexane at a pump-probe delay time of 100 ps, an important contribution of the LE band remains alongside the ICT band, in contrast to what is observed in EtCN and MeCN. This shows that a LE ⇄ ICT equilibrium is established in this solvent and the ICT reaction time of 0.5 ps is equal to the reciprocal of the sum of the forward and backward ICT rate constants 1/(k(a) + k(d)). In the photostationary S(0) → S(n) absorption spectrum of NP4CN in n-hexane and MeCN, an additional CT absorption band appears, absent in the sum of the spectra of its electron donor (D) and acceptor (A) subgroups carbazole and benzonitrile. This CT band is located at an energy of ∼4000 cm(-1) lower than for N-phenylcarbazole (NPC), due to the larger electron affinity of the benzonitrile moiety of NP4CN than the phenyl subunit of NPC. The fluorescence spectrum of NP4CN in n-hexane at 25 °C mainly consists of a structured LE emission, with a small ICT admixture, indicating that a LE → ICT reaction just starts to occur under these conditions. In di-n-pentyl ether (DPeE) and di-n-butyl ether (DBE), a LE emission is found upon cooling at the high-energy edge of the ICT fluorescence band, caused by the onset of dielectric solvent relaxation. This is not the case in more polar solvents, such as diethyl ether (DEE) and MeCN, in which a structureless ICT emission band fully overlaps the strongly quenched LE

  8. <em>Angiostrongylus vasorumem> in red foxes (<em>Vulpes vulpesem> and badgers (<em>Meles melesem> from Central and Northern Italy

    Directory of Open Access Journals (Sweden)

    Marta Magi

    2010-06-01

    Full Text Available Abstract During 2004-2005 and 2007-2008, 189 foxes (<em>Vulpes vulpesem> and 6 badgers (<em>Meles melesem> were collected in different areas of Central Northern Italy (Piedmont, Liguria and Tuscany and examined for <em>Angiostrongylus vasorumem> infection. The prevalence of the infection was significantly different in the areas considered, with the highest values in the district of Imperia (80%, Liguria and in Montezemolo (70%, southern Piedmont; the prevalence in Tuscany was 7%. One badger collected in the area of Imperia turned out to be infected, representing the first report of the parasite in this species in Italy. Further studies are needed to evaluate the role played by fox populations as reservoirs of infection and the probability of its spreading to domestic dogs.
    Riassunto <em>Angiostrongylus vasorumem> nella volpe (<em>Vulpes vulpesem> e nel tasso (<em>Meles melesem> in Italia centro-settentrionale. Nel 2004-2005 e 2007-2008, 189 volpi (<em>Vulpes vulpesem> e 6 tassi (<em>Meles melesem> provenienti da differenti aree dell'Italia settentrionale e centrale (Piemonte, Liguria Toscana, sono stati esaminati per la ricerca di <em>Angiostrongylus vasorumem>. La prevalenza del nematode è risultata significativamente diversa nelle varie zone, con valori elevati nelle zone di Imperia (80% e di Montezemolo (70%, provincia di Cuneo; la prevalenza in Toscana è risultata del 7%. Un tasso proveniente dall'area di Imperia è risultato positivo per A. vasorum; questa è la prima segnalazione del parassita in tale specie in Italia. Ulteriori studi sono necessari per valutare il potenziale della volpe come serbatoio e la possibilità di diffusione della parassitosi ai cani domestici.

    doi:10.4404/hystrix-20.2-4442

  9. International EMS Systems

    DEFF Research Database (Denmark)

    Langhelle, Audun; Lossius, Hans Morten; Silfvast, Tom

    2004-01-01

    Emergency medicine service (EMS) systems in the five Nordic countries have more similarities than differences. One similarity is the involvement of anaesthesiologists as pre-hospital physicians and their strong participation for all critically ill and injured patients in-hospital. Discrepancies do...... exist, however, especially within the ground and air ambulance service, and the EMS systems face several challenges. Main problems and challenges emphasized by the authors are: (1) Denmark: the dispatch centres are presently not under medical control and are without a national criteria based system...... is the only country that has emergency medicine (EM) as a recognised speciality but there is a need for more fully trained specialists in EM; (4) Norway: the ordinary ground ambulance is pointed out as the weakest link in the EM chain and a health reform demands extensive co-operation between the new health...

  10. O ator em jogo

    OpenAIRE

    Daves Otani

    2005-01-01

    Resumo: O Ator em Jogo é uma reflexão pessoal sobre aspectos do processo criativo em dois espetáculos teatrais encenados pelo grupo Boa Companhia: PRIMUS (adaptado do conto "Comunicado a uma Academia", de Franz Kafka) e MISTER K. E OS ARTISTAS DA FOME (adaptado do conto "O artista da fome", de Kafka). Utilizando a experiência prática da capoeira, que serviu como matriz criativa nessas duas montagens, em cada uma a seu modo específico, faço uma reflexão a partir de um diário que relata experiê...

  11. International EMS Systems

    DEFF Research Database (Denmark)

    Langhelle, Audun; Lossius, Hans Morten; Silfvast, Tom

    2004-01-01

    exist, however, especially within the ground and air ambulance service, and the EMS systems face several challenges. Main problems and challenges emphasized by the authors are: (1) Denmark: the dispatch centres are presently not under medical control and are without a national criteria based system...... enterprises to re-establish a nation-wide air ambulance service; (5) Sweden: to create evidence based medicine standards for treatment in emergency medicine, a better integration of all part of the chain of survival, a formalised education in EM and a nation wide physician staffed helicopter EMS (HEMS) cover....

  12. International EMS Systems

    DEFF Research Database (Denmark)

    Langhelle, Audun; Lossius, Hans Morten; Silfvast, Tom

    2004-01-01

    . Access to on-line medical advice of a physician is not available; (2) Finland: the autonomy of the individual municipalities and their responsibility to cover for primary and specialised health care, as well as the EMS, and the lack of supporting or demanding legislation regarding the EMS; (3) Iceland...... exist, however, especially within the ground and air ambulance service, and the EMS systems face several challenges. Main problems and challenges emphasized by the authors are: (1) Denmark: the dispatch centres are presently not under medical control and are without a national criteria based system...

  13. Expression of Selected <em>Ginkgo em>>biloba em>Heat Shock Protein Genes After Cold Treatment Could Be Induced by Other Abiotic Stress

    Directory of Open Access Journals (Sweden)

    Feng Xu

    2012-05-01

    Full Text Available Heat shock proteins (HSPs play various stress-protective roles in plants. In this study, three <em>HSP> genes were isolated from a suppression subtractive hybridization (SSH cDNA library of <em>Ginkgo bilobaem> leaves treated with cold stress. Based on the molecular weight, the three genes were designated <em>GbHSP16.8em>, <em>GbHSP17em> and <em>GbHSP70em>. The full length of the three genes were predicted to encode three polypeptide chains containing 149 amino acids (Aa, 152 Aa, and 657 Aa, and their corresponding molecular weights were predicted as follows: 16.67 kDa, 17.39 kDa, and 71.81 kDa respectively. The three genes exhibited distinctive expression patterns in different organs or development stages. <em>GbHSP16.8em> and <em>GbHSP70em> showed high expression levels in leaves and a low level in gynoecia, <em>GbHSP17em> showed a higher transcription in stamens and lower level in fruit. This result indicates that <em>GbHSP16.8em> and <em>GbHSP70 em>may play important roles in <em>Ginkgo> leaf development and photosynthesis, and <em>GbHSP17em> may play a positive role in pollen maturation. All three <em>GbHSPs> were up-regulated under cold stress, whereas extreme heat stress only caused up-regulation of <em>GbHSP70em>, UV-B treatment resulted in up-regulation of <em>GbHSP16.8em> and <em>GbHSP17em>, wounding treatment resulted in up-regulation of <em>GbHSP16.8em> and <em>GbHSP70em>, and abscisic acid (ABA treatment caused up-regulation of <em>GbHSP70em> primarily.

  14. [Ru(IV)(F20-TPP)Cl2] efficiently catalysed inter- and intra-molecular nitrene insertion into sp3 C-H bonds of hydrocarbons using phosphoryl azides as nitrene sources.

    Science.gov (United States)

    Xiao, Wenbo; Wei, Jinhu; Zhou, Cong-Ying; Che, Chi-Ming

    2013-05-21

    [Ru(IV)(F20-TPP)Cl2][H2(F20-TPP) = meso-tetrakis(pentafluorophenyl)porphyrin] is an active catalyst for both inter- and intra-molecular nitrene insertion into sp(3) C-H bonds of hydrocarbons in good to high product yields using phosphoryl azides as nitrene sources.

  15. Pulse radiolysis studies of intramolecular electron transfer in model peptides and proteins. 7. Trp -> TyrO radical transformation in hen egg-white lysozyme. Effects of pH, temperature, Trp62 oxidation and inhibitor binding

    DEFF Research Database (Denmark)

    Bobrowski, K.; Holcman, J.; Poznanski, J.

    1997-01-01

    Intramolecular long-range electron transfer (LRET) in hen egg-white lysozyme (HEWL) accompanying Trp --> TyrO radical transformation was investigated in aqueous solution by pulse radiolysis as a function of pH (5.2-7.4) and temperature (283-328K). The reaction was induced by highly selective...

  16. Intramolecular stacking interactions in ternary copper(II) complexes formed by a heteroaromatic amine and 9-[2-(2-phosphonoethoxy)ethyl]adenine, a relative of the antiviral nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]adenine

    Czech Academy of Sciences Publication Activity Database

    Fernández-Botello, A.; Holý, Antonín; Moreno, V.; Sigel, H.

    2004-01-01

    Roč. 98, - (2004), s. 2114-2124 ISSN 0162-0134 R&D Projects: GA MŠk OC D20.002 Institutional research plan: CEZ:AV0Z4055905 Keywords : adenine nucleotide analogues * intramolecular equilibria * isomeric complexes Subject RIV: CC - Organic Chemistry Impact factor: 2.225, year: 2004

  17. Intramolecular .pi.-.pi. stacking interactions in aqueous solution in mixed-ligand copper (II) complexes formed by heteroaromatic amines and the nucleotide analogue (PME2AP), an isomer of the antivirally active (PMEA)

    Czech Academy of Sciences Publication Activity Database

    Fernández-Botello, A.; Holý, Antonín; Moreno, V.; Operschall, B. P.; Sigel, H.

    2009-01-01

    Roč. 362, č. 3 (2009), s. 799-810 ISSN 0020-1693 R&D Projects: GA MŠk 1M0508 Institutional research plan: CEZ:AV0Z40550506 Keywords : antiviral activity * intramolecular equilibria * isomeric complexes * phosphonate complexes Subject RIV: CC - Organic Chemistry Impact factor: 2.322, year: 2009

  18. Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.

    Science.gov (United States)

    Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

    2014-07-03

    A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are α to the piperidine nitrogen (α-C-H bonds). With 3 HAT from both the phenolic O-H and the α-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the α-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems.

  19. Synthesis of Structurally Diverse 2,3-Fused Indoles via Microwave-Assisted AgSbF6-Catalysed Intramolecular Difunctionalization of o-Alkynylanilines

    Science.gov (United States)

    Huang, Yuanqiong; Yang, Yan; Song, Hongjian; Liu, Yuxiu; Wang, Qingmin

    2015-08-01

    2,3-Fused indoles are found in numerous natural products and drug molecules. Although several elegant methods for the synthesis of this structural motif have been reported, long reaction times and harsh conditions are sometimes required, and the yields tend to be low. Herein, we report a microwave method for straightforward access to various types of 2,3-fused indoles via AgSbF6-catalysed intramolecular difunctionalization of o-alkynylanilines. AgSbF6 played a role in both the hydroamination step and the imine-formation step. This method, which exhibited excellent chemoselectivity (no ring-fused 1,2-dihydroquinolines were formed), was used for formal syntheses of the natural products conolidine and ervaticine and the antihistamine drug latrepirdine.

  20. Efficient Estimators for Quantum Instanton Evaluation of theKinetic Isotope Effects: Application to the Intramolecular HydrogenTransfer in Pentadiene

    Energy Technology Data Exchange (ETDEWEB)

    Vanicek, Jiri; Miller, William H.

    2007-06-13

    The quantum instanton approximation is used to compute kinetic isotope effects for intramolecular hydrogen transfer in cis-1,3-pentadiene. Due to the importance of skeleton motions, this system with 13 atoms is a simple prototype for hydrogen transfer in enzymatic reactions. The calculation is carried out using thermodynamic integration with respect to the mass of the isotopes and a path integral Monte Carlo evaluation of relevant thermodynamic quantities. Efficient 'virial' estimators are derived for the logarithmic derivatives of the partition function and the delta-delta correlation functions. These estimators require significantly fewer Monte Carlo samples since their statistical error does not increase with the number of discrete time slices in the path integral. The calculation treats all 39 degrees of freedom quantum-mechanically and uses an empirical valence bond potential based on a modified general AMBER force field.

  1. New Palladium-Catalyzed Domino Reaction with Intramolecular Ring Closure of an N-(2-Chloro-3-heteroaryl) arylamide: First Synthesis of Oxazolo[4,5-b] pyrazines

    DEFF Research Database (Denmark)

    Demmer, Charles S.; Hansen, Jacob C.; Kehler, Jan

    2014-01-01

    The synthesis of novel planar heterocycles is at the heart of basic research as such scaffolds constitute key building blocks in important diverse areas of research: drug discovery, material sciences, and pesticides. The well-known benzoxazole is often contained in drug candidates but tweaking its...... lipophilicity and target interaction points are often desired. In this respect, the oxazolo[4,5-b]pyrazine is an attractive heterocyclic scaffold as it possesses increased water solubility as well as two additional hydrogen bonding acceptors. We here report a new Pd(II)-catalyzed domino reaction comprising...... the first Pd(II)-assisted intramolecular cyclization of an N-(2-chloro-3-heteroaryl)arylamide and validate its value by application to the first synthesis of 2-substituted oxazolo[4,5-b]pyrazines. We demonstrate that a bidentate phosphorus ligand as well as the presence of an aromatic nitrogen atom...

  2. Effects of Molecular Structure on Intramolecular Charge Carrier Transport in Dithieno [3,2-b: 2,3-d] Pyrrole-Based Conjugated Copolymers

    Directory of Open Access Journals (Sweden)

    Yoshihito Honsho

    2012-01-01

    Full Text Available Intramolecular mobility of positive charge carriers in conjugated polymer films based on dithieno [2,3-b: 2,3-d] pyrrole (DTP is studied by time-resolved microwave conductivity (TRMC. A series of DTP homopolymer and copolymers combined with phenyl, 2,2-biphenyl, thiophene, 2,2-bithiophene, and 9,9-dioctylfluorene were synthesized by Suzuki-Miyaura and Yamamoto coupling reactions. Polymers containing DTP unit are reported to show high value of hole mobility measured by FET method, and this type of polymers is expected to have stable HOMO orbitals which are important for hole transportation. Among these copolymers, DTP coupled with 9,9-dioctylfluorene copolymer showed the highest charge carrier mobility as high as 1.7 cm2/Vs, demonstrating an excellent electrical property on rigid copolymer backbones.

  3. Intra-molecular mobility of charge carriers along oligogermane backbones studied by flash photolysis time-resolved microwave conductivity and transient optical spectroscopy techniques

    Energy Technology Data Exchange (ETDEWEB)

    Seki, Shu [Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)], E-mail: seki@chem.eng.osaka-u.ac.jp; Saeki, Akinori; Acharya, Anjali; Koizumi, Yoshiko; Tagawa, Seiichi [The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Mochida, Kunio [Department of Chemistry Faculty of Science, Gakusyuin University, 1-5-1 Mejiro, Tokyo 171-8588 (Japan)

    2008-10-15

    Time-resolved microwave conductivity (TRMC) measurement has been performed for fullerene-doped thin films of oligo (dimethylgermane) at different excitation energies to evaluate the intra-molecular mobility of holes along their Ge backbones. Photo-induced electron transfer reaction between oligogermane and fullerene has been observed in the solution with a variety of solvent polarity using transient optical spectroscopy (TOS). The transient spectrum at 391 nm can be attributed to the radical cation of the oligomer under an excitation at 532-nm light, whereas the same spectrum (391 nm) is the overlapping of absorptions of radical cations and neutral radicals of oligogermanes upon exposure of 355-nm light in polar solvent. A combined TRMC and TOS experiments on the solutions of oligomer confirms the conductive transients originate from the radical cations on the backbone chains.

  4. Morphological transition of the host-structure influences solvent-relaxation: A wavelength-selective fluorescence exploration through environment-sensitive intramolecular charge transfer photophysics

    Science.gov (United States)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2011-10-01

    Here, we report the modulation of photo-induced intramolecular charge transfer (ICT) photophysics of N,N-dimethylaminonaphthyl-acrylo-nitrile (DMANAN) associated with sphere-to-rod structural transition of SDS micelles induced by increasing ionic strength of the medium. Emphasis is rendered on the exploration of solvent-relaxation associated with this transition on the basis of wavelength-selective fluorescence technique which includes monitoring of red-edge excitation shift (REES) and excitation/emission anisotropy profiles. Based on micropolarity determination and organization of solvent water around the probe microenvironment we argue that the present results advocate for rod-shaped micelles to be a better mimic for membrane bilayers than spherical micelles.

  5. Gate voltage dependent characteristics of p-n diodes and bipolar transistors based on multiwall CN(x)/carbon nanotube intramolecular junctions.

    Science.gov (United States)

    Zhang, W J; Zhang, Q F; Chai, Y; Shen, X; Wu, J L

    2007-10-03

    The electrical transport characteristics of multiwall CN(x)/carbon nanotube intramolecular junctions were studied. The junctions could be used as diodes. We found that the rectification resulted from p-n junctions, not from metal-semiconductor junctions. The gate effect was very weak when the diodes were reverse biased. At forward bias, however, some of the p-n diodes could be n-type transistors. Experimental results supported the opinion that the gate voltage dependent property is derived from the Schottky barrier between the CN(x) part and the electrode. Using p-n diodes, a bipolar transistor with nanoscale components was built, whose behavior was very similar to that of a conventional planar bipolar transistor.

  6. Separation of the intramolecular isotope effect for the cytochrome P-450 catalyzed hydroxylation of n-octane into its primary and secondary components

    International Nuclear Information System (INIS)

    Jones, J.P.; Trager, W.F.

    1987-01-01

    The intramolecular isotope effect for the cytochrome P-450b omega-hydroxylation of [1,1,1- 2 H 3 ]-n-octane was separated into its primary and secondary components by the method of Hanzlik. The primary isotope effect was found to lie between 7.3 and 7.9 while the secondary isotope effect was found to lie between 1.09 and 1.14. These data are consistent with a highly symmetrical transition state with 15% of the observed isotope effect being due to secondary isotope effects. Although the system was found to depart from the rule of the geometric mean, the phenomenon could not be attributed to tunneling

  7. Synthesis of Bioactive 2-(Arylaminothiazolo[5,4-f]-quinazolin-9-ones via the Hügershoff Reaction or Cu- Catalyzed Intramolecular C-S Bond Formation

    Directory of Open Access Journals (Sweden)

    Damien Hédou

    2016-06-01

    Full Text Available A library of thirty eight novel thiazolo[5,4-f]quinazolin-9(8H-one derivatives (series 8, 10, 14 and 17 was prepared via the Hügershoff reaction and a Cu catalyzed intramolecular C-S bond formation, helped by microwave-assisted technology when required. The efficient multistep synthesis of the key 6-amino-3-cyclopropylquinazolin-4(3H-one (3 has been reinvestigated and performed on a multigram scale from the starting 5-nitroanthranilic acid. The inhibitory potency of the final products was evaluated against five kinases involved in Alzheimer’s disease and showed that some molecules of the 17 series described in this paper are particularly promising for the development of novel multi-target inhibitors of kinases.

  8. The dimers of glyoxal and acrolein with H 2O and HF: Negative intramolecular coupling and blue-shifted C-H stretch

    Science.gov (United States)

    Karpfen, Alfred; Kryachko, Eugene S.

    2010-04-01

    The structures and the vibrational spectra of the hydrogen-bonded complexes: glyoxal-H 2O, glyoxal-HF, acrolein-H 2O, and acrolein-HF, are investigated within the MP2/aug-cc-pVTZ computational approach. It is demonstrated that the calculated blue shifts of the C-H stretching frequencies in the glyoxal-H 2O complexes are only indirectly pertinent to hydrogen bonding to the C-H group. The comparison with the glyoxal-HF and the acrolein-HF complexes reveals that these blue shifts are a direct consequence of a negative intramolecular coupling between vicinal C dbnd O and C-H bonds in the aldehyde groups of isolated glyoxal and acrolein molecules. To support this interpretation, the halogen-bonded complexes glyoxal-BrF and acrolein-BrF are discussed.

  9. Intramolecular interaction influences binding of the Flax L5 and L6 resistance proteins to their AvrL567 ligands.

    Directory of Open Access Journals (Sweden)

    Michael Ravensdale

    Full Text Available L locus resistance (R proteins are nucleotide binding (NB-ARC leucine-rich repeat (LRR proteins from flax (Linum usitatissimum that provide race-specific resistance to the causal agent of flax rust disease, Melampsora lini. L5 and L6 are two alleles of the L locus that directly recognize variants of the fungal effector AvrL567. In this study, we have investigated the molecular details of this recognition by site-directed mutagenesis of AvrL567 and construction of chimeric L proteins. Single, double and triple mutations of polymorphic residues in a variety of AvrL567 variants showed additive effects on recognition strength, suggesting that multiple contact points are involved in recognition. Domain-swap experiments between L5 and L6 show that specificity differences are determined by their corresponding LRR regions. Most positively selected amino acid sites occur in the N- and C-terminal LRR units, and polymorphisms in the first seven and last four LRR units contribute to recognition specificity of L5 and L6 respectively. This further confirms that multiple, additive contact points occur between AvrL567 variants and either L5 or L6. However, we also observed that recognition of AvrL567 is affected by co-operative polymorphisms between both adjacent and distant domains of the R protein, including the TIR, ARC and LRR domains, implying that these residues are involved in intramolecular interactions to optimize detection of the pathogen and defense signal activation. We suggest a model where Avr ligand interaction directly competes with intramolecular interactions to cause activation of the R protein.

  10. Thorium and uranium redox-active ligand complexes; reversible intramolecular electron transfer in U(dpp-BIAN)2/ U(dpp-BIAN)2(THE)

    Energy Technology Data Exchange (ETDEWEB)

    Schelter, Eric John [Los Alamos National Laboratory; Wu, Ruilian [Los Alamos National Laboratory; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

    2008-01-01

    Actinide complexes of the redox-active ligand dpp-BIAN{sup 2-} (dpp-BIAN = bis(2,6-diisopropylphenyl)acenaphthylene), An(dpp-BIAN){sub 2}(THF){sub n} (An = Th, n = 1; An = U, n = 0, 1) have been prepared. Solid-state magnetic and single-crystal X-ray data for U(dpp-BIAN){sub 2}(THF){sub n} show when n = 0, the complex exists in an f{sup 2}-{pi}*{sup 4} configuration; whereas an intramolecular electron transfer occurs for n = 1, resulting in an f{sup 3}-{pi}*{sup 3} ground configuration. The magnetic data also indicate that interconversion between the two forms of the complex is possible, limited only by the ability of THF vapor to penetrate the solid on cooling of the sample. Spectroscopic data indicate the complex exists solely in the f{sup 2}-{pi}*{sup 4} form in solution, evidenced by the appearance of only small changes in the electronic absorption spectra of the U(dpp-BIAN){sub 2} complex on titration with THF and by measurement of the solution magnetic moment m d{sub 8}-tetrahydrofuran using Evans method. Electrochemistry of the complexes is reported, with small differences observed in wave potentials between metals and in the presence of THF. These data represent the first example of a well-defined, reversible intramolecular electron transfer in an f-element complex and the second example of oxidation state change through dative interaction with a metal ion.

  11. An Intramolecular Salt Bridge in Bacillus thuringiensis Cry4Ba Toxin Is Involved in the Stability of Helix α-3, Which Is Needed for Oligomerization and Insecticidal Activity.

    Science.gov (United States)

    Pacheco, Sabino; Gómez, Isabel; Sánchez, Jorge; García-Gómez, Blanca-Ines; Soberón, Mario; Bravo, Alejandra

    2017-10-15

    Bacillus thuringiensis three-domain Cry toxins kill insects by forming pores in the apical membrane of larval midgut cells. Oligomerization of the toxin is an important step for pore formation. Domain I helix α-3 participates in toxin oligomerization. Here we identify an intramolecular salt bridge within helix α-3 of Cry4Ba (D111-K115) that is conserved in many members of the family of three-domain Cry toxins. Single point mutations such as D111K or K115D resulted in proteins severely affected in toxicity. These mutants were also altered in oligomerization, and the mutant K115D was more sensitive to protease digestion. The double point mutant with reversed charges, D111K-K115D, recovered both oligomerization and toxicity, suggesting that this salt bridge is highly important for conservation of the structure of helix α-3 and necessary to promote the correct oligomerization of the toxin. IMPORTANCE Domain I has been shown to be involved in oligomerization through helix α-3 in different Cry toxins, and mutations affecting oligomerization also elicit changes in toxicity. The three-dimensional structure of the Cry4Ba toxin reveals an intramolecular salt bridge in helix α-3 of domain I. Mutations that disrupt this salt bridge resulted in changes in Cry4Ba oligomerization and toxicity, while a double point reciprocal mutation that restored the salt bridge resulted in recovery of toxin oligomerization and toxicity. These data highlight the role of oligomer formation as a key step in Cry4Ba toxicity. Copyright © 2017 American Society for Microbiology.

  12. Intramolecular interactions in dimedone and phenalen-1,3-dione adducts of 2(4)-pyridinecarboxaldehyde: Enol-enol and ring-chain tautomerism, strong hydrogen bonding, zwitterions

    Science.gov (United States)

    Sigalov, Mark; Shainyan, Bagrat; Krief, Pnina; Ushakov, Igor; Chipanina, Nina; Oznobikhina, Larisa

    2011-12-01

    The 2:1 adducts of dimedone and phenalen-1,3-dione with 2- and 4-pyridine carboxaldehyde, in spite of similar chemical behavior of their diketone precursors, have quite different tautomeric structure both in solid state and in solution. 2,2'-(Pyridin-2-ylmethanediyl)-bis(5,5-dimethyl-cyclohexane-1,3-dione) 5 exists as an equilibrium mixture of its dienol tautomer 5а' with two intramolecular H-bonds ОН⋯О dbnd С and OH ⋯N and the epimeric products of its reversible cyclization, that is, 4a-hydroxy-9-(pyridin-2-yl)-2,3,4,4a,6,7,9,9a-octahydro-5-H-xanthene-1,8-diones 5b (major) and 5c (minor), the latter appears only in polar media like DMSO. 2,2'-(Pyridin-4-ylmethanediyl)bis(5,5-dimethylcyclohexane-1,3-dione) 4, like other 2:1 dimedone-aldehyde adducts, both in solution and in solid state exists as dienol with two intramolecular H-bonds ОН ⋯О dbnd С. 4-[Bis(1H-phenalen-1,3(2H)-dione)methyl]pyridine 6 in nonpolar media like chloroform exists as dienol, but crystallizes from this solvent as zwitter-ion 6b with one very strong ionic hydrogen bond O sbnd H ⋯O sbnd and protonated pyridine nitrogen. The same zwitterion is formed in polar media (DMSO). For 2-[bis(1H-phenalen-1,3(2H)-dione)-methyl]-pyridine 7, fast exchange between its dienol tautomer 7a and zwitter-ion 7b occurs even in CD2Cl2, whereas in DMSO the equilibrium shifts towards zwitter-ion 7b.

  13. EThcD Discrimination of Isomeric Leucine/Isoleucine Residues in Sequencing of the Intact Skin Frog Peptides with Intramolecular Disulfide Bond

    Science.gov (United States)

    Samgina, Tatiana Yu; Kovalev, Sergey V.; Tolpina, Miriam D.; Trebse, Polonca; Torkar, Gregor; Lebedev, Albert T.

    2018-01-01

    Our scientific interests involve de novo sequencing of non-tryptic natural amphibian skin peptides including those with intramolecular S-S bond by means of exclusively mass spectrometry. Reliable discrimination of the isomeric leucine/isoleucine residues during peptide sequencing by means of mass spectrometry represents a bottleneck in the workflow for complete automation of the primary structure elucidation of these compounds. MS3 is capable of solving the problem. Earlier we demonstrated the advanced efficiency of ETD-HCD method to discriminate Leu/Ile in individual peptides by consecutive application of ETD to the polyprotonated peptides followed by HCD applied to the manually selected primary z-ions with the targeted isomeric residues at their N-termini and registration of the characteristic w-ions. Later this approach was extended to deal with several (4-7) broad band mass ranges, without special isolation of the primary z-ions. The present paper demonstrates an advanced version of this method when EThcD is applied in the whole mass range to a complex mixture of natural non-tryptic peptides without their separation and intermediate isolation of the targeted z-ions. The proposed EThcD method showed over 81% efficiency for the large natural peptides with intact disulfide ring, while the interfering process of radical site migration is suppressed. Due to higher speed and sensitivity, the proposed EThcD approach facilitates the analytical procedure and allows for the automation of the entire experiment and data processing. Moreover, in some cases it gives a chance to establish the nature of the residues in the intact intramolecular disulfide loops.

  14. Excited-state intramolecular hydrogen transfer (ESIHT) of 1,8-Dihydroxy-9,10-anthraquinone (DHAQ) characterized by ultrafast electronic and vibrational spectroscopy and computational modeling

    KAUST Repository

    Mohammed, Omar F.

    2014-05-01

    We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S 2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S 1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state. © 2014 American Chemical Society.

  15. Photophysical properties and excited state intramolecular proton transfer in 2-hydroxy-5-[(E)-(4-methoxyphenyl)diazenyl]benzoic acid in homogeneous solvents and micro-heterogeneous environments

    International Nuclear Information System (INIS)

    Gashnga, Pynsakhiat Miki; Singh, T. Sanjoy; Baul, Tushar S. Basu; Mitra, Sivaprasad

    2014-01-01

    A systematic study on the photophysical properties and excited state intramolecular proton transfer (ESIPT) behavior of 2-hydroxy-5-[(E)-(4-methoxyphenyl)diazenyl]benzoic acid, is reported using steady-state and time-resolved fluorescence spectroscopy in homogeneous solvents as well as in different micro-heterogeneous environments. Depending on the nature of intramolecular hydrogen bond (IHB), the salicylic acid derivative may exist in two different ground state conformers (I and II). Structure I having IHB between the carbonyl oxygen and phenolic hydrogen can undergo ESIPT upon excitation as evidenced by largely Stokes-shifted fluorescence at ∼455 nm; whereas, normal fluorescence in the blue side of the spectrum (∼410 nm) is due to the spontaneous emission from conformer II. The results in homogeneous solvents were compared with those in bio-mimicking environments of β-cyclodextrin (CD) and surfactants. The intensity of the ESIPT fluorescence increases substantially upon encapsulation of the probe into the cyclodextrin as well as micellar nano-cavities. Detailed analysis of the spectroscopic data indicates that the probe forms 1:1 complex with CD in aqueous medium. Binding constant of the probe with the micelles as well as critical micelle concentration was obtained from the variation of fluorescence intensity on increasing concentration of different surfactants in aqueous medium. -- Highlights: • Steady state and time resolved fluorescence study on ESIPT in HMBA. • Dual fluorescence corresponding to the pro- and non-ESIPT structures. • Modulation of ESIPT fluorescence in micro-heterogeneous environments. • 1:1 stoichiometry for interaction with cyclodextrin. • Calculation of binding constant and other physico-chemical properties from fluorescence titration data in surfactants

  16. Direct Observation of a Photochemical Alkyne-Allene Reaction and of a Twisted and Rehybridized Intramolecular Charge-Transfer State in a Donor-Acceptor Dyad.

    Science.gov (United States)

    Dereka, Bogdan; Svechkarev, Denis; Rosspeintner, Arnulf; Tromayer, Maximilian; Liska, Robert; Mohs, Aaron M; Vauthey, Eric

    2017-11-22

    The excited-state dynamics of an aniline-triazine electron donor-acceptor dyad with an alkyne spacer has been investigated using a combination of ultrafast broadband mid-IR and visible transient absorption and fluorescence spectroscopies. The transient IR data reveal the occurrence of an efficient alkyne to allene isomerization of the spacer with a time constant increasing from a few hundreds of femtoseconds to a few picoseconds with solvent viscosity. This process is faster than the vibrational cooling of the Franck-Condon excited state, indicative of nonequilibrium dynamics. The transient electronic absorption and fluorescence data evidence that this transformation is accompanied by a charge separation between the donor and the acceptor subunits. The allene character of the spacer implies an orthogonal orientation of the donor and acceptor moieties, similar to that proposed for twisted intramolecular charge-transfer states. Such states are often invoked in the excited-state dynamics of donor-acceptor dyads, but their involvement could never be unambiguously evidenced spectroscopically. The alkyne-allene isomerization involves not only a torsional motion but also a bending of the molecule due to the sp to sp 2 rehybridization of one of the alkyne carbon atoms. This twisted and rehybridized intramolecular charge transfer ("TRICT") state decays back to the planar and linear alkyne ground state on a time scale decreasing from a few hundred to ten picoseconds upon going from weakly to highly polar solvents. The different solvent dependencies reveal that the dynamics of the allene buildup are controlled by the structural changes, whereas the decay is limited by the charge recombination step.

  17. <em>In Vitro em>and <em>in em>Vivo> Antitumor Effect of Trachylobane-360, a Diterpene from<em> Xylopia langsdorffianaem>

    Directory of Open Access Journals (Sweden)

    João Carlos Lima Rodrigues Pita

    2012-08-01

    Full Text Available Trachylobane-360 (<em>ent>-7α-acetoxytrachyloban-18-oic acid was isolated from <em>Xylopia langsdorffianaem>. Studies have shown that it has weak cytotoxic activity against tumor and non-tumor cells. This study investigated the <em>in vitroem>> em>and <em>in vivoem> antitumor effects of trachylobane-360, as well as its cytotoxicity in mouse erythrocytes. In order to evaluate the <em>in vivoem> toxicological aspects related to trachylobane-360 administration, hematological, biochemical and histopathological analyses of the treated animals were performed. The compound exhibited a concentration-dependent effect in inducing hemolysis with HC50 of 273.6 µM, and a moderate <em>in vitroem>> em>concentration-dependent inhibitory effect on the proliferation of sarcoma 180 cells with IC50 values of 150.8 µM and 150.4 µM, evaluated by the trypan blue exclusion test and MTT reduction assay, respectively. The <em>in vivoem> inhibition rates of sarcoma 180 tumor development were 45.60, 71.99 and 80.06% at doses of 12.5 and 25 mg/kg of trachylobane-360 and 25 mg/kg of 5-FU, respectively. Biochemical parameters were not altered. Leukopenia was observed after 5-FU treatment, but this effect was not seen with trachylobane-360 treatment. The histopathological analysis of liver and kidney showed that both organs were mildly affected by trachylobane-360 treatment. Trachylobane-360 showed no immunosuppressive effect. In conclusion, these data reinforce the anticancer potential of this natural diterpene.

  18. Chemical Composition and Insecticidal Activity Against <em>Sitophilus zeamaisem> of the Essential Oils Derived from <em>Artemisia giraldiiem> and <em>Artemisia subdigitataem>

    Directory of Open Access Journals (Sweden)

    Zhi-Long Liu

    2012-06-01

    Full Text Available The aim of this research was to determine the chemical composition and insecticidal activity of the essential oils derived from flowering aerial parts of <em>Artemisia giraldii em>Pamp. and <em>A. subdigitataem> Mattf. (Family: Asteraceae against the maize weevil (<em>Sitophilus zeamaisem> Motsch.. Essential oils of aerial parts of <em>A. giraldiiem> and <em>A. subdigitataem> were obtained from hydrodistillation and investigated by GC and GC-MS. A total of 48 and 33 components of the essential oils of <em>A. giraldiiem> and <em>A. subdigitataem> were identified, respectively. The principal compounds in <em>A. giraldiiem> essential oil were β-pinene (13.18%, <em>iso>-elemicin (10.08%, germacrene D (5.68%, 4-terpineol (5.43% and (<em>Z>-β-ocimene (5.06%. 1,8-Cineole (12.26% and α-curcumene (10.77% were the two main components of the essential oil of <em>A. subdigitataem>, followed by β-pinene (7.38%, borneol (6.23% and eugenol (5.87%. The essential oils of <em>A. giraldiiem> and <em>A. subdigitataem> possessed fumigant toxicity against the maize weevils with LC50 values of 6.29 and 17.01 mg/L air, respectively. The two essential oils of <em>A. giraldiiem> and <em>A. subdigitataem> also exhibited contact toxicity against <em>S. zeamaisem> adults with LD50 values of 40.51 and 76.34 µg/adult, respectively. The results indicated that the two essential oils show potential in terms of fumigant and contact toxicity against grain storage insects.

  19. Purification, Characterization and Antioxidant Activities <em>in Vitroem>> em>and <em>in Vivoem> of the Polysaccharides from <em>Boletus edulisem> Bull

    Directory of Open Access Journals (Sweden)

    Yijun Fan

    2012-07-01

    Full Text Available A water-soluble polysaccharide (BEBP was extracted from <em>Boletus edulis em>Bull using hot water extraction followed by ethanol precipitation. The polysaccharide BEBP was further purified by chromatography on a DEAE-cellulose column, giving three major polysaccharide fractions termed BEBP-1, BEBP-2 and BEBP-3. In the next experiment, the average molecular weight (Mw, IR and monosaccharide compositional analysis of the three polysaccharide fractions were determined. The evaluation of antioxidant activities both <em>in vitroem> and <em>in vivo em>suggested that BEBP-3 had good potential antioxidant activity, and should be explored as a novel potential antioxidant.

  20. Methyl 2-Benzamido-2-(1<em>H>-benzimidazol-1-ylmethoxyacetate

    Directory of Open Access Journals (Sweden)

    Alami Anouar

    2012-09-01

    Full Text Available The heterocyclic carboxylic α-aminoester methyl 2-benzamido-2-(1<em>H>-benzimidazol-1-ylmethoxyacetate is obtained by <em>O>-alkylation of methyl α-azido glycinate <em>N>-benzoylated with 1<em>H>-benzimidazol-1-ylmethanol.

  1. Sulla presenza di <em>Sorex antinoriiem>, <em>Neomys anomalusem> (Insectivora, Soricidae e <em>Talpa caecaem> (Insectivora, Talpidae in Umbria

    Directory of Open Access Journals (Sweden)

    A.M. Paci

    2003-10-01

    Full Text Available Lo scopo del contributo è di fornire un aggiornamento sulla presenza del Toporagno del Vallese <em>Sorex antinoriiem>, del Toporagno acquatico di Miller <em>Neomys anomalusem> e della Talpa cieca <em>Talpa caecaem> in Umbria, dove le specie risultano accertate ormai da qualche anno. A tal fine sono stati rivisitati i reperti collezionati e la bibliografia conosciuta. Toporagno del Vallese: elevato di recente a livello di specie da Brünner et al. (2002, altrimenti considerato sottospecie del Toporagno comune (<em>S. araneus antinoriiem>. È conservato uno di tre crani incompleti (mancano mandibole ed incisivi superiori al momento prudenzialmente riferiti a <em>Sorex> cfr. <em>antinorii>, provenienti dall?Appennino umbro-marchigiano settentrionale (dintorni di Scalocchio - PG, 590 m. s.l.m. e determinati sulla base della pigmentazione rossa degli ipoconi del M1 e M2; Toporagno acquatico di Miller: tre crani (Breda in Paci e Romano op. cit. e un esemplare intero (Paci, ined. sono stati trovati a pochi chilometri di distanza gli uni dall?altro tra i comuni di Assisi e Valfabbrica, in ambienti mediocollinari limitrofi al Parco Regionale del M.te Subasio (Perugia. In provincia di Terni la specie viene segnalata da Isotti (op. cit. per i dintorni di Orvieto. Talpa cieca: sono noti una femmina e un maschio raccolti nel comune di Pietralunga (PG, rispettivamente in una conifereta a <em>Pinus nigraem> (m. 630 s.l.m. e nelle vicinanze di un bosco misto collinare a prevalenza di <em>Quercus cerrisem> (m. 640 s.l.m.. Recentemente un terzo individuo è stato rinvenuto nel comune di Sigillo (PG, all?interno del Parco Regionale di M.te Cucco, sul margine di una faggeta a 1100 m s.l.m. In entrambi i casi l?areale della specie è risultato parapatrico con quello di <em>Talpa europaeaem>.

  2. Glycosylation of Vanillin and 8-Nordihydrocapsaicin by Cultured <em>Eucalyptus perrinianaem> Cells

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    Naoji Kubota

    2012-05-01

    Full Text Available Glycosylation of vanilloids such as vanillin and 8-nordihydrocapsaicin by cultured plant cells of <em>Eucalyptus perrinianaem> was studied. Vanillin was converted into vanillin 4-<em>O>-b-D-glucopyranoside, vanillyl alcohol, and 4-<em>O>-b-D-glucopyranosylvanillyl alcohol by <em>E. perriniana em>cells. Incubation of cultured <em>E. perrinianaem> cells with 8-nor- dihydrocapsaicin gave 8-nordihydrocapsaicin 4-<em>O>-b-D-glucopyranoside and 8-nordihydro- capsaicin 4-<em>O>-b-D-gentiobioside.

  3. Study of the <em>in Vitroem> Antiplasmodial, Antileishmanial and Antitrypanosomal Activities of Medicinal Plants from Saudi Arabia

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    Nawal M. Al-Musayeib

    2012-09-01

    Full Text Available The present study investigated the <em>in vitroem> antiprotozoal activity of sixteen selected medicinal plants. Plant materials were extracted with methanol and screened <em>in vitroem> against erythrocytic schizonts of <em>Plasmodium falciparumem>, intracellular amastigotes of <em>Leishmania infantum em>and <em>Trypanosoma cruzi em>and free trypomastigotes of<em> T. bruceiem>. Cytotoxic activity was determined against MRC-5 cells to assess selectivity<em>. em>The criterion for activity was an IC50 < 10 µg/mL (4. Antiplasmodial activity was found in the<em> em>extracts of<em> em>>Prosopis julifloraem> and <em>Punica granatumem>. Antileishmanial activity<em> em>against <em>L. infantumem> was demonstrated in <em>Caralluma sinaicaem> and <em>Periploca aphylla.em> Amastigotes of<em> T. cruzi em>were affected by the methanol extract of<em> em>>Albizia lebbeckem>> em>pericarp, <em>Caralluma sinaicaem>,> Periploca aphylla em>and <em>Prosopius julifloraem>. Activity against<em> T. brucei em>was obtained in<em> em>>Prosopis julifloraem>. Cytotoxicity (MRC-5 IC50 < 10 µg/mL and hence non-specific activities were observed for<em> em>>Conocarpus lancifoliusem>.>

  4. Retratos em movimento.

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    Luiz Carlos Oliveira Junior

    Full Text Available resumo O artigo aborda aspectos da relação do cinema com a arte do retrato. Buscamos, em primeiro lugar, uma definição estética do que seria um retrato cinematográfico, sempre em tensão com os critérios formais e padrões estilísticos que historicamente constituíram o retrato pictórico. Em seguida, relacionamos essa questão com a importância que se deu à representação do close-up de rosto nas primeiras décadas do cinema, quando foi atribuído aos filmes um papel inédito no estudo da fisionomia e da expressão facial. Por fim, apresentamos exemplos de autorretratos na pintura e no cinema para expor a forma como a autorrepresentação põe em crise as noções de subjetividade e identidade em que a definição clássica do retrato se apoiava.

  5. Natural Products from Antarctic Colonial Ascidians of the Genera <em>Aplidium> and <em>Synoicum>: Variability and Defensive Role

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    Conxita Avila

    2012-08-01

    Full Text Available Ascidians have developed multiple defensive strategies mostly related to physical, nutritional or chemical properties of the tunic. One of such is chemical defense based on secondary metabolites. We analyzed a series of colonial Antarctic ascidians from deep-water collections belonging to the genera <em>Aplidium> and <em>Synoicum> to evaluate the incidence of organic deterrents and their variability. The ether fractions from 15 samples including specimens of the species <em>A.> <em>falklandicum>, <em>A.> <em>fuegiense>, <em>A.> <em>meridianum>, <em>A.> <em>millari> and <em>S.> <em>adareanum> were subjected to feeding assays towards two relevant sympatric predators: the starfish <em>Odontaster> <em>validus>, and the amphipod <em>Cheirimedon> <em>femoratus>. All samples revealed repellency. Nonetheless, some colonies concentrated defensive chemicals in internal body-regions rather than in the tunic. Four ascidian-derived meroterpenoids, rossinones B and the three derivatives 2,3-epoxy-rossinone B, 3-epi-rossinone B, 5,6-epoxy-rossinone B, and the indole alkaloids meridianins A–G, along with other minoritary meridianin compounds were isolated from several samples. Some purified metabolites were tested in feeding assays exhibiting potent unpalatabilities, thus revealing their role in predation avoidance. Ascidian extracts and purified compound-fractions were further assessed in antibacterial tests against a marine Antarctic bacterium. Only the meridianins showed inhibition activity, demonstrating a multifunctional defensive role. According to their occurrence in nature and within our colonial specimens, the possible origin of both types of metabolites is discussed.

  6. Effect of solvent on proton location and dynamic behavior in short intramolecular hydrogen bonds studied by molecular dynamics simulations and NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Yukie, E-mail: mori.yukie@ocha.ac.jp; Masuda, Yuichi

    2015-09-08

    Highlights: • MD simulations were performed to study dynamics of strong hydrogen bonds. • Nuclear magnetic relaxation times of proton were measured in solution. • The hydrogen bond of dibenzoylmethane enol is asymmetric in methanol solution. • Formation or breakage of intermolecular hydrogen bonds can trigger proton transfer. • Dimethylsulfoxide may form a bifurcated hydrogen bond with a hydrogen-bonded system. - Abstract: Hydrogen phthalate anion has a short strong O–H–O hydrogen bond (H-bond). According to previous experimental studies, the H-bond is asymmetric and two tautomers are interconverted in aqueous solutions. In the present study, the effects of polar solvents on the H-bond in a zwitterionic hydrogen phthalate derivative 1 were investigated by quantum mechanics/molecular mechanics molecular dynamics (MD) simulations. The analyses of the trajectories for the methanol solution showed that the H-bonding proton tends to be located closer to the carboxylate group that forms fewer intermolecular H-bonds, than to the other carboxylate group and that the intramolecular proton transfer in 1 is triggered by the breakage and/or formation of an intermolecular H-bond. The enol form of dibenzoylmethane (2) also has a short H-bond, and the OH bond is reported to be rather long (>1.1 Å) in the crystal. In the present study, the effects of the solvent on the H-bond in 2 were investigated by molecular orbital (MO) calculations, MD simulations and nuclear magnetic resonance (NMR) spectroscopy. Density functional theory (DFT) calculations for 2 in vacuum indicated that the barrier height for the intramolecular proton transfer is almost the same as the zero-point energy of the vibrational ground state, resulting in broad distribution of the proton density along the H-bond, owing to the nuclear quantum effect. The OH distances were determined in CCl{sub 4}, acetonitrile, and dimethylsulfoxide solutions from the magnetic dipolar interactions between the {sup 17

  7. Kinetic evidence for the formation of discrete 1,4-dehydrobenzene intermediates. Trapping by inter- and intramolecular hydrogen atom transfer and observation of high-temperature CIDNP

    Energy Technology Data Exchange (ETDEWEB)

    Lockhart, Thomas P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Comita, Paul B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Bergman, Robert G. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States)

    1981-07-01

    Upon heating, alkyl-substituted cis-1,2-diethynyl olefins undergo cyclization to yield reactive 1,4-dehydrobenzenes; the products isolated may be derived from either unimolecular or bimolecular reactions of the intermediate. (Z)-4,5-Diethynyl-4-octene (4) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-dehydrobenzene (17). Solution pyrolysis of 4 in inert aromatic solvents produces three unimolecular products, (Z)-dodeca-4,8-diyn-6-ene (7), benzocyclooctene (9), and o-allyl-n-propylbenzene (10), in high yield. When 1,4-cyclohexadiene is added to the pyrolysis solution as a trapping agent, high yields of the reduced product o-di-n-propylbenzene (12) are obtained. The kinetics of solution pyrolysis of 4 in the presence and absence of trapping agent establish that 2,3-di-n-propyl-1,4-dehydrobenzene is a discrete intermediate on the pathway leading to products. When the reaction was run in the heated probe of an NMR spectrometer, CIDNP was observed in 10. This observation, along with kinetic and chemical trapping evidence, indicates the presence of two additional intermediates, formed from 17 by sequential intramolecular [1,5] hydrogen transfer, on the pathway to products. The observation of CIDNP, coupled with the reactivity exhibited by 17 and the other two intermediates, implicate a biradical description of these molecules. Biradical 17 has been estimated to have a lifetime of about 10-9 s at 200°C and to lie in a well of about 5 kcal/mol with respect to the lowest energy unimolecular pathway ([1,5] hydrogen transfer). Ring opening (expected to be the lowest energy process for 1,4-dehydrobenzenes in which intramolecular hydrogen transfer is unlikely) to the isomeric diethynyl olefin 7 appears to have an activation enthalpy of about 10 kcal/moL Upon thermal reaction in the gas phase (400°C) or in solution in inert solvents (Z)-hexa-2,3-diethyl-1,5-diyn-3-ene (5) rearranges in good yield to the isomeric diethynyl olefin (Z)-deca-3,7-diyn-5-ene (8

  8. Nietzsche em voga

    OpenAIRE

    Borromeu, Carlos

    2015-01-01

    Resumo:Texto publicado em 1941, na revista de orientação católica A Ordem, no Rio de Janeiro. Seu autor considera que Nietzsche teria negado a moral tradicional, concebendo em seu lugar outra, porém imoral e brutal. Acusa o filósofo, por fim, de ser responsável pela Guerra ora e curso na Europa. Abstract:Text published in 1941 in the Catholic orientation magazine, A Ordem, in Rio de Janeiro. The author believes that Nietzsche would have denied traditional morality, conceiving another in it...

  9. Primeiras frases em Libras

    OpenAIRE

    Comissão Editorial

    2017-01-01

    "Primeiras Frases em Libras" é um CD-ROM com interface interativa que tem por objetivo a iniciação na Língua Brasileira de Sinais - Libras. A partir de temas do cotidiano, permite à criança relacionar a imagem a uma estrutura frasal da Libras de forma lúdica, contribuindo para aquisição de conceitos e aspectos culturais. Para a utilização desse material é importante que sejam identificadas as diferenças regionais existentes em alguns sinais e que sejam adaptadas para a Libras local, tornando-...

  10. Identification and Determination of <em>Aconitum> Alkaloids in <em>Aconitum> Herbs and <em>Xiaohuoluo Pillem> Using UPLC-ESI-MS

    Directory of Open Access Journals (Sweden)

    Li Yang

    2012-08-01

    Full Text Available A rapid, specific, and sensitive ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS method to examine the chemical differences between <em>Aconitum> herbs and processed products has been developed and validated. Combined with chemometrics analysis of principal component analysis (PCA and orthogonal projection to latent structural discriminate analysis, diester-diterpenoid and monoester-type alkaloids, especially the five alkaloids which contributed to the chemical distinction between <em>Aconitum> herbs and processed products, namely mesaconitine (MA, aconitine (AC, hypaconitine (HA, benzoylmesaconitine (BMA, and benzoylhypaconitine (BHA, were picked out. Further, the five alkaloids and benzoylaconitine (BAC have been simultaneously determined in the <em>Xiaohuoluo pillem>. Chromatographic separations were achieved on a C18 column and peaks were detected by mass spectrometry in positive ion mode and selected ion recording (SIR mode. In quantitative analysis, the six alkaloids showed good regression, (<em>r> > 0.9984, within the test ranges. The lower limit quantifications (LLOQs for MA, AC, HA, BMA, BAC, and BHA were 1.41, 1.20, 1.92, 4.28, 1.99 and 2.02 ng·mL−1, respectively. Recoveries ranged from 99.7% to 101.7%. The validated method was applied successfully in the analysis of the six alkaloids from different samples, in which significant variations were revealed. Results indicated that the developed assay can be used as an appropriate quality control assay for <em>Xiaohuoluo pillem> and other herbal preparations containing <em>Aconitum> roots.

  11. Conditions to obtain precise and true measurements of the intramolecular {sup 13}C distribution in organic molecules by isotopic {sup 13}C nuclear magnetic resonance spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Bayle, Kevin [EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modelling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3 (France); Gilbert, Alexis [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Earth–Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Julien, Maxime [EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modelling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3 (France); Yamada, Keita [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Silvestre, Virginie; Robins, Richard J.; Akoka, Serge [EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modelling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3 (France); Yoshida, Naohiro [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Earth–Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Remaud, Gérald S., E-mail: gerald.remaud@univ-nantes.fr [EBSI Team, Interdisciplinary Chemistry: Synthesis, Analysis, Modelling (CEISAM), University of Nantes-CNRS UMR 6230, 2 Rue de la Houssinière, BP 92208, F-44322, Nantes Cedex 3 (France)

    2014-10-10

    Highlights: • Evaluation of the trueness and precision criteria of isotopic {sup 13}C NMR spectrometry. • Use of bi-labelled [1,2-{sup 13}C{sub 2}]acetic acid to determine the performance of the instrumental response. • Inter-calibration of the {sup 13}C intramolecular composition of acetic acid using the technique GC-Py–irm-MS. - Abstract: Intramolecular {sup 13}C composition gives access to new information on the (bio) synthetic history of a given molecule. Isotopic {sup 13}C NMR spectrometry provides a general tool for measuring the position-specific {sup 13}C content. As an emerging technique, some aspects of its performance are not yet fully delineated. This paper reports on (i) the conditions required to obtain satisfactory trueness and precision for the determination of the internal {sup 13}C distribution, and (ii) an approach to determining the “absolute” position-specific {sup 13}C content. In relation to (i), a precision of <1% can be obtained whatever the molecule on any spectrometer, once quantitative conditions are met, in particular appropriate proton decoupling efficiency. This performance is a prerequisite to the measurement of isotope fractionation either on the transformed or residual compound when a chemical reaction or process is being studied. The study of the trueness has revealed that the response of the spectrometer depends on the {sup 13}C frequency range of the studied molecule, i.e. the chemical shift range. The “absolute value” and, therefore, the trueness of the {sup 13}C NMR measurements has been assessed on acetic acid and by comparison to the results obtained on the fragments from COOH and CH{sub 3} by isotopic mass spectrometry coupled to a pyrolysis device (GC-Py–irm-MS), this technique being the reference method for acetic acid. Of the two NMR spectrometers used in this work, one gave values that corresponded to those obtained by GC-Py–irm-MS (thus, the “true” value) while the other showed a bias, which was

  12. Intramolecular C−H···π Interactions in Metal-Porphyrin Complexes

    Directory of Open Access Journals (Sweden)

    Snežana D. Zarić

    2004-04-01

    Full Text Available Abstract: Cambridge Structural Database (CSD was screened in order to find intramolecular C−H···π interactions with a chelate ring of coordinated porphyrin. It was found 154 crystal structures with 244 intramolecular C−H···π interactions in transition metal complexes with derivatives of porphyrin. Comparison of interacting distances indicates that interactions of hydrogen atoms in positions 2 and 6 of axially coordinated pyridine are more favorable with ruffled than with planar porphyrin.

  13. Application of transient infrared spectroscopy to intramolecular energy transfer in [(phen) (CO)[sub 3]Re[sup I](NC) Ru[sup II](CN) (bpy)[sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Schoonover, J.R.; Myer, T.J. (Univ. of North Carolina, Chapel Hill, NC (United States)); Gordon, K.C.; Woodruff, W.H.; Peterson, K.A.; Dyer, R.B. (Los Alamos National Lab., NM (United States)); Argazzi, R.; Bignozzi, C.A. (Universita di Ferrara (Italy))

    1993-11-17

    Significant advances have been made in the design and characterization of molecular assemblies, which, when photolyzed, undergo intramolecular electron or energy transfer. Time-resolved resonance Raman spectroscopy has been successfully applied to the study of excited states and molecular assemblies, but time-resolved infrared spectroscopy is particularly well-suited for complexes containing ligands such as CO or CN. Unlike the transient Raman experiment, infrared spectroscopy does not rely on resonance enhancement in the excited state since the metal-CO and -CN stretching vibrations have high oscillator strengths, providing high sensitivity. We describe here a novel application of the technique to the elucidation of intramolecular energy transfer in the ligand-bridged complex [(phen)(CO)[sub 3]Re[sup I](NC) Ru[sup II](CN) (bpy)[sub 2

  14. Espondiloptose em atleta

    Directory of Open Access Journals (Sweden)

    Ana Paula Luppino Assad

    2014-06-01

    Full Text Available Os atletas adolescentes estão sob maior risco de lombalgia e lesões estruturais da coluna. A espondilólise é responsável pela maioria das lombalgias em jovens esportistas e raramente ocorre em adultos. Relatamos o caso de uma paciente de 13 anos, atleta de judô, que chegou a nosso serviço com quadro de cinco meses de lombalgia progressiva durante os treinos, sendo inicialmente atribuída a causas mecânicas, sem que houvesse uma investigação mais detalhada por métodos de imagem. Na admissão já apresentava deformidade lombar, postura antálgica e manobra de hiperextensão lombar em unipodálico positiva bilateralmente. Realizou-se investigação, que evidenciou espondiloptose, sendo, então, submetida a tratamento cirúrgico. Com base neste relato de caso, discutimos a abordagem diagnóstica de lombalgia em atletas jovens, uma vez que a queixa de lombalgia crônica pode ser marcador de uma lesão estrutural, a qual pode ser definitiva e trazer perda funcional irreversível.

  15. Accountability em listas abertas

    Directory of Open Access Journals (Sweden)

    Luis Felipe Miguel

    2010-10-01

    Full Text Available O artigo discute criticamente a percepção, corrente em estudos sobre o sistema eleitoral brasileiro, de que a representação proporcional com listas abertas é um obstáculo à efetivação da accountability. Tal percepção está, em grande medida, baseada em visões equivocadas sobre a natureza do vínculo eleitoral no Brasil e o sentido da accountability, vista como uma relação entre o eleitor e seu candidato e não entre os constituintes e os representantes. O foco nas deficiências do sistema eleitoral, por outro lado, leva a ofuscar outros aspectos mais importantes para o aprimoramento da representação, relacionados à democratização da informação e ao fortalecimento da sociedade civil. Mesmo os problemas identificados nas listas abertas são melhor enfrentados com a ampliação do debate público e o fortalecimento da sociedade civil, que permitiria aos eleitores aproveitar de forma mais consistente as oportunidade de escolha que lhe são oferecidas, mais amplas do que em outros sistemas eleitorais.

  16. Fumigant Antifungal Activity of Myrtaceae Essential Oils and Constituents from <em>Leptospermum petersoniiem> against Three <em>Aspergillus> Species

    Directory of Open Access Journals (Sweden)

    Il-Kwon Park

    2012-09-01

    Full Text Available Commercial plant essential oils obtained from 11 Myrtaceae plant species were tested for their fumigant antifungal activity against <em>Aspergillus ochraceusem>, <em>A. flavusem>, and <em>A. nigerem>. Essential oils extracted from<em> em>Leptospermum> <em>petersonii> at air concentrations of 56 × 10−3 mg/mL and 28 × 10−3 mg/mL completely inhibited the growth of the three <em>Aspergillus> species. However, at an air concentration of 14 × 10−3 mg/mL, inhibition rates of <em>L. petersoniiem> essential oils were reduced to 20.2% and 18.8% in the case of <em>A. flavusem> and <em>A. nigerem>, respectively. The other Myrtaceae essential oils (56 × 10−3 mg/mL only weakly inhibited the fungi or had no detectable affect. Gas chromatography-mass spectrometry analysis identified 16 compounds in <em>L. petersoniiem>> em>essential> em>oil.> em>The antifungal activity of the identified compounds was tested individually by using standard or synthesized compounds. Of these, neral and geranial inhibited growth by 100%, at an air concentration of 56 × 10−3 mg/mL, whereas the activity of citronellol was somewhat lover (80%. The other compounds exhibited only moderate or weak antifungal activity. The antifungal activities of blends of constituents identified in <em>L. petersoniiem> oil indicated that neral and geranial were the major contributors to the fumigant and antifungal activities.

  17. Rh(I-catalyzed intramolecular [2 + 2 + 1] cycloaddition of allenenes: Construction of bicyclo[4.3.0]nonenones with an angular methyl group and tricyclo[6.4.0.01,5]dodecenone

    Directory of Open Access Journals (Sweden)

    Chisato Mukai

    2011-04-01

    Full Text Available The [RhCl(COdppp]2-catalyzed intramolecular carbonylative [2 + 2 + 1] cycloaddition of allenenes was developed to prepare bicyclo[4.3.0]nonenones possessing a methyl group at the ring junction, which is difficult to achieve by the Pauson–Khand reaction of the corresponding enynes. This method also provided a new procedure for the construction of the tricyclo[6.4.0.01,5]dodecenone framework in a satisfactory yield.

  18. Excited-state inter- and intramolecular proton transfer in methyl 3-hydroxy-2-quinoxalinate: effects of solvent and acid or base concentrations

    International Nuclear Information System (INIS)

    Dogra, S.K.

    2005-01-01

    Absorption, fluorescence excitation and fluorescence spectroscopy, combined with time-dependent spectroscopy and semi-empirical (AM1) and density functional theory using Gaussian 98 program calculations have been used to study the effects of solvent and acid or base concentration on the spectral characteristics of methyl 3-hydroxy-2-quinoxalinate (M3HQ). M3HQ is present as enol in less polar solvents and as keto in polar media. In non-polar solvents, large Stokes shifted fluorescence band is assigned to the phototautomer, formed by the excited-state intramolecular proton transfer, whereas fluorescence is only observed from keto in the polar solvents. In aqueous and polar solvents the monocation (MC5/MC6) is formed by protonating the carbonyl oxygen atom in the ground (S 0 ) and the first excited singlet states (S 1 ). Dication is formed by protonating one of ?N- atom of MC5/MC6. Monoanion is formed by deprotonating the phenolic proton of enol in the basic solution. pK a values for different prototropic equilibriums were determined in S 0 and S 1 states and discussed

  19. X-ray investigations of sulfur-containing fungicides. II. Intramolecular forces governing the conformation of four novel alpha-phenylazo- and alpha-phenylhydrazono-beta-ketosulfones.

    Science.gov (United States)

    Wolf , W M

    2001-02-01

    The crystal and molecular structures of four novel beta-ketosulfones, phenyl benzoyl(phenylhydrazono)methyl sulfone (I), phenyl benzoyl(4-nitrophenylhydrazono)methyl sulfone (II), (benzoyl)(phenyl)(phenylazo)methyl phenyl sulfone (III) and (benzoyl)(phenyl)(3-chlorophenylazo)methyl 4-tolyl sulfone (IV), have been investigated using X-ray analysis and density functional theory supplemented by ab initio Hartree-Fock calculations. The conformations of (I) and (II) are stabilized by strong intramolecular resonance-assisted hydrogen bonds formed between the sulfonyl and the alpha-hydrazono moieties. The following increase of a positive charge on the S atoms is compensated via pi-conjugation and stereoelectronic back-donation from the nearby beta-carbonyl group. Compounds (III) and (IV) adopt a strongly distorted propeller shape with pivotal tetrahedral C1 atoms. Distortion mostly follows from the approximate coplanarity of the alpha-azophenyl and alpha-phenyl moieties opposite each other. The main stereoelectronic interactions involve the donation of electron density from the alpha-azo N2 towards the sulfonyl S and the beta-carbonyl C2 atoms.

  20. Circular DNA by "Bis-Click" Ligation: Template-Independent Intramolecular Circularization of Oligonucleotides with Terminal Alkynyl Groups Utilizing Bifunctional Azides.

    Science.gov (United States)

    Yang, Haozhe; Seela, Frank

    2016-01-22

    A highly effective and convenient "bis-click" strategy was developed for the template-independent circularization of single-stranded oligonucleotides by employing copper(I)-assisted azide-alkyne cycloaddition. Terminal triple bonds were incorporated at both ends of linear oligonucleotides. Alkynylated 7-deaza-2'-deoxyadenosine and 2'-deoxyuridine residues with different side chains were used in solid-phase synthesis with phosphoramidite chemistry. The bis-click ligation of linear 9- to 36-mer oligonucleotides with 1,4-bis(azidomethyl)benzene afforded circular DNA in a simple and selective way; azido modification of the oligonucleotide was not necessary. Short ethynyl side chains were compatible with the circularization of longer oligonucleotides, whereas octadiynyl residues were used for short 9-mers. Compared with linear duplexes, circular bis-click constructs exhibit a significantly increased duplex stability over their linear counterparts. The intramolecular bis-click ligation protocol is not limited to DNA, but may also be suitable for the construction of other macrocycles, such as circular RNAs, peptides, or polysaccharides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Intra-molecular lysine-arginine derived advanced glycation end-product cross-linking in Type I collagen: A molecular dynamics simulation study.

    Science.gov (United States)

    Collier, Thomas A; Nash, Anthony; Birch, Helen L; de Leeuw, Nora H

    2016-11-01

    Covalently cross-linked advanced glycation end products (AGE) are among the major post-translational modifications to proteins as a result of non-enzymatic glycation. The formation of AGEs has been shown to have adverse effects on the properties of the collagenous tissue; they are even linked to a number of age related disorders. Little is known about the sites at which these AGEs form or why certain sites within the collagen are energetically more favourable than others. In this study we have used a proven fully atomistic molecular dynamics approach to identify six sites where the formation of the intra-molecular 3-deoxyglucosone-derived imidazolium cross-link (DOGDIC) is energetically favourable. We have also conducted a comparison of these positions with those of the more abundant glucosepane cross-link, to determine any site preference. We show that when we consider both lysine and arginine AGEs, they exhibit a prevalence to form within the gap region of the collagen fibril. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  2. Fluorescent Chemosensors with Varying Degrees of Intramolecular Charge Transfer for Detection of a Nerve Agent Mimic in Solutions and in Vapor.

    Science.gov (United States)

    Cai, Yuan-Chao; Li, Chen; Song, Qin-Hua

    2017-06-23

    Nerve agents are highly toxic organophosphorus compounds, and their possible use in terrorist attacks has led to increasing interest in the development of reliable and accurate methods to detect these lethal chemicals. In this paper, we have prepared six 6-aminoquinolines with various N-substituents as chemosensors for a nerve-agent mimic diethylchlorophosphate (DCP). The chemosensors with the nucleophilic pyridine-N atom as the active site detect DCP via a catalytic hydrolysis approach to form the protonated sensor. The nucleophilicity of the pyridine-N atom depends on the donating ability of the 6-amine group, which affects the intramolecular charge-transfer (ICT) character of sensors and the protonated sensors, leading to different fluorescence-response modes. The effects of the ICT character on the sensing property have been clarified. Among these charge transfer sensors, the sensor 3 displays ratiometric fluorescence response to DCP and a low limit of detection (8 nM). Furthermore, a facile testing strip with 3 has been fabricated with poly(ethylene oxide) for real-time selective monitoring of DCP vapor.

  3. Tandem catalysis in domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization: concise synthesis of 2,6-cis-substituted tetrahydropyran derivatives.

    Science.gov (United States)

    Fuwa, Haruhiko; Noguchi, Takuma; Noto, Kenkichi; Sasaki, Makoto

    2012-10-28

    Herein, we describe the concise synthesis of 2,6-cis-substituted tetrahydropyran derivatives based on a domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization (CM/IOCC) reaction. We have found that the domino CM/IOCC of δ-hydroxy olefins with α,β-unsaturated carbonyl compounds (e.g., trans-crotonaldehyde or N-acryloyl-2,5-dimethylpyrrole) could be efficiently achieved in the presence of the second-generation Hoveyda-Grubbs catalyst under elevated temperature conditions, directly affording 2,6-cis-substituted tetrahydropyrans in excellent yields with synthetically useful diastereoselectivity ("auto-tandem catalysis"). In addition, we have found that the domino CM/IOCC of δ-hydroxy olefins with α,β-unsaturated carbonyl compounds could be achieved simply by performing CM in the presence of a Brønsted acid in CH(2)Cl(2) at 25-35 °C, which delivered 2,6-cis-substituted tetrahydropyrans in good yields with excellent diastereoselectivity ("orthogonal-tandem catalysis"). To understand the mechanism of auto-tandem catalysis in the domino CM/IOCC reaction, we have investigated the role of ruthenium hydride complexes in the IOCC of a ζ-hydroxy α,β-unsaturated ketone as a model case.

  4. Synthesis, Hydrolysis, and Protonation-Promoted Intramolecular Reductive Breakdown of Potential NRTIs: Stavudine α-P-Borano-γ-P-N-l-tryptophanyltriphosphates

    Directory of Open Access Journals (Sweden)

    Zhihong Xu

    2015-10-01

    Full Text Available Phosphorus-modified prodrugs of dideoxynucleoside triphosphates (ddNTPs have shown promise as pronucleotide strategies for improving antiviral activity compared to their parent dideoxynucleosides. Borane modified NTPs offer a promising choice as nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs. However, the availability of α-P-borano-γ-P-substituted NTP analogs remains limited due to challenges with synthesis and purification. Here, we report the chemical synthesis and stability of a new potential class of NRTI prodrugs: stavudine (d4T 5′-α-P-borano-γ-P-N-L-tryptophanyltriphosphates. One-pot synthesis of these compounds was achieved via a modified cyclic trimetaphosphate approach. Pure Rp and Sp diastereomers were obtained after HPLC separation. Based on LC-MS analysis, we report degradation pathways, half-lives (5–36 days and mechanisms arising from structural differences to generate the corresponding borano tri- and di-phosphates, and H-phosphonate, via several parallel routes in buffer at physiologically relevant pH and temperature. Here, the major hydrolysis products, d4T α-P-boranotriphosphate Rp and Sp isomers, were isolated by HPLC and identified with spectral data. We first propose that one of the major degradation products, d4T H-phosphonate, was generated from the d4T pronucleotides via a protonation-promoted intramolecular reduction followed by a second step nucleophilic attack. This report could provide valuable information for pronucleotide-based drug design in terms of selective release of target nucleotides.

  5. A highly selective turn-on fluorescent probe for hypochlorous acid based on hypochlorous acid-induced oxidative intramolecular cyclization of boron dipyrromethene-hydrazone

    International Nuclear Information System (INIS)

    Chen, Wei-Chieh; Venkatesan, Parthiban; Wu, Shu-Pao

    2015-01-01

    Highlights: • A BODIPY-based fluorescent probe for sensing HOCl was developed. • The probe utilizes the HOCl-promoted cyclization in response to the amount of HOCl. • The probe might have application in the investigation of HOCl in biological systems. - Abstract: A BODIPY-based fluorescent probe, HBP, was developed for the detection of hypochlorous acid based on the specific hypochlorous acid-promoted oxidative intramolecular cyclization of heterocyclic hydrazone in response to the amount of HOCl. The reaction is accompanied by a 41-fold increase in the fluorescent quantum yield (from 0.004 to 0.164). The fluorescence intensity of the reaction between HOCl and HBP is linear in the HOCl concentration range of 1–8 μM with a detection limit of 2.4 nM (S/N = 3). Confocal fluorescence microscopy imaging using RAW264.7 cells showed that the new probe HBP could be used as an effective fluorescent probe for detecting HOCl in living cells

  6. External Electric Field Effects on Excited-State Intramolecular Proton Transfer in 4'-N,N-Dimethylamino-3-hydroxyflavone in Poly(methyl methacrylate) Films.

    Science.gov (United States)

    Furukawa, Kazuki; Hino, Kazuyuki; Yamamoto, Norifumi; Awasthi, Kamlesh; Nakabayashi, Takakazu; Ohta, Nobuhiro; Sekiya, Hiroshi

    2015-09-17

    The external electric field effects on the steady-state electronic spectra and excited-state dynamics were investigated for 4'-N,N-(dimethylamino)-3-hydroxyflavone (DMHF) in a poly(methyl methacrylate) (PMMA) film. In the steady-state spectrum, dual emission was observed from the excited states of the normal (N*) and tautomer (T*) forms. Application of an external electric field of 1.0 MV·cm(-1) enhanced the N* emission and reduced the T* emission, indicating that the external electric field suppressed the excited-state intramolecular proton transfer (ESIPT). The fluorescence decay profiles were measured for the N* and T* forms. The change in the emission intensity ratio N*/T* induced by the external electric field is dominated by ESIPT from the Franck-Condon excited state of the N* form and vibrational cooling in potential wells of the N* and T* forms occurring within tens of picoseconds. Three manifolds of fluorescent states were identified for both the N* and T* forms. The excited-state dynamics of DMHF in PMMA films has been found to be very different from that in solution due to intermolecular interactions in a rigid environment.

  7. A comprehensive spectroscopic and computational investigation of intramolecular proton transfer in the excited states of 2-(2′-hydroxyphenyl) benzoxazole and its derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Padalkar, Vikas S. [Tinctorial Chemistry Group, Institute of Chemical Technology, Matunga, Mumbai 400019 (India); Ramasami, Ponnadurai, E-mail: ramchemi@intnet.mu [Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit (Mauritius); Sekar, Nagaiyan, E-mail: n.sekar@ictmumbai.edu.in [Tinctorial Chemistry Group, Institute of Chemical Technology, Matunga, Mumbai 400019 (India)

    2014-02-15

    The excited-state intramolecular proton transfer (ESIPT) fluorescence of the 2-(2′ hydroxyphenyl) benzoxazole (HBO) and its derivatives with NO{sub 2} as electron acceptor and NH{sub 2} as electron donor at the 4 and 5 position of benzoxazole ring was studied by spectroscopic and computational methods. The changes in the electronic transition, energy levels, and orbital diagrams of the HBO derivatives were investigated using the DFT computations and they were correlated with the experimental spectral emission. The benzoxazole derivatives are fluorescent under UV-light in solution. Photophysical properties of the compounds were also studied in solvents of different polarities. Experimental absorption and emission wavelengths are in agreement with those computed with a deviation ranging between 0 and 50%. The computational methods have been useful for molecular understanding of the transitions responsible for the fluorescent spectra. -- Highlights: • Experimental photophysical properties of 2-substituted benzoxazoles in different solvents have been studied and compared with the computational data. • Compounds show dual emission due to ESIPT process and was supported by DFT and TD-DFT computations. • Experimental results and computational results are in good agreements.

  8. Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer

    International Nuclear Information System (INIS)

    Paul, Bijan Kumar; Guchhait, Nikhil

    2013-01-01

    Highlights: ► Intramolecular hydrogen bonding (IMHB) in salicylic acid and its chloro derivatives. ► A complex effect of +R and −I effect of chlorine substituents on IMHB energy. ► Interplay between IMHB energy and aromaticity. ► Directional nature of IMHB from quantum chemical assessment. ► Quantum chemical treatment vs. geometrical criteria to assess weak interaction. - Abstract: Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ρ(r) and Laplacian ∇ 2 ρ(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ρ(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems

  9. Iodo em alimentos consumidos em Portugal

    OpenAIRE

    Coelho, Inês; Delgado, Inês; Costa, Sofia; Castanheira, Isabel; Calhau, Maria Antónia

    2015-01-01

    O iodo é um elemento vestigial essencial na dieta humana e animal, com uma importância nutricional bem estabelecida. É indispensável para a síntese das hormonas da tiroide, tiroxina e triiodotirosina, cujo principal papel está relacionado com o crescimento e desenvolvimento dos órgãos, em particular do cérebro. A fonte natural de iodo são os alimentos. Contudo, de acordo com a OMS um terço da população mundial sofre de algum tipo de carência de iodo. A deficiência crônica de iodo pode levar a...

  10. Efecto de extractos vegetales de <em>Polygonum hydropiperoidesem>, <em>Solanum nigrumem> y <em>Calliandra pittieriem> sobre el gusano cogollero (<em>Spodoptera frugiperdaem>

    Directory of Open Access Journals (Sweden)

    Lizarazo H. Karol

    2008-12-01

    Full Text Available

    El gusano cogollero <em>Spodoptera frugiperdaem> es una de las plagas que más afectan los cultivos en la región de Sumapaz (Cundinamarca, Colombia. En la actualidad se controla principalmente aplicando productos de síntesis química, sin embargo la aplicación de extractos vegetales surge como una alternativa de menor impacto sobre el ambiente. Este control se emplea debido a que las plantas contienen metabolitos secundarios que pueden inhibir el desarrollo de los insectos. Por tal motivo, la presente investigación evaluó el efecto insecticida y antialimentario de extractos vegetales de barbasco <em>Polygonum hydropiperoidesem> (Polygonaceae, carbonero <em>Calliandra pittieriem> (Mimosaceae y hierba mora <em>Solanum nigrumem> (Solanaceae sobre larvas de <em>S. frugiperdaem> biotipo maíz. Se estableció una cría masiva del insecto en el laboratorio utilizando una dieta natural con hojas de maíz. Posteriormente se obtuvieron extractos vegetales utilizando solventes de alta polaridad (agua y etanol y media polaridad (diclorometano los cuales se aplicaron sobre las larvas de segundo instar. Los resultados más destacados se presentaron con extractos de <em>P. hydropiperoidesem>, obtenidos con diclorometano en sus diferentes dosis, con los cuales se alcanzó una mortalidad de 100% 12 días después de la aplicación y un efecto antialimentario representado por un consumo de follaje de maíz inferior al 4%, efectos similares a los del testigo comercial (Clorpiriphos.

  11. Primeiras frases em Libras

    Directory of Open Access Journals (Sweden)

    Comissão Editorial

    2017-02-01

    Full Text Available "Primeiras Frases em Libras" é um CD-ROM com interface interativa que tem por objetivo a iniciação na Língua Brasileira de Sinais - Libras. A partir de temas do cotidiano, permite à criança relacionar a imagem a uma estrutura frasal da Libras de forma lúdica, contribuindo para aquisição de conceitos e aspectos culturais. Para a utilização desse material é importante que sejam identificadas as diferenças regionais existentes em alguns sinais e que sejam adaptadas para a Libras local, tornando-se mais um exercício enriquecedor para aquisição e prática da Língua de Sinais. Maiores informações sobre o material no site da Editora Arara Azul: www.editora-arara-azul.com. br

  12. Quedas em idosos

    OpenAIRE

    Meneses, Joana Gonçalves de

    2016-01-01

    Trabalho final do mestrado em medicina do desporto com vista à atribuição do Grau de Mestre (área científica de geriatria), apresentado à Faculdade de Medicina da Universidade de Coimbra As quedas na população idosa constituem um grande problema de saúde pública, tendo em conta a sua dimensão física, psicológica, económica e social. Subjacente à ocorrência destes acontecimentos existe uma série de fatores de risco, como a idade, falta de equilíbrio, sedentarismo, doenças crónicas, a polime...

  13. Hipervitaminose D em animais

    Directory of Open Access Journals (Sweden)

    Paulo V. Peixoto

    2012-07-01

    Full Text Available Por meio de revisão da literatura, são apresentados dados referentes ao metabolismo da vitamina D, bem como aos principais aspectos toxicológicos, clínicos, bioquímicos, macroscópicos, microscópicos, ultraestruturais, imuno-histoquímicos e radiográficos de animais intoxicados natural e experimentalmente por essa vitamina, em diferentes espécies. Este estudo objetiva demonstrar a existência de muitas lacunas no conhecimento sobre mineralização fisiológica e patológica, em especial na mediação hormonal do fenômeno, bem como alertar para os riscos de ocorrência dessa intoxicação.

  14. CORANTES ARTIFICIAIS EM ALIMENTOS

    Directory of Open Access Journals (Sweden)

    Marcelo Alexandre PRADO

    2009-07-01

    Full Text Available

    O emprego de aditivos químicos é, sem dúvida, um dos mais polêmicos avanços alcançados pela indústria de alimentos. Os corantes artificiais pertencem a uma dessas classes de aditivos alimentares e têm sido objeto de muitas críticas, já que seu uso em muitos alimentos justifica-se apenas por questões de hábitos alimentares. Ainda existem diferentes opiniões quanto à inocuidade dos diversos corantes artificiais. Visando, principalmente, o controle no uso dos corantes sintéticos, mas tendo em vista que produtos coloridos artificialmente são exportados e importados, a análise desses aditivos requer métodos eficientes e rápidos para a detecção, identificação e quantificação. A cromatografia em papel e em camada delgada, apesar de serem técnicas relativamente rápidas, apresentam dados com baixa exatidão e precisão. Já na cromatografia líquida de alta eficiência (CLAE as maiores dificuldades encontram-se nas etapas de extração, mas principalmente no alto custo do equipamento. A eletroforese capilar apresenta os mesmos problemas da CLAE, aliados ao fato de se tratar de uma técnica relativamente recente para a análise desse tipo de substância e, portanto, existem poucos estudos a cerca da determinação e quantificação. PALAVRAS-CHAVE: Corantes artificiais; análise; legislação; CLAE; EC

  15. O estresse em escolares

    Directory of Open Access Journals (Sweden)

    Marilda E. Novaes Lipp

    Full Text Available A presença de sintomas de estresse foi pesquisada em uma amostra de 255 escolares de 7 a 14 anos de idade, oriundos de três tipos diferentes de escolas (municipal, particular e particular confessional filantrópica. Os dados foram analisados em termos de diferenças entre as escolas, sexo e série do ensino fundamental em que as crianças se encontravam. Constatou-se que o tipo de escola tinha uma forte associação com o nível de estresse dos alunos e que o número de meninas com estresse era significativamente maior do que o dos meninos. Verificou-se também que o estresse diminui nas séries mais elevadas e estava mais presente na primeira série. Pode-se concluir que as escolas têm um papel relevante no estresse infantil e que é possível dentro de uma escola apresentar níveis baixos de estresse, dependendo das características da mesma.

  16. Rapid Development of Microsatellite Markers with 454 Pyrosequencing in a Vulnerable Fish<em>,> the Mottled Skate<em>, Raja em>pulchra>

    Directory of Open Access Journals (Sweden)

    Jung-Ha Kang

    2012-06-01

    Full Text Available The mottled skate, <em>Raja pulchraem>, is an economically valuable fish. However, due to a severe population decline, it is listed as a vulnerable species by the International Union for Conservation of Nature. To analyze its genetic structure and diversity, microsatellite markers were developed using 454 pyrosequencing. A total of 17,033 reads containing dinucleotide microsatellite repeat units (mean, 487 base pairs were identified from 453,549 reads. Among 32 loci containing more than nine repeat units, 20 primer sets (62% produced strong PCR products, of which 14 were polymorphic. In an analysis of 60 individuals from two <em>R. pulchra em>populations, the number of alleles per locus ranged from 1–10, and the mean allelic richness was 4.7. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The Hardy–Weinberg equilibrium test showed significant deviation in two of the 28 single-loci after sequential Bonferroni’s correction. Using 11 primer sets, cross-species amplification was demonstrated in nine related species from four families within two classes. Among the 11 loci amplified from three other <em>Rajidae> family species; three loci were polymorphic. A monomorphic locus was amplified in all three <em>Rajidae> family species and the <em>Dasyatidae> family. Two <em>Rajidae> polymorphic loci amplified monomorphic target DNAs in four species belonging to the Carcharhiniformes class, and another was polymorphic in two Carcharhiniformes species.

  17. Solidariedade em Redes

    Directory of Open Access Journals (Sweden)

    Angie Gomes Gomes Biondi

    2015-03-01

    Full Text Available O discurso da comum humanidade que vinculava sofredor e espectador na base de uma moralidade piedosa caducou frente às solicitações de uma sociedade tecnológica, multicultural e pluralista. Ao repertório do protesto e da denúncia, como instrumentos privilegiados da modernidade, prevalecem agora novos apelos à chamada “sensibilidade humanitária” (CHOULIARAKI, 2013 posta diretamente a cada sujeito social conectado. Deste modo, uma profusão de causas individuais tem se amontoado nas redes sociais (não raro, multiplicadas pelos meios de comunicação tradicionais todos os dias. Causas que se declaram legítimas e justificáveis em tempos de uma precária e insuficiente participação do Estado e que se orientam para uma ação direta às vítimas e oprimidos. Contudo, as interações afetivas que subjazem estes apelos solidários se coadunam à lógica de um capitalismo flexível que toma a própria vida em sua vertente criativa, como núcleo de produção econômica, ou seja, como forma de capitalização da própria vida cotidiana. Neste texto buscamos desenvolver uma etapa descritiva destas convocações solidárias como uma prática baseada na lógica conexionista que tem vigorado em nossa sociedade. Alguns casos são trazidos para pensar o lugar da vítima enquanto instância privilegiada de sua própria enunciação, os mecanismos de visibilidade que são articulados na comunicação modulada pelas redes e em que medida é possível pensar tais práticas como uma espécie de atualização das ações solidárias baseadas em uma “política do conexionismo”, conforme indicam os estudos de Boltanski e Chiapello (2013.

  18. Acarofauna em plantas ornamentais

    Directory of Open Access Journals (Sweden)

    Jania Claudia Camilo dos Santos

    2014-10-01

    Full Text Available Normal 0 21 false false false PT-BR X-NONE X-NONE O cultivo e o comercio de plantas ornamentais vem cada vez mais ganhando espaço no Brasil, pela grande variedade das espécies existentes e exuberância de suas flores, que oferecem uma maior riqueza ao local. Dessa forma, o objetivo desse trabalho foi realizar o levantamento da população de ácaros associados às plantas ornamentais no município de Arapiraca-AL, em função dos diversos problemas acarretados por essa espécie. O levantamento foi realizado entre os meses de abril a março, através de amostragens mensais de folhas coletadas da parte basal, intermediária e apical de plantas existentes em praças e jardins. Foram coletados 55 ácaros pertencentes à ordem Prostigmata em 20 famílias de plantas. As plantas com as maiores riquezas de ácaros foram as Coleus blumei L. e Bxuxus sempervirens L., que apresentaram 65% dos valores amostrais. Analisando-se as coletas realizadas, pode-se observar que houve uma maior incidência populacional de ácaros na coleta do mês de maio, cuja percentagem foi de 36% de ácaros levantados, sendo que no levantamento dos dados amostrais de março a percentagem encontrada foi de 14%, nas amostragens dos meses de abril e junho, a percentagem amostrada dos dados foi de 22 e 28%, respectivamente. O estudo do levantamento de ácaros em plantas ornamentais permitiu observar a relação entre ácaros e a relação com a planta hospedeira, facilitando posteriormente um estudo mais aprofundado sobre plantas hospedeiras, e pode-se observar que em períodos chuvosos ocorre uma menor incidência populacional.

  19. How <em>Varroa> Parasitism Affects the Immunological and Nutritional Status of the Honey Bee, <em>Apis melliferaem>

    Directory of Open Access Journals (Sweden)

    Katherine A. Aronstein

    2012-06-01

    Full Text Available We investigated the effect of the parasitic mite <em>Varroa destructorem> on the immunological and nutritional condition of honey bees, <em>Apis melliferaem>, from the perspective of the individual bee and the colony. Pupae, newly-emerged adults and foraging adults were sampled from honey bee colonies at one site in S. Texas, USA. <em>Varroa>‑infested bees displayed elevated titer of Deformed Wing Virus (DWV, suggestive of depressed capacity to limit viral replication. Expression of genes coding three anti-microbial peptides (<em>defensin1, abaecin, hymenoptaecinem> was either not significantly different between <em>Varroa>-infested and uninfested bees or was significantly elevated in <em>Varroa>-infested bees, varying with sampling date and bee developmental age. The effect of <em>Varroa> on nutritional indices of the bees was complex, with protein, triglyceride, glycogen and sugar levels strongly influenced by life-stage of the bee and individual colony. Protein content was depressed and free amino acid content elevated in <em>Varroa>-infested pupae, suggesting that protein synthesis, and consequently growth, may be limited in these insects. No simple relationship between the values of nutritional and immune-related indices was observed, and colony-scale effects were indicated by the reduced weight of pupae in colonies with high <em>Varroa> abundance, irrespective of whether the individual pupa bore <em>Varroa>.

  20. Deacidification of <em>Pistacia> <em>chinensis> Oil as a Promising Non-Edible Feedstock for Biodiesel Production in China

    Directory of Open Access Journals (Sweden)

    Yuan Meng

    2012-07-01

    Full Text Available <em>Pistacia> <em>chinensis> seed oil is proposed as a promising non-edible feedstock for biodiesel production. Different extraction methods were tested and compared to obtain crude oil from the seed of <em>Pistacia> <em>chinensis>, along with various deacidification measures of refined oil. The biodiesel was produced through catalysis of sodium hydroxide (NaOH and potassium hydroxide (KOH. The results showed that the acid value of <em>Pistacia> <em>chinensis> oil was successfully reduced to 0.23 mg KOH/g when it was extracted using ethanol. Consequently, the biodiesel product gave a high yield beyond 96.0%. The transesterification catalysed by KOH was also more complete. Fourier transform infrared (FTIR spectroscopy was used to monitor the transesterification reaction. Analyses by gas chromatography-mass spectrometry (GC-MS and gas chromatography with a flame ionisation detector (GC-FID certified that the <em>Pistacia> <em>chinensis> biodiesel mainly consisted of C18 fatty acid methyl esters (81.07% with a high percentage of methyl oleate. Furthermore, the measured fuel properties of the biodiesel met the required standards for fuel use. In conclusion, the <em>Pistacia> <em>chinensis> biodiesel is a qualified and feasible substitute for fossil diesel.

  1. On subspecific taxonomy of <em>Microtus saviiem> (Rodentia, Arvicolidae

    Directory of Open Access Journals (Sweden)

    Longino Contoli

    2003-10-01

    Full Text Available Riassunto Sulla tassonomia sottospecifica di <em>Microtus saviiem> (Rodentia, Arvicolidae Viene riveduta e riassunta la situazione tassonomica sottospecifica di <em>Microtus (Terricola saviiem>, anche tramite la descrizione di due nuovi taxa: <em>Microtus (Terricola savii tolfetanusem>, dei Monti della Tolfa e <em>Microtus (Terricola savii niethammericusem>, del Gargano.

  2. Vibration-rotation alchemy in acetylene (12C2H2), ? at low vibrational excitation: from high resolution spectroscopy to fast intramolecular dynamics

    Science.gov (United States)

    Perry, David S.; Miller, Anthony; Amyay, Badr; Fayt, André; Herman, Michel

    2010-04-01

    The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), ? with up to 8600 cm-1 of vibrational energy. This comparison is based on the extensive and reliable knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision [B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys. 131, 114301 (2009)]. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities in intramolecular vibrational redistribution (IVR) are first investigated for the v 4 + v 5 and v 3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor φ d, the IVR lifetime τ IVR , and the recurrence time τ rec. For the two bright states v 3 + 2v 4 and 7v 4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7v 4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states.

  3. Two states are not enough: quantitative evaluation of the valence-bond intramolecular charge-transfer model and its use in predicting bond length alternation effects.

    Science.gov (United States)

    Jarowski, Peter D; Mo, Yirong

    2014-12-15

    The structural weights of the canonical resonance contributors used in the Two-state valence-bond charge-transfer model, neutral (N, R1) and ionic (VB-CT, R2), to the ground states and excited states of a series of linear dipolar intramolecular charge-transfer chromophores containing a buta-1,3-dien-1,4-diyl bridge have been computed by using the block-localized wavefunction (BLW) method at the B3LYP/6-311+G(d) level to provide the first quantitative assessment of this simple model. Ground- and excited-state analysis reveals surprisingly low ground-state structural weights for the VB-CT resonance form using either this Two-state model or an expanded Ten-state model. The VB-CT state is found to be more prominent in the excited state. Individual resonance forms were structurally optimized to understand the origins of the bond length alternation (BLA) of the bridging unit. Using a Wheland energy-based weighting scheme, the weighted average of the optimized bond lengths with the Two-state model was unable to reproduce the BLA features with values 0.04 to 0.02 Å too large compared to the fully delocalized (FD) structure (BLW: ca. -0.13 to -0.07 Å, FD: ca. -0.09 to -0.05 Å). Instead, an expanded Ten-state model fit the BLA values of the FD structure to within only 0.001 Å of FD. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A novel chalcone-analogue as an optical sensor based on ground and excited states intramolecular charge transfer: A combined experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Fayed, Tarek A. [Chemistry Department, Faculty of Science, Tanta University, 31527-Tanta (Egypt)], E-mail: tfayed2003@yahoo.co.uk

    2006-05-31

    Steady-state absorption and emission spectroscopic techniques as well as semiempirical quantum calculations at the AM1 and ZINDO/S levels have been used to investigate the intramolecular charge transfer (ICT) behaviour of a novel chalcone namely; 1-(2-pyridyl)-5-(4-dimethylaminophenyl)-penta-2,4-diene-1-one, DMAC. The ground state DMAC has a significant ICT character and a great sensitivity to the hydrogen bond donating ability of the medium as reflected from the change of the absorption spectra in pure and mixed organic solvents. On the other hand, its excited singlet state exhibits high ICT characters as manifested by the drastic solvatochromic effects. These results are consistent with the data of charge density calculations in both the ground and excited state, which indicates enhancement of the charge transfer from the dimethyl-amino group to the carbonyl oxygen upon excitation. Also, the dipole moment calculations indicates a highly dipolar excited singlet state ({delta}{mu} {sub eg} = 15.5 D). The solvent dependence of the fluorescence quantum yield of DMAC was interpreted on the basis of positive and negative solvatokinetic as well as the hydrogen bonding effects. Incorporation of the 2-pyridyl group in the chemical structure of the present DMAC led to design of a potential optical sensor for probing acidity of the medium and metal cations such as Zn{sup 2+}, Cd{sup 2+} and Hg{sup 2+}. This was concluded from the high acidochromic and metallochromic behaviour of DMAC on adding such cations to its acetonitrile solutions.

  5. Intramolecular Singlet Fission in Quinoidal Bi- and Tetrathiophenes: A Comparative Study of Low-Lying Excited Electronic States and Potential Energy Surfaces.

    Science.gov (United States)

    Momeni, Mohammad R

    2016-10-11

    Quinoidal bithiophene has recently been introduced ( Varnavski, O. et al. J. Phys. Chem. Lett. 2015 , 6 , 1375 - 1384 ) as a very promising isolated organic compound for intramolecular singlet fission (iSF) with an outstanding SF quantum yield of ≈180%. In contrast, another recent study ( Ren, L. et al. J. Am. Chem. Soc. 2015 , 137 , 11294 - 11302 ) revealed that quinoidal tetrathiophenes have no activity in the iSF process and are strong fluorophores instead, with measured fluorescent quantum yields up to 53.1%. Using DFT and TD-DFT methods, the authors of the second contribution attributed the marked differences between these compounds to faster reverse T 2 → S 1 intersystem crossing processes in the tetrathiophenes. To address this unprecedented discrepancy, quinoidal bithiophene and tetrathiophene compounds and their derivatives are carefully examined using the CASPT2 technique. Theoretical evidence is provided through detailed investigation of CASPT2 potential energy surfaces of different singlet and triplet states involved in the iSF process. Through comparison of the CASPT2 results with the CASSCF and RAS-2SF data, it is found that the dynamic electron correlation present in the CASPT2 method plays a crucial role for correct description of the multiexciton nature of the triplet pair 1 [TT] state in quinoidal bi- and tetrathiophenes. Effects of substitution and structural modification on iSF activity of these compounds are also examined using the CASPT2 method where the obtained results are in accordance with previous experimental predictions. These results contribute to a better understanding of the iSF mechanism in quinoidal systems which could be relevant for designing new iSF active compounds.

  6. Intramolecular ex vivo Fluorescence Resonance Energy Transfer (FRET of Dihydropyridine Receptor (DHPR β1a Subunit Reveals Conformational Change Induced by RYR1 in Mouse Skeletal Myotubes.

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    Dipankar Bhattacharya

    Full Text Available The dihydropyridine receptor (DHPR β1a subunit is essential for skeletal muscle excitation-contraction coupling, but the structural organization of β1a as part of the macromolecular DHPR-ryanodine receptor type I (RyR1 complex is still debatable. We used fluorescence resonance energy transfer (FRET to probe proximity relationships within the β1a subunit in cultured skeletal myotubes lacking or expressing RyR1. The fluorescein biarsenical reagent FlAsH was used as the FRET acceptor, which exhibits fluorescence upon binding to specific tetracysteine motifs, and enhanced cyan fluorescent protein (CFP was used as the FRET donor. Ten β1a reporter constructs were generated by inserting the CCPGCC FlAsH binding motif into five positions probing the five domains of β1a with either carboxyl or amino terminal fused CFP. FRET efficiency was largest when CCPGCC was positioned next to CFP, and significant intramolecular FRET was observed for all constructs suggesting that in situ the β1a subunit has a relatively compact conformation in which the carboxyl and amino termini are not extended. Comparison of the FRET efficiency in wild type to that in dyspedic (lacking RyR1 myotubes revealed that in only one construct (H458 CCPGCC β1a -CFP FRET efficiency was specifically altered by the presence of RyR1. The present study reveals that the C-terminal of the β1a subunit changes conformation in the presence of RyR1 consistent with an interaction between the C-terminal of β1a and RyR1 in resting myotubes.

  7. A molecular dynamics study of intramolecular proton transfer reaction of malonaldehyde in solutions based upon mixed quantum-classical approximation. I. Proton transfer reaction in water.

    Science.gov (United States)

    Yamada, Atsushi; Kojima, Hidekazu; Okazaki, Susumu

    2014-08-28

    In order to investigate proton transfer reaction in solution, mixed quantum-classical molecular dynamics calculations have been carried out based on our previously proposed quantum equation of motion for the reacting system [A. Yamada and S. Okazaki, J. Chem. Phys. 128, 044507 (2008)]. Surface hopping method was applied to describe forces acting on the solvent classical degrees of freedom. In a series of our studies, quantum and solvent effects on the reaction dynamics in solutions have been analysed in detail. Here, we report our mixed quantum-classical molecular dynamics calculations for intramolecular proton transfer of malonaldehyde in water. Thermally activated proton transfer process, i.e., vibrational excitation in the reactant state followed by transition to the product state and vibrational relaxation in the product state, as well as tunneling reaction can be described by solving the equation of motion. Zero point energy is, of course, included, too. The quantum simulation in water has been compared with the fully classical one and the wave packet calculation in vacuum. The calculated quantum reaction rate in water was 0.70 ps(-1), which is about 2.5 times faster than that in vacuum, 0.27 ps(-1). This indicates that the solvent water accelerates the reaction. Further, the quantum calculation resulted in the reaction rate about 2 times faster than the fully classical calculation, which indicates that quantum effect enhances the reaction rate, too. Contribution from three reaction mechanisms, i.e., tunneling, thermal activation, and barrier vanishing reactions, is 33:46:21 in the mixed quantum-classical calculations. This clearly shows that the tunneling effect is important in the reaction.

  8. Roles of Intramolecular and Intermolecular Interactions in Functional Regulation of the Hsp70 J-protein Co-Chaperone Sis1

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hyun Young; Ziegelhoffer, Thomas; Osipiuk, Jerzy; Ciesielski, Szymon J.; Baranowski, Maciej; Zhou, Min; Joachimiak, Andrzej; Craig, Elizabeth A.

    2015-04-01

    Unlike other Hsp70 molecular chaperones, those of the eukaryotic cytosol have four residues, EEVD, at heir C-termini. EEVD(Hsp70) binds adaptor proteins of the Hsp90 chaperone system and mitochondrial membrane preprotein receptors, thereby facilitating processing of Hsp70-bound clients through protein folding and translocation pathways. Among J-protein co-chaperones functioning in these pathways, Sis1 is unique, as it also binds the EEVD(Hsp70) motif. However, little is known about the role of the Sis1:EEVD(Hsp70) interaction. We found that deletion of EEVD(Hsp70) abolished the ability of Sis1, but not the ubiquitous J-protein Ydj1, to partner with Hsp70 in in vitro protein refolding. Sis1 co-chaperone activity with Hsp70ΔEEVD was restored upon substitution of a glutamic acid of the J-domain. Structural analysis revealed that this key glutamic acid, which is not present in Ydj1, forms a salt bridge with an arginine of the immediately adjacent glycine-rich region. Thus, restoration of Sis1 in vitro activity suggests that intramolecular interactions between the J-domain and glycine-rich region control co-chaperone activity, which is optimal only when Sis1 interacts with the EEVD(Hsp70) motif. However, we found that disruption of the Sis1:EEVD(Hsp70) interaction enhances the ability of Sis1 to substitute for Ydj1 in vivo. Our results are consistent with the idea that interaction of Sis1 with EEVD(Hsp70) minimizes transfer of Sis1-bound clients to Hsp70s that are primed for client transfer to folding and translocation pathways by their preassociation with EEVD binding adaptor proteins. These interactions may be one means by which cells triage Ydj1- and Sis1-bound clients to productive and quality control pathways, respectively.

  9. Excited-state intramolecular proton transfer (ESIPT) emission of hydroxyphenylimidazopyridine: computational study on enhanced and polymorph-dependent luminescence in the solid state.

    Science.gov (United States)

    Shigemitsu, Yasuhiro; Mutai, Toshiki; Houjou, Hirohiko; Araki, Koji

    2012-12-13

    Although 2-(2'-hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP) is only weakly fluorescent in solution, two of its crystal polymorphs in which molecules are packed as stacked pairs and in nearly coplanar conformation exhibit bright excited-state intramolecular proton transfer (ESIPT) luminescence of different colors (blue-green and yellow). In order to clarify the enhanced and polymorph-dependent luminescence of HPIP in the solid state, the potential energy surfaces (PESs) of HPIP in the ground (S(0)) and excited (S(1)) states were analyzed computationally by means of ab initio quantum chemical calculations. The calculations reproduced the experimental photophysical properties of HPIP in solution, indicating that the coplanar keto form in the first excited (S(1)) state smoothly approaches the S(0)/S(1) conical intersection (CI) coupled with the twisting motion of the central C-C bond. The S(1)-S(0) energy gap of the keto form became sufficiently small at the torsion angle of 60°, and the corresponding CI point was found at 90°. Since a minor role of the proximity effect was indicated experimentally and theoretically, the observed emission enhancement of the HPIP crystals was ascribed to the following two factors: (1) suppression of efficient radiationless decay via the CI by fixing the torsion angle at the nearly coplanar conformation of the molecules in the crystals and (2) inhibition of excimer formation resulting from the lower excited level of the S(1)-keto state compared to the S(0)-S(1) excitation energy in the enol form. However, the fluorescence color difference between the two crystal polymorphs having slightly different torsion angles was not successfully reproduced, even at the MS-CASPT2 level of theory.

  10. Structure of the Receptor-Binding Carboxy-Terminal Domain of the Bacteriophage T5 L-Shaped Tail Fibre with and without Its Intra-Molecular Chaperone

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    Carmela Garcia-Doval

    2015-12-01

    Full Text Available Bacteriophage T5, a Siphovirus belonging to the order Caudovirales, has a flexible, three-fold symmetric tail, to which three L-shaped fibres are attached. These fibres recognize oligo-mannose units on the bacterial cell surface prior to infection and are composed of homotrimers of the pb1 protein. Pb1 has 1396 amino acids, of which the carboxy-terminal 133 residues form a trimeric intra-molecular chaperone that is auto-proteolyzed after correct folding. The structure of a trimer of residues 970–1263 was determined by single anomalous dispersion phasing using incorporated selenomethionine residues and refined at 2.3 Å resolution using crystals grown from native, methionine-containing, protein. The protein inhibits phage infection by competition. The phage-distal receptor-binding domain resembles a bullet, with the walls formed by partially intertwined beta-sheets, conferring stability to the structure. The fold of the domain is novel and the topology unique to the pb1 structure. A site-directed mutant (Ser1264 to Ala, in which auto-proteolysis is impeded, was also produced, crystallized and its 2.5 Å structure solved by molecular replacement. The additional chaperone domain (residues 1263–1396 consists of a central trimeric alpha-helical coiled-coil flanked by a mixed alpha-beta domain. Three long beta-hairpin tentacles, one from each chaperone monomer, extend into long curved grooves of the bullet-shaped domain. The chaperone-containing mutant did not inhibit infection by competition.

  11. Molecular eigenstate spectroscopy: Application to the intramolecular dynamics of some polyatomic molecules in the 3000 to 7000 cm{sup {minus}1} region

    Energy Technology Data Exchange (ETDEWEB)

    Perry, D.S. [Univ. of Akron, OH (United States)

    1993-12-01

    Intramolecular vibrational redistribution (IVR) appears to be a universal property of polyatomic molecules in energy regions where the vibrational density of states is greater than about 5 to 30 states per cm{sup {minus}1}. Interest in IVR stems from its central importance to the spectroscopy, photochemistry, and reaction kinetics of these molecules. A bright state, {var_phi}{sub s}, which may be a C-H stretching vibration, carries the oscillator strength from the ground state. This bright state may mix with bath rotational-vibrational levels to form a clump of molecular eigenstates, each of which carries a portion of the oscillator strength from the ground state. In this work the authors explicitly resolve transitions to each of these molecular eigenstates. Detailed information about the nature of IVR is contained in the frequencies and intensities of the observed discrete transitions. The primary goal of this research is to probe the coupling mechanisms by which IVR takes place. The most fundamental distinction to be made is between anharmonic coupling which is independent of molecular rotation and rotationally-mediated coupling. The authors are also interested in the rate at which IVR takes place. Measurements are strictly in the frequency domain but information is obtained about the decay of the zero order state, {var_phi}{sub s}, which could be prepared in a hypothetical experiment as a coherent excitation of the clump of molecular eigenstates. As the coherent superposition dephases, the energy would flow from the initially prepared mode into nearby overtones and combinations of lower frequency vibrational modes. The decay of the initially prepared mode is related to a pure sequence infrared absorption spectrum by a Fourier transform.

  12. Antioxidant Profile of <em>Trifolium pratenseem> L.

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    Heidy Schwartsova

    2012-09-01

    Full Text Available In order to examine the antioxidant properties of five different extracts of <em>Trifolium pratenseem> L. (Leguminosae leaves, various assays which measure free radical scavenging ability were carried out: 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, superoxide anion and nitric oxide radical scavenger capacity tests and lipid peroxidation assay. In all of the tests, only the H2O and (to some extent the EtOAc extracts showed a potent antioxidant effect compared with BHT and BHA, well-known synthetic antioxidants. In addition, <em>in vivo em>experiments were conducted with antioxidant systems (activities of GSHPx, GSHR, Px, CAT, XOD, GSH content and intensity of LPx in liver homogenate and blood of mice after their treatment with extracts of <em>T. pratenseem> leaves, or in combination with CCl4. Besides, in the extracts examined the total phenolic and flavonoid amounts were also determined, together with presence of the selected flavonoids: quercetin, luteolin, apigenin, naringenin and kaempferol, which were studied using a HPLC-DAD technique. HPLC-DAD analysis showed a noticeable content of natural products according to which the examined <em>Trifolium pratenseem> species could well be regarded as a promising new source of bioactive natural compounds, which can be used both as a food supplement and a remedy.

  13. Proximate Composition, Nutritional Attributes and Mineral Composition of <em>Peperomia> <em>pellucida> L. (Ketumpangan Air Grown in Malaysia

    Directory of Open Access Journals (Sweden)

    Maznah Ismail

    2012-09-01

    Full Text Available This study presents the proximate and mineral composition of <em>Peperomia> <em>pellucida> L., an underexploited weed plant in Malaysia. Proximate analysis was performed using standard AOAC methods and mineral contents were determined using atomic absorption spectrometry. The results indicated <em>Peperomia> <em>pellucida> to be rich in crude protein, carbohydrate and total ash contents. The high amount of total ash (31.22% suggests a high-value mineral composition comprising potassium, calcium and iron as the main elements. The present study inferred that <em>Peperomia> <em>pellucida> would serve as a good source of protein and energy as well as micronutrients in the form of a leafy vegetable for human consumption.

  14. Sade em Lacan

    OpenAIRE

    Riaviz, Eduardo

    2000-01-01

    Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Esta dissertação analisa o lugar do Marquês de Sade no ensino de Lacan. Começamos por reconstruir a recepção de Sade pela vanguarda francesa, particularmente no movimento surrealista e nos seus dissidentes. Em seguida, acompanhamos as modificações do lugar de Sade na obra de Lacan. Para isto nos orientamos nos seis paradigmas do gozo através dos quais J.-A. Miller ordena a doutrina lacaniana...

  15. Branqueamento em dentes endodonciados

    OpenAIRE

    Melício, Joianne Sandrine Lopes

    2014-01-01

    Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Medicina Dentária Uma vez que a procura pela estética dentária vem aumentando significativamente, houve necessidade de procurar alternativas para a recuperação da coloração natural dos dentes quando esta é perdida por inúmeros fatores. O Branqueamento dentário, entre outras técnicas, tornou-se uma possibilidade para restaurar a perda da cor e tonalida...

  16. Quedas em idosos institucionalizados

    OpenAIRE

    Julia Emiko Fleming Uchida; Sheila de Melo Borges

    2014-01-01

    O objetivo do presente estudo foi verificar a frequência de quedas em idosos institucionalizados, bem como descrever os fatores de risco para quedas dessa população. As informações foram obtidas por meio de análise de prontuários, de entrevistas e pelos testes Timed Up and Go, Short Physical Performance Battery, Mini-exame do Estado Mental, Medida de Independência Funcional e Escala de Depressão Geriátrica-15. A frequência de quedas foi de 22,2% e verificou-se que os fatores de risco são freq...

  17. Flashes em Circuito

    Directory of Open Access Journals (Sweden)

    Ivete Lara Camargos Walty

    2002-12-01

    Full Text Available Reflexão sobre o papel da narrativa urbana no tratamento do tema da exclusão social, tendo como ponto de partida uma leitura do livro Passaporte, de Fernando Bonassi, que envolve a discussão do próprio gênero, a partir, sobretudo, da teoria do conto de Ricardo Piglia e de sua retomada das Seis propostas para o próximo milênio, de Ítalo Calvino, em artigo recente.

  18. Effects of <em>Citrus aurantiumem> (Bitter Orange Fruit Extracts and <em>p>-Synephrine on Metabolic Fluxes in the Rat Liver

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    Rosane Marina Peralta

    2012-05-01

    Full Text Available The fruit extracts of <em>Citrus aurantiumem> (bitter orange are traditionally used as weight-loss products and as appetite supressants. An important fruit component is <em>p>-synephrine, which is structurally similar to the adrenergic agents. Weight-loss and adrenergic actions are always related to metabolic changes and this work was designed to investigate a possible action of the <em>C. aurantiumem> extract on liver metabolism. The isolated perfused rat liver was used to measure catabolic and anabolic pathways, including oxygen uptake and perfusion pressure. The <em>C. aurantiumem> extract and <em>p>-synephrine increased glycogenolysis, glycolysis, oxygen uptake and perfusion pressure. These changes were partly sensitive to a- and b-adrenergic antagonists. <em>p>-Synephrine (200 mM produced an increase in glucose output that was only 15% smaller than the increment caused by the extract containing 196 mM <em>p>-synephrine. At low concentrations the <em>C. aurantiumem> extract tended to increase gluconeogenesis, but at high concentrations it was inhibitory, opposite to what happened with <em>p>-synephrine. The action of the <em>C. aurantiumem> extract on liver metabolism is similar to the well known actions of adrenergic agents and can be partly attributed to its content in <em>p>-synephrine. Many of these actions are catabolic and compatible with the weight-loss effects usually attributed to <em>C. aurantiumem>.

  19. Identification and Characterization of a <em>Bursaphelenchus xylophilusem> (Aphelenchida: Aphelenchoididae Thermotolerance-Related Gene: <em>Bx-HSP90em>

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    Danlei Li

    2012-07-01

    Full Text Available Temperatures directly influence the distribution and intensity of pine wilt disease caused by the pine wood nematode, <em>Bursaphelenchus xylophilusem>. To date, however, little is known about the causation and mechanism of this influence. The molecular chaperone HSP90 is a key component that contributes to survival in the abiotic stress response. In this study, we investigated the relationship between the survival of <em>B. xylophilusem> and the functionality of the HSP90 gene<em>.> <em>Bx-HSP90 em>was cloned from a suppression subtractive hybridization library. <em>In situem> mRNA hybridization showed that <em>Bx-HSP90em> was constitutively expressed in response to all of the temperatures tested, and RT-PCR indicated that all of the temperatures could induce <em>Bx-HSP90 em>transcription, with the highest transcript level detected at 30 °C. The suppression of the <em>Bx-HSP90em> transcript by RNA interference led to a 25% reduction in the number of nematodes at 30 °C after 44 h. Sharp declines in the survival of the RNAi-treated nematodes were observed after 8 days at 25 °C, 48 h at 30 °C and 24 h at 35 °C. Both heat shock and the knockdown of <em>Bx-HSP90 em>hindered the growth of the <em>B. xylophilusem> populations. The results indicate that <em>Bx-HSP90em> is essential for the survival of <em>B. xylophilusem>, confirming the thermoregulatory function of the gene, and delineate the timeframe and temperature range within which the gene function occurs.

  20. Chemical Composition, Antimicrobial and Antitumor Activities of the Essential Oils and Crude Extracts of<em> Euphorbiaem>> macrorrhizaem>

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    Haji Akber Aisa

    2012-05-01

    Full Text Available The present study aimed to examine the chemical composition and biological activity of essential oils extracted from <em>Euphorbia macrorrhizaem> collected from Northwest China. The major constituents of the essential oils of aerial parts and roots of <em>E. macrorrhizaem> are acorenone B (16.72% and 25.80%, (+-cycloisosativene (14.94% and 12.40%, 3a-hydroxy-5b-androstane (10.62% and 5.52%, copaene (7.37% and 6.29%, l-calamenene (4.13% and 4.65% and β-cedrene (8.40% and 7.98%, respectively. The minor components of them are thymene, γ-terpinene, thymecamphor, α-cedrene, zingiberene, trans-caryophyllene, β-chamigrene, curcumene, pentadecane, (−-α-muurolene, cuparene, γ-cadinene, (<em>Z>-3-heptadecene, 1,3,7,7-tetramethyl-2-oxabicyclo(4.4.0dec-5-en-4-one, hexahydrofarnesyl acetone, γ-elixene and palmitinic acid. The antimicrobial and antitumor activitiy of the <em>E. macrorrhizaem> essential oil against <em>Staphyloccocus aureusem>, <em>Escherichia coliem>, <em>Canidia Albicansem> and Caco-2 cells were evaluated. Among all the tested microorganisms and Caco-2 cells, the essential oils showed the strongest inhibitory effect on <em>Staphyloccocus aureus em>(MIC = 2.8 μg/mL and Caco-2 cell (IC50 = 11.86 μg/mL, whereas no effect on <em>Escherichia coliem> and <em>Candida em>albicans>. The data of this study suggested that the <em>E. macrorrhizaem> essential oils have great potential as a natural medicine for microbial infections and cancers.

  1. Further Insights on the Carotenoid Profile of the Echinoderm <em>Marthasteria>s glacialisem> L.

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    Natércia Teixeira

    2012-07-01

    Full Text Available In this study, the carotenoid profile of the echinoderm <em>Marthasterias glacialisem> L. was established using HPLC-DAD-APCI-MS/MS equipped with a C30 column. This approach rendered the identification of 20 compounds, eight of them reported for the first time in this marine organism. Differentiation of carotenoid isomers was also achieved.

  2. O insight em psiquiatria

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    Ana Margarida P. Cardoso

    2008-12-01

    Full Text Available O sinal de que algo está a acontecer contribui para que o paciente reconheça que alguma coisa de estranho se está a passar consigo. Este reconhecimento faz com que o sujeito possa desempenhar uma função activa e seja um elemento colaborante do seu processo de recuperação. Cada doença apresenta, contudo, diferentes sintomas, uma vez que cada doença psiquiátrica consiste em diferentes perturbações com diversos efeitos sobre o funcionamento mental. Desta maneira, o fenómeno do insight que é registado em cada doença é diferente e expressa-se sob diferentes formas, não somente devido às manifestações clínicas da doença mas também devido às características individuais do sujeito.

  3. Antibioticos profilaticos em neurocirurgia

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    Reynaldo A. Brandt

    1979-03-01

    Full Text Available O índice de infecções pós-operatórias em pacientes neuro-cirúrgicos que receberam antibióticos profiláticos neste período foi comparado com o de pacientes que não receberam antibióticos. Infecções ocorreram em proporções significativamente maiores nos pacientes que receberam antibióticos, particularmente naqueles com afecções intracranianas graves; estas infecções foram graves e fatais na maioria dos casos. A administração de antibióticos profiláticos nestes pacientes não só foi incapaz de prevenir o aparecimento de infecções pós-operatórias, como aparentemente favoreceu o seu desenvolvimento. Tal se deveu, provavelmente, à destruição do equilíbrio microbiano no organismo, favorecendo o desenvolvimento de germes patogênicos e resistentes aos antibióticos usuais

  4. Mulheres em movimento

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    Carneiro Sueli

    2003-01-01

    Full Text Available ESSE artigo busca demarcar a trajetória de luta das mulheres negras brasileiras no interior do movimento feminista nacional. Trata-se de colocar em questão a perspectiva feminista clássica fundada numa concepção universalista de mulher, que tem o seu paradigma na mulher branca ocidental, o que obscurece a percepção das múltiplas contradições intragênero e entre gêneros que a racialidade aporta. Dessas contradições, impõem-se para as mulheres negras a sua afirmação como um novo sujeito político, portador de uma nova agenda, esta resultante de uma identidade específica na qual se articulam as variáveis de gênero, raça e classe, colocando novos e mais complexos desafios para realização da eqüidade de gênero e raça em nossa sociedade.

  5. Competing intramolecular N-H⋯O=C hydrogen bonds and extended intermolecular network in 1-(4-chlorobenzoyl)-3-(2-methyl-4-oxopentan-2-yl) thiourea analyzed by experimental and theoretical methods

    Energy Technology Data Exchange (ETDEWEB)

    Saeed, Aamer, E-mail: aamersaeed@yahoo.com [Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Khurshid, Asma [Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Jasinski, Jerry P. [Department of Chemistry, Keene State College, 229 Main Street Keene, NH 03435-2001 (United States); Pozzi, C. Gustavo; Fantoni, Adolfo C. [Instituto de Física La Plata, Departamento de Física, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 49 y 115, La Plata, Buenos Aires (Argentina); Erben, Mauricio F., E-mail: erben@quimica.unlp.edu.ar [CEQUINOR (UNLP, CONICET-CCT La Plata), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962, (1900) La Plata, Buenos Aires (Argentina)

    2014-03-18

    Highlights: • Two distinct N-H⋯O=C intramolecular competing hydrogen bonds are feasible in the title molecule. • Crystal structures and vibrational properties were determined. • The C=O and C=S double bonds of the acyl-thiourea group are mutually oriented in opposite directions. • A strong hyperconjugative lpO1 → σ{sup ∗}(N2-H) remote interaction was detected. • Topological analysis reveals a Cl⋯N interaction playing a relevant role in crystal packing. - Abstract: The synthesis of a novel 1-acyl-thiourea species (C{sub 14}H{sub 17}N{sub 2}O{sub 2}SCl), has been tailored in such a way that two distinct N-H⋯O=C intramolecular competing hydrogen bonds are feasible. The X-ray structure analysis as well as the vibrational (FT-IR and FT-Raman) data reveal that the S conformation is preferred, with the C=O and C=S bonds of the acyl-thiourea group pointing in opposite directions. The preference for the intramolecular N-H⋯O=C hydrogen bond within the -C(O)NHC(S)NH- core is confirmed. The Natural Bond Orbital and the Atom in Molecule approaches demonstrate that a strong hyperconjugative lpO → σ{sup ∗}(N-H) remote interaction between the acyl and the thioamide N-H groups is responsible for the stabilization of the S conformation. Intermolecular interactions have been characterized in the periodic system electron density and the topological analysis reveals the presence of an extended intermolecular network in the crystal, including a Cl⋯N interaction playing a relevant role in crystal packing.

  6. The Effect of Neighboring Methionine Residue on Tyrosine Nitration & Oxidation in Peptides Treated with MPO, H2O2, & NO2- or Peroxynitrite and Bicarbonate: Role of Intramolecular Electron-Transfer Mechanism?

    Science.gov (United States)

    Zhang, Hao; Zielonka, Jacek; Sikora, Adam; Joseph, Joy; Xu, Yingkai; Kalyanaraman, B.

    2009-01-01

    Recent reports suggest that intramolecular electron-transfer reactions can profoundly affect the site and specificity of tyrosyl nitration and oxidation in peptides and proteins. Here we investigated the effects of methionine on tyrosyl nitration and oxidation induced by myeloperoxidase (MPO), H2O2 and NO2- and peroxynitrite (ONOO-) or ONOO- and bicarbonate (HCO3-) in model peptides, tyrosylmethionine (YM), tyrosylphenylalanine (YF) and tyrosine. Nitration and oxidation products of these peptides were analysed by HPLC with UV/Vis and fluorescence detection, and mass spectrometry; radical intermediates were identified by electron paramagnetic resonance (EPR)-spin-trapping. We have previously shown (Zhang et al., J. Biol. Chem. (2005) 280, 40684-40698) that oxidation and nitration of tyrosyl residue was inhibited in tyrosylcysteine(YC)-type peptides as compared to free tyrosine. Here we show that methionine, another sulfur-containing amino acid, does not inhibit nitration and oxidation of a neighboring tyrosine residue in the presence of ONOO- (or ONOOCO2-) or MPO/H2O2/NO2- system. Nitration of tyrosyl residue in YM was actually stimulated under the conditions of in situ generation of ONOO- (formed by reaction of superoxide with nitric oxide during SIN-1 decomposition), as compared to YF, YC and tyrosine. The dramatic variations in tyrosyl nitration profiles caused by methionine and cysteine residues have been attributed to differences in the direction of intramolecular electron transfer mechanism in these peptides. Further confirmation of HPLC data analysis was obtained by steady-state radiolysis and photolysis experiments. Potential implications of the intramolecular electron-transfer mechanism in mediating selective nitration of protein tyrosyl groups are discussed. PMID:19056332

  7. Identified EM Earthquake Precursors

    Science.gov (United States)

    Jones, Kenneth, II; Saxton, Patrick

    2014-05-01

    Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for

  8. A democracia em Cuba

    Directory of Open Access Journals (Sweden)

    Julio César Guanche Zaldívar

    2011-01-01

    Full Text Available O triunfo revolucionário de 1959 consagrou em Cuba um novo conceito de democracia, com o intuito de garantir o acesso à vida política ativa de grandes setores da população, antes excluídos. Para isso, foi desenvolvida uma política de inclusão social com caráter universal. A prática política popular deixou as riquezas do país em mãos da população carente e gerou uma grande mobilidade social, fato que foi central para o aumento da participação popular. O contexto de agressão imperialista e o próprio desenvolvimento do processo produziram a consolidação de noções que limitaram a participação popular: o apogeu da burocracia, a compreensão da unidade como unanimidade e o seguimento, em certa medida, de correntes do marxismo soviético. Os desafios atuais para aprofundar a democracia em Cuba se apresentam em três planos: socializar o poder, promover a sociodiversidade e desenvolver a ideologia revolucionária.El triunfo revolucionario de 1959 consagró en Cuba un nuevo concepto de democracia, basado en garantizar acceso a la vida política activa a grandes sectores poblacionales, antes excluidos de ella. Para ello desarrolló una política de inclusión social con carácter universal. La práctica política popular puso las riquezas del país en manos de los desposeídos y generó gran movilidad social, hecho que resultó clave para el aumento de la participación popular. El contexto de agresión imperialista y el propio desarrollo del proceso produjo el afianzamiento de nociones que limitaron la participación popular: el auge de la burocracia, la comprensión de la unidad como unanimidad y el seguimiento, en parte, de corrientes del marxismo soviético. Los desafíos actuales se presentan en tres planos para profundizar la democracia en Cuba: socializar el poder, promover la sociodiversidad y desarrollar la ideología revolucionaria.The revolutionary triumph of 1959 established in Cuba a new concept of democracy, one that

  9. Construction of the 1,2-dialkenylcyclohexane framework via Ireland-Claisen rearrangement and intramolecular Barbier reaction: application to the synthesis of (±)-Geijerone and a diastereoisomeric mixture with its 5-epimer.

    Science.gov (United States)

    Liang, Dawei; Gao, Nana; Liu, Wei; Dong, Jinhua

    2014-01-20

    The elemene-type terpenoids, which possess various biological activities, contain a syn- or anti-1,2-dialkenylcyclohexane framework. An efficient synthetic route to the syn- and anti-1,2-dialkenylcyclohexane core and its application in the synthesis of (±)-geijerone and its diastereomer is reported. Construction of the syn- and anti-1,2-dialkenyl moiety was achieved via Ireland-Claisen rearrangement of the (E)-allylic ester, and the cyclohexanone moiety was derived from the iodoaldehyde via intramolecular Barbier reaction. The synthetic strategy allows rapid access to various epimers and analogues of elemene-type products.

  10. Construction of the 1,2-Dialkenylcyclohexane Framework via Ireland-Claisen Rearrangement and Intramolecular Barbier Reaction: Application to the Synthesis of (±-Geijerone and a Diastereoisomeric Mixture with Its 5-Epimer

    Directory of Open Access Journals (Sweden)

    Dawei Liang

    2014-01-01

    Full Text Available The elemene-type terpenoids, which possess various biological activities, contain a syn- or anti-1,2-dialkenylcyclohexane framework. An efficient synthetic route to the syn- and anti-1,2-dialkenylcyclohexane core and its application in the synthesis of (±-geijerone and its diastereomer is reported. Construction of the syn- and anti-1,2-dialkenyl moiety was achieved via Ireland-Claisen rearrangement of the (E-allylic ester, and the cyclohexanone moiety was derived from the iodoaldehyde via intramolecular Barbier reaction. The synthetic strategy allows rapid access to various epimers and analogues of elemene-type products.

  11. Four Novel Cellulose Synthase (CESA Genes from <em>Birch> (<em>Betula platyphylla em>Suk. Involved in Primary and Secondary Cell Wall Biosynthesis

    Directory of Open Access Journals (Sweden)

    Xuemei Liu

    2012-09-01

    Full Text Available Cellulose synthase (CESA, which is an essential catalyst for the generation of plant cell wall biomass, is mainly encoded by the <em>CesA> gene family that contains ten or more members. In this study; four full-length cDNAs encoding CESA were isolated from<em> Betula platyphyllaem> Suk., which is an important timber species, using RT-PCR combined with the RACE method and were named as <em>BplCesA3em>, <em>−4em>,> −7 em>and> −8em>. These deduced CESAs contained the same typical domains and regions as their <em>Arabidopsis> homologs. The cDNA lengths differed among these four genes, as did the locations of the various protein domains inferred from the deduced amino acid sequences, which shared amino acid sequence identities ranging from only 63.8% to 70.5%. Real-time RT-PCR showed that all four <em>BplCesAs> were expressed at different levels in diverse tissues. Results indicated that BplCESA8 might be involved in secondary cell wall biosynthesis and floral development. BplCESA3 appeared in a unique expression pattern and was possibly involved in primary cell wall biosynthesis and seed development; it might also be related to the homogalacturonan synthesis. BplCESA7 and BplCESA4 may be related to the formation of a cellulose synthase complex and participate mainly in secondary cell wall biosynthesis. The extremely low expression abundance of the four BplCESAs in mature pollen suggested very little involvement of them in mature pollen formation in <em>Betula>. The distinct expression pattern of the four <em>BplCesAs> suggested they might participate in developments of various tissues and that they are possibly controlled by distinct mechanisms in <em>Betula.>

  12. Influence of intramolecular f-f interactions on nuclear spin driven quantum tunneling of magnetizations in quadruple-decker phthalocyanine complexes containing two terbium or dysprosium magnetic centers.

    Science.gov (United States)

    Fukuda, Takamitsu; Matsumura, Kazuya; Ishikawa, Naoto

    2013-10-10

    Nuclear spin driven quantum tunneling of magnetization (QTM) phenomena, which arise from admixture of more than two orthogonal electronic spin wave functions through the couplings with those of the nuclear spins, are one of the important magnetic relaxation processes in lanthanide single molecule magnets (SMMs) in the low temperature range. Although recent experimental studies have indicated that the presence of the intramolecular f-f interactions affects their magnetic relaxation processes, little attention has been given to their mechanisms and, to the best of our knowledge, no rational theoretical models have been proposed for the interpretations of how the nuclear spin driven QTMs are influenced by the f-f interactions. Since quadruple-decker phthalocyanine complexes with two terbium or dysprosium ions as the magnetic centers show moderate f-f interactions, these are appropriate to investigate the influence of the f-f interactions on the dynamic magnetic relaxation processes. In the present paper, a theoretical model including ligand field (LF) potentials, hyperfine, nuclear quadrupole, magnetic dipolar, and the Zeeman interactions has been constructed to understand the roles of the nuclear spins for the QTM processes, and the resultant Zeeman plots are obtained. The ac susceptibility measurements of the magnetically diluted quadruple-decker monoterbium and diterbium phthalocyanine complexes, [Tb-Y] and [Tb-Tb], have indicated that the presence of the f-f interactions suppresses the QTMs in the absence of the external magnetic field (H(dc)) being consistent with previous reports. On the contrary, the faster magnetic relaxation processes are observed for [Tb-Tb] than [Tb-Y] at H(dc) = 1000 Oe, clearly demonstrating that the QTMs are rather enhanced in the presence of the external magnetic field. Based on the calculated Zeeman diagrams, these observations can be attributed to the enhanced nuclear spin driven QTMs for [Tb-Tb]. At the H(dc) higher than 2000 Oe, the

  13. Selective Complexation of Cyanide and Fluoride Ions with Ammonium Boranes: A Theoretical Study on Sensing Mechanism Involving Intramolecular Charge Transfer and Configurational Changes.

    Science.gov (United States)

    Bhat, Haamid R; Jha, Prakash C

    2017-05-18

    The anion binding selectivity and the recognition mechanism of two isomeric boranes, namely, 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([p-(Mes 2 B)C 6 H 4 (NMe 3 )] + , 1, where "Mes" represents mesitylene and "Me" represents methyl) and 2-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([o-(Mes 2 B)C 6 H 4 (NMe 3 )] + , 2) has been investigated using density functional theory (DFT) and time dependent-density functional theory (TD-DFT) methods. Natural population analysis indicates that the central boron atoms in 1 and 2 are the most active centers for nucleophilic addition of anions. The negative magnitude of free energy changes (ΔG) reveals that out of CN - , F - , Cl - , Br - , NO 3 - , and HSO 4 - only the binding of CN - and F - with 1 and 2 is thermodynamically feasible and spontaneous. In addition, the calculated binding energies reveal that the CN - is showing lesser binding affinity than F - both with 1 and 2, while other ions, viz. NO 3 - , HSO 4 - , Br - , and Cl - , either do not bind at all or show very insignificant binding energy. The first excited states (S 1 ) of 1 and 2 are shown to be the local excited states with π → σ* transition by frontier molecular orbital analysis, whereas fourth excited states (S 4 ) of 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline cyanide ([p-(Mes 2 B)C 6 H 4 (NMe 3 )] CN, 1CN, the cyano form of 1) and 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline fluoride ([p-(Mes 2 B)C 6 H 4 (NMe 3 )] F, 1F, the fluoro form of 1) and fifth excited state (S 5 ) of 2-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline fluoride ([o-(Mes 2 B)C 6 H 4 (NMe 3 )] F, 2F, the fluoro form of 2) are charge separation states that are found to be responsible for the intramolecular charge transfer (ICT) process. The synergistic effect of ICT and partial configuration changes induce fluorescence quenching in 1CN, 1F, and 2F after a significant internal conversion (IC) from S 4 and

  14. NMR of proteins (4Fe-4S): structural properties and intramolecular electron transfer; RMN de proteines (4Fe-4S): proprietes structurales et transfert electronique intramoleculaire

    Energy Technology Data Exchange (ETDEWEB)

    Huber, J.G.

    1996-10-17

    NMR started to be applied to Fe-S proteins in the seventies. Its use has recently been enlarged as the problems arising from the paramagnetic polymetallic clusters ware overcome. Applications to [4Fe-4S] are presented herein. The information derived thereof deepens the understanding of the redox properties of these proteins which play a central role in the metabolism of bacterial cells. The secondary structure elements and the overall folding of Chromatium vinosum ferredoxin (Cv Fd) in solution have been established by NMR. The unique features of this sequence have been shown to fold as an {alpha} helix at the C-terminus and as a loop between two cysteines ligand of one cluster: these two parts localize in close proximity from one another. The interaction between nuclear and electronic spins is a source of additional structural information for (4Fe-AS] proteins. The conformation of the cysteine-ligands, as revealed by the Fe-(S{sub {gamma}}-C{sub {beta}}-H{sub {beta}})Cys dihedral angles, is related to the chemical shifts of the signals associated with the protons of these residues. The longitudinal relaxation times of the protons depend on their distance to the cluster. A quantitative relationship has been established and used to show that the solution structure of the high-potential ferredoxin from Cv differs significantly from the crystal structure around Phe-48. Both parameters (chemical shifts and longitudinal relaxation times) give also insight into the electronic and magnetic properties of the [4Fe-4S] clusters. The rate of intramolecular electron transfer between the two [4FE-4S] clusters of ferredoxins has been measured by NMR. It is far slower in the case of Cv Fd than for shorter ferredoxins. The difference may be associated with changes in the magnetic and/or electronic properties of one cluster. The strong paramagnetism of the [4Fe-4S] clusters, which originally limited the applicability of NMR to proteins containing these cofactors, has been proven

  15. Osteoporose em caprinos

    Directory of Open Access Journals (Sweden)

    Fábio B. Rosa

    2013-04-01

    Full Text Available Foi realizado um estudo de casos de osteoporose em caprinos provenientes de uma propriedade na área de abrangência do LPV-UFSM, determinando a epidemiologia, o quadro clínico-patológico e discutindo os prováveis mecanismos patogenéticos. Cinco cabras, fêmeas, SRD, de seis meses a seis anos de idade foram afetadas. As cabras eram mantidas em campo nativo, sem suplementação com ração e sob superlotação. Os principais sinais clínicos foram emagrecimento, dificuldade de locomoção e permanência em decúbito por longos períodos. As principais alterações macroscópicas nos ossos examinados foram vistas nas superfícies de corte e caracterizavam-se por depleção do osso esponjoso (porosidade e redução acentuada da espessura do osso cortical. Havia também marcada atrofia serosa da gordura da medula óssea. Microscopicamente, nas regiões avaliadas (úmero proximal, rádio distal, fêmur distal, tíbia proximal e corpos das vértebras lombares foi observada redução moderada a acentuada do número e da espessura das trabéculas ósseas nas epífises e metáfises dos ossos longos e nos corpos vertebrais. Os achados clínico-patológicos indicaram que a osteoporose observada provavelmente foi causada pela desnutrição. As alterações ósseas (diminuição no número e na espessura das trabéculas do osso esponjoso sugerem que ambos os mecanismos, má formação óssea e reabsorção óssea aumentada, contribuíram para a ocorrência de osteoporose nos caprinos deste estudo.

  16. Intramolecular electron transfer in laccases.

    Science.gov (United States)

    Farver, Ole; Wherland, Scot; Koroleva, Olga; Loginov, Dmitry S; Pecht, Israel

    2011-09-01

    Rate constants and activation parameters have been determined for the internal electron transfer from type 1 (T1) to type 3 (T3) copper ions in laccase from both the fungus Trametes hirsuta and the lacquer tree Rhus vernicifera, using the pulse radiolysis method. The rate constant at 298 K and the enthalpy and entropy of activation were 25 ± 1 s(-1), 39.7 ± 5.0 kJ·mol(-1) and -87 ± 9 J·mol(-1) ·K(-1) for the fungal enzyme and 1.1 ± 0.1 s(-1), 9.8 ± 0.2 kJ·mol(-1) and -211 ± 3 J·mol(-1) ·K(-1) for the tree enzyme. The initial reduction of the T1 site by pulse radiolytically produced radicals was direct in the case of T. hirsuta laccase, but occured indirectly via a disulfide radical in R. vernicifera. The equilibrium constant that characterizes the electron transfer from T1 to T3 copper ions was 0.4 for T. hirsuta laccase and 1.5 for R. vernicifera laccase, leading to full reduction of the T1 site occurring at 2.9 ± 0.2 electron equivalents for T. hirsuta and 4 electron equivalents for R. vernicifera laccase. These results were compared with each other and with those for the same process in other multicopper oxidases, ascorbate oxidase and Streptomyces coelicolor laccase, using available structural information and electron transfer theory. © 2011 The Authors Journal compilation © 2011 FEBS.

  17. Quedas em idosos institucionalizados

    Directory of Open Access Journals (Sweden)

    Julia Emiko Fleming Uchida

    2014-03-01

    Full Text Available O objetivo do presente estudo foi verificar a frequência de quedas em idosos institucionalizados, bem como descrever os fatores de risco para quedas dessa população. As informações foram obtidas por meio de análise de prontuários, de entrevistas e pelos testes Timed Up and Go, Short Physical Performance Battery, Mini-exame do Estado Mental, Medida de Independência Funcional e Escala de Depressão Geriátrica-15. A frequência de quedas foi de 22,2% e verificou-se que os fatores de risco são frequentes nessa população, mostrando, assim, um risco importante para quedas futuras. Palavras-chave: Saúde do Idoso Institucionalizado; Acidentes por quedas; Fatores de risco.

  18. INDICADORES EM SANEAMENTO

    OpenAIRE

    Costa, Samuel Alves Barbi; Côrtes, Larissa Silveira; Coelho Netto, Taiana; Freitas Junior, Moacyr Moreira de

    2016-01-01

    Este artigo se propõe a analisar a evolução dos prestadores de serviços de saneamento do estado de MinasGerais entre os anos de 2005 e 2010 com base nos indicadores do Sistema Nacional de Informações em Saneamento(SNIS). Foram definidos parâmetros técnicos para a análise dos indicadores, classificados os resultados como satisfatórios(verdes) ou insatisfatórios (vermelhos). Esta categorização atende a concepção da Regulação Sunshine, trazendo à tona omonitoramento do progresso das ações no set...

  19. O humano em Womanity

    OpenAIRE

    Silva, Dâmaris de Oliveira Batista da

    2012-01-01

    Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-Graduação em Psicologia. A cultura da comunicação transforma e cria uma nova forma urbana, a comunicação urbana que produzida é para nos capturar e envolver com maior intensidade nessa sociedade do consumo. Há na comunicação publicitária uma proposta ideológica, pois cada signo é dirigido a alguém e o diálogo é constituído pelo poder. Nossa inserção no mundo define e é d...

  20. Em favor da talassografia

    Directory of Open Access Journals (Sweden)

    Jean-Louis Boudou

    2001-01-01

    Full Text Available A Talassografia (“descrição do mar” interessa-sepelos impactos físicos, biológicos, ecológicos... culturais da violenta antropização dos ambientes costeiros (oceânicos e continentais, caracterizados pelaexigüidade, vulnerabilidade, fragilidade e plasticidade. Como o Brasil é um “país marítimo”, os geó-grafos (os talassógrafos brasileiros são convidadosa intensificar suas pesquisas nas áreas costeiras e acriar novas estruturas para divulgá-las: Revista, Encontros, Associação, Pós-Graduação... tudo em prolda talassografia.

  1. Imagem digital em movimento

    OpenAIRE

    Travisani, Tatiana Giovannone [UNESP

    2008-01-01

    Este trabalho reúne análises sobre as imagens digitais com questões estruturais e poéticas do movimento, fazendo um levantamento histórico e artístico desde os primeiros experimentos em cronofotografia, até as manifestações atuais, do universo digital, que incorporam o movimento como temática. A imagem digital tratada não é de cunho sintético, mas sim que passou por algum processo de captura analógica, por meio de câmeras, e após isso, foi digitalizada. A partir daí, a pesquisa reflete as tra...

  2. Mechanism of hydrogen peroxide dismutation by a dimanganese catalase mimic: dominant role of an intramolecular base on substrate binding affinity and rate acceleration.

    Science.gov (United States)

    Boelrijk, A E; Dismukes, G C

    2000-07-10

    substrate affinity (KM). By contrast, free (noncoordinating) bases in solution have no effect on catalysis, thus establishing intramolecular sites for both functional hydroxide anions. Solution structural studies indicate that the presence of 2-5 equiv of hydroxide in solution leads to formation of a bishydroxide species, [(L1,2)Mn2(mu 13-O2CCH3)(OH)2], which in the presence of air or oxygen auto-oxidizes to yield complex 6, a Mn2(III,III)(mu-O) species. Complex 6 oxidizes H2O2 to O2 without a kinetic lag phase and is implicated as the active form of the oxidized catalyst. A maximum increase by 240-fold in catalytic efficiency (kcat/KM = 700 s-1 M-1) is observed with the bishydroxide species versus the aquo complex 1, or only 800-fold less efficient than the enzyme. Deprotonation of the amine groups of the chelate ligand L was shown not to be involved in the hydroxide effects because identical results were obtained using the catalyst with tetrakis(N-ethylated)-L. Uncoupling of the Mn(II) spins by protonation of the alkoxyl bridge (LH) was observed to lower the catalase activity. Comparisons to other dimanganese complexes reveals that the Mn2(II,II)/Mn2(III,III) redox potential is not the determining factor in the catalase rate of these complexes. Rather, rate acceleration correlates with the availability of an intramolecular hydroxide for substrate deprotonation and with binding of the substrate at the bridging site between Mn ions in the reductive O-O bond cleavage step that forms water and complex 6.

  3. INFLUÊNCIA ESTOICA NA CONCEPÇÃO DE <em>STATUS> E <em>DICTUM> COMO <em> QUASI RES EM> (ὡσανεì τινά EM ABERLARDO STOIC INFLUENCE IN ABELARD'S CONCEPTION OF <em>STATUS> AND <em>DICTUM> AS <em>QUASI RESem> (ὡσανεì τινά.

    Directory of Open Access Journals (Sweden)

    Guy Hamelin

    2011-09-01

    Full Text Available Na sua obra, Pedro Abelardo (1079-1142 destaca duas noções metafísicas que fundamentam sua teoria lógica: o <em style="mso-bidi-font-style: normal;">statusem> e o <em style="mso-bidi-font-style: normal;">dictum propositionisem>, ao causar, respectivamente, a imposição (<em style="mso-bidi-font-style: normal;">impositioem> dos termos universais e o valor de verdade das proposições. Trata-se de expressões que se referem a naturezas ontológicas peculiares, na medida em que não são consideradas coisas (<em style="mso-bidi-font-style: normal;">resem>, mesmo que constituem causas. Todavia, também não são nada. Abelardo as chama de ‘quase coisas’ (<em style="mso-bidi-font-style: normal;">quasi resem>. No presente artigo, explicamos, primeiro, essas duas noções essenciais da lógica abelardiana, antes de tentar, em seguida, encontrar a fonte dessa metafísica particular. Em oposição a comentadores importantes da lógica de Abelardo, que estimam que haja uma forte influência platônica sobre essa concepção específica, defendemos antes, com apoio de textos significativos e de acordo com o nominalismo abelardiano, que a maior ascendência sobre a metafísica do nosso autor é a do estoicismo, sobretudo, antigo.In his work, Peter Abelard (1079-1142 highlights two metaphysical notions, which sustain his logical theory: the <em>status> and the <em>dictum propositionisem>, causing respectively both the imposition (<em>impositio> of universal terms and the thuth-value of propositions. Both expressions refer to peculiar ontological natures, in so far as they are not considered things (<em>res>, even if they constitute causes. Nevertheless, neither are they ‘nothing’. Abelard calls them ‘quasi-things’ (<em>quasi resem>. In the present article, we expound first these two essential notions of Abelardian logic before then trying to find the source of this particular metaphysics. Contrary to some important

  4. Aggiornamento sulla distribuzione di <em>Talpa europaeaem> in Umbria

    Directory of Open Access Journals (Sweden)

    A.M. Paci

    2003-10-01

    Full Text Available L?Umbria, in ragione della sua posizione centrale nella Penisola, appare particolarmente interessante dal punto di vista biogeografico. Per quanto riguarda le talpe, ad esempio, sono presenti tutti i <em>taxa> italiani ma, essendo ancora scarse e frammentarie le informazioni sulla loro distribuzione regionale, viene intanto aggiornato lo status di <em>T. europaeaem> con la sintesi di alcuni dati inediti raccolti nella provincia di Perugia: <em>Zoccolanti>, Città di Castello, 300 m as pa, 13-IV-2001; <em>Monte Maggioreem>, Città di Castello, 605 m bc pa vu, 13-VI-2003; <em>San Secondoem>, Città di Castello, 260 m ci pb vf, 3-VI-1995 / 9-V-2001; <em>Lugnano>, Città di Castello, 260 m ci pb vf, 25-XI-1992; <em>Niccone>, Umbertide, 250 m ce pb vf 14-VI-2003; <em>Pietralunga>, 505 m as pa, 19-IV-2002; <em>Monte Cuccoem>, Sigillo, 1050 m bc bm vu, 5-V-2003 <em>Castiglione>, Gubbio, 840 m bc pa, 30-V-1999; <em>Schifanoia>, Valfabbrica, 350 m bc pa, 30-V-2000; <em>Oscano>, Perugia, 470 m bc pa, 2002; <em>Monte Melinoem>, Magione, 225 m ci ps vt, 19-I-2001; <em>Sant?Arcangelo>, Magione; 260 m zu ps vt, IV-2002; <em>Città della Pieveem>, 500 m as pa, 29-VI-2001 (bc bosco di caducifoglie, ce colture estensive, ci colture intensive, as area suburbana, zu zona umida, pa piano bioclimatico altocollinare, pb piano bioclimatico bassocollinare, bm piano bioclimatico bassomontano, ps piano bioclimatico collinare submediterraneo, vu variante umida, vf variante fredda, vt variante temperata. In letteratura la specie viene segnalata anche nel Comune di Assisi. In due località dell?Umbria nord-orientale ? Pietralunga e Monte Cucco - <em>T. europaeaem> è risultata in parapatria con <em>T. caecaem> mentre, da recentissima bibliografia, entrerebbe in contatto con <em>T. romanaem> nella fascia centrale della regione. Contemporaneamente si è creduto opportuno riportare notizie relative ad individui marchigiani

  5. Preferencia alimenticia del ácaro depredador <em>Balaustium> sp. en condiciones controladas

    Directory of Open Access Journals (Sweden)

    Muñoz Karen

    2009-04-01

    Full Text Available

    Se evaluó la preferencia de presas de <em>Balaustium> sp., enemigo natural de diferentes artrópodos plaga, y el cual es nativo de la Sabana de Bogotá. En unidades experimentales construidas con foliolos de plantas de rosa se colocaron independientemente individuos de <em>Balaustium> sp. y se registró el número de presas consumidas. De esta manera se determinó la preferencia de los tres estados móviles del ácaro depredador <em>Balaustium> sp. por diferentes edades de tres presas. Las especies y edades de las presas estudiadas fueron: huevos, ninfas y adultos de <em>Trialeurodes vaporariorumem>, huevos, ninfas y adultos de <em>Tetranychus urticaeem>, y larvas de primer y segundo instar y adultos de <em>Frankliniella occidentalisem>. Los estados menos desarrollados fueron preferidos, aunque se observó que los adultos del depredador tienen gran habilidad para consumir adultos de <em>T. vaporariorumem>. La presa preferida por las larvas de <em>Balaustium> sp. fue los huevos de <em>T. urticaeem> con una proporción de consumo de 0,54 de los huevos que se ofrecieron de esta presa; las deutoninfas del depredador eligieron huevos de <em>T. vaporariorumem> (0,537 o de <em>T. urticaeem> (0,497 y los adultos de <em>Balaustium> sp. prefrieron los huevos de <em>T. vaporariorumem> (0,588.

  6. Busca de estruturas em grandes escalas em altos redshifts

    Science.gov (United States)

    Boris, N. V.; Sodré, L., Jr.; Cypriano, E.

    2003-08-01

    A busca por estruturas em grandes escalas (aglomerados de galáxias, por exemplo) é um ativo tópico de pesquisas hoje em dia, pois a detecção de um único aglomerado em altos redshifts pode por vínculos fortes sobre os modelos cosmológicos. Neste projeto estamos fazendo uma busca de estruturas distantes em campos contendo pares de quasares próximos entre si em z Â3 0.9. Os pares de quasares foram extraídos do catálogo de Véron-Cetty & Véron (2001) e estão sendo observados com os telescópios: 2,2m da University of Hawaii (UH), 2,5m do Observatório de Las Campanas e com o GEMINI. Apresentamos aqui a análise preliminar de um par de quasares observado nos filtros i'(7800 Å) e z'(9500 Å) com o GEMINI. A cor (i'-z') mostrou-se útil para detectar objetos "early-type" em redshifts menores que 1.1. No estudo do par 131046+0006/J131055+0008, com redshift ~ 0.9, o uso deste método possibilitou a detecção de sete objetos candidatos a galáxias "early-type". Num mapa da distribuição projetada dos objetos para 22 escala. Um outro argumento em favor dessa hipótese é que eles obedecem uma relação do tipo Kormendy (raio equivalente X brilho superficial dentro desse raio), como a apresentada pelas galáxias elípticas em z = 0.

  7. Synthesis of 1,2,3-Triazole Derivatives and <em>in Vitroem> Antifungal Evaluation on <em>Candida> Strains

    Directory of Open Access Journals (Sweden)

    Almir G. Wanderley

    2012-05-01

    Full Text Available 1,2,3-Triazoles have been extensively studied as compounds possessing important biological activities. In this work, we describe the synthesis of ten 2-(1-aryl-1<em>H>-1,2,3-triazol-4-ylpropan-2-ols via copper catalyzed azide alkyne cycloaddition (CuAAc or <em>click chemistryem>. Next the<em> in vitroem> antifungal activity of these ten compounds was evaluated using the microdilution broth method against 42 isolates of four different <em>Candida> species. Among all tested compounds, the halogen substituted triazole 2-[1-(4-chlorophenyl-1<em>H>-(1,2,3triazol-4-yl]propan-2-ol, revealed the best antifungal profile, showing that further modifications could be done in the structure to obtain a better drug candidate in the future.

  8. Extraction of Dihydroquercetin<em> em>from <em>Larix gmeliniem>i> em>with Ultrasound-Assisted and Microwave-Assisted Alternant Digestion

    Directory of Open Access Journals (Sweden)

    Yuangang Zu

    2012-07-01

    Full Text Available An ultrasound and microwave assisted alternant extraction method (UMAE was applied for extracting dihydroquercetin (DHQ from <em>Larix gmeliniem>i> wood. This investigation was conducted using 60% ethanol as solvent, 1:12 solid to liquid ratio, and 3 h soaking time. The optimum treatment time was ultrasound 40 min, microwave 20 min, respectively, and the extraction was performed once. Under the optimized conditions, satisfactory extraction yield of the target analyte was obtained. Relative to ultrasound-assisted or microwave-assisted method, the proposed approach provides higher extraction yield. The effect of DHQ of different concentrations and synthetic antioxidants on oxidative stability in soy bean oil stored for 20 days at different temperatures (25 °C and 60 °C was compared. DHQ was more effective in restraining soy bean oil oxidation, and a dose-response relationship was observed. The antioxidant activity of DHQ was a little stronger than that of BHA and BHT. Soy bean oil supplemented with 0.08 mg/g DHQ exhibited favorable antioxidant effects and is preferable for effectively avoiding oxidation. The <em>L. gmeliniiem> wood samples before and after extraction were characterized by scanning electron microscopy. The results showed that the UMAE method is a simple and efficient technique for sample preparation.

  9. Molluscicidal Activity of Methomyl and Cardenolide Extracts from <em>Calotropis proceraem> and <em>Adenium> <em>arabicum> Against the Land Snail <em>Monacha cantianaem>

    Directory of Open Access Journals (Sweden)

    Alaa Bayoumi

    2012-05-01

    Full Text Available In this work, we have evaluated the molluscicidal activity of two cardenolide extracts from <em>Adenium arabicumem> Balf f. [the benzene (B and methanol (M extracts], one cardenolide extract from <em>Calotropis proceraem> (Aiton W.T. Aiton (extract C, and methomyl against the harmful land snail <em>Monacha cantianaem> (Montagu. The contact LD50 values for the above mentioned plant extracts were 12.62, 34.63, and 34.35 mg·kg−1 of body weight, respectively, while the LD50 for methomyl was 116.62 mg·kg−1, that is, the plant extracts were 9.24, 3.37, and 3.4 times more toxic than methomyl. In addition, a simple colorimetric method, based on Kedde reagent, was modified to determine cardenolide concentrations in plant extracts. Thin layer chromatography analysis (TLC showed several cardiac glycosidal compounds in each plant extract. The results proved that cardiac glycosides are promising candidate compounds that could be used to control land snails, or exploited to develop new, effective, and environmentally friendly molluscicides.

  10. Conjuntivite em animais de companhia

    OpenAIRE

    Gonçalves, Mariana Inês Pereira Coelho

    2015-01-01

    Dissertação de Mestrado Integrado em Medicina Veterinária, Ciências Veterinárias A conjuntivite é a doença ocular mais frequentemente diagnosticada em Medicina Veterinária, tanto em cães como em gatos. O facto de a conjuntiva ser uma membrana mucosa tão exposta a agentes externos faz com que esteja bastante suscetível a sofrer lesões, com consequente inflamação. Nesta dissertação abordam-se os diferentes tipos de conjuntivite, que são classificados de acordo com a sua etiologia. No Hospita...

  11. Regional Suppression of <em>Bactrocera> Fruit Flies (Diptera: Tephritidae in the Pacific through Biological Control and Prospects for Future Introductions into Other Areas of the World

    Directory of Open Access Journals (Sweden)

    Roger I. Vargas

    2012-08-01

    Full Text Available <em>Bactrocera> fruit fly species are economically important throughout the Pacific. The USDA, ARS U.S. Pacific Basin Agricultural Research Center has been a world leader in promoting biological control of <em>Bactrocera> spp. that includes classical, augmentative, conservation and IPM approaches. In Hawaii, establishment of <em>Bactrocera> <em>cucurbitae> (Coquillett in 1895 resulted in the introduction of the most successful parasitoid, <em>Psyttalia> <em>fletcheri> (Silvestri; similarly, establishment of <em>Bactrocera> <em>dorsalis> (Hendel in 1945 resulted in the introduction of 32 natural enemies of which <em>Fopius> <em>arisanus> (Sonan, <em>Diachasmimorpha> <em>longicaudata> (Ashmead and <em>Fopius> <em>vandenboschi> (Fullaway were most successful. Hawaii has also been a source of parasitoids for fruit fly control throughout the Pacific region including Australia, Pacific Island Nations, Central and South America, not only for <em>Bactrocera> spp. but also for <em>Ceratitis> and <em>Anastrepha> spp. Most recently, in 2002, <em>F.> <em>arisanus> was introduced into French Polynesia where <em>B.> <em>dorsalis> had invaded in 1996. Establishment of <em>D.> <em>longicaudata> into the new world has been important to augmentative biological control releases against <em>Anastrepha> spp. With the rapid expansion of airline travel and global trade there has been an alarming spread of <em>Bactrocera> spp. into new areas of the world (<em>i.e.>, South America and Africa. Results of studies in Hawaii and French Polynesia, support parasitoid introductions into South America and Africa, where <em>B.> <em>carambolae> and <em>B.> <em>invadens>, respectively, have become established. In addition, <em>P.> <em>fletcheri> is a candidate for biological control of <em>B.> <em>cucurbitae> in Africa. We review past and more

  12. CATETERES EM TERAPIA INTENSIVA

    Directory of Open Access Journals (Sweden)

    Carolina de Deus Lisboa

    2014-01-01

    Full Text Available Pesquisa com os objetivos de identificar falhas na administração de medicamentos por sondas e caracterizar a interrupção ou não da nutrição no caso de medicamentos que exigem jejum relativo. Estudo epidemiológico, transversal, observacional, numa terapia intensiva, com amostra de 350 doses administradas por 56 técnicos de enfermagem. Resultados mostraram que não houve pausa entre a administração do medicamento e a infusão de dieta enteral em 116 (33,14% doses de medicamentos que necessitavam de jejum relativo, entre os quais captopril, varfarina sódica, levotiroxina sódica, digoxina e fenitoína sódica. A irrigação das sondas não ocorreu na maioria dos casos (94,28%. Conclui-se que é possível que os medicamentos citados tenham tido sua biodisponibilidade sérica reduzida, comprometendo sua eficácia terapêutica e que a falta da prática de irrigar sondas com água estéril, antes de administrar medicamentos, configura-se como a ausência de um cuidado específico fundamental para evitar a obstrução das mesmas.

  13. Hemoptises em jovens adultos

    Directory of Open Access Journals (Sweden)

    Herbert Peter Know

    2008-07-01

    Full Text Available Resumo: A hemoptise é uma queixa médica frequente que pode requerer broncoscopia para o seu diagnóstico e tratamento. Não está completamente esclarecido quais são os doentes que beneficiam da broncoscopia como abordagem precoce. Está estabelecido que os jovens adultos com hemoptises são doentes de baixo risco, quando comparados com velhos; contudo, não há muitos trabalhos sobre o interesse da broncoscopia na abordagem deste grupo etário.Os autores resolveram avaliar, retrospectivamente, todos os doentes submetidos a broncoscopia por hemoptises, caracterizando a apresentação clínica e a avaliação diagnóstica dos jovens adultos (18 aos 40 anos, incluindo a utilidade diagnóstica da broncoscopia.Satisfizeram os critérios de inclusão 18 doentes. Na broncoscopia realizada nos doentes com hemoptises que apresentavam radiografia do tórax e T AC do tórax normal não foram identificadas quaisquer alterações endobrônquicas.Os autores, perante estes resultados preconizam que os doentes jovens adultos com hemoptises, com radiografias do tórax e TAC do tórax normais, não necessitam da avaliação broncoscópica inicial, devendo ser seguidos em follow-up clínico apertado.

  14. Activity-Guided Isolation of Antioxidant Compounds from <em>Rhizophora apiculataem>

    Directory of Open Access Journals (Sweden)

    Hongbin Xiao

    2012-09-01

    Full Text Available <em>Rhizophora apiculataem> (<em>R. apiculataem> contains an abundance of biologically active compounds due its special salt-tolerant living surroundings. In this study, the total phenolic content and antioxidant activities of various extract and fractions of stem of <em>R. apiculataem> were investigated. Results indicated that butanol fraction possesses the highest total phenolic content (181.84 mg/g GAE/g dry extract with strongest antioxidant abilities. Following <em>in vitroem> antioxidant activity-guided phytochemical separation procedures, lyoniresinol-3α-<em>O>-β-arabinopyranoside (1, lyoniresinol-3α-<em>O>-β-rhamnoside (2, and afzelechin-3-<em>O>-L-rhamno-pyranoside (3 were separated from the butanol fraction. These compounds showed more noticeable antioxidant activity than a BHT standard in the DPPH, ABTS and hydroxyl radical scavenging assays. HPLC analysis results showed that among different plant parts, the highest content of 13 was located in the bark (0.068%, 0.066% and 0.011%, respectively. The results imply that the <em>R. apiculataem> might be a potential source of natural antioxidants and 13 are antioxidant ingredients in <em>R. apiculataem>.

  15. Tratamento da dor em queimados

    Directory of Open Access Journals (Sweden)

    Rodrigo José Alencar de Castro

    2013-02-01

    Full Text Available JUSTIFICATIVA E OBJETIVOS: Apesar dos avanços, ainda é observado manejo analgésico inadequado dos pacientes com queimaduras. O objetivo desta revisão foi coletar dados sobre tratamento da dor em queimados. CONTEÚDO: Foi feita revisão sobre os mecanismos de dor, avaliação do paciente com queimadura e o tratamento farmacológico e não farmacológico. CONCLUSÕES: O manejo da dor em pacientes vítimas de queimaduras ainda é um desafio por parte da equipe multiprofissional. A avaliação frequente e contínua da resposta apresentada pelo paciente é muito importante, tendo em vista os vários momentos por que passa o paciente internado em decorrência de uma queimadura, além de uma terapêutica combinada com medicações analgésicas e medidas não farmacológicas. Entender a complexidade de alterações fisiopatológicas, psicológicas e bioquímicas apresentadas por um paciente em tratamento de queimadura é o primeiro passo para alcançar o sucesso no seu manejo analgésico.

  16. Imagens de um Sujeito em Devir: Autorretrato em Rede

    Directory of Open Access Journals (Sweden)

    Camila Leite Araujo

    2012-06-01

    Full Text Available Este artigo se prope a discutir o fenmeno da circulao das fotografias pessoais em plataformas virtuais e o surgimento de uma possvel nova esttica do cotidiano e do efmero. Assim, iniciamos com um quadro conceitual sobre as possibilidades da fotografia digital referentes s imagens do cotidiano e apresentamos uma anlise sobre as particularidades estticas do autorretrato contemporneo, um processo de criao que envolve conceitos como fabulao, performance e o efmero, em um espao de interao com as ferramentas de comunicao na comunidade do Flickr.

  17. Alcaloides pirrolizidinicos em borboletas Ithomiinal : alguns aspectos em ecologia quimica

    OpenAIRE

    Jose Roberto Trigo

    1993-01-01

    Resumo: Alcalóides pirrolizidínicos (PAs) são ésteres de 1-metilhidroxilpirrolizidínas, sendo o aminoálcool chamado de base necina e a parte ácida de ácidos nécicos. Geralmente ocorrem em forma de monoésteres, diésteres abertos ou cíclicos, podendo apresentar uma insaturação no anel (PAs insaturados) ou não (PAs saturados). Estas substâncias apresentam mais de 200 estruturas isoladas de plantas, ocorrendo principalmente em Senecio, Eupatorium (Asteraceae), Crotalaria (Fabaceae) e Heliotropium...

  18. The influence of intramolecular coordination on the aggregation of sodium phenolate complexes. X-ray structures of [NaOC6H4(CH2NMe2)-2]6 and [Na(OC6H2(CH2NMe2)2-2,6-Me-4)(HOC6H2NMe2)2-2,6-Me-4)]2

    NARCIS (Netherlands)

    Koten, G. van; Hogerheide, M.P.; Ringelberg, S.N.; Janssen, M.D.; Boersma, J.; Spek, A.L.

    1996-01-01

    The structural characterization of two new sodium phenolate complexes, containing ortho-amino substituents, enables the influence of intramolecular coordination on the aggregation of sodium phenolate complexes to be determined. Crystals of hexameric [NaOC6H4(CH2NMe2)-2]6 (1a) are monoclinic, space

  19. Consumo ecologicamente consciente em Portugal

    OpenAIRE

    Schoor, Maria Adelaide Oliveira van

    2013-01-01

    Dissertação apresentada à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências da Comunicação, ramo de Marketing e Publicidade Esta Dissertação de Mestrado faz uma análise ao consumo ecologicamente consciente em Portugal. Tento em conta as questões ambientais que tem vindo a ser debatidas nas últimas décadas, o desenvolvimento de estratégias de produção e promoção de produtos e serviços mais ecológicos tem vindo a aumentar significativamente. A...

  20. Objetos mediadores em museus

    Directory of Open Access Journals (Sweden)

    Inês Ferreira

    2015-02-01

    Full Text Available Um museu participativo incentiva a que a experiência da visita seja criativa e pessoal. Facilita a participação biográfica do visitante - com a sua experiência, conhecimento e interesses. Muitas exposições, porém, não promovem esse envolvimento pessoal. Neste artigo apresentamos uma revisão da literatura que indicia que a mediação com objetos mediadores facilita o envolvimento pessoal, a construção de conhecimento e a criatividade. O problema teórico que colocamos é se os museus mais tradicionais se podem abrir à participação e, neste contexto, o nosso objetivo é perceber que papel podem ter os objetos mediadores nesse processo. Discutimos o recurso a objetos mediadores como forma de adicionar múltiplos níveis de relação e modos de ver, potencial que consideramos subaproveitado em muitos museus. Começamos por apresentar o museu como espaço potencialmente participativo, que convida a um envolvimento ativo e crítico – ativo, porque o visitante é desafiado a fazer coisas; crítico, porque é estimulado a pensar, optar, discutir e refletir. Discutimos depois diferentes formas de usar objetos mediadores para incentivar o visitante a um envolvimento com os artefactos, recorrendo à memória, experiência, conhecimento e sentimentos. A participação biográfica potencia o cruzamento entre o mundo interior do visitante e os artefactos e conteúdos do museu. Esse espaço de cruzamento - inbetween - é o espaço da construção de conhecimento. Apresentamos diversas formas de um museu, mesmo não sendo interativo, se tornar mais criativo e participativo, o que pode contribuir para uma mudança nas práticas dos museus, nomeadamente na montagem e remodelação de exposições permanentes.

  1. Rural Emergency Medical Services (EMS) and Trauma

    Science.gov (United States)

    ... Guide Rural Health Topics & States Topics View more Rural Emergency Medical Services (EMS) and Trauma Emergency medical ... injuries treated in emergency departments? How can a rural EMS unit find funding for major equipment, such ...

  2. EM Mortar Technology Development for Indirect Fire

    National Research Council Canada - National Science Library

    Turman, B. N; Kaye, R. J; Crawford, M; Magnotti, P; Nguyen, D; van Reuth, E; Johnson, S. A; Poppe, R

    2006-01-01

    The DARPA Electromagnetic (EM) Mortar Laboratory Demonstration Program is a focused development and demonstration effort for an EM gun system for vehicle-based, non-line-of-sight, artillery applications...

  3. Trombo flutuante em veia femoral

    Directory of Open Access Journals (Sweden)

    Matheus Bertanha

    2017-12-01

    Full Text Available Resumo O trombo venoso flutuante em veia femoral é um tipo de trombo com alto potencial de embolização pulmonar. Entretanto, ainda é controversa a conduta mais apropriada nesses casos. Tratamentos clínicos com anticoagulantes ou fibrinolíticos e trombectomias abertas ou por meio de dispositivos endovasculares vêm sendo empregados ainda sem um critério de indicação bem definido. Apresentamos três casos clínicos de trombos flutuantes em veia femoral, de etiologias distintas, cujos tratamentos e respectivas evoluções serão discutidos.

  4. Eletrons interagentes em bilhares magneticos

    OpenAIRE

    Luis Gregorio G. de V. Dias da Silva

    2002-01-01

    Resumo: Consideramos o problema de dois elétrons confinados em um Bilhar quadrado, interagindo por um potencial repulsivo de alcance finito do tipo Yukawa e sujeitos a um campo magnético ortogonal. Calculamos o espectro de energia do sistema para singletos e tripletos de spin em todas as classes de simetria como função da intensidade e alcance da interação e do campo magnético. Mostramos que a natureza de curto alcance da interação suprime a formação de estados fundamentais "Moléculas de Wign...

  5. Factores de risco em implantologia

    OpenAIRE

    Sousa, Inês Silveira e Luz Nunes de

    2015-01-01

    A Implantologia tem ganho popularidade na medicina dentária pelos resultados previsíveis em reabilitações de áreas edêntulas, permitindo minimizar as consequências funcionais, fonéticas e estéticas que advém da perda de dentes através de uma solução fixa que satizfaz os pacientes. Esta é uma revisão da literatura existente sobre factores de risco, fracassos e complicações inerentes ao tratamento com implantes dentários. Categorizam-se os factores de risco em implantologia co...

  6. Efeito da enxertia em mandioca

    OpenAIRE

    Bomfim, Nayra Nascimento

    2011-01-01

    Enxertos de duas espécies silvestres (M. glaziovii e M. fortalezensis) sobre M. esculenta, mandioca, foram estudados morfologicamente, anatomicamente e citogeneticamente e a fim de se avaliar possíveis efeitos devido à interação entre enxerto e porta-enxerto. Foram feitas análises anatômicas das raízes dos porta-enxertos UnB 201 e UnB 122 (variedades de M. esculenta), em comparação com as variedades não enxertadas. Analisou-se a meiose em enxerto da espécie M. glaziovii que apresentava morfol...

  7. Adaptabilidade e estabilidade em aveia em ambientes estratificados

    Directory of Open Access Journals (Sweden)

    Bertan Ivandro

    2005-01-01

    Full Text Available Vinte cultivares de aveia (Avena sativa L. foram avaliados para rendimento de grãos nas safras agrícolas de 2001 e 2002 em nove locais dos estados do Paraná, Rio Grande do Sul e São Paulo, com o objetivo de avaliar as estimativas dos componentes de adaptabilidade e estabilidade do rendimento de grãos em ambientes favoráveis e desfavoráveis em presença e ausência de aplicação de fungicida. Foi empregada a metodologia de EBERHART & RUSSELL (1966. A presença de significância para anos, genótipos, fungicidas e locais, indicou comportamento diferencial de genótipos frente às variações de ambiente e a aplicação de fungicida, nas condições de ambientes favoráveis e desfavoráveis. A aplicação de fungicida e o favorecimento do ambiente de cultivo afetaram intensamente os parâmetros de adaptabilidade (b1 e estabilidade (s²d i, indicando que estas estimativas devam ser realizadas em ambientes estratificados, apesar de nenhuma constituição genética ter evidenciado o biótipo ideal, conforme preconizado pelo modelo adotado.

  8. EM Algorithm and Stochastic Control in Economics

    OpenAIRE

    Kou, Steven; Peng, Xianhua; Xu, Xingbo

    2016-01-01

    Generalising the idea of the classical EM algorithm that is widely used for computing maximum likelihood estimates, we propose an EM-Control (EM-C) algorithm for solving multi-period finite time horizon stochastic control problems. The new algorithm sequentially updates the control policies in each time period using Monte Carlo simulation in a forward-backward manner; in other words, the algorithm goes forward in simulation and backward in optimization in each iteration. Similar to the EM alg...

  9. Evaluation of Antioxidant Activities of Aqueous Extracts and Fractionation of Different Parts of <em>Elsholtzia em>ciliata>

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    Yuangang Zu

    2012-05-01

    Full Text Available The aim of this study was to investigate the antioxidant and free-radical scavenging activity of extract and fractions from various parts of <em>Elsholtzia ciliataem>. The inflorescences, leaves, stems and roots of <em>E. ciliataem> were extracted separately and two phenolic component enrichment methods: ethyl acetate-water liquid-liquid extraction and macroporous resin adsorption-desorption, were adopted in this study. The antioxidant activities of water extracts and fractions of <em>E. ciliataem> were examined using different assay model systems <em>in vitroem>. The fraction root E (purified by HPD300 macroporous resin exhibited the highest total phenolics content (497.2 ± 24.9 mg GAE/g, accompanied with the highest antioxidant activity against various antioxidant systems <em>in vitroem> compared to other fractions. On the basis of the results obtained, <em>E. ciliataem> extracts can be used potentially as a ready accessible and valuable bioactive source of natural antioxidants.

  10. A Novel Apoptosis Correlated Molecule: Expression and Characterization of Protein Latcripin-1 from <em>Lentinula em>edodes> C91–3

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    Min Huang

    2012-05-01

    Full Text Available An apoptosis correlated molecule—protein Latcripin-1 of <em>Lentinula> edodesem> C91-3—was expressed and characterized in <em>Pichia pastorisem> GS115. The total RNA was obtained from <em>Lentinula edodesem> C91–3. According to the transcriptome, the full-length gene of Latcripin-1 was isolated with 3'-Full Rapid Amplification of cDNA Ends (RACE and 5'-Full RACE methods. The full-length gene was inserted into the secretory expression vector pPIC9K. The protein Latcripin-1 was expressed in <em>Pichia pastorisem> GS115 and analyzed by Sodium Dodecylsulfonate Polyacrylate Gel Electrophoresis (SDS-PAGE and Western blot. The Western blot showed that the protein was expressed successfully. The biological function of protein Latcripin-1 on A549 cells was studied with flow cytometry and the 3-(4,5-Dimethylthiazol-2-yl-2,5-Diphenyl-tetrazolium Bromide (MTT method. The toxic effect of protein Latcripin-1 was detected with the MTT method by co-culturing the characterized protein with chick embryo fibroblasts. The MTT assay results showed that there was a great difference between protein Latcripin-1 groups and the control group (<em>p em>< 0.05. There was no toxic effect of the characterized protein on chick embryo fibroblasts. The flow cytometry showed that there was a significant difference between the protein groups of interest and the control group according to apoptosis function (<em>p em>< 0.05. At the same time, cell ultrastructure observed by transmission electron microscopy supported the results of flow cytometry. The work demonstrates that protein Latcripin-1 can induce apoptosis of human lung cancer cells A549 and brings new insights into and advantages to finding anti-tumor proteins.

  11. Low Diversity Bacterial Community and the Trapping Activity of Metabolites from Cultivable Bacteria Species in the Female Reproductive System of the Oriental Fruit Fly, <em>Bactrocera dorsalisem> Hendel (Diptera: Tephritidae

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    Hongyu Zhang

    2012-05-01

    Full Text Available Our goal was to identify the bacteria inhabiting the reproductive system of the female oriental fruit fly, <em>Bactrocera dorsalisem> (Hendel, and evaluate the chemotaxis of <em>B>. <em>dorsalis> to the metabolites produced by the bacteria. Based on 16S rRNA-based polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE, 18 operational taxonomic units (OTUs were assigned to the five bacterial classes <em>Betaproteobacteria>, <em>Alphaproteobacteria>, <em>Gammaproteobacteria>, <em>Bacilli> and <em>Actinobacteria>. Nine OTUs were assigned to <em>Gammaproteobacteria>, which was the most highly represented class. <em>Enterobacteriaceae> constituted the dominant family, and within this family, three genera and five species were identified, including <em>Enterobacter sakazakiiem>, <em>Klebsiella> <em>oxytoca>, <em>Klebsiella> <em>pneumoniae,> Raoultellaem> <em>terrigena em>and <em>Enterobacter> <em>amnigenus>. In this set, the first two species were the dominant components, and the latter three species were the minor ones. Finally, we found that the metabolites produced by <em>R.> terrigenaem>, <em>K. oxytocaem> and <em>K.> pneumoniae em>were attractive to the <em>B.> dorsalisem> adults, and in field studies, <em>B.> dorsalisem> adults were most attracted to <em>K.> oxytocaem>. Collectively, our results suggest that the female reproductive system plays an important role in the transfer of enterobacteria from the gut to fruit. Our data may prompt the development of a female-targeted population control strategy for this fly.

  12. Rodent hosts of <em>Maritrema> sp. (Digenea, Microphallidae in Sardinia Island

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    Juan Carlos Casanova

    2003-10-01

    Full Text Available Prospections on helminth fauna of rodents were carried out in the Cedrino river (Eastern of Sardinia island. Twelve <em>Rattus rattusem> (L., 1758 and eight <em>Mus domesticusem> (Schwarz & Schwarz, 1943 were captured by Sherman traps. Parasitological study revealed in <em>R. rattusem> the presence of an intestinal helminth belonging to the genus <em>Maritrema> (family Microphallidae. The transmission of this Digenetic Trematode among vertebrates involves the participation of aquatic invertebrate organisms, molluscs and crustacea, acting as intermediate hosts. Dissection of 117 individuals of the Amphipod Crustacea <em>Gammarus italicusem>, collected in the same biotope, allowed the detection of encysted metacercariae. These larvae constitute the infesting stage of the parasite for vertebrates, acting these as definitive hosts ingesting parasitized crustacea as preys. Adults of <em>Maritrema> sp. were also obtained experimentally in the laboratory mice (<em>Mus domesticusem> CD1 strain. These were infested by inoculating them, using gastric probe, metacercarial cysts isolated from <em>G. italicusem>. Post-infection mice dissection was performed at different intervals of time getting adults in various maturity stages. Experimental facts confirm that <em>Maritrema> sp., as it occurs in other trematodes, do not present strict specificity to the definitive host, being able to develop as well in <em>Mus>. In nature, the presence or absence of this digenean in mammals species will be dependent of host ethological factors, mainly related to feeding habitats. This study was partially supported by the ?Comissionat per Recerca i Universitats de la Generalitat de Catalunya? 2001SGR00088.

  13. Antifungal Activity, Toxicity and Chemical Composition of the Essential Oil of <em>Coriandrum sativumem> L. Fruits

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    Erika H. S. Brito

    2012-07-01

    Full Text Available The aims of this study were to test the antifungal activity, toxicity and chemical composition of essential oil from <em>C. sativumem> L. fruits. The essential oil, obtained by hydro-distillation, was analyzed by gas chromatography/mass spectroscopy. Linalool was the main constituent (58.22%. The oil was considered bioactive, showing an LC50 value of 23 µg/mL in the <em>Artemia salinaem> lethality test. The antifungal activity was evaluated against <em>Microsporum canisem> and <em>Candida> spp. by the agar-well diffusion method and the minimum inhibitory concentration (MIC and the minimum fungicidal concentration (MFC were established by the broth microdilution method. The essential oil induced growth inhibition zones of 28 ± 5.42 and 9.25 ± 0.5 for <em>M. canisem> and <em>Candida> spp. respectively. The MICs and MFCs for <em>M. canisem> strains ranged from 78 to 620 and 150 to 1,250 µg/mL, and the MICs and MFCs for <em>Candida> spp strains ranged from 310 to 620 and 620 to 1,250 µg/mL, respectively. <em>C. sativumem> essential oil is active<em> in vitroem> against <em>M. canis em>and> Candidaem> spp. demonstrating good antifungal activity.

  14. Bens virtuais em social games

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    Rebeca Recuero Rebs

    Full Text Available O artigo foca a compreensão dos significados da aquisição de bens virtuais por usuários de social games. Conjuntamente, busca estimular a reflexão sobre os usos e as identificações que motivam os jogadores à compra destes bens. Com base em autores que trabalham com a produção e as simbologias de bens integrados às práticas de consumo da sociedade, o trabalho apresenta dados de uma observação participante por sete meses em dez social games e de questionários aplicados em 140 jogadores. Por fim, propõe-se uma classificação de bens virtuais em social games baseada nos dados adquiridos e na dinâmica social do jogo. Os resultados apontam para a circulação de significações atribuídas aos bens virtuais a partir de contextos pré-estabelecidos pelos social games e pelas origens culturais de seus jogadores, atuando possivelmente na edificação e/ou manifestação identitária dos sujeitos no ciberespaço.

  15. Allometric and Isometric variations in the Italian <em>Apodemus sylvaticusem> and <em>Apodemus flavicollisem> with respect to the conditions of allopatry and sympatry / Variazioni allometriche e isometriche in <em>Apodemus sylvaticusem> e <em>Apodemus flavicollisem> italiani, rispetto alle condizioni di allopatria e simpatria

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    Giovanni Amori

    1986-12-01

    Full Text Available Abstract In Italy there are two species of <em>Apodemus> (<em>Sylvaemus>: <em>Apodemus sylvaticusem> on the mainland and the main island, and <em>Apodemus flavicollisem> only on the mainland. The trend of some morphometric characters of the skull (incisive foramen length - FI; interorbital breadth = IO; length of palatal bridge = PP; upper alveolar length = $M^1M^3$ was analized and some theoretical models verified for <em>A. sylvaticusem>. If one considers the sympatric population of <em>A. sylvaticusem> and <em>A. flavicollisem> simultaneously the characters PP, IO and $M^1M^3$ appear significantly isometric being directly correlated ($P leq O.O1$, while FI character results allometric with respect to the previous ones, as expected. If one considers the sympatric populations of each of the species separately, the scenario is different. For <em>A. sylvaticusem> only PP and $M^1M^3$ are isometric ($P leq 0.05$. For <em>A. flavicollisem> only $M^1M^3$ and FI appear to be correlated, although not as significantly as for <em>A. sylvaticusem> ($P le 0.05$; one tail. The insular populations of <em>A. sylvaticusem> do not show significant correlations, except for FI and $M^1M^3$ ($P le 0.05$. On the contrary, considering all populations, sympatric and allopatric, of <em>A. sylvaticusem> at the same time are significant correlations ($P le 0.05$ in all combinations of characters, except for those involving the IO. We suggest that the isometric relations in sympatric assemblages are confined within a morphological range available to the genus <em>Apodemus>. In such a space, the two species are split in two different and innerly homogeneous distributions. We found no evidence to confirm the niche variation hypothesis. On the contrary, the variability expressed as SO or CV's appears higher in the sympatric populations than in the allopatric ones, for three of the four characters, confirming previous results

  16. First sign of <em>Clethrionomys glareolusem> in the Po valley plain / Prima segnalazione in Pianura Padana di <em>Clethrionomys glareolusem>

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    Luis Nieder

    1987-07-01

    Full Text Available Abstract The presence of <em>Clethrionomys glareolusem> (Schreber, 1790 populations is reported in the Po valley, formerly considered outside the distribution area of the species. An initial series of captures was made in the high-water area of the Po near S. Nazzaro (Monticelli d'Ongina - PC following with research was extended along the river's banks in Emilia both upstream and downstream. The search for this species was carried out by analysing food pellets relating to <em>Strix alucoem>, <em>Tyto albaem> e <em>Athene noctuaem>, thought to be among the most common predators of these intensive herbaceous and arboreal agricultural biocoenosis. The information we gathered was integrated with other Authors' unpublished and bibliographical data. The presence of <em>C. glareolusem> was noted in habitats quite different from the expected ones. Many of the problems raised by the presence of this species in "islands" along the main body of the Po river and its tributaries, and by its presumed absence from particulary suitable environments such as the Carrega woods, the Ticino park and Mesola wood must still be resolved. Riassunto Viene segnalata la presenza di popolazioni di <em>Clethrionomys glareolusem> (Schreber 1790 nella pianura Padana precedentemente considerata al di fuori dell'areale della specie. A partire da una prima serie di catture nell'area golenale del Po presso S. Nazzaro (Monticelli d'Ongina - PC, si è successivamente proceduto ad allargare l'area di ricerca lungo l'argine emiliano del Po, sia a monte sia a valle. La ricerca di questa specie è avvenuta tramite l'analisi di boli alimentari relativi a <em>Strix alucoem>, <em>Tyto albaem> e <em>Athene noctuaem>, ritenuti tra i più comuni predatori di queste biocenosi agricole intensive erbacee ed arboree. I dati da noi raccolti sono stati integrati con quelli bibliografici e inediti di altri Autori. È stata riscontrata la presenza

  17. Parasitic zoonoses: survey in foxes (<em>Vulpes vulpesem> in the northern Apennines / Zoonosi parassitarie: indagini in volpi (<em>Vulpes vulpesem> dell'Appennino settentrionale

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    Vittorio Guberti

    1991-07-01

    Full Text Available Abstract A parasitological survey on 153 foxes was carried out in the northern Apennines, during the period 1984-1987. The following parasites were identified: <em>Toxocara canisem> (46.4%, <em>Taenia> sp. (17%, <em>Uncinaria stenocephalaem> (11.8%, <em>Mesocestoides lineatusem> (11.1%, <em>Ancylostoma caninumem> (3.9%, <em>Taenia hydatigenaem> (3.3%, <em>Trichuris vulpisem> (3.3%, <em>Dipylidium caninumem> (2.6%, <em>Taenia crassicepsem> (2%. All foxes were negative for <em>Trichinella> sp. A statistical analysis was performed to evaluate differences in the parasitic fauna according to the sex and age classes of the hosts. The role that the fox could have as a reservoir of helminthic zoonoses is discussed. The results are compared with those of similar studies carried out in Italy. Riassunto Nel periodo 1984-1987 è stata condotta un'indagine parassitologica su 153 volpi abbattute nell'Appennino romagnolo. Sono stati reperiti i seguenti parassiti: <em>Toxocara canisem> (46,4%, <em>Taenia> sp. (17%, <em>Uncinaria stenocephalaem> (11,8%, <em>Mesocestoides lineatusem> (11,1%, <em>Ancylostoma caninumem> (3,9%, <em>Taenia hydatigenaem> (3,3%, <em>Trichuris vulpisem> (3,3%, <em>Dipylidium caninumem> (2,6%, <em>Taenia crassicepsem> (2%. Tutte le volpi esaminate sono risultate negative per <em>Trichinella> sp. È stata effettuata l'analisi statistica dei dati per evidenziare eventuali differenze della fauna parassitaria in relazione al sesso e all'età delle volpi. Sulla base dei dati ottenuti viene discussa l'importanza che la Volpe può assumere come serbatoio di zoonosi elmintiche. I risultati acquisiti sono inoltre comparati con quelli ottenuti in analoghe ricerche condotte in Italia.

  18. Cefaleia em salvas: aspectos clinicos e terapeuticos em 26 casos

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    Wilson Luiz Sanvito

    1980-12-01

    Full Text Available Vinte e seis casos de cefaléia-em-salvas são estudados do ponto de vista clínico e terapêutico. Nos aspectos clínicos são ressaltados a dramaticidade deste tipo de cefaléia, o nítido predomínio no sexo masculino, a média de idade dos pacientes, a presença de manifestações associadas e os fatores desencadeantes das crises nos períodos suscetíveis. Do ponto de vista terapêutico três esquemas medicamentosos foram utilizados: maleato de metisergida, prednisona e associação de ambas as drogas. Em 88,3% dos casos um resultado significativo foi alcançado, traduzido por melhora ou abolição das crises.

  19. Fatores de risco cardiovascular em alcoolistas em tratamento

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    Mayla Cardoso Fernandes Toffolo

    2013-06-01

    Full Text Available OBJETIVO: Avaliar a presença de fatores de risco cardiovascular, com ênfase na hipertensão e na adiposidade corporal, em alcoolistas abstinentes ou não abstinentes em tratamento. MÉTODO: Trata-se de um estudo transversal com 65 pacientes alcoolistas em tratamento no CAP-Sad. O grau de dependência do álcool foi avaliado pelo SADD (Short Alcohol Dependence Data e o uso de outras drogas, pelo ASSIST (Alcohol Smoking and Substance Involvement Screening Test. Foram avaliados o perfil bioquímico e o antropométrico dos usuários. RESULTADOS: Participaram do estudo 42 homens e 23 mulheres. A maioria dos participantes (67,74% apresentou dependência alcoólica grave, com uso de álcool associado principalmente a cigarro (66,15%. A média da circunferência da cintura (CC foi significativamente maior entre os abstinentes, em comparação aos não abstinentes (AB: 88,15 ± 15,95 x NA: 81,04 ± 9,86; p = 0,03. Pacientes abstinentes há mais tempo tiveram maior sobrepeso/obesidade e adiposidade abdominal (CC do que os não abstinentes e abstinentes recentes, com razão de chances de 5,25. Os abstinentes apresentaram razão de chances de 3,38 para %GC acima da média, independente do tempo de abstinência. CONCLUSÃO: Pacientes alcoolistas abstinentes apresentam mais sobrepeso/ obesidade, adiposidade corporal (%GC e abdominal (CC do que os não abstinentes. É importante o acompanhamento multiprofissional no tratamento de alcoolistas com abordagem para fatores de risco cardiovasculares, principalmente evitando o ganho de peso.

  20. Enfermagem em cardiologia baseada em evidência

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    Eneida Rejane Rabelo da Silva

    2007-10-01

    Full Text Available Neste artigo apresentamos, dentro do cenário cardiovascular, estudos recentes do nosso grupo. Buscando melhores evidências de enfermagem investigamos por meio de ensaios clínicos randomizados (ECR estratégias de educação e acompanhamento destes pacientes (pctes. O primeiro ECR avaliou o impacto da educação individual e da orientação em grupo no conhecimento sobre doença e autocuidado em pctes com insuficiência cardíaca (IC. No grupo intervenção, houve uma melhora do conhecimento dos cuidados essenciais (controle de sal e da ingesta hídrica, peso diário, realização de atividade física P=0,008, demonstrando que o atendimento em grupo é semelhante ao individual. No ambiente hospitalar, segundo ECR, comparamos o efeito da educação de enfermagem e seguimento telefônico após alta versus educação sem a monitorização por telefone. Demonstramos que intervenção educativa durante a internação melhora o conhecimento da doença, autocuidado e qualidade de vida (P

  1. Fadiga em idosos em tratamento quimioterápico

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    Thalyta Cristina Mansano-Schlosser

    2014-08-01

    Full Text Available Pesquisa com delineamento transversal, realizada de agosto a dezembro de 2010, que objetivou identificar a presença e intensidade da fadiga em 140 idosos (média de idade 69,8 anos, 52,1% do sexo feminino com diagnóstico de câncer, em tratamento quimioterápico ambulatorial. Utilizou-se um questionário para caracterização sociodemográfica e clínica e a Escala de Fadiga de Piper-revisada. Identificou-se a presença de fadiga em 60 idosos (42,9% e a causa atribuída foi o câncer (64,1%, a quimioterapia (32,8% e o tratamento (3,1%. Como fator de alívio, os idosos entrevistados relataram "dormir", "rezar" e "morrer", enquanto 45% deles disseram "não ter o que fazer", pois a fadiga não poderia ser aliviada. Espera-se que este estudo alerte os profissionais de enfermagem para a relevância da fadiga e os estimule a identificar e realizar intervenções de enfermagem que visem o adequado manejo desse sintoma no paciente idoso oncológico.

  2. <em>Ipomoea aquaticaem> Extract Shows Protective Action Against Thioacetamide-Induced Hepatotoxicity

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    A. Hamid A. Hadi

    2012-05-01

    Full Text Available In the Indian system of traditional medicine (Ayurveda it is recommended to consume <em>Ipomoea em>aquatica> to mitigate disorders like jaundice. In this study, the protective effects of ethanol extract of <em>I. aquaticaem> against liver damage were evaluated in thioacetamide (TAA-induced chronic hepatotoxicity in rats. There was no sign of toxicity in the acute toxicity study, in which Sprague-Dawley (SD rats were orally fed with <em>I. aquaticaem> (250 and 500 mg/kg for two months along with administration of TAA (i.p injection 200 mg/kg three times a week for two months. The results showed that the treatment of <em>I. aquaticaem> significantly lowered the TAA-induced serum levels of hepatic enzyme markers (ALP, ALT, AST, protein, albumin, bilirubin and prothrombin time. The hepatic content of activities and expressions SOD and CAT that were reduced by TAA were brought back to control levels by the plant extract supplement. Meanwhile, the rise in MDA level in the TAA receiving groups also were significantly reduced by <em>I. aquaticaem> treatment. Histopathology of hepatic tissues by H&E and Masson trichrome stains displayed that <em>I. aquaticaem> has reduced the incidence of liver lesions, including hepatic cells cloudy swelling, infiltration, hepatic necrosis, and fibrous connective tissue proliferation induced by TAA in rats. Therefore, the results of this study show that the protective effect of <em>I. aquaticaem> in TAA-induced liver damage might be contributed to its modulation on detoxification enzymes and its antioxidant and free radical scavenger effects. Moreover, it confirms a scientific basis for the traditional use of <em>I. aquaticaem> for the treatment of liver disorders.

  3. Phytochemical Composition, Antioxidant and Xanthine Oxidase Inhibitory Activities of <em>Amaranthus cruentusem> L. and <em>Amaranthus hybridusem> L. Extracts

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    Jeanne F. Millogo

    2012-06-01

    Full Text Available This paper describes a preliminary assessment of the nutraceutical value of <em>Amaranthus cruentus (A. cruentusem> and <em>Amaranthus hybridus (A. hybridusem>, two food plant species found in Burkina Faso. Hydroacetonic (HAE, methanolic (ME, and aqueous extracts (AE from the aerial parts were screened for <em>in vitroem> antioxidant and xanthine oxidase inhibitory activities. Phytochemical analyses revealed the presence of polyphenols, tannins, flavonoids, steroids, terpenoids, saponins and betalains. Hydroacetonic extracts have shown the most diversity for secondary metabolites. The TLC analyses of flavonoids from HAE extracts showed the presence of rutin and other unidentified compounds. The phenolic compound contents of the HAE, ME and AE extracts were determined using the Folin–Ciocalteu method and ranged from 7.55 to 10.18 mg Gallic acid equivalent GAE/100 mg. Tannins, flavonoids, and flavonols ranged from 2.83 to 10.17 mg tannic acid equivalent (TAE/100 mg, 0.37 to 7.06 mg quercetin equivalent (QE /100 mg, and 0.09 to 1.31 mg QE/100 mg, respectively. The betacyanin contents were 40.42 and 6.35 mg Amaranthin Equivalent/100 g aerial parts (dry weight in <em>A. cruentusem> and <em>A. hybridusem>, respectively. Free-radical scavenging activity expressed as IC50 (DPPH method and iron reducing power (FRAP method ranged from 56 to 423 µg/mL and from 2.26 to 2.56 mmol AAE/g, respectively. Xanthine oxidase inhibitory activities of extracts of <em>A. cruentus em>and <em>A. hybridusem> were 3.18% and 38.22%, respectively.<em> em>The> A. hybridusem> extract showed the best antioxidant and xanthine oxidase inhibition activities. The results indicated that the phytochemical contents of the two species justify their traditional uses as nutraceutical food plants.

  4. Virtude e felicidade em Sêneca

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    José João Neves Barbosa Vicente

    2016-06-01

    Full Text Available Viver feliz é o que todos almejam, mas o caminho para a felicidade não parece estar claro para todos. Os ensinamentos de Sêneca nos apontam alguns caminhos, ainda que para o nosso tempo, são caminhos considerados de acesso difícil, pois Sêneca nos diz que, para sermos felizes, devemos dirigir nossos olhares sempre para as virtudes e nunca para o gozo dos prazeres, estes nos escravizam, enquanto aquelas nos libertam. Portanto, o propósito deste texto é refletir, ainda que seja em termos introdutórios, sobre a felicidade em Sêneca que pode ser entendido a partir de uma relação com a virtude; ou seja, para ele, não é possível ser feliz se deixarmos de buscar ou viver nas virtudes.

  5. Governo e Poder em Foucault

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    Monica Loyola Stival

    Full Text Available RESUMO: O presente artigo mostra que o conceito de "governo" de Michel Foucault ocupa o espaço aberto por sua crítica ao poder moderno. Foucault passa aos poucos do conceito de poder à noção de governo em suas análises. Porém, não se trata de substituição de conceitos equivalentes, mas de um refinamento conceitual que ilumina a dimensão da atividade dos sujeitos como base das relações sociais e políticas modernas. Assim, este texto tem dois momentos distintos e complementares: mostra a possibilidade de passar do conceito de poder ao conceito de governo, pelo menos como elemento central da análise social e política, e discute o alcance do conceito de governo, que se instala em uma dimensão diferente daquela do poder.

  6. Sinais em neurorradiologia: parte 1

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    Fabrício Guimarães Gonçalves

    2011-04-01

    Full Text Available O uso de sinais ou analogias na interpretação de imagens na radiologia médica é prática comum e antiga entre os radiologistas. Comparação entre achados de imagem com animais, alimentos ou objetos se faz de modo natural. Muitos sinais são bastante específicos e em alguns casos patognomônicos. Independentemente do grau de especificidade, sinais auxiliam a prática radiológica. Vários sinais já foram descritos em neurorradiologia. Neste artigo os autores demonstrarão 15 sinais neurorradiológicos. Serão abordados as principais características de cada um, a sua importância na prática clínica e os seus achados de imagem.

  7. Paratuberculose em ruminantes no Brasil

    OpenAIRE

    Yamasaki,Elise M.; Brito,Marilene F.; Mota,Rinaldo A.; McIntosh,Douglas; Tokarnia,Carlos H.

    2013-01-01

    A paratuberculose ou doença de Johne é uma enterite granulomatosa causada por Mycobacterium avium subsp. paratuberculosis (Map) e comumente afeta ruminantes domésticos, no entanto, pode infectar várias espécies de mamíferos. Está presente nos cinco continentes e é considerada endêmica em algumas regiões pela Organização Internacional de Epizootias (OIE). Pertence à lista de enfermidades notificáveis, que compreende as doenças transmissíveis de importância sócio-econômica e/ou em saúde-pública...

  8. Culturas orais em sociedades letradas

    Directory of Open Access Journals (Sweden)

    Geraldi João Wanderley

    2000-01-01

    Full Text Available Na relação entre linguagem e cultura, um aspecto essencial diz respeito às diferentes funções da escrita e às formas de sua apropriação social em sociedades letradas. Tomando como inspiração a forma de um uso específico da escrita pelo povo indígena Jarawara e narrativas de ribeirinhos do rio Madeira do mito amazônico Cobra Norato, são discutidas as diferentes relações entre oralidade e escrita que, atravessadas pelas relações de poder, transformam o alfabeto, de artefato histórico construído para o registro da oralidade, em espaço social de construção de distinções, clivagens e exclusões.

  9. Bacharelado em psicopedagogia = Psycopedagogy Course

    Directory of Open Access Journals (Sweden)

    Ramos, Maria Beatriz Jacques

    2007-01-01

    Full Text Available Este texto mostra a história da implantação do Curso de Bacharelado em Psicopedagogia na FACED, PUCRS. Neste texto são apresentados os referenciais teóricos e dados sobre a atuação do psicopedagogo nos campos preventivo e terapêutico explicitando a relevância da formação de profissionais nesta área

  10. Iatrogenia em pacientes idosos hospitalizados

    Directory of Open Access Journals (Sweden)

    Carvalho-Filho Eurico T.

    1998-01-01

    Full Text Available Analisar as complicações iatrogênicas apresentadas por idosos hospitalizados. Estudo retrospectivo dos prontuários de 96 pacientes, 48 do sexo masculino e 48 do feminino, com idades variando de 60 a 93 anos (média: 75,7 anos, hospitalizados durante o ano de 1995 em enfermaria geriátrica. A análise da evolução dos pacientes durante o período de hospitalização permitiu evidenciar: 1 em 42 (43,7% pacientes ocorreram uma ou mais complicações iatrogênicas, num total de 56 episódios; 2 manifestações relacionadas aos procedimentos diagnósticos corresponderam a 17,9% das iatrogenias; 3 alterações relacionadas às medidas terapêuticas corresponderam a 58,9%, sendo 32,1% referentes à terapêutica farmacológica e 26,8% a outros procedimentos terapêuticos; 4 manifestações iatrogênicas não relacionadas diretamente às afecções (úlceras de decúbito, quedas e fraturas corresponderam a 23,2%; 5 a presença de manifestações iatrogênicas correlacionou-se com período mais prolongado de internação; 6 cinco pacientes faleceram em conseqüência direta de complicações iatrogênicas. A iatrogenia é freqüente em pacientes idosos hospitalizados, podendo determinar manifestações graves e mesmo fatais. Como uma significativa proporção dessas complicações pode ser evitada através de medidas adequadas, deve-se procurar identificar suas causas e desenvolver métodos para previni-la ou reduzir seus efeitos.

  11. COMPETÊNCIA EM MEDICINA

    Directory of Open Access Journals (Sweden)

    Hélio Teixeira MD.

    2005-01-01

    Full Text Available Competência no exercício da medicina depende de um processo evolutivo ao longo da vida do profissional, processo este fundamentado em eficiência, experiência e em princípios éticos. A eficiência depende da cultura médica, de habilidades técnicas e relacionamento interpessoal com o paciente. A experiência ao longo da vida vai refinando o médico, favorecendo o evolver do conhecimento e da sabedoria vivencial. Finalmente, a ética médica se fundamenta na justiça, compaixão e amor ao próximo. Didaticamente, distinguimos 3 fases da evolução profissional do médico: a infância profissional ou visão linear: o médico se restringe em geral ao atendimento da doença, negligenciando o doente. É quase exclusivamente técnico e tem percepção acanhada da medicina-arte. b Maturidade profissional ou visão humanística: resultado de evolução da personalidade, da cultura e da experiência do médico, agora voltado para o doente com sua doença. c Excelência profissional ou visão holística: estágio máximo que se pode alcançar, quando o médico vislumbra a si e ao seu cliente em todas suas dimensões integradas e atua como mestre, procurando despertar no paciente condições próprias de cura, oriundas de sua essência. Conclui-se que exercer medicina com competência significa desempenhar adequadamente a ciência e a arte médica.

  12. Iatrogenia em pacientes idosos hospitalizados

    Directory of Open Access Journals (Sweden)

    Eurico T. Carvalho-Filho

    1998-02-01

    Full Text Available Analisar as complicações iatrogênicas apresentadas por idosos hospitalizados. Estudo retrospectivo dos prontuários de 96 pacientes, 48 do sexo masculino e 48 do feminino, com idades variando de 60 a 93 anos (média: 75,7 anos, hospitalizados durante o ano de 1995 em enfermaria geriátrica. A análise da evolução dos pacientes durante o período de hospitalização permitiu evidenciar: 1 em 42 (43,7% pacientes ocorreram uma ou mais complicações iatrogênicas, num total de 56 episódios; 2 manifestações relacionadas aos procedimentos diagnósticos corresponderam a 17,9% das iatrogenias; 3 alterações relacionadas às medidas terapêuticas corresponderam a 58,9%, sendo 32,1% referentes à terapêutica farmacológica e 26,8% a outros procedimentos terapêuticos; 4 manifestações iatrogênicas não relacionadas diretamente às afecções (úlceras de decúbito, quedas e fraturas corresponderam a 23,2%; 5 a presença de manifestações iatrogênicas correlacionou-se com período mais prolongado de internação; 6 cinco pacientes faleceram em conseqüência direta de complicações iatrogênicas. A iatrogenia é freqüente em pacientes idosos hospitalizados, podendo determinar manifestações graves e mesmo fatais. Como uma significativa proporção dessas complicações pode ser evitada através de medidas adequadas, deve-se procurar identificar suas causas e desenvolver métodos para previni-la ou reduzir seus efeitos.

  13. Complaints against an EMS system.

    Science.gov (United States)

    Colwell, Christopher B; Pons, Peter T; Pi, Randy

    2003-11-01

    Complaints against Emergency Medical Services (EMS) agencies represent a concerning and potentially time-consuming problem for all involved in the delivery of prehospital emergency medical care. The objective of this study was to identify the source of complaints against an EMS system to help focus quality and performance improvement and customer service efforts. We conducted a retrospective review of complaints filed against a busy urban EMS agency over a 6-year period. All complaints were included, totaled by season and by year, and categorized by originator and nature of the complaint. A total of 286 complaints were registered during the 6-year period, with an average of 48 per year and 9.3 per 10,000 responses. The most common originators of complaints were patients (53%) followed by medical personnel (19%) and family members or friends (12%). Rude behavior accounted for 23% of the complaints registered, followed by technical skills (20%), transport problems (18%), and loss of belongings (13%). The identification of areas of dissatisfaction will allow focused quality and performance improvement programs directed at customer service and risk management.

  14. Existe sujeito em Michel Maffesoli?

    Directory of Open Access Journals (Sweden)

    Marli Appel da Silva

    2010-06-01

    Full Text Available Este ensaio discute a concepção de sujeito na abordagem teórica de Michel Maffesoli. As ideias desse autor estão em voga em alguns meios acadêmicos no Brasil e são difundidas por algumas mídias de grande circulação nacional. Entretanto, ao longo de suas obras, os pressupostos que definem quem é o sujeito maffesoliano se encontram pouco clarificados. Portanto, para alcançar o objetivo a que se propõe, este ensaio desenvolve uma análise da epistemologia e da ontologia maffesoliana com a finalidade de compreender as origens dos pressupostos desse autor, ou seja, as teorias e os autores em que Maffesoli se baseou para desenvolver uma visão de sujeito. Com essa compreensão, pretende-se responder à questão: existe sujeito na abordagem teórica de Maffesoli.

  15. Adding large EM stack support

    KAUST Repository

    Holst, Glendon

    2016-12-01

    Serial section electron microscopy (SSEM) image stacks generated using high throughput microscopy techniques are an integral tool for investigating brain connectivity and cell morphology. FIB or 3View scanning electron microscopes easily generate gigabytes of data. In order to produce analyzable 3D dataset from the imaged volumes, efficient and reliable image segmentation is crucial. Classical manual approaches to segmentation are time consuming and labour intensive. Semiautomatic seeded watershed segmentation algorithms, such as those implemented by ilastik image processing software, are a very powerful alternative, substantially speeding up segmentation times. We have used ilastik effectively for small EM stacks – on a laptop, no less; however, ilastik was unable to carve the large EM stacks we needed to segment because its memory requirements grew too large – even for the biggest workstations we had available. For this reason, we refactored the carving module of ilastik to scale it up to large EM stacks on large workstations, and tested its efficiency. We modified the carving module, building on existing blockwise processing functionality to process data in manageable chunks that can fit within RAM (main memory). We review this refactoring work, highlighting the software architecture, design choices, modifications, and issues encountered.

  16. Discovery of S···C≡N Intramolecular Bonding in a Thiophenylcyanoacrylate-Based Dye: Realizing Charge Transfer Pathways and Dye···TiO 2 Anchoring Characteristics for Dye-Sensitized Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Jacqueline M. [Cavendish; ISIS; Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, United States; Department; Blood-Forsythe, Martin A. [Cavendish; Lin, Tze-Chia [Cavendish; Pattison, Philip [Swiss; Gong, Yun [Cavendish; Vázquez-Mayagoitia, Álvaro [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, United States; Waddell, Paul G. [Cavendish; Australian Centre for Neutron Scattering, Australian Nuclear Science; Zhang, Lei [Cavendish; Koumura, Nagatoshi [National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan; Mori, Shogo [Division

    2017-07-25

    Donor-pi-acceptor dyes containing thiophenyl pi-conjugated units and cyanoacrylate acceptor groups are among the best-performing organic chromophores used in dye-sensitized solar cell (DSC) applications. Yet, the molecular origins of their high photovoltaic output have remained unclear until now. This synchrotron-based X-ray diffraction study elucidates these origins for the high-performance thiophenylcyanoacrylate-based dye MK-2 (7.7% DSC device efficiency) and its molecular building block, MK-44. The crystal structures of MK-2 and MK-44 are both determined, while a high-resolution charge-density mapping of the smaller molecule was also possible, enabling the nature of its bonding to be detailed. A strong S center dot center dot center dot C equivalent to N intramolecular interaction is discovered, which bears a bond critical point, thus proving that this interaction should be formally classified as a chemical bond. A topological analysis of the pi-conjugated portion of MK-44 shows that this S center dot center dot center dot C equivalent to N bonding underpins the highly efficient intramolecular charge transfer(ICT) in thiophenylcyanoacrylate dyes. This manifests as two bipartite ICT pathways bearing carboxylate and nitrile end points. In turn, these pathways dictate a preferred COO/CN anchoring mode for the dye as it adsorbs onto TiO2 surfaces, to form the dye TiO2 interface that constitutes the DSC working electrode. These results corroborate a recent proposal that all cyanoacrylate groups anchor onto TiO2 in this COO/CN binding configuration. Conformational analysis of the MK-44 and MK-2 crystal structures reveals that this S center dot center dot center dot C equivalent to N bonding will persist in MK-2. Accordingly, this newly discovered bond affords a rational explanation for the attractive photovoltaic properties of,MK-2. More generally, this study provides the first unequivocal evidence for an S center dot center dot center dot C equivalent to N

  17. Extensive reduction in back electron transfer in twisted intramolecular charge-transfer (TICT) coumarin-dye-sensitized TiO(2) nanoparticles/film: a femtosecond transient absorption study.

    Science.gov (United States)

    Debnath, Tushar; Maity, Partha; Lobo, Hyacintha; Singh, Balvant; Shankarling, Ganapati S; Ghosh, Hirendra N

    2014-03-17

    We report the synthesis, characterization, and optical and electrochemical properties of two structurally similar coumarin dyes (C1 and C2). These dyes have been deployed as sensitizers in TiO2 nanoparticles and thin films, and the effect of molecular structure on interfacial electron-transfer dynamics has been studied. Steady-state optical absorption, emission, and time-resolved emission studies on both C1 and C2, varying the polarity of the solvent and the solution pH, suggest that both photoexcited dyes exist in a locally excited (LE) state in solvents of low polarity. In highly polar solvents, however, C1 exists in an intramolecular charge-transfer (ICT) state, whereas C2 exists in both ICT and twisted intramolecular charge-transfer (TICT) states, their populations depending on the degree of polarity of the solvent and the pH of the solution. We have employed femtosecond transient absorption spectroscopy to monitor the charge-transfer dynamics in C1- and C2-sensitized TiO2 nanoparticles and thin films. Electron injection has been confirmed by direct detection of electrons in the conduction band of TiO2 nanoparticles and of radical cations of the dyes in the visible and near-IR regions of the transient absorption spectra. Electron injection in both the C1/TiO2 and C2/TiO2 systems has been found to be pulse-width limited (<100 fs); however, back-electron-transfer (BET) dynamics has been found to be slower in the C2/TiO2 system than in the C1/TiO2 system. The involvement of TICT states in C2 is solely responsible for the higher electron injection yield as well as the slower BET process compared to those in the C1/TiO2 system. Further pH-dependent experiments on C1- and C2-sensitized TiO2 thin films have corroborated the participation of the TICT state in the slower BET process in the C2/TiO2 system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Paratuberculose em ruminantes no Brasil

    Directory of Open Access Journals (Sweden)

    Elise M. Yamasaki

    2013-02-01

    Full Text Available A paratuberculose ou doença de Johne é uma enterite granulomatosa causada por Mycobacterium avium subsp. paratuberculosis (Map e comumente afeta ruminantes domésticos, no entanto, pode infectar várias espécies de mamíferos. Está presente nos cinco continentes e é considerada endêmica em algumas regiões pela Organização Internacional de Epizootias (OIE. Pertence à lista de enfermidades notificáveis, que compreende as doenças transmissíveis de importância sócio-econômica e/ou em saúde-pública, cujo controle é necessário para o comércio internacional de animais e alimentos de origem animal. A importância da doença de Johne não se restringe somente aos prejuízos econômicos causados à indústria animal, mas também na possível participação do Map na íleocolite granulomatosa que afeta seres humanos, conhecida como doença de Crohn. No Brasil, a paratuberculose já foi descrita em diversas espécies de ruminantes e em vários estados. Embora os relatos naturais da enfermidade sejam pontuais, acredita-se na possibilidade da transmissão interespecífica e na disseminação do agente através da compra e venda de animais infectados. O objetivo deste artigo foi reunir as informações disponíveis referentes aos aspectos epidemiológicos, clínico-patológicos e laboratoriais da paratuberculose em bovinos, bubalinos, caprinos e ovinos no Brasil, e salientar a necessidade de implementação de medidas de controle sanitário da enfermidade no país, o que possibilitaria a melhoria da qualidade e valorização dos produtos de origem animal no mercado internacional.

  19. Ultrasound-Assisted Extraction of Carnosic Acid and Rosmarinic Acid Using Ionic Liquid Solution from <em>Rosmarinus officinalisem>>

    Directory of Open Access Journals (Sweden)

    Chunjian Zhao

    2012-09-01

    Full Text Available Ionic liquid based, ultrasound-assisted extraction was successfully applied to the extraction of phenolcarboxylic acids, carnosic acid and rosmarinic acid, from <em>Rosmarinus officinalisem>. Eight ionic liquids, with different cations and anions, were investigated in this work and [C8mim]Br was selected as the optimal solvent. Ultrasound extraction parameters, including soaking time, solid–liquid ratio, ultrasound power and time, and the number of extraction cycles, were discussed by single factor experiments and the main influence factors were optimized by response surface methodology. The proposed approach was demonstrated as having higher efficiency, shorter extraction time and as a new alternative for the extraction of carnosic acid and rosmarinic acid from <em>R. officinalisem>> em>compared with traditional reference extraction methods. Ionic liquids are considered to be green solvents, in the ultrasound-assisted extraction of key chemicals from medicinal plants, and show great potential.

  20. Trophic systems and chorology: data from shrews, moles and voles of Italy preyed by the barn owl / Sistemi trofici e corologia: dati su <em>Soricidae>, <em>Talpidae> ed <em>Arvicolidae> d'Italia predati da <em>Tyto albaem> (Scopoli 1769

    Directory of Open Access Journals (Sweden)

    Longino Contoli

    1986-12-01

    Full Text Available Abstract In small Mammals biogeography, available data are up to now by far too scanty for elucidate the distribution of a lot of taxa, especially with regard to the absence from a given area. In this respect, standardized quantitative sampling techniques, like Owl pellets analysis can enable not only to enhance faunistic knowledges, but also to estimate the actual absence probability of a given taxon "m", lacking from the diet of an individual raptor. For the last purpose, the relevant frequencies of "m" in the other ecologically similar sites of the same raptor species diets are averaged ($f_m$ : the relevant standard error (multiplicated by a coefficient, according to the desired degree of accuracy, in relation of the integral of probabilities subtracted ($overline{F}_m - a E$: then, the probability that a single specimen is not pertaining to "m" is obtained ($P_0 = 1 - F_m + a E$; lastly, the desiderate accuracy probability ($P_d$ is chosen. Now, "$N_d$" (the number of individuals of all prey species in a single site needed for obtain, with the desired probability, a specimen at least of "m" is obtained through $$N = frac{ln P_d}{ln P_0}$$ Obviously, every site-diet with more than "N" preyed individuals and without any "i" specimen is considered to be lacking of such taxon. A "usefulness index" for the above purposes is outlined and checked about three raptors. Some exanples about usefulness of the Owl pellet analysis method in biogeography are given, concerning <em>Tyto albaem> diets in peninsular Italy about: - <em>Sorex minutusem>, lacking in some quite insulated areas; - <em>Sorex araneusem> (sensu stricto, after GRAF et al., 1979, present also in lowland areas in Emilia-Romagna; - <em>Crocidura suaveolensem> and - <em>Suncus etruscusem>, present also in the southermost part of Calabria (Reggio province; - <em>Talpa caecaem>, present also in the Antiapennines of Latium (Cimini mounts; - <em>Talpa romanaem