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Sample records for complex exciton-phonon coupling

  1. Communication: Exciton-phonon information flow in the energy transfer process of photosynthetic complexes

    NASA Astrophysics Data System (ADS)

    Rebentrost, Patrick; Aspuru-Guzik, Alán

    2011-03-01

    Non-Markovian and nonequilibrium phonon effects are believed to be key ingredients in the energy transfer in photosynthetic complexes, especially in complexes which exhibit a regime of intermediate exciton-phonon coupling. In this work, we utilize a recently developed measure for non-Markovianity to elucidate the exciton-phonon dynamics in terms of the information flow between electronic and vibrational degrees of freedom. We study the measure in the hierarchical equation of motion approach which captures strong coupling effects and nonequilibrium molecular reorganization. We propose an additional trace distance measure for the information flow that could be extended to other master equations. We find that for a model dimer system and for the Fenna-Matthews-Olson complex the non-Markovianity is significant under physiological conditions.

  2. Exciton-phonon dynamics on complex networks: Comparison between a perturbative approach and exact calculations

    NASA Astrophysics Data System (ADS)

    Yalouz, Saad; Pouthier, Vincent; Falvo, Cyril

    2017-08-01

    A method combining perturbation theory with a simplifying ansatz is used to describe the exciton-phonon dynamics in complex networks. This method, called PT*, is compared to exact calculations based on the numerical diagonalization of the exciton-phonon Hamiltonian for eight small-sized networks. It is shown that the accuracy of PT* depends on the nature of the network, and three different situations were identified. For most graphs, PT* yields a very accurate description of the dynamics. By contrast, for the Wheel graph and the Apollonian network, PT* reproduces the dynamics only when the exciton occupies a specific initial state. Finally, for the complete graph, PT* breaks down. These different behaviors originate in the interplay between the degenerate nature of the excitonic energy spectrum and the strength of the exciton-phonon interaction so that a criterion is established to determine whether or not PT* is relevant. When it succeeds, our study shows the undeniable advantage of PT* in that it allows us to perform very fast simulations when compared to exact calculations that are restricted to small-sized networks.

  3. Reclassifying exciton-phonon coupling in molecular aggregates: evidence of strong nonadiabatic coupling in oligothiophene crystals.

    PubMed

    Spano, F C; Silvestri, L; Spearman, P; Raimondo, L; Tavazzi, S

    2007-11-14

    Exciton-phonon (EP) coupling in molecular aggregates is reexamined in cases where extended intermolecular interactions result in low-energy excitons with high effective masses. The analysis is based on a single intramolecular vibrational mode with frequency omega0 and Huang-Rhys factor lambda2. When the curvature Jc at the exciton band bottom is much smaller than the free-exciton Davydov splitting W, the strength of the EP coupling is determined by comparing the nuclear relaxation energy lambda2omega0 with the curvature. In this way, weak (lambda2omega0<4piJc), intermediate I (lambda2omega0 approximately 4piJc), and strong I (lambda2omega0>4piJc) coupling regimes are introduced. The conventional intermediate (lambda2omega0 approximately W) and strong (lambda2omega0>W) EP coupling regimes originally defined by Simpson and Peterson [J. Chem. Phys. 26, 588 (1957)] are based solely on the Davydov splitting and are referred to here as intermediate II and strong II regimes, respectively. Within the intermediate I and strong I regimes the near degeneracy of the low-energy excitons allows efficient nonadiabatic coupling, resulting in a spectral splitting between the b- and ac-polarized first replicas in the vibronic progression characterizing optical absorption. Such spectral signatures are clearly observed in OT4 thin films and crystals, where splittings for the lowest energy mode with omega0=161 cm(-1) are as large as 30 cm(-1) with a small variation due to sample disorder. Numerical calculations using a multiphonon BO basis set and a Hamiltonian including linear EP coupling yield excellent agreement with experiment.

  4. Photoluminescence and the exciton-phonon coupling in hydrothermally grown ZnO

    NASA Astrophysics Data System (ADS)

    Mendelsberg, R. J.; Allen, M. W.; Durbin, S. M.; Reeves, R. J.

    2011-05-01

    Near band-edge photoluminescence (PL) from hydrothermally grown bulk ZnO was studied as a function of temperature along with the effects of simultaneous excitation with below-gap photons, allowing for accurate assignment of the emission features not possible from low-temperature data alone. Free exciton emission was clearly observed at low temperatures and dominated the PL spectrum above 100 K. Emission from A excitons bound to three neutral donors dominated the low-temperature PL spectrum. Recombination of B excitons bound to these same neutral donors were also identified along with A excitons bound to the donors in their ionized state. A clear difference in the redshift of free and bound excitons with increasing temperature was observed and attributed to reduced exciton-phonon coupling for the bound excitons. Additionally, Fano resonance of the 1-LO replica of the dominant bound A exciton was observed to reduce its PL intensity which can lead to the misidentification of the 2-LO replica as a donor-acceptor-pair transition.

  5. Optical properties of MgZnO alloys: Excitons and exciton-phonon complexes

    SciTech Connect

    Neumann, M. D.; Cobet, C.; Esser, N.; Laumer, B.; Wassner, T. A.; Eickhoff, M.; Feneberg, M.; Goldhahn, R.

    2011-07-01

    The characteristics of the excitonic absorption and emission around the fundamental bandgap of wurtzite Mg{sub x}Zn{sub 1-x}O grown on c-plane sapphire substrates by plasma assisted molecular beam epitaxy with Mg contents between x = 0 and x = 0.23 are studied using spectroscopic ellipsometry and photoluminescence (PL) measurements. The ellipsometric data were analyzed using a multilayer model yielding the dielectric function (DF). The imaginary part of the DF for the alloys exhibits a pronounced feature which is attributed to exciton-phonon coupling (EPC) similar to the previously reported results for ZnO. Thus, in order to determine reliable transition energies, the spectral dependence is analyzed by a model which includes free excitonic lines, the exciton continuum, and the enhanced absorption due to EPC. A line shape analysis of the temperature-dependent PL spectra yielded in particular the emission-related free excitonic transition energies, which are compared to the results from the DF line-shape analysis. The PL linewidth is discussed within the framework of an alloy disorder model.

  6. Benchmarking calculations of spectral densities for the diagonal and nondiagonal exciton-phonon coupling of tetracene crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Zhu, Chaoyuan; Liang, WanZhen

    2017-08-01

    The spectral densities of diagonal and nondiagonal exciton-phonon (e-p) coupling for tetracene crystal have been calculated by the harmonic oscillator (HO) model and ground-state MD-based approaches. We find that classical MD-based approaches overestimate the coupling of exciton with high-frequency vibrational modes and predict the strongest e-p coupling appeared above 1500 cm-1 whereas HO model and AIMD-based approach predict it appeared at ∼ 1400 cm-1. Additionally, the calculated spectral densities of nondiagonal e-p coupling for three different dimers show that they are continuously distributed in the range of 0-150 cm-1 and are 2-3 order of magnitude smaller than the maxima of diagonal e-p coupling.

  7. Nonuniform Excitonic Charge Distribution Enhances Exciton-Phonon Coupling in ZnSe/CdSe Alloyed Quantum Dots.

    PubMed

    Gong, Ke; Kelley, David F; Kelley, Anne Myers

    2017-02-02

    Zinc to cadmium cation exchange of ZnSe quantum dots has been used to produce a series of alloyed Zn1-xCdxSe quantum dots. As x increases and the lowest-energy exciton shifts to the red, the peak initially broadens and then sharpens as x approaches 1. Resonance Raman spectra obtained with excitation near the lowest excitonic absorption peak show a gradual shift of the longitudinal optical phonon peak from 251 cm(-1) in pure ZnSe to 210 cm(-1) in nearly pure CdSe with strong broadening at intermediate compositions. The LO overtone to fundamental intensity ratio, a rough gauge of exciton-phonon coupling strength, increases considerably for intermediate compositions compared with those of either pure ZnSe or pure CdSe. The results indicate that partial localization of the hole in locally Cd-rich regions of the alloyed particles increases the strengths of local internal electric fields, increasing the coupling between the exciton and polar optical phonons.

  8. Temperature and composition dependent excitonic luminescence and exciton-phonon coupling in CdSeS nanocrystals

    PubMed Central

    2012-01-01

    The yellow- and red-emitting CdSeS nanocrystals (NCs) synthesized through one-step organometallic synthesis method are uniformly assembled in polymethyl methacrylate (PMMA). A higher-energy emission band originates from band-edge excitonic state appeared at low temperature. With the Se dopant concentration increasing, the luminescent spectra of CdSeS NCs have a red-shifted emission peak and a shorter luminescent lifetime, which is attributed to the existence of trapping state caused by surface defect and Se dopant. CdSeS NC shows a shorter luminescence lifetime and higher energy emission peak in PMMA matrix than that in toluene, indicating that the former is more favorable to transfer energy through exciton-phonon coupling. The upconversion luminescence (UCL) is observed using 800 nm femtosecond laser excitation. The pump power dependence demonstrated UCL spectra of yellow-emitting CdSeS NCs has a slope of 2.2, while that of red-emitting CdSeS NCs has a slope of 1.4. The results demonstrate that the two-photon absorption plays a dominating role when Se concentration of CdSeS NCs is lower, while phonon-assisted UCL by one-photon excitation gradually takes place with the amount of Se dopants increasing. PMID:22682098

  9. Effect of Off-Diagonal Exciton-Phonon Coupling on Intramolecular Singlet Fission.

    PubMed

    Huang, Zhongkai; Fujihashi, Yuta; Zhao, Yang

    2017-07-20

    Intramolecular singlet fission (iSF) materials provide remarkable advantages in terms of tunable electronic structures, and quantum chemistry studies have indicated strong electronic coupling modulation by high frequency phonon modes. In this work, we formulate a microscopic model of iSF with simultaneous diagonal and off-diagonal coupling to high-frequency modes. A nonperturbative treatment, the Dirac-Frenkel time-dependent variational approach is adopted using the multiple Davydov trial states. It is shown that both diagonal and off-diagonal coupling can aid efficient singlet fission if excitonic coupling is weak, and fission is only facilitated by diagonal coupling if excitonic coupling is strong. In the presence of off-diagonal coupling, it is found that high frequency modes create additional fission channels for rapid iSF. Results presented here may help provide guiding principles for design of efficient singlet fission materials by directly tuning singlet-triplet interstate coupling.

  10. Band-edge optical transitions in a nonpolar-plane GaN substrate: exciton-phonon coupling and temperature effects

    NASA Astrophysics Data System (ADS)

    Wang, M. Z.; Xu, S. J.

    2016-09-01

    We present a detailed investigation of the band-edge optical transitions involving the interacting exciton-phonon system, especially first-order longitudinal optical (LO) phonon-assisted luminescence of bound and free excitons in m- and c-plane GaN substrates in a low temperature range from 4 K to 40 K. The main luminescence features of all of the three kinds of excitons can be well described by the theoretical models that take exciton-LO-phonon coupling into account. The effective Bohr radii of the excitons play a key role in determining the Huang-Rhys factor characterizing the exciton-LO-phonon coupling strength in GaN. An interesting oscillatory structure is found to appear in the low-temperature luminescence spectra of the nonpolar-plane GaN substrate, which needs to be clarified by further investigations.

  11. Exciton-phonon coupling efficiency in CdSe quantum dots embedded in ZnSe nanowires

    NASA Astrophysics Data System (ADS)

    Bounouar, S.; Morchutt, C.; Elouneg-Jamroz, M.; Besombes, L.; André, R.; Bellet-Amalric, E.; Bougerol, C.; den Hertog, M.; Kheng, K.; Tatarenko, S.; Poizat, J. Ph.

    2012-01-01

    Exciton luminescence of a CdSe quantum dot (QD) inserted in a ZnSe nanowire is strongly influenced by the dark exciton states. Because of the small size of these QDs (2-5 nm), exchange interaction between hole and electron is highly enhanced and we measured large energy splitting between bright and dark exciton states (ΔE∈[4,9.2] meV) and large spin-flip rates between these states. Statistics on many QDs showed that this splitting depends on the QD size. Moreover, we measured an increase of the spin-flip rate to the dark states with increasing energy splitting. We explain this observation with a model, taking into account the fact that the exciton-phonon interaction depends on the bright to dark exciton energy splitting, as well as on the size and shape of the exciton wave function. It also has consequences on the exciton line intensity at high temperature.

  12. Nonperturbative theory of exciton-phonon resonances in semiconductor absorption

    NASA Astrophysics Data System (ADS)

    Hannewald, K.; Bobbert, P. A.

    2005-09-01

    We develop a theory of exciton-phonon sidebands in the absorption spectra of semiconductors. The theory does not rely on an ad hoc exciton-phonon picture, but is based on a more fundamental electron-phonon Hamiltonian, thus avoiding a priori assumptions about excited-state properties. We derive a nonperturbative compact solution that can be looked upon as the semiconductor version of the textbook absorption formula for a two-level system coupled to phonons. Accompanied by an illustrative numerical example, the importance and usefulness of our approach with respect to practical applications for semiconductors is demonstrated.

  13. The shell effect on the room temperature photoluminescence from ZnO/MgO core/shell nanowires: exciton-phonon coupling and strain

    NASA Astrophysics Data System (ADS)

    Vega, N. C.; Marin, O.; Tosi, E.; Grinblat, G.; Mosquera, E.; Moreno, M. S.; Tirado, M.; Comedi, D.

    2017-07-01

    The room temperature photoluminescence from ZnO/MgO core/shell nanowires (NWs) grown by a simple two-step vapor transport method was studied for various MgO shell widths (w). Two distinct effects induced by the MgO shell were clearly identified. The first one, related to the ZnO/MgO interface formation, is evidenced by strong enhancements of the zero-phonon and first phonon replica of the excitonic emission, which are accompanied by a total suppression of its second phonon replica. This effect can be explained by the reduction of the band bending within the ZnO NW core that follows the removal of atmospheric adsorbates and associated surface traps during the MgO growth process on one hand, and a reduced exciton-phonon coupling as a result of the mechanical stabilization of the outermost ZnO NW monolayers by the MgO shell on the other hand. The second effect is the gradual increase of the excitonic emission and decrease in the defect related emission by up to two and one orders of magnitude, respectively, when w is increased in the ˜3-17 nm range. Uniaxial strain build-up within the ZnO NW core with increasing w, as detected by x-ray diffraction measurements, and photocarrier tunneling escape from the ZnO core through the MgO shell enabled by defect-states are proposed as possible mechanisms involved in this effect. These findings are expected to be of key significance for the efficient design and fabrication of ZnO/MgO NW heterostructures and devices.

  14. The shell effect on the room temperature photoluminescence from ZnO/MgO core/shell nanowires: exciton-phonon coupling and strain.

    PubMed

    Vega, N C; Marin, O; Tosi, E; Grinblat, G; Mosquera, E; Moreno, M S; Tirado, M; Comedi, D

    2017-07-07

    The room temperature photoluminescence from ZnO/MgO core/shell nanowires (NWs) grown by a simple two-step vapor transport method was studied for various MgO shell widths (w). Two distinct effects induced by the MgO shell were clearly identified. The first one, related to the ZnO/MgO interface formation, is evidenced by strong enhancements of the zero-phonon and first phonon replica of the excitonic emission, which are accompanied by a total suppression of its second phonon replica. This effect can be explained by the reduction of the band bending within the ZnO NW core that follows the removal of atmospheric adsorbates and associated surface traps during the MgO growth process on one hand, and a reduced exciton-phonon coupling as a result of the mechanical stabilization of the outermost ZnO NW monolayers by the MgO shell on the other hand. The second effect is the gradual increase of the excitonic emission and decrease in the defect related emission by up to two and one orders of magnitude, respectively, when w is increased in the ∼3-17 nm range. Uniaxial strain build-up within the ZnO NW core with increasing w, as detected by x-ray diffraction measurements, and photocarrier tunneling escape from the ZnO core through the MgO shell enabled by defect-states are proposed as possible mechanisms involved in this effect. These findings are expected to be of key significance for the efficient design and fabrication of ZnO/MgO NW heterostructures and devices.

  15. Photoluminescence characteristics of CdSe quantum dots: role of exciton-phonon coupling and defect/trap states

    NASA Astrophysics Data System (ADS)

    Kushavah, Dushyant; Mohapatra, P. K.; Ghosh, Pintu; Singh, Mamraj; Vasa, P.; Bahadur, D.; Singh, B. P.

    2017-07-01

    In this paper, we report temperature dependent photoluminescence (PL) characteristics of CdSe colloidal QDs with average diameter ~2.8 nm. Temperature dependence of strongly confined exciton PL peak position, linewidth and intensity were investigated in 30 K to 300 K temperature range. Our studies reveal nearly four times weaker exciton-LO phonon coupling than bulk CdSe crystal. Theoretically, it should be vanishingly small due to near identical electron and hole charge distributions in strongly confined QDs. On the other hand, exciton-acoustic phonon coupling is an order of magnitude larger than its bulk counterpart. Observed finite value of exciton-LO phonon coupling and enhanced exciton-acoustic phonon coupling are due to piezoelectric strain fields. PL intensity exhibits anomalous behavior in the temperature range 100-230 K. This has been explained by thermally activated detrapping of the charge carriers trapped in the potential wells formed at the interface adjoining dislocations/stacking faults developed during the synthesis process. Above 230 K, PL is partially quenched by thermal escape of charge carriers from luminescing exciton state to higher lying nonluminescing states.

  16. Analytic derivative couplings and first-principles exciton/phonon coupling constants for an ab initio Frenkel-Davydov exciton model: Theory, implementation, and application to compute triplet exciton mobility parameters for crystalline tetracene

    NASA Astrophysics Data System (ADS)

    Morrison, Adrian F.; Herbert, John M.

    2017-06-01

    Recently, we introduced an ab initio version of the Frenkel-Davydov exciton model for computing excited-state properties of molecular crystals and aggregates. Within this model, supersystem excited states are approximated as linear combinations of excitations localized on molecular sites, and the electronic Hamiltonian is constructed and diagonalized in a direct-product basis of non-orthogonal configuration state functions computed for isolated fragments. Here, we derive and implement analytic derivative couplings for this model, including nuclear derivatives of the natural transition orbital and symmetric orthogonalization transformations that are part of the approximation. Nuclear derivatives of the exciton Hamiltonian's matrix elements, required in order to compute the nonadiabatic couplings, are equivalent to the "Holstein" and "Peierls" exciton/phonon couplings that are widely discussed in the context of model Hamiltonians for energy and charge transport in organic photovoltaics. As an example, we compute the couplings that modulate triplet exciton transport in crystalline tetracene, which is relevant in the context of carrier diffusion following singlet exciton fission.

  17. Symmetry-dependent exciton-phonon coupling in 2D and bulk MoS2 observed by resonance Raman scattering.

    PubMed

    Carvalho, Bruno R; Malard, Leandro M; Alves, Juliana M; Fantini, Cristiano; Pimenta, Marcos A

    2015-04-03

    This work describes a resonance Raman study performed on samples with one, two, and three layers (1L, 2L, 3L), and bulk MoS2, using more than 30 different laser excitation lines covering the visible range, and focusing on the intensity of the two most pronounced features of the Raman scattering spectrum of MoS2 (E2g(1) and A1g bands). The Raman excitation profiles of these bands were obtained experimentally, and it is found that the A1g feature is enhanced when the excitation laser is in resonance with A and B excitons of MoS2, while the E2g1 feature is shown to be enhanced when the excitation laser is close to 2.7 eV. We show from the symmetry analysis of the exciton-phonon interaction that the mode responsible for the E2g(1) resonance is identified as the high energy C exciton recently predicted [D. Y. Qiu, F. H. da Jornada, and S. G. Louie, Phys. Rev. Lett. 111, 216805 (2013)].

  18. Low Exciton-Phonon Coupling, High Charge Carrier Mobilities, and Multiexciton Properties in Two-Dimensional Lead, Silver, Cadmium, and Copper Chalcogenide Nanostructures.

    PubMed

    Ding, Yuchen; Singh, Vivek; Goodman, Samuel M; Nagpal, Prashant

    2014-12-18

    The development of two-dimensional (2D) nanomaterials has revealed novel physical properties, like high carrier mobilities and the tunable coupling of charge carriers with phonons, which can enable wide-ranging applications in optoelectronic and thermoelectric devices. While mechanical exfoliation of graphene and some transition metal dichalcogenides (e.g., MoS2, WSe2) has enabled their fabrication as 2D semiconductors and integration into devices, lack of similar syntheses for other 2D semiconductor materials has hindered further progress. Here, we report measurements of fundamental charge carrier interactions and optoelectronic properties of 2D nanomaterials made from two-monolayers-thick PbX, CdX, Cu2X, and Ag2X (X = S, Se) using colloidal syntheses. Extremely low coupling of charge carriers with phonons (2-6-fold lower than bulk and other low-dimensional semiconductors), high carrier mobilities (0.2-1.2 cm(2) V(-1) s(-1), without dielectric screening), observation of infrared surface plasmons in ultrathin 2D semiconductor nanostructures, strong quantum-confinement, and other multiexcitonic properties (different phonon coupling and photon-to-charge collection efficiencies for band-edge and higher-energy excitons) can pave the way for efficient solution-processed devices made from these 2D nanostructured semiconductors.

  19. Vibronic enhancement of excitation energy transport: Interplay between local and non-local exciton-phonon interactions

    NASA Astrophysics Data System (ADS)

    Lee, Myeong H.; Troisi, Alessandro

    2017-02-01

    It has been reported in recent years that vibronic resonance between vibrational energy of the intramolecular nuclear mode and excitation-energy difference is crucial to enhance excitation energy transport in light harvesting proteins. Here we investigate how vibronic enhancement induced by vibronic resonance is influenced by the details of local and non-local exciton-phonon interactions. We study a heterodimer model with parameters relevant to the light-harvesting proteins with the surrogate Hamiltonian quantum dynamics method in a vibronic basis. In addition, the impact of field-driven excitation on the efficiency of population transfer is compared with the instantaneous excitation, and the effect of multi-mode vibronic coupling is presented in comparison with the coupling to a single effective vibrational mode. We find that vibronic enhancement of site population transfer is strongly suppressed with the increase of non-local exciton-phonon interaction and increasing the number of strongly coupled high-frequency vibrational modes leads to a further decrease in vibronic enhancement. Our results indicate that vibronic enhancement is present but may be much smaller than previously thought and therefore care needs to be taken when interpreting its role in excitation energy transport. Our results also suggest that non-local exciton-phonon coupling, which is related to the fluctuation of the excitonic coupling, may be as important as local exciton-phonon coupling and should be included in any quantum dynamics model.

  20. Atypical Exciton-Phonon Interactions in WS2 and WSe2 Monolayers Revealed by Resonance Raman Spectroscopy.

    PubMed

    Del Corro, E; Botello-Méndez, A; Gillet, Y; Elias, A L; Terrones, H; Feng, S; Fantini, C; Rhodes, Daniel; Pradhan, N; Balicas, L; Gonze, X; Charlier, J-C; Terrones, M; Pimenta, M A

    2016-04-13

    Resonant Raman spectroscopy is a powerful tool for providing information about excitons and exciton-phonon coupling in two-dimensional materials. We present here resonant Raman experiments of single-layered WS2 and WSe2 using more than 25 laser lines. The Raman excitation profiles of both materials show unexpected differences. All Raman features of WS2 monolayers are enhanced by the first-optical excitations (with an asymmetric response for the spin-orbit related XA and XB excitons), whereas Raman bands of WSe2 are not enhanced at XA/B energies. Such an intriguing phenomenon is addressed by DFT calculations and by solving the Bethe-Salpeter equation. These two materials are very similar. They prefer the same crystal arrangement, and their electronic structure is akin, with comparable spin-orbit coupling. However, we reveal that WS2 and WSe2 exhibit quite different exciton-phonon interactions. In this sense, we demonstrate that the interaction between XC and XA excitons with phonons explains the different Raman responses of WS2 and WSe2, and the absence of Raman enhancement for the WSe2 modes at XA/B energies. These results reveal unusual exciton-phonon interactions and open new avenues for understanding the two-dimensional materials physics, where weak interactions play a key role coupling different degrees of freedom (spin, optic, and electronic).

  1. Exciton-phonon interaction in Al0.4Ga0.6N/Al0.53Ga0.47N multiple quantum wells

    NASA Astrophysics Data System (ADS)

    Liu, Ya-Li; Jin, Peng; Liu, Gui-Peng; Wang, Wei-Ying; Qi, Zhi-Qiang; Chen, Chang-Qing; Wang, Zhan-Guo

    2016-08-01

    The exciton-phonon interaction in Al0.4Ga0.6N/Al0.53Ga0.47N multiple quantum wells (MQWs) is studied by deep-ultraviolet time-integrated and time-resolved photoluminescence (PL). Up to four longitudinal-optical (LO) phonon replicas of exciton recombination are observed, indicating the strong coupling of excitons with LO phonons in the MQWs. Moreover, the exciton-phonon coupling strength in the MQWs is quantified by the Huang-Rhys factor, and it keeps almost constant in a temperature range from 10 K to 120 K. This result can be explained in terms of effects of fluctuations in the well thickness in the MQWs and the temperature on the exciton-phonon interaction. Project supported by the National Basic Research Program of China (Grant No. 2012CB619306), the Beijing Science and Technology Project, China (Grant No. Z151100003315024), and the National Natural Science Foundation of China (Grant No. 61404132).

  2. Exciton-phonon system on a star graph: A perturbative approach.

    PubMed

    Yalouz, Saad; Pouthier, Vincent

    2016-05-01

    Based on the operatorial formulation of the perturbation theory, the properties of an exciton coupled with optical phonons on a star graph are investigated. Within this method, the dynamics is governed by an effective Hamiltonian, which accounts for exciton-phonon entanglement. The exciton is dressed by a virtual phonon cloud whereas the phonons are clothed by virtual excitonic transitions. In spite of the coupling with the phonons, it is shown that the energy spectrum of the dressed exciton resembles that of a bare exciton. The only differences originate in a polaronic mechanism that favors an energy shift and a decay of the exciton hopping constant. By contrast, the motion of the exciton allows the phonons to propagate over the graph so that the dressed normal modes drastically differ from the localized modes associated to bare phonons. They define extended vibrations whose properties depend on the state occupied by the exciton that accompanies the phonons. It is shown that the phonon frequencies, either red shifted or blue shifted, are very sensitive to the model parameter in general, and to the size of the graph in particular.

  3. Exciton-phonon system on a star graph: A perturbative approach

    NASA Astrophysics Data System (ADS)

    Yalouz, Saad; Pouthier, Vincent

    2016-05-01

    Based on the operatorial formulation of the perturbation theory, the properties of an exciton coupled with optical phonons on a star graph are investigated. Within this method, the dynamics is governed by an effective Hamiltonian, which accounts for exciton-phonon entanglement. The exciton is dressed by a virtual phonon cloud whereas the phonons are clothed by virtual excitonic transitions. In spite of the coupling with the phonons, it is shown that the energy spectrum of the dressed exciton resembles that of a bare exciton. The only differences originate in a polaronic mechanism that favors an energy shift and a decay of the exciton hopping constant. By contrast, the motion of the exciton allows the phonons to propagate over the graph so that the dressed normal modes drastically differ from the localized modes associated to bare phonons. They define extended vibrations whose properties depend on the state occupied by the exciton that accompanies the phonons. It is shown that the phonon frequencies, either red shifted or blue shifted, are very sensitive to the model parameter in general, and to the size of the graph in particular.

  4. Pressure induced increase of the exciton phonon interaction in ZnO/(ZnMg)O quantum wells

    SciTech Connect

    Jarosz, D.; Suchocki, A.; Kozanecki, A.

    2016-03-15

    It is a well-established experimental fact that exciton-phonon coupling is very efficient in ZnO. The intensities of the phonon-replicas in ZnO/(ZnMg)O quantum structures strongly depend on the internal electric field. We performed high-pressure measurements on the single ZnO/(ZnMg)O quantum well. We observed a strong increase of the intensity of the phonon-replicas relative to the zero phonon line. In our opinion this effect is related to pressure induced increase of the strain in quantum structure. As a consequence, an increase of the piezoelectric component of the electric field is observed which leads to an increase of the intensity of the phonon-replicas.

  5. Exciton-phonon interaction breaking all antiunitary symmetries in external magnetic fields

    NASA Astrophysics Data System (ADS)

    Schweiner, Frank; Rommel, Patric; Main, Jörg; Wunner, Günter

    2017-07-01

    Recent experimental investigations by M. Aßmann et al. [Nat. Mater. 15, 741 (2016), 10.1038/nmat4622] on the spectrum of magnetoexcitons in cuprous oxide revealed the statistics of a Gaussian unitary ensemble (GUE). The model of F. Schweiner et al. [Phys. Rev. Lett. 118, 046401 (2017), 10.1103/PhysRevLett.118.046401], which includes the complete cubic valence band structure of the solid, can explain the appearance of GUE statistics if the magnetic field is not oriented in one of the symmetry planes of the cubic lattice. However, it cannot explain the experimental observation of GUE statistics for all orientations of the field. In this paper we investigate the effect of quasiparticle interactions or especially the exciton-phonon interaction on the level statistics of magnetoexcitons and show that the motional Stark field induced by the exciton-phonon interaction leads to the occurrence of GUE statistics for arbitrary orientations of the magnetic field in agreement with experimental observations. Importantly, the breaking of all antiunitary symmetries can be explained only by considering both the exciton-phonon interaction and the cubic crystal lattice.

  6. Unusual Exciton-Phonon Interactions at van der Waals Engineered Interfaces.

    PubMed

    Chow, Colin M; Yu, Hongyi; Jones, Aaron M; Yan, Jiaqiang; Mandrus, David G; Taniguchi, Takashi; Watanabe, Kenji; Yao, Wang; Xu, Xiaodong

    2017-02-08

    Raman scattering is a ubiquitous phenomenon in light-matter interactions, which reveals a material's electronic, structural, and thermal properties. Controlling this process would enable new ways of studying and manipulating fundamental material properties. Here, we report a novel Raman scattering process at the interface between different van der Waals (vdW) materials as well as between a monolayer semiconductor and 3D crystalline substrates. We find that interfacing a WSe2 monolayer with materials such as SiO2, sapphire, and hexagonal boron nitride (hBN) enables Raman transitions with phonons that are either traditionally inactive or weak. This Raman scattering can be amplified by nearly 2 orders of magnitude when a foreign phonon mode is resonantly coupled to the A exciton in WSe2 directly or via an A1(') optical phonon from WSe2. We further showed that the interfacial Raman scattering is distinct between hBN-encapsulated and hBN-sandwiched WSe2 sample geometries. This cross-platform electron-phonon coupling, as well as the sensitivity of 2D excitons to their phononic environments, will prove important in the understanding and engineering of optoelectronic devices based on vdW heterostructures.

  7. Influence of TiO2 and Si on the exciton-phonon interaction in PbI2 and CdS semiconductors evidenced by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Nila, A.; Baltog, I.; Dragoman, D.; Baibarac, M.; Mercioniu, I.

    2017-09-01

    The exciton-phonon interaction, considered as a stimulated Raman scattering process, is studied in different semiconductor mixtures: PbI2/TiO2, PbI2/Si and CdS/Si. Raman spectra recorded at excitation wavelengths of 514.5 and 488 nm for PbI2 and CdS, respectively, reveal a strong enhancement of the Raman lines peaked at 97 and 305 cm-1, evaluated by the ratio I TK/I 300 K between the relative intensities of the spectra recorded in the temperature range of 88-300 K. It is found that PbI2 and CdS exhibit a decrease in the Raman intensity modes with decreasing temperature, while in TiO2 and Si an increase in the Raman lines intensities peaked at 138 and 520 cm-1 is observed. This behavior can be explained by an energy transfer process from PbI2 or CdS towards TiO2 and Si. This explanation is supported by the schematic potential energy levels diagram obtained from the density of states, which is calculated using the density functional theory. According to this energy levels diagram, the electrons are expected to migrate directly from the conduction band (CB) energetic levels of the PbI2 and CdS towards the CB levels of TiO2 and Si.

  8. Coupled adaptive complex networks

    NASA Astrophysics Data System (ADS)

    Shai, S.; Dobson, S.

    2013-04-01

    Adaptive networks, which combine topological evolution of the network with dynamics on the network, are ubiquitous across disciplines. Examples include technical distribution networks such as road networks and the internet, natural and biological networks, and social science networks. These networks often interact with or depend upon other networks, resulting in coupled adaptive networks. In this paper we study susceptible-infected-susceptible (SIS) epidemic dynamics on coupled adaptive networks, where susceptible nodes are able to avoid contact with infected nodes by rewiring their intranetwork connections. However, infected nodes can pass the disease through internetwork connections, which do not change with time: The dependencies between the coupled networks remain constant. We develop an analytical formalism for these systems and validate it using extensive numerical simulation. We find that stability is increased by increasing the number of internetwork links, in the sense that the range of parameters over which both endemic and healthy states coexist (both states are reachable depending on the initial conditions) becomes smaller. Finally, we find a new stable state that does not appear in the case of a single adaptive network but only in the case of weakly coupled networks, in which the infection is endemic in one network but neither becomes endemic nor dies out in the other. Instead, it persists only at the nodes that are coupled to nodes in the other network through internetwork links. We speculate on the implications of these findings.

  9. In-situ optical transmission electron microscope study of exciton phonon replicas in ZnO nanowires by cathodoluminescence

    SciTech Connect

    Yang, Shize; Tian, Xuezeng; Wang, Lifen; Wei, Jiake; Qi, Kuo; Li, Xiaomin; Xu, Zhi E-mail: xdbai@iphy.ac.cn Wang, Wenlong; Zhao, Jimin; Bai, Xuedong E-mail: xdbai@iphy.ac.cn; Wang, Enge E-mail: xdbai@iphy.ac.cn

    2014-08-18

    The cathodoluminescence spectrum of single zinc oxide (ZnO) nanowires is measured by in-situ optical Transmission Electron Microscope. The coupling between exciton and longitudinal optical phonon is studied. The band edge emission varies for different excitation spots. This effect is attributed to the exciton propagation along the c axis of the nanowire. Contrary to free exciton emission, the phonon replicas are well confined in ZnO nanowire. They travel along the c axis and emit at the end surface. Bending strain increases the relative intensity of second order phonon replicas when excitons travel along the c-axis.

  10. Coupling suspension complex system optimization

    NASA Astrophysics Data System (ADS)

    English, Kenneth William

    The design of a complex product requires multiple analyses, many of which trade information. In some cases, some information is required before it is available, as a result an estimate must be made of that input for the analysis to proceed. Once the input becomes available, additional calculations must be made to ensure that the result of the analysis reflects the changed input. This iteration creates a considerable computational cost in the design process. This iteration may be eliminated through the reordering of the analyses, or through the temporary or permanent removal of the couplings between the system analyses. This elimination of couplings is termed system reduction. Until relatively recently, the trade of accuracy and efficiency that enables system reduction was only carried out in the context of local sensitivities, how much one analysis output impacts another output. Recent developments expanded this capability to include a system level measure of introduced error into the objective function and constraints, allowing the development of a selection subproblem that trades accuracy and efficiency in the system reduction context. The current state of the trade-off between accuracy and efficiency is far form complete. The initial subproblem formulation resulted in potentially destabilizing sets of couplings being selected, which could result in system analysis convergence errors. Additionally, the technique employed to select couplings for suspension is extremely limited in scope. The designer's intuition and experience had been eliminated from the selection process, replaced by a simple selection algorithm. First, the current coupling suspension problem is augmented, incorporating additional constraints to improve performance in system analysis stability, improved convergence characteristics, and more accurate error growth modeling. The second issue this dissertation addresses is the development of a methodology that allows a designer to interactively

  11. Unified analysis of ensemble and single-complex optical spectral data from light-harvesting complex-2 chromoproteins for gaining deeper insight into bacterial photosynthesis

    NASA Astrophysics Data System (ADS)

    Pajusalu, Mihkel; Kunz, Ralf; Rätsep, Margus; Timpmann, Kõu; Köhler, Jürgen; Freiberg, Arvi

    2015-11-01

    Bacterial light-harvesting pigment-protein complexes are very efficient at converting photons into excitons and transferring them to reaction centers, where the energy is stored in a chemical form. Optical properties of the complexes are known to change significantly in time and also vary from one complex to another; therefore, a detailed understanding of the variations on the level of single complexes and how they accumulate into effects that can be seen on the macroscopic scale is required. While experimental and theoretical methods exist to study the spectral properties of light-harvesting complexes on both individual complex and bulk ensemble levels, they have been developed largely independently of each other. To fill this gap, we simultaneously analyze experimental low-temperature single-complex and bulk ensemble optical spectra of the light-harvesting complex-2 (LH2) chromoproteins from the photosynthetic bacterium Rhodopseudomonas acidophila in order to find a unique theoretical model consistent with both experimental situations. The model, which satisfies most of the observations, combines strong exciton-phonon coupling with significant disorder, characteristic of the proteins. We establish a detailed disorder model that, in addition to containing a C2-symmetrical modulation of the site energies, distinguishes between static intercomplex and slow conformational intracomplex disorders. The model evaluations also verify that, despite best efforts, the single-LH2-complex measurements performed so far may be biased toward complexes with higher Huang-Rhys factors.

  12. Unified analysis of ensemble and single-complex optical spectral data from light-harvesting complex-2 chromoproteins for gaining deeper insight into bacterial photosynthesis.

    PubMed

    Pajusalu, Mihkel; Kunz, Ralf; Rätsep, Margus; Timpmann, Kõu; Köhler, Jürgen; Freiberg, Arvi

    2015-01-01

    Bacterial light-harvesting pigment-protein complexes are very efficient at converting photons into excitons and transferring them to reaction centers, where the energy is stored in a chemical form. Optical properties of the complexes are known to change significantly in time and also vary from one complex to another; therefore, a detailed understanding of the variations on the level of single complexes and how they accumulate into effects that can be seen on the macroscopic scale is required. While experimental and theoretical methods exist to study the spectral properties of light-harvesting complexes on both individual complex and bulk ensemble levels, they have been developed largely independently of each other. To fill this gap, we simultaneously analyze experimental low-temperature single-complex and bulk ensemble optical spectra of the light-harvesting complex-2 (LH2) chromoproteins from the photosynthetic bacterium Rhodopseudomonas acidophila in order to find a unique theoretical model consistent with both experimental situations. The model, which satisfies most of the observations, combines strong exciton-phonon coupling with significant disorder, characteristic of the proteins. We establish a detailed disorder model that, in addition to containing a C_{2}-symmetrical modulation of the site energies, distinguishes between static intercomplex and slow conformational intracomplex disorders. The model evaluations also verify that, despite best efforts, the single-LH2-complex measurements performed so far may be biased toward complexes with higher Huang-Rhys factors.

  13. Synchronization in complex networks with adaptive coupling

    NASA Astrophysics Data System (ADS)

    Zhang, Rong; Hu, Manfeng; Xu, Zhenyuan

    2007-08-01

    Generally it is very difficult to realized synchronization for some complex networks. In order to synchronize, the coupling coefficient of networks has to be very large, especially when the number of coupled nodes is larger. In this Letter, we consider the problem of synchronization in complex networks with adaptive coupling. A new concept about asymptotic stability is presented, then we proved by using the well-known LaSalle invariance principle, that the state of such a complex network can synchronize an arbitrary assigned state of an isolated node of the network as long as the feedback gain is positive. Unified system is simulated as the nodes of adaptive coupling complex networks with different topologies.

  14. Complexity of coupled human and natural systems.

    PubMed

    Liu, Jianguo; Dietz, Thomas; Carpenter, Stephen R; Alberti, Marina; Folke, Carl; Moran, Emilio; Pell, Alice N; Deadman, Peter; Kratz, Timothy; Lubchenco, Jane; Ostrom, Elinor; Ouyang, Zhiyun; Provencher, William; Redman, Charles L; Schneider, Stephen H; Taylor, William W

    2007-09-14

    Integrated studies of coupled human and natural systems reveal new and complex patterns and processes not evident when studied by social or natural scientists separately. Synthesis of six case studies from around the world shows that couplings between human and natural systems vary across space, time, and organizational units. They also exhibit nonlinear dynamics with thresholds, reciprocal feedback loops, time lags, resilience, heterogeneity, and surprises. Furthermore, past couplings have legacy effects on present conditions and future possibilities.

  15. Compensation of coupling in the SSC complex

    SciTech Connect

    Pilat, F.; Bourianoff, G.

    1991-10-01

    This paper will describe a study of the coupling effects and their compensation by means of local depending techniques for some of the accelerators in the SSC Complex. Results concerning corrections and decoupling for the Low Energy and Medium Energy Boosters will be compared to results obtained for the Collider Ring. Some preliminary experimental data about measurement of coupling quantities will also be presented.

  16. Complex mode dynamics of coupled wave oscillators

    NASA Astrophysics Data System (ADS)

    Alexander, T. J.; Yan, D.; Kevrekidis, P. G.

    2013-12-01

    We explore how nonlinear coherent waves localized in a few wells of a periodic potential can act analogously to a chain of coupled oscillators. We identify the small-amplitude oscillation modes of these “coupled wave oscillators” and find that they can be extended into the large amplitude regime, where some “ring” for long times. We also reveal the appearance of complex behavior such as the breakdown of Josephson-like oscillations, the destabilization of fundamental oscillation modes, and the emergence of chaotic oscillations for large amplitude excitations. We show that the dynamics may be accurately described by a discrete model with nearest-neighbor coupling, in which the lattice oscillators bear an effective mass.

  17. Sensitivity of complex, internally coupled systems

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, Jaroslaw

    1990-01-01

    A method is presented for computing sensitivity derivatives with respect to independent (input) variables for complex, internally coupled systems, while avoiding the cost and inaccuracy of finite differencing performed on the entire system analysis. The method entails two alternative algorithms: the first is based on the classical implicit function theorem formulated on residuals of governing equations, and the second develops the system sensitivity equations in a new form using the partial (local) sensitivity derivatives of the output with respect to the input of each part of the system. A few application examples are presented to illustrate the discussion.

  18. Complex behavior in coupled bromate oscillators.

    PubMed

    Chen, Yu; Wang, Jichang

    2005-05-05

    In this study, coupled bromate-oscillators constructed by adding 1,4-cyclohexanedione (1,4-CHD) to the ferroin-catalyzed Belousov-Zhabotinsky reaction are investigated in a batch reactor under anaerobic conditions. Various complex behaviors such as sequential oscillations and bursting phenomena are observed. At low concentrations of ferroin or malonic acid (MA), the development of sequential oscillations is found to depend on the ratio of [1,4-CHD]/[ferroin] and [1,4-CHD]/[MA] rather than their absolute concentrations. As the concentration of MA or ferroin was increased gradually, however, the minimum 1,4-CHD concentration required to induce complex oscillations reaches a plateau. Perturbations by light illustrate that the first oscillatory window is governed by the ferroin-MA-BZ mechanism, whereas the 1,4-CHD-bromate oscillator plays a prominent role during the non-oscillatory evolution and the second oscillatory window. Our conclusion is further supported by numerical simulations in which sequential oscillations observed in experiments are qualitatively reproduced by a modified FKN mechanism.

  19. Coupled Riccati equations for complex plane constraint

    NASA Technical Reports Server (NTRS)

    Strong, Kristin M.; Sesak, John R.

    1991-01-01

    A new Linear Quadratic Gaussian design method is presented which provides prescribed imaginary axis pole placement for optimal control and estimation systems. This procedure contributes another degree of design freedom to flexible spacecraft control. Current design methods which interject modal damping into the system tend to have little affect on modal frequencies, i.e., they predictably shift open plant poles horizontally in the complex plane to form the closed loop controller or estimator pole constellation, but make little provision for vertical (imaginary axis) pole shifts. Imaginary axis shifts which reduce the closed loop model frequencies (the bandwidths) are desirable since they reduce the sensitivity of the system to noise disturbances. The new method drives the closed loop modal frequencies to predictable (specified) levels, frequencies as low as zero rad/sec (real axis pole placement) can be achieved. The design procedure works through rotational and translational destabilizations of the plant, and a coupling of two independently solved algebraic Riccati equations through a structured state weighting matrix. Two new concepts, gain transference and Q equivalency, are introduced and their use shown.

  20. The coupling ATPase complex: an evolutionary view.

    PubMed

    Harris, D A

    1981-01-01

    Phospholipid micelles and vesicles, present in the primordial soup, formed both primitive (surface) catalyst and primitive replicative life forms. With the adoption of a common energy source, ATP, integrated biochemical systems within these vesicles became possible - cells. Fermentation within these primitive cells was favoured by the evolution, first of ion channels allowing protons to leak out, and then of an active ATP-driven pump. In the prokaryotic/mitochondria/chloroplast line, the proton channel was such as to be blocked by dicyclohexylcarbodiimide and the adenosine 5' triphosphate phosphohydrolase (ATPase) by 4-chloro 7-nitrobenzofurazan (Nbf-C1). The ATPase was initially simple (4 subunits) but later, possibly concomitant with its evolution to an ATP synthetase, became more complex (8 subunits). One of the steps in evolution probably involved gene duplication and divergence of 2 subunits (alpha and beta) from the largest of the ATPase subunits. From this stage, the general form of the ATPase was fixed, although sensitivity to, for example, oligomycin involved later, after divergence of the mitochondrial and chloroplast lines. A regulatory protein, the ATPase inhibitor, is found associated with a wide spectrum of coupling ATPases.

  1. Synchronization between two coupled complex networks.

    PubMed

    Li, Changpin; Sun, Weigang; Kurths, Jürgen

    2007-10-01

    We study synchronization for two unidirectionally coupled networks. This is a substantial generalization of several recent papers investigating synchronization inside a network. We derive analytically a criterion for the synchronization of two networks which have the same (inside) topological connectivity. Then numerical examples are given which fit the theoretical analysis. In addition, numerical calculations for two networks with different topological connections are presented and interesting synchronization and desynchronization alternately appear with increasing value of the coupling strength.

  2. Same-Sex Couples: Legal Complexities

    ERIC Educational Resources Information Center

    Oswald, Ramona Faith; Kuvalanka, Katherine A.

    2008-01-01

    In this article, the authors present a typology for organizing our current knowledge regarding same-sex couples in the United States who have and have not established legal ties between partners. This framework is complemented by a discussion of key rulings that define what is legally possible as well as the introduction of "legal consciousness,"…

  3. Same-Sex Couples: Legal Complexities

    ERIC Educational Resources Information Center

    Oswald, Ramona Faith; Kuvalanka, Katherine A.

    2008-01-01

    In this article, the authors present a typology for organizing our current knowledge regarding same-sex couples in the United States who have and have not established legal ties between partners. This framework is complemented by a discussion of key rulings that define what is legally possible as well as the introduction of "legal consciousness,"…

  4. Complex projective synchronization in drive-response stochastic coupled networks with complex-variable systems and coupling time delays

    NASA Astrophysics Data System (ADS)

    Wu, Xuefei; Xu, Chen; Feng, Jianwen

    2015-03-01

    In this paper, the complex projective synchronization in drive-response stochastic coupled networks with complex-variable systems and linear coupling time delays are considered. The pinning control scheme are adopted to achieve complex projective synchronization and several simple and practical sufficient conditions are obtained in a general drive-response network. In addition, the adaptive feedback algorithms are proposed to adjust the control strength. Several numerical simulations are provided to show the effectiveness and feasibility of the proposed methods.

  5. Sparse repulsive coupling enhances synchronization in complex networks.

    PubMed

    Leyva, I; Sendiña-Nadal, I; Almendral, J A; Sanjuán, M A F

    2006-11-01

    Through the last years, different strategies to enhance synchronization in complex networks have been proposed. In this work, we show that synchronization of nonidentical dynamical units that are attractively coupled in a small-world network is strongly improved by just making phase-repulsive a tiny fraction of the couplings. By a purely topological analysis that does not depend on the dynamical model, we link the emerging dynamical behavior with the structural properties of the sparsely coupled repulsive network.

  6. Exciton coupling of surface complexes on a nanocrystal surface.

    PubMed

    Xu, Xiangxing; Ji, Jianwei; Wang, Guan; You, Xiaozeng

    2014-08-25

    Exciton coupling may arise when chromophores are brought into close spatial proximity. Herein the intra-nanocrystal exciton coupling of the surface complexes formed by coordination of 8-hydroxyquinoline to ZnS nanocrystals (NCs) is reported. It is studied by absorption, photoluminescence (PL), PL excitation (PLE), and PL lifetime measurements. The exciton coupling of the surface complexes tunes the PL color and broadens the absorption and PLE windows of the NCs, and thus is a potential strategy for improving the light-harvesting efficiency of NC solar cells and photocatalysts.

  7. Adaptive synchronization of two nonlinearly coupled complex dynamical networks with delayed coupling

    NASA Astrophysics Data System (ADS)

    Zheng, Song; Wang, Shuguo; Dong, Gaogao; Bi, Qinsheng

    2012-01-01

    This paper investigates the adaptive synchronization between two nonlinearly delay-coupled complex networks with the bidirectional actions and nonidentical topological structures. Based on LaSalle's invariance principle, some criteria for the synchronization between two coupled complex networks are achieved via adaptive control. To validate the proposed methods, the unified chaotic system as the nodes of the networks are analyzed in detail, and numerical simulations are given to illustrate the theoretical results.

  8. Complex network synchronization of chaotic systems with delay coupling

    SciTech Connect

    Theesar, S. Jeeva Sathya Ratnavelu, K.

    2014-03-05

    The study of complex networks enables us to understand the collective behavior of the interconnected elements and provides vast real time applications from biology to laser dynamics. In this paper, synchronization of complex network of chaotic systems has been studied. Every identical node in the complex network is assumed to be in Lur’e system form. In particular, delayed coupling has been assumed along with identical sector bounded nonlinear systems which are interconnected over network topology.

  9. Evolution of photoelectron vibrational coupling with molecular complexity

    NASA Astrophysics Data System (ADS)

    Poliakoff, E. D.; Lucchese, R. R.

    2006-11-01

    We review how electronic and vibrational degrees of freedom become coupled in molecular photoionization, and describe effects that emerge as the molecular complexity increases. Molecular photoionization is frequently influenced by the temporary trapping of the continuum electron in the field of the target molecules, which is referred to as a shape resonance, as it depends on the shape of the potential experienced by the exiting photoelectron. Such resonances couple electronic and vibrational motion, and the nature of the coupling can vary widely for polyatomic molecules. We show how vibrationally resolved photoelectron spectra acquired as a function of energy can be used to elucidate such coupling. The experiments are analysed using physically realistic and computationally tractable Schwinger variational theory, and the systems studied to date can be well understood using an independent-particle, adiabatic nuclei framework. As a result, simple and intuitive pictures emerge, even when dealing with scattering phenomena involving complex molecular targets and potentials.

  10. Ideal gas behavior of a strongly coupled complex (dusty) plasma.

    PubMed

    Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry

    2013-07-05

    In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

  11. Anticipated synchronization in coupled complex Ginzburg-Landau systems.

    PubMed

    Ciszak, Marzena; Mayol, Catalina; Mirasso, Claudio R; Toral, Raul

    2015-09-01

    We study the occurrence of anticipated synchronization in two complex Ginzburg-Landau systems coupled in a master-slave configuration. Master and slave systems are ruled by the same autonomous function, but the slave system receives the injection from the master and is subject to a negative delayed self-feedback loop. We give evidence that the magnitude of the largest anticipation time, obtained for complex-valued coupling constants, depends on the dynamical regime where the system operates (defect turbulence, phase turbulence, or bichaos) and scales with the linear autocorrelation time of the system. We also provide analytical conditions for the stability of the anticipated synchronization manifold that are in qualitative agreement with those obtained numerically. Finally, we report on the existence of anticipated synchronization in coupled two-dimensional complex Ginzburg-Landau systems.

  12. Synchronization of complex networks coupled by periodically intermittent noise

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Yan, Huiyun; Li, Jiaorui

    2016-04-01

    Noise is ubiquitous in real systems, so it is important to investigate the effects of noise on the network system. In this paper, the synchronization of complex network coupled by periodically intermittent noise is investigated and a sufficient condition of noise-induced synchronization is obtained analytically via stability theory of stochastic differential equation. The sufficient condition provides a theoretical reference for the analysis of the impact of coupling noise intensity, duration, coupled oscillator number and other parameters on the synchronization behavior. As examples, Rossler-like and Lorenz network systems are presented to verify the theoretical result.

  13. From globally coupled maps to complex-systems biology

    SciTech Connect

    Kaneko, Kunihiko

    2015-09-15

    Studies of globally coupled maps, introduced as a network of chaotic dynamics, are briefly reviewed with an emphasis on novel concepts therein, which are universal in high-dimensional dynamical systems. They include clustering of synchronized oscillations, hierarchical clustering, chimera of synchronization and desynchronization, partition complexity, prevalence of Milnor attractors, chaotic itinerancy, and collective chaos. The degrees of freedom necessary for high dimensionality are proposed to equal the number in which the combinatorial exceeds the exponential. Future analysis of high-dimensional dynamical systems with regard to complex-systems biology is briefly discussed.

  14. From globally coupled maps to complex-systems biology

    NASA Astrophysics Data System (ADS)

    Kaneko, Kunihiko

    2015-09-01

    Studies of globally coupled maps, introduced as a network of chaotic dynamics, are briefly reviewed with an emphasis on novel concepts therein, which are universal in high-dimensional dynamical systems. They include clustering of synchronized oscillations, hierarchical clustering, chimera of synchronization and desynchronization, partition complexity, prevalence of Milnor attractors, chaotic itinerancy, and collective chaos. The degrees of freedom necessary for high dimensionality are proposed to equal the number in which the combinatorial exceeds the exponential. Future analysis of high-dimensional dynamical systems with regard to complex-systems biology is briefly discussed.

  15. From globally coupled maps to complex-systems biology.

    PubMed

    Kaneko, Kunihiko

    2015-09-01

    Studies of globally coupled maps, introduced as a network of chaotic dynamics, are briefly reviewed with an emphasis on novel concepts therein, which are universal in high-dimensional dynamical systems. They include clustering of synchronized oscillations, hierarchical clustering, chimera of synchronization and desynchronization, partition complexity, prevalence of Milnor attractors, chaotic itinerancy, and collective chaos. The degrees of freedom necessary for high dimensionality are proposed to equal the number in which the combinatorial exceeds the exponential. Future analysis of high-dimensional dynamical systems with regard to complex-systems biology is briefly discussed.

  16. EGFR-targeting peptide-coupled platinum(IV) complexes.

    PubMed

    Mayr, Josef; Hager, Sonja; Koblmüller, Bettina; Klose, Matthias H M; Holste, Katharina; Fischer, Britta; Pelivan, Karla; Berger, Walter; Heffeter, Petra; Kowol, Christian R; Keppler, Bernhard K

    2017-06-01

    The high mortality rate of lung cancer patients and the frequent occurrence of side effects during cancer therapy demonstrate the need for more selective and targeted drugs. An important and well-established target for lung cancer treatment is the occasionally mutated epidermal growth factor receptor (EGFR). As platinum(II) drugs are still the most important therapeutics against lung cancer, we synthesized in this study the first platinum(IV) complexes coupled to the EGFR-targeting peptide LARLLT (and the shuffled RTALLL as reference). Notably, HPLC-MS measurements revealed two different peaks with the same molecular mass, which turned out to be a transcyclization reaction in the linker between maleimide and the coupled cysteine moiety. With regard to the EGFR specificity, subsequent biological investigations (3-day viability, 14-day clonogenic assays and platinum uptake) on four different cell lines with different verified EGFR expression levels were performed. Unexpectedly, the results showed neither an enhanced activity nor an EGFR expression-dependent uptake of our new compounds. Consequently, fluorophore-coupled peptides were synthesized to re-evaluate the targeting ability of LARLLT itself. However, also with these molecules, flow cytometry measurements showed no correlation of drug uptake with the EGFR expression levels. Taken together, we successfully synthesized the first platinum(IV) complexes coupled to an EGFR-targeting peptide; however, the biological investigations revealed that LARLLT is not an appropriate peptide for enhancing the specific uptake of small-molecule drugs into EGFR-overexpressing cancer cells.

  17. Synchronization in complex delayed dynamical networks with nonsymmetric coupling

    NASA Astrophysics Data System (ADS)

    Wu, Jianshe; Jiao, Licheng

    2007-12-01

    A new general complex delayed dynamical network model with nonsymmetric coupling is introduced, and then we investigate its synchronization phenomena. Several synchronization criteria for delay-independent and delay-dependent synchronization are provided which generalize some previous results. The matrix Jordan canonical formalization method is used instead of the matrix diagonalization method, so in our synchronization criteria, the coupling configuration matrix of the network does not required to be diagonalizable and may have complex eigenvalues. Especially, we show clearly that the synchronizability of a delayed dynamical network is not always characterized by the second-largest eigenvalue even though all the eigenvalues of the coupling configuration matrix are real. Furthermore, the effects of time-delay on synchronizability of networks with unidirectional coupling are studied under some typical network structures. The results are illustrated by delayed networks in which each node is a two-dimensional limit cycle oscillator system consisting of a two-cell cellular neural network, numerical simulations show that these networks can realize synchronization with smaller time-delay, and will lose synchronization when the time-delay increase larger than a threshold.

  18. Synchronization for linear singularly perturbed complex networks with coupling delays

    NASA Astrophysics Data System (ADS)

    Cai, Chenxiao; Xu, Jing; Liu, Yurong; Zou, Yun

    2015-02-01

    This paper is concerned with the synchronization problem about linear singularly perturbed complex network system with coupling delay. The sufficient delay-dependent conditions for the synchronization of the network are established by introducing an equivalent network system with the Lyapunov stability theory. These conditions, which are formulated in terms of linear matrix inequalities, can be solved efficiently by the LMI toolbox of MATLAB. A simulation example is provided to show the validity of the proposed the synchronization conditions of the whole network.

  19. Phase Synchronization in Coupled Complex Systems - From Neuroscience to Climate

    NASA Astrophysics Data System (ADS)

    Kurths, Juergen

    2001-03-01

    The phenomenon of phase synchronization, especially in weakly coupled complex systems will be explained. Next it will be discussed how to identify epochs of phase synchronization in noisy data. In the second part I will demonstrate the potential of this approach for some examples from natural systems; in particular for brain and muscle activity of Parkinsonian patients, cardio-respiratory interactions in humans and rats and for a chaotically forced climate system.

  20. Coupled disease-behavior dynamics on complex networks: A review.

    PubMed

    Wang, Zhen; Andrews, Michael A; Wu, Zhi-Xi; Wang, Lin; Bauch, Chris T

    2015-12-01

    It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease-behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease-behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years.

  1. Coupled disease-behavior dynamics on complex networks: A review

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Andrews, Michael A.; Wu, Zhi-Xi; Wang, Lin; Bauch, Chris T.

    2015-12-01

    It is increasingly recognized that a key component of successful infection control efforts is understanding the complex, two-way interaction between disease dynamics and human behavioral and social dynamics. Human behavior such as contact precautions and social distancing clearly influence disease prevalence, but disease prevalence can in turn alter human behavior, forming a coupled, nonlinear system. Moreover, in many cases, the spatial structure of the population cannot be ignored, such that social and behavioral processes and/or transmission of infection must be represented with complex networks. Research on studying coupled disease-behavior dynamics in complex networks in particular is growing rapidly, and frequently makes use of analysis methods and concepts from statistical physics. Here, we review some of the growing literature in this area. We contrast network-based approaches to homogeneous-mixing approaches, point out how their predictions differ, and describe the rich and often surprising behavior of disease-behavior dynamics on complex networks, and compare them to processes in statistical physics. We discuss how these models can capture the dynamics that characterize many real-world scenarios, thereby suggesting ways that policy makers can better design effective prevention strategies. We also describe the growing sources of digital data that are facilitating research in this area. Finally, we suggest pitfalls which might be faced by researchers in the field, and we suggest several ways in which the field could move forward in the coming years.

  2. Exciton coupling induces vibronic hyperchromism in light-harvesting complexes

    NASA Astrophysics Data System (ADS)

    Schulze, Jan; Torbjörnsson, Magne; Kühn, Oliver; Pullerits, Tõnu

    2014-04-01

    The recently suggested possibility that weak vibronic transitions can be excitonically enhanced in light-harvesting complexes is studied in detail. A vibronic exciton dimer model that includes ground-state vibrations is investigated using the multi-configuration time-dependent Hartree method with a parameter set typical to photosynthetic light-harvesting complexes. The absorption spectra are discussed based on the Coulomb coupling, the detuning of the site energies, and the number of vibrational modes. Fluorescence spectra calculations show that the spectral densities obtained from the low-temperature fluorescence line-narrowing measurements of light-harvesting systems need to be corrected for the effects of excitons. For the J-aggregate configuration, as in most light-harvesting complexes, the true spectral density has a larger amplitude than that obtained from the measurement.

  3. Numerical Experiments In Strongly Coupled Complex (Dusty) Plasmas

    NASA Astrophysics Data System (ADS)

    Hou, L. J.; Ivlev A.; Hubertus M. T.; Morfill, G. E.

    2010-07-01

    Complex (dusty) plasma is a suspension of micron-sized charged dust particles in a weakly ionized plasma with electrons, ions, and neutral atoms or molecules. Therein, dust particles acquire a few thousand electron charges by absorbing surrounding electrons and ions, and consequently interact with each other via a dynamically screened Coulomb potential while undergoing Brownian motion due primarily to frequent collisions with the neutral molecules. When the interaction potential energy between charged dust particles significantly exceeds their kinetic energy, they become strongly coupled and can form ordered structures comprising liquid and solid states. Since the motion of charged dust particles in complex (dusty) plasmas can be directly observed in real time by using a video camera, such systems have been generally regarded as a promising model system to study many phenomena occurring in solids, liquids and other strongly-coupled systems at the kinetic level, such as phase transitions, transport processes, and collective dynamics. Complex plasma physics has now grown into a mature research field with a very broad range of interdisciplinary facets. In addition to usual experimental and theoretical study, computer simulation in complex plasma plays an important role in bridging experimental observations and theories and in understanding many interesting phenomena observed in laboratory. The present talk will focus on a class of computer simulations that are usually non-equilibrium ones with external perturbation and that mimic the real complex plasma experiments (i. e., numerical experiment). The simulation method, i. e., the so-called Brownian Dynamics methods, will be firstly reviewed and then examples, such as simulations of heat transfer and shock wave propagation, will be present.

  4. Coupling Through Tortuous Path Narrow Slot Apertures into Complex Cavitivies

    SciTech Connect

    Jedlicka, Russell P.; Castillo, Steven P.; Warne, Larry K.

    1999-07-26

    A hybrid FEM/MoM model has been implemented to compute the coupling of fields into a cavity through narrow slot apertures having depth. The model utilizes the slot model of Warne and Chen [23]-[29] which takes into account the depth of the slot, wall losses, and inhomogeneous dielectrics in the slot region. The cavity interior is modeled with the mixed-order, covariant-projection hexahedral elements of Crowley [32]. Results are given showing the accuracy and generality of the method for modeling geometrically complex slot-cavity combinations.

  5. On the sensitivity of complex, internally coupled systems

    NASA Technical Reports Server (NTRS)

    Sobieszczanskisobieski, Jaroslaw

    1988-01-01

    A method is presented for computing sensitivity derivatives with respect to independent (input) variables for complex, internally coupled systems, while avoiding the cost and inaccuracy of finite differencing performed on the entire system analysis. The method entails two alternative algorithms: the first is based on the classical implicit function theorem formulated on residuals of governing equations, and the second develops the system sensitivity equations in a new form using the partial (local) sensitivity derivatives of the output with respect to the input of each part of the system. A few application examples are presented to illustrate the discussion.

  6. Complex Plasmonic Nanostructures: Symmetry Breaking and Coupled Systems

    NASA Astrophysics Data System (ADS)

    Lassiter, J. Britt

    Metallic nanostructures support resonant oscillations of their conduction band electrons called localized surface plasmon resonances. Plasmons couple efficiently to light and have enabled a new class of technology for the manipulation of light at the nanoscale. Nanostructures that support plasmon resonances have the potential for a wide range of applications such as enhanced optical spectroscopy techniques for chemical- and bio-sensing, cancer diagnosis and therapy, metamaterials, and energy harvesting. As the field of plasmonics has progressed, these applications have become more sophisticated, requiring increasingly complex nanostructures. For example, coupled nanostructures of two or more nanoparticles are used extensively in plasmon-enhanced spectroscopy techniques because they exhibit extremely large optical field enhancements. Asymmetric nanostructures, such as nanocups (metallic semishells), have been shown to support magnetic modes that could be used in metamaterials applications. This class of complex plasmonic nanostructures holds great potential for both the observation of new physical phenomena and practical applications. This thesis will focus on the fabrication and characterization of several examples of these complex nanostructures using darkfield spectroscopy. The plasmon modes of a dimer consisting of two nanoshells are investigated in both the separated and conductively overlapping regimes and are interpreted using the plasmon hybridization model. Next, coupled nanoclusters of seven particles arranged in a hexagonal pattern are studied. It is found that these nanoclusters support Fano resonances due to the coupling and interference of degenerate subradiant and superradiant plasmon modes. These structures are found to have an extremely high sensitivity to the local dielectric environment, making them attractive for biosensing applications. Variations on the nanocluster geometry are then explored, and it is observed that by adding more particles and

  7. Mixed outer synchronization of coupled complex networks with time-varying coupling delay.

    PubMed

    Wang, Jun-Wei; Ma, Qinghua; Zeng, Li; Abd-Elouahab, Mohammed Salah

    2011-03-01

    In this paper, the problem of outer synchronization between two complex networks with the same topological structure and time-varying coupling delay is investigated. In particular, we introduce a new type of outer synchronization behavior, i.e., mixed outer synchronization (MOS), in which different state variables of the corresponding nodes can evolve into complete synchronization, antisynchronization, and even amplitude death simultaneously for an appropriate choice of the scaling matrix. A novel nonfragile linear state feedback controller is designed to realize the MOS between two networks and proved analytically by using Lyapunov-Krasovskii stability theory. Finally, numerical simulations are provided to demonstrate the feasibility and efficacy of our proposed control approach.

  8. Suicidal dephosphorylation of thiamine pyrophosphate coupled with pyruvate dehydrogenase complex.

    PubMed

    Strumilo, Slawomir; Dobrzyn, Pawel; Czerniecki, Jan; Tylicki, Adam

    2004-12-01

    Earlier it was noted that purified pyruvate dehydrogenase complex (PDC) produced by "Sigma" usually contains almost saturating amounts of thiamine pyrophosphate (ThPP). In this communication we present the observation that the endogenous ThPP coupled to PDC is dephosphorylated while staying at -10 degrees C, because in the enzyme preparation thiamine monophosphate and un-phosphorylated thiamine appear (HPLC determination). Under the same conditions exogenous ThPP is not dephosphorylated despite contact with the PDC preparation. This may suggest that interactions of some active groups of the enzyme with molecules of endogenous ThPP leads to break-up of the phosphoesters bonds, and destruction of the coenzyme. Decrease of PDC activity during storage is not in proportion with the degree of ThPP dephosphorylation. However the observed instability of PDC activity may be a consequence of the spontaneous process of its coenzyme autodestruction.

  9. The complex choreography of transcription-coupled repair.

    PubMed

    Spivak, Graciela; Ganesan, Ann K

    2014-07-01

    A quarter of a century has elapsed since the discovery of transcription-coupled repair (TCR), and yet our fascination with this process has not diminished. Nucleotide excision repair (NER) is a versatile pathway that removes helix-distorting DNA lesions from the genomes of organisms across the evolutionary scale, from bacteria to humans. TCR, defined as a subpathway of NER, is dedicated to the repair of lesions that, by virtue of their location on the transcribed strands of active genes, encumber elongation by RNA polymerases. In this review, we will report on newly identified proteins, protein modifications, and protein complexes that participate in TCR in Escherichia coli and in human cells. We will discuss general models for the biochemical pathways and how and when cells might choose to utilize TCR or other pathways for repair or bypass of transcription-blocking DNA alterations. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Integration of complex reservoir grids for hydromechanical coupling

    NASA Astrophysics Data System (ADS)

    Nakaten, Benjamin; Pohl, Maik; Kempka, Thomas

    2017-04-01

    Geomechanics became an integral part in the assessment of geological subsurface utilization during the last decade. However, complex grids as applied in state-of-the-art reservoir simulation, including local grid refinements, pinch-out elements resulting from geological discontinuities and reservoirs of low thickness, hinder a straight-forward integration of these grids into geomechanical simulations. Hence, the geomechanical modelling community tends to simplify their grid discretization schemes to meet the grid geometry criteria required by geomechanical simulators or to apply complex interpolation methods between reservoir simulation and geomechanical grids. Both approaches are known to result in significant deviations compared to coupled simulations conducted on the very same grid. Hereby, the application of specific interpolation methods further demands for careful result verification between single parameter transfers between both simulation grids, e.g., including the development of model-specific verification procedures. Consequently, utilization of identical grids in both simulators should be preferred over both workarounds. Resolving this pressing issue, we implemented a fast algorithm using FLAC3D [1] intrinsics (C++), allowing for an efficient and seamless integration of Schlumberger ECLIPSE grids [2], generated using, e.g., the Petrel software package [3], including pinch-out elements and local grid refinements (LGRs). This algorithm comprises four major steps: (1) read the ECLIPSE global grid (hexahedron and pinch-out elements) and generate a compressed corner point grid with unique element nodes; (2) read any LGRs present in the model and transfer these to the geomechanical grid using the previously retrieved global grid information; (3) verify if all (including pinch-outs) element geometries meet the geomechanical grid geometry criteria and revise these elements as required; (4) parametrize the global grid and LGR elements and maintain a data

  11. Stability of gravito-coupled complex gyratory astrofluids

    NASA Astrophysics Data System (ADS)

    Kumar Karmakar, Pralay; Das, Papari

    2017-07-01

    We analyze the gravitational instability of complex rotating astrofluids in the presence of dynamic role of dark matter in a homogeneous hydrostatic equilibrium framework. The effects of the lowest-order fluid viscoelasticity, Coriolis force, fluid turbulence and inter-layer frictional coupling dynamics are concurrently considered in spatially-flat geometry. The Coriolis rotation is relative to the center of the entire fluid mass distribution, contributed by both the gyratory bright (visible) and dark (invisible) sectors, conjugated via the mutual gravitational interaction. The turbulence effects are included via the modified Larson equation of state. We use a regular Fourier-based linear perturbation analysis over the rotating fluid field equations to obtain a unique form of quartic dispersion relation with variable coefficients. We numerically carry out the dispersion analysis in two extreme limits: hydrodynamic (low-frequency) and kinetic (high-frequency) regimes. It is demonstrated that, in the former regime, the gas as well as dark matter rotations have stabilizing effects on the Jeans instability of the bi-fluidic admixture. In contrast, in the latter, the rotations play destabilizing roles on the instability. An interesting feature noted here is that the magnitude of the group velocity of the fluctuations throughout increases with both the gas and dark matter rotation frequencies, and vice-versa. We, finally, hope that the obtained results could be helpful in understanding the top-down kinetic mechanisms of bounded structure formation via gravitational collapse dynamics.

  12. Strong Coupling of Localized Surface Plasmons to Excitons in Light-Harvesting Complexes

    PubMed Central

    2016-01-01

    Gold nanostructure arrays exhibit surface plasmon resonances that split after attaching light harvesting complexes 1 and 2 (LH1 and LH2) from purple bacteria. The splitting is attributed to strong coupling between the localized surface plasmon resonances and excitons in the light-harvesting complexes. Wild-type and mutant LH1 and LH2 from Rhodobacter sphaeroides containing different carotenoids yield different splitting energies, demonstrating that the coupling mechanism is sensitive to the electronic states in the light harvesting complexes. Plasmon–exciton coupling models reveal different coupling strengths depending on the molecular organization and the protein coverage, consistent with strong coupling. Strong coupling was also observed for self-assembling polypeptide maquettes that contain only chlorins. However, it is not observed for monolayers of bacteriochlorophyll, indicating that strong plasmon–exciton coupling is sensitive to the specific presentation of the pigment molecules. PMID:27689237

  13. Synchronization in complex dynamical networks with nonsymmetric coupling

    NASA Astrophysics Data System (ADS)

    Wu, Jianshe; Jiao, Licheng

    2008-10-01

    Based on the work of Nishikawa and Motter, who have extended the well-known master stability framework to include non-diagonalizable cases, we develop another extension of the master stability framework to obtain criteria for global synchronization. Several criteria for global synchronization are provided which generalize some previous results. The Jordan canonical transformation method is used in stead of the matrix diagonalization method. Especially, we show clearly that, the synchronizability of a dynamical network with nonsymmetric coupling is not always characterized by its second-largest eigenvalue, even though all the eigenvalues of the nonsymmetric coupling matrix are real. Furthermore, the effects of the asymmetry of coupling on synchronizability of networks with different structures are analyzed. Numerical simulations are also done to illustrate and verify the theoretical results on networks in which each node is a dynamical limit cycle oscillator consisting of a two-cell cellular neural network.

  14. Coupled Dust-Lattice Modes in Magnetized Complex Plasmas

    SciTech Connect

    Farokhi, B.; Shahmansouri, M.

    2008-09-07

    Dust lattice wave modes in a one dimensional plasma crystal (formed by paramagnetic dust particles) suspended in the plasma sheath are studied. The ion flow in the sheath introduces 'ion wakes' below the crystal particles. The wave dispersion relations are found under the influence of inhomogeneous magnetic field, wake charge effect and equilibrium charge gradient. The expression for the wave dispersion relations clearly show that three branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz forces, charge gradient and wake charge effect. We observe a new coupling between the dust lattice modes, which have not reported so far.

  15. Magnetic exchange couplings from noncollinear perturbation theory: dinuclear CuII complexes.

    PubMed

    Phillips, Jordan J; Peralta, Juan E

    2014-08-07

    To benchmark the performance of a new method based on noncollinear coupled-perturbed density functional theory [J. Chem. Phys. 138, 174115 (2013)], we calculate the magnetic exchange couplings in a series of triply bridged ferromagnetic dinuclear Cu(II) complexes that have been recently synthesized [Phys. Chem. Chem. Phys. 15, 1966 (2013)]. We find that for any basis-set the couplings from our noncollinear coupled-perturbed methodology are practically identical to those of spin-projected energy-differences when a hybrid density functional approximation is employed. This demonstrates that our methodology properly recovers a Heisenberg description for these systems, and is robust in its predictive power of magnetic couplings. Furthermore, this indicates that the failure of density functional theory to capture the subtle variation of the exchange couplings in these complexes is not simply an artifact of broken-symmetry methods, but rather a fundamental weakness of current approximate density functionals for the description of magnetic couplings.

  16. Optical absorption in semiconductor quantum dots coupling to dispersive phonons of infinite modes

    NASA Astrophysics Data System (ADS)

    Ding, Zhiwen; Wang, Qin; Zheng, Hang

    2012-10-01

    Optical absorption spectrum of semiconductor quantum dot is investigated by means of an analytical approach based on the Green's function for different forms of coupling strength in an unified method by using the standard model with valence and conduction band levels coupled to dispersive quantum phonons of infinite modes. The analytical expression of the optical absorption coefficient in semiconductor quantum dots is obtained and by this expression the line shape and the peak position of the absorption spectrum are procured. The relation between the properties of absorption spectrum and the forms of coupling strength is clarified, which can be referenced for choosing the proper form of the coupling strength or spectral density to control the features of absorption spectrum of quantum dot. The coupling and confinement induced energy shift and intensity decrease in the absorption spectrum are determined precisely for a wide range of parameters. The results show that the activation energy of the optical absorption is reduced by the effect of exciton-phonon coupling and photons with lower frequencies could also be absorbed in absorption process. With increase of the coupling constant, the line shape of optical absorption spectrum broadens and the peak position moves to lower photon energy with a rapid decrease in intensity at the same time. Both the coupling induced red shift and the confinement induced blue shift conduce to decrease in the intensity of absorption spectrum. Furthermore, this method may have application potential to other confined quantum systems.

  17. Synchronization analysis of delayed complex networks with time-varying couplings

    NASA Astrophysics Data System (ADS)

    Li, Ping; Yi, Zhang

    2008-06-01

    In this paper, a new method is presented to analyze the linear stability of the synchronized state in arbitrarily coupled complex dynamical systems with time delays. The coupling configurations are not restricted to the symmetric and irreducible connections or the non-negative off-diagonal links. The stability criteria are obtained by using Lyapunov-Krasovskii functional method and subspace projection method. These criteria reveal the relationship between coupling matrices and stability of the dynamical networks.

  18. Adaptive global synchronization of a general complex dynamical network with non-delayed and delayed coupling

    NASA Astrophysics Data System (ADS)

    Wen, Sun; Chen, Shihua; Guo, Wanli

    2008-10-01

    This Letter investigates the global synchronization of a general complex dynamical network with non-delayed and delayed coupling. Based on Lasalle's invariance principle, adaptive global synchronization criteria is obtained. Analytical result shows that under the designed adaptive controllers, a general complex dynamical network with non-delayed and delayed coupling can globally asymptotically synchronize to a given trajectory. What is more, the node dynamic need not satisfy the very strong and conservative uniformly Lipschitz condition and the coupling matrix is not assumed to be symmetric or irreducible. Finally, numerical simulations are presented to verify the effectiveness of the proposed synchronization criteria.

  19. Adaptive synchronization of the complex dynamical network with non-derivative and derivative coupling

    NASA Astrophysics Data System (ADS)

    Xu, Yuhua; Zhou, Wuneng; Fang, Jian'an; Sun, Wen

    2010-04-01

    This Letter investigates the synchronization of a general complex dynamical network with non-derivative and derivative coupling. Based on LaSalle's invariance principle, adaptive synchronization criteria are obtained. Analytical result shows that under the designed adaptive controllers, a general complex dynamical network with non-derivative and derivative coupling can asymptotically synchronize to a given trajectory, and several useful criteria for synchronization are given. What is more, the coupling matrix is not assumed to be symmetric or irreducible. Finally, simulations results show the method is effective.

  20. Observer-based synchronization in complex dynamical networks with nonsymmetric coupling

    NASA Astrophysics Data System (ADS)

    Wu, Jianshe; Jiao, Licheng

    2007-12-01

    Based on a general complex dynamical network model with nonsymmetric coupling, some criteria for synchronization are proposed based on the approach of state observer design. Unlike the nonobserver-based dynamical networks, where the coupling between two connected nodes is defined by an inner coupling matrix and full state coupling is typically needed, in this paper, smaller amount of coupling variables or even only a scalar output signal of each node is needed to synchronize the network. Unlike the commonly researched complex network model, where the coupling between nodes is symmetric, here, in our network model, the coupling configuration matrix is not assumed to be symmetric and may have complex eigenvalues. The matrix Jordan canonical formalization method is used instead of the matrix diagonalization method, so in our synchronization criteria, the coupling configuration matrix is not required to be diagonalizable. Especially, the proposed step-by-step approach is simpler in computation than the existent ones, which usually rely heavily on numerical toolbox, and may be done by hand completely. An example is given to illustrate the step-by-step approach, in which each node is a two-dimensional dynamical limit cycle oscillator system consisting of a two-cell cellular neural network, and numerical simulations are also done to verify the results of design.

  1. Symmetrized complex amplitudes for He double photoionization from the time-dependent close coupling and exterior complex scaling methods

    SciTech Connect

    Horner, D.A.; Colgan, J.; Martin, F.; McCurdy, C.W.; Pindzola, M.S.; Rescigno, T.N.

    2004-06-01

    Symmetrized complex amplitudes for the double photoionization of helium are computed by the time-dependent close-coupling and exterior complex scaling methods, and it is demonstrated that both methods are capable of the direct calculation of these amplitudes. The results are found to be in excellent agreement with each other and in very good agreement with results of other ab initio methods and experiment.

  2. Towards quantification of vibronic coupling in photosynthetic antenna complexes

    NASA Astrophysics Data System (ADS)

    Singh, V. P.; Westberg, M.; Wang, C.; Dahlberg, P. D.; Gellen, T.; Gardiner, A. T.; Cogdell, R. J.; Engel, G. S.

    2015-06-01

    Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency—by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime.

  3. Towards quantification of vibronic coupling in photosynthetic antenna complexes.

    PubMed

    Singh, V P; Westberg, M; Wang, C; Dahlberg, P D; Gellen, T; Gardiner, A T; Cogdell, R J; Engel, G S

    2015-06-07

    Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency--by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime.

  4. Towards quantification of vibronic coupling in photosynthetic antenna complexes

    SciTech Connect

    Singh, V. P.; Westberg, M.; Wang, C.; Gellen, T.; Engel, G. S.; Dahlberg, P. D.; Gardiner, A. T.; Cogdell, R. J.

    2015-06-07

    Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency—by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime.

  5. Towards quantification of vibronic coupling in photosynthetic antenna complexes

    PubMed Central

    Singh, V. P.; Westberg, M.; Wang, C.; Dahlberg, P. D.; Gellen, T.; Gardiner, A. T.; Cogdell, R. J.

    2015-01-01

    Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency—by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime. PMID:26049466

  6. Imidazole-nitrile or imidazole-isonitrile C-C coupling on rhenium tricarbonyl complexes.

    PubMed

    Viguri, Maialen Espinal; Huertos, Miguel A; Pérez, Julio; Riera, Lucía

    2013-09-23

    Ligand activation: Deprotonation of the nitrile or isonitrile complexes [Re(CO)3(N-RIm)2(L)](+) (N-RIm = N-alkylimidazole; L = N≡CtBu, C≡NtBu) selectively afforded alkylidenamido or iminoacyl derivatives, respectively, in which C-C coupling has occurred. Protonation of the latter complex leads to aminocarbene products.

  7. Rhodium Complex and Enzyme Couple Mediated Electrochemical Detection of Adenosine.

    PubMed

    Han, Dawoon; Kim, Hyeong-Mook; Chand, Rohit; Kim, Gyumin; Shin, Ik-Soo; Kim, Yong-Sang

    2015-10-01

    Adenosine is one of the nucleoside which plays an important role in signal transduction and neuromodulation. This work proposes a simple electrochemical assay, comprising two enzymes and rhodium complex based electron transfer mediator, for the detection of adenosine. Sequential reaction of adenosine deaminase and L-glutamic dehydrogenase and the supporting cycle between β-NADH and mediator enable quantitative analysis of adenosine. Role of electron transfer mediator is the conveyance of proton from electrode to β-NAD(+) for regeneration of β-NADH. The electrochemical characteristics of electron transfer mediator were also studied. Real-time adenosine detection was carried out using this multiple enzyme based chronoamperometric assay. The analysis results show a low limit of detection (140 μM) and good correspondence between current signal and the adenosine concentration (R (2) = 0.997).

  8. Handling Qualities of Model Reference Adaptive Controllers with Varying Complexity for Pitch-Roll Coupled Failures

    NASA Technical Reports Server (NTRS)

    Schaefer, Jacob; Hanson, Curt; Johnson, Marcus A.; Nguyen, Nhan

    2011-01-01

    Three model reference adaptive controllers (MRAC) with varying levels of complexity were evaluated on a high performance jet aircraft and compared along with a baseline nonlinear dynamic inversion controller. The handling qualities and performance of the controllers were examined during failure conditions that induce coupling between the pitch and roll axes. Results from flight tests showed with a roll to pitch input coupling failure, the handling qualities went from Level 2 with the baseline controller to Level 1 with the most complex MRAC tested. A failure scenario with the left stabilator frozen also showed improvement with the MRAC. Improvement in performance and handling qualities was generally seen as complexity was incrementally added; however, added complexity usually corresponds to increased verification and validation effort required for certification. The tradeoff between complexity and performance is thus important to a controls system designer when implementing an adaptive controller on an aircraft. This paper investigates this relation through flight testing of several controllers of vary complexity.

  9. Transient complex oscillations in a closed chemical system with coupled autocatalysis

    NASA Astrophysics Data System (ADS)

    Zhao, Jinpei; Chen, Yu; Wang, Jichang

    2005-03-01

    In this study, hydroquinone was introduced to the classic Belousov-Zhabotinsky (BZ) reaction to build up coupled autocatalytic feedbacks. Various complex dynamical behaviors including successive period-adding bifurcations, irregular oscillations, and frequency modulations were observed in the coupled reaction system. Not only the complexity of oscillations but also the time period during which complex oscillations persist were found to depend greatly on the initial concentration of hydroquinone, which was expected to manifest the coupling strength in the studied system. Dependence of the observed transient complex oscillations on concentrations of ferroin, sulfuric acid, bromate, and malonic acid was also characterized systematically. Numerical simulations with a modified BZ model via incorporating reactions involving hydroquinone and products of hydroquinone qualitatively reproduced the influence of hydroquinone seen in experiments.

  10. Topology identification of the complex networks with non-delayed and delayed coupling

    NASA Astrophysics Data System (ADS)

    Guo, Wanli; Chen, Shihua; Sun, Wen

    2009-10-01

    In practical situation, there exists many uncertain information in complex networks, such as the topological structures. So the topology identification is an important issue in the research of the complex networks. Based on LaSalle's invariance principle, in this Letter, an adaptive controlling method is proposed to identify the topology of a weighted general complex network model with non-delayed and delayed coupling. Finally, simulation results show that the method is effective.

  11. Measurement of Magnitude and Sign of Heteronuclear Coupling Constants in Transition Metal Complexes.

    PubMed

    Otting; Soler; Messerle

    1999-04-01

    Sets of specifically tailored E.COSY-type correlation experiments and double-quantum/zero-quantum (DQ/ZQ) experiments are presented which enable the determination of sign and size of small heteronuclear coupling constants across the metal center of transition metal complexes. For the octahedrally coordinated complexes, [Ru(TPM)(H)(CO)(PPh3)]+[BF4]- (1) and [Ir(TPM)(H)(CO)(CO2CH3)]+[BF4]- (2), 14 of 15 and 15 of 15 possible two-bond scalar coupling constants across the metal center were measured, respectively, using 15N and 15N/13C enriched samples (TPM = tris(1-pyrazolyl)methane)). The reduced coupling constants 2KX-M-Y = 4pi2 2J/(hgammaXgammaY) were found to be positive when the coupled nuclei X and Y were trans with respect to the metal center, and negative when the coupled nuclei were in cis position. The validity of this sign rule was verified for JCC, JNN, JPN, JPC, JCN, JHP, JHC, and JHN couplings. Idiosyncracies associated with 2D NMR spectra for the sign determination of coupling constants with 15N which lead to corrections for the signs of JHN, JPN, and JCN couplings reported previously are discussed. Copyright 1999 Academic Press.

  12. Proton-coupled electron transfer and multielectron oxidations in complexes of ruthenium and osmium

    SciTech Connect

    Dovletoglou, A.

    1992-01-01

    This doctoral research concerns the mechanism of proton-coupled electron transfer over an extended pH range. These processes between ruthenium and osmium complexes and hydroquinones have been studied using spectrophotometric methods and cyclic voltammetry. Elucidation of the mechanistic details has been attempted by using isotopic labelling, kinetic analysis, and numerical simulation of complex kinetic schemes. The coordination and redox chemistry of polypyridyl-acetylacetonato and -oxalato complexes of ruthenium and the role of ancillary ligands in defining the properties of Ru[sup IV]O complexes were explored. These studies represent the first attempt to probe possible 2e[sup [minus

  13. Comment on the relation between the nonadiabatic coupling and the complex intersection of potential energy curves

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.

    1977-01-01

    Simple relations are discussed that provide a correspondence between the complex intersection of two potential surfaces and the nonadiabatic coupling matrix element between those surfaces. These are key quantities in semiclassical and quantum mechanical theories of collision induced electronic transitions. Within the two state approximation, the complex intersection is shown to be directly related to the location and magnitude of the peak in the nonadiabatic coupling. Two cases are considered: the avoided crossing between two potential surfaces; and the spin orbit interaction due to a P-2 halogen atom. Comparisons are made between the results of the two-state model and the results of ab initio quantum chemical calculations.

  14. Electrically coupling complex oxides to semiconductors: A route to novel material functionalities

    DOE PAGES

    Ngai, J. H.; Ahmadi-Majlan, K.; Moghadam, J.; ...

    2017-01-12

    Complex oxides and semiconductors exhibit distinct yet complementary properties owing to their respective ionic and covalent natures. By electrically coupling complex oxides to traditional semiconductors within epitaxial heterostructures, enhanced or novel functionalities beyond those of the constituent materials can potentially be realized. Essential to electrically coupling complex oxides to semiconductors is control of the physical structure of the epitaxially grown oxide, as well as the electronic structure of the interface. In this paper, we discuss how composition of the perovskite A- and B-site cations can be manipulated to control the physical and electronic structure of semiconductor—complex oxide heterostructures. Two prototypicalmore » heterostructures, Ba1-xSrxTiO3/Ge and SrZrxTi1-xO3/Ge, will be discussed. In the case of Ba1-xSrxTiO3/Ge, we discuss how strain can be engineered through A-site composition to enable the re-orientable ferroelectric polarization of the former to be coupled to carriers in the semiconductor. In the case of SrZrxTi1-xO3/Ge we discuss how B-site composition can be exploited to control the band offset at the interface. Finally, analogous to heterojunctions between compound semiconducting materials, control of band offsets, i.e., band-gap engineering, provides a pathway to electrically couple complex oxides to semiconductors to realize a host of functionalities.« less

  15. Metal-enhanced fluorescence of chlorophylls in light-harvesting complexes coupled to silver nanowires.

    PubMed

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Twardowska, Magdalena; Czechowski, Nikodem; Hofmann, Eckhard; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes.

  16. Redox-Coupled Protonation of Respiratory Complex I: The Hydrophilic Domain

    PubMed Central

    Couch, Vernon; Popovic, Dragan; Stuchebrukhov, Alexei

    2011-01-01

    Respiratory complex I, NADH:ubiquinone oxidoreductase, is a large and complex integral membrane enzyme found in respiring bacteria and mitochondria. It is responsible in part for generating the proton gradient necessary for ATP production. Complex I serves as both a proton pump and an entry point for electrons into the respiratory chain. Although complex I is one of the most important of the respiratory complexes, it is also one of the least understood, with detailed structural information only recently available. In this study, full-finite-difference Poisson-Boltzmann calculations of the protonation state of respiratory complex I in various redox states are presented. Since complex I couples the oxidation and reduction of the NADH/ubiquinone redox couple to proton translocation, the interaction of the protonation and redox states of the enzyme are of the utmost significance. Various aspects of complex I function are presented, including the redox-Bohr effect, intercofactor interactions, and the effects of both the protein dielectric and inclusion of the membrane. PMID:21767496

  17. Observation of low-loss broadband supermode propagation in coupled acoustic waveguide complex.

    PubMed

    Shen, Ya-Xi; Peng, Yu-Gui; Chen, Xin-Cheng; Zhao, De-Gang; Zhu, Xue-Feng

    2017-03-28

    We investigate analytically, numerically, and experimentally the low-loss supermode propagation in a coupled acoustic waveguide complex within a broadband. The waveguide complex is implemented with air channels coupled via an ultrathin metafluid layer. We analytically derive the field distribution of incident sound needed for producing acoustic supermodes, and verify the periodically revival propagation in coupled waveguide systems numerically and experimentally. We find out that the supermode wavelength becomes longer for higher mode order or lower frequency. We have also demonstrated the robust propagation of supermodes in broadband. Our scheme can in principle be extended to three dimensions and the ultrasound regime with simplicity and may promote applications of high-fidelity signal transfer in complicated acoustic networks.

  18. Stoichiometric and Catalytic Aryl-Perfluoroalkyl Coupling at Tri-tert-butylphosphine Palladium(II) Complexes.

    PubMed

    Ferguson, Devin M; Bour, James R; Canty, Allan J; Kampf, Jeff W; Sanford, Melanie S

    2017-08-30

    This Communication describes studies of Ph-RF (RF = CF3 or CF2CF3) coupling at Pd complexes of general structure (P(t)Bu3)Pd(II)(Ph)(RF). The CF3 analogue participates in fast Ph-CF3 coupling (<5 min at 80 °C). However, the formation of side products limits the yield of this transformation as well as its translation to catalysis. DFT and experimental studies suggest that the side products derive from facile α-fluoride elimination at the 3-coordinate Pd(II) complex. Furthermore, they show that this undesired pathway can be circumvented by changing from a CF3 to a CF2CF3 ligand. Ultimately, the insights gained from stoichiometric studies enabled the identification of Pd(P(t)Bu3)2 as a catalyst for the Pd-catalyzed cross-coupling of aryl bromides with TMSCF2CF3 to afford pentafluoroethylated arenes.

  19. Coupling centrality and authority of co-processing model on complex networks

    NASA Astrophysics Data System (ADS)

    Zhang, Zhanli; Li, Huibin

    2016-04-01

    Coupling centrality and authority of co-processing model on complex networks are investigated in this paper. As one crucial factor to determine the processing ability of nodes, the information flow with potential time lag is modeled by co-processing diffusion which couples the continuous time processing and the discrete diffusing dynamics. Exact results on master equation and stationary state are obtained to disclose the formation. Considering the influence of a node to the global dynamical behavior, coupling centrality and authority are introduced for each node, which determine the relative importance and authority of nodes in the diffusion process. Furthermore, the experimental results on large-scale complex networks confirm our analytical prediction.

  20. Pattern formation based on complex coupling mechanism in dielectric barrier discharge

    SciTech Connect

    Liu, Weibo; Dong, Lifang E-mail: pyy1616@163.com; Wang, Yongjie; Zhang, Hao; Pan, Yuyang E-mail: pyy1616@163.com

    2016-08-15

    The pattern formation of cinque-dice square superlattice pattern (CDSSP) is investigated based on the complex coupling mechanism in a dielectric barrier discharge (DBD) system. The spatio-temporal structure of CDSSP obtained by using an intensified-charge coupled device indicates that CDSSP is an interleaving of two kinds of subpatterns (mixture of rectangle and square, and dot-line square) which discharge twice in one half voltage, respectively. Selected by the complex coupling of two subpatterns, the CDSSP can be formed and shows good stability. This investigation based on gas discharge theory together with nonlinear theory may provide a deeper understanding for the nonlinear characteristics and even the formation mechanism of patterns in DBD.

  1. Observation of low-loss broadband supermode propagation in coupled acoustic waveguide complex

    PubMed Central

    Shen, Ya-Xi; Peng, Yu-Gui; Chen, Xin-Cheng; Zhao, De-Gang; Zhu, Xue-Feng

    2017-01-01

    We investigate analytically, numerically, and experimentally the low-loss supermode propagation in a coupled acoustic waveguide complex within a broadband. The waveguide complex is implemented with air channels coupled via an ultrathin metafluid layer. We analytically derive the field distribution of incident sound needed for producing acoustic supermodes, and verify the periodically revival propagation in coupled waveguide systems numerically and experimentally. We find out that the supermode wavelength becomes longer for higher mode order or lower frequency. We have also demonstrated the robust propagation of supermodes in broadband. Our scheme can in principle be extended to three dimensions and the ultrasound regime with simplicity and may promote applications of high-fidelity signal transfer in complicated acoustic networks. PMID:28349953

  2. Pattern formation based on complex coupling mechanism in dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Liu, Weibo; Dong, Lifang; Wang, Yongjie; Zhang, Hao; Pan, Yuyang

    2016-08-01

    The pattern formation of cinque-dice square superlattice pattern (CDSSP) is investigated based on the complex coupling mechanism in a dielectric barrier discharge (DBD) system. The spatio-temporal structure of CDSSP obtained by using an intensified-charge coupled device indicates that CDSSP is an interleaving of two kinds of subpatterns (mixture of rectangle and square, and dot-line square) which discharge twice in one half voltage, respectively. Selected by the complex coupling of two subpatterns, the CDSSP can be formed and shows good stability. This investigation based on gas discharge theory together with nonlinear theory may provide a deeper understanding for the nonlinear characteristics and even the formation mechanism of patterns in DBD.

  3. Generalized projective synchronization between two different general complex dynamical networks with delayed coupling

    NASA Astrophysics Data System (ADS)

    Wu, Xiangjun; Lu, Hongtao

    2010-08-01

    In this Letter, generalized projective synchronization (GPS) between two different complex dynamical networks with delayed coupling is investigated. Two complex networks are distinct if they have diverse node dynamics, or different number of nodes, or different topological structures. By using the adaptive control scheme, a sufficient synchronization criterion for this GPS is derived based on the LaSalle invariance principle. Three corollaries are also obtained. It is noticed that the synchronization speed sensitively depends on the adjustable positive constants μ. Furthermore, the coupling configuration matrix is not necessary to be symmetric or irreducible, and the inner coupling matrix need not be symmetric. In addition, the node dynamic need not satisfy the very strong and conservative uniformly Lipschitz condition. Numerical simulations further demonstrate the feasibility and effectiveness of the theoretical results.

  4. Magnetic Exchange Couplings in Heterodinuclear Complexes Based on Differential Local Spin Rotations.

    PubMed

    Joshi, Rajendra P; Phillips, Jordan J; Peralta, Juan E

    2016-04-12

    We analyze the performance of a new method for the calculation of magnetic exchange coupling parameters for the particular case of heterodinuclear transition metals complexes of Cu, Ni, and V. This method is based on a generalized perturbative approach which uses differential local spin rotations via formal Lagrange multipiers (Phillips, J. J.; Peralta, J. E. J. Chem. Phys. 2013, 138, 174115). The reliability of the calculated couplings has been assessed by comparing with results from traditional energy differences with different density functional approximations and with experimental values. Our results show that this method to calculate magnetic exchange couplings can be reliably used for heteronuclear transition metal complexes, and at the same time, that it is independent from the different mapping schemes used in energy difference methods.

  5. The mechanism of coupling between electron transfer and proton translocation in respiratory complex I.

    PubMed

    Sazanov, Leonid A

    2014-08-01

    NADH-ubiquinone oxidoreductase (complex I) is the first and largest enzyme in the respiratory chain of mitochondria and many bacteria. It couples the transfer of two electrons between NADH and ubiquinone to the translocation of four protons across the membrane. Complex I is an L-shaped assembly formed by the hydrophilic (peripheral) arm, containing all the redox centres performing electron transfer and the membrane arm, containing proton-translocating machinery. Mitochondrial complex I consists of 44 subunits of about 1 MDa in total, whilst the prokaryotic enzyme is simpler and generally consists of 14 conserved "core" subunits. Recently we have determined the first atomic structure of the entire complex I, using the enzyme from Thermus thermophilus (536 kDa, 16 subunits, 9 Fe-S clusters, 64 TM helices). Structure suggests a unique coupling mechanism, with redox energy of electron transfer driving proton translocation via long-range (up to ~200 Å) conformational changes. It resembles a steam engine, with coupling elements (akin to coupling rods) linking parts of this molecular machine.

  6. Bis-diimidazolylidine complexes of nickel: investigations into nickel catalyzed coupling reactions.

    PubMed

    Paulose, Tressia A P; Wu, Shih-Chang; Olson, Jeremy A; Chau, Tony; Theaker, Nikki; Hassler, Matt; Quail, J Wilson; Foley, Stephen R

    2012-01-07

    Air and moisture stable homoleptic bis(diimidazolylidine)nickel(II) complexes, ([(diNHC)(2)Ni](2+)) 3a,b and their corresponding silver(I) 4a,b and palladium(II) 5a,b complexes were synthesized and characterized by NMR and single crystal X-ray analysis. The catalytic potential of complex 3a was assessed in Mizoroki-Heck and Suzuki-Miyaura coupling reactions. In the Suzuki-Miyaura coupling reaction, nickel precatalyst 3a was active for the coupling of aryl chlorides as well as aryl fluorides. The analogously synthesized Pd(II) complexes resulted in formation of (diNHC)PdCl(2) species which were not active for the coupling of aryl fluorides. For the Mizoroki-Heck reaction, it was found that aryl iodides could be activated in the absence of nickel or palladium precatalysts when using Na(2)CO(3) or NEt(3) as base while aryl iodides and aryl bromides could be activated in the Suzuki-Miyaura reaction sans precatalyst when K(3)PO(4) was used as base.

  7. Solution of coupled integral equations for quantum scattering in the presence of complex potentials

    SciTech Connect

    Franz, Jan

    2015-01-15

    In this paper, we present a method to compute solutions of coupled integral equations for quantum scattering problems in the presence of a complex potential. We show how the elastic and absorption cross sections can be obtained from the numerical solution of these equations in the asymptotic region at large radial distances.

  8. π-π Stacking and ferromagnetic coupling mechanism on a binuclear Cu(II) complex.

    PubMed

    Chi, Yan-Hui; Yu, Li; Shi, Jing-Min; Zhang, Yi-Quan; Hu, Tai-Qiu; Zhang, Gui-Qiu; Shi, Wei; Cheng, Peng

    2011-02-21

    The ferromagnetic couplings were observed in an unpublished crystal that consists of binuclear copper(II) complexes, namely, [Cu(2)(μ(1,3)-SCN)(2)(PhenOH)(OCH(3))(2)(HOCH(3))(2)] (PhenOH = 2-hydroxy-1,10-phenanthroline), and in the binuclear complex Cu(ii) ion assumes a distorted octahedral geometry and thiocyanate anion functions as a μ(1,3)-SCN(-) equatorial-axial (EA) bridging ligand. The analysis for the crystal structure indicates that there are three types of magnetic coupling pathways, in which two pathways involve π-π stacking between the adjacent complexes and the third one is the μ(1,3)-SCN(-) bridged pathway. The fitting for the data of the variable-temperature magnetic susceptibilities shows that there is a ferromagnetic coupling between adjacent Cu(II) ions with J = 50.02 cm(-1). Theoretical calculations reveal that the two types of π-π stacking resulted in ferromagnetic couplings with J = 4.16 cm(-1) and J = 2.75 cm(-1), respectively, and the bridged thiocyanate anions pathway led to a weaker ferromagnetic interaction with J = 0.88 cm(-1). The theoretical calculations also indicate that the ferromagnetic coupling sign from the two types of π-π stacking does not accord with McConnell I spin-polarization mechanism. The analysis for the Wiberg bond indexes that originate from the π-π stacking atoms indicates that the Wiberg bond indexes are relevant to the associated magnetic coupling magnitude and the Wiberg bond index is one of the key factors that dominates the associated magnetic coupling magnitude.

  9. Direct C-C coupling of two Ni-salphen complexes to yield dinickel-disalphen complexes with symmetric and non-symmetric substitution-patterns.

    PubMed

    Bugenhagen, B E C; Prosenc, M H

    2016-04-25

    The synthesis of symmetric and non-symmetric 5,5'-linked disalophen Ni(ii) complexes by the Suzuki-Miyaura-reaction is reported. Also, the synthesis and structural characterization of four Ni(ii)-precursor complexes are presented. The 5-Br-substituted mononuclear complexes and are coupled to the pinacolborane substituted complexes and yielding the four dinuclear dinickel complexes in good yields. The crystal structure of dinuclear complex was obtained revealing a coplanar arrangement between the two salophen fragments. Electronic spectra as well as DFT-calculations on the ground states and excitation energies are reported and they reveal a small coupling between the electronically saturated Ni-salophen complexes.

  10. Electrostatic effects on proton coupled electron transfer in oxomanganese complexes inspired by the oxygen-evolving complex of photosystem II.

    PubMed

    Amin, Muhamed; Vogt, Leslie; Vassiliev, Serguei; Rivalta, Ivan; Sultan, Mohammad M; Bruce, Doug; Brudvig, Gary W; Batista, Victor S; Gunner, M R

    2013-05-23

    The influence of electrostatic interactions on the free energy of proton coupled electron transfer in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII) are investigated. The reported study introduces an enhanced multiconformer continuum electrostatics (MCCE) model, parametrized at the density functional theory (DFT) level with a classical valence model for the oxomanganese core. The calculated pKa's and oxidation midpoint potentials (E(m)'s) match experimental values for eight complexes, indicating that purely electrostatic contributions account for most of the observed couplings between deprotonation and oxidation state transitions. We focus on pKa's of terminal water ligands in [Mn(II/III)(H2O)6](2+/3+) (1), [Mn(III)(P)(H2O)2](3-) (2, P = 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinato), [Mn2(IV,IV)(μ-O)2(terpy)2(H2O)2](4+) (3, terpy = 2,2':6',2″-terpyridine), and [Mn3(IV,IV,IV)(μ-O)4(phen)4(H2O)2](4+) (4, phen = 1,10-phenanthroline) and the pKa's of μ-oxo bridges and Mn E(m)'s in [Mn2(μ-O)2(bpy)4] (5, bpy = 2,2'-bipyridyl), [Mn2(μ-O)2(salpn)2] (6, salpn = N,N'-bis(salicylidene)-1,3-propanediamine), [Mn2(μ-O)2(3,5-di(Cl)-salpn)2] (7), and [Mn2(μ-O)2(3,5-di(NO2)-salpn)2] (8). The analysis of complexes 6-8 highlights the strong coupling between electron and proton transfers, with any Mn oxidation lowering the pKa of an oxo bridge by 10.5 ± 0.9 pH units. The model also accounts for changes in the E(m)'s by ligand substituents, such as found in complexes 6-8, due to the electron withdrawing Cl (7) and NO2 (8). The reported study provides the foundation for analysis of electrostatic effects in other oxomanganese complexes and metalloenzymes, where proton coupled electron transfer plays a fundamental role in redox-leveling mechanisms.

  11. Polaron dynamics with off-diagonal coupling: beyond the Ehrenfest approximation.

    PubMed

    Huang, Zhongkai; Wang, Lu; Wu, Changqin; Chen, Lipeng; Grossmann, Frank; Zhao, Yang

    2017-01-04

    Treated traditionally by the Ehrenfest approximation, the dynamics of a one-dimensional molecular crystal model with off-diagonal exciton-phonon coupling is investigated in this work using the Dirac-Frenkel time-dependent variational principle with the multi-D2Ansatz. It is shown that the Ehrenfest method is equivalent to our variational method with the single D2Ansatz, and with the multi-D2Ansatz, the accuracy of our simulated dynamics is significantly enhanced in comparison with the semi-classical Ehrenfest dynamics. The multi-D2Ansatz is able to capture numerically accurate exciton momentum probability and help clarify the relation between the exciton momentum redistribution and the exciton energy relaxation. The results demonstrate that the exciton momentum distributions in the steady state are determined by a combination of the transfer integral and the off-diagonal coupling strength, independent of the excitonic initial conditions. We also probe the effect of the transfer integral and the off-diagonal coupling on exciton transport in both real and reciprocal space representations. Finally, the variational method with importance sampling is employed to investigate temperature effects on exciton transport using the multi-D2Ansatz, and it is demonstrated that the variational approach is valid in both low and high temperature regimes.

  12. Altered dynamic coupling of lateral occipital complex during visual perception in schizophrenia

    PubMed Central

    Harvey, Philippe-Olivier; Lee, Junghee; Cohen, Mark S.; Engel, Stephen A.; Glahn, David C.; Nuechterlein, Keith H.; Wynn, Jonathan K.; Green, Michael F.

    2011-01-01

    Introduction There is mounting evidence that visual perception abnormalities in schizophrenia are partly explained by a dysfunction of the lateral occipital complex (LO). We previously demonstrated that schizophrenia patients had broader topography and reduced magnitude of activity of LO. However, the functional connectivity of LO with other brain regions during visual perception has not been directly investigated in schizophrenia. Material and Methods Eighteen patients with schizophrenia and eighteen matched controls performed a backward masking task during functional magnetic resonance imaging (fMRI). Stimulus onset asynchronies were manipulated to change the level of target visibility. To examine connectivity with LO function we conducted psychophysiological interactions (PPI) analyses using: 1) a region of interest (ROI) approach and 2) a whole brain analysis. ROIs were defined based on a contrast of trials on which a target was presented versus null trials in which no stimuli were presented. Results Eleven ROIs were identified. Both groups showed similar strength of coupling between LO and the 11 ROIs when visibility was not taken into account. Healthy controls showed clear changes in coupling between LO and prefrontal and parietal regions as a function of target visibility (higher coupling with more visible targets). In comparison, patients showed reduced dynamic coupling with LO in the right superior frontal gyrus (significant after correcting for multiple comparisons) and a trend for reduced coupling in the left precuneus and left inferior frontal regions. Whole brain analysis identified additional regions that showed dynamic coupling with LO in healthy controls, but not in patients. Discussion The increased coupling between LO and higher-level parietal and prefrontal regions during visual awareness in healthy controls likely reflects visual reentrant processing. The lack of modulation of coupling between LO and key prefrontal and parietal regions found in

  13. A network of allosterically coupled residues in the bacteriophage T4 Mre11-Rad50 complex.

    PubMed

    Gao, Yang; Meyer, Jennifer R; Nelson, Scott W

    2016-11-01

    The Mre11-Rad50 (MR) protein complex, made up of a nuclease and ATPase, respectively, is involved in the processing of double-strand breaks as part of an intricate mechanism for their repair. Although it is clear that the MR complex is subject to allosteric regulation and that there is communication between the nuclease and ATPase active sites, the underlying mechanisms are poorly understood. We performed statistical coupling analysis on Mre11 and Rad50 to predict linked residues based on their evolutionary correlation. This analysis predicted a coevolving sector of six residues that may be allosterically coupled. The prediction was tested using double-mutant cycle analysis of nuclease and ATPase activity. The results indicate that a tyrosine residue located near the active site of Mre11 is allosterically coupled to several Rad50 residues located over 40 Å away. This allosteric coupling may be the basis for the reciprocal regulation of the ATPase and nuclease activities of the complex. © 2016 The Protein Society.

  14. Programs EMCUPL and SCHCOPL: computation of electromagnetic coupling on a layered halfspace with complex conductivities

    USGS Publications Warehouse

    Kauahikaua, James P.; Anderson, Walter L.

    1979-01-01

    A number of efficient numerical computer algorithms are incorporated into a general program called EMCUPL, which calculates the electromagnetic (EM) coupling between two straight wires on the surface of a multilayered half space. Each layer has an isotropic conductivity which may be either real or complex. A second computer program, called SCHCOPL, is described which calculates the coupling for the special case of a Schlumberger or Wenner array also on a multilayered half space. Comparison with other programs shows that EMCUPL is at least as accurate, more generally applicable, and computationally more efficient FORTRAN listings of all subprograms and example calculations are given in the Appendix.

  15. Topological effects on dynamics in complex pulse-coupled networks of integrate-and-fire type

    NASA Astrophysics Data System (ADS)

    Shkarayev, Maxim S.; Kovačič, Gregor; Cai, David

    2012-03-01

    For a class of integrate-and-fire, pulse-coupled networks with complex topology, we study the dependence of the pulse rate on the underlying architectural connectivity statistics. We derive the distribution of the pulse rate from this dependence and determine when the underlying scale-free architectural connectivity gives rise to a scale-free pulse-rate distribution. We identify the scaling of the pairwise coupling between the dynamical units in this network class that keeps their pulse rates bounded in the infinite-network limit. In the process, we determine the connectivity statistics for a specific scale-free network grown by preferential attachment.

  16. Characterizing and Modeling the Noise and Complex Impedance of Feedhorn-Coupled TES Polarimeters

    SciTech Connect

    Appel, J. W.; Beall, J. A.; Essinger-Hileman, T.; Parker, L. P.; Staggs, S. T.; Visnjic, C.; Zhao, Y.; Austermann, J. E.; Halverson, N. W.; Henning, J. W.; Simon, S. M.; Becker, D.; Britton, J.; Cho, H. M.; Hilton, G. C.; Irwin, K. D.; Niemack, M. D.; Yoon, K. W.; Benson, B. A.; Bleem, L. E.

    2009-12-16

    We present results from modeling the electrothermal performance of feedhorn-coupled transition edge sensor (TES) polarimeters under development for use in cosmic microwave background (CMB) polarization experiments. Each polarimeter couples radiation from a corrugated feedhorn through a planar orthomode transducer, which transmits power from orthogonal polarization modes to two TES bolometers. We model our TES with two- and three-block thermal architectures. We fit the complex impedance data at multiple points in the TES transition. From the fits, we predict the noise spectra. We present comparisons of these predictions to the data for two TESes on a prototype polarimeter.

  17. anQCD: Fortran programs for couplings at complex momenta in various analytic QCD models

    NASA Astrophysics Data System (ADS)

    Ayala, César; Cvetič, Gorazd

    2016-02-01

    We provide three Fortran programs which evaluate the QCD analytic (holomorphic) couplings Aν(Q2) for complex or real squared momenta Q2. These couplings are holomorphic analogs of the powers a(Q2)ν of the underlying perturbative QCD (pQCD) coupling a(Q2) ≡αs(Q2) / π, in three analytic QCD models (anQCD): Fractional Analytic Perturbation Theory (FAPT), Two-delta analytic QCD (2 δanQCD), and Massive Perturbation Theory (MPT). The index ν can be noninteger. The provided programs do basically the same job as the Mathematica package anQCD.m published by us previously (Ayala and Cvetič, 2015), but are now written in Fortran.

  18. Functional modules and structural basis of conformational coupling in mitochondrial complex I.

    PubMed

    Hunte, Carola; Zickermann, Volker; Brandt, Ulrich

    2010-07-23

    Proton-pumping respiratory complex I is one of the largest and most complicated membrane protein complexes. Its function is critical for efficient energy supply in aerobic cells, and malfunctions are implicated in many neurodegenerative disorders. Here, we report an x-ray crystallographic analysis of mitochondrial complex I. The positions of all iron-sulfur clusters relative to the membrane arm were determined in the complete enzyme complex. The ubiquinone reduction site resides close to 30 angstroms above the membrane domain. The arrangement of functional modules suggests conformational coupling of redox chemistry with proton pumping and essentially excludes direct mechanisms. We suggest that a approximately 60-angstrom-long helical transmission element is critical for transducing conformational energy to proton-pumping elements in the distal module of the membrane arm.

  19. Coupling of PAK-interacting exchange factor PIX to GIT1 promotes focal complex disassembly.

    PubMed

    Zhao, Z S; Manser, E; Loo, T H; Lim, L

    2000-09-01

    The p21-activated kinase PAK is targeted to focal complexes (FCs) through interactions with the SH3 domains of the PAK-interacting exchange factor PIX and Nck. PIX is a Rac GTP exchange factor that also binds the G-protein-coupled receptor kinase-interacting protein known as GIT1. Overexpression of GIT1 in fibroblasts or epithelial cells causes a loss of paxillin from FCs and stimulates cell motility. This is due to the direct interaction of a C-terminal 125-residue domain of GIT1 with paxillin, under the regulation of PIX. In its activated state, GIT1 can promote FC disassembly independent of actin-myosin contractile events. Additionally, GIT directly couples to a key component of FCs, focal adhesion kinase (FAK), via a conserved Spa2 homology domain. We propose that GIT1 and FAK cooperate to promote motility both by directly regulating focal complex dynamics and by the activation of Rac.

  20. Experimental Verification of Coupled Stiffness Matrix in Multilayer Composite Structure with Complex Curvature

    NASA Astrophysics Data System (ADS)

    Jang, Jun Hwan; Kim, Jae Hoon

    The paper presents an experimental verification for calculating coupled stiffness matrix in complex curvature composite structure. The results of the analytical procedure using Variational Asymptotic Beam Sectional Analysis also indicate that the calculation of 2-D, beam, cross-sectional properties can then be incorporated into and 1-D beam analysis expressed coupled stiffness matrix. This paper presents the 2-D cross-sectional analysis of active anisotropic beams. Comparison between the analytical and experimental results shows that the proposed analytical procedure can provide an accurate and efficient prediction of the both deflection and flexural stiffness of multilayer composite slender structure. Verified comparison results can be used to efficiently design accurate complex slender structure properties for preliminary design and optimization.

  1. Boson stars in a theory of complex scalar field coupled to gravity

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjeev; Kulshreshtha, Usha; Kulshreshtha, Daya Shankar

    2015-07-01

    We study boson stars in a theory of complex scalar field coupled to Einstein gravity with the potential: (where and are positive constant parameters). This could be considered either as a theory of massive complex scalar field coupled to gravity in a conical potential or as a theory in the presence of a potential which is an overlap of a parabolic and a conical potential. We study our theory with positive as well as negative values of the cosmological constant . Boson stars are found to come in two types, having either ball-like or shell-like charge density. We have studied the properties of these solutions and have also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Hartmann, Kleihaus, Kunz, and Schaffer, in a V-shaped scalar potential.

  2. Robust projective outer synchronization of coupled uncertain fractional-order complex networks

    NASA Astrophysics Data System (ADS)

    Wang, Junwei; Zhang, Yun

    2013-06-01

    In this work, we propose a novel projective outer synchronization (POS) between unidirectionally coupled uncertain fractional-order complex networks through scalar transmitted signals. Based on the state observer theory, a control law is designed and some criteria are given in terms of linear matrix inequalities which guarantee global robust POS between such networks. Interestingly, in the POS regime, we show that different choices of scaling factor give rise to different outer synchrony, with various special cases including complete outer synchrony, anti-outer synchrony and even a state of amplitude death. Furthermore, it is demonstrated that although stability of POS is irrelevant to the inner-coupling strength, it will affect the convergence speed of POS. In particular, stronger inner synchronization can induce faster POS. The effectiveness of our method is revealed by numerical simulations on fractional-order complex networks with small-world communication topology.

  3. Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexes.

    PubMed

    Camasso, Nicole M; Sanford, Melanie S

    2015-03-13

    Homogeneous nickel catalysis is used for the synthesis of pharmaceuticals, natural products, and polymers. These reactions generally proceed via nickel intermediates in the Ni(0), Ni(I), Ni(II), and/or Ni(III) oxidation states. In contrast, Ni(IV) intermediates are rarely accessible. We report herein the design, synthesis, and characterization of a series of organometallic Ni(IV) complexes, accessed by the reaction of Ni(II) precursors with the widely used oxidant S-(trifluoromethyl)dibenzothiophenium triflate. These Ni(IV) complexes undergo highly selective carbon(sp(3))-oxygen, carbon(sp(3))-nitrogen, and carbon(sp(3))-sulfur coupling reactions with exogenous nucleophiles. The observed reactivity has the potential for direct applications in the development of nickel-catalyzed carbon-heteroatom coupling reactions.

  4. Tm(iii) complexes undergoing slow relaxation of magnetization: exchange coupling and aging effects.

    PubMed

    Amjad, A; Figuerola, A; Sorace, L

    2017-03-21

    The present study focuses on the dynamic magnetic behaviour of exchange coupled 3d-4f complexes containing the scarcely investigated non-Kramers Tm(3+) center, the 3d metal ions being either the low-spin Fe(3+) (1) or the diamagnetic Co(3+) (2) ion. Both complexes display field-induced slow relaxation of magnetization. The field and temperature dependences of the relaxation rate provided indication of relevant contributions from quantum tunnelling, direct, Orbach and Raman processes, with only minor effects from exchange coupling interactions. Furthermore, the aged sample of 2 exhibited an additional relaxation process, possibly due to structural modifications accompanied by solvent loss, highlighting the importance of a careful consideration of this factor when analysing the magnetization dynamics in solvated systems.

  5. Comment on the relation between the nonadiabatic coupling and the complex intersection of potential energy curves

    NASA Technical Reports Server (NTRS)

    Jaffe, R. L.

    1977-01-01

    Simple relations are discussed that provide a correspondence between the complex intersection of two potential surfaces and the nonadiabatic coupling matrix element between those surfaces. These are key quantities in semiclassical and quantum-mechanical theories of collision-induced electronic transitions. Within the two-state approximation, the complex intersection is shown to be directly related to the location and magnitude of the peak in the nonadiabatic coupling. Two cases have been considered: (1) the avoided crossing between two potential surfaces, and (2) the spin-orbit interaction due to a 2P halogen atom. Comparisons are made between the results of the two-state model and the results of ab initio quantum chemical calculations.

  6. Soliton dynamics to the multi-component complex coupled integrable dispersionless equation

    NASA Astrophysics Data System (ADS)

    Xu, Zong-Wei; Yu, Guo-Fu; Zhu, Zuo-Nong

    2016-11-01

    The generalized coupled integrable dispersionless (CID) equation describes the current-fed string in a certain external magnetic field. In this paper, we propose a multi-component complex CID equation. The integrability of the multi-component complex equation is confirmed by constructing Lax pairs. One-soliton and two-soliton solutions are investigated to exhibit rich evolution properties. Especially, similar as the multi-component short pulse equation and the first negative AKNS equation, periodic interaction, parallel solitons, elastic and inelastic interaction, energy re-distribution happen between two solitons. Multi-soliton solutions are given in terms of Pfaffian expression by virtue of Hirota's bilinear method.

  7. Oxidative Addition Complexes as Precatalysts for Cross-Coupling Reactions Requiring Extremely Bulky Biarylphosphine Ligands.

    PubMed

    Ingoglia, Bryan T; Buchwald, Stephen L

    2017-06-02

    In this report, we describe the application of palladium-based oxidative addition complexes (OACs) as effective precatalysts for C-N, C-O, and C-F cross-coupling reactions with a variety of (hetero)arenes. These complexes offer a convenient alternative to previously developed classes of precatalysts, particularly in the case of the bulkiest biarylphosphine ligands, for which palladacycle-based precatalysts do not readily form. The precatalysts described herein are easily prepared and stable to long-term storage under air.

  8. Noise-Coupled Image Rejection Architecture of Complex Bandpass ΔΣAD Modulator

    NASA Astrophysics Data System (ADS)

    San, Hao; Kobayashi, Haruo

    This paper proposes a new realization technique of image rejection function by noise-coupling architecture, which is used for a complex bandpass ΔΣAD modulator. The complex bandpass ΔΣAD modulator processes just input I and Q signals, not image signals, and the AD conversion can be realized with low power dissipation. It realizes an asymmetric noise-shaped spectra, which is desirable for such low-IF receiver applications. However, the performance of the complex bandpass ΔΣAD modulator suffers from the mismatch between internal analog I and Q paths. I/Q path mismatch causes an image signal, and the quantization noise of the mirror image band aliases into the desired signal band, which degrades the SQNDR (Signal to Quantization Noise and Distortion Ratio) of the modulator. In our proposed modulator architecture, an extra notch for image rejection is realized by noise-coupled topology. We just add some passive capacitors and switches to the modulator; the additional integrator circuit composed of an operational amplifier in the conventional image rejection realization is not necessary. Therefore, the performance of the complex modulator can be effectively raised without additional power dissipation. We have performed simulation with MATLAB to confirm the validity of the proposed architecture. The simulation results show that the proposed architecture can achieve the realization of image-rejection effectively, and improve the SQNDR of the complex bandpass ΔΣAD modulator.

  9. Assessing spatial coupling in complex population dynamics using mutual prediction and continuity statistics

    USGS Publications Warehouse

    Nichols, J.M.; Moniz, L.; Nichols, J.D.; Pecora, L.M.; Cooch, E.

    2005-01-01

    A number of important questions in ecology involve the possibility of interactions or ?coupling? among potential components of ecological systems. The basic question of whether two components are coupled (exhibit dynamical interdependence) is relevant to investigations of movement of animals over space, population regulation, food webs and trophic interactions, and is also useful in the design of monitoring programs. For example, in spatially extended systems, coupling among populations in different locations implies the existence of redundant information in the system and the possibility of exploiting this redundancy in the development of spatial sampling designs. One approach to the identification of coupling involves study of the purported mechanisms linking system components. Another approach is based on time series of two potential components of the same system and, in previous ecological work, has relied on linear cross-correlation analysis. Here we present two different attractor-based approaches, continuity and mutual prediction, for determining the degree to which two population time series (e.g., at different spatial locations) are coupled. Both approaches are demonstrated on a one-dimensional predator?prey model system exhibiting complex dynamics. Of particular interest is the spatial asymmetry introduced into the model as linearly declining resource for the prey over the domain of the spatial coordinate. Results from these approaches are then compared to the more standard cross-correlation analysis. In contrast to cross-correlation, both continuity and mutual prediction are clearly able to discern the asymmetry in the flow of information through this system.

  10. Flexible simulation framework to couple processes in complex 3D models for subsurface utilization assessment

    NASA Astrophysics Data System (ADS)

    Kempka, Thomas; Nakaten, Benjamin; De Lucia, Marco; Nakaten, Natalie; Otto, Christopher; Pohl, Maik; Tillner, Elena; Kühn, Michael

    2016-04-01

    Utilization of the geological subsurface for production and storage of hydrocarbons, chemical energy and heat as well as for waste disposal requires the quantification and mitigation of environmental impacts as well as the improvement of georesources utilization in terms of efficiency and sustainability. The development of tools for coupled process simulations is essential to tackle these challenges, since reliable assessments are only feasible by integrative numerical computations. Coupled processes at reservoir to regional scale determine the behaviour of reservoirs, faults and caprocks, generally demanding for complex 3D geological models to be considered besides available monitoring and experimenting data in coupled numerical simulations. We have been developing a flexible numerical simulation framework that provides efficient workflows for integrating the required data and software packages to carry out coupled process simulations considering, e.g., multiphase fluid flow, geomechanics, geochemistry and heat. Simulation results are stored in structured data formats to allow for an integrated 3D visualization and result interpretation as well as data archiving and its provision to collaborators. The main benefits in using the flexible simulation framework are the integration of data geological and grid data from any third party software package as well as data export to generic 3D visualization tools and archiving formats. The coupling of the required process simulators in time and space is feasible, while different spatial dimensions in the coupled simulations can be integrated, e.g., 0D batch with 3D dynamic simulations. User interaction is established via high-level programming languages, while computational efficiency is achieved by using low-level programming languages. We present three case studies on the assessment of geological subsurface utilization based on different process coupling approaches and numerical simulations.

  11. Functional coupling from simple to complex cells in the visually driven cortical circuit.

    PubMed

    Yu, Jianing; Ferster, David

    2013-11-27

    In the classic model of the primary visual cortex, upper-layer complex cells are driven by feedforward inputs from layer 4 simple cells. Based on spike cross-correlation, previous in vivo work has suggested that this connection is strong and dense, with a high probability of connection (50%) and significant strength in connected pairs. A much sparser projection has been found in brain slices, however, with the probability of layer 4 cells connecting to layer 2/3 cells being relatively low (10%). Here, we explore this connection in vivo in the cat primary visual cortex by recording simultaneously spikes of layer 4 simple cells and the membrane potential (V(m)) of layer 2/3 complex cells. By triggering the average of the complex cell's V(m) on the spikes of the simple cell (V(m)-STA), we found functional coupling to be very common during visual stimulation: the simple cell's spikes tended to occur near the troughs of the complex cell's V(m) fluctuations and were, on average, followed by a significant (~1 mV) fast-rising (10 ms) depolarization in the complex cell. In the absence of visual stimulation, however, when single simple cells were activated electrically through the recording electrode, no significant depolarization, or at most a very weak input (0.1-0.2 mV), was detected in the complex cell. We suggest that the functional coupling observed during visual stimulation arises from coordinated or nearly synchronous activity among a large population of simple cells, only a small fraction of which are presynaptic to the recorded complex cell.

  12. Studying Arsenite-Humic Acid Complexation Using Size Exclusion Chromatography-Inductively Coupled Plasma Mass Spectrometry

    PubMed Central

    Liu, Guangliang; Cai, Yong

    2012-01-01

    Arsenic (As) can form complexes with dissolved organic matter (DOM), which affects the fate of arsenic in waste sites and natural environments. It remains a challenge to analyze DOM-bound As, in particular by using a direct chromatographic separation method. Size exclusion chromatography (SEC) hyphenated with UV spectrophotometer and inductively coupled plasma mass spectrometry (ICP-MS) was developed to characterize the complexation of arsenite (AsIII) with DOM. This SEC-UV-ICP-MS method is able to differentiate AsIII-DOM complexes from free As species and has the advantage of direct determination of both free and DOM-bound AsIII through mild separation. The suitability of this method for studying AsIII-DOM complexation was demonstrated by its application, in combination with the Scatchard plot and nonlinear regression of ligand binding model, for characterizing AsIII complexation with humic acid (HA) in the absence or presence of natural sand. The results suggest that, consistent with polyelectrolytic nature of HA, the AsIII-HA complexation should be accounted for by multiple classes of binding sites. By loosely classifying the binding sites into strong (S1) and weak (S2) sites, the apparent stability constants (Ks) of the resulting As-DOM complexes were calculated as log Ks1 = 6.5–7.1 while log Ks2 = 4.7–5.0. PMID:22664255

  13. Robust synchronization of complex networks with uncertain couplings and incomplete information

    NASA Astrophysics Data System (ADS)

    Wang, Fan; Liang, Jinling; Wang, Zidong; Alsaadi, Fuad E.

    2016-07-01

    The mean square exponential (MSE) synchronization problem is investigated in this paper for complex networks with simultaneous presence of uncertain couplings and incomplete information, which comprise both the randomly occurring delay and the randomly occurring non-linearities. The network considered is uncertain with time-varying stochastic couplings. The randomly occurring delay and non-linearities are modelled by two Bernoulli-distributed white sequences with known probabilities to better describe realistic complex networks. By utilizing the coordinate transformation, the addressed complex network can be exponentially synchronized in the mean square if the MSE stability of a transformed subsystem can be assured. The stability problem is studied firstly for the transformed subsystem based on the Lyapunov functional method. Then, an easy-to-verify sufficient criterion is established by further decomposing the transformed system, which embodies the joint impacts of the single-node dynamics, the network topology and the statistical quantities of the uncertainties on the synchronization of the complex network. Numerical examples are exploited to illustrate the effectiveness of the proposed methods.

  14. Cooperation-induced temporal complexity in networks of pulse-coupled units

    NASA Astrophysics Data System (ADS)

    Geneston, Elvis; Grigolini, Paolo

    2012-02-01

    We study a network of stochastic pulse-coupled units generating bursts with the same size distribution as the neuronal avalanches in mature cultured neurons, recently revealed by the experimental observation. We prove that in addition to this form of complexity this model yields a form of phase transition generating also temporal complexity. This means that the distance from two consecutive bursts fits the prescription of a Mittag-Leffler (ML) function renewal theory. There exists a critical value of the cooperation parameter at which this description applies to the whole time regime. By increasing the cooperation parameter the ML theory breaks down and the sequence of bursts tend to become periodic with the same intensity. We make the conjecture that the analysis of this model may shed light into the theoretical foundation of neuronal burst leaders and that the recently discovered principle of complexity management may be conveniently applied to the neuro-physiological processes that are properly described by this model.

  15. Coupling of Spin and Charge Ordering and Elastic Finescales in Complex Electronic Materials

    NASA Astrophysics Data System (ADS)

    Lookman, T.; Saxena, A.; Albers, R. C.; Bishop, A. R.; Shenoy, S. R.

    2000-03-01

    There has been an intense focus in the past decade on complex electronic/magnetic materials such as high temperature cuprate and bismuthate superconductors, colossal magnetoresistance manganites, martensitic (and shape memory) alloys, ferroelectric as well as relaxor titanates and zirconates. Various high-resolution microscopies probing spin, charge and lattice degrees of freedom have revealed new, intrinsically inhomogeneous phases, with complex multiscale patterning over hundreds of lattice spacings. We show that long-range anisotropic strain interactions arising from general elastic compatibility considerations, linking components of the strain tensor, can enable interfaces or atomic-scale defects, to induce global strain textures. Symmetry-allowed couplings between strains and electronic/magnetic variables can then generate effective strain-mediated long-range interactions between these variables. This provides a generic elastic mechanism for mutual multiscale texturing of spin, charge and microstructural variables in the above complex materials.

  16. Numerical simulation and analysis of complex patterns in a two-layer coupled reaction diffusion system

    NASA Astrophysics Data System (ADS)

    Li, Xin-Zheng; Bai, Zhan-Guo; Li, Yan; He, Ya-Feng; Zhao, Kun

    2015-04-01

    The resonance interaction between two modes is investigated using a two-layer coupled Brusselator model. When two different wavelength modes satisfy resonance conditions, new modes will appear, and a variety of superlattice patterns can be obtained in a short wavelength mode subsystem. We find that even though the wavenumbers of two Turing modes are fixed, the parameter changes have influences on wave intensity and pattern selection. When a hexagon pattern occurs in the short wavelength mode layer and a stripe pattern appears in the long wavelength mode layer, the Hopf instability may happen in a nonlinearly coupled model, and twinkling-eye hexagon and travelling hexagon patterns will be obtained. The symmetries of patterns resulting from the coupled modes may be different from those of their parents, such as the cluster hexagon pattern and square pattern. With the increase of perturbation and coupling intensity, the nonlinear system will convert between a static pattern and a dynamic pattern when the Turing instability and Hopf instability happen in the nonlinear system. Besides the wavenumber ratio and intensity ratio of the two different wavelength Turing modes, perturbation and coupling intensity play an important role in the pattern formation and selection. According to the simulation results, we find that two modes with different symmetries can also be in the spatial resonance under certain conditions, and complex patterns appear in the two-layer coupled reaction diffusion systems. Project supported by the National Natural Science Foundation of China (Grant No. 11247242), the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 51201057), and the Natural Science Foundation of Hebei Province, China (Grant No. A2014208171).

  17. Semiquinone Intermediates are involved in the Energy Coupling Mechanism of E. coli Complex I

    PubMed Central

    Narayanan, Madhavan; Leung, Steven A.; Inaba, Yuta; Elguindy, Mahmoud M.; Nakamaru-Ogiso, Eiko

    2015-01-01

    Complex I (NADH:quinone oxidoreductase) is central to cellular aerobic energy metabolism, and its deficiency is involved in many human mitochondrial diseases. Complex I translocates protons across the membrane using electron transfer energy. Semiquinone (SQ) intermediates appearing during catalysis are suggested to be key for the coupling mechanism in complex I. However, the existence of SQ has remained controversial due to the extreme difficulty in detecting unstable and low intensity SQ signals. Here, for the first time with E. coli complex I reconstituted in proteoliposomes, we successfully resolved and characterized three distinct SQ species by EPR. These species include: fast-relaxing SQ (SQNf) with P1/2 (half-saturation power level) > 50 mW and a wider linewidth (12.8 G); slow-relaxing SQ (SQNs) with P1/2 = 2–3 mW and a 10 G linewidth; and very slow-relaxing SQ (SQNvs) with P1/2 = ~ 0.1 mW and a 7.5 G linewidth. The SQNf signals completely disappeared in the presence of the uncoupler gramicidin D or squamotacin, a potent E. coli complex I inhibitor. The pH dependency of the SQNf signals correlated with the proton-pumping activities of complex I. The SQNs signals were insensitive to gramicidin D, but sensitive to squamotacin. The SQNvs signals were insensitive to both gramicidin D and squamotacin. Our deuterium exchange experiments suggested that SQNf is neutral, while SQNs and SQNvs are anion radicals. The SQNs signals were lost in the ΔNuoL mutant missing transporter module subunits NuoL and NuoM. The roles and relationships of the SQ intermediates in the coupling mechanism are discussed. PMID:25868873

  18. Inducing isolated-desynchronization states in complex network of coupled chaotic oscillators

    NASA Astrophysics Data System (ADS)

    Lin, Weijie; Li, Huiyan; Ying, Heping; Wang, Xingang

    2016-12-01

    In a recent study about chaos synchronization in complex networks [Nat. Commun. 5, 4079 (2014), 10.1038/ncomms5079], it is shown that a stable synchronous cluster may coexist with vast asynchronous nodes, resembling the phenomenon of a chimera state observed in a regular network of coupled periodic oscillators. Although of practical significance, this new type of state, namely, the isolated-desynchronization state, is hardly observed in practice due to its strict requirements on the network topology. Here, by the strategy of pinning coupling, we propose an effective method for inducing isolated-desynchronization states in symmetric networks of coupled chaotic oscillators. Theoretical analysis based on eigenvalue analysis shows that, by pinning a group of symmetric nodes in the network, there exists a critical pinning strength beyond which the group of pinned nodes can completely be synchronized while the unpinned nodes remain asynchronous. The feasibility and efficiency of the control method are verified by numerical simulations of both artificial and real-world complex networks with the numerical results in good agreement with the theoretical predictions.

  19. Complex dynamics analysis of impulsively coupled Duffing oscillators with ring structure

    NASA Astrophysics Data System (ADS)

    Jiang, Hai-Bo; Zhang, Li-Ping; Yu, Jian-Jiang

    2015-02-01

    Impulsively coupled systems are high-dimensional non-smooth systems that can exhibit rich and complex dynamics. This paper studies the complex dynamics of a non-smooth system which is unidirectionally impulsively coupled by three Duffing oscillators in a ring structure. By constructing a proper Poincaré map of the non-smooth system, an analytical expression of the Jacobian matrix of Poincaré map is given. Two-parameter Hopf bifurcation sets are obtained by combining the shooting method and the Runge-Kutta method. When the period is fixed and the coupling strength changes, the system undergoes stable, periodic, quasi-periodic, and hyper-chaotic solutions, etc. Floquet theory is used to study the stability of the periodic solutions of the system and their bifurcations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11402224, 11202180, 61273106, and 11171290), the Qing Lan Project of the Jiangsu Higher Educational Institutions of China, and the Jiangsu Overseas Research and Training Program for University Prominent Young and Middle-aged Teachers and Presidents.

  20. Major histocompatibility complex alleles, sexual responsivity, and unfaithfulness in romantic couples.

    PubMed

    Garver-Apgar, Christine E; Gangestad, Steven W; Thornhill, Randy; Miller, Robert D; Olp, Jon J

    2006-10-01

    Preferences for mates that possess genes dissimilar to one's own at the major histocompatibility complex (MHC), a polymorphic group of loci associated with the immune system, have been found in mice, birds, fish, and humans. These preferences may help individuals choose genetically compatible mates and may adaptively function to prevent inbreeding or to increase heterozygosity and thereby immunocompetence of offspring. MHC-dissimilar mate preferences may influence the psychology of sexual attraction. We investigated whether MHC similarity among romantically involved couples (N= 48) predicted aspects of their sexual relationship. All women in our sample normally ovulated, and alleles at three MHC loci were typed for each person. As the proportion of MHC alleles couples shared increased, women's sexual responsivity to their partners decreased, their number of extrapair sexual partners increased, and their attraction to men other than their primary partners increased, particularly during the fertile phase of their cycles.

  1. Measurements of complex coupling coefficients in a ring resonator of a laser gyroscope

    NASA Astrophysics Data System (ADS)

    Bessonov, A. S.; Makeev, A. P.; Petrukhin, E. A.

    2017-07-01

    A method is proposed for measuring complex coupling coefficients in a ring optical resonator in the absence of an active gas mixture. A setup is described on which measurements are performed in ring resonators of ring He-Ne lasers with a wavelength of 632.8 nm. A model of backscattering field interference between conservative and dissipative sources is presented. Within the framework of this model, the unusual behaviour of backscattering fields in ring resonators observed in experiments is explained: a significant difference in the moduli of coupling coefficients of counterpropagating waves and variation of the magnitude of the total phase shift in a wide range. It is proposed to use this method as a metrological method when assembling and aligning a ring resonator of a laser gyroscope.

  2. The Ndc80 complex uses a tripartite attachment point to couple microtubule depolymerization to chromosome movement.

    PubMed

    Tooley, John G; Miller, Stephanie A; Stukenberg, P Todd

    2011-04-15

    In kinetochores, the Ndc80 complex couples the energy in a depolymerizing microtubule to perform the work of moving chromosomes. The complex directly binds microtubules using an unstructured, positively charged N-terminal tail located on Hec1/Ndc80. Hec1/Ndc80 also contains a calponin homology domain (CHD) that increases its affinity for microtubules in vitro, yet whether it is required in cells and how the tail and CHD work together are critical unanswered questions. Human kinetochores containing Hec1/Ndc80 with point mutations in the CHD fail to align chromosomes or form productive microtubule attachments. Kinetochore architecture and spindle checkpoint protein recruitment are unaffected in these mutants, and the loss of CHD function cannot be rescued by removing Aurora B sites from the tail. The interaction between the Hec1/Ndc80 CHD and a microtubule is facilitated by positively charged amino acids on two separate regions of the CHD, and both are required for kinetochores to make stable attachments to microtubules. Chromosome congression in cells also requires positive charge on the Hec1 tail to facilitate microtubule contact. In vitro binding data suggest that charge on the tail regulates attachment by directly increasing microtubule affinity as well as driving cooperative binding of the CHD. These data argue that in vertebrates there is a tripartite attachment point facilitating the interaction between Hec1/Ndc80 and microtubules. We discuss how such a complex microtubule-binding interface may facilitate the coupling of depolymerization to chromosome movement.

  3. Proton coupled electron transfer from the excited state of a ruthenium(II) pyridylimidazole complex.

    PubMed

    Pannwitz, Andrea; Wenger, Oliver S

    2016-04-28

    Proton coupled electron transfer (PCET) from the excited state of [Ru(bpy)2pyimH](2+) (bpy = 2,2'-bipyridine; pyimH = 2-(2'-pyridyl)imidazole) to N-methyl-4,4'-bipyridinium (monoquat, MQ(+)) was studied. While this complex has been investigated previously, our study is the first to show that the formal bond dissociation free energy (BDFE) of the imidazole-N-H bond decreases from (91 ± 1) kcal mol(-1) in the electronic ground state to (43 ± 5) kcal mol(-1) in the lowest-energetic (3)MLCT excited state. This makes the [Ru(bpy)2pyimH](2+) complex a very strong (formal) hydrogen atom donor even when compared to metal hydride complexes, and this is interesting for light-driven (formal) hydrogen atom transfer (HAT) reactions with a variety of different substrates. Mechanistically, formal HAT between (3)MLCT excited [Ru(bpy)2pyimH](2+) and monoquat in buffered 1 : 1 (v : v) CH3CN/H2O was found to occur via a sequence of reaction steps involving electron transfer from Ru(ii) to MQ(+) coupled to release of the N-H proton to buffer base, followed by protonation of reduced MQ(+) by buffer acid. Our study is relevant in the larger contexts of photoredox catalysis and light-to-chemical energy conversion.

  4. Substrate-Na{sup +} complex formation: Coupling mechanism for {gamma}-aminobutyrate symporters

    SciTech Connect

    Pallo, Anna; Simon, Agnes; Bencsura, Akos; Heja, Laszlo; Kardos, Julianna

    2009-07-24

    Crystal structures of transmembrane transport proteins belonging to the important families of neurotransmitter-sodium symporters reveal how they transport neurotransmitters across membranes. Substrate-induced structural conformations of gated neurotransmitter-sodium symporters have been in the focus of research, however, a key question concerning the mechanism of Na{sup +} ion coupling remained unanswered. Homology models of human glial transporter subtypes of the major inhibitory neurotransmitter {gamma}-aminobutyric acid were built. In accordance with selectivity data for subtype 2 vs. 3, docking and molecular dynamics calculations suggest similar orthosteric substrate (inhibitor) conformations and binding crevices but distinguishable allosteric Zn{sup 2+} ion binding motifs. Considering the occluded conformational states of glial human {gamma}-aminobutyric acid transporter subtypes, we found major semi-extended and minor ring-like conformations of zwitterionic {gamma}-aminobutyric acid in complex with Na{sup +} ion. The existence of the minor ring-like conformation of {gamma}-aminobutyric acid in complex with Na{sup +} ion may be attributed to the strengthening of the intramolecular H-bond by the electrostatic effect of Na{sup +} ion. Coupling substrate uptake into cells with the thermodynamically favorable Na{sup +} ion movement through substrate-Na{sup +} ion complex formation may be a mechanistic principle featuring transmembrane neurotransmitter-sodium symporter proteins.

  5. Approximate reconstruction of continuous spatially complex domain motions by multialignment NMR residual dipolar couplings.

    PubMed

    Fisher, Charles K; Al-Hashimi, Hashim M

    2009-05-07

    NMR spectroscopy is one of the most powerful techniques for studying the internal dynamics of biomolecules. Current formalisms approximate the dynamics using simple continuous motional models or models involving discrete jumps between a small number of states. However, no approach currently exists for interpreting NMR data in terms of continuous spatially complex motional paths that may feature more than one distinct maneuver. Here, we present an approach for approximately reconstructing spatially complex continuous motions of chiral domains using NMR anisotropic interactions. The key is to express Wigner matrix elements, which can be determined experimentally using residual dipolar couplings, as a line integral over a curve in configuration space containing an ensemble of conformations and to approximate the curve using a series of geodesic segments. Using this approach and five sets of synthetic residual dipolar couplings computed for five linearly independent alignment conditions, we show that it is theoretically possible to reconstruct salient features of a multisegment interhelical motional trajectory obtained from a 65 ns molecular dynamics simulation of a stem-loop RNA. Our study shows that the 3-D atomic reconstruction of complex motions in biomolecules is within experimental reach.

  6. Molecular basis of coupled protein and electron transfer dynamics of cytochrome c in biomimetic complexes.

    PubMed

    Alvarez-Paggi, Damián; Martín, Diego F; DeBiase, Pablo M; Hildebrandt, Peter; Martí, Marcelo A; Murgida, Daniel H

    2010-04-28

    Direct electron transfer (ET) of redox proteins immobilized on biomimetic or biocompatible electrodes represents an active field of fundamental and applied research. In this context, several groups have reported for a variety of proteins unexpected distance dependencies of the ET rate, whose origin remains largely speculative and controversial, but appears to be a quite general phenomenon. Here we have employed molecular dynamics (MD) simulations and electron pathway analyses to study the ET properties of cytochrome c (Cyt) electrostatically immobilized on Au coated by carboxyl-terminated alkylthiols. The MD simulations and concomitant binding energy calculations allow identification of preferred binding configurations of the oxidized and reduced Cyt which are established via different lysine residues and, thus, correspond to different orientations and dipole moments. Calculations of the electronic coupling matrices for the various Cyt/self-assembled monolayer (SAM) complexes indicate that the thermodynamically preferred protein orientations do not coincide with the orientations of optimum coupling. These findings demonstrate that the ET of the immobilized Cyt is controlled by an interplay between protein dynamics and tunneling probabilities. Protein dynamics exerts two level of tuning on the electronic coupling via reorientation (coarse) and low amplitude thermal fluctuations (fine). Upon operating the Au support as an electrode, electric-field-dependent alignment of the protein dipole moment becomes an additional determinant for the protein dynamics and thus for the overall ET rate. The present results provide a consistent molecular description of previous (spectro)electrochemical data and allow conclusions concerning the coupling of protein dynamics and ET of Cyt in physiological complexes.

  7. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  8. Coupled variable selection for regression modeling of complex treatment patterns in a clinical cancer registry.

    PubMed

    Schmidtmann, I; Elsäßer, A; Weinmann, A; Binder, H

    2014-12-30

    For determining a manageable set of covariates potentially influential with respect to a time-to-event endpoint, Cox proportional hazards models can be combined with variable selection techniques, such as stepwise forward selection or backward elimination based on p-values, or regularized regression techniques such as component-wise boosting. Cox regression models have also been adapted for dealing with more complex event patterns, for example, for competing risks settings with separate, cause-specific hazard models for each event type, or for determining the prognostic effect pattern of a variable over different landmark times, with one conditional survival model for each landmark. Motivated by a clinical cancer registry application, where complex event patterns have to be dealt with and variable selection is needed at the same time, we propose a general approach for linking variable selection between several Cox models. Specifically, we combine score statistics for each covariate across models by Fisher's method as a basis for variable selection. This principle is implemented for a stepwise forward selection approach as well as for a regularized regression technique. In an application to data from hepatocellular carcinoma patients, the coupled stepwise approach is seen to facilitate joint interpretation of the different cause-specific Cox models. In conditional survival models at landmark times, which address updates of prediction as time progresses and both treatment and other potential explanatory variables may change, the coupled regularized regression approach identifies potentially important, stably selected covariates together with their effect time pattern, despite having only a small number of events. These results highlight the promise of the proposed approach for coupling variable selection between Cox models, which is particularly relevant for modeling for clinical cancer registries with their complex event patterns. Copyright © 2014 John Wiley & Sons

  9. Analytical modeling provides new insight into complex mutual coupling between surface loops at ultrahigh fields.

    PubMed

    Avdievich, N I; Pfrommer, A; Giapitzakis, I A; Henning, A

    2017-10-01

    Ultrahigh-field (UHF) (≥7 T) transmit (Tx) human head surface loop phased arrays improve both the Tx efficiency (B1(+) /√P) and homogeneity in comparison with single-channel quadrature Tx volume coils. For multi-channel arrays, decoupling becomes one of the major problems during the design process. Further insight into the coupling between array elements and its dependence on various factors can facilitate array development. The evaluation of the entire impedance matrix Z for an array loaded with a realistic voxel model or phantom is a time-consuming procedure when performed using electromagnetic (EM) solvers. This motivates the development of an analytical model, which could provide a quick assessment of the Z-matrix. In this work, an analytical model based on dyadic Green's functions was developed and validated using an EM solver and bench measurements. The model evaluates the complex coupling, including both the electric (mutual resistance) and magnetic (mutual inductance) coupling. Validation demonstrated that the model does well to describe the coupling at lower fields (≤3 T). At UHFs, the model also performs well for a practical case of low magnetic coupling. Based on the modeling, the geometry of a 400-MHz, two-loop transceiver array was optimized, such that, by simply overlapping the loops, both the mutual inductance and the mutual resistance were compensated at the same time. As a result, excellent decoupling (below -40 dB) was obtained without any additional decoupling circuits. An overlapped array prototype was compared (signal-to-noise ratio, Tx efficiency) favorably to a gapped array, a geometry which has been utilized previously in designs of UHF Tx arrays. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Ferromagnetic vs antiferromagnetic coupling in bis(mu-phenoxo)dicopper(II) complexes. Tuning of the nature of exchange coupling by remote ligand substituents.

    PubMed

    Chaudhuri, Phalguni; Wagner, Rita; Weyhermüller, Thomas

    2007-06-25

    Two bis(mu-phenoxo)dicopper(II) complexes, [(L(CH3))(2)Cu(2)] (1) and [(L(t-Bu))(2)Cu(2)] (2), where L(CH3) and L(t-Bu) represent the dianions of (methylamino)-N,N-bis(2-methylene-4,6-dimethylphenol) and of (methylamino)-N,N-bis(2-methylene-4,6-di-tert-butylphenol), respectively, are reported to demonstrate the effect of remote substituents on the nature of exchange coupling interactions between the copper(II) centers. In contrast to 1, which is as usual antiferromagnetically coupled, complex 2 is a rare example of a ferromagnetically coupled diphenoxodicopper(II) complex.

  11. Complexity and bandwidth enhancement in unidirectionally coupled semiconductor lasers with time-delayed optical feedback

    NASA Astrophysics Data System (ADS)

    Kanno, Kazutaka; Uchida, Atsushi; Bunsen, Masatoshi

    2016-03-01

    We numerically investigate the frequency bandwidth and the autocorrelation characteristics of chaotic temporal wave forms in unidirectionally coupled semiconductor lasers with time-delayed optical feedback. We evaluate the complexity of the chaotic temporal wave forms by using Lyapunov exponents. We found that larger maximum Lyapunov exponents can be obtained for smaller peak values of the autocorrelation function at the delay time of the optical feedback. On the contrary, the maximum Lyapunov exponent is independent from the frequency bandwidth of the chaotic temporal wave forms.

  12. Coexistence of Regular and Irregular Dynamics in Complex Networks of Pulse-Coupled Oscillators

    NASA Astrophysics Data System (ADS)

    Timme, Marc; Wolf, Fred; Geisel, Theo

    2002-11-01

    For general networks of pulse-coupled oscillators, including regular, random, and more complex networks, we develop an exact stability analysis of synchronous states. As opposed to conventional stability analysis, here stability is determined by a multitude of linear operators. We treat this multioperator problem exactly and show that for inhibitory interactions the synchronous state is stable, independent of the parameters and the network connectivity. In randomly connected networks with strong interactions this synchronous state, displaying regular dynamics, coexists with a balanced state exhibiting irregular dynamics. External signals may switch the network between qualitatively distinct states.

  13. Communication: Analytic gradients for the complex absorbing potential equation-of-motion coupled-cluster method

    NASA Astrophysics Data System (ADS)

    Benda, Zsuzsanna; Jagau, Thomas-C.

    2017-01-01

    The general theory of analytic energy gradients is presented for the complex absorbing potential equation-of-motion coupled-cluster (CAP-EOM-CC) method together with an implementation within the singles and doubles approximation. Expressions for the CAP-EOM-CC energy gradient are derived based on a Lagrangian formalism with a special focus on the extra terms arising from the presence of the CAP. Our implementation allows for locating minima on high-dimensional complex-valued potential energy surfaces and thus enables geometry optimizations of resonance states of polyatomic molecules. The applicability of our CAP-EOM-CC gradients is illustrated by computations of the equilibrium structures and adiabatic electron affinities of the temporary anions of formaldehyde, formic acid, and ethylene. The results are compared to those obtained from standard EOM-CC calculations and the advantages of CAP methods are emphasized.

  14. Eigenfunction Expansions for Coupled Nonlinear Convection-Diffusion Problems in Complex Physical Domains

    NASA Astrophysics Data System (ADS)

    Cotta, R. M.; Naveira-Cotta, C. P.; Knupp, D. C.; Zotin, J. L. Z.; Pontes, P. C.

    2016-09-01

    This lecture offers an updated review on the Generalized Integral Transform Technique (GITT), with focus on handling complex geometries, coupled problems, and nonlinear convection-diffusion, so as to illustrate some new application paradigms. Special emphasis is given to demonstrating novel developments, such as a single domain reformulation strategy that simplifies the treatment of complex geometries, an integral balance scheme in handling multiscale problems, the adoption of convective eigenvalue problems in dealing with strongly convective formulations, and the direct integral transformation of nonlinear convection-diffusion problems based on nonlinear eigenvalue problems. Representative application examples are then provided that employ recent extensions on the Generalized Integral Transform Technique (GITT), and a few numerical results are reported to illustrate the convergence characteristics of the proposed eigenfunction expansions.

  15. Arsenic removal from water by coupling photocatalysis and complexation-ultrafiltration processes: A preliminary study.

    PubMed

    Molinari, R; Argurio, P

    2017-02-01

    Inorganic As removal from contaminated water has been studied by off-line coupling of photocatalysis and complexation-ultrafiltration (CP-UF), showing that this combination permits to obtain a quite complete arsenic removal from the treated water. Two commercial polymers, poly(dimethylamine-coepichlorohydrin-coethylenediamine) (PDEHED) and poly(diallyl dimethyl amnmonium chloride) (PolyDADMAC) have been tested in the CP-UF process. The operating conditions (pH and polymer/As weight ratio) for As(V) complexation were determined finding values of 7.5/20 and 9.2/30 for PDEHED and polyDADMAC, respectively. The UF tests were performed by continuous diafiltration and diafiltration with volume reduction modes. The latter method permits to save the volume of washing solution during polymer regeneration. As(III) was not complexed, operating under the As(V) complexation conditions, thus a pre-oxidation step by using the photocatalytic approach was carried out to remove As(III) species. As(III) conversion to As(V) was evaluated by As speciation by using the CP-UF process for analytical purposes. Photocatalytic oxidation was successfully performed under UV radiation by using TiO2 (0.05 mg L(-1)), O2 and pH = 9. The oxidation was very fast during the first 10 min following a zero order kinetics (k = 0.83 mg L(-1) min(-1)) and reaching 90% As(III) oxidation. A conceptual scheme coupling photocatalysis and CP-UF and some criteria to operate the CP-UF process, useful to address it towards application, are reported.

  16. Visualization of coupled protein folding and binding in bacteria and purification of the heterodimeric complex

    PubMed Central

    Wang, Haoyong; Chong, Shaorong

    2003-01-01

    During overexpression of recombinant proteins in Escherichia coli, misfolded proteins often aggregate and form inclusion bodies. If an aggregation-prone recombinant protein is fused upstream (as an N-terminal fusion) to GFP, aggregation of the recombinant protein domain also leads to misfolding of the downstream GFP domain, resulting in a decrease or loss of fluorescence. We investigated whether the GFP domain could fold correctly if aggregation of the upstream protein domain was prevented in vivo by a coupled protein folding and binding interaction. Such interaction has been previously shown to occur between the E. coli integration host factors α and β, and between the domains of the general transcriptional coactivator cAMP response element binding protein (CREB)-binding protein and the activator for thyroid hormone and retinoid receptors. In this study, fusion of integration host factor β or the CREB-binding protein domain upstream to GFP resulted in aggregation of the fusion protein. Coexpression of their respective partners, on the other hand, allowed soluble expression of the fusion protein and a dramatic increase in fluorescence. The study demonstrated that coupled protein folding and binding could be correlated to GFP fluorescence. A modified miniintein containing an affinity tag was inserted between the upstream protein domain and GFP to allow rapid purification and identification of the heterodimeric complex. The GFP coexpression fusion system may be used to identify novel protein–protein interactions that involve coupled folding and binding or protein partners that can solubilize aggregation-prone recombinant proteins. PMID:12515863

  17. Coupling of downstream RNA polymerase-promoter interactions with formation of catalytically competent transcription initiation complex

    PubMed Central

    Mekler, Vladimir; Minakhin, Leonid; Borukhov, Sergei; Mustaev, Arkady; Severinov, Konstantin

    2014-01-01

    Bacterial RNA polymerase (RNAP) makes extensive contacts with duplex DNA downstream of the transcription bubble in initiation and elongation complexes. We investigated the role of downstream interactions in formation of catalytically competent transcription initiation complex by measuring initiation activity of stable RNAP complexes with model promoter DNA fragments whose downstream ends extend from +3 to +21 relative to the transcription start site at +1. We found that DNA downstream of position +6 does not play a significant role in transcription initiation when RNAP-promoter interactions upstream of the transcription start site are strong and promoter melting region is AT-rich. Further shortening of downstream DNA dramatically reduces efficiency of transcription initiation. The boundary of minimal downstream DNA duplex needed for efficient transcription initiation shifted further away from the catalytic center upon increasing the GC content of promoter melting region or in the presence of bacterial stringent response regulators DksA and ppGpp. These results indicate that the strength of RNAP-downstream DNA interactions has to reach a certain threshold to retain the catalytically competent conformation of the initiation complex and that establishment of contacts between RNAP and downstream DNA can be coupled with promoter melting. The data further suggest that RNAP interactions with DNA immediately downstream of the transcription bubble are particularly important for initiation of transcription. We hypothesize that these active center-proximal contacts stabilize the DNA template strand in the active center cleft and/or position the RNAP clamp domain to allow RNA synthesis. PMID:25311862

  18. ATPase-coupled release control from polyion complex capsules encapsulating muscle proteins.

    PubMed

    Sugiura, Kousuke; Ohkawa, Kousaku; Hirai, Toshihiro; Fujii, Toshihiro

    2007-04-10

    In the present study, a muscle contractile protein complex, actomyosin, has been successfully encapsulated into gellan-chitosan polyion complex (PIC) capsules. The recovery of the myosin-ATPase activity is approximately 50% and the Mg2+-ATPase activity is stimulated by the presence of F-actin, which implies the formation of the actomyosin complex inside the capsule. Furthermore, encapsulation could protect the myosin, F-actin, and actomyosin inside from hydrolysis by proteases. Two small proteins, myoglobin and cytochrome c, have been used in the release tests. The release of myoglobin is not affected by the ionic strength of the external solution, while the release of cytochrome c increases with increasing ionic strength. The maximal releases are found in the external pH solution close to the isoelectric points of each protein. The Mg2+-ATP complex itself reduces the release percentages of the small proteins from the PIC capsule. The release amounts further decrease when coexisting with Mg2+-ATP and the encapsulated actomyosin, which indicates the release regulation by actomyosin. The present study suggests that the ATPase-coupled sliding motion of the myosin-F-actin filaments modifies the pore size of the polymer networks in the PIC capsule membranes.

  19. Heterobimetallic porphyrin complexes displaying triple dynamics: coupled metal motions controlled by constitutional evolution.

    PubMed

    Le Gac, Stéphane; Fusaro, Luca; Roisnel, Thierry; Boitrel, Bernard

    2014-05-07

    A bis-strap porphyrin ligand (1), with an overhanging carboxylic acid group on each side of the macrocycle, has been investigated toward the formation of dynamic libraries of bimetallic complexes with Hg(II), Cd(II), and Pb(II). Highly heteroselective metalation processes occurred in the presence of Pb(II), with Hg(II) or Cd(II) bound out-of-plane to the N-core and "PbOAc" bound to a carboxylate group of a strap on the opposite side. The resulting complexes, 1(Hg)·PbOAc and 1(Cd)·PbOAc, display three levels of dynamics. The first is strap-level (interactional dynamics), where the PbOAc moiety swings between the left and right side of the strap owing to a second sphere of coordination with lateral amide functions. The second is ligand-level (motional dynamics), where 1(Hg)·PbOAc and 1(Cd)·PbOAc exist as two degenerate states in equilibrium controlled by a chemical effector (AcO(-)). The process corresponds to a double translocation of the metal ions according to an intramolecular migration of Hg(II) or Cd(II) through the N-core, oscillating between the two equivalent overhanging carbonyl groups, coupled to an intermolecular pathway for PbOAc exchanging between the two equivalent overhanging carboxylate groups (N-core(up) ⇆ N-core(down) coupled to strap(down) ⇆ strap(up), i.e., coupled motion #1 in the abstract graphic). The third is library-level (constitutional dynamics), where a dynamic constitutional evolution of the system was achieved by the successive addition of two chemical effectors (DMAP and then AcO(-)). It allowed shifting equilibrium forward and backward between 1(Hg)·PbOAc and the corresponding homobimetallic complexes 1(Hg2)·DMAP and 1(Pb)·PbOAc. The latter displays a different ligand-level dynamics, in the form of an intraligand coupled migration of the Pb(II) ions (N-core(up) ⇆ strap(up) coupled to strap(down) ⇆ N-core(down), i.e., coupled motion #2 in the abstract graphic). In addition, the neutral "bridged" complexes 1HgPb and 1Cd

  20. Calculation of exchange coupling constants of transition metal complexes with DFT.

    PubMed

    Comba, Peter; Hausberg, Sascha; Martin, Bodo

    2009-06-18

    A broken-symmetry method for the calculation of exchange coupling constants from DFT calculations, using the Heisenberg-Dirac-van Vleck spin Hamiltonian, has been validated for a dinuclear copper(II) complex. Hybrid functionals in combination with a large basis set on the metal centers and their first coordination sphere, and a smaller basis set on the ligand backbone are shown to be efficient and acceptable with respect to the computational cost and precision in comparison with experimental data. This method was thoroughly tested with a series of oligonuclear transition metal complexes with Cr(III), Cu(II), Fe(III), Mn(II), Mn(III), Mn(IV), Ni(II), and V(IV) as magnetic centers. The computed values of J are within approximately 50 cm(-1) of the experimental values for most of the examples; with combined basis sets, there generally is a similar accuracy to that obtained with a large basis set for the entire spin cluster but with significantly reduced computational expense. When the experimentally observed structural data are refined prior to the calculation of the exchange coupling constants, the computed values of J are in most cases in slightly better agreement with the experimental data than those obtained from single point calculations based on the X-ray data.

  1. Mechanism of Coupled Folding and Binding in the siRNA-PAZ Complex.

    PubMed

    Chen, Hai-Feng

    2008-08-01

    The PAZ domain plays a key role in gene silencing pathway. The PAZ domain binds with siRNAs to form the multimeric RNA-induced silencing complex (RISC). RISC identifies mRNAs homologous to the siRNAs and promotes their degradation. It was found that binding with siRNA significantly enhances apo-PAZ folding. However, the mechanism by which folding is coupled to binding is poorly understood. Thus, the coupling relationship between binding and folding is very important for understanding the function of gene silencing. We have performed molecular dynamics (MD) of both bound and apo-PAZ to study the coupling mechanism between binding and folding in the siRNA-PAZ complex. Room-temperature MD simulations suggest that both PAZ and siRNA become more rigid and stable upon siRNA binding. Kinetic analysis of high-temperature MD simulations shows that both bound and apo-PAZ unfold via a two-state process. The unfolding pathways are different between bound and apo-PAZ: the order of helix III and helices I & II unfolding is switched. Furthermore, transition probability was used to determine the transition state ensemble for both bound and apo-PAZ. It was found that the transition state of bound PAZ is more compact than that of apo-PAZ. The predicted Φ-values suggest that the Φ-values of helix III and sheets of β3-β7 for bound PAZ are more native-like than those of apo-PAZ upon the binding of siRNA. The results can help us to understand the mechanism of gene silencing.

  2. Characterization of a multiprotein complex involved in excitation-transcription coupling of skeletal muscle.

    PubMed

    Arias-Calderón, Manuel; Almarza, Gonzalo; Díaz-Vegas, Alexis; Contreras-Ferrat, Ariel; Valladares, Denisse; Casas, Mariana; Toledo, Héctor; Jaimovich, Enrique; Buvinic, Sonja

    2016-01-01

    Electrical activity regulates the expression of skeletal muscle genes by a process known as "excitation-transcription" (E-T) coupling. We have demonstrated that release of adenosine 5'-triphosphate (ATP) during depolarization activates membrane P2X/P2Y receptors, being the fundamental mediators between electrical stimulation, slow intracellular calcium transients, and gene expression. We propose that this signaling pathway would require the proper coordination between the voltage sensor (dihydropyridine receptor, DHPR), pannexin 1 channels (Panx1, ATP release conduit), nucleotide receptors, and other signaling molecules. The goal of this study was to assess protein-protein interactions within the E-T machinery and to look for novel constituents in order to characterize the signaling complex. Newborn derived myotubes, adult fibers, or triad fractions from rat or mouse skeletal muscles were used. Co-immunoprecipitation, 2D blue native SDS/PAGE, confocal microscopy z-axis reconstruction, and proximity ligation assays were combined to assess the physical proximity of the putative complex interactors. An L6 cell line overexpressing Panx1 (L6-Panx1) was developed to study the influence of some of the complex interactors in modulation of gene expression. Panx1, DHPR, P2Y2 receptor (P2Y2R), and dystrophin co-immunoprecipitated in the different preparations assessed. 2D blue native SDS/PAGE showed that DHPR, Panx1, P2Y2R and caveolin-3 (Cav3) belong to the same multiprotein complex. We observed co-localization and protein-protein proximity between DHPR, Panx1, P2Y2R, and Cav3 in adult fibers and in the L6-Panx1 cell line. We found a very restricted location of Panx1 and Cav3 in a putative T-tubule zone near the sarcolemma, while DHPR was highly expressed all along the transverse (T)-tubule. By Panx1 overexpression, extracellular ATP levels were increased both at rest and after electrical stimulation. Basal mRNA levels of the early gene cfos and the oxidative metabolism

  3. Complex band structures of transition metal dichalcogenide monolayers with spin-orbit coupling effects

    NASA Astrophysics Data System (ADS)

    Szczęśniak, Dominik; Ennaoui, Ahmed; Ahzi, Saïd

    2016-09-01

    Recently, the transition metal dichalcogenides have attracted renewed attention due to the potential use of their low-dimensional forms in both nano- and opto-electronics. In such applications, the electronic and transport properties of monolayer transition metal dichalcogenides play a pivotal role. The present paper provides a new insight into these essential properties by studying the complex band structures of popular transition metal dichalcogenide monolayers (MX 2, where M  =  Mo, W; X  =  S, Se, Te) while including spin-orbit coupling effects. The conducted symmetry-based tight-binding calculations show that the analytical continuation from the real band structures to the complex momentum space leads to nonlinear generalized eigenvalue problems. Herein an efficient method for solving such a class of nonlinear problems is presented and yields a complete set of physically relevant eigenvalues. Solutions obtained by this method are characterized and classified into propagating and evanescent states, where the latter states manifest not only monotonic but also oscillatory decay character. It is observed that some of the oscillatory evanescent states create characteristic complex loops at the direct band gap of MX 2 monolayers, where electrons can directly tunnel between the band gap edges. To describe these tunneling currents, decay behavior of electronic states in the forbidden energy region is elucidated and their importance within the ballistic transport regime is briefly discussed.

  4. Vortex-soliton complexes in coupled nonlinear Schrödinger equations with unequal dispersion coefficients.

    PubMed

    Charalampidis, E G; Kevrekidis, P G; Frantzeskakis, D J; Malomed, B A

    2016-08-01

    We consider a two-component, two-dimensional nonlinear Schrödinger system with unequal dispersion coefficients and self-defocusing nonlinearities, chiefly with equal strengths of the self- and cross-interactions. In this setting, a natural waveform with a nonvanishing background in one component is a vortex, which induces an effective potential well in the second component, via the nonlinear coupling of the two components. We show that the potential well may support not only the fundamental bound state, but also multiring excited radial state complexes for suitable ranges of values of the dispersion coefficient of the second component. We systematically explore the existence, stability, and nonlinear dynamics of these states. The complexes involving the excited radial states are weakly unstable, with a growth rate depending on the dispersion of the second component. Their evolution leads to transformation of the multiring complexes into stable vortex-bright solitons ones with the fundamental state in the second component. The excited states may be stabilized by a harmonic-oscillator trapping potential, as well as by unequal strengths of the self- and cross-repulsive nonlinearities.

  5. Complex band structures of transition metal dichalcogenide monolayers with spin-orbit coupling effects.

    PubMed

    Szczęśniak, Dominik; Ennaoui, Ahmed; Ahzi, Saïd

    2016-09-07

    Recently, the transition metal dichalcogenides have attracted renewed attention due to the potential use of their low-dimensional forms in both nano- and opto-electronics. In such applications, the electronic and transport properties of monolayer transition metal dichalcogenides play a pivotal role. The present paper provides a new insight into these essential properties by studying the complex band structures of popular transition metal dichalcogenide monolayers (MX 2, where M  =  Mo, W; X  =  S, Se, Te) while including spin-orbit coupling effects. The conducted symmetry-based tight-binding calculations show that the analytical continuation from the real band structures to the complex momentum space leads to nonlinear generalized eigenvalue problems. Herein an efficient method for solving such a class of nonlinear problems is presented and yields a complete set of physically relevant eigenvalues. Solutions obtained by this method are characterized and classified into propagating and evanescent states, where the latter states manifest not only monotonic but also oscillatory decay character. It is observed that some of the oscillatory evanescent states create characteristic complex loops at the direct band gap of MX 2 monolayers, where electrons can directly tunnel between the band gap edges. To describe these tunneling currents, decay behavior of electronic states in the forbidden energy region is elucidated and their importance within the ballistic transport regime is briefly discussed.

  6. Investigating tunnel and above-barrier ionization using complex-scaled coupled-cluster theory

    NASA Astrophysics Data System (ADS)

    Jagau, Thomas-C.

    2016-11-01

    The theory and implementation of the complex-scaled coupled-cluster method with singles and doubles excitations (cs-CCSD) for studying resonances induced by static electric fields are presented. Within this framework, Stark shifts and ionization rates are obtained directly from the real and imaginary parts of the complex energy. The method is applied to the ground states of hydrogen, helium, lithium, beryllium, neon, argon, and carbon at varying field strengths. Complex-scaled Hartree-Fock, second-order many-body perturbation theory, and CCSD results are reported and analyzed with a focus on the impact of electron correlation on the ionization process. cs-CCSD calculations with suitably augmented standard Gaussian basis sets are found to deliver accurate strong-field ionization rates over a range of six orders of magnitude. The field-induced resonances are characterized beyond energy and ionization rate through their dipole moments, second moments, as well as Dyson orbitals and comparisons are drawn to autoionizing and autodetaching resonances. Marked differences are found between the tunneling and above-barrier regimes allowing for a clear distinction of the two mechanisms.

  7. Pentafluorophenyl imidato palladium(II) complexes: catalysts for Suzuki cross-coupling reactions.

    PubMed

    Ruiz, José; Vicente, Consuelo; Cutillas, Natalia; Pérez, José

    2005-06-07

    Novel N-bonded imidato complexes of general formula [Pd(N-N)(C6F5)(imidate)](imidate = maleimidate, succinimidate or phthalimidate; N-N = 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (Me2bipy) or N,N,N',N'-tetramethylethylenediamine (tmeda)), [NBu4][Pd(C6F5)(H2O)(succinimidate)2] and [NBu4][Pd(C6F5)(L)(succinimidate)2](L = PPh3 or t-BuNC) have been synthesised. These complexes are air-, light- and moisture-stable. The crystal structures of [Pd(tmeda)(C6F5)(maleimidate)].H2O.0.5CHCl3, [NBu4][Pd(C6F5)(H2O)(succinimidate)2].H2O and [NBu4][Pd(C6F5)(t-BuNC)(succinimidate)2].2H2O have been determined by X-ray diffraction. Many of these new complexes are shown to be active phosphine-free palladium catalysts/precatalysts for the Suzuki cross-coupling reactions of aryl bromides and aryl chlorides with phenylboronic acid.

  8. Coordination versus coupling of dicyanamide in molybdenum and manganese pyrazole complexes.

    PubMed

    Arroyo, Marta; Gómez-Iglesias, Patricia; Martín-Alvarez, Jose Miguel; Alvarez, Celedonio M; Miguel, Daniel; Villafañe, Fernando

    2012-06-04

    The reactions of cis-[MoCl(η(3)-methallyl)(CO)(2)(NCMe)(2)] (methallyl = CH(2)C(CH(3))CH(2)) with Na(NCNCN) and pz*H (pzH, pyrazole, or dmpzH, 3,5-dimethylpyrazole) lead to cis-[Mo(η(3)-methallyl)(CO)(2)(pz*H)(μ-NCNCN-κ(2)N,N)](2) (pzH, 1a; dmpzH, 1b), where dicyanamide is coordinated as bridging ligand. Similar reactions with fac-[MnBr(CO)(3)(NCMe)(2)] lead to the pyrazolylamidino complexes fac-[Mn(pz*H)(CO)(3)(NH═C(pz*)NCN-κ(2)N,N)] (pzH, 2a; dmpzH, 2b), resulting from the coupling of pyrazol with one of the CN bonds of dicyanamide. The second CN bond of dicyanamide in 2a undergoes a second coupling with pyrazole after addition of 1 equiv of fac-[MnBr(CO)(3)(pzH)(2)], yielding the dinuclear doubly coupled complex [{fac-Mn(pzH)(CO)(3)}(2)(μ-NH═C(pz)NC(pz)=NH-κ(4)N,N,N,N)]Br (3). The crystal structure of 3 reveals the presence of two isomers, cis or trans, depending on whether the terminal pyrazoles are coordinated at the same or at different sides of the approximate plane defined by the bridging bis-amidine ligand. Only the cis isomer is detected in the crystal structure of the perchlorate salt of the same bimetallic cation (4), obtained by metathesis with AgClO(4). All the N-bound hydrogen atoms of the cations in 3 or 4 are involved in hydrogen bonds. Some of the C-N bonds of the pyrazolylamidino ligand have a character intermediate between single and double, and theoretical studies were carried out on 2a and 3 to confirm its electronic origin and discard packing effects. Calculations also show the essential role of bromide in the planarity of the tetradentate ligand in the bimetallic complex 3.

  9. Bose-Einstein condensates with localized spin-orbit coupling: Soliton complexes and spinor dynamics

    NASA Astrophysics Data System (ADS)

    Kartashov, Yaroslav V.; Konotop, Vladimir V.; Zezyulin, Dmitry A.

    2014-12-01

    Spin-orbit (SO) coupling can be introduced in a Bose-Einstein condensate (BEC) as a gauge potential acting only in a localized spatial domain. The effect of such a SO "defect" can be understood by transforming the system to the integrable vector model. The properties of the SO BEC change drastically if the SO defect is accompanied by the Zeeman splitting. In such a nonintegrable system, the SO defect qualitatively changes the character of soliton interactions and allows for formation of stable nearly scalar soliton complexes with almost all atoms concentrated in only one dark state. These solitons exist only if the number of particles exceeds a threshold value. We also report on the possibility of transmission and reflection of a soliton upon its scattering on the SO defect. Scattering strongly affects the pseudospin polarization and can induce pseudospin precession. The scattering can also result in almost complete atomic transfer between the dark states.

  10. Supramolecular complex coupled to a metal nanoparticle: computational studies on the optical absorption.

    PubMed

    Zelinskyy, Yaroslav; Zhang, Yuan; May, Volkhard

    2012-11-26

    Absorption spectra of a supramolecular complex (SC) placed in the proximity of a spherical metal nanoparticle (MNP) are computed. A description of the absorption is used that is based on a density matrix propagation. The applied density matrix theory starts from a microscopic model including the Coulomb interaction between the SC and the MNP. This interaction is dominated by an energy exchange coupling between the excitations of the SC and the multipolar excitations of the MNP. Its nonperturbative consideration results in a shift and a broadening of all Frenkel-exciton levels as well as an oscillator strength change. If a J-aggregate type SC near a MNP is considered, all exciton levels strongly contribute to the absorption what is in contrast to the isolated SC.

  11. A self-consistent three-wave coupling model with complex linear frequencies

    SciTech Connect

    Kim, J.-H.; Terry, P. W.

    2011-09-15

    A three-wave coupling model with complex linear frequencies is investigated for the nonlinear interaction in a triad that has linearly unstable and stable modes. Time scales associated with linear and nonlinear physics are identified and compared with features of the frequency spectrum. From appropriate time scales, the frequency spectra are well characterized even in the transition to the steady state. The nonlinear time scales that best match spectral features are the nonlinear frequency of the fixed point and a frequency that depends on the amplitude displacement from the fixed point through the large-amplitude Jacobian elliptic solution. Two limited efforts to model the effect of other triads suggest robustness in the single triad results.

  12. Peculiarity in the electronic structure of Cu(II) complex ferromagnetically coupled with bisimino nitroxides.

    PubMed

    Ikoma, Tadaaki; Oshio, Hiroki; Yamamoto, Masashi; Ohba, Yasunori; Nihei, Masayuki

    2008-09-18

    By means of the electron spin resonance (ESR) technique, we have investigated the electronic structures of the tridentate imino nitroxyl diradical complex with copper(II) (Cu-bisimpy), which has a square planar structure and a ground quartet state with an extremely strong ferromagnetic exchange interaction, and its related compounds (bisimpy = 2,6-bis(1'-oxyl-4',4',5',5'-tetramethyl-4',5'-dihydro-1' H-imidazol-2'-yl)pyridine). It was clarified that Cu-bisimpy had unique magnetic orbitals, compared with the biradical ligand (bisimpy), a zinc(II) biradical complex (Zn-bisimpy) and a copper(II) terpyridine complex (Cu-tpy) (tpy = 2,2';6',2''-terpyridine). Multifrequency ESR spectroscopy provided a reliable set of magnetic parameters of Cu-bisimpy, which has a small g anisotropy ( g x = 2.02, g y = 2.01, g z = 2.08) and small hyperfine coupling with Cu (|A x| = 42.0 MHz, |A y|coupling in Cu-bisimpy. Multifrequency electron spin resonance spectroscopy clarified the unique electronic structure of a square planar copper(II) complex with an imino nitroxyl diradical, which undergoes a strong ferromagnetic interaction caused by a covalent bonding effect.

  13. Impact of asymptomatic infection on coupled disease-behavior dynamics in complex networks

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Feng; Xie, Jia-Rong; Chen, Han-Shuang; Liu, Can; Small, Michael

    2016-05-01

    Studies on how to model the interplay between diseases and behavioral responses (so-called coupled disease-behavior interaction) have attracted increasing attention. Owing to the lack of obvious clinical evidence of diseases, or the incomplete information related to the disease, the risks of infection cannot be perceived and may lead to inappropriate behavioral responses. Therefore, how to quantitatively analyze the impacts of asymptomatic infection on the interplay between diseases and behavioral responses is of particular importance. In this letter, under the complex network framework, we study the coupled disease-behavior interaction model by dividing infectious individuals into two states: U-state (without evident clinical symptoms, labelled as U) and I-state (with evident clinical symptoms, labelled as I). A susceptible individual can be infected by U- or I-nodes, however, since the U-nodes cannot be easily observed, susceptible individuals take behavioral responses only when they contact I-nodes. The mechanism is considered in the improved Susceptible-Infected-Susceptible (SIS) model and the improved Susceptible-Infected-Recovered (SIR) model, respectively. Then, one of the most concerned problems in spreading dynamics: the epidemic thresholds for the two models are given by two methods. The analytic results quantitatively describe the influence of different factors, such as asymptomatic infection, the awareness rate, the network structure, and so forth, on the epidemic thresholds. Moreover, because of the irreversible process of the SIR model, the suppression effect of the improved SIR model is weaker than the improved SIS model.

  14. A Tractable Method for Describing Complex Couplings between Neurons and Population Rate

    PubMed Central

    Marre, Olivier

    2016-01-01

    Abstract Neurons within a population are strongly correlated, but how to simply capture these correlations is still a matter of debate. Recent studies have shown that the activity of each cell is influenced by the population rate, defined as the summed activity of all neurons in the population. However, an explicit, tractable model for these interactions is still lacking. Here we build a probabilistic model of population activity that reproduces the firing rate of each cell, the distribution of the population rate, and the linear coupling between them. This model is tractable, meaning that its parameters can be learned in a few seconds on a standard computer even for large population recordings. We inferred our model for a population of 160 neurons in the salamander retina. In this population, single-cell firing rates depended in unexpected ways on the population rate. In particular, some cells had a preferred population rate at which they were most likely to fire. These complex dependencies could not be explained by a linear coupling between the cell and the population rate. We designed a more general, still tractable model that could fully account for these nonlinear dependencies. We thus provide a simple and computationally tractable way to learn models that reproduce the dependence of each neuron on the population rate. PMID:27570827

  15. Coupled ice shelf-ocean modeling and complex grounding line retreat from a seabed ridge

    NASA Astrophysics Data System (ADS)

    De Rydt, J.; Gudmundsson, G. H.

    2016-05-01

    Recent observations and modeling work have shown a complex mechanical coupling between Antarctica's floating ice shelves and the adjacent grounded ice sheet. A prime example is Pine Island Glacier, West Antarctica, which has a strong negative mass balance caused by a recent increase in ocean-induced melting of its ice shelf. The mass loss coincides with the retreat of the grounding line from a seabed ridge, on which it was at least partly grounded until the 1970s. At present, it is unclear what has caused the onset of this retreat and how feedback mechanisms between the ocean and ice shelf geometry have influenced the ice dynamics. To address these questions, we present the first results from an offline coupling between a state-of-the-art shallow-ice flow model with grounding line resolving capabilities and a three-dimensional ocean general circulation model with a static implementation of the ice shelf. A series of idealized experiments simulate the retreat from a seabed ridge in response to changes in the ocean forcing, and we show that the retreat becomes irreversible after 20 years of warm ocean conditions. A comparison to experiments with a simple depth-dependent melt rate parameterization demonstrates that such parameterizations are unable to capture the details of the retreat process, and they overestimate mass loss by more than 40% over a 50 year timescale.

  16. Coupled ice shelf-ocean modeling and complex grounding line retreat for Pine Island Glacier

    NASA Astrophysics Data System (ADS)

    De Rydt, Jan; Gudmundsson, Hilmar

    2016-04-01

    Recent observations and modeling work have shown a complex mechanical coupling between Antarctica's floating ice shelves and the adjacent grounded ice sheet. A prime example is Pine Island Glacier, West Antarctica, which has a strong negative mass balance caused by a recent increase in ocean-induced melting of its ice shelf. The mass loss coincides with the retreat of the grounding line from a seabed ridge, on which it was at least partly grounded until the 1970s. At present, it is unclear what has caused the onset of this retreat, and how feedback mechanisms between the ocean and iceshelf geometry have influenced the ice dynamics. To address these questions, we present results from an offline coupling between a state-of-the-art shallow-ice flow model with grounding line resolving capabilities, and a three-dimensional ocean general circulation model with a static implementation of the ice shelf. A series of idealized experiments simulate the retreat from a seabed ridge in response to changes in the ocean forcing, and we show that the retreat becomes irreversible after 20 years of warm ocean conditions. A comparison to experiments with a simple depth-dependent meltrate parameterisation demonstrates that such parameterizations are unable to capture the details of the retreat process, and they overestimate mass loss by more than 40% over a 50-year timescale.

  17. A Tractable Method for Describing Complex Couplings between Neurons and Population Rate.

    PubMed

    Gardella, Christophe; Marre, Olivier; Mora, Thierry

    2016-01-01

    Neurons within a population are strongly correlated, but how to simply capture these correlations is still a matter of debate. Recent studies have shown that the activity of each cell is influenced by the population rate, defined as the summed activity of all neurons in the population. However, an explicit, tractable model for these interactions is still lacking. Here we build a probabilistic model of population activity that reproduces the firing rate of each cell, the distribution of the population rate, and the linear coupling between them. This model is tractable, meaning that its parameters can be learned in a few seconds on a standard computer even for large population recordings. We inferred our model for a population of 160 neurons in the salamander retina. In this population, single-cell firing rates depended in unexpected ways on the population rate. In particular, some cells had a preferred population rate at which they were most likely to fire. These complex dependencies could not be explained by a linear coupling between the cell and the population rate. We designed a more general, still tractable model that could fully account for these nonlinear dependencies. We thus provide a simple and computationally tractable way to learn models that reproduce the dependence of each neuron on the population rate.

  18. Eddy current and coupled landscapes for nonadiabatic and nonequilibrium complex system dynamics

    PubMed Central

    Zhang, Kun; Sasai, Masaki; Wang, Jin

    2013-01-01

    Physical and biological systems are often involved with coupled processes of different time scales. In the system with electronic and atomic motions, for example, the interplay between the atomic motion along the same energy landscape and the electronic hopping between different landscapes is critical: the system behavior largely depends on whether the intralandscape motion is slower (adiabatic) or faster (nonadiabatic) than the interlandscape hopping. For general nonequilibrium dynamics where Hamiltonian or energy function is unknown a priori, the challenge is how to extend the concepts of the intra- and interlandscape dynamics. In this paper we establish a theoretical framework for describing global nonequilibrium and nonadiabatic complex system dynamics by transforming the coupled landscapes into a single landscape but with additional dimensions. On this single landscape, dynamics is driven by gradient of the potential landscape, which is closely related to the steady-state probability distribution of the enlarged dimensions, and the probability flux, which has a curl nature. Through an example of a self-regulating gene circuit, we show that the curl flux has dramatic effects on gene regulatory dynamics. The curl flux and landscape framework developed here are easy to visualize and can be used to guide further investigation of physical and biological nonequilibrium systems. PMID:23980160

  19. Coupling osmium complexes to epoxy-functionalised polymers to provide mediated enzyme electrodes for glucose oxidation.

    PubMed

    Ó Conghaile, Peter; Pöller, Sascha; MacAodha, Domhnall; Schuhmann, Wolfgang; Leech, Dónal

    2013-05-15

    Newly synthesised osmium complex-modified redox polymers were tested for potential application as mediators in glucose oxidising enzyme electrodes for application to biosensors or biofuel cells. Coupling of osmium complexes containing amine functional groups to epoxy-functionalised polymers of variable composition provides a range of redox polymers with variation possible in redox potential and physicochemical properties. Properties of the redox polymers as mediators for glucose oxidation were investigated by co-immobilisation onto graphite with glucose oxidase or FAD-dependent glucose dehydrogenase using a range of crosslinkers and in the presence and absence of multiwalled carbon nanotubes. Electrodes prepared by immobilising [P20-Os(2,2'-bipyridine)2(4-aminomethylpyridine)Cl].PF6, carbon nanotubes and glucose oxidase exhibit glucose oxidation current densities as high as 560μAcm(-2) for PBS containing 100mM glucose at 0.45V vs. Ag/AgCl. Films prepared by crosslinking [P20-Os(4,4'-dimethoxy-2,2'-bipyridine)2(4-aminomethylpyridine)Cl].PF6, an FAD-dependent glucose dehydrogenase, and carbon nanotubes achieve current densities of 215μAcm(-2) in 5mM glucose at 0.2V vs. Ag/AgCl, showing some promise for application to glucose oxidising biosensors or biofuel cells.

  20. Slug-flow microextraction coupled with paper spray mass spectrometry for rapid analysis of complex samples.

    PubMed

    Deng, Jiewei; Wang, Wenwen; Yang, Yunyun; Wang, Xiaowei; Chen, Baowei; Yao, Zhong-Ping; Luan, Tiangang

    2016-10-12

    Analysis of trace compounds in small-volume complex samples is of importance for forensic, clinical, pharmaceutical, environmental, and life science investigation. In this study, we reported the coupling of slug-flow microextraction with paper spray mass spectrometry for rapid analysis of trace analytes in small volume of complicated biological samples such as whole blood, milk, and body fluid, etc. The method is performed by applying a disposable glass capillary for rapid extraction of a small amount of complex samples using a small amount of organic solvent; the loaded organic solvent was then spotted onto a paper triangle and dried out; subsequently, a high voltage and some spray solvent were applied onto the paper triangle for mass spectrometric analysis. By using the proposed method, high sensitivity and satisfactory precision for quantitative analysis of trace macrolide antibiotics in whole bloods and milks as well as perfluorinated compounds in individual small organisms have been successfully achieved. In addition, investigation of bioaccumulation of perfluorinated compounds in individual small organisms has been reached. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Two-Dimensional Gas-Phase Separations Coupled to Mass Spectrometry for Analysis of Complex Mixtures

    PubMed Central

    Tang, Keqi; Li, Fumin; Shvartsburg, Alexandre A.; Strittmatter, Eric F.; Smith*, Richard D.

    2007-01-01

    Ion mobility spectrometry (IMS) has been explored for decades, and its versatility in separation and identification of gas-phase ions is well established. Recently, field asymmetric waveform IMS (FAIMS) has been gaining acceptance in similar applications. Coupled to mass spectrometry (MS), both IMS and FAIMS have shown the potential for broad utility in proteomics and other biological analyses. A major attraction of these separations is extremely high speed, exceeding that of condensed-phase alternatives by orders of magnitude. However, modest separation peak capacities have limited the utility of FAIMS and IMS for analyses of complex mixtures. We report 2-D gas-phase separations that join FAIMS to IMS, in conjunction with high-resolution and accuracy time-of-flight MS. Implementation of FAIMS/IMS and IMS/MS interfaces using electrodynamic ion funnels greatly improves sensitivity. Evaluation of FAIMS/IMS/TOF performance for a protein mixture tryptic digest reveals high orthogonality between FAIMS and IMS dimensions, and hence the benefit of FAIMS filtering prior to IMS/MS. The effective peak capacities in analyses of tryptic peptides are ~500 for FAIMS/IMS separations and ~106 for 3-D FAIMS/IMS/MS, providing a potential platform for ultrahigh-throughput analyses of complex mixtures. PMID:16194103

  2. Plexciton Dynamics: Exciton-Plasmon Coupling in a J-Aggregate-Au Nanoshell Complex Provides a Mechanism for Nonlinearity

    SciTech Connect

    Fofang, Nche T.; Grady, Nathaniel K.; Fan, Zhiyuan; Govorov, Alexander; Halas, Naomi J.

    2011-03-18

    Coherently coupled plasmons and excitons give rise to new optical excitations- plexcitons - due to the strong coupling of these two oscillator systems. Time-resolved studies of J-aggregate-Au nanoshell complexes when the nanoshell plasmon and J-aggregate exciton energies are degenerate probe the dynamical behavior of this coupled system. Transient absorption of the interacting plasmon-exciton system is observed, in dramatic contrast to the photoinduced transmission of the pristine J-aggregate. An additional, transient Fano-shaped modulation within the Fano dip is also observable. The behavior of the J-aggregate-Au nanoshell complex is described by a combined one-exciton and two-exciton state model coupled to the nanoshell plasmon.

  3. Plexciton dynamics: exciton-plasmon coupling in a J-aggregate-Au nanoshell complex provides a mechanism for nonlinearity.

    PubMed

    Fofang, Nche T; Grady, Nathaniel K; Fan, Zhiyuan; Govorov, Alexander O; Halas, Naomi J

    2011-04-13

    Coherently coupled plasmons and excitons give rise to new optical excitations--plexcitons--due to the strong coupling of these two oscillator systems. Time-resolved studies of J-aggregate-Au nanoshell complexes when the nanoshell plasmon and J-aggregate exciton energies are degenerate probe the dynamical behavior of this coupled system. Transient absorption of the interacting plasmon-exciton system is observed, in dramatic contrast to the photoinduced transmission of the pristine J-aggregate. An additional, transient Fano-shaped modulation within the Fano dip is also observable. The behavior of the J-aggregate-Au nanoshell complex is described by a combined one-exciton and two-exciton state model coupled to the nanoshell plasmon.

  4. Modular Approaches to Diversified Soft Lewis Basic Complexants through Suzuki-Miyaura Cross-Coupling of Bromoheteroarenes with Organotrifluoroborates.

    PubMed

    Chin, Ai Lin; Carrick, Jesse D

    2016-02-05

    Remediation or transmutation of spent nuclear fuel obtained as a function of energy production and legacy waste remains a significant environmental concern. Substantive efforts over the last three decades have focused on the potential of soft-Lewis basic complexants for the chemoselective separation of trivalent actinides from lanthanides in biphasic solvent systems. Recent efforts in this laboratory have focused on the concept of modularity to rapidly prepare complexants and complexant scaffolds not easily accessible via traditional linear methods in a convergent manner to better understand solubility and complexation structure/activity function in process-relevant solvents. The current work describes an efficient method for the construction of diversified complexants through multi-Suzuki-Miyaura cross-coupling of bromoheteroarenes with organotrifluoroborates affording efficient access to 22 novel materials in 43-99% yield over two, three, or four cross-couplings on the same scaffold. Optimization of the catalyst/ligand system, application, and limitations are reported herein.

  5. Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands.

    PubMed

    Börner, Martin; Blömer, Laura; Kischel, Marcus; Richter, Peter; Salvan, Georgeta; Zahn, Dietrich R T; Siles, Pablo F; Fuentes, Maria E N; Bufon, Carlos C B; Grimm, Daniel; Schmidt, Oliver G; Breite, Daniel; Abel, Bernd; Kersting, Berthold

    2017-01-01

    The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [Ni(II)2L(L')](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L' is a ω-mercapto-carboxylato ligand (L' = HS(CH2)5CO2(-) (6), HS(CH2)10CO2(-) (7), or HS(C6H4)2CO2(-) (8)), and their ability to adsorb on gold surfaces is reported. Besides elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESIMS), UV-vis spectroscopy, and X-ray crystallography (for 6 and 7), the compounds were also studied by temperature-dependent magnetic susceptibility measurements (for 7 and 8) and (broken symmetry) density functional theory (DFT) calculations. An S = 2 ground state is demonstrated by temperature-dependent susceptibility and magnetization measurements, achieved by ferromagnetic coupling between the spins of the Ni(II) ions in 7 (J = +22.3 cm(-1)) and 8 (J = +20.8 cm(-1); H = -2JS1S2). The reactivity of complexes 6-8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however, prevent the packing and self-assembly of the hydrocarbon chains. The smaller film thickness of 7 is attributed to the specific coordination mode of the coligand. Results of preliminary transport measurements utilizing rolled-up devices are also reported.

  6. Ab initio density matrix renormalization group study of magnetic coupling in dinuclear iron and chromium complexes

    SciTech Connect

    Harris, Travis V.; Morokuma, Keiji; Kurashige, Yuki; Yanai, Takeshi

    2014-02-07

    The applicability of ab initio multireference wavefunction-based methods to the study of magnetic complexes has been restricted by the quickly rising active-space requirements of oligonuclear systems and dinuclear complexes with S > 1 spin centers. Ab initio density matrix renormalization group (DMRG) methods built upon an efficient parameterization of the correlation network enable the use of much larger active spaces, and therefore may offer a way forward. Here, we apply DMRG-CASSCF to the dinuclear complexes [Fe{sub 2}OCl{sub 6}]{sup 2−} and [Cr{sub 2}O(NH{sub 3}){sub 10}]{sup 4+}. After developing the methodology through systematic basis set and DMRG M testing, we explore the effects of extended active spaces that are beyond the limit of conventional methods. We find that DMRG-CASSCF with active spaces including the metal d orbitals, occupied bridging-ligand orbitals, and their virtual double shells already capture a major portion of the dynamic correlation effects, accurately reproducing the experimental magnetic coupling constant (J) of [Fe{sub 2}OCl{sub 6}]{sup 2−} with (16e,26o), and considerably improving the smaller active space results for [Cr{sub 2}O(NH{sub 3}){sub 10}]{sup 4+} with (12e,32o). For comparison, we perform conventional MRCI+Q calculations and find the J values to be consistent with those from DMRG-CASSCF. In contrast to previous studies, the higher spin states of the two systems show similar deviations from the Heisenberg spectrum, regardless of the computational method.

  7. Theoretical study of head-on collision of dust acoustic solitary waves in a strongly coupled complex plasma

    SciTech Connect

    Jaiswal, S. Bandyopadhyay, P.; Sen, A.

    2014-05-15

    We investigate the propagation characteristics of two counter propagating dust acoustic solitary waves (DASWs) undergoing a head-on collision, in the presence of strong coupling between micron sized charged dust particles in a complex plasma. A coupled set of nonlinear dynamical equations describing the evolution of the two DASWs using the extended Poincaré-Lighthill-Kuo perturbation technique is derived. The nature and extent of post collision phase-shifts of these solitary waves are studied over a wide range of dusty plasma parameters in a strongly and a weakly coupled medium. We find a significant change in the nature and amount of phase delay in the strongly coupled regime as compared to a weakly coupled regime. The phase shift is seen to change its sign beyond a threshold value of compressibility of the medium for a given set of dusty plasma parameters.

  8. The complex G protein-coupled receptor kinase 2 (GRK2) interactome unveils new physiopathological targets

    PubMed Central

    Penela, Petronila; Murga, Cristina; Ribas, Catalina; Lafarga, Vanesa; Mayor, Federico

    2010-01-01

    GRK2 is a ubiquitous member of the G protein-coupled receptor kinase (GRK) family that appears to play a central, integrative role in signal transduction cascades. GRKs participate together with arrestins in the regulation of G protein-coupled receptors (GPCR), a family of hundreds of membrane proteins of key physiological and pharmacological importance, by triggering receptor desensitization from G proteins and GPCR internalization, and also by helping assemble macromolecular signalosomes in the receptor environment acting as agonist-regulated adaptor scaffolds, thus contributing to signal propagation. In addition, emerging evidence indicates that GRK2 can phosphorylate a growing number of non-GPCR substrates and associate with a variety of proteins related to signal transduction, thus suggesting that this kinase could also have diverse ‘effector’ functions. We discuss herein the increasing complexity of such GRK2 ‘interactome’, with emphasis on the recently reported roles of this kinase in cell migration and cell cycle progression and on the functional impact of the altered GRK2 levels observed in several relevant cardiovascular, inflammatory or tumour pathologies. Deciphering how the different networks of potential GRK2 functional interactions are orchestrated in a stimulus, cell type or context-specific way is critical to unveil the contribution of GRK2 to basic cellular processes, to understand how alterations in GRK2 levels or functionality may participate in the onset or development of several cardiovascular, tumour or inflammatory diseases, and to assess the feasibility of new therapeutic strategies based on the modulation of the activity, levels or specific interactions of GRK2. PMID:20590581

  9. Dynamic coupling of complex brain networks and dual-task behavior.

    PubMed

    Alavash, Mohsen; Thiel, Christiane M; Gießing, Carsten

    2016-04-01

    Multi-tasking is a familiar situation where behavioral performance is often challenged. To date, fMRI studies investigating the neural underpinning of dual-task interference have mostly relied on local brain activation maps or static brain connectivity networks. Here, based on task fMRI we explored how fluctuations in behavior during concurrent performance of a visuospatial and a speech task relate to alternations in the topology of dynamic brain connectivity networks. We combined a time-resolved functional connectivity and complex network analysis with a sliding window approach applied to the trial by trial behavioral responses to investigate the coupling between dynamic brain networks and dual-task behavior at close temporal proximity. Participants showed fluctuations in their dual-task behavior over time, with the accuracy in the component tasks being statistically independent from one another. On the global level of brain networks we found that dynamic changes of network topology were differentially coupled with the behavior in each component task during the course of dual-tasking. While momentary decrease in the global efficiency of dynamic brain networks correlated with subsequent increase in visuospatial accuracy, better speech performance was preceded by higher global network efficiency and was followed by an increase in between-module connectivity over time. Additionally, dynamic alternations in the modular organization of brain networks at the posterior cingulate cortex were differentially predictive for the visuospatial as compared to the speech accuracy over time. Our results provide the first evidence that, during the course of dual-tasking, each component task is supported by a distinct topological configuration of brain connectivity networks. This finding suggests that the failure of functional brain connectivity networks to adapt to an optimal topology supporting the performance in both component tasks at the same time contributes to the moment to

  10. Study of the influence of the bridge on the magnetic coupling in cobalt(II) complexes.

    PubMed

    Fabelo, Oscar; Cañadillas-Delgado, Laura; Pasán, Jorge; Delgado, Fernando S; Lloret, Francesc; Cano, Joan; Julve, Miguel; Ruiz-Pérez, Catalina

    2009-12-07

    Two new cobalt(II) complexes of formula [Co(2)(bta)(H(2)O)(6)](n) x 2nH(2)O (1) and [Co(phda)(H(2)O)](n) x nH(2)O (2) [H(4)bta = 1,2,4,5-benzenetetracarboxylic acid, H(2)phda = 1,4-phenylenediacetic acid] have been characterized by single crystal X-ray diffraction. Compound 1 is a one-dimensional compound where the bta(4-) ligand acts as 2-fold connector between the cobalt(II) ions through two carboxylate groups in para-conformation. Triply bridged dicobalt(II) units occur within each chain, a water molecule, a carboxylate group in the syn-syn conformation, and an oxo-carboxylate with the mu(2)O(1);kappa(2)O(1),O(2) coordination mode acting as bridges. Compound 2 is a three-dimensional compound, where the phda(2-) group acts as a bridge through its two carboxylate groups, one of them adopting the mu-O,O' coordination mode in the syn-syn conformation and the other exhibiting the single mu(2)-O'' bridging mode. As in 1, chains of cobalt(II) ions occur in 2 with a water molecule, a syn-syn carboxylate group, and an oxo-carboxylate constitute the triply intrachain bridging skeleton. Each chain is linked to other four ones through the phda(2-) ligand, giving rise to the three-dimensional structure. The values of the intrachain cobalt-cobalt separation are 3.1691(4) (1) and 3.11499(2) A (2) whereas those across the phenyl ring of the extended bta(4-) (1) and phda(2-) (2) groups are 10.1120(6) and 11.4805(69 A, respectively. The magnetic properties of 1 and 2 have been investigated in the temperature range 1.9-300 K, and their analysis has revealed the occurrence of moderate intrachain ferromagnetic couplings [J = +5.4 (1) and +2.16 cm(-1) (2), J being the isotropic magnetic coupling parameter], the magnetic coupling through the extended bta(4-) and phda(2-) with cobalt-cobalt separations larger than 10 A being negligible. The nature and magnitude of the magnetic interactions between the high-spin cobalt(II) ions in 1 and 2 are compared to those of related systems and

  11. Simplifying the complexity of a coupled carbon turnover and pesticide degradation model

    NASA Astrophysics Data System (ADS)

    Marschmann, Gianna; Erhardt, André H.; Pagel, Holger; Kügler, Philipp; Streck, Thilo

    2016-04-01

    The mechanistic one-dimensional model PECCAD (PEsticide degradation Coupled to CArbon turnover in the Detritusphere; Pagel et al. 2014, Biogeochemistry 117, 185-204) has been developed as a tool to elucidate regulation mechanisms of pesticide degradation in soil. A feature of this model is that it integrates functional traits of microorganisms, identifiable by molecular tools, and physicochemical processes such as transport and sorption that control substrate availability. Predicting the behavior of microbially active interfaces demands a fundamental understanding of factors controlling their dynamics. Concepts from dynamical systems theory allow us to study general properties of the model such as its qualitative behavior, intrinsic timescales and dynamic stability: Using a Latin hypercube method we sampled the parameter space for physically realistic steady states of the PECCAD ODE system and set up a numerical continuation and bifurcation problem with the open-source toolbox MatCont in order to obtain a complete classification of the dynamical system's behaviour. Bifurcation analysis reveals an equilibrium state of the system entirely controlled by fungal kinetic parameters. The equilibrium is generally unstable in response to small perturbations except for a small band in parameter space where the pesticide pool is stable. Time scale separation is a phenomenon that occurs in almost every complex open physical system. Motivated by the notion of "initial-stage" and "late-stage" decomposers and the concept of r-, K- or L-selected microbial life strategies, we test the applicability of geometric singular perturbation theory to identify fast and slow time scales of PECCAD. Revealing a generic fast-slow structure would greatly simplify the analysis of complex models of organic matter turnover by reducing the number of unknowns and parameters and providing a systematic mathematical framework for studying their properties.

  12. Accurate gradient approximation for complex interface problems in 3D by an improved coupling interface method

    SciTech Connect

    Shu, Yu-Chen; Chern, I-Liang; Chang, Chien C.

    2014-10-15

    Most elliptic interface solvers become complicated for complex interface problems at those “exceptional points” where there are not enough neighboring interior points for high order interpolation. Such complication increases especially in three dimensions. Usually, the solvers are thus reduced to low order accuracy. In this paper, we classify these exceptional points and propose two recipes to maintain order of accuracy there, aiming at improving the previous coupling interface method [26]. Yet the idea is also applicable to other interface solvers. The main idea is to have at least first order approximations for second order derivatives at those exceptional points. Recipe 1 is to use the finite difference approximation for the second order derivatives at a nearby interior grid point, whenever this is possible. Recipe 2 is to flip domain signatures and introduce a ghost state so that a second-order method can be applied. This ghost state is a smooth extension of the solution at the exceptional point from the other side of the interface. The original state is recovered by a post-processing using nearby states and jump conditions. The choice of recipes is determined by a classification scheme of the exceptional points. The method renders the solution and its gradient uniformly second-order accurate in the entire computed domain. Numerical examples are provided to illustrate the second order accuracy of the presently proposed method in approximating the gradients of the original states for some complex interfaces which we had tested previous in two and three dimensions, and a real molecule ( (1D63)) which is double-helix shape and composed of hundreds of atoms.

  13. Antibody fragments for stabilization and crystallization of G protein-coupled receptors and their signaling complexes.

    PubMed

    Shukla, Arun K; Gupta, Charu; Srivastava, Ashish; Jaiman, Deepika

    2015-01-01

    G protein-coupled receptors (GPCRs) are one of the key players in extracellular signal recognition and their subsequent communications with cellular signaling machinery. Crystallization and high-resolution structure determination of GPCRs has been one of the major advances in the area of GPCR biology over the last 7-8 years. There have primarily been three approaches to GPCR crystallization till date. These are fusion protein strategy, thermostabilization, and antibody fragment-mediated crystallization. Of these, antibody fragment-mediated crystallization has not only provided the first breakthrough in structure determination of a non-rhodopsin GPCR but it has also assisted in obtaining structures of fully active conformations of GPCRs. Antibody fragment approach has also been crucial in obtaining structural information on GPCR signaling complexes. Here, we highlight the specific examples of GPCR crystal structures that have utilized antibody fragments for promoting crystallogenesis and structure solution. We also discuss emerging powerful technologies such as the nanobody technology and the synthetic phage display libraries in the context of GPCR crystallization and underline how these tools are likely to propel key GPCR structural studies in future.

  14. Three-body resonances using slow variable discretization coupled with complex absorbing potential

    NASA Astrophysics Data System (ADS)

    Blandon, Juan; Kokoouline, Viatcheslav; Masnou-Seeuws, Francoise

    2006-05-01

    We are investigating three-body resonances for a model three-particle problem using the slow variable discretization method of Tolstikhin et al. [1] coupled with a complex absorbing potential. We compare the results with those of Fedorov et al. [2]. We will also present preliminary calculations on Efimov resonances using our method. Efimov states are a universal set of bound trimer states which appear when there is a two-body weakly-bound or virtual state [3]. Bound states of Efimov trimers have been studied in a number of theoretical treatments. Efimov resonances can be viewed as three-body Feshbach resonances that decay into a two-body bound system and a free third body (diatomic molecule + free atom, for example). Recent experimental evidence for Efimov trimers in an ultracold gas of Cs atoms obtained by Kraemer et al. [4] has made the study of their resonances especially relevant. [1] O. I. Tolstikhin et al., J. Phys. B: At. Mol. Opt. Phys. 29, L389 (1996). [2] D. V. Fedorov et al., Few Body Systems 33, 153 (2003). [3] B. D. Esry et al., Phys. Rev. A54, 394 (1996) and references therein. [4] T. Kraemer et al., arxiv.org/abs/cond-mat/0512394

  15. Pathogen control in complex fluids with water-coupled excimer lamps at 282 and 308 nm.

    PubMed

    Coogan, John J

    2005-01-01

    Water-coupled excimer lamp systems have been developed to inactivate microorganisms within complex, low-optical quality, fluids. Monochromatic lamps were selected to minimize UV-B and UV-C absorption within the carrier fluids while maximizing deposition within specific chemical targets. Fundamentals, system scaling and power supply design are discussed. This work used two large-surface area excimer lamps as intense sources of near monochromatic radiation at 308 and 282 nm. Data are presented for two distinct fluid systems: flow-through processing of large-volume metalworking fluids used in heavy industry and batch irradiation of human blood plasma and platelet suspensions used in transfusion medicine. In the first, a 200-600 L/min reactor is used to control bacterial concentrations within metalworking fluids used in large-scale metal machining processes. Control is defined as the maintenance of 10(3) to 10(4) CFU/mL in fluids that without treatment would have concentrations over 10(7) CFU/mL. The second is a batch process for viral inactivation in undiluted blood bank products. Samples of fresh frozen plasma and platelet suspensions were spiked with high titers of porcine parvovirus (PPV) and irradiated at 308 and 282 nm. Although both wavelengths were effective at reducing PPV levels, 308 nm light resulted in both higher rates of viral inactivation (greater than 6 log units) and lower rates of fluid degradation.

  16. The "K-pp" System Investigated with a Coupled-Channel Complex Scaling Method

    NASA Astrophysics Data System (ADS)

    Doté, Akinobu

    Nuclear systems with anti-kaons (kaonic nuclei) are expected to have exotic nature such as formation of a dense state, due to the strong attraction between an anti-kaon and a nucleon. In this article, the current theoretical studies of the most essential kaonic nucleus "K-pp" are reviewed and our study of "K-pp" based on a coupled-channel Complex Scaling Method is reported. With a new version of our chiral SU(3)-based potential constrained by a precise measurement of kaonic hydrogen atom (SIDDHARTA experiment), the "K-pp" state is found to be rather shallowly bound: BK - pp = 15-22 MeV and Γ M = 20-50 MeV. The "K-pp" seems to have another pole, and it might possibly have so-called a double-pole structure, similarly to the Λ (1405). Recent results of the K-pp search experiments (J-PARC E15 and E27) are discussed in comparison with several new theoretical studies.

  17. Complex image method for RF antenna-plasma inductive coupling calculation in planar geometry. Part I: basic concepts

    NASA Astrophysics Data System (ADS)

    Howling, A. A.; Guittienne, Ph; Jacquier, R.; Furno, I.

    2015-12-01

    The coupling between an inductive source and the plasma determines the power transfer efficiency and the reflected impedance in the primary circuit. Usually, the plasma coupling is analysed by means of a transformer equivalent circuit, where the plasma inductance and resistance are estimated using a global plasma model. This paper shows that, for planar RF antennas, the mutual inductance between the plasma and the primary circuit can be calculated using partial inductances and the complex image method, where the plasma coupling is determined in terms of the plasma skin depth and the distance to the plasma. To introduce the basic concepts, the mutual inductance is calculated here for a linear conductor parallel to the plasma surface. In the accompanying paper part II Guittienne et al (2015 Plasma Sources Sci. Technol. 24 065015), impedance measurements on a RF resonant planar plasma source are modeled using an impedance matrix where the plasma-antenna mutual impedances are calculated using the complex image method presented here.

  18. Cross coupling of magnesium diacetylenides with functional allylic and halide-containing compounds catalyzed by transition metal complexes

    SciTech Connect

    Dzhemilev, U.M.; Ibragimov, A.G.; Saraev, R.A.

    1986-08-20

    An efficient method has been developed for the synthesis of 1,4-enynes, conjugated acetylenes and aryl acetylenes by the cross coupling of magnesium diacetylenides with allyl ethers and esters, alkyl halides, allyl halides, aryl halides, allyl sulfides, and allylsulfones, using Ni and Pd complexes as the catalyst.

  19. Exchange coupling and anisotropy effects on the low temperature magnetization dynamics in rare-earth dioxolene complexes

    NASA Astrophysics Data System (ADS)

    Amjad, Asma; Poneti, Giordano; Sottini, Silvia; Dei, Andrea; Sorace, Lorenzo

    The prelude of relevant magnetic coupling in f-element based complexes is actively pursued to improve the single-molecule magnetic features. However, a quantitative analysis of magnetic properties of exchange-coupled anisotropic rare-earth based complexes is often hampered owing to the comparable magnitude of the crystal field with the magnetic coupling. In this study, we investigated the properties of complexes containing different ligands with comparable molecular structures and ligand field strengths. Comparative low-temperature magnetic and EPR study of homologous LnIIISemiquinonate (LnSQ) and LnIIITropolonate (LnTrp) complexes, where Ln = Dy, Tb is investigated. Single-crystal EPR revealed that the direct exchange coupling in DySQ resulted in a highly anisotropic pseudo-triplet state. An out-of-phase susceptibility signal was observed for TbTrp only in the presence of an external magnetic field. Furthermore, the dynamics revealed slow relaxation of magnetization in the DySQ at low temperature which upon comparative study with the dynamics of the related DyTrp revealed a not so simple dependence on the crystal field effects of the coordination sphere of the lanthanide.

  20. Synthesis of Naphthalenes through Three-Component Coupling of Alkynes, Fischer Carbene Complexes, and Benzaldehyde Hydrazones via Isoindole Intermediates

    PubMed Central

    Duan, Shaofeng; Sinha-Mahapatra, Dilip K.; Herndon, James W.

    2008-01-01

    The synthesis of naphthalene derivatives through three-component coupling of 2-alkynylbenzaldehyde hydrazones with carbene complexes and electron-deficient alkynes has been examined. The reaction involves formation of an isoindole derivative, followed by intramolecular Diels–Alder reaction, followed by nitrene extrusion. The reaction was highly regioselective using unsymmetrical alkynes. PMID:18351767

  1. Flight Behaviors of a Complex Projectile Using a Coupled Computational Fluid Dynamics (CFD)-based Simulation Technique: Free Motion

    DTIC Science & Technology

    2015-09-01

    extended for computation of free-flight aerodynamics and flight dynamics of a finned projectile with pulse jet control21 and is being extended for...Dynamics ( CFD )-based Simulation Technique: Free Motion by Jubaraj Sahu and Frank Fresconi Approved for public release...US Army Research Laboratory Flight Behaviors of a Complex Projectile Using a Coupled Computational Fluid Dynamics ( CFD )-based Simulation

  2. LGM ice sheets simulated with a complex fully coupled ice sheet - climate model

    NASA Astrophysics Data System (ADS)

    Ziemen, F.; Rodehacke, C.; Mikolajewicz, U.

    2012-04-01

    One major challenge in predicting future climate change is the validation of the numerical models. A particular good time period for testing ice sheet - climate interactions is the last glacial maximum (LGM). It combines large ice sheets with good proxy data cover. We use a coarse resolution complex climate model coupled with an ice sheet model to study the ice sheets and the climate of the last glacial maximum and validate our setup by comparing glacial as well as pre-industrial equilibrium experiments with reconstructions and the present state. Since the last glacial maximum climate is largely different from the pre-industrial climate, we can test our model under large perturbations that go beyond the linear range by running both setups. Our model comprises of the atmosphere-ocean-vegetation general circulation model ECHAM5/MPIOM/LPJ interactively coupled with the ice sheet model mPISM. mPISM is a modified version of the Parallel Ice Sheet Model from the University of Alaska, Fairbanks. We run ECHAM5 in T31 resolution (~ 3.75°), and mPISM on a 20 km grid covering most of the northern hemisphere. We do not use flux correction or anomaly maps in our models. For the surface mass balance, we use a positive degree day scheme with lapse rate correction and height desertification effect. We show results from steady state experiments under last glacial maximum as well as pre-industrial boundary conditions. In both cases, we are able to maintain reasonable ice sheet distributions. In the pre-industrial setup, the Greenland ice sheet looks realistic, and the only major deviation is an ice sheet forming in the Rocky Mountains due to a cold bias in ECHAM5 in this region. The last glacial maximum ice sheets largely agree with the reconstructions except for an ice sheet that forms in eastern Siberia and extends to the Alaskan end of the Laurentide ice sheet. The ice sheets never reach a perfectly steady state because parts show repeated surges resembling Heinrich events. Most

  3. Residence Times of Molecular Complexes in Solution from NMR Data of Intermolecular Hydrogen-Bond Scalar Coupling.

    PubMed

    Zandarashvili, Levani; Esadze, Alexandre; Kemme, Catherine A; Chattopadhyay, Abhijnan; Nguyen, Dan; Iwahara, Junji

    2016-03-03

    The residence times of molecular complexes in solution are important for understanding biomolecular functions and drug actions. We show that NMR data of intermolecular hydrogen-bond scalar couplings can yield information on the residence times of molecular complexes in solution. The molecular exchange of binding partners via the breakage and reformation of a complex causes self-decoupling of intermolecular hydrogen-bond scalar couplings, and this self-decoupling effect depends on the residence time of the complex. For protein-DNA complexes, we investigated the salt concentration dependence of intermolecular hydrogen-bond scalar couplings between the protein side-chain (15)N and DNA phosphate (31)P nuclei, from which the residence times were analyzed. The results were consistent with those obtained by (15)Nz-exchange spectroscopy. This self-decoupling-based kinetic analysis is unique in that it does not require any different signatures for the states involved in the exchange, whereas such conditions are crucial for kinetic analyses by typical NMR and other methods.

  4. Proton-Coupled Electron Transfer in a Strongly Coupled Photosystem II-Inspired Chromophore–Imidazole–Phenol Complex: Stepwise Oxidation and Concerted Reduction

    SciTech Connect

    Manbeck, Gerald F.; Fujita, Etsuko; Concepcion, Javier J.

    2016-08-18

    Proton-coupled electron-transfer (PCET) reactions were studied in acetonitrile for a Photosystem II (PSII) inspired [Ru(bpy)2(phen-imidazole-Ph(OH)(tBu)2)]2+, in which Ru(III) generated by a flash-quench sequence oxidizes the appended phenol and the proton is transferred to the hydrogen bonded imidazole base. In contrast to related systems, the donor and acceptor are strongly coupled, as indicated by the shift in the RuIII/IIcouple upon phenol oxidation, and intramolecular oxidation of the phenol by Ru(III) is energetically favorable by both stepwise or concerted pathways. The phenol oxidation occurs via a stepwise ET-PT mechanism with kET = 2.7 × 107 s₋1 and a kinetic isotope effect (KIE) of 0.99 ± 0.03. The electron transfer reaction was characterized as adiabatic with λDA = 1.16 eV and 280 < HDA < 540 cm₋1 consistent with strong electronic coupling and slow solvent dynamics. Reduction of the phenoxyl radical by the quencher radical was examined as the analogue of the redox reaction between the PSII tyrosyl radical and the oxygen evolving complex (OEC). In our PSII-inspired complex, the recombination reaction activation energy is < 2 kcal mol₋1. In conclusion, the reaction is nonadiabatic (VPCET ~ 22 cm₋1 (H) and 49 cm₋1 (D)), concerted, and exhibits an unexpected inverse KIE of 0.55 that is attributed to greater overlap of the reactant vibronic ground state with the OD vibronic states of the proton acceptor due to the smaller quantum spacing of the deuterium vibrational levels.

  5. Proton-Coupled Electron Transfer in a Strongly Coupled Photosystem II-Inspired Chromophore–Imidazole–Phenol Complex: Stepwise Oxidation and Concerted Reduction

    SciTech Connect

    Manbeck, Gerald F.; Fujita, Etsuko; Concepcion, Javier J.

    2016-08-18

    Proton-coupled electron-transfer (PCET) reactions were studied in acetonitrile for a Photosystem II (PSII) inspired [Ru(bpy)2(phen-imidazole-Ph(OH)(tBu)2)]2+, in which Ru(III) generated by a flash-quench sequence oxidizes the appended phenol and the proton is transferred to the hydrogen bonded imidazole base. In contrast to related systems, the donor and acceptor are strongly coupled, as indicated by the shift in the RuIII/IIcouple upon phenol oxidation, and intramolecular oxidation of the phenol by Ru(III) is energetically favorable by both stepwise or concerted pathways. The phenol oxidation occurs via a stepwise ET-PT mechanism with kET = 2.7 × 107 s₋1 and a kinetic isotope effect (KIE) of 0.99 ± 0.03. The electron transfer reaction was characterized as adiabatic with λDA = 1.16 eV and 280 < HDA < 540 cm₋1 consistent with strong electronic coupling and slow solvent dynamics. Reduction of the phenoxyl radical by the quencher radical was examined as the analogue of the redox reaction between the PSII tyrosyl radical and the oxygen evolving complex (OEC). In our PSII-inspired complex, the recombination reaction activation energy is < 2 kcal mol₋1. In conclusion, the reaction is nonadiabatic (VPCET ~ 22 cm₋1 (H) and 49 cm₋1 (D)), concerted, and exhibits an unexpected inverse KIE of 0.55 that is attributed to greater overlap of the reactant vibronic ground state with the OD vibronic states of the proton acceptor due to the smaller quantum spacing of the deuterium vibrational levels.

  6. Routes to complex dynamics in a ring of unidirectionally coupled systems.

    PubMed

    Perlikowski, P; Yanchuk, S; Wolfrum, M; Stefanski, A; Mosiolek, P; Kapitaniak, T

    2010-03-01

    We study the dynamics of a ring of unidirectionally coupled autonomous Duffing oscillators. Starting from a situation where the individual oscillator without coupling has only trivial equilibrium dynamics, the coupling induces complicated transitions to periodic, quasiperiodic, chaotic, and hyperchaotic behavior. We study these transitions in detail for small and large numbers of oscillators. Particular attention is paid to the role of unstable periodic solutions for the appearance of chaotic rotating waves, spatiotemporal structures, and the Eckhaus effect for a large number of oscillators. Our analytical and numerical results are confirmed by a simple experiment based on the electronic implementation of coupled Duffing oscillators.

  7. Complex eigensolutions of coupled flexural and longitudinal modes in a beam with inclined elastic supports with non-proportional damping

    NASA Astrophysics Data System (ADS)

    Noll, Scott; Dreyer, Jason; Singh, Rajendra

    2014-02-01

    Structure borne vibration and noise in an automobile are often explained by representing the full vehicle as a system of elastically coupled beam structures representing the body, engine cradle and body subframe where the engine is often connected to the chassis via inclined viscoelastic supports. To understand more clearly the interactions between a beam structure and isolators, this article examines the flexural and longitudinal motions in an elastic beam with intentionally inclined mounts (viscoelastic end supports). A new analytical solution is derived for the boundary coupled Euler beam and wave equations resulting in complex eigensolutions. This system is demonstrated to be self-adjoint when the support stiffness matrices are symmetric; thus, the modal analysis is used to decouple the equations of motion and solve for the steady state, damped harmonic response. Experimental validation and computational verifications confirm the validity of the proposed formulation. New and interesting phenomena are presented including coupled rigid motions, modal properties for ideal angled roller boundaries, and relationships between coupling and system modal loss factors. The ideal roller boundary conditions when inclined are seen as a limiting case of coupled longitudinal and flexural motions. In particular, the coupled rigid body motions illustrate the influence of support stiffness coupling on the eigenvalues and eigenfunctions. The relative modal strain energy concept is used to distinguish the contribution of longitudinal and flexural deformation modes. Since the beam is assumed to be undamped, the system damping is derived from the viscoelastic supports. The support damping (for a given loss factor) is shown to be redistributed between the system modes due to the inclined coupling mechanisms. Finally, this article provides valuable insight by highlighting some technical issues a real-life designer faces when balancing modeling assumptions such as rigid or elastic

  8. A peroxynitrite complex of copper: formation from a copper-nitrosyl complex, transformation to nitrite and exogenous phenol oxidative coupling or nitration.

    PubMed

    Park, Ga Young; Deepalatha, Subramanian; Puiu, Simona C; Lee, Dong-Heon; Mondal, Biplab; Narducci Sarjeant, Amy A; del Rio, Diego; Pau, Monita Y M; Solomon, Edward I; Karlin, Kenneth D

    2009-11-01

    Reaction of nitrogen monoxide with a copper(I) complex possessing a tridentate alkylamine ligand gives a Cu(I)-(*NO) adduct, which when exposed to dioxygen generates a peroxynitrite (O=NOO(-))-Cu(II) species. This undergoes thermal transformation to produce a copper(II) nitrito (NO(2) (-)) complex and 0.5 mol equiv O(2). In the presence of a substituted phenol, the peroxynitrite complex effects oxidative coupling, whereas addition of chloride ion to dissociate the peroxynitrite moiety instead leads to phenol ortho nitration. Discussions include the structures (including electronic description) of the copper-nitrosyl and copper-peroxynitrite complexes and the formation of the latter, based on density functional theory calculations and accompanying spectroscopic data.

  9. Re-affirmation of a Preliminary Live with Love Conceptual Framework for cancer couple dyads: A couple-based complex intervention study.

    PubMed

    Li, Qiuping; Xu, Yinghua; Zhou, Huiya; Loke, Alice Yuen

    2016-02-01

    The relational dynamics of couples may be under great strain due to the diagnosis and treatment of cancer. A complex "Caring for Couples Coping with Cancer" (4Cs) intervention program, guided by a Preliminary Live with Love Conceptual Framework (P-LLCF) for Cancer Couple Dyads, was developed to support couples going through such hardship. The purpose of this paper is to present a re-analysis of the results of the 4Cs intervention program to determine whether the findings provide evidence to support the constructs in the P-LLCF. The 4Cs intervention was provided to support cancer patients and their spousal caregivers. The pre- and post-intervention findings of the 4Cs intervention program were re-analyzed using descriptive-correlational analysis and structural equation modeling (SEM) to test whether the findings provide evidence to support the constructs in the P-LLCF. A total of 92 out of the 117 dyads at baseline (T0) were successfully followed-up at 6 weeks (T1). The re-analysis of the findings from the 4Cs program (T1 outcomes) showed inter-relationships among the components included in the P-LLCF: dyadic mediators, dyadic coping, dyadic appraisal, and dyadic outcomes. The SEM of all six models resulted in convergence and showed goodness of fit to the data and variables, which is supportive of the constructs in the P-LLCF. The present analysis of the T1 outcome measures of the 4Cs program provides evidence to support the constructs in the P-LLCF. Multiple mutual effects existed between couples in the process of living and coping with cancer as dyads. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. A novel 4-aminoantipyrine-Pd(II) complex catalyzes Suzuki-Miyaura cross-coupling reactions of aryl halides.

    PubMed

    Contreras-Celedón, Claudia Araceli; Mendoza-Rayo, Darío; Rincón-Medina, José A; Chacón-García, Luis

    2014-01-01

    A simple and efficient catalytic system based on a Pd complex of 4-aminoantipyrine, 4-AAP-Pd(II), was found to be highly active for Suzuki-Miyaura cross-coupling of aryl iodides and bromides with phenylboronic acids under mild reaction conditions. Good to excellent product yields from the cross-coupling reaction can be achieved when the reaction is carried out in ethanol, in the open air, using low loading of 4-AAP-Pd(II) as a precatalyst, and in the presence of aqueous K2CO3 as the base. A variety of functional groups are tolerated.

  11. Relaxation and anharmonic couplings of the O-H stretching vibration of asymmetric strongly hydrogen-bonded complexes.

    PubMed

    Gündoğdu, Kenan; Bandaria, Jigar; Nydegger, Michael; Rock, William; Cheatum, Christopher M

    2007-07-28

    We present infrared transient grating measurements of complexes of formic acid with pyridine and pyrazine at four excitation frequencies within the broad proton-stretching band. These experiments investigate the mechanism of the line broadening of the O-H stretching vibration. The transients show coherent oscillations that decay within a few hundred femtoseconds and population relaxation on two time scales. We fit the data using a simple model of three coupled oscillators that relax via sequential kinetics through an intermediate state. Based on this model, we conclude that the coherent oscillations result from superpositions of Fermi-resonance-coupled states involving formic acid overtone and combination states.

  12. A novel 4-aminoantipyrine-Pd(II) complex catalyzes Suzuki–Miyaura cross-coupling reactions of aryl halides

    PubMed Central

    Mendoza-Rayo, Darío; Rincón-Medina, José A; Chacón-García, Luis

    2014-01-01

    Summary A simple and efficient catalytic system based on a Pd complex of 4-aminoantipyrine, 4-AAP–Pd(II), was found to be highly active for Suzuki–Miyaura cross-coupling of aryl iodides and bromides with phenylboronic acids under mild reaction conditions. Good to excellent product yields from the cross-coupling reaction can be achieved when the reaction is carried out in ethanol, in the open air, using low loading of 4-AAP–Pd(II) as a precatalyst, and in the presence of aqueous K2CO3 as the base. A variety of functional groups are tolerated. PMID:25550748

  13. Relaxation and anharmonic couplings of the O-H stretching vibration of asymmetric strongly hydrogen-bonded complexes

    NASA Astrophysics Data System (ADS)

    Gündoǧdu, Kenan; Bandaria, Jigar; Nydegger, Michael; Rock, William; Cheatum, Christopher M.

    2007-07-01

    We present infrared transient grating measurements of complexes of formic acid with pyridine and pyrazine at four excitation frequencies within the broad proton-stretching band. These experiments investigate the mechanism of the line broadening of the O-H stretching vibration. The transients show coherent oscillations that decay within a few hundred femtoseconds and population relaxation on two time scales. We fit the data using a simple model of three coupled oscillators that relax via sequential kinetics through an intermediate state. Based on this model, we conclude that the coherent oscillations result from superpositions of Fermi-resonance-coupled states involving formic acid overtone and combination states.

  14. Organotrifluoroborates and Monocoordinated Palladium Complexes as Catalysts—A Perfect Combination for Suzuki–Miyaura Coupling

    PubMed Central

    Molander, Gary A.; Canturk, Belgin

    2010-01-01

    Monocoordinated palladium catalysts derived from sterically hindered, electron-rich phosphines or N-heterocyclic carbenes have revolutionized the Suzuki–Miyaura coupling reaction. The emergence of organotrifluoroborates has provided important new perspectives for the organoboron component of these reactions. In combination, these two components prove to be extraordinarily powerful partners for cross-coupling reactions. PMID:19899086

  15. Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

    PubMed Central

    Apps, Michael G.; Johnson, Ben W.; Sutcliffe, Oliver B.; Brown, Sarah D.; Wheate, Nial J.

    2014-01-01

    Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand. PMID:24893964

  16. Embedding complex hydrology in the regional climate system - Dynamic coupling across different modelling domains

    NASA Astrophysics Data System (ADS)

    Butts, Michael; Drews, Martin; Larsen, Morten A. D.; Lerer, Sara; Rasmussen, Søren H.; Grooss, Jesper; Overgaard, Jesper; Refsgaard, Jens C.; Christensen, Ole B.; Christensen, Jens H.

    2014-12-01

    To improve our understanding of the impacts of feedback between the atmosphere and the terrestrial water cycle including groundwater and to improve the integration of water resource management modelling for climate adaption we have developed a dynamically coupled climate-hydrological modelling system. The OpenMI modelling interface is used to couple a comprehensive hydrological modelling system, MIKE SHE running on personal computers, and a regional climate modelling system, HIRHAM running on a high performance computing platform. The coupled model enables two-way interaction between the atmosphere and the groundwater via the land surface and can represent the lateral movement of water in both the surface and subsurface and their interactions, not normally accounted for in climate models. Meso-scale processes are important for climate in general and rainfall in particular. Hydrological impacts are assessed at the catchment scale, the most important scale for water management. Feedback between groundwater, the land surface and the atmosphere occurs across a range of scales. Recognising this, the coupling was developed to allow dynamic exchange of water and energy at the catchment scale embedded within a larger meso-scale modelling domain. We present the coupling methodology used and describe the challenges in representing the exchanges between models and across scales. The coupled model is applied to one-way and two-way coupled simulations for a managed groundwater-dominated catchment, the Skjern River, Denmark. These coupled model simulations are evaluated against field observations and then compared with uncoupled climate and hydrological model simulations. Exploratory simulations show significant differences, particularly in the summer for precipitation and evapotranspiration the coupled model including groundwater and the RCM where groundwater is neglected. However, the resulting differences in the net precipitation and the catchment runoff in this groundwater

  17. The complex contribution of sociodemographics to decision-making power in gay male couples.

    PubMed

    Perry, Nicholas S; Huebner, David M; Baucom, Brian R W; Hoff, Colleen C

    2016-12-01

    Relationship power is an important dyadic construct in close relationships that is associated with relationship health and partner's individual health. Understanding what predicts power in heterosexual couples has proven difficult, and even less is known about gay couples. Resource models of power posit that demographic characteristics associated with social status (e.g., age, income) confer power within the relationship, which in turn shapes relationship outcomes. We tested this model in a sample of gay male couples (N = 566 couples) and extended it by examining race and HIV status. Multilevel modeling was used to test associations between demographic bases of power and decision-making power. We also examined relative associations among demographic bases and decision-making power with relationship satisfaction given the literature on power imbalances and overall relationship functioning. Results showed that individual income was positively associated with decision-making power, as was participant's HIV status, with HIV-positive men reporting greater power. Age differences within the relationship interacted with relationship length to predict decision-making power, but not satisfaction. HIV-concordant positive couples were less satisfied than concordant negative couples. Higher power partners were less satisfied than lower power partners. Demographic factors contributing to decision-making power among same-sex male couples appear to share some similarities with heterosexual couples (e.g., income is associated with power) and have unique features (e.g., HIV status influences power). However, these same demographics did not reliably predict relationship satisfaction in the manner that existing power theories suggest. Findings indicate important considerations for theories of power among same-sex male couples. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  18. Broken symmetry approach to density functional calculation of magnetic anisotropy or zero field splittings for multinuclear complexes with antiferromagnetic coupling.

    PubMed

    van Wüllen, Christoph

    2009-10-29

    Antiferromagnetic coupling in multinuclear transition metal complexes usually leads to electronic ground states that cannot be described by a single Slater determinant and that are therefore difficult to describe by Kohn-Sham density functional methods. Density functional calculations in such cases are usually converged to broken symmetry solutions which break spin and, in many cases, also spatial symmetry. While a procedure exists to extract isotropic Heisenberg (exchange) coupling constants from such calculations, no such approach is yet established for the calculation of magnetic anisotropy energies or zero field splitting parameters. This work proposes such a procedure. The broken symmetry solutions are not only used to extract the exchange couplings but also single-ion D tensors which are then used to construct a (phenomenological) spin Hamiltonian, from which the magnetic anisotropy and the zero-field energy levels can be computed. The procedure is demonstrated for a bi- and a trinuclear Mn(III) model compound.

  19. Proton-Coupled Electron Transfer in a Strongly Coupled Photosystem II-Inspired Chromophore–Imidazole–Phenol Complex: Stepwise Oxidation and Concerted Reduction

    DOE PAGES

    Manbeck, Gerald F.; Fujita, Etsuko; Concepcion, Javier J.

    2016-08-18

    Proton-coupled electron-transfer (PCET) reactions were studied in acetonitrile for a Photosystem II (PSII) inspired [Ru(bpy)2(phen-imidazole-Ph(OH)(tBu)2)]2+, in which Ru(III) generated by a flash-quench sequence oxidizes the appended phenol and the proton is transferred to the hydrogen bonded imidazole base. In contrast to related systems, the donor and acceptor are strongly coupled, as indicated by the shift in the RuIII/IIcouple upon phenol oxidation, and intramolecular oxidation of the phenol by Ru(III) is energetically favorable by both stepwise or concerted pathways. The phenol oxidation occurs via a stepwise ET-PT mechanism with kET = 2.7 × 107 s₋1 and a kinetic isotope effect (KIE)more » of 0.99 ± 0.03. The electron transfer reaction was characterized as adiabatic with λDA = 1.16 eV and 280 < HDA < 540 cm₋1 consistent with strong electronic coupling and slow solvent dynamics. Reduction of the phenoxyl radical by the quencher radical was examined as the analogue of the redox reaction between the PSII tyrosyl radical and the oxygen evolving complex (OEC). In our PSII-inspired complex, the recombination reaction activation energy is < 2 kcal mol₋1. In conclusion, the reaction is nonadiabatic (VPCET ~ 22 cm₋1 (H) and 49 cm₋1 (D)), concerted, and exhibits an unexpected inverse KIE of 0.55 that is attributed to greater overlap of the reactant vibronic ground state with the OD vibronic states of the proton acceptor due to the smaller quantum spacing of the deuterium vibrational levels.« less

  20. Synchronization-based topology identification of weighted general complex dynamical networks with time-varying coupling delay

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoqun

    2008-02-01

    Many existing papers investigated the geometric features, control and synchronization of complex dynamical networks provided with certain topology. However, the exact topology of a network is sometimes unknown or uncertain. Based on LaSalle’s invariance principle, we propose an adaptive feedback technique to identify the exact topology of a weighted general complex dynamical network model with time-varying coupling delay. By receiving the network nodes evolution, the topology of such a kind of network with identical or different nodes, or even with varying topology can be monitored. In comparison with previous methods, time delay is taken into account in this simple, analytical and systematic synchronization-based technique. Particularly, the weight configuration matrix is not necessarily symmetric or irreducible, and the inner-coupling matrix need not be symmetric. Illustrative simulations are provided to verify the correctness and effectiveness of the proposed scheme.

  1. Organometallic nickel(III) complexes relevant to cross-coupling and carbon-heteroatom bond formation reactions.

    PubMed

    Zheng, Bo; Tang, Fengzhi; Luo, Jia; Schultz, Jason W; Rath, Nigam P; Mirica, Liviu M

    2014-04-30

    Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing aryl and alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C-heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(III) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.

  2. Self-time-delay synchronization of time-delay coupled complex chaotic system and its applications to communication

    NASA Astrophysics Data System (ADS)

    Zhang, Fangfang; Liu, Shutang

    2014-10-01

    Considering the time lag produced by the transmission in chaos-communication, we present self-time-delay synchronization (STDS) of complex chaotic systems. STDS implies that the synchronization between the time-delay system (the receiver) and the original system (the transmitter) while maintaining the structure and parameters of systems unchanged, thus these various problems produced by time-delay in practice are avoided. It is more suitable to simulate real communication situation. Aimed to time-delay coupled complex chaotic systems, the control law is derived by active control technique. Based on STDS, a novel communication scheme is further designed according to chaotic masking. In simulation, we take time-delay coupled complex Lorenz system transmitting actual speech signal (analog signal) and binary signal as examples. The speech signal contains two components, which are transmitted by the real part and imaginary part of one complex state variable. Two sequences of binary bits are converted into analog signals by 2M-ary and zero-order holder, then added into the real part and imaginary part of one complex state variable. Therefore, the STDS controller is realized by one critical state variable. It is simple in principle and easy to implement in engineering. Moreover, the communication system is robust to noise. It is possible to adopt cheap circuits with time-delay, which is economical and practical for communication.

  3. Endoglucanase Peripheral Loops Facilitate Complexation of Glucan Chains on Cellulose via Adaptive Coupling to the Emergent Substrate Structures

    SciTech Connect

    Lin, Yuchun; Beckham, Gregg T.; Himmel, Michael E.; Crowley, Michael F.; Chu, Jhih-wei

    2013-09-19

    We examine how the catalytic domain of a glycoside hydrolase family 7 endoglucanase catalytic domain (Cel7B CD) facilitates complexation of cellulose chains from a crystal surface. With direct relevance to the science of biofuel production, this problem also represents a model system of biopolymer processing by proteins in Nature. Interactions of Cel7B CD with a cellulose microfibril along different paths of complexation are characterized by mapping the atomistic fluctuations recorded in free-energy simulations onto the parameters of a coarse-grain model. The resulting patterns of protein-biopolymer couplings also uncover the sequence signatures of the enzyme in peeling off glucan chains from the microfibril substrate. We show that the semiopen active site of Cel7B CD exhibits similar barriers and free energies of complexation over two distinct routes; namely, scooping of a chain into the active-site cleft and threading from the chain end into the channel. On the other hand, the complexation energetics strongly depends on the surface packing of the targeted chain and the resulting interaction sites with the enzyme. A revealed principle is that Cel7B CD facilitates cellulose deconstruction via adaptive coupling to the emergent substrate. The flexible, peripheral segments of the protein outside of the active-site cleft are able to accommodate the varying features of cellulose along the simulated paths of complexation. The general strategy of linking physics-based molecular interactions to protein sequence could also be helpful in elucidating how other protein machines process biopolymers.

  4. Complexation studies with lanthanides and humic acid analyzed by ultrafiltration and capillary electrophoresis-inductively coupled plasma mass spectrometry.

    PubMed

    Kautenburger, Ralf; Beck, Horst Philipp

    2007-08-03

    For the long-term storage of radioactive waste, detailed information about geo-chemical behavior of radioactive and toxic metal ions under environmental conditions is necessary. Humic acid (HA) can play an important role in the immobilisation or mobilisation of metal ions due to complexation and colloid formation. Therefore, we investigate the complexation behavior of HA and its influence on the migration or retardation of selected lanthanides (europium and gadolinium as homologues of the actinides americium and curium). Two independent speciation techniques, ultrafiltration and capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) have been compared for the study of Eu and Gd interaction with (purified Aldrich) HA. The degree of complexation of Eu and Gd in 25 mg l(-1) Aldrich HA solutions was determined with a broad range of metal loading (Eu and Gd total concentration between 10(-6) and 10(-4) mol l(-1)), ionic strength of 10 mM (NaClO4) and different pH-values. From the CE-ICP-MS electropherograms, additional information on the charge of the Eu species was obtained by the use of 1-bromopropane as neutral marker. To detect HA in the ICP-MS and separate between HA complexed and non complexed metal ions in the CE-ICP-MS, we have halogenated the HA with iodine as ICP-MS marker.

  5. Effective DNA binding and cleaving tendencies of malonic acid coupled transition metal complexes

    NASA Astrophysics Data System (ADS)

    Pravin, Narayanaperumal; Utthra, Ponnukalai Ponya; Kumaravel, Ganesan; Raman, Natarajan

    2016-11-01

    Eight transition metal complexes were designed to achieve maximum biological efficacy. They were characterized by elemental analysis and various other spectroscopic techniques. The monomeric complexes were found to espouse octahedral geometry and non-electrolytic nature. The DNA interaction propensity of the complexes with calf thymus DNA (CT-DNA), studied at physiological pH by spectrophotometric, spectrofluorometric, cyclic voltammetry, and viscometric techniques revealed intercalation as the possible binding mode. Fascinatingly, the complexes were found to exhibit greater binding strength than that of the free ligands. A strong hypochromism and a slight red shift were exhibited by complex 5 among the other complexes. The intrinsic binding constant values of all the complexes compared to cisplatin reveal that they are excellent metallonucleases than that of cisplatin. The complexes were also shown to reveal displacement of the ethidium bromide, a strong intercalator using fluorescence titrations. Gel electrophoresis was used to divulge the competence of the complexes in cleaving the supercoiled pBR322 plasmid DNA. From the results, it is concluded that the complexes, especially 5, are excellent chemical nucleases in the presence of H2O2. Furthermore, the in vitro antimicrobial screening of the complexes exposes that these complexes are excellent antimicrobial agents. Overall the effect of coligands is evident from the results of all the investigations.

  6. Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment

    ERIC Educational Resources Information Center

    Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

    2011-01-01

    A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

  7. Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment

    ERIC Educational Resources Information Center

    Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

    2011-01-01

    A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

  8. Structure of Human G Protein-Coupled Receptor Kinase 2 in Complex with the Kinase Inhibitor Balanol

    SciTech Connect

    Tesmer, John J.G.; Tesmer, Valerie M.; Lodowski, David T.; Steinhagen, Henning; Huber, Jochen

    2010-07-19

    G protein-coupled receptor kinase 2 (GRK2) is a pharmaceutical target for the treatment of cardiovascular diseases such as congestive heart failure, myocardial infarction, and hypertension. To better understand how nanomolar inhibition and selectivity for GRK2 might be achieved, we have determined crystal structures of human GRK2 in complex with G{beta}{gamma} in the presence and absence of the AGC kinase inhibitor balanol. The selectivity of balanol among human GRKs is assessed.

  9. Fluorescence enhancement of light-harvesting complex 2 from purple bacteria coupled to spherical gold nanoparticles

    SciTech Connect

    Bujak, Ł.; Czechowski, N.; Piatkowski, D.; Litvin, R.; Mackowski, S.; Brotosudarmo, T. H. P.; Pichler, S.; Cogdell, R. J.; Heiss, W.

    2011-10-24

    The influence of plasmon excitations in spherical gold nanoparticles on the optical properties of a light-harvesting complex 2 (LH2) from the purple bacteria Rhodopseudomonas palustris has been studied. Systematic analysis is facilitated by controlling the thickness of a silica layer between Au nanoparticles and LH2 complexes. Fluorescence of LH2 complexes features substantial increase when these complexes are separated by 12 nm from the gold nanoparticles. At shorter distances, non-radiative quenching leads to a decrease of fluorescence emission. The enhancement of fluorescence originates predominantly from an increase of absorption of pigments comprising the LH2 complex.

  10. Reaction-complexation coupling between an enzyme and its polyelectrolytic substrate: determination of the dissociation constant of the hyaluronidase-hyaluronan complex from the hyaluronidase substrate-dependence.

    PubMed

    Lenormand, Hélène; Amar-Bacoup, Fériel; Vincent, Jean-Claude

    2013-01-01

    Hyaluronan (HA) is catalytically hydrolyzed by hyaluronidase (HAase). Depending on pH, HA is able to form a non-productive electrostatic complex with HAase in addition to the classical enzyme-substrate complex. Experiments have shown the strong inhibition of the HA hydrolysis catalyzed by HAase when performed at high HA over HAase concentration ratio and low ionic strength. The substrate-dependence thus shows a non-classic inhibition of HAase at high substrate concentrations due to the sequestration of HAase by HA in the electrostatic complex. The modeling of the HA/HAase system is characteristic of a reaction-complexation coupling and it is very difficult to study reaction or binding, separately. Here, we have established the equation controlling the global system and shown that the substrate-dependence of such a system is a direct combination of a pure Michaelis-Menten equation associated with the reaction and a hyperbolic curve associated with the binding. At low substrate concentrations, the hyperbola, representing the relative part of HAase not sequestered by HA, can be assimilated to a straight line. We have established the relationship between the slope of that straight line and the dissociation constant of the electrostatic HA-HAase complex. Fitting the theoretical equation to the experimental data allowed us to determine, for the first time, the Kd value of the non-productive HA-HAase complex at low ionic strength. Copyright © 2013. Published by Elsevier B.V.

  11. Determining the effects of absorption and aperture size on sound decay in a complex coupled volume system

    NASA Astrophysics Data System (ADS)

    Bradley, David T.; Wang, Lily M.

    2005-09-01

    Coupled volume systems may consist of a large, dry main volume connected to a smaller, reverberant coupled volume through an acoustically transparent opening, known as a coupling aperture. Given the right combination of architectural parameters, a particular sound decay may be obtained in the main volume which exhibits the double-slope effect (DSE). DSE is characterized by a double-slope decay profile with a steep early decay and a shallow reverberant tail. This project focuses on two architectural parameters-absorption ratio between the main and coupled volumes, and aperture size-and how these parameters affect sound decay in a complex coupled volume system. A medium detail level computer model of a generalized imaginary concert hall has been constructed, and the computer modeling program ODEON has been used to predict the room impulse responses for several configurations of the architectural parameters in the model. Binaural auralizations have also been created in ODEON and used in subjective testing to determine the effects of parameter changes on subjective cues. Objective results, based on several DSE quantifiers, will be presented. Corresponding subjective results will also be discussed.

  12. Coordination Complexes of Decamethylytterbocene with4,4'-Disubstituted Bipyridines: An Experimental Study of Spin Coupling inLanthanide Complexes

    SciTech Connect

    Walter, Marc D.; Berg, David J.; Andersen, Richard A.

    2005-12-08

    The paramagnetic 1:1 coordination complexes of (C5Me5)2Ybwith a series of 4,4'-disubstituted bipyridines, bipy-X, where X is Me,tert-Bu, OMe, Ph, CO2Me, and CO2Et have been prepared. All of thecomplexes are paramagnetic and the values of the magnetic susceptibilityas a function of temperature show that these values are less thanexpected for the cation, [(C5Me5)2Yb(III)(bipy-X)]+, which have beenisolated as the cation-anion ion-pairs[(C5Me5)2Yb(III)(bipy-X)]+[(C5Me5)2YbI2]f fnfn where X is CO2Et, OMe andMe. The 1H NMR chemical shifts (293 K) for the methine resonances locatedat the 6,6' site in the bipy-X ring show a linear relationship with thevalues of chiT (300 K) for the neutral complexes which illustrates thatthe molecular behavior does not depend upon the phase with one exception,viz., (C5Me5)2Yb(bipy-Me). Single crystals of the 4,4'-dimethylbipyridinecomplex undergo an irreversible, abrupt first order phase change at 228 Kthat shatters the single crystals. The magnetic susceptibility,represented in a delta vs. T plot, on this complex, in polycrystallineform undergoes reversible abrupt changes in the temperature regime 205 -212 K, which is suggested to be due to the way the individual molec ularunits pack in the unit cell. A qualitative model is proposed thataccounts for the sub-normal magnetic moments in theseytterbocene-bipyridine complexes.

  13. Morphological communication: exploiting coupled dynamics in a complex mechanical structure to achieve locomotion

    PubMed Central

    Rieffel, John A.; Valero-Cuevas, Francisco J.; Lipson, Hod

    2010-01-01

    Traditional engineering approaches strive to avoid, or actively suppress, nonlinear dynamic coupling among components. Biological systems, in contrast, are often rife with these dynamics. Could there be, in some cases, a benefit to high degrees of dynamical coupling? Here we present a distributed robotic control scheme inspired by the biological phenomenon of tensegrity-based mechanotransduction. This emergence of morphology-as-information-conduit or ‘morphological communication’, enabled by time-sensitive spiking neural networks, presents a new paradigm for the decentralized control of large, coupled, modular systems. These results significantly bolster, both in magnitude and in form, the idea of morphological computation in robotic control. Furthermore, they lend further credence to ideas of embodied anatomical computation in biological systems, on scales ranging from cellular structures up to the tendinous networks of the human hand. PMID:19776146

  14. Affinity filtration coupled with capillary-based affinity purification for the isolation of protein complexes.

    PubMed

    Qureshi, M S; Sheikh, Q I; Hill, R; Brown, P E; Dickman, M J; Tzokov, S B; Rice, D W; Gjerde, D T; Hornby, D P

    2013-08-01

    The isolation of complex macromolecular assemblies at the concentrations required for structural analysis represents a major experimental challenge. Here we present a method that combines the genetic power of site-specific recombination in order to selectively "tag" one or more components of a protein complex with affinity-based rapid filtration and a final step of capillary-based enrichment. This modified form of tandem affinity purification produces highly purified protein complexes at high concentrations in a highly efficient manner. The application of the method is demonstrated for the yeast Arp2/3 heptameric protein complex involved in mediating reorganization of the actin cytoskeleton.

  15. Tracking of Maneuvering Complex Extended Object with Coupled Motion Kinematics and Extension Dynamics Using Range Extent Measurements.

    PubMed

    Sun, Lifan; Ji, Baofeng; Lan, Jian; He, Zishu; Pu, Jiexin

    2017-09-22

    The key to successful maneuvering complex extended object tracking (MCEOT) using range extent measurements provided by high resolution sensors lies in accurate and effective modeling of both the extension dynamics and the centroid kinematics. During object maneuvers, the extension dynamics of an object with a complex shape is highly coupled with the centroid kinematics. However, this difficult but important problem is rarely considered and solved explicitly. In view of this, this paper proposes a general approach to modeling a maneuvering complex extended object based on Minkowski sum, so that the coupled turn maneuvers in both the centroid states and extensions can be described accurately. The new model has a concise and unified form, in which the complex extension dynamics can be simply and jointly characterized by multiple simple sub-objects' extension dynamics based on Minkowski sum. The proposed maneuvering model fits range extent measurements very well due to its favorable properties. Based on this model, an MCEOT algorithm dealing with motion and extension maneuvers is also derived. Two different cases of the turn maneuvers with known/unknown turn rates are specifically considered. The proposed algorithm which jointly estimates the kinematic state and the object extension can also be easily implemented. Simulation results demonstrate the effectiveness of the proposed modeling and tracking approaches.

  16. Photochemistry between a ruthenium(II) pyridylimidazole complex and benzoquinone: simple electron transfer versus proton-coupled electron transfer.

    PubMed

    Hönes, Roland; Kuss-Petermann, Martin; Wenger, Oliver S

    2013-02-01

    A ruthenium(II) complex with two 4,4'-bis(trifluoromethyl)-2,2'-bipyridine chelates and a 2-(2'-pyridyl)imidazole ligand was synthesized and characterized by electrochemical and optical spectroscopic means. The respective complex has the potential to act as a combined electron-proton donor when promoted to its long-lived (3)MLCT excited state with visible light. The possibility of proton-coupled electron transfer (PCET) between the ruthenium(II) complex and 1,4-benzoquinone as an electron/proton acceptor was explored by steady-state and time-resolved luminescence spectroscopy, as well as by transient absorption spectroscopy in the nanosecond time regime. Excited-state deactivation is found to occur predominantly via simple oxidative quenching involving no proton motion, but a minor fraction of the photoexcited complex appears to react via PCET since there is spectral evidence for semiquinone as a photoproduct. Presumably, PCET is not kinetically competitive with simple electron transfer because the latter process is sufficiently exergonic and because there is little thermodynamic benefit from coupling proton transfer to the photoinduced electron transfer.

  17. Domain Wall Magnetoresistance and Complex Magnetic Response in Antiferromagnetically Coupled Fe/Cr Multilayers

    DTIC Science & Technology

    2003-01-01

    Antiferromagnetically Coupled Fe/Cr Multilayers F.G.Aliev1, R.Villar1, R.Schad2 and J.L.Martinez 3 (1) Dpto. de Fisica de la Materia Condensada, C-Ill...Universidad Aut6noma de Madrid, 28049, Madrid, Spain (2) CMIT, University of Alabama, Tuscaloosa, USA (3) Instituto de Ciencia de Materiales Madrid

  18. Onset of chaotic phase synchronization in complex networks of coupled heterogeneous oscillators.

    PubMed

    Ricci, Francesco; Tonelli, Roberto; Huang, Liang; Lai, Ying-Cheng

    2012-08-01

    Existing studies on network synchronization focused on complex networks possessing either identical or nonidentical but simple nodal dynamics. We consider networks of both complex topologies and heterogeneous but chaotic oscillators, and investigate the onset of global phase synchronization. Based on a heuristic analysis and by developing an efficient numerical procedure to detect the onset of phase synchronization, we uncover a general scaling law, revealing that chaotic phase synchronization can be facilitated by making the network more densely connected. Our methodology can find applications in probing the fundamental network dynamics in realistic situations, where both complex topology and complicated, heterogeneous nodal dynamics are expected.

  19. The Copper-nicotinamide complex: sustainable applications in coupling and cycloaddition reactions

    EPA Science Inventory

    Crystalline copper (II)-nicotinamide complex, synthesized via simple mixing of copper chloride and nicotinamide solution at room temperature, catalyzes the C-S, C-N bond forming and cycloaddition reactions under a variety of sustainable reaction conditions.

  20. The Copper-nicotinamide complex: sustainable applications in coupling and cycloaddition reactions

    EPA Science Inventory

    Crystalline copper (II)-nicotinamide complex, synthesized via simple mixing of copper chloride and nicotinamide solution at room temperature, catalyzes the C-S, C-N bond forming and cycloaddition reactions under a variety of sustainable reaction conditions.

  1. Modulational instability in a purely nonlinear coupled complex Ginzburg-Landau equations through a nonlinear discrete transmission line.

    PubMed

    Ndzana, Fabien; Mohamadou, Alidou; Kofané, Timoléon C

    2008-12-01

    We study wave propagation in a nonlinear transmission line with dissipative elements. We show analytically that the telegraphers' equations of the electrical transmission line can be modeled by a pair of continuous coupled complex Ginzburg-Landau equations, coupled by purely nonlinear terms. Based on this system, we investigated both analytically and numerically the modulational instability (MI). We produce characteristics of the MI in the form of typical dependence of the instability growth rate on the wavenumbers and system parameters. Generic outcomes of the nonlinear development of the MI are investigated by dint of direct simulations of the underlying equations. We find that the initial modulated plane wave disintegrates into waves train. An apparently turbulent state takes place in the system during the propagation.

  2. FLS-Based Adaptive Synchronization Control of Complex Dynamical Networks With Nonlinear Couplings and State-Dependent Uncertainties.

    PubMed

    Li, Xiao-Jian; Yang, Guang-Hong

    2016-01-01

    This paper is concerned with the problem of synchronization control of complex dynamical networks (CDN) subject to nonlinear couplings and uncertainties. An fuzzy logical system-based adaptive distributed controller is designed to achieve the synchronization. The asymptotic convergence of synchronization errors is analyzed by combining algebraic graph theory and Lyapunov theory. In contrast to the existing results, the proposed synchronization control method is applicable for the CDN with system uncertainties and unknown topology. Especially, the considered uncertainties are allowed to occur in the node local dynamics as well as in the interconnections of different nodes. In addition, it is shown that a unified controller design framework is derived for the CDN with or without coupling delays. Finally, simulations on a Chua's circuit network are provided to validate the effectiveness of the theoretical results.

  3. Stability analysis and synchronization in discrete-time complex networks with delayed coupling.

    PubMed

    Cheng, Ranran; Peng, Mingshu; Yu, Weibin; Sun, Bo; Yu, Jinchen

    2013-12-01

    A new network of coupled maps is proposed in which the connections between units involve no delays but the intra-neural communication does, whereas in the work of Atay et al. [Phys. Rev. Lett. 92, 144101 (2004)], the focus is on information processing delayed by the inter-neural communication. We show that the synchronization of the network depends on not only the intrinsic dynamical features and inter-connection topology (characterized by the spectrum of the graph Laplacian) but also the delays and the coupling strength. There are two main findings: (i) the more neighbours, the easier to be synchronized; (ii) odd delays are easier to be synchronized than even ones. In addition, compared with those discussed by Atay et al. [Phys. Rev. Lett. 92, 144101 (2004)], our model has a better synchronizability for regular networks and small-world variants.

  4. Communication: Relativistic Fock-space coupled cluster study of small building blocks of larger uranium complexes

    SciTech Connect

    Tecmer, Paweł Visscher, Lucas; Severo Pereira Gomes, André; Knecht, Stefan

    2014-07-28

    We present a study of the electronic structure of the [UO{sub 2}]{sup +}, [UO{sub 2}]{sup 2} {sup +}, [UO{sub 2}]{sup 3} {sup +}, NUO, [NUO]{sup +}, [NUO]{sup 2} {sup +}, [NUN]{sup −}, NUN, and [NUN]{sup +} molecules with the intermediate Hamiltonian Fock-space coupled cluster method. The accuracy of mean-field approaches based on the eXact-2-Component Hamiltonian to incorporate spin–orbit coupling and Gaunt interactions are compared to results obtained with the Dirac–Coulomb Hamiltonian. Furthermore, we assess the reliability of calculations employing approximate density functionals in describing electronic spectra and quantities useful in rationalizing Uranium (VI) species reactivity (hardness, electronegativity, and electrophilicity)

  5. Exacerbated vulnerability of coupled socio-economic risk in complex networks

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Feng, Ling; Berman, Yonatan; Hu, Ning; Stanley, H. Eugene

    2016-10-01

    The study of risk contagion in economic networks has most often focused on the financial liquidities of institutions and assets. In practice the agents in a network affect each other through social contagion, i.e., through herd behavior and the tendency to follow leaders. We study the coupled risk between social and economic contagion and find it significantly more severe than when economic risk is considered alone. Using the empirical network from the China venture capital market we find that the system exhibits an extreme risk of abrupt phase transition and large-scale damage, which is in clear contrast to the smooth phase transition traditionally observed in economic contagion alone. We also find that network structure impacts market resilience and that the randomization of the social network of the market participants can reduce system fragility when there is herd behavior. Our work indicates that under coupled contagion mechanisms network resilience can exhibit a fundamentally different behavior, i.e., an abrupt transition. It also reveals the extreme risk when a system has coupled socio-economic risks, and this could be of interest to both policy makers and market practitioners.

  6. Coupling-induced complexity in nephron models of renal blood flow regulation

    PubMed Central

    Laugesen, Jakob L.; Sosnovtseva, Olga V.; Mosekilde, Erik; Holstein-Rathlou, Niels-Henrik

    2010-01-01

    Tubular pressure and nephron blood flow time series display two interacting oscillations in rats with normal blood pressure. Tubuloglomerular feedback (TGF) senses NaCl concentration in tubular fluid at the macula densa, adjusts vascular resistance of the nephron's afferent arteriole, and generates the slower, larger-amplitude oscillations (0.02–0.04 Hz). The faster smaller oscillations (0.1–0.2 Hz) result from spontaneous contractions of vascular smooth muscle triggered by cyclic variations in membrane electrical potential. The two mechanisms interact in each nephron and combine to act as a high-pass filter, adjusting diameter of the afferent arteriole to limit changes of glomerular pressure caused by fluctuations of blood pressure. The oscillations become irregular in animals with chronic high blood pressure. TGF feedback gain is increased in hypertensive rats, leading to a stronger interaction between the two mechanisms. With a mathematical model that simulates tubular and arteriolar dynamics, we tested whether an increase in the interaction between TGF and the myogenic mechanism can cause the transition from periodic to irregular dynamics. A one-dimensional bifurcation analysis, using the coefficient that couples TGF and the myogenic mechanism as a bifurcation parameter, shows some regions with chaotic dynamics. With two nephrons coupled electrotonically, the chaotic regions become larger. The results support the hypothesis that increased oscillator interactions contribute to the transition to irregular fluctuations, especially when neighboring nephrons are coupled, which is the case in vivo. PMID:20147606

  7. Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy

    SciTech Connect

    Slenkamp, Karla M.; Lynch, Michael S.; Van Kuiken, Benjamin E.; Brookes, Jennifer F.; Bannan, Caitlin C.; Daifuku, Stephanie L.; Khalil, Munira

    2014-02-28

    Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (ν{sub CN}) vibrations found in [(NH{sub 3}){sub 5}Ru{sup III}NCFe{sup II}(CN){sub 5}]{sup −} (FeRu) dissolved in D{sub 2}O and formamide and [(NC){sub 5}Fe{sup II}CNPt{sup IV}(NH{sub 3}){sub 4}NCFe{sup II}(CN){sub 5}]{sup 4−} (FePtFe) dissolved in D{sub 2}O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the ν{sub CN} modes in the electronic ground state. The FTIR spectra of the ν{sub CN} modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic ν{sub CN} modes. The vibrational mode anharmonicities of the individual ν{sub CN} modes range from 14 to 28 cm{sup −1}. The mixed-mode anharmonicities range from 2 to 14 cm{sup −1}. In general, the bridging ν{sub CN} mode is most weakly coupled to the radial ν{sub CN} mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four ν{sub CN} modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D{sub 2}O. The ν{sub CN} modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm{sup −1}. This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the ν{sub CN} modes in cyanide-bridged transition metal mixed valence complexes.

  8. Sequestered water and binding energy are coupled in complexes of lambda Cro repressor with non-consensus binding sequences.

    PubMed

    Rau, Donald C

    2006-08-11

    We use the osmotic pressure dependence of dissociation rates and relative binding constants to infer differences in sequestered water among complexes of lambda Cro repressor with varied DNA recognition sequences. For over a 1000-fold change in association constant, the number of water molecules sequestered by non-cognate complexes varies linearly with binding free energy. One extra bound water molecule is coupled with the loss of approximately 150 cal/mol complex in binding free energy. Equivalently, every tenfold decrease in binding constant at constant salt and temperature is associated with eight to nine additional water molecules sequestered in the non-cognate complex. The relative insensitivity of the difference in water molecules to the nature of the osmolyte used to probe the reaction suggests that the water is sterically sequestered. If the previously measured changes in heat capacity for lambda Cro binding to different non-cognate sequences are attributed solely to this change in water, then the heat capacity change per incorporated water is almost the same as the difference between ice and water. The associated changes in enthalpies and entropies, however, indicate that the change in complex structure involves more than a simple incorporation of fixed water molecules that act as adaptors between non-complementary surfaces.

  9. Metal speciation in a complexing soft film layer: a theoretical dielectric relaxation study of coupled chemodynamic and electrodynamic interfacial processes.

    PubMed

    Merlin, Jenny; Duval, Jérôme F L

    2012-04-07

    We report a comprehensive formalism for the dynamics of metal speciation across an interphase formed between a complexing soft film layer and an electrolyte solution containing indifferent ions and metal ions that form complexes with charged molecular ligands distributed throughout the film. The analysis integrates the intricate interplay between metal complexation kinetics and diffusive metal transfer from/toward the ligand film, together with the kinetics of metal electrostatic partitioning across the film/solution interphase. This partitioning is determined by the settling dynamics of the interfacial electric double layer (EDL), as governed by time-dependent conduction-diffusion transports of both indifferent and reactive metal ions. The coupling between such chemodynamic and electrodynamic processes is evaluated via derivation of the dielectric permittivity increment for the ligand film/electrolyte interphase that is perturbed upon application of an ac electric field (pulsation ω) between electrodes supporting the films. The dielectric response is obtained from the ω-dependent distributions of all ions across the ligand film, as ruled by coupled Poisson-Nernst-Planck equations amended for a chemical source term involving the intra-film complex formation and dissociation pulsations (ω(a) and ω(d) respectively). Dielectric spectra are discussed for bare and film coated-electrodes over a wide range of field pulsations and Deborah numbers De = ω(a,d)/ω(diff), where ω(diff) is the electric double layer relaxation pulsation. The frequency-dependent dynamic or inert character of the formed metal complexes is then addressed over a time window that ranges from transient to fully relaxed EDL. The shape and magnitude of the dielectric spectra are further shown to reflect the lability of dynamic complexes, i.e. whether the overall speciation process at a given pulsation ω is primarily rate-limited either by complexation kinetics or by ion-transport dynamics. The

  10. Structure identification of an uncertain network coupled with complex-variable chaotic systems via adaptive impulsive control

    NASA Astrophysics Data System (ADS)

    Liu, Dan-Feng; Wu, Zhao-Yan; Ye, Qing-Ling

    2014-04-01

    In this paper, structure identification of an uncertain network coupled with complex-variable chaotic systems is investigated. Both the topological structure and the system parameters can be unknown and need to be identified. Based on impulsive stability theory and the Lyapunov function method, an impulsive control scheme combined with an adaptive strategy is adopted to design effective and universal network estimators. The restriction on the impulsive interval is relaxed by adopting an adaptive strategy. Further, the proposed method can monitor the online switching topology effectively. Several numerical simulations are provided to illustrate the effectiveness of the theoretical results.

  11. Dynamical complexity of multipoint geospace observations related to magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Balasis, Georgios; Daglis, Ioannis A.; Papadimitriou, Constantinos; Donner, Reik; Runge, Jakob

    2016-07-01

    We explore, evaluate and compare the applicability, effectiveness and interdisciplinary character of a variety of modern and sophisticated methods, from complex systems sciences, for the investigation of dynamical complexity of the near-Earth electromagnetic environment. We identify and inter-compare complementary analysis concepts, allowing for a systematic study of geospace magnetic storms and magnetospheric substorms and regime shifts between normal and abnormal states of the Earth's magnetic field, based on observational data from both ground and space. We expect these concepts to allow identifying previously unrecognized precursory structures in the dynamical complexity and, thus, contribute to a better understanding of dynamical processes manifested in observable magnetic field fluctuations prior to possible space weather-related hazards.

  12. Passivity of Directed and Undirected Complex Dynamical Networks With Adaptive Coupling Weights.

    PubMed

    Wang, Jin-Liang; Wu, Huai-Ning; Huang, Tingwen; Ren, Shun-Yan; Wu, Jigang

    2016-05-05

    A complex dynamical network consisting of $N$ identical neural networks with reaction-diffusion terms is considered in this paper. First, several passivity definitions for the systems with different dimensions of input and output are given. By utilizing some inequality techniques, several criteria are presented, ensuring the passivity of the complex dynamical network under the designed adaptive law. Then, we discuss the relationship between the synchronization and output strict passivity of the proposed network model. Furthermore, these results are extended to the case when the topological structure of the network is undirected. Finally, two examples with numerical simulations are provided to illustrate the correctness and effectiveness of the proposed results.

  13. Solitary wave solutions and modulational instability in a system of coupled complex Newell-Segel-Whitehead equations

    NASA Astrophysics Data System (ADS)

    Kelkar, Asawari; Yomba, Emmanuel; Djellouli, Rabia

    2016-12-01

    By virtue of the modulational instability (MI) and phase amplitude ansatz approach, a system of coupled complex Newell-Segel-Whitehead equations (NSWEs), which describes isotropic systems near a subcritical oscillatory instability, is investigated. The constraints that allow the MI procedure to transform the system under consideration into a study of the roots of a polynomial equation of the fourth degree are obtained. A number of examples are analyzed graphically, to overcome the complexity of the dispersion relation and its dependence on many parameters. The existence of a variety of MI gain spectrum is observed. The influence of the cubic-quintic nonlinearity and the magnitude of the plane wave solutions of the system on the MI are also analyzed. Various novel solitary-wave solutions of the system, such as bright-bright, dark-dark, and dark-bright wave solutions, are analytically obtained using direct approach under some constraint conditions.

  14. Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes

    SciTech Connect

    Andersen, Richard; Walter, Marc D.; Berg, David J.; Andersen, Richard A.

    2006-11-04

    The paramagnetic 1:1 coordination complexes of (C5Me5)2Yb with a series of diazabutadiene ligands, RN=C(R')C(R')=NR, where R= CMe3, CHMe2, adamantyl, p-tolyl, p-anisyl, and mesityl when R'=H, and R= p-anisyl when R'= Me, have been prepared. The complexes are paramagnetic, but their magnetic moments are less than expected for the two uncoupled spin carriers, (C5Me5)2Yb(III, 4f13) and the diazabutadiene radical anions (S=1/2), which implies exchange coupling between the spins. The variable temperature 1H NMR spectra show that rotation about the R-N bond is hindered and these barriers are estimated. The barriers are largely determined by steric effects but electronic effects are not unimportant.

  15. Parity-time symmetric complex-coupled distributed feedback laser with excellent immunity to external optical feedback

    NASA Astrophysics Data System (ADS)

    Ke, Cheng; Li, Xun; Xi, Yanping

    2017-03-01

    In this paper, we propose an external optical feedback resistant distributed feedback (DFB) laser diode (LD) by exploiting parity-time symmetric complex coupling. With its complex refractive index followed a parity-time symmetry, the grating shows a strongly asymmetric reflection to the contra-propagating light inside the DFB cavity, which effectively rejects the returning light from one end. Consequently, the DFB LD is much less sensitive to external optical feedback. On the contrary, the transmissivity of such grating is still symmetric so that the output light of the DFB LD is not affected. Numerical simulation result shows that the lasing wavelength drift can be less than 0.2 nm with a SMSR exceeding 45 dB under a coherent external optical feedback as high as -10 dB.

  16. Trinuclear copper complexes with triplesalen ligands: geometric and electronic effects on ferromagnetic coupling via the spin-polarization mechanism.

    PubMed

    Glaser, Thorsten; Heidemeier, Maik; Strautmann, Julia B H; Bögge, Hartmut; Stammler, Anja; Krickemeyer, Erich; Huenerbein, Robert; Grimme, Stefan; Bothe, Eberhard; Bill, Eckhard

    2007-01-01

    (+) is strongly stabilized with respect to reference mononuclear salen-like Cu complexes. Chemical one-electron oxidation of 2 to 2(+) allows the determination of its UV/Vis/NIR spectrum, which indicates a ligand-centered oxidation that can be assigned to the central phloroglucinol unit by analogy with the trinuclear Ni triplesalen series. Delocalization of this oxidation over three Cu(II)-phenolate subunits causes the observed energetic stabilization of 2(+). Temperature-dependent magnetic susceptibility measurements reveal ferromagnetic couplings for all three trinuclear Cu(II) triplesalen complexes. The trend of the coupling constants can be rationalized by two opposing effects: 1) electron-withdrawing terminal substituents stabilize the central Cu(II)-phenolate bond, which results in a stronger coupling, and 2) ligand folding around the central Cu(II)-phenolate bond opens a bonding pathway between the magnetic Cu(II) d(x(2)-y(2) ) orbital and the phenolate O p(z) orbital, which results in a stronger coupling. Density functional calculations indicate that both spin-polarization and spin-delocalization are operative and that slight geometric variations alter their relative magnitudes.

  17. Deformation coupling between the Archean Pukaskwa intrusive complex and the Hemlo shear zone, Superior Province, Canada

    NASA Astrophysics Data System (ADS)

    Liodas, Nathaniel T.; Gébelin, Aude; Ferré, Eric C.; Misgna, Girmay M.

    2013-11-01

    Archean greenstone belts typically form narrow sheared basins separating bulbous tonalo-trondjhemo-granodioritic (TTG) intrusive complexes. The role played by gravity in the development of such dome-and-keel structures constitutes a key question in Archean tectonics. The Pukaskwa intrusive complex (PIC)-Hemlo greenstone belt system stands as a remarkable example of the dome-and-keel architecture that commonly occurs in Archean terrains. Abundant strain markers in the greenstone belt and in the Hemlo shear zone (HSZ) attest of late sinistral strike-slip kinematics (D2) whereas, in general, the quartzofeldspathic coarse-grained rocks of the Pukaskwa intrusive complex bear little macroscopically visible kinematic indicators, most likely due to pervasive recrystallization. The PIC consists dominantly of a heterogeneous assemblage of TTG plutonic rocks and gneisses, which overall are less dense than the greenstone rocks. The study of anisotropy of magnetic susceptibility (AMS), based on 120 stations and 1947 specimens from the PIC, reveals east-west trending prolate and plano-linear fabrics across the northern margin of the complex, i.e., along the HSZ. Since geotherms were higher in the Archean than in the present, the effective viscosity of the TTG units would have been sufficiently low to allow their diapiric ascent through denser greenstone rocks. Here we propose an alternative model where thrust tectonics is responsible for the early structuration of the PIC. Later transpressive tectonics causes strain localization along internal strike-slip shear zones and along lithological boundaries.

  18. Complex dynamics of an oscillator ensemble with uniformly distributed natural frequencies and global nonlinear coupling

    NASA Astrophysics Data System (ADS)

    Baibolatov, Yernur; Rosenblum, Michael; Zhanabaev, Zeinulla Zh.; Pikovsky, Arkady

    2010-07-01

    We consider large populations of phase oscillators with global nonlinear coupling. For identical oscillators such populations are known to demonstrate a transition from completely synchronized state to the state of self-organized quasiperiodicity. In this state phases of all units differ, yet the population is not completely incoherent but produces a nonzero mean field; the frequency of the latter differs from the frequency of individual units. Here we analyze the dynamics of such populations in case of uniformly distributed natural frequencies. We demonstrate numerically and describe theoretically (i) states of complete synchrony, (ii) regimes with coexistence of a synchronous cluster and a drifting subpopulation, and (iii) self-organized quasiperiodic states with nonzero mean field and all oscillators drifting with respect to it. We analyze transitions between different states with the increase of the coupling strength; in particular we show that the mean field arises via a discontinuous transition. For a further illustration we compare the results for the nonlinear model with those for the Kuramoto-Sakaguchi model.

  19. Targeted ferromagnetic coupling in a trinuclear copperII complex: analysis of the St = 3/2 spin ground state.

    PubMed

    Glaser, Thorsten; Heidemeier, Maik; Grimme, Stefan; Bill, Eckhard

    2004-08-23

    The trinuclear Cu(II) complex [(talen)Cu(II)(3)] (1) using the new triplesalen ligand H(6)talen has been synthesized and structurally characterized. The three Cu(II) ions are bridged in a m-phenylene linkage by the phloroglucinol backbone of the ligand. This m-phenylene bridging mode results in ferromagnetic couplings with an S(t) = (3)/(2) spin ground state, which has been analyzed by means of EPR spectroscopy and DFT calculations. The EPR spectrum exhibits an unprecedented pattern of 10 hyperfine lines due to the coupling of three Cu(II) ions (I = (3)/(2)). Resonances around g = 4 in both perpendicular and parallel mode EPR spectra demonstrate a zero-field splitting of D approximately 74 x 10(-4) cm(-1) arising from anisotropic/antisymmetric exchange interactions. The DFT calculations show an alteration in the sign of the spin densities of the central benzene ring corroborating the spin-polarization mechanism as origin for the ferromagnetic coupling.

  20. Assessment of the CCSD and CCSD(T) Coupled-Cluster Methods in Calculating Heats of Formation for Zn Complexes

    PubMed Central

    Weaver, Michael N.; Yang, Yue

    2010-01-01

    Heats of formation were calculated using coupled-cluster methods for a series of zinc complexes. The calculated values were evaluated against previously conducted computational studies using density functional methods as well as experimental values. Heats of formation for nine neutral ZnXn complexes [X = -Zn, -H, -O, -F2, -S, -Cl, -Cl2, -CH3, (-CH3)2] were determined at the CCSD and CCSD(T) levels using the 6–31G** and TZVP basis sets, as well as the LANL2DZ-6–31G** (LACVP**) and LANL2DZ-TZVP hybrid basis sets. The CCSD(T)/6–31G** level of theory was found to predict the heat of formation for the non-alkyl Zn complexes most accurately. The alkyl Zn species were problematic in that none of the methods that were tested accurately predicted the heat of formation for these complexes. For the seven non-alkyl species, the CCSD(T)/6–31G** level of theory was shown to predict the most accurate heat of formation values. In instances where experimental geometric parameters were available, these were most accurately predicted by the CCSD/6–31G** level of theory; going to CCSD(T) did not improve agreement with the experimental values. PMID:19691272

  1. The coupling of carbon dioxide and epoxides by phenanthroline derivatives containing different Cu(II) complexes as catalyst.

    PubMed

    Kilic, Ahmet; Palali, Ahmet Arif; Durgun, Mustafa; Tasci, Zeynep; Ulusoy, Mahmut

    2013-09-01

    A series of the mononuclear Cu(II) metal complexes containing the ligand Bdppz [(9a,13a-dihydro-4,5,9,14-tetraaza-benzo[b]triphenylene-11-yl)-phenyl-methanone] (L1) and Aqphen [(12,17-dihydronaphthol[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione)] (L2) were synthesized and used as catalyst for the coupling of carbon dioxide (CO2) and liquid epoxide which served as both reactant and solvent. Dimethylamino pyridine (DMAP) was used as co-catalyst. The yields of epoxides to corresponding cyclic carbonates were determined by comparing the ratio of product to substrate in the (1)H NMR spectrum of an aliquot of the reaction mixture. The mononuclear Cu(II) complexes of these ligands were synthesized by treating an ethanol solvent of the appropriate ligand with a different molar amount of CuCl2·2H2O. The Cu(II) complexes were characterized by FT-IR, UV-Vis, elemental analysis, melting point analysis, mass spectra, molar conductivity measurements and magnetic susceptibility techniques. The reaction of the Bdppz and Aqphen ligands in a 1:1, 1:2 or 1:3 mole ratio with CuCl2·2H2O afforded ionic Cu(II) complexes in the presence of Et3N.

  2. Boson stars in a theory of complex scalar fields coupled to the U(1) gauge field and gravity

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjeev; Kulshreshtha, Usha; Shankar Kulshreshtha, Daya

    2014-08-01

    We study boson shells and boson stars in a theory of a complex scalar field coupled to the U(1) gauge field {{A}_{\\mu }} and Einstein gravity with the potential V(|\\Phi |)\\;:=\\frac{1}{2}{{m}^{2}}{{\\left( |\\Phi |+a \\right)}^{2}}. This could be considered either as a theory of a massive complex scalar field coupled to an electromagnetic field and gravity in a conical potential, or as a theory in the presence of a potential that is an overlap of a parabolic and conical potential. Our theory has a positive cosmological constant (\\Lambda :=4\\pi G{{m}^{2}}{{a}^{2}}). Boson stars are found to come in two types, having either ball-like or shell-like charge density. We studied the properties of these solutions and also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.

  3. SPOP-containing complex regulates SETD2 stability and H3K36me3-coupled alternative splicing

    PubMed Central

    Zhu, Kun; Lei, Pin-Ji; Ju, Lin-Gao; Wang, Xiang; Huang, Kai; Yang, Bo; Shao, Changwei; Zhu, Yuan; Wei, Gang; Fu, Xiang-Dong; Li, Lianyun; Wu, Min

    2017-01-01

    Trimethylation of histone H3K36 is a chromatin mark associated with active gene expression, which has been implicated in coupling transcription with mRNA splicing and DNA damage response. SETD2 is a major H3K36 trimethyltransferase, which has been implicated as a tumor suppressor in mammals. Here, we report the regulation of SETD2 protein stability by the proteasome system, and the identification of SPOP, a key subunit of the CUL3 ubiquitin E3 ligase complex, as a SETD2-interacting protein. We demonstrate that SPOP is critically involved in SETD2 stability control and that the SPOP/CUL3 complex is responsible for SETD2 polyubiquitination both in vivo and in vitro. ChIP-Seq analysis and biochemical experiments demonstrate that modulation of SPOP expression confers differential H3K36me3 on SETD2 target genes, and induce H3K36me3-coupled alternative splicing events. Together, these findings establish a functional connection between oncogenic SPOP and tumor suppressive SETD2 in the dynamic regulation of gene expression on chromatin. PMID:27614073

  4. Investigation of organic magnetoresistance dependence on spin-orbit coupling using 8-hydroxyquinolinate rare-earth based complexes

    SciTech Connect

    Carvalho, R. S.; Ávila, H. C.; Cremona, M.; Costa, D. G.; Paolini, T. B.; Brito, H. F.; Capaz, Rodrigo B.

    2016-05-16

    The recently discovered organic magnetoresistance effect (OMAR) reveals the spin-dependent behavior of the charge transport in organic semiconductors. So far, it is known that hyperfine interactions play an important role in this phenomenon and also that spin-orbit coupling is negligible for light-atom based compounds. However, in the presence of heavy atoms, spin-orbit interactions should play an important role in OMAR. It is known that these interactions are responsible for singlet and triplet states mixing via intersystem crossing and the change of spin-charge relaxation time in the charge mobility process. In this work, we report a dramatic change in the OMAR effect caused by the presence of strong intramolecular spin-orbit coupling in a series of rare-earth quinolate organic complex-based devices. Our data show a different OMAR lineshape compared with the OMAR lineshape of tris(8-hydroxyquinolinate) aluminum-based devices, which are well described in the literature. In addition, electronic structure calculations based on density functional theory help to establish the connection between this results and the presence of heavy central ions in the different complexes.

  5. Investigation of organic magnetoresistance dependence on spin-orbit coupling using 8-hydroxyquinolinate rare-earth based complexes

    NASA Astrophysics Data System (ADS)

    Carvalho, R. S.; Costa, D. G.; Ávila, H. C.; Paolini, T. B.; Brito, H. F.; Capaz, Rodrigo B.; Cremona, M.

    2016-05-01

    The recently discovered organic magnetoresistance effect (OMAR) reveals the spin-dependent behavior of the charge transport in organic semiconductors. So far, it is known that hyperfine interactions play an important role in this phenomenon and also that spin-orbit coupling is negligible for light-atom based compounds. However, in the presence of heavy atoms, spin-orbit interactions should play an important role in OMAR. It is known that these interactions are responsible for singlet and triplet states mixing via intersystem crossing and the change of spin-charge relaxation time in the charge mobility process. In this work, we report a dramatic change in the OMAR effect caused by the presence of strong intramolecular spin-orbit coupling in a series of rare-earth quinolate organic complex-based devices. Our data show a different OMAR lineshape compared with the OMAR lineshape of tris(8-hydroxyquinolinate) aluminum-based devices, which are well described in the literature. In addition, electronic structure calculations based on density functional theory help to establish the connection between this results and the presence of heavy central ions in the different complexes.

  6. The apical complex couples cell fate and cell survival to cerebral cortical development

    PubMed Central

    Kim, Seonhee; Lehtinen, Maria K.; Sessa, Alessandro; Zappaterra, Mauro; Cho, Seo-Hee; Gonzalez, Dilenny; Boggan, Brigid; Austin, Christina A.; Wijnholds, Jan; Gambello, Michael J.; Malicki, Jarema; LaMantia, Anthony S.; Broccoli, Vania; Walsh, Christopher A.

    2010-01-01

    Cortical development depends upon tightly controlled cell fate and cell survival decisions that generate a functional neuronal population, but the coordination of these two processes is poorly understood. Here we show that conditional removal of a key apical complex protein, Pals1, causes premature withdrawal from the cell cycle, inducing excessive generation of early-born postmitotic neurons followed by surprisingly massive and rapid cell death, leading to the abrogation of virtually the entire cortical structure. Pals1 loss shows exquisite dosage sensitivity, so that heterozygote mutants show an intermediate phenotype on cell fate and cell death. Loss of Pals1 blocks essential cell survival signals, including the mammalian target of rapamycin (mTOR) pathway, while mTORC1 activation partially rescues Pals1 deficiency. These data highlight unexpected roles of the apical complex protein Pals1 in cell survival through interactions with mTOR signaling. PMID:20399730

  7. Non-double-couple earthquake mechanisms at the Hengill-Grensdalur volcanic complex, southwest Iceland

    USGS Publications Warehouse

    Julian, B.R.; Miller, A.D.; Foulger, G.R.

    1997-01-01

    The Hengill-Grensdalur area in Iceland generates frequent small non-double-couple earthquakes with explosive volumetric components. We collected high quality three-component digital recordings of 4,000 earthquakes on a purpose-designed, 32-station network in 1991, and determined focal mechanisms for 100 of the best-recorded earthquakes by inverting amplitude ratios. Many of the mechanisms are consistent, within the errors, with simultaneous shear and tensile faulting, with tensile faults parallel to the local spreading ridge, and shear faulting similar to that in the South Iceland transform-fault zone. Some events cannot be explained by this model, however, and require other processes, such as crack closing and partial compensation of tensile cracks by fluid flow.

  8. Coupling of single, double, and triple-decker metal-phthalocyanine complexes to ferromagnetic and antiferromagnetic substrates

    NASA Astrophysics Data System (ADS)

    Lodi Rizzini, Alberto; Krull, Cornelius; Mugarza, Aitor; Balashov, Timofey; Nistor, Corneliu; Piquerel, Raoul; Klyatskaya, Svetlana; Ruben, Mario; Sheverdyaeva, Polina M.; Moras, Paolo; Carbone, Carlo; Stamm, Christian; Miedema, Piter S.; Thakur, Pardeep K.; Sessi, Violetta; Soares, Marcio; Yakhou-Harris, Flora; Cezar, Julio C.; Stepanow, Sebastian; Gambardella, Pietro

    2014-12-01

    We report a survey of the magnetic properties of metal-organic complexes coupled to ferromagnetic and antiferromagnetic surfaces. Using element-resolved X-ray magnetic circular dichroism, we investigate the magnetism of single, double, and triple-decker phthalocyanines focusing on MnPc, TbPc2, and Tb2Pc3 deposited on Ni, Mn, and CoO thin films. Depending on the number of Pc ligands, we find that the metal ions within the molecules couple either parallel or antiparallel to a ferromagnetic substrate. Whereas single-decker complexes such as MnPc form a unique magnetic entity with ferromagnetic films, the intrinsic single molecule magnet properties of TbPc2 and Tb2Pc3 remain largely unaltered. TbPc2 deposited on perpendicularly magnetized Ni films exhibits enhanced magnetic stability compared to TbPc2 in molecular crystals, opposite to TbPc2 deposited on in-plane magnetized Ni. Depending on the competition between uniaxial anisotropy, superexchange, and Zeeman interaction, the magnetic moment of TbPc2 can be aligned parallel or antiparallel to that of the substrate by modulating the intensity of an external magnetic field. This occurs also for Tb2Pc3, but the substrate-induced exchange coupling in triple-decker molecules is found to be short-ranged, that is, limited to the Tb ion closer to the ferromagnetic surface. Finally, we discuss the conditions required to establish exchange bias between molecules and antiferromagnetic substrates. We show that TbPc2 deposited on antiferromagnetic Mn thin films exhibits both exchange bias and enhanced coercivity when field cooled parallel to the out-of-plane easy axis. However, exchange bias does not extend to all molecules on the surface. On oxide antiferromagnets such as CoO we find no evidence of exchange bias for either TbPc2 or MnPc.

  9. Mixed (phthalocyaninato)(Schiff-base) di-dysprosium sandwich complexes. Effect of magnetic coupling on the SMM behavior.

    PubMed

    Wang, Hailong; Liu, Chenxi; Liu, Tao; Zeng, Suyuan; Cao, Wei; Ma, Qi; Duan, Chunying; Dou, Jianmin; Jiang, Jianzhuang

    2013-11-21

    Reaction between Schiff-base ligand and half-sandwich complex M(Pc)(acac) led to the isolation of new sandwich-type mixed (phthalocyaninato)(Schiff-base) di-lanthanide compounds M2(Pc)2(L)H2O (M = Dy, Gd) (1, 2) [H2Pc = metal free phthalocyanine, Hacac = acetylacetone, H2L = N,N'-bis(3-methyloxysalicylidene)benzene-1,2-diamine] with the triple-decker molecular structure clearly revealed by single crystal X-ray diffraction analysis. For the comparative studies, sandwich triple-decker analogues with pure Schiff-base ligand M2(L)3H2O (M = Dy, Gd) (3, 4) were also prepared. Dynamic magnetic measurement result reveals the single-molecule magnet (SMM) nature of the di-dysprosium derivative 1, while the static magnetic investigation over both pure and the diamagnetic diluted samples of this compound discloses the interionic ferromagnetic coupling between the two dysprosium ions, which in turn effectively suppresses the QTM and enhances the energy barrier of this SMM. Nevertheless, comparative studies over the static magnetic properties of the di-dysprosium triple-decker complexes 1 and 3 indicate the stronger magnetic coupling between the two lanthanide ions in mixed (phthalocyaninato)(Schiff-base) species than in the pure Schiff-base triple-decker analogue, suggesting the special coordination sphere around the dysprosium ions in the former compound over the latter one on the more intense inter-ionic ferromagnetic coupling. As a very small step towards understanding the structure-property relationship, the present result will be surely helpful for the design and synthesis of the multinuclear lanthanide-based SMMs with good properties.

  10. Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

    SciTech Connect

    Morozov, Vitaly A.; Petrova, Marina V.; Lukzen, Nikita N.

    2015-08-15

    Family of “breathing crystals” is the polymer-chain complexes of Cu(hfac){sub 2} with nitroxides. The polymer chains consist of one-, two- or three-spin clusters. The “breathing crystals” experience simultaneous magnetic and Jahn-Teller type structural phase transitions with change of total cluster spin and drastic change of bond lengths (ca. 10-12%). For the first time the intra-cluster magnetic couplings in ”breathing crystals” have been calculated both by band structure methods GGA + U and hybrid DFT (B3LYP and PBE0) for the isolated exchange clusters. The temperature dependence of the magnetic coupling constant was calculated for two polymer-chain compounds of the “breathing crystal” family - C{sub 21}H{sub 19}CuF{sub 12}N{sub 4}O{sub 6} with the chains containing two-spin clusters and C{sub 22}H{sub 21}CuF{sub 12}N{sub 4}O{sub 6} with the chains of alternating three-spin clusters and one-spin sites. It was found that adding a Hubbard-like parameter not only to the copper 3d electrons but also to the oxygen 2p electrons (GGA + U{sub d} + U{sub p} approach) results in an improved description of exchange coupling in the “breathing crystal” compounds. At the same time treatment of the isolated clusters by a large basis hybrid DFT with high computational cost provides a similar quality fit of the experimental magneto-chemical data as that for the GGA + U{sub d} + U{sub p} band structure calculation scheme. Our calculations also showed that in spite of the abrupt transformation of the magnetic coupling constant under the phase transition, the band gap in the “breathing crystals” remains about the same value with temperature decrease.

  11. Palladium complexes with a tridentate PNO ligand. Synthesis of eta1-allyl complexes and cross-coupling reactions promoted by boron compounds.

    PubMed

    Crociani, Bruno; Antonaroli, Simonetta; Burattini, Marcello; Paoli, Paola; Rossi, Patrizia

    2010-04-21

    The iminophosphine 2-(2-Ph(2)P)C(6)H(4)N=CHC(6)H(4)OH (P-N-OH) reacts with [Pd(mu-Cl)(eta(3)-C(3)H(5))](2) yielding [PdCl(P-N-O)] and propene. In the presence of NEt(3), the reaction of P-N-OH with [Pd(mu-Cl)(eta(3)-1-R(1),3-R(2)C(3)H(3))](2) (R(1) = R(2) = H, Ph; R(1) = H, R(2) = Ph) affords the eta(1)-allyl derivatives [Pd(eta(1)-1-R(1),3-R(2)C(3)H(3))](P-N-O)] (R(1) = R(2) = H: 1; R(1) = H, R(2) = Ph: 2; R(1) = R(2) = Ph: 3). In solution, the complexes 1 and 3 undergo a slow dynamic process which interconverts the bonding site of the allyl ligand. The X-ray structural analysis of 1 indicates a square-planar coordination geometry around the palladium centre with a P,N,O,-tridentate ligand and a sigma bonded allyl group. The complexes [PdR(P-N-O)] (R = C(6)H(4)Me-4, C[triple bond]CPh) react slowly with p-bromoanisole in the presence of p-tolylboronic acid to give [PdBr(P-N-O)] and the coupling product RC(6)H(4)OMe-4. The latter reactions also proceed at a low rate under catalytic conditions. The coupling of allyl bromide with p-tolylboronic acid is catalyzed by [PdCl(P-N-O)]/K(2)CO(3) to give 4-allyltoluene.

  12. Prion Protein—Antibody Complexes Characterized by Chromatography-Coupled Small-Angle X-Ray Scattering

    PubMed Central

    Carter, Lester; Kim, Seung Joong; Schneidman-Duhovny, Dina; Stöhr, Jan; Poncet-Montange, Guillaume; Weiss, Thomas M.; Tsuruta, Hiro; Prusiner, Stanley B.; Sali, Andrej

    2015-01-01

    Aberrant self-assembly, induced by structural misfolding of the prion proteins, leads to a number of neurodegenerative disorders. In particular, misfolding of the mostly α-helical cellular prion protein (PrPC) into a β-sheet-rich disease-causing isoform (PrPSc) is the key molecular event in the formation of PrPSc aggregates. The molecular mechanisms underlying the PrPC-to-PrPSc conversion and subsequent aggregation remain to be elucidated. However, in persistently prion-infected cell-culture models, it was shown that treatment with monoclonal antibodies against defined regions of the prion protein (PrP) led to the clearing of PrPSc in cultured cells. To gain more insight into this process, we characterized PrP-antibody complexes in solution using a fast protein liquid chromatography coupled with small-angle x-ray scattering (FPLC-SAXS) procedure. High-quality SAXS data were collected for full-length recombinant mouse PrP [denoted recPrP(23–230)] and N-terminally truncated recPrP(89–230), as well as their complexes with each of two Fab fragments (HuM-P and HuM-R1), which recognize N- and C-terminal epitopes of PrP, respectively. In-line measurements by fast protein liquid chromatography coupled with SAXS minimized data artifacts caused by a non-monodispersed sample, allowing structural analysis of PrP alone and in complex with Fab antibodies. The resulting structural models suggest two mechanisms for how these Fabs may prevent the conversion of PrPC into PrPSc. PMID:26287631

  13. An alternative to fully coupled reactive transport simulations for long-term prediction of chemical reactions in complex geological systems

    NASA Astrophysics Data System (ADS)

    De Lucia, Marco; Kempka, Thomas; Kühn, Michael

    2014-05-01

    Fully-coupled reactive transport simulations involving multiphase hydrodynamics and chemical reactions in heterogeneous settings are extremely challenging from a computational point of view. This often leads to oversimplification of the investigated system: coarse spatial discretization, to keep the number of elements in the order of few thousands; simplified chemistry, disregarding many potentially important reactions. A novel approach for coupling non-reactive hydrodynamic simulations with the outcome of single batch geochemical simulations was therefore introduced to assess the potential long-term mineral trapping at the Ketzin pilot site for underground CO2 storage in Germany [1],[2]. The advantage of the coupling is the ability to use multi-million grid non-reactive hydrodynamics simulations on one side and few batch 0D geochemical simulations on the other, so that the complexity of both systems does not need to be reduced. This contribution shows the approach which was taken to validate this simplified coupling scheme. The procedure involved batch simulations of the reference geochemical model, then performing both non-reactive and fully coupled 1D and 3D reactive transport simulations and finally applying the simplified coupling scheme based on the non-reactive and geochemical batch model. The TOUGHREACT/ECO2N [3] simulator was adopted for the validation. The degree of refinement of the spatial grid and the complexity and velocity of the mineral reactions, along with a cut-off value for the minimum concentration of dissolved CO2 allowed to originate precipitates in the simplified approach were found out to be the governing parameters for the convergence of the two schemes. Systematic discrepancies between the approaches are not reducible, simply because there is no feedback between chemistry and hydrodynamics, and can reach 20 % - 30 % in unfavourable cases. However, even such discrepancy is completely acceptable, in our opinion, given the amount of

  14. The Relationship Between Torsion and Anisotropic Exchange Coupling in a Tb(III)-Radical Complex

    NASA Astrophysics Data System (ADS)

    Baker, Michael L.; Tanaka, Takuya; Kawamura, Seiko; Nakajima, Kenji; Ishida, Takayuki; Nojiri, Hiroyuki

    2015-03-01

    The incorporation of paramagnetic ligands within anisotropic rare earth ion clusters has provided significant advance to the design of single molecule magnets with large blocking temperatures. The exchange interaction in such systems is complex, difficult to probe, and little is known about structural relations. Inelastic neutron scattering and sub-THz electron paramagnetic resonance are used complimentary to investigate the large exchange interaction between a rare earth - radical pair in the Tb(hfac)3(2pyNO) complex. Two molecular species exhibiting different Tb-O-N-C torsion angles of the paramagnetic 2pyNO ligand are compared. Antiferromagnetic Ising type 2 p - 4 f exchange is determined for a low torsion angle (3.8 degrees) species. A different species with a larger torsion angle (15.8 degrees) is found to have weaker antiferromagnetic exchange and a non-degenerate ground state doublet. The origin of degeneracy lifting is due to an in-plane ferromagnetic component to the exchange matrix originating from 2 p - 5 d charge transfer rather than a Dzyaloshinski-Moriya interaction. Supported by the Japanese society for the promotion of science and J-PARC.

  15. Export and transport of tRNA are coupled to a multi-protein complex.

    PubMed Central

    Kruse, C; Willkomm, D K; Grünweller, A; Vollbrandt, T; Sommer, S; Busch, S; Pfeiffer, T; Brinkmann, J; Hartmann, R K; Müller, P K

    2000-01-01

    Vigilin is a ubiquitous multi heterogeneous nuclear ribonucleoprotein (hnRNP) K homologous (KH)-domain protein. Here we demonstrate that purified recombinant human vigilin binds tRNA molecules with high affinity, although with limited specificity. Nuclear microinjection experiments revealed for the first time that the immuno-affinity-purified nuclear vigilin core complex (VCC(N)) as well as recombinant vigilin accelerate tRNA export from the nucleus in human cells. The nuclear tRNA receptor exportin-t is part of the VCC(N). Elongation factor (EF)-1alpha is enriched in VCC(N) and its cytoplasmic counterpart VCC(C), whereas EF-1beta, EF-1gamma and EF-1delta are basically confined to the VCC(C). Our results suggest further that vigilin and exportin-t might interact during tRNA export, provide evidence that the channeled tRNA cycle is already initiated in the nucleus, and illustrate that intracellular tRNA trafficking is associated with discrete changes in the composition of cellular cytoplasmic multi-protein complexes containing tRNA. PMID:10657246

  16. Synthesis of a complex nanostructure of CuO via a coupled chemical route

    NASA Astrophysics Data System (ADS)

    Sabeeh, Sabah H.; Abed Hussein, Hashim; Kadhim Judran, Hadia

    2016-12-01

    In the present study, we report the preparation of CuO nanopowder by using a coupled chemical method, namely sol-gel/hydrothermal processes. The product of the first stage process (i.e. sol-gel) was a nanocomposite of Cu(OH)2/SDS, while the product of the second stage (i.e. hydrothermal) was a pure phase of CuO nanopowder. The structure and morphology of the prepared samples was characterized using x-ray diffraction analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive x-ray analysis. The CuO nanostructure assemblies obtained are similar to flower-like structures with intricate geometry. The size of CuO prolate spheroids ranges from 500 nm to 700 nm when they are measured according to a major axis, while they range from 120 nm to 450 nm when the measurement is carried out according to a minor axis. The mechanism growth was explained on the basis of chemical reactions and the role of each reactant in the formation the CuO nanostructure.

  17. Complex Coupling of Air Quality and Climate-Relevant Aerosols in a Chemistry-Aerosol Microphysics Model

    NASA Astrophysics Data System (ADS)

    Yoshioka, M.; Carslaw, K. S.; Reddington, C.; Mann, G.

    2013-12-01

    Controlling emissions of aerosols and their precursors to improve air quality will impact the climate through direct and indirect radiative forcing. We have investigated the impacts of changes in a range of aerosol and gas-phase emission fluxes and changes in temperature on air quality and climate change metrics using a global aerosol microphysics and chemistry model, GLOMAP. We investigate how the responses of PM2.5 and cloud condensation nuclei (CCN) are coupled, and how attempts to improve air quality could have inadvertent effects on CCN, clouds and climate. The parameter perturbations considered are a 5°C increase in global temperature, increased or decreased precursor emissions of anthropogenic SO2, NH3, and NOx, and biogenic monoterpenes, and increased or decreased primary emissions of organic and black carbon aerosols from wildfire, fossil fuel, and biofuel. To quantify the interactions, we define a new sensitivity metric in terms of the response of CCN divided by the response of PM in different regions. .Our results show that the coupled chemistry and aerosol processes cause complex responses that will make any co-benefit policy decision problematic. In particular, we show that reducing SO2 emissions effectively reduces surface-level PM2.5 over continental regions in summer when background PM2.5 is high, with a relatively small reduction in marine CCN (and hence indirect radiative cooling over ocean), which is beneficial for near-term climate. Reducing NOx emissions does not improve summertime air quality very effectively but leads to a relatively high reduction of marine CCN. Reducing NH3 emissions has moderate effects on both PM2.5 and CCN. These three species are strongly coupled chemically and microphysically and the effects of changing emissions of one species on mass and size distributions of aerosols are very complex and spatially and temporally variable. For example, reducing SO2 emissions leads to reductions in sulphate and ammonium mass

  18. Targeted high-resolution ion mobility separation coupled to ultrahigh-resolution mass spectrometry of endocrine disruptors in complex mixtures.

    PubMed

    Benigni, Paolo; Thompson, Christopher J; Ridgeway, Mark E; Park, Melvin A; Fernandez-Lima, Francisco

    2015-04-21

    Traditional separation and detection of targeted compounds from complex mixtures from environmental matrices requires the use of lengthy prefractionation steps and high-resolution mass analyzers due to the large number of chemical components and their large structural diversity (highly isomeric). In the present work, selected accumulation trapped ion mobility spectrometry (SA-TIMS) is coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for direct separation and characterization of targeted endocrine-disrupting compounds (EDC) from a complex environmental matrix in a single analysis. In particular, targeted identification based on high-resolution mobility (R ∼ 70-120) and ultrahigh-resolution mass measurements (R > 400 000) of seven commonly targeted EDC and their isobars (e.g., bisphenol A, (Z)- and (E)-diethylstilbestrol, hexestrol, estrone, α-estradiol, and 17-ethynylestradiol) is shown from a complex mixture of water-soluble organic matter (e.g., Suwannee River Fulvic Acid Standard II) complemented with reference standard measurements and theoretical calculations (<3% error).

  19. Cell division orientation is coupled to cell–cell adhesion by the E-cadherin/LGN complex

    PubMed Central

    Gloerich, Martijn; Bianchini, Julie M.; Siemers, Kathleen A.; Cohen, Daniel J.; Nelson, W. James

    2017-01-01

    Both cell–cell adhesion and oriented cell division play prominent roles in establishing tissue architecture, but it is unclear how they might be coordinated. Here, we demonstrate that the cell–cell adhesion protein E-cadherin functions as an instructive cue for cell division orientation. This is mediated by the evolutionarily conserved LGN/NuMA complex, which regulates cortical attachments of astral spindle microtubules. We show that LGN, which adopts a three-dimensional structure similar to cadherin-bound catenins, binds directly to the E-cadherin cytosolic tail and thereby localizes at cell–cell adhesions. On mitotic entry, NuMA is released from the nucleus and competes LGN from E-cadherin to locally form the LGN/NuMA complex. This mediates the stabilization of cortical associations of astral microtubules at cell–cell adhesions to orient the mitotic spindle. Our results show how E-cadherin instructs the assembly of the LGN/NuMA complex at cell–cell contacts, and define a mechanism that couples cell division orientation to intercellular adhesion. PMID:28045117

  20. Intraflagellar transport-A complex mediates ciliary entry and retrograde trafficking of ciliary G protein–coupled receptors

    PubMed Central

    Hirano, Tomoaki; Katoh, Yohei; Nakayama, Kazuhisa

    2017-01-01

    Cilia serve as cellular antennae where proteins involved in sensory and developmental signaling, including G protein–coupled receptors (GPCRs), are specifically localized. Intraflagellar transport (IFT)-A and -B complexes mediate retrograde and anterograde ciliary protein trafficking, respectively. Using a visible immunoprecipitation assay to detect protein–protein interactions, we show that the IFT-A complex is divided into a core subcomplex, composed of IFT122/IFT140/IFT144, which is associated with TULP3, and a peripheral subcomplex, composed of IFT43/IFT121/IFT139, where IFT139 is most distally located. IFT139-knockout (KO) and IFT144-KO cells demonstrated distinct phenotypes: IFT139-KO cells showed the accumulation of IFT-A, IFT-B, and GPCRs, including Smoothened and GPR161, at the bulged ciliary tips; IFT144-KO cells showed failed ciliary entry of IFT-A and GPCRs and IFT-B accumulation at the bulged tips. These observations demonstrate the distinct roles of the core and peripheral IFT-A subunits: IFT139 is dispensable for IFT-A assembly but essential for retrograde trafficking of IFT-A, IFT-B, and GPCRs; in contrast, IFT144 is essential for functional IFT-A assembly and ciliary entry of GPCRs but dispensable for anterograde IFT-B trafficking. Thus the data presented here demonstrate that the IFT-A complex mediates not only retrograde trafficking but also entry into cilia of GPCRs. PMID:27932497

  1. Smallest eigenvalue density for regular or fixed-trace complex Wishart-Laguerre ensemble and entanglement in coupled kicked tops

    NASA Astrophysics Data System (ADS)

    Kumar, Santosh; Sambasivam, Bharath; Anand, Shashank

    2017-08-01

    The statistical behaviour of the smallest eigenvalue has important implications for systems which can be modeled using a Wishart-Laguerre ensemble, the regular one or the fixed trace one. For example, the density of the smallest eigenvalue of the Wishart-Laguerre ensemble plays a crucial role in characterizing multiple channel telecommunication systems. Similarly, in the quantum entanglement problem, the smallest eigenvalue of the fixed trace ensemble carries information regarding the nature of entanglement. For real Wishart-Laguerre matrices, there exists an elegant recurrence scheme suggested by Edelman to directly obtain the exact expression for the smallest eigenvalue density. In the case of complex Wishart-Laguerre matrices, for finding exact and explicit expressions for the smallest eigenvalue density, existing results based on determinants become impractical when the determinants involve large-size matrices. In this work, we derive a recurrence scheme for the complex case which is analogous to that of Edelman’s for the real case. This is used to obtain exact results for the smallest eigenvalue density for both the regular, and the fixed trace complex Wishart-Laguerre ensembles. We validate our analytical results using Monte Carlo simulations. We also study scaled Wishart-Laguerre ensemble and investigate its efficacy in approximating the fixed-trace ensemble. Eventually, we apply our result for the fixed-trace ensemble to investigate the behaviour of the smallest eigenvalue in the paradigmatic system of coupled kicked tops.

  2. Porphyrin-cobaloxime complexes for hydrogen production, a photo- and electrochemical study, coupled with quantum chemical calculations.

    PubMed

    Manton, Jennifer C; Long, Conor; Vos, Johannes G; Pryce, Mary T

    2014-03-07

    Two porphyrin-cobaloxime complexes; [{Co(dmgH)2Cl}{MPyTPP}] () and [{Co(dmgH)2Cl}{ZnMPyTPP}] () (dmgH = dimethylglyoxime, MPyTPP = 5-(4-pyridyl)-10,15,20-triphenylporphyrin) have been synthesised as model systems for the generation of hydrogen from water. Although initially envisaged as photocatalytic systems neither complex catalysed the reduction of water to hydrogen following irradiation. However, both complexes are molecular precursors for hydrogen evolution under electrochemical conditions. Turnover numbers for hydrogen production of 1.8 × 10(3) and 5.1 × 10(3) were obtained for and respectively following potentiostatic electrolysis at -1.2 V vs. Ag/AgCl while cobaloxime alone produced a turnover-number of 8.0 × 10(3). The photophysical properties of and were examined to provide an explanation for the lack of photochemical activity. These results, coupled with quantum chemical calculations, confirm that porphyrins fail to act as light-harvesting units for these systems and that the lowest energy excited states are in fact cobaloxime-based rather than porphyrin based.

  3. Concerted proton-coupled electron transfer from a metal-hydride complex.

    PubMed

    Bourrez, Marc; Steinmetz, Romain; Ott, Sascha; Gloaguen, Frederic; Hammarström, Leif

    2014-02-01

    Metal hydrides are key intermediates in the catalytic reduction of protons and CO2 as well as in the oxidation of H2. In these reactions, electrons and protons are transferred to or from separate acceptors or donors in bidirectional protoncoupled electron transfer (PCET) steps. The mechanistic interpretation of PCET reactions of metal hydrides has focused on the stepwise transfer of electrons and protons. A concerted transfer may, however, occur with a lower reaction barrier and therefore proceed at higher catalytic rates. Here we investigate the feasibility of such a reaction by studying the oxidation–deprotonation reactions of a tungsten hydride complex. The rate dependence on the driving force for both electron transfer and proton transfer—employing different combinations of oxidants and bases—was used to establish experimentally the concerted, bidirectional PCET of a metal-hydride species. Consideration of the findings presented here in future catalyst designs may lead to more-efficient catalysts.

  4. Complex Process Couplings Related to Deep Geologic Sequestration and Energy Recovery (Invited)

    NASA Astrophysics Data System (ADS)

    Elsworth, D.

    2009-12-01

    Fluids in the shallow crust exert important controls on a wide spectrum of natural and engineered phenomena. The complex interaction of stress and particularly that of chemistry exhibit important feedbacks which influence the evolution of the mechanical and transport properties of rocks. These feedbacks in turn relate crucially to the subsurface recovery of hydrocarbons from the full spectrum of conventional through unconventional reservoirs, to the recovery of hydrothermal and non-hydrothermal geothermal resources, to the secure and enduring sequestration of energy by-products, and to the earthquake cycle, for example. Enigmatic interactions between stress and chemistry in mediating the evolution of permeability and strength in natural and engineered systems are explored - as relevant to high-carbon through low-carbon energy systems. Examples are selected to illustrate the significance of these interactions in controlling the response of hydrocarbon and geothermal reservoirs, fracture treatments, radioactive waste disposal and in the response of faults.

  5. Charge Transfer Between Quantum Dots and Peptide-Coupled Redox Complexes

    DTIC Science & Technology

    2009-01-01

    scale ) Ruthenium complex 190 2009 NRL REVIEW NANOSCIENCE TECHNOLOGY N or m al iz ed C ur re nt (µ A ) Potential, V vs...DHLA QDs Abs 2 Ru /QD Abs 5 Ru /QD FIGURE 4 Enzymatic assay of chymotrypsin activity utilizing QD–Ru peptide conjugates, showing enzymatic ve ...0.01 0.02 0.03 0.04 Vmax = 0.04 +/- 0.02 µM/min KM = 0.83 +/- 0.16 µM KM = 2.2 +/- 0.5 µM Vmax = 0.01 +/- 0.004 µM/min No inhibitor + Chymostatin inhibitor V el oc ity (µ M C hy m -R u cl ea ve d

  6. Nonadiabatic dynamics of photoinduced proton-coupled electron transfer in a solvated phenol-amine complex.

    PubMed

    Goyal, Puja; Schwerdtfeger, Christine A; Soudackov, Alexander V; Hammes-Schiffer, Sharon

    2015-02-12

    Photoinduced concerted electron-proton transfer (EPT), denoted photo-EPT, is important for a wide range of energy conversion processes. Transient absorption and Raman spectroscopy experiments on the hydrogen-bonded p-nitrophenylphenol-t-butylamine complex, solvated in 1,2-dichloroethane, suggested that this complex may undergo photo-EPT. The experiments probed two excited electronic states that were interpreted as an intramolecular charge transfer (ICT) state and an EPT state. Herein mixed quantum mechanical/molecular mechanical nonadiabatic surface hopping dynamics is used to investigate the relaxation pathways following photoexcitation. The potential energy surface is generated on the fly with a semiempirical floating occupation molecular orbital complete active space configuration interaction method for the solute molecule and a molecular mechanical force field for the explicit solvent molecules. The free energy curves along the proton transfer coordinate illustrate that proton transfer is thermodynamically and kinetically favorable on the lower-energy excited state but not on the higher-energy excited state, supporting the characterization of these states as EPT and ICT, respectively. The nonadiabatic dynamics simulations indicate that the population decays from the ICT state to the EPT state in ∼100 fs and from the EPT state to the ground state on the slower time scale of ∼1 ps, qualitatively consistent with the experimental measurements. For ∼54% of the trajectories, the proton transfers from the phenol to the amine in ∼400 fs on the EPT state and then transfers back to the phenol rapidly upon decay to the ground state. Thus, these calculations augment the original interpretation of the experimental data by providing evidence of proton transfer on the EPT state prior to decay to the ground state. The fundamental insights obtained from these simulations are also relevant to other photo-EPT processes.

  7. Coupled dynamics of node and link states in complex networks: a model for language competition

    NASA Astrophysics Data System (ADS)

    Carro, Adrián; Toral, Raúl; San Miguel, Maxi

    2016-11-01

    Inspired by language competition processes, we present a model of coupled evolution of node and link states. In particular, we focus on the interplay between the use of a language and the preference or attitude of the speakers towards it, which we model, respectively, as a property of the interactions between speakers (a link state) and as a property of the speakers themselves (a node state). Furthermore, we restrict our attention to the case of two socially equivalent languages and to socially inspired network topologies based on a mechanism of triadic closure. As opposed to most of the previous literature, where language extinction is an inevitable outcome of the dynamics, we find a broad range of possible asymptotic configurations, which we classify as: frozen extinction states, frozen coexistence states, and dynamically trapped coexistence states. Moreover, metastable coexistence states with very long survival times and displaying a non-trivial dynamics are found to be abundant. Interestingly, a system size scaling analysis shows, on the one hand, that the probability of language extinction vanishes exponentially for increasing system sizes and, on the other hand, that the time scale of survival of the non-trivial dynamical metastable states increases linearly with the size of the system. Thus, non-trivial dynamical coexistence is the only possible outcome for large enough systems. Finally, we show how this coexistence is characterized by one of the languages becoming clearly predominant while the other one becomes increasingly confined to ‘ghetto-like’ structures: small groups of bilingual speakers arranged in triangles, with a strong preference for the minority language, and using it for their intra-group interactions while they switch to the predominant language for communications with the rest of the population.

  8. Structures and magnetic properties of an antiferromagnetically coupled polymeric copper(II) complex and ferromagnetically coupled hexanuclear nickel(II) clusters.

    PubMed

    Tandon, Santokh S; Bunge, Scott D; Sanchiz, Joaquin; Thompson, Laurence K

    2012-03-05

    Reactions between 2,6-diformyl-4-methylphenol (DFMF) and tris(hydroxymethyl) aminomethane (THMAM = H(3)L2) in the presence of copper(II) salts, CuX(2) (X = CH(3)CO(2)(-), BF(4)(-), ClO(4)(-), Cl(-), NO(3)(-)) and Ni(CH(3)CO(2))(2) or Ni(ClO(4))(2)/NaC(6)H(5)CO(2), sodium azide (NaN(3)), and triethylamine (TEA), in one pot self-assemble giving a coordination polymer consisting of repeating pentanuclear copper(II) clusters {[Cu(2)(H(5)L(2-))(μ-N(3))](2)[Cu(N(3))(4)]·2CH(3)OH}(n) (1) and hexanuclear Ni(II) complexes [Ni(6)(H(3)L1(-))(2)(HL2(2-))(2)(μ-N(3))(4)(CH(3)CO(2))(2)]·6C(3)H(7)NO·C(2)H(5)OH (2) and [Ni(6)(H(3)L1(-))(2)(HL2(2-))(2)(μ-N(3))(4)(C(6)H(5)CO(2))(2)]·3C(3)H(7)NO·3H(2)O·CH(3)OH (3). In 1, H(5)L(2-) and in 2 and 3 H(3)L1(-) and HL2(2-) represent doubly deprotonated, singly deprotonated, and doubly deprotonated Schiff-base ligands H(7)L and H(4)L1 and a tripodal ligand H(3)L2, respectively. 1 has a novel double-stranded ladder-like structure in which [Cu(N(3))(4)](2-) anions link single chains comprised of dinuclear cationic subunits [Cu(2)(H(5)L(2-))(μ-N(3))](+), forming a 3D structure of interconnected ladders through H bonding. Nickel(II) clusters 2 and 3 have very similar neutral hexanuclear cores in which six nickel(II) ions are bonded to two H(4)L1, two H(3)L2, four μ-azido, and two μ-CH(3)CO(2)(-)/μ-C(6)H(5)CO(2)(-) ligands. In each structure two terminal dinickel (Ni(2)) units are connected to the central dinickel unit through four doubly bridging end-on (EO) μ-azido and four triply bridging μ(3)-methoxy bridges organizing into hexanuclear units. In each terminal dinuclear unit two nickel centers are bridged through one μ-phenolate oxygen from H(3)L1(-), one μ(3)-methoxy oxygen from HL2(2-), and one μ-CH(3)CO(2)(-) (2)/μ-C(6)H(5)CO(2)(-) (3) ion. Bulk magnetization measurements on 1 show moderately strong antiferromagnetic coupling within the [Cu(2)] building block (J(1) = -113.5 cm(-1)). Bulk magnetization measurements on 2

  9. Ligand-induced dynamics of heterotrimeric G protein-coupled receptor-like kinase complexes

    PubMed Central

    Tunc-Ozdemir, Meral; Jones, Alan M.

    2017-01-01

    Background Arabidopsis, 7-transmembrane Regulator of G signaling protein 1 (AtRGS1) modulates canonical G protein signaling by promoting the inactive state of heterotrimeric G protein complex on the plasma membrane. It is known that plant leucine-rich repeat receptor–like kinases (LRR RLKs) phosphorylate AtRGS1 in vitro but little is known about the in vivo interaction, molecular dynamics, or the cellular consequences of this interaction. Methods Therefore, a subset of the known RLKs that phosphorylate AtRGS1 were selected for elucidation, namely, BAK1, BIR1, FLS2. Several microscopies for both static and dynamic protein-protein interactions were used to follow in vivo interactions between the RLKs and AtRGS1 after the presentation of the Pathogen-associated Molecular Pattern, Flagellin 22 (Flg22). These microscopies included Förster Resonance Energy Transfer, Bimolecular Fluoresence Complementation, and Cross Number and Brightness Fluorescence Correlation Spectroscopy. In addition, reactive oxygen species and calcium changes in living cells were quantitated using luminometry and R-GECO1 microscopy. Results The LRR RLKs BAK1 and BIR1, interact with AtRGS1 at the plasma membrane. The RLK ligand flg22 sets BAK1 in motion toward AtRGS1 and BIR1 away, both returning to the baseline orientations by 10 minutes. The C-terminal tail of AtRGS1 is important for the interaction with BAK1 and for the tempo of the AtRGS1/BIR1 dynamics. This window of time corresponds to the flg22-induced transient production of reactive oxygen species and calcium release which are both attenuated in the rgs1 and the bak1 null mutants. Conclusions A temporal model of these interactions is proposed. flg22 binding induces nearly instantaneous dimerization between FLS2 and BAK1. Phosphorylated BAK1 interacts with and enables AtRGS1 to move away from BIR1 and AtRGS1 becomes phosphorylated leading to its endocytosis thus leading to de-repression by permitting AtGPA1 to exchange GDP for GTP

  10. Ligand-induced dynamics of heterotrimeric G protein-coupled receptor-like kinase complexes

    DOE PAGES

    Tunc-Ozdemir, Meral; Jones, Alan M.

    2017-02-10

    Background Arabidopsis, 7-transmembrane Regulator of G signaling protein 1 (AtRGS1) modulates canonical G protein signaling by promoting the inactive state of heterotrimeric G protein complex on the plasma membrane. It is known that plant leucine-rich repeat receptor-like kinases (LRR RLKs) phosphorylate AtRGS1 in vitro but little is known about the in vivo interaction, molecular dynamics, or the cellular consequences of this interaction. Methods Therefore, a subset of the known RLKs that phosphorylate AtRGS1 were selected for elucidation, namely, BAK1, BIR1, FLS2. Several microscopies for both static and dynamic protein-protein interactions were used to follow in vivo interactions between the RLKsmore » and AtRGS1 after the presentation of the Pathogen-associated Molecular Pattern, Flagellin 22 (Flg22). These microscopies included FoÈrster Resonance Energy Transfer, Bimolecular Fluoresence Complementation, and Cross Number and Brightness fluorescence Correlation Spectroscopy. In addition, reactive oxygen species and calcium changes in living cells were quantitated using luminometry and R-GECO1 microscopy. Results The LRR RLKs BAK1 and BIR1, interact with AtRGS1 at the plasma membrane. The RLK ligand flg22 sets BAK1 in motion toward AtRGS1 and BIR1 away, both returning to the baseline orientations by 10 minutes. The C-terminal tail of AtRGS1 is important for the interaction with BAK1 and for the tempo of the AtRGS1/BIR1 dynamics. This window of time corresponds to the flg22-induced transient production of reactive oxygen species and calcium release which are both attenuated in the rgs1 and the bak1 null mutants. Conclusions A temporal model of these interactions is proposed. flg22 binding induces nearly instantaneous dimerization between FLS2 and BAK1. Phosphorylated BAK1 interacts with and enables AtRGS1 to move away from BIR1 and AtRGS1 becomes phosphorylated leading to its endocytosis thus leading to de-repression by permitting AtGPA1 to exchange GDP for GTP

  11. Performance and evaluation of a coupled prognostic model TAPM over a mountainous complex terrain industrial area

    NASA Astrophysics Data System (ADS)

    Matthaios, Vasileios N.; Triantafyllou, Athanasios G.; Albanis, Triantafyllos A.; Sakkas, Vasileios; Garas, Stelios

    2017-04-01

    Atmospheric modeling is considered an important tool with several applications such as prediction of air pollution levels, air quality management, and environmental impact assessment studies. Therefore, evaluation studies must be continuously made, in order to improve the accuracy and the approaches of the air quality models. In the present work, an attempt is made to examine the air pollution model (TAPM) efficiency in simulating the surface meteorology, as well as the SO2 concentrations in a mountainous complex terrain industrial area. Three configurations under different circumstances, firstly with default datasets, secondly with data assimilation, and thirdly with updated land use, ran in order to investigate the surface meteorology for a 3-year period (2009-2011) and one configuration applied to predict SO2 concentration levels for the year of 2011.The modeled hourly averaged meteorological and SO2 concentration values were statistically compared with those from five monitoring stations across the domain to evaluate the model's performance. Statistical measures showed that the surface temperature and relative humidity are predicted well in all three simulations, with index of agreement (IOA) higher than 0.94 and 0.70 correspondingly, in all monitoring sites, while an overprediction of extreme low temperature values is noted, with mountain altitudes to have an important role. However, the results also showed that the model's performance is related to the configuration regarding the wind. TAPM default dataset predicted better the wind variables in the center of the simulation than in the boundaries, while improvement in the boundary horizontal winds implied the performance of TAPM with updated land use. TAPM assimilation predicted the wind variables fairly good in the whole domain with IOA higher than 0.83 for the wind speed and higher than 0.85 for the horizontal wind components. Finally, the SO2 concentrations were assessed by the model with IOA varied from 0

  12. Influence of weak vibrational-electronic couplings on 2D electronic spectra and inter-site coherence in weakly coupled photosynthetic complexes

    NASA Astrophysics Data System (ADS)

    Monahan, Daniele M.; Whaley-Mayda, Lukas; Ishizaki, Akihito; Fleming, Graham R.

    2015-08-01

    Coherence oscillations measured in two-dimensional (2D) electronic spectra of pigment-protein complexes may have electronic, vibrational, or mixed-character vibronic origins, which depend on the degree of electronic-vibrational mixing. Oscillations from intrapigment vibrations can obscure the inter-site coherence lifetime of interest in elucidating the mechanisms of energy transfer in photosynthetic light-harvesting. Huang-Rhys factors (S) for low-frequency vibrations in Chlorophyll and Bacteriochlorophyll are quite small (S ≤ 0.05), so it is often assumed that these vibrations influence neither 2D spectra nor inter-site coherence dynamics. In this work, we explore the influence of S within this range on the oscillatory signatures in simulated 2D spectra of a pigment heterodimer. To visualize the inter-site coherence dynamics underlying the 2D spectra, we introduce a formalism which we call the "site-probe response." By comparing the calculated 2D spectra with the site-probe response, we show that an on-resonance vibration with Huang-Rhys factor as small as S = 0.005 and the most strongly coupled off-resonance vibrations (S = 0.05) give rise to long-lived, purely vibrational coherences at 77 K. We moreover calculate the correlation between optical pump interactions and subsequent entanglement between sites, as measured by the concurrence. At 77 K, greater long-lived inter-site coherence and entanglement appear with increasing S. This dependence all but vanishes at physiological temperature, as environmentally induced fluctuations destroy the vibronic mixing.

  13. Influence of weak vibrational-electronic couplings on 2D electronic spectra and inter-site coherence in weakly coupled photosynthetic complexes

    SciTech Connect

    Monahan, Daniele M.; Whaley-Mayda, Lukas; Fleming, Graham R.; Ishizaki, Akihito

    2015-08-14

    Coherence oscillations measured in two-dimensional (2D) electronic spectra of pigment-protein complexes may have electronic, vibrational, or mixed-character vibronic origins, which depend on the degree of electronic-vibrational mixing. Oscillations from intrapigment vibrations can obscure the inter-site coherence lifetime of interest in elucidating the mechanisms of energy transfer in photosynthetic light-harvesting. Huang-Rhys factors (S) for low-frequency vibrations in Chlorophyll and Bacteriochlorophyll are quite small (S ≤ 0.05), so it is often assumed that these vibrations influence neither 2D spectra nor inter-site coherence dynamics. In this work, we explore the influence of S within this range on the oscillatory signatures in simulated 2D spectra of a pigment heterodimer. To visualize the inter-site coherence dynamics underlying the 2D spectra, we introduce a formalism which we call the “site-probe response.” By comparing the calculated 2D spectra with the site-probe response, we show that an on-resonance vibration with Huang-Rhys factor as small as S = 0.005 and the most strongly coupled off-resonance vibrations (S = 0.05) give rise to long-lived, purely vibrational coherences at 77 K. We moreover calculate the correlation between optical pump interactions and subsequent entanglement between sites, as measured by the concurrence. At 77 K, greater long-lived inter-site coherence and entanglement appear with increasing S. This dependence all but vanishes at physiological temperature, as environmentally induced fluctuations destroy the vibronic mixing.

  14. PREVENTION project the complex geophysical observatory in Mexico as a test facility for lithosphere-atmosphere-ionosphere coupling models

    NASA Astrophysics Data System (ADS)

    Pulinets, S.; Leyva Contreras, A.; Kostoglodov, V.; Perez de Tejada, H.; Urrutia Fucugauchi, H.

    2003-04-01

    The recent few years flourished in different physical models trying to explain the physical mechanisms of electromagnetic and plasma phenomena observed in the area of anticipated earthquake on the ground level, in atmosphere and ionosphere. No one of the presented models avoids the use of hypothesis because of lack of the experimental data. At least, the models use the data collected in different places, in different time, for different earthquakes. The project PREVENTION (PREcursores de Vulcano Erupciones y Notable Temblores. Integral Observatorio Nacional) intends to establish the complex geophysical observatory in one of the most seismically active areas of Mexico state of Guerrero including measurements on all levels from underground to space to have the dataset of simultaneous multiparameter measurements for direct check of existing physical models of seismo-ionospheric coupling. The second site of experimental survey will be organized in the vicinity of Popacatepetl volcano to study the precursors of volcano eruption. The observatory conception will be described.

  15. Modified function projective synchronization between two different complex networks with delayed couplings and delayed nodes of different dimensions

    NASA Astrophysics Data System (ADS)

    Han, Min; Zhang, Yamei; Zhang, Meng

    2016-05-01

    In this paper, to deal with the problem of modified function projective synchronization (MFPS) between two different networks with delayed couplings and delayed nodes of different dimensions, a hybrid control scheme combining adaptive control and nonlinear control is proposed. First, a more realistic drive-response complex network model is constructed by introducing double delays. Then, we design hybrid feedback controllers to synchronize up the drive and response networks of different dimensions to a scaling function matrix. Based on Lyapunov stability theory and the linear matrix inequality (LMI), we rigorously prove that the MFPS between the proposed drive-response networks can be achieved and meanwhile some sufficient conditions are derived by adopting an appropriate Lyapunov-Krasovskii energy function. Noteably, many existing synchronization settings can be regarded as special cases of the present synchronization framework. Numerical simulation experiments are employed to verify the correctness and the effectiveness of the proposed method.

  16. Divergent Coupling of Alcohols and Amines Catalyzed by Isoelectronic Hydride Mn(I) and Fe(II) PNP Pincer Complexes.

    PubMed

    Mastalir, Matthias; Glatz, Mathias; Gorgas, Nikolaus; Stöger, Berthold; Pittenauer, Ernst; Allmaier, Günter; Veiros, Luis F; Kirchner, Karl

    2016-08-22

    Herein, we describe an efficient coupling of alcohols and amines catalyzed by well-defined isoelectronic hydride Mn(I) and Fe(II) complexes, which are stabilized by a PNP ligand based on the 2,6-diaminopyridine scaffold. This reaction is an environmentally benign process implementing inexpensive, earth-abundant non-precious metal catalysts, and is based on the acceptorless alcohol dehydrogenation concept. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted in good to excellent isolated yields. Although in the case of Mn selectively imines were obtained, with Fe-exclusively monoalkylated amines were formed. These reactions proceed under base-free conditions and required the addition of molecular sieves.

  17. Homology modeling of the CheW coupling protein of the chemotaxis signaling complex.

    PubMed

    Cashman, Derek J; Ortega, Davi R; Zhulin, Igor B; Baudry, Jerome

    2013-01-01

    Homology models of the E. coli and T. maritima chemotaxis protein CheW were constructed to assess the quality of structural predictions and their applicability in chemotaxis research: i) a model of E. coli CheW was constructed using the T. maritima CheW NMR structure as a template, and ii) a model of T. maritima CheW was constructed using the E. coli CheW NMR structure as a template. The conformational space accessible to the homology models and to the NMR structures was investigated using molecular dynamics and Monte Carlo simulations. The results show that even though static homology models of CheW may be partially structurally different from their corresponding experimentally determined structures, the conformational space they can access through their dynamic variations can be similar, for specific regions of the protein, to that of the experimental NMR structures. When CheW homology models are allowed to explore their local accessible conformational space, modeling can provide a rational path to predicting CheW interactions with the MCP and CheA proteins of the chemotaxis complex. Homology models of CheW (and potentially, of other chemotaxis proteins) should be seen as snapshots of an otherwise larger ensemble of accessible conformational space.

  18. Homology Modeling of the CheW Coupling Protein of the Chemotaxis Signaling Complex

    PubMed Central

    Cashman, Derek J.; Ortega, Davi R.; Zhulin, Igor B.; Baudry, Jerome

    2013-01-01

    Homology models of the E. coli and T. maritima chemotaxis protein CheW were constructed to assess the quality of structural predictions and their applicability in chemotaxis research: i) a model of E. coli CheW was constructed using the T. maritima CheW NMR structure as a template, and ii) a model of T. maritima CheW was constructed using the E. coli CheW NMR structure as a template. The conformational space accessible to the homology models and to the NMR structures was investigated using molecular dynamics and Monte Carlo simulations. The results show that even though static homology models of CheW may be partially structurally different from their corresponding experimentally determined structures, the conformational space they can access through their dynamic variations can be similar, for specific regions of the protein, to that of the experimental NMR structures. When CheW homology models are allowed to explore their local accessible conformational space, modeling can provide a rational path to predicting CheW interactions with the MCP and CheA proteins of the chemotaxis complex. Homology models of CheW (and potentially, of other chemotaxis proteins) should be seen as snapshots of an otherwise larger ensemble of accessible conformational space. PMID:23950985

  19. Dynamics of Complex Systems Built as Coupled Physical, Communication and Decision Layers.

    PubMed

    Kühnlenz, Florian; Nardelli, Pedro H J

    2016-01-01

    This paper proposes a simple model to capture the complexity of multilayer systems where their constituent layers affect, and are affected by, each other. The physical layer is a circuit composed by a power source and resistors in parallel. Every individual agent aims at maximizing its own delivered power by adding, removing or keeping the resistors it has; the delivered power is in turn a non-linear function that depends on the other agents' behavior, its own internal state, its global state perception, the information received from its neighbors via the communication network and a randomized selfishness. We develop an agent-based simulation to analyze the effects of number of agents (system size), communication network topology, communication errors and the minimum power gain that triggers a behavioral change on the system dynamic. Our results show that a wave-like behavior at macro-level (caused by individual changes in the decision layer) can only emerge for a specific system size. The ratio between cooperators and defectors depends on the minimum gain assumed-lower minimal gains lead to less cooperation, and vice-versa. Different communication network topologies imply different levels of power utilization and fairness at the physical layer, and a certain level of error in the communication layer induces more cooperation.

  20. Evolution of protein-coupled RNA dynamics during hierarchical assembly of ribosomal complexes.

    PubMed

    Abeysirigunawardena, Sanjaya C; Kim, Hajin; Lai, Jonathan; Ragunathan, Kaushik; Rappé, Mollie C; Luthey-Schulten, Zaida; Ha, Taekjip; Woodson, Sarah A

    2017-09-08

    Assembly of 30S ribosomes involves the hierarchical addition of ribosomal proteins that progressively stabilize the folded 16S rRNA. Here, we use three-color single molecule FRET to show how combinations of ribosomal proteins uS4, uS17 and bS20 in the 16S 5' domain enable the recruitment of protein bS16, the next protein to join the complex. Analysis of real-time bS16 binding events shows that bS16 binds both native and non-native forms of the rRNA. The native rRNA conformation is increasingly favored after bS16 binds, explaining how bS16 drives later steps of 30S assembly. Chemical footprinting and molecular dynamics simulations show that each ribosomal protein switches the 16S conformation and dampens fluctuations at the interface between rRNA subdomains where bS16 binds. The results suggest that specific protein-induced changes in the rRNA dynamics underlie the hierarchy of 30S assembly and simplify the search for the native ribosome structure.Ribosomes assemble through the hierarchical addition of proteins to a ribosomal RNA scaffold. Here the authors use three-color single-molecule FRET to show how the dynamics of the rRNA dictate the order in which multiple proteins assemble on the 5' domain of the E. coli 16S rRNA.

  1. Dynamics of Complex Systems Built as Coupled Physical, Communication and Decision Layers

    PubMed Central

    Kühnlenz, Florian; Nardelli, Pedro H. J.

    2016-01-01

    This paper proposes a simple model to capture the complexity of multilayer systems where their constituent layers affect, and are affected by, each other. The physical layer is a circuit composed by a power source and resistors in parallel. Every individual agent aims at maximizing its own delivered power by adding, removing or keeping the resistors it has; the delivered power is in turn a non-linear function that depends on the other agents’ behavior, its own internal state, its global state perception, the information received from its neighbors via the communication network and a randomized selfishness. We develop an agent-based simulation to analyze the effects of number of agents (system size), communication network topology, communication errors and the minimum power gain that triggers a behavioral change on the system dynamic. Our results show that a wave-like behavior at macro-level (caused by individual changes in the decision layer) can only emerge for a specific system size. The ratio between cooperators and defectors depends on the minimum gain assumed—lower minimal gains lead to less cooperation, and vice-versa. Different communication network topologies imply different levels of power utilization and fairness at the physical layer, and a certain level of error in the communication layer induces more cooperation. PMID:26730590

  2. Increasing Model Complexity: Unit Testing and Validation of a Coupled Electrical Resistive Heating and Macroscopic Invasion Percolation Model

    NASA Astrophysics Data System (ADS)

    Molnar, I. L.; Krol, M.; Mumford, K. G.

    2016-12-01

    Geoenvironmental models are becoming increasingly sophisticated as they incorporate rising numbers of mechanisms and process couplings to describe environmental scenarios. When combined with advances in computing and numerical techniques, these already complicated models are experiencing large increases in code complexity and simulation time. Although, this complexity has enabled breakthroughs in the ability to describe environmental problems, it is difficult to ensure that complex models are sufficiently robust and behave as intended. Many development tools used for testing software robustness have not seen widespread use in geoenvironmental sciences despite an increasing reliance on complex numerical models, leaving many models at risk of undiscovered errors and potentially improper validations. This study explores the use of unit testing, which independently examines small code elements to ensure each unit is working as intended as well as their integrated behaviour, to test the functionality and robustness of a coupled Electrical Resistive Heating (ERH) - Macroscopic Invasion Percolation (MIP) model. ERH is a thermal remediation technique where the soil is heated until boiling and volatile contaminants are stripped from the soil. There is significant interest in improving the efficiency of ERH, including taking advantage of low-temperature co-boiling behaviour which may reduce energy consumption. However, at lower co-boiling temperatures gas bubbles can form, mobilize and collapse in cooler areas, potentially contaminating previously clean zones. The ERH-MIP model was created to simulate the behaviour of gas bubbles in the subsurface and to evaluate ERH during co-boiling1. This study demonstrates how unit testing ensures that the model behaves in an expected manner and examines the robustness of every component within the ERH-MIP model. Once unit testing is established, the MIP module (a discrete gas transport algorithm for gas expansion, mobilization and

  3. Design of a Binuclear Ni(II) Complex with Large Ising-type Anisotropy and Weak Anti-Ferromagnetic Coupling.

    PubMed

    El-Khatib, Fatima; Cahier, Benjamin; López-Jordà, Maurici; Guillot, Régis; Rivière, Eric; Hafez, Hala; Saad, Zeinab; Girerd, Jean-Jacques; Guihéry, Nathalie; Mallah, Talal

    2017-09-05

    The preparation of a binuclear Ni(II) complex with a pentacoordinate environment using a cryptand organic ligand and the imidazolate bridge is reported. The coordination sphere is close to trigonal bipyramidal (tbp) for one Ni(II) and to square pyramidal (spy) for the other. The use of the imidazolate bridge that undergoes π-π stacking with two benzene rings of the chelating ligand induces steric hindrance that stabilizes the pentacoordinate environment. Magnetic measurements together with theoretical studies of the spin states energy levels allow fitting the data and reveal a large Ising-type anisotropy and a weak anti-ferromagnetic exchange coupling between the metal ions. The magnitude and the nature of the magnetic anisotropy and the difference in anisotropy between the two metal ions are rationalized using wave-function-based calculations. We show that a slight distortion of the coordination sphere of Ni(II) from spy to tbp leads to an Ising-type anisotropy. Broken-symmetry density functional calculations rationalize the weak anti-ferromagnetic exchange coupling through the imidazolate bridge.

  4. Coupling nutrient sensing to metabolic homoeostasis: the role of the mammalian target of rapamycin complex 1 pathway.

    PubMed

    André, Caroline; Cota, Daniela

    2012-11-01

    The mammalian target of rapamycin complex 1 (mTORC1) pathway is known to couple different environmental cues to the regulation of several energy-demanding functions within the cell, spanning from protein translation to mitochondrial activity. As a result, at the organism level, mTORC1 activity affects energy balance and general metabolic homoeostasis by modulating both the activity of neuronal populations that play key roles in the control of food intake and body weight, as well as by determining storage and use of fuel substrates in peripheral tissues. This review focuses on recent advances made in understanding the role of the mTORC1 pathway in the regulation of energy balance. More particularly, it aims at providing an overview of the status of knowledge regarding the mechanisms underlying the ability of certain amino acids, glucose and fatty acids, to affect mTORC1 activity and in turn illustrates how the mTORC1 pathway couples nutrient sensing to the hypothalamic regulation of the organisms' energy homoeostasis and to the control of intracellular metabolic processes, such as glucose uptake, protein and lipid biosynthesis. The evidence reviewed pinpoints the mTORC1 pathway as an integrator of the actions of nutrients on metabolic health and provides insight into the relevance of this intracellular pathway as a potential target for the therapy of metabolic diseases such as obesity and type-2 diabetes.

  5. Intermediate-coupling scheme for many-electron systems of the complexes of the transition-metal ions

    NASA Astrophysics Data System (ADS)

    Basu, S.; Chakravarty, A. S.

    1982-10-01

    The generalized theory of the intermediate-coupling scheme has been developed for the many-electron systems of the second and third series of the transition-metal-ion octahedral complexes. The theory has been developed for the general configuration, kdn (k=3, 4, 5 n=2, ..., 9) but has been presented up to n=5. The transformation matrices for the remaining d10-n(n<5) configurations can be easily found from those of dn(n<5) by using the well-known principle of electron-hole complimentarity. To show the enormous simplicity and great advantage over the strong-field coupling scheme so long used in such cases, the d3 configuration has been treated by this method as an application. At the end some typical magnitudes of the parameters like Dq, ζ, B, and C have been used to find the energy levels and the paramagnetic susceptibility for K2ReCl6. The beauty and importance of this scheme lies in the fact that as one switches off the spin-orbit interaction one gets results identical with those of Tanabe and Sugano, and further, if one also switches off the crystal field but retains only the interelectronic repulsion term one gets the results coinciding with those of Racah in atomic spectroscopy.

  6. Resting State and Elementary Steps of the Coupling of Aryl Halides with Thiols Catalyzed by Alkylbisphosphine Complexes of Palladium

    PubMed Central

    Alvaro, Elsa

    2010-01-01

    Detailed mechanistic studies on the coupling of aryl halides with thiols catalyzed by palladium complexes of the alkylbisphosphine ligand CyPF-tBu (1-dicyclohexylphosphino-2-di-tert-butylphosphinoethylferrocene) are reported. The elementary steps that constitute the catalytic cycle, i.e. oxidative addition, transmetalation and reductive elimination, have been studied, and their relative rates are reported. Each of the steps of the catalytic process occurs at temperatures that are much lower than those required for the reactions catalyzed by a combination of palladium precursors and CyPF-tBu. To explain these differences in rates between the catalytic and stoichiometric reactions, studies were conducted to identify the resting state of the catalyst of the reactions catalyzed by a combination of Pd(OAc)2 and CyPF-tBu, a combination of Pd(dba)2 and CyPF-tBu, or the likely intermediate Pd(CyPF-tBu)(Ar)(Br). These show that the major palladium complex in each case lies off of the catalytic cycle. The resting state of the reactions catalyzed by Pd(OAc)2 and CyPF-tBu was the palladium bis-thiolate complex [Pd(CyPF-tBu)(SR)2] (R = alkyl or aryl). The resting state in reactions catalyzed by Pd2(dba)3 and CyPF-tBu was the binuclear complex [Pd(CyPF-tBu)]2(μ2, η2-dba) (9). The resting state of reactions of both aromatic and aliphatic thiols catalyzed by [Pd(CyPF-tBu)(p-tolyl)(Br)] (3a) was the hydridopalladium thiolate complex [Pd(CyPF-tBu)(H)(SR)] (R= alkyl and aryl). All these palladium species have been prepared independently, and the mechanisms by which they enter the catalytic cycle have been examined in detail. These features of the reaction catalyzed by palladium and CyPF-tBu have been compared with those of reactions catalyzed by the alkylbisphosphine DiPPF and Pd(OAc)2 or Pd(dba)2. Our data indicate that the resting states of these reactions are similar to each other and that our mechanistic conclusions about reactions catalyzed by palladium and CyPF-tBu can be

  7. Advances in protein complex analysis by chemical cross-linking coupled with mass spectrometry (CXMS) and bioinformatics.

    PubMed

    Tran, Bao Quoc; Goodlett, David R; Goo, Young Ah

    2016-01-01

    For the analysis of protein-protein interactions and protein conformations, cross-linking coupled with mass spectrometry (CXMS) has become an essential tool in recent years. A variety of cross-linking reagents are used to covalently link interacting amino acids to identify protein-binding partners. The spatial proximity of cross-linked amino acid residues is used to elucidate structural models of protein complexes. The main challenges for mapping protein-protein interaction are low stoichiometry and low frequency of cross-linked peptides relative to unmodified linear peptides as well as accurate and efficient matches to corresponding peptide sequences with low false discovery rates for identifying the site of cross-link. We evaluate the current state of chemical cross-linking and mass spectrometry applications with the special emphasis on the recent development of informatics data processing and analysis tools that help complexity of interpreting CXMS data. This article is part of a Special Issue entitled:Physiological Enzymology and Protein Functions. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Serum Response Factor-GATA Ternary Complex Required for Nuclear Signaling by a G-Protein-Coupled Receptor

    PubMed Central

    Morin, Steves; Paradis, Pierre; Aries, Anne; Nemer, Mona

    2001-01-01

    Endothelins are a family of biologically active peptides that are critical for development and function of neural crest-derived and cardiovascular cells. These effects are mediated by two G-protein-coupled receptors and involve transcriptional regulation of growth-responsive and/or tissue-specific genes. We have used the cardiac ANF promoter, which represents the best-studied tissue-specific endothelin target, to elucidate the nuclear pathways responsible for the transcriptional effects of endothelins. We found that cardiac-specific response to endothelin 1 (ET-1) requires the combined action of the serum response factor (SRF) and the tissue-restricted GATA proteins which bind over their adjacent sites, within a 30-bp ET-1 response element. We show that SRF and GATA proteins form a novel ternary complex reminiscent of the well-characterized SRF-ternary complex factor interaction required for transcriptional induction of c-fos in response to growth factors. In transient cotransfections, GATA factors and SRF synergistically activate atrial natriuretic factor and other ET-1-inducible promoters that contain both GATA and SRF binding sites. Thus, GATA factors may represent a new class of tissue-specific SRF accessory factors that account for muscle- and other cell-specific SRF actions. PMID:11158291

  9. Two-tiered coupling between flowing actin and immobilized N-cadherin/catenin complexes in neuronal growth cones

    PubMed Central

    Garcia, Mikael; Leduc, Cécile; Lagardère, Matthieu; Argento, Amélie; Sibarita, Jean-Baptiste; Thoumine, Olivier

    2015-01-01

    Neuronal growth cones move forward by dynamically connecting actin-based motility to substrate adhesion, but the mechanisms at the individual molecular level remain unclear. We cultured primary neurons on N-cadherin–coated micropatterned substrates, and imaged adhesion and cytoskeletal proteins at the ventral surface of growth cones using single particle tracking combined to photoactivated localization microscopy (sptPALM). We demonstrate transient interactions in the second time scale between flowing actin filaments and immobilized N-cadherin/catenin complexes, translating into a local reduction of the actin retrograde flow. Normal actin flow on micropatterns was rescued by expression of a dominant negative N-cadherin construct competing for the coupling between actin and endogenous N-cadherin. Fluorescence recovery after photobleaching (FRAP) experiments confirmed the differential kinetics of actin and N-cadherin, and further revealed a 20% actin population confined at N-cadherin micropatterns, contributing to local actin accumulation. Computer simulations with relevant kinetic parameters modeled N-cadherin and actin turnover well, validating this mechanism. Such a combination of short- and long-lived interactions between the motile actin network and spatially restricted adhesive complexes represents a two-tiered clutch mechanism likely to sustain dynamic environment sensing and provide the force necessary for growth cone migration. PMID:26038554

  10. Complexation of europium and uranium by humic acids analyzed by capillary electrophoresis-inductively coupled plasma mass spectrometry.

    PubMed

    Möser, Christina; Kautenburger, Ralf; Philipp Beck, Horst

    2012-05-01

    Investigations of the mobility of radioactive and nonradioactive substances in the environment are important tasks for the development of a future disposal in deep geological formations. Dissolved organic matter (DOM) can play an important role in the mobilization of metal ions due to complexation. In this study, we investigate the complexation behavior of humic acid (HA) as a model substance for DOM and its influence on the migration of europium as homologue for the actinide americium and uranium as the principal component of nuclear fuel. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For the study, 0.5 mg·L⁻¹ of the metals and 25 mg·L⁻¹ of (purified Aldrich) HA and an aqueous solution sodium-perchlorate with an ionic strength of 10 mM at pH 5 were used. CE-ICP-MS clearly shows the different speciation of the triple positively charged europium and the double positively charged uranyl cation with HA. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Coupled snow dynamics, soil moisture, and soil temperatures in complex terrain of a semi-arid mountainous watershed

    NASA Astrophysics Data System (ADS)

    Bryden, S.; Link, T. E.; Seyfried, M. S.; McNamara, J. P.

    2011-12-01

    Mid-elevation regions characterized by transient or relatively brief seasonal snow covers are likely to experience large hydrologic impacts from warming trends as these regions transition from snow to rain-dominated precipitation in winter. These regions in the western United States are often comprised of complex terrain, including a range of slopes, aspects, elevation, vegetation, geology, and soils over multiple scales. How snow dynamics (e.g. distribution and timing) are coupled with soil moisture and soil temperature in complex terrain is a topic that needs to be explored in order to better understand how climate variations and trends will alter the hydrologic states and fluxes in these mid-elevation transition zones. To address this question, automated hydrometeorological stations were installed in Johnston Draw, a subbasin of the Reynolds Creek Experimental Watershed in southwestern Idaho. In addition to long-term precipitation records for the area, individual meteorological stations were installed on opposing north and south-facing slopes in the drainage at 50 meter elevation intervals, from 1550 to 1750 m amsl. Each station provides air temperature and vapor pressure, wind speed and direction, snow depth, and a profile of soil moisture and temperature at 5cm, 20cm, 35cm, and 50 cm depths, with some profiles extending to approximately 2 m where soils are deepest. Prior to a major mid-winter melt event in January 2011 snow depths averaged 45 cm on north-facing slopes and only 3 cm on south-facing slopes. Soil moisture was depleted near the surface and soil temperatures were just above freezing at all elevations and aspects. In mid-January, air temperatures rapidly increased from below freezing to daily averages from 3-6 °C for six consecutive days, coupled with very high wind speeds, and followed by a pulse of increased streamflow. This event completely ablated the snowpack on south-facing slopes and reduced the snowpack depth on north-facing slopes by 24 cm

  12. Ferromagnetic coupling and magnetic anisotropy in oxalato-bridged trinuclear chromium(III)-cobalt(II) complexes with aromatic diimine ligands.

    PubMed

    Vallejo, Julia; Castro, Isabel; Cañadillas-Delgado, Laura; Ruiz-Pérez, Catalina; Ferrando-Soria, Jesús; Ruiz-García, Rafael; Cano, Joan; Lloret, Francesc; Julve, Miguel

    2010-03-07

    Two novel heterotrinuclear chromium(III)-cobalt(II) complexes of formula {[Cr(III)(bpy)(ox)(2)](2)Co(II)(Me(2)bpy)}.2H(2)O (1) and {[Cr(III)(phen)(ox)(2)](2)Co(II)(Me(2)bpy)}.1.5H(2)O (2) [ox = oxalato, bpy = 2,2'-bipyridine, Me(2)bpy = 6,6'-dimethyl-2,2'-bipyridine, and phen = 1,10-phenanthroline] have been synthesized using the "complex-as-ligand/complex-as-metal" strategy. The X-ray crystal structure of 2 consists of neutral oxalato-bridged Cr(III)(2)Co(II) bent entities formed by the coordination of two anionic [Cr(III)(phen)(ox)(2)](-) complexes through one of their oxalato groups toward a cationic cis-[Co(II)(Me(2)bpy)](2+) complex. The three tris(chelated), six-coordinated metal atoms possess alternating propeller chiralities leading thus to a racemic mixture of heterochiral (Lambda,Delta,Lambda)- and (Delta,Lambda,Delta)-Cr(III)Co(II)Cr(III) triads, whereby the two peripheral chromium(III) ions adopt a trigonal distorted trapezoidal bipyramidal geometry and the central high-spin cobalt(II) ion exhibits a compressed rectangular bipyramidal one. The intermolecular pi-pi stacking interactions between the enantiomeric pairs of heterochiral Cr(III)(2)Co(II) entities through the aromatic diimine terminal ligands lead to a unique two-dimensional supramolecular network. Variable temperature (2.0-300 K) magnetic susceptibility and variable-field (0-5.0 T) magnetization measurements for 1 and 2 reveal the presence of weak but non-negligible intermolecular antiferromagnetic interactions [zj = -0.012 (2a) and -0.08 cm(-1) (2b)] between the Cr(III)(2)Co(II) molecules possessing a moderately anisotropic S = 9/2 ground state. This results from the moderately weak intramolecular ferromagnetic coupling [J = +2.43 (1) and +2.34 cm(-1) (2)] between the two peripheral Cr(III) (S(Cr) = 3/2) and the central high-spin Co(II) (S(Co) = 3/2) ions across the oxalato bridge as well as the appreciable single-ion axial magnetic anisotropy of the central high-spin Co(II) (S(Co) = 3

  13. Hypoxia-Responsive Cobalt Complexes in Tumor Spheroids: Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Magnetic Resonance Imaging Studies.

    PubMed

    O'Neill, Edward S; Kaur, Amandeep; Bishop, David P; Shishmarev, Dmitry; Kuchel, Philip W; Grieve, Stuart M; Figtree, Gemma A; Renfrew, Anna K; Bonnitcha, Paul D; New, Elizabeth J

    2017-08-21

    Dense tumors are resistant to conventional chemotherapies due to the unique tumor microenvironment characterized by hypoxic regions that promote cellular dormancy. Bioreductive drugs that are activated in response to this hypoxic environment are an attractive strategy for therapy with anticipated lower harmful side effects in normoxic healthy tissue. Cobalt bioreductive pro-drugs that selectively release toxic payloads upon reduction in hypoxic cells have shown great promise as anticancer agents. However, the bioreductive response in the tumor microenvironment must be better understood, as current techniques for monitoring bioreduction to Co(II) such as X-ray absorption near-edge structure and extended X-ray absorption fine structure provide limited information on speciation and require synchrotron radiation sources. Here, we present magnetic resonance imaging (MRI) as an accessible and powerful technique to monitor bioreduction by treating the cobalt complex as an MRI contrast agent and monitoring the change in water signal induced by reduction from diamagnetic Co(III) to paramagnetic Co(II). Cobalt pro-drugs built upon the tris(2-pyridylmethyl)amine ligand scaffold with varying charge were investigated for distribution and activity in a 3D tumor spheroid model by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and MRI. In addition, paramagnetic (1)H NMR spectroscopy of spheroids enabled determination of the speciation of activated Co(II)TPAx complexes. This study demonstrates the utility of MRI and associated spectroscopy techniques for understanding bioreductive cobalt pro-drugs in the tumor microenvironment and has broader implications for monitoring paramagnetic metal-based therapies.

  14. Intramolecular cyclization of a diruthenium complex: insight into the mechanism of heteroatom-directed intramolecular C-H/olefin coupling reactions.

    PubMed

    Gong, Dawei; Hu, Bowen; Shi, Jing; Chen, Dafa

    2015-07-28

    Complex 2, synthesized by the reaction of {(C5H4N)(μ2-η(5):η(1)-C9H5)}Ru3(CO)9 (1) with 1,5-hexadiene, could further transform to another diruthenium complex 3via intramolecular carbometalation. The results are relevant to the mechanism of transition-metal catalyzed heteroatom-directed intramolecular C-H/olefin coupling reactions.

  15. Mode-coupling theory and polynomial fitting functions: a complex-plane representation of dielectric data on polymers.

    PubMed

    Eliasson, H

    2001-07-01

    Recently, it has been shown that the higher-order A3 and A4 scenarios of the mode-coupling theory (MCT) are in many cases capable of providing a good description of the complicated dielectric spectra often encountered in polymeric systems. In this paper, more data from dielectric measurements on poly(ethylene terephthalate), poly(vinylidene fluoride), Nylon-66, poly(chlorotrifluoroethylene) (PCTFE), and the polymer gel system poly(acrylonitrile)-ethylene carbonate-propylene carbonate are evaluated within the A4 scenario of the MCT. For all these systems, very good agreement is found between the theoretical and experimental spectra. The data analysis is demonstrated to be facilitated considerably by plotting the data in the complex plane whereby the elliptic functions derived from the theory for the frequency-dependent dielectric function can be replaced by polynomials. For PCTFE, the scaling behavior predicted by the MCT could be verified and the temperature dependences of the extracted scaling parameters were found to be consistent with theory.

  16. Prevention project: a complex geophysical observatory in Mexico as a test facility for lithosphere atmosphere ionosphere coupling models

    NASA Astrophysics Data System (ADS)

    Pulinets, S. A.; Leyva Contreras, A.; Kostoglodov, V.; Perez de Tejada, H.; Urrutia-Fucugauchi, J.

    During the recent few years different physical models were developed trying to explain the physical mechanisms of electromagnetic and plasma phenomena observed in the area of anticipated earthquake on different levels: near the ground, in the atmosphere and in the ionosphere. All existing models are based on certain hypothesis because of lack of sufficient experimental data. In the best case, the models had to use the data collected at different places, and in different time, for different earthquakes. The project PREVENTION (PREcursors of Volcano Eruptions and Notable Tremors Integral ObservatioN) intends to establish a complex geophysical observatory in one of the most seismically active and potentially dangerous areas of Mexico - the State of Guerrero. The measurements will be done on all levels from the underground to the space to obtain simultaneous multi-parameter data for direct examination of existing physical models of seismo-ionospheric coupling. The second site of experimental survey will be established in the vicinity of Popocatepetl volcano to study the relation between volcanic activity and the ionospheric effects. The concept of the observatory is presented.

  17. Quasilongitudinal soliton in a two-dimensional strongly coupled complex dusty plasma in the presence of an external magnetic field.

    PubMed

    Ghosh, Samiran

    2014-09-01

    The propagation of a nonlinear low-frequency mode in two-dimensional (2D) monolayer hexagonal dusty plasma crystal in presence of external magnetic field and dust-neutral collision is investigated. The standard perturbative approach leads to a 2D Korteweg-de Vries (KdV) soliton for the well-known dust-lattice mode. However, the Coriolis force due to crystal rotation and Lorentz force due to magnetic field on dust particles introduce a linear forcing term, whereas dust-neutral drag introduce the usual damping term in the 2D KdV equation. This new nonlinear equation is solved both analytically and numerically to show the competition between the linear forcing and damping in the formation of quasilongitudinal soliton in a 2D strongly coupled complex (dusty) plasma. Numerical simulation on the basis of the typical experimental plasma parameters and the analytical solution reveal that the neutral drag force is responsible for the usual exponential decay of the soliton, whereas Coriolis and/or Lorentz force is responsible for the algebraic decay as well as the oscillating tail formation of the soliton. The results are discussed in the context of the plasma crystal experiment.

  18. Quasilongitudinal soliton in a two-dimensional strongly coupled complex dusty plasma in the presence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Ghosh, Samiran

    2014-09-01

    The propagation of a nonlinear low-frequency mode in two-dimensional (2D) monolayer hexagonal dusty plasma crystal in presence of external magnetic field and dust-neutral collision is investigated. The standard perturbative approach leads to a 2D Korteweg-de Vries (KdV) soliton for the well-known dust-lattice mode. However, the Coriolis force due to crystal rotation and Lorentz force due to magnetic field on dust particles introduce a linear forcing term, whereas dust-neutral drag introduce the usual damping term in the 2D KdV equation. This new nonlinear equation is solved both analytically and numerically to show the competition between the linear forcing and damping in the formation of quasilongitudinal soliton in a 2D strongly coupled complex (dusty) plasma. Numerical simulation on the basis of the typical experimental plasma parameters and the analytical solution reveal that the neutral drag force is responsible for the usual exponential decay of the soliton, whereas Coriolis and/or Lorentz force is responsible for the algebraic decay as well as the oscillating tail formation of the soliton. The results are discussed in the context of the plasma crystal experiment.

  19. Magnetic Ugi-functionalized graphene oxide complexed with copper nanoparticles: Efficient catalyst toward Ullman coupling reaction in deep eutectic solvents.

    PubMed

    Shaabani, Ahmad; Afshari, Ronak

    2017-09-23

    Herein, we report the direct synthesis of carboxamide-functionalized graphene oxide (carboxamide-f-GO) for the development of new nanocatalysts, with highly dispersed particles, through covalent functionalization with a facile and direct strategy. This surface functionalization was carried out through a one-pot sequential four-component Ugi reaction. Subsequently, the Ugi-ligand decorated on the surface of the graphene oxide sheets coordinated with copper nanoparticles (Cu NPs) and finally covered with magnetic nanoparticles. The synthesized nanocatalyst was characterized by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance spectroscopy ((1)H NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and atomic force microscopy (AFM). The carboxamido nitrogen in Ugi-ligand showed high affinity toward complexation with Cu NPs and has a profound effect on the reactivity of the copper center in this nanocatalyst. The catalytic activity of nanocatalyst was investigated in Ullmann cross-coupling reaction for practical and direct access to corresponding N-aryl amines in a deep eutectic solvent as a green and recyclable media. The results showed the capability of this designed catalytic system through N-arylation of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, both of the nanocatalyst and deep eutectic solvent were easily recovered and reused for five consecutive runs. Copyright © 2017. Published by Elsevier Inc.

  20. Adhesive F-actin Waves: A Novel Integrin-Mediated Adhesion Complex Coupled to Ventral Actin Polymerization

    PubMed Central

    Case, Lindsay B.; Waterman, Clare M.

    2011-01-01

    At the leading lamellipodium of migrating cells, protrusion of an Arp2/3-nucleated actin network is coupled to formation of integrin-based adhesions, suggesting that Arp2/3-mediated actin polymerization and integrin-dependent adhesion may be mechanistically linked. Arp2/3 also mediates actin polymerization in structures distinct from the lamellipodium, in “ventral F-actin waves” that propagate as spots and wavefronts along the ventral plasma membrane. Here we show that integrins engage the extracellular matrix downstream of ventral F-actin waves in several mammalian cell lines as well as in primary mouse embryonic fibroblasts. These “adhesive F-actin waves” require a cycle of integrin engagement and disengagement to the extracellular matrix for their formation and propagation, and exhibit morphometry and a hierarchical assembly and disassembly mechanism distinct from other integrin-containing structures. After Arp2/3-mediated actin polymerization, zyxin and VASP are co-recruited to adhesive F-actin waves, followed by paxillin and vinculin, and finally talin and integrin. Adhesive F-actin waves thus represent a previously uncharacterized integrin-based adhesion complex associated with Arp2/3-mediated actin polymerization. PMID:22069459

  1. Rfc5, a small subunit of replication factor C complex, couples DNA replication and mitosis in budding yeast.

    PubMed Central

    Sugimoto, K; Shimomura, T; Hashimoto, K; Araki, H; Sugino, A; Matsumoto, K

    1996-01-01

    The inhibition of DNA synthesis prevents mitotic entry through the action of the S phase checkpoint. In the yeast Saccharomyces cerevisiae, an essential protein kinase, Spk1/Mec2/Rad53/Sad1, controls the coupling of S phase to mitosis. In an attempt to identify genes that genetically interact with Spk1, we have isolated a temperature-sensitive mutation, rfc5-1, that can be suppressed by overexpression of SPK1. The RFC5 gene encodes a small subunit of replication factor C complex. At the restrictive temperature, rfc5-1 mutant cells entered mitosis with unevenly separated or fragmented chromosomes, resulting in loss of viability. Thus, the rfc5 mutation defective for DNA replication is also impaired in the S phase checkpoint. Overexpression of POL30, which encodes the proliferating cell nuclear antigen, suppressed the replication defect of the rfc5 mutant but not its checkpoint defect. Taken together, these results suggested that replication factor C has a direct role in sensing the state of DNA replication and transmitting the signal to the checkpoint machinery. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8692942

  2. Selectivity control between Mizoroki-Heck and homo-coupling reactions for synthesising multinuclear metal complexes: unique addition effects of tertiary phosphines and O2.

    PubMed

    Yamazaki, Yasuomi; Ishitani, Osamu

    2017-04-05

    The addition of a tertiary phosphine and O2 to reaction solutions strongly affected the reactivity and selectivity of coupling reactions between transition metal complexes. The Mizoroki-Heck reaction between metal complexes with bromo and those with vinyl groups in the diimine ligand did not proceed using Pd(OAc)2 in the presence of 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (Sphos) under Ar but proceeded selectively after injection of air into the reaction vessel. In the absence of the phosphine ligand, on the other hand, not only the Mizoroki-Heck reaction but also a homo-coupling reaction between the metal complexes with the bromo groups proceeded at the same time. Mechanistic investigation showed that nanoparticles of Pd species were produced in the absence of the phosphine ligand and worked as catalysts for both the Mizoroki-Heck and homo-coupling reactions. On the other hand, larger Pd particles, which were produced in the presence of Sphos but after addition of air for oxidising Sphos, selectively catalysed the Mizoroki-Heck reaction. 'Molecular' Pd species that were stabilised in the presence of non-oxidised Sphos could not catalyse both coupling reactions under the reaction conditions. Based on these results, reaction conditions were established for the selective progress of the Mizoroki-Heck and the homo-coupling reactions.

  3. Coupling of complex aromatic ring vibrations to solvent through hydrogen bonds: effect of varied on-ring and off-ring hydrogen-bonding substitutions.

    PubMed

    Nucci, Nathaniel V; Scott, J Nathan; Vanderkooi, Jane M

    2008-04-03

    In this study, we examine the coupling of a complex ring vibration to solvent through hydrogen-bonding interactions. We compare phenylalanine, tyrosine, l-dopa, dopamine, norepinephrine, epinephrine, and hydroxyl-dl-dopa, a group of physiologically important small molecules that vary by single differences in H-bonding substitution. By examination of the temperature dependence of infrared absorptions of these molecules, we show that complex, many-atom vibrations can be coupled to solvent through hydrogen bonds and that the extent of that coupling is dependent on the degree of both on- and off-ring H-bonding substitution. The coupling is seen as a temperature-dependent frequency shift in infrared spectra, but the determination of the physical origin of that shift is based on additional data from temperature-dependent optical experiments and ab initio calculations. The optical experiments show that these small molecules are most sensitive to their immediate H-bonding environment rather than to bulk solvent properties. Ab initio calculations demonstrate H-bond-mediated vibrational coupling for the system of interest and also show that the overall small molecule solvent dependence is determined by a complex interplay of specific interactions and bulk solvation characteristics. Our findings indicate that a full understanding of biomolecule vibrational properties must include consideration of explicit hydrogen-bonding interactions with the surrounding microenvironment.

  4. NMR J-Coupling Constants of Tl-Pt Bonded Metal Complexes in Aqueous Solution: Ab Initio Molecular Dynamics and Localized Orbital Analysis.

    PubMed

    Ducati, Lucas C; Marchenko, Alex; Autschbach, Jochen

    2016-11-21

    The influence of solvent (water) coordination and dynamics on the electronic structure and nuclear magnetic resonance (NMR) indirect spin-spin coupling (J-coupling) constants in a series of Tl-Pt bonded complexes is investigated using Kohn-Sham (KS) Car-Parrinello molecular dynamics (CPMD) and relativistic hybrid KS NMR calculations with and without coordination to water. Coordination of the Tl center by water molecules has a dramatic impact on (1)J(Tl-Pt) and other J-coupling constants. It is shown that a previous computational study of the same complexes using static optimized structures and nonhybrid functionals was correct about the important role of the solvent but obtained reasonable agreement with experimental NMR data because of a cancellation of substantial errors. For example, the CPMD trajectories show that on average the inner coordination shell of Tl is not saturated, as previously assumed, which leads to poor agreement with experiment when the J-coupling constants are averaged over the CPMD trajectories using NMR calculations with nonhybrid functionals. The combination of CPMD with hybrid KS NMR calculations provides a much more realistic computational model that reproduces the large magnitudes of (1)J(Tl-Pt) and the correct trends for other coupling constants. An analysis of (1)J(Tl-Pt) in terms of localized orbitals shows that the presence of coordinating water molecules increases the capacity for covalent interactions between Tl and Pt. There is pronounced multicenter bonding along the metal-metal axis of the complexes.

  5. The Nickel-Pincer Complex in Lactate Racemase Is an Electron Relay and Sink that acts through Proton-Coupled Electron Transfer.

    PubMed

    Wang, Binju; Shaik, Sason

    2017-02-03

    QM/MM calculations reveal that the nickel pincer complex in lactate racemase functions as a reversible "single-center electrode" that accepts and donates back an electron. In this way, it catalyzes the isomerization process d-lactate⇌l-lactate through successive proton-coupled electron-transfer steps.

  6. Amidino ligands obtained from the coupling of 1-methylcytosine and nitrile: a new method to incorporate biomolecules into luminescent Re(CO)3 complexes.

    PubMed

    Gómez-Iglesias, Patricia; Martín-Alvarez, Jose Miguel; Miguel, Daniel; Villafañe, Fernando

    2015-10-28

    The formation of an amidino chelating ligand from the coupling reaction of 1-methylcytosine and nitrile is a new method herein reported for the incorporation of biologically relevant substrates into rhenium(i) tricarbonyl complexes. The reactions are carried out thermally or are microwave assisted.

  7. Direct synthesis of pyridines and quinolines by coupling of γ-amino-alcohols with secondary alcohols liberating H2 catalyzed by ruthenium pincer complexes.

    PubMed

    Srimani, Dipankar; Ben-David, Yehoshoa; Milstein, David

    2013-07-28

    A novel, one-step synthesis of substituted pyridine- and quinoline-derivatives was achieved by acceptorless dehydrogenative coupling of γ-aminoalcohols with secondary alcohols. The reaction involves consecutive C-N and C-C bond formation, catalyzed by a bipyridyl-based ruthenium pincer complex with a base.

  8. Detection of complex formation and determination of intermolecular geometry through electrical anharmonic coupling of molecular vibrations using electron-vibration-vibration two-dimensional infrared spectroscopy.

    PubMed

    Guo, Rui; Fournier, Frederic; Donaldson, Paul M; Gardner, Elizabeth M; Gould, Ian R; Klug, David R

    2009-10-14

    Electrical interactions between molecular vibrations can be non-linear and thereby produce intermolecular coupling even in the absence of a chemical bond. We use this fact to detect the formation of an intermolecular complex using electron-vibration-vibration two-dimensional infrared spectroscopy (EVV 2DIR) and also to determine the distance and angle between the two molecular species.

  9. Variation of exciton-vibrational coupling in photosystem II core complexes from Thermosynechococcus elongatus as revealed by single-molecule spectroscopy.

    PubMed

    Skandary, Sepideh; Hussels, Martin; Konrad, Alexander; Renger, Thomas; Müh, Frank; Bommer, Martin; Zouni, Athina; Meixner, Alfred J; Brecht, Marc

    2015-03-19

    The spectral properties and dynamics of the fluorescence emission of photosystem II core complexes are investigated by single-molecule spectroscopy at 1.6 K. The emission spectra are dominated by sharp zero-phonon lines (ZPLs). The sharp ZPLs are the result of weak to intermediate exciton-vibrational coupling and slow spectral diffusion. For several data sets, it is possible to surpass the effect of spectral diffusion by applying a shifting algorithm. The increased signal-to-noise ratio enables us to determine the exciton-vibrational coupling strength (Huang-Rhys factor) with high precision. The Huang-Rhys factors vary between 0.03 and 0.8. The values of the Huang-Rhys factors show no obvious correlation between coupling strength and wavelength position. From this result, we conclude that electrostatic rather than exchange or dispersive interactions are the main contributors to the exciton-vibrational coupling in this system.

  10. Fast and simultaneous determination of (1) H-(1) H and (1) H-(19) F scalar couplings in complex spin systems: Application of PSYCHE homonuclear broadband decoupling.

    PubMed

    Kakita, Veera Mohana Rao; Rachineni, Kavitha; Hosur, Ramakrishna V

    2017-07-21

    The present manuscript focuses on fast and simultaneous determination of (1) H-(1) H and (1) H-(19) F scalar couplings in fluorinated complex steroid molecules. Incorporation of broadband PSYCHE homonuclear decoupling in the indirect dimension of zero-quantum filtered diagonal experiments (F1-PSYCHE-DIAG) suppresses (1) H-(1) H scalar couplings; however, it retains (1) H-(19) F scalar couplings (along F1 dimension) for the (19) F coupled protons while preserving the pure-shift nature for (1) H resonances uncoupled to (19) F. In such cases, along the direct dimensions, (1) H-(1) H scalar coupling multiplets deconvolute and they appear as duplicated multiplets for the (19) F coupled protons, which facilitates unambiguous discrimination of (19) F coupled (1) H chemical sites from the others. Further, as an added advantage, data acquisition has been accelerated by invoking the known ideas of spectral aliasing in the F1-PSYCHE-DIAG scheme and experiments demand only ~10 min of spectrometer times. Copyright © 2017 John Wiley & Sons, Ltd.

  11. Complexity.

    PubMed

    Gómez-Hernández, J Jaime

    2006-01-01

    It is difficult to define complexity in modeling. Complexity is often associated with uncertainty since modeling uncertainty is an intrinsically difficult task. However, modeling uncertainty does not require, necessarily, complex models, in the sense of a model requiring an unmanageable number of degrees of freedom to characterize the aquifer. The relationship between complexity, uncertainty, heterogeneity, and stochastic modeling is not simple. Aquifer models should be able to quantify the uncertainty of their predictions, which can be done using stochastic models that produce heterogeneous realizations of aquifer parameters. This is the type of complexity addressed in this article.

  12. Statistical energy analysis modelling of complex structures as coupled sets of oscillators: Ensemble mean and variance of energy

    NASA Astrophysics Data System (ADS)

    Ji, L.; Mace, B. R.

    2008-11-01

    Expressions are derived for the ensemble means and variances of the subsystem energies of built-up systems comprising two subsystems. The approach is based on the Statistical Energy Analysis of two spring-coupled oscillators and sets of oscillators, or coupled continuous subsystems, described by Mace and Ji [The statistical energy analysis of coupled sets of oscillators, Proceedings of the Royal Society A 1824 (2007)]. The paper focuses on spring coupling, although similar results hold for more general forms of conservative coupling. Randomness is introduced into the system by assuming that the natural frequency spacings in each subsystem conform to certain statistical distributions. A "coupling coefficient parameter" is introduced which, together with the "coupling strength parameter" defined by Mace and Ji (2007), accounts for the statistics of the coupling stiffness. Various approximations and assumptions are made. It is seen that the variance of the excited subsystem depends primarily on the variance of the input power, which in turn depends on the variance of the number of modes of the excited subsystem in the frequency band of excitation and their mode shapes. The variance of the undriven subsystem, on the other hand, depends primarily on the variance of the intermodal coupling coefficients, which in turn depend on the variances of the number of in-band modes of both subsystems and their mode shapes. The cases of Poisson and Gaussian Orthogonal Ensemble natural frequency spacing statistics are considered. Numerical examples of two plates coupled by one or a number of springs are presented.

  13. Manipulating Nonlinear Emission and Cooperative Effect of CdSe/ZnS Quantum Dots by Coupling to a Silver Nanorod Complex Cavity

    PubMed Central

    Nan, Fan; Cheng, Zi-Qiang; Wang, Ya-Lan; Zhang, Qing; Zhou, Li; Yang, Zhong-Jian; Zhong, Yu-Ting; Liang, Shan; Xiong, Qihua; Wang, Qu-Quan

    2014-01-01

    Colloidal semiconductor quantum dots have three-dimensional confined excitons with large optical oscillator strength and gain. The surface plasmons of metallic nanostructures offer an efficient tool to enhance exciton-exciton coupling and excitation energy transfer at appropriate geometric arrangement. Here, we report plasmon-mediated cooperative emissions of approximately one monolayer of ensemble CdSe/ZnS quantum dots coupled with silver nanorod complex cavities at room temperature. Power-dependent spectral shifting, narrowing, modulation, and amplification are demonstrated by adjusting longitudinal surface plasmon resonance of silver nanorods, reflectivity and phase shift of silver nanostructured film, and mode spacing of the complex cavity. The underlying physical mechanism of the nonlinear excitation energy transfer and nonlinear emissions are further investigated and discussed by using time-resolved photoluminescence and finite-difference time-domain numerical simulations. Our results suggest effective strategies to design active plasmonic complex cavities for cooperative emission nanodevices based on semiconductor quantum dots. PMID:24787617

  14. Zero-point corrections and temperature dependence of HD spin-spin coupling constants of heavy metal hydride and dihydrogen complexes calculated by vibrational averaging.

    PubMed

    Mort, Brendan C; Autschbach, Jochen

    2006-08-09

    Vibrational corrections (zero-point and temperature dependent) of the H-D spin-spin coupling constant J(HD) for six transition metal hydride and dihydrogen complexes have been computed from a vibrational average of J(HD) as a function of temperature. Effective (vibrationally averaged) H-D distances have also been determined. The very strong temperature dependence of J(HD) for one of the complexes, [Ir(dmpm)Cp*H2]2 + (dmpm = bis(dimethylphosphino)methane) can be modeled simply by the Boltzmann average of the zero-point vibrationally averaged JHD of two isomers. For this complex and four others, the vibrational corrections to JHD are shown to be highly significant and lead to improved agreement between theory and experiment in most cases. The zero-point vibrational correction is important for all complexes. Depending on the shape of the potential energy and J-coupling surfaces, for some of the complexes higher vibrationally excited states can also contribute to the vibrational corrections at temperatures above 0 K and lead to a temperature dependence. We identify different classes of complexes where a significant temperature dependence of J(HD) may or may not occur for different reasons. A method is outlined by which the temperature dependence of the HD spin-spin coupling constant can be determined with standard quantum chemistry software. Comparisons are made with experimental data and previously calculated values where applicable. We also discuss an example where a low-order expansion around the minimum of a complicated potential energy surface appears not to be sufficient for reproducing the experimentally observed temperature dependence.

  15. Complex of 2-(methylthio)aniline with palladium(II) as an efficient catalyst for Suzuki-Miyaura C-C coupling in eco-friendly water.

    PubMed

    Rao, Gyandshwar K; Kumar, Arun; Bhunia, Mrinal; Singh, Mahabir P; Singh, Ajai Kumar

    2014-03-30

    2-(Methylthio)aniline (L1), a bidentate (S,N) ligand synthesized by the reaction of o-aminothiophenol with methyl iodide, on reacting with Na2PdCl4 in acetone and water gives a complex [PdL1Cl2] (1). Single crystal X-ray diffraction studies have revealed that the geometry of palladium in 1 is nearly square-planar and the ligand L1 is bound to the palladium through S and N in a bidentate coordination mode forming a five membered chelate ring. This complex functions as a thermally and air stable catalyst of high efficiency for Suzuki-Miyaura CC coupling reactions in water. It catalyzes CC coupling between various aryl bromides and phenylboronic acid under mild reaction conditions in water. TON value up to 93,000 has been obtained. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. High-frequency properties of 1.55 μm laterally complex coupled distributed feedback lasers fabricated by focused-ion-beam lithography

    NASA Astrophysics Data System (ADS)

    Rennon, S.; Bach, L.; Reithmaier, J. P.; Forchel, A.; Gentner, J. L.; Goldstein, L.

    2000-07-01

    Laterally complex coupled distributed feedback lasers have been fabricated by focused-ion-beam lithography on completely grown InGaAsP/InP laser structures emitting at 1.55 μm. The grating definition is based on implantation-enhanced quantum-well intermixing and wet chemical etching and allows the fabrication of complex coupled antiphase gratings without any further overgrowth step. Side-mode suppression ratios of 45 dB and bandwidths for direct modulation beyond 13 GHz were obtained for 300-μm-long devices. The lasers exhibit frequency-modulation response values lower than 200 MHz/mA and feature a low sensitivity to back-reflected light. Preliminary lifetime measurements over 7000 h continuous-wave operation at room temperature show no significant indication for long-time degradation.

  17. Excitation wavelength-dependent electron-phonon and electron-vibrational coupling in the CP29 antenna complex of green plants.

    PubMed

    Rätsep, Margus; Pieper, Jörg; Irrgang, Klaus-Dieter; Freiberg, Arvi

    2008-01-10

    Electron-phonon and electron-vibrational coupling strengths of a weakly (excitonically) coupled chlorophyll a S1-->S0 transition of the CP29 antenna complex of plant photosystem II were studied by difference fluorescence-line-narrowing spectroscopy at 4.5 K. A strong, almost linear increase of the electron-phonon coupling strength toward longer wavelengths was observed, with Huang-Rhys factors Sph increasing from 0.41+/-0.05 at 680 nm to about 0.66+/-0.07 at 688 nm. The former and latter wavelengths are located close to the peak and on the red edge of the inhomogeneous site distribution function, respectively. The experimentally obtained wavelength dependence of Sph may originate either from an alteration of the electron-phonon coupling strength by the local environment of the fluorescing chromophore and/or from the presence of two isoforms of CP29, which are characterized by different coupling strengths to the protein environment. The one-phonon profile peaks at omegam=22 cm(-1) and is described by an asymmetric function composed of a Gaussian low-energy wing and a Lorentzian high-energy tail with half-widths at half-maximum of 10+/-1 and 60+/-10 cm(-1), respectively. Thirty-nine individual vibrational modes between 90 and 1665 cm(-1) were resolved, and their Huang-Rhys factors were determined, which fall in the range between 0.0004 and 0.032. The broad feature present in the overlap region of phonon and vibrational modes at about 90 cm(-1) is characterized by S=0.048. An integral value of vibrational coupling strengths Svib=0.36+/-0.05 was determined, which is similar to that observed earlier for the trimeric LHC II complex.

  18. Receptor component protein (RCP): a member of a multi-protein complex required for G-protein-coupled signal transduction.

    PubMed

    Prado, M A; Evans-Bain, B; Dickerson, I M

    2002-08-01

    The calcitonin-gene-related peptide (CGRP) receptor component protein (RCP) is a 148-amino-acid intracellular protein that is required for G-protein-coupled signal transduction at receptors for the neuropeptide CGRP. RCP works in conjunction with two other proteins to constitute a functional CGRP receptor: calcitonin-receptor-like receptor (CRLR) and receptor-activity-modifying protein 1 (RAMP1). CRLR has the stereotypical seven-transmembrane topology of a G-protein-coupled receptor; it requires RAMP1 for trafficking to the cell surface and for ligand specificity, and requires RCP for coupling to the cellular signal transduction pathway. We have made cell lines that expressed an antisense construct of RCP and determined that CGRP-mediated signal transduction was reduced, while CGRP binding was unaffected. Furthermore, signalling at two other endogenous G-protein-coupled receptors was unaffected, suggesting that RCP was specific for a limited subset of receptors.

  19. Complex multireference configuration interaction calculations employing a coupled diabatic representation for the 2Pi(g) resonance states of N2(-).

    PubMed

    Honigmann, Michael; Buenker, Robert J; Liebermann, Heinz-Peter

    2009-07-21

    Complex multireference configuration interaction calculations have been carried out for the lowest resonance states of (2)Pi(g) symmetry of the N(2)(-) molecule. It is shown that there is a forbidden crossing between the two lowest roots of this symmetry and that a satisfactory calculation of vibrational levels and cross sections therefore requires inclusion of both states and the coupling between them. A diabatic representation for the two (2)Pi(g) states was determined and vibronic calculations of the cross sections for vibrational excitation were carried out with a two-dimensional complex variational program.

  20. Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

    PubMed Central

    Nan, Guangming; Ren, Fang

    2010-01-01

    Summary The Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation. Various aryltriazenes were investigated as electrophilic substrates at room temperature to give biaryls in good to excellent yields and showed good chemoselectivity over aryl halides in the reactions. PMID:20703375

  1. Decarboxylative Coupling Reaction in ESI(-)-MS/MS of 4-Nitrobenzyl 4-Hydroxybenzoates: Triplet Ion-Neutral Complex-Mediated 4-Nitrobenzyl Transfer

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping; Bai, Xingfeng; Fang, Liwen; Jiang, Kezhi; Li, Zuguang

    2016-05-01

    In negative electrospray ionization mass spectrometry of 4-nitrobenzyl 4-hydroxybenzoates, a decarboxylation reaction, which was significantly promoted by the presence of a nitro group on the benzyl group, competed with radical elimination reactions. Density functional theory calculations indicated that decarboxylation of deprotonated 4-nitrobenzyl vanillate occurred via a radical route involving homolytic cleavage of the Cbenzyl-O bond to give a triplet ion-neutral complex, followed by decarboxylative coupling.

  2. Fully-coupled pressure-based finite-volume framework for the simulation of fluid flows at all speeds in complex geometries

    NASA Astrophysics Data System (ADS)

    Xiao, Cheng-Nian; Denner, Fabian; van Wachem, Berend G. M.

    2017-10-01

    A generalized finite-volume framework for the solution of fluid flows at all speeds in complex geometries and on unstructured meshes is presented. Starting from an existing pressure-based and fully-coupled formulation for the solution of incompressible flow equations, the additional implementation of pressure-density-energy coupling as well as shock-capturing leads to a novel solver framework which is capable of handling flows at all speeds, including quasi-incompressible, subsonic, transonic and supersonic flows. The proposed numerical framework features an implicit coupling of pressure and velocity, which improves the numerical stability in the presence of complex sources and/or equations of state, as well as an energy equation discretized in conservative form that ensures an accurate prediction of temperature and Mach number across strong shocks. The framework is verified and validated by a large number of test cases, demonstrating the accurate and robust prediction of steady-state and transient flows in the quasi-incompressible as well as subsonic, transonic and supersonic speed regimes on structured and unstructured meshes as well as in complex domains.

  3. The role of range-separated Hartree-Fock exchange in the calculation of magnetic exchange couplings in transition metal complexes.

    PubMed

    Phillips, Jordan J; Peralta, Juan E

    2011-01-21

    We assess the dependence of magnetic exchange couplings on the variation of Hartree-Fock exchange (HFX) admixture in global hybrid functionals and the range-separation parameter ω in range-separated hybrid functionals in a set of 12 spin-1/2 binuclear transition metal complexes. The global hybrid PBEh (hybrid Perdew-Burke-Ernzerhof) and range-separated hybrids HSE (Heyd-Scuseria-Ernzerhof) and LC-ωPBE (long-range corrected hybrid PBE) are employed for this assessment, and exchange couplings are calculated from energy differences within the framework of the spin-projected approach. It is found that these functionals perform optimally for magnetic exchange couplings with 35% HFX admixture for PBEh, ω = 0.50 a.u.(-1) for LC-ωPBE, and ω at or near 0.0 a.u.(-1) for HSE (which corresponds to PBEh). We find that in their standard respective forms, LC-ωPBE slightly outperforms PBEh, while PBEh with 35% HFX yields exchange couplings closer to experiment than those of LC-ωPBE with ω = 0.50 a.u.(-1). Additionally, we show that the profile of exchange couplings with respect to ω in HSE is appreciably flat from 0 to 0.2 a.u.(-1). This combined with the fact that HSE is computationally more tractable than global hybrids makes HSE an attractive alternative for the evaluation of exchange couplings in extended systems. These results are rationalized with respect to how varying the parameters within these functionals affects the delocalization of the magnetic orbitals, and conclusions are made regarding the relative importance of range separation versus global mixing of HFX for the calculation of exchange couplings.

  4. Absorption Spectroscopy, Emissive Properties, and Ultrafast Intersystem Crossing Processes in Transition Metal Complexes: TD-DFT and Spin-Orbit Coupling.

    PubMed

    Daniel, Chantal

    2016-01-01

    Absorption spectroscopy, emissive properties, and ultrafast intersystem crossing processes in transition metal complexes are discussed in the light of recent developments in time-dependent density functional theory (TD-DFT), spin-orbit coupling (SOC) effects, and non-adiabatic excited states dynamics. Methodological highlights focus on spin-orbit and vibronic couplings and on the recent strategies available for simulating ultra-fast intersystem crossings (ISC).The role of SOC in the absorption spectroscopy of third-row transition metal complexes is illustrated by two cases studies, namely Ir(III) phenyl pyridine and Re(I) carbonyl bipyridine complexes.The problem of luminescence decay in third-row transition metal complexes handled by TD-DFT linear and quadratic response theories including SOC is exemplified by three studies: (1) the phosphorescence of Ir(III) complexes from the lowest triplet state; (2) the emissive properties of square planar Pt(II) complexes with bidentate and terdentate ligands characterized by low-lying metal-to-ligand-charge-transfer (MLCT) and metal-centered (MC) states; and (3) the ultra-fast luminescence decay of Re(I) carbonyl bipyridine halides via low-lying singlet and triplet charge transfer states delocalized over the bipyridine and the halide ligands.Ultrafast ISC occurring in spin crossover [Fe (bpy)3]2+, in [Ru (bpy)3]2+, and [Re (Br)(CO)3(bpy] complexes are deciphered thanks to recent developments based on various approaches, namely non-radiative rate theory within the Condon approximation, non-adiabatic surface hopping molecular dynamics, and quantum wave packet dynamics propagation.

  5. Ferromagnetic coupling by orthogonal magnetic orbitals in a heterodinuclear CuIIVIV=O complex and in a homodinuclear CuIICuII complex.

    PubMed

    Glaser, Thorsten; Theil, Hubert; Liratzis, Ioannis; Weyhermüller, Thomas; Bill, Eckhard

    2006-06-26

    The heterodinuclear complex [LCuIIVIVO] 1 was synthesized by using a new unsymmetric dinucleating ligand based on 1,8-naphthalenediol, whereas the homodinuclear CuIICuII complex 2 has a bridging beta-diketimineamid unit. Here we report on the synthesis, molecular structures, and magnetic properties of 1 and 2. In the solid state, both complexes dimerize to tetranuclear entities 1(2) and 2(2). The intradimer interaction in both complexes is ferromagnetic because of the orthogonality of the magnetic orbitals (J12 = +45.6 cm(-1) in 1 and +4.8 cm(-1) in 2). The interdimer interaction in 1 is also ferromagnetic, giving a St = 2 ground state.

  6. Trinuclear complexes of palladium(ii) with chalcogenated N-heterocyclic carbenes: catalysis of selective nitrile-primary amide interconversion and Sonogashira coupling.

    PubMed

    Dubey, Pooja; Gupta, Sonu; Singh, Ajai K

    2017-09-22

    3-Methyl-1-(2-(phenylthio/seleno)ethyl)-1H-benzo[d]imidazol-3-ium iodide (L1/L2), a precursor of sulfated/selenated N-heterocyclic carbene, was synthesized by the reaction of benzimidazole with 1,2-dichloroethane followed by treatment with PhS/SeNa and MeI. The reaction of L1/L2 with Ag2O followed by treatment with [Pd(CH3CN)2Cl2] (metal to ligand ratio 3 : 2), i.e. transmetallation, resulted in trinuclear palladium(ii) complexes [Pd3(L1/L2-HI)2(CH3CN)Cl6] (1-2). The complexes were characterized with (1)H, (13)C{(1)H} and (77)Se{(1)H} NMR (2 only), elemental analyses, HR-MS and single-crystal X-ray diffraction. The geometry of three Pd atoms in each complex is nearly square planar. The Pd-S/Se, Pd-C, Pd-N and Pd-Cl bond distances (Å) in 1/2 are 2.3179(19)/2.4312(10), 1.968(7)/1.952(4), 2.073(8)/2.079(4) and 2.2784(19)-2.298(2)/2.292(2)-2.3003(15), respectively. In both the complexes, all Cl are trans to each other. For the central Pd atom, two benzimidazole rings are also trans to each other. The C-HCl non-covalent interactions result in a three-dimensional network. The moisture and air insensitive trinuclear Pd(ii) complexes 1 and 2 are thermally stable and efficient as a catalyst for nitrile-amide interconversion and amine-free Sonogashira C-C coupling (in the presence of CuI). The optimum temperature is 80 °C for the interconversion and 110 °C for the coupling. The catalytic protocols are applicable to both aliphatic and aromatic amides/nitriles. The optimum catalyst loading is 1 mol% for the C-C coupling and 0.5 to 1 mol% for the interconversion. K2CO3 as a base gives the best result for Sonogashira C-C coupling. In the conversion of nitriles to amides, the formation of an acid was not detected. After using once, 1/2 can carry out the conversion of ten fresh lots of nitriles to amides with almost the same efficiency. The real catalytic species for the interconversion and coupling appear to be based on Pd(ii) and Pd(0), respectively.

  7. Enhancing the ferromagnetic coupling in extended phloroglucinol complexes by increasing the metal SOMO-ligand overlap: synthesis and characterization of a trinuclear Co(II)(3) triplesalophen complex.

    PubMed

    Oldengott, Jan; Stammler, Anja; Bögge, Hartmut; Glaser, Thorsten

    2015-06-07

    The triplesalophen complex [(baron(Me))Co(II)(3)] has been synthesized and characterized. The low-spin Co(II) ions possess an (2)A2 ground state with the magnetic orbitals of dyz type. These are well oriented for a strong π overlap with the bridging phloroglucinol, which results in the strongest ferromagnetic interactions by the spin-polarization mechanism for a 3d phloroglucinol complex.

  8. The role of complex networks in behavior epidemiology. Comment on "Coupled disease-behavior dynamics on complex networks: A review" by Z. Wang et al.

    NASA Astrophysics Data System (ADS)

    Zhao, Dawei; Wang, Lianhai

    2015-12-01

    Outbreaks of disease can trigger spontaneous behavioral response of individuals to consider prevention measures (mainly including medical cure and non-pharmaceutical intervention), which usually in turn influence the diffusion of epidemic, namely, forming the interplay between individual behaviors and epidemic dynamics. During the past decade, understanding such coupled disease-behavior dynamics in population has become a critical tool for predicting the disease evolution and designing effective prevention strategies [1-3].

  9. Spatial modulation of light transmission through a single microcavity by coupling of photosynthetic complex excitations to surface plasmons

    NASA Astrophysics Data System (ADS)

    Carmeli, Itai; Cohen, Moshik; Heifler, Omri; Lilach, Yigal; Zalevsky, Zeev; Mujica, Vladimiro; Richter, Shachar

    2015-06-01

    Molecule-plasmon interactions have been shown to have a definite role in light propagation through optical microcavities due to strong coupling between molecular excitations and surface plasmons. This coupling can lead to macroscopic extended coherent states exhibiting increment in temporal and spatial coherency and a large Rabi splitting. Here, we demonstrate spatial modulation of light transmission through a single microcavity patterned on a free-standing Au film, strongly coupled to one of the most efficient energy transfer photosynthetic proteins in nature, photosystem I. Here we observe a clear correlation between the appearance of spatial modulation of light and molecular photon absorption, accompanied by a 13-fold enhancement in light transmission and the emergence of a distinct electromagnetic standing wave pattern in the cavity. This study provides the path for engineering various types of bio-photonic devices based on the vast diversity of biological molecules in nature.

  10. A vibronic coupling hamiltonian to describe the ultrafast excited state dynamics of a Cu(i)-phenanthroline complex.

    PubMed

    Capano, Gloria; Penfold, Thomas J; Röthlisberger, Ursula; Tavernelli, Ivano

    2014-01-01

    We present a model Hamiltonian to study the nonadiabatic dynamics of photoexcited [Cu(dmp)2](+), (dmp = 2,9-dimethyl-1,10-phenanthroline). The relevant normal modes, identified by the magnitude of the first order coupling constants, correspond closely to those observed experimentally. The potential energy surfaces (PES) and nonadiabatic couplings for these modes are computed and provide a first interpretation of the nonadiabatic relaxation mechanism. The Hamiltonian incorporates both the low lying singlet and triplet states, which will make it possible to follow the dynamics from the photoexcitation event to the initial stages of intersystem crossing.

  11. Second order Møller-Plesset and coupled cluster singles and doubles methods with complex basis functions for resonances in electron-molecule scattering

    DOE PAGES

    White, Alec F.; Epifanovsky, Evgeny; McCurdy, C. William; ...

    2017-06-21

    The method of complex basis functions is applied to molecular resonances at correlated levels of theory. Møller-Plesset perturbation theory at second order and equation-of-motion electron attachment coupled-cluster singles and doubles (EOM-EA-CCSD) methods based on a non-Hermitian self-consistent-field reference are used to compute accurate Siegert energies for shape resonances in small molecules including N 2 - , CO - , CO 2 - , and CH 2 O - . Analytic continuation of complex θ-trajectories is used to compute Siegert energies, and the θ-trajectories of energy differences are found to yield more consistent results than those of total energies. Furthermore, themore » ability of such methods to accurately compute complex potential energy surfaces is investigated, and the possibility of using EOM-EA-CCSD for Feshbach resonances is explored in the context of e-helium scattering.« less

  12. Multi-pyridine decorated Fe(II) and Ru(II) complexes by Pd(0)-catalysed cross couplings: new building blocks for metallosupramolecular assemblies.

    PubMed

    Yang, Jiajia; Clegg, Jack K; Jiang, Qibai; Lui, Xiaoming; Yan, Hong; Zhong, Wei; Beves, Jonathon E

    2013-11-28

    Eight metal complexes of the type [M(tpy)2](2+) (tpy = 2,2':6',2''-terpyridine) featuring four pendant pyridine rings are reported and characterised by NMR, MS, absorption spectroscopy and electrochemical methods. Palladium-mediated Suzuki and Sonogashira cross-coupling reactions were performed on both free 4'-(3,5-dibromophenyl)-tpy and its Ru(II) complex in good yields. The ready N-alkylation of the pendant pyridyl units has significant influence on the absorption and electrochemical reduction of the complexes, processes which are localised on the periphery and leaves the [Ru(tpy)2](2+) core essentially unaffected. The binding of metal ions by the free pyridines is also demonstrated as means of assembling larger ordered non-covalent structures.

  13. A numerical method of reduced complexity for simulating vascular hemodynamics using coupled 0D lumped and 1D wave propagation models.

    PubMed

    Kroon, Wilco; Huberts, Wouter; Bosboom, Marielle; van de Vosse, Frans

    2012-01-01

    A computational method of reduced complexity is developed for simulating vascular hemodynamics by combination of one-dimensional (1D) wave propagation models for the blood vessels with zero-dimensional (0D) lumped models for the microcirculation. Despite the reduced dimension, current algorithms used to solve the model equations and simulate pressure and flow are rather complex, thereby limiting acceptance in the medical field. This complexity mainly arises from the methods used to combine the 1D and the 0D model equations. In this paper a numerical method is presented that no longer requires additional coupling methods and enables random combinations of 1D and 0D models using pressure as only state variable. The method is applied to a vascular tree consisting of 60 major arteries in the body and the head. Simulated results are realistic. The numerical method is stable and shows good convergence.

  14. Second order Møller-Plesset and coupled cluster singles and doubles methods with complex basis functions for resonances in electron-molecule scattering

    NASA Astrophysics Data System (ADS)

    White, Alec F.; Epifanovsky, Evgeny; McCurdy, C. William; Head-Gordon, Martin

    2017-06-01

    The method of complex basis functions is applied to molecular resonances at correlated levels of theory. Møller-Plesset perturbation theory at second order and equation-of-motion electron attachment coupled-cluster singles and doubles (EOM-EA-CCSD) methods based on a non-Hermitian self-consistent-field reference are used to compute accurate Siegert energies for shape resonances in small molecules including N2-, CO-, CO2-, and CH2O-. Analytic continuation of complex 𝜃 -trajectories is used to compute Siegert energies, and the 𝜃 -trajectories of energy differences are found to yield more consistent results than those of total energies. The ability of such methods to accurately compute complex potential energy surfaces is investigated, and the possibility of using EOM-EA-CCSD for Feshbach resonances is explored in the context of e-helium scattering.

  15. Distance-Independent Charge Recombination Kinetics in Cytochrome c - Cytochrome c Peroxidase Complexes: Compensating Changes in the Electronic Coupling and Reorganization Energies

    PubMed Central

    Jiang, Nan; Kuznetsov, Aleksey; Nocek, Judith M.; Hoffman, Brian M.; Crane, Brian R.; Hu, Xiangqian; Beratan, David N.

    2013-01-01

    Charge recombination rate constants vary no more than three-fold for inter-protein ET in the Zn-substituted wild type (WT) cytochrome c peroxidase (CcP):cytochrome c (Cc) complex and in complexes with four mutants of the Cc protein (i.e., F82S, F82W, F82Y and F82I), despite large differences in the ET distance. Theoretical analysis indicates that charge recombination for all complexes involves a combination of tunneling and hopping via Trp191. For three of the five structures (WT and F82S(W)), the protein favors hopping more than that in the other two structures that have longer heme→ZnP distances (F82Y(I)). Experimentally observed biexponential ET kinetics is explained by the complex locking in alternative coupling pathways, where the acceptor hole state is either primarily localized on ZnP (slow phase) or on Trp191 (fast phase). The large conformational differences between the CcP:Cc interface for the F82Y(I) mutants compared to the WT and F82S(W) complexes are predicted to change the reorganization energies for the CcP:Cc ET reactions because of changes in solvent exposure and inter-protein ET distances. Since the recombination reaction is likely to occur in the inverted Marcus regime, an increased reorganization energy compensates the decreased role for hopping recombination (and the longer transfer distance) in the F82Y(I) mutants. Taken together, coupling pathway and reorganization energy effects for the five protein complexes explains the observed insensitivity of recombination kinetics to donor-acceptor distance and docking pose and also reveals how hopping through aromatic residues can accelerate long-range ET. PMID:23895339

  16. Inventory of metal complexes circulating in plant fluids: a reliable method based on HPLC coupled with dual elemental and high-resolution molecular mass spectrometric detection.

    PubMed

    Flis, Paulina; Ouerdane, Laurent; Grillet, Louis; Curie, Catherine; Mari, Stéphane; Lobinski, Ryszard

    2016-08-01

    Description of metal species in plant fluids such as xylem, phloem or related saps remains a complex challenge usually addressed either by liquid chromatography-mass spectrometry, X-ray analysis or computational prediction. To date, none of these techniques has achieved a complete and true picture of metal-containing species in plant fluids, especially for the least concentrated complexes. Here, we present a generic analytical methodology for a large-scale (> 10 metals, > 50 metal complexes) detection, identification and semiquantitative determination of metal complexes in the xylem and embryo sac liquid of the green pea, Pisum sativum. The procedure is based on direct injection using hydrophilic interaction chromatography with dual detection by elemental (inductively coupled plasma mass spectrometry) and molecular (high-resolution electrospray mass spectrometry) mass spectrometric detection. Numerous and novel complexes of iron(II), iron(III), copper(II), zinc, manganese, cobalt(II), cobalt(III), magnesium, calcium, nickel and molybdenum(IV) with several ligands including nicotianamine, citrate, malate, histidine, glutamine, aspartic acid, asparagine, phenylalanine and others are observed in pea fluids and discussed. This methodology provides a large inventory of various types of metal complexes, which is a significant asset for future biochemical and genetic studies into metal transport/homeostasis. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  17. Analytical developments for the determination of monomethylmercury complexes with low molecular mass thiols by reverse phase liquid chromatography hyphenated to inductively coupled plasma mass spectrometry.

    PubMed

    Bouchet, Sylvain; Björn, Erik

    2014-04-25

    The behavior of monomethylmercury (MMHg) is markedly influenced by its distribution among complexes with low molecular mass (LMM) thiols but analytical methodologies dedicated to measure such complexes are very scarce up to date. In this work, we selected 15 LMM thiols often encountered in living organisms and/or in the environment and evaluated the separation of the 15 corresponding MMHg-thiol complexes by various high performance liquid chromatography (HPLC) columns. Two C18 (Phenomenex Synergi Hydro-RP and LunaC18(2)), two phenyl (Inertsil Ph 3 and 5μm) and one mixed-mode (Restek Ultra IBD) stationary phases were tested for their retention and resolution capacities of the various complexes. The objective was to find simple separation conditions with low organic contents in the mobile phase to provide optimal conditions for detection by inductively coupled plasma mass spectrometry (ICPMS). The 15 complexes were synthesized in solution and characterized by electrospray ionization-mass spectrometry (ESI-MS). The C18 columns tested were either not resolutive enough or too retentive. The 3μm phenyl stationary phase was able to resolve 10 out of the 15 complexes in less than 25min, under isocratic conditions. The mixed-mode column was especially effective at separating the most hydrophilic complexes (6 complexes out of the 15), corresponding to the main LMM thiols found in living organisms. The detection limits (DLs) for these two columns were in the low nanomolar range and overall slightly better for the phenyl column. The possibilities offered by such methodology were exemplified by monitoring the time-course concentrations of four MMHg-thiol complexes within a phytoplankton incubation containing MMHg in the presence of an excess of four added thiols. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Elemental ratios for characterization of quantum-dots populations in complex mixtures by asymmetrical flow field-flow fractionation on-line coupled to fluorescence and inductively coupled plasma mass spectrometry.

    PubMed

    Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T; Costa-Fernandez, Jose M; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo

    2014-08-11

    Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches.

  19. Public health impact of disease-behavior dynamics. Comment on "Coupled disease-behavior dynamics on complex networks: A review" by Z. Wang et al.

    NASA Astrophysics Data System (ADS)

    Wells, Chad R.; Galvani, Alison P.

    2015-12-01

    In a loop of dynamic feedback, behavior such as the decision to vaccinate, hand washing, or avoidance influences the progression of the epidemic, yet behavior is driven by the individual's and population's perceived risk of infection during an outbreak. In what we believe will become a seminal paper that stimulates future research as well as an informative teaching aid, Wang et. al. comprehensively review methodological advances that have been used to incorporate human behavior into epidemiological models on the effects of coupling disease transmission and behavior on complex social networks [1]. As illustrated by the recent outbreaks of measles and Middle Eastern Respiratory Syndrome (MERS), here we highlight the importance of coupling behavior and disease transmission that Wang et al. address.

  20. Effects of Competing First- and Second-Neighbour Couplings on the Propagation of Unstable Patterns in the Discrete Complex Cubic Ginzburg Landau Equation

    NASA Astrophysics Data System (ADS)

    Mohamadou, Alidou; KenfackJiotsa, A.; Kofané, T. C.

    2005-01-01

    We consider the stability of a continuous wave solution in line of vortices. The weakly nonlinear dynamics are governed by a one-dimensional (1D) discrete complex cubic Ginzburg Landau (DCCGL) equation. In particular, within the framework of linear stability analysis, we show how the Lange and Newell criterion for the Benjamin Feir instability is modified by the lattice effects as well as the second neighbour coupling. A noteworthy feature of the present study is that the initial condition is not disintegrated into trains of unstable patterns which have the shape of solitons in the absence of second neighbour couplings and quintic term. The simulations also show that the main observed physical signatures of this instability are a variety of propagative patterns for short-time scales and chaotic states for long-time scales where the linear perturbation analysis fails.

  1. The first example of MEEKC–ICP-MS coupling and its application for the analysis of anticancer platinum complexes

    PubMed Central

    Bytzek, Anna K.; Reithofer, Michael R.; Galanski, Markus; Groessl, Michael; Keppler, Bernhard K.; Hartinger, Christian G.

    2010-01-01

    MEEKC is a powerful electrodriven separation technique with many applications in different disciplines, including medicinal chemistry; however the coupling to highly sensitive and selective mass spectrometric detectors was limited due to the ion suppressive effect of the surfactant SDS. Herein, the first example of the coupling of MEEKC to ICP-MS is presented and an MEEKC method for the separation of Pt(II) and Pt(IV) anticancer drugs and drug candidates was developed. Different compositions of microemulsions were evaluated and the data were compared to those collected with standard ultraviolet/visible spectroscopy (UV/vis) detection. The MEEKC–ICP-MS system was found to be more sensitive than MEEKC–UV/vis and the analysis of UV/vis silent compounds is now achievable. Furthermore, the migration behavior of the Pt(II) and Pt(IV) compounds under investigation is correlated to their differences in structure. PMID:20349510

  2. Interligand C-C Coupling between α-Methyl N-Heterocycles and bipy or phen at Rhenium Tricarbonyl Complexes.

    PubMed

    Arévalo, Rebeca; Riera, Lucía; Pérez, Julio

    2017-04-03

    Intramolecular C-C coupling between N-bonded 1,2-dimethylimidazole, 2-methyloxazoline, or 2-methylpyridine and either 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen) ligands results from α-methyl group deprotonation in the coordination sphere of Re(CO)3 fragments. The nucleophilic CH2 group generated by the deprotonation attacks the 6 (bipy) or 2 (phen) positions of the diimines, dearomatizing the involved pyridine ring and generating new asymmetric, fac-capping tridentate ligands.

  3. Functional Coupling between HIV-1 Integrase and the SWI/SNF Chromatin Remodeling Complex for Efficient in vitro Integration into Stable Nucleosomes

    PubMed Central

    Lesbats, Paul; Botbol, Yair; Chevereau, Guillaume; Vaillant, Cédric; Calmels, Christina; Arneodo, Alain; Andreola, Marie-Line; Lavigne, Marc; Parissi, Vincent

    2011-01-01

    Establishment of stable HIV-1 infection requires the efficient integration of the retroviral genome into the host DNA. The molecular mechanism underlying the control of this process by the chromatin structure has not yet been elucidated. We show here that stably associated nucleosomes strongly inhibit in vitro two viral-end integration by decreasing the accessibility of DNA to integrase. Remodeling of the chromatinized template by the SWI/SNF complex, whose INI1 major component interacts with IN, restores and redirects the full-site integration into the stable nucleosome region. These effects are not observed after remodeling by other human remodeling factors such as SNF2H or BRG1 lacking the integrase binding protein INI1. This suggests that the restoration process depends on the direct interaction between IN and the whole SWI/SNF complex, supporting a functional coupling between the remodeling and integration complexes. Furthermore, in silico comparison between more than 40,000 non-redundant cellular integration sites selected from literature and nucleosome occupancy predictions also supports that HIV-1 integration is promoted in the genomic region of weaker intrinsic nucleosome density in the infected cell. Our data indicate that some chromatin structures can be refractory for integration and that coupling between nucleosome remodeling and HIV-1 integration is required to overcome this natural barrier. PMID:21347347

  4. Electrochemical Field-Effect Transistor Utilization to Study the Coupling Success Rate of Photosynthetic Protein Complexes to Cytochrome c.

    PubMed

    Takshi, Arash; Yaghoubi, Houman; Wang, Jing; Jun, Daniel; Beatty, J Thomas

    2017-03-30

    Due to the high internal quantum efficiency, reaction center (RC) proteins from photosynthetic organisms have been studied in various bio-photoelectrochemical devices for solar energy harvesting. In vivo, RC and cytochrome c (cyt c; a component of the biological electron transport chain) can form a cocomplex via interprotein docking. This mechanism can be used in vitro for efficient electron transfer from an electrode to the RC in a bio-photoelectrochemical device. Hence, the success rate in coupling RCs to cyt c is of great importance for practical applications in the future. In this work, we use an electrochemical transistor to study the binding of the RC to cytochrome. The shift in the transistor threshold voltage was measured in the dark and under illumination to estimate the density of cytochrome and coupled RCs on the gate of the transistor. The results show that ~33% of the cyt cs on the transistor gate were able to effectively couple with RCs. Due to the high sensitivity of the transistor, the approach can be used to make photosensors for detecting low light intensities.

  5. Electrochemical Field-Effect Transistor Utilization to Study the Coupling Success Rate of Photosynthetic Protein Complexes to Cytochrome c

    PubMed Central

    Takshi, Arash; Yaghoubi, Houman; Wang, Jing; Jun, Daniel; Beatty, J. Thomas

    2017-01-01

    Due to the high internal quantum efficiency, reaction center (RC) proteins from photosynthetic organisms have been studied in various bio-photoelectrochemical devices for solar energy harvesting. In vivo, RC and cytochrome c (cyt c; a component of the biological electron transport chain) can form a cocomplex via interprotein docking. This mechanism can be used in vitro for efficient electron transfer from an electrode to the RC in a bio-photoelectrochemical device. Hence, the success rate in coupling RCs to cyt c is of great importance for practical applications in the future. In this work, we use an electrochemical transistor to study the binding of the RC to cytochrome. The shift in the transistor threshold voltage was measured in the dark and under illumination to estimate the density of cytochrome and coupled RCs on the gate of the transistor. The results show that ~33% of the cyt cs on the transistor gate were able to effectively couple with RCs. Due to the high sensitivity of the transistor, the approach can be used to make photosensors for detecting low light intensities. PMID:28358305

  6. Computation of indirect nuclear spin-spin couplings with reduced complexity in pure and hybrid density functional approximations.

    PubMed

    Luenser, Arne; Kussmann, Jörg; Ochsenfeld, Christian

    2016-09-28

    We present a (sub)linear-scaling algorithm to determine indirect nuclear spin-spin coupling constants at the Hartree-Fock and Kohn-Sham density functional levels of theory. Employing efficient integral algorithms and sparse algebra routines, an overall (sub)linear scaling behavior can be obtained for systems with a non-vanishing HOMO-LUMO gap. Calculations on systems with over 1000 atoms and 20 000 basis functions illustrate the performance and accuracy of our reference implementation. Specifically, we demonstrate that linear algebra dominates the runtime of conventional algorithms for 10 000 basis functions and above. Attainable speedups of our method exceed 6 × in total runtime and 10 × in the linear algebra steps for the tested systems. Furthermore, a convergence study of spin-spin couplings of an aminopyrazole peptide upon inclusion of the water environment is presented: using the new method it is shown that large solvent spheres are necessary to converge spin-spin coupling values.

  7. Computation of indirect nuclear spin-spin couplings with reduced complexity in pure and hybrid density functional approximations

    NASA Astrophysics Data System (ADS)

    Luenser, Arne; Kussmann, Jörg; Ochsenfeld, Christian

    2016-09-01

    We present a (sub)linear-scaling algorithm to determine indirect nuclear spin-spin coupling constants at the Hartree-Fock and Kohn-Sham density functional levels of theory. Employing efficient integral algorithms and sparse algebra routines, an overall (sub)linear scaling behavior can be obtained for systems with a non-vanishing HOMO-LUMO gap. Calculations on systems with over 1000 atoms and 20 000 basis functions illustrate the performance and accuracy of our reference implementation. Specifically, we demonstrate that linear algebra dominates the runtime of conventional algorithms for 10 000 basis functions and above. Attainable speedups of our method exceed 6 × in total runtime and 10 × in the linear algebra steps for the tested systems. Furthermore, a convergence study of spin-spin couplings of an aminopyrazole peptide upon inclusion of the water environment is presented: using the new method it is shown that large solvent spheres are necessary to converge spin-spin coupling values.

  8. Electromagnetic coupling and array packing induce exchange of dominance on complex modes in 3D periodic arrays of spheres with large permittivity

    DOE PAGES

    Campione, Salvatore; Capolino, Filippo

    2016-01-25

    In this study, we investigate the effect on wave propagation of array packing and electromagnetic coupling between spheres in a three-dimensional (3D) lattice of microspheres with large permittivity that exhibit strong magnetic polarizability. We report on the complex wavenumber of Bloch waves in the lattice when each sphere is assumed to possess both electric and magnetic dipoles and full electromagnetic coupling is accounted for. While for small material-filling fractions we always determine one dominant mode with low attenuation constant, the same does not happen for large filling fractions, when electromagnetic coupling is included. In the latter case we peculiarly observemore » two dominant modes with low attenuation constant, dominant in different frequency ranges. The filling fraction threshold for which two dominant modes appear varies for different metamaterial constituents, as proven by considering spheres made by either titanium dioxide or lead telluride. As further confirmation of our findings, we retrieve the complex propagation constant of the dominant mode(s) via a field fitting procedure employing two sets of waves (direct and reflected) pertaining to two distinct modes, strengthening the presence of the two distinct dominant modes for increasing filling fractions. However, given that one mode only, with transverse polarization, at any given frequency, is dominant and able to propagate inside the lattice, we are able to accurately treat the metamaterial that is known to exhibit artificial magnetism as a homogeneous material with effective parameters, such as the refractive index. Results clearly show that the account of both electric and magnetic scattering processes in evaluating all electromagnetic intersphere couplings is essential for a proper description of the electromagnetic propagation in lattices.« less

  9. Electromagnetic coupling and array packing induce exchange of dominance on complex modes in 3D periodic arrays of spheres with large permittivity

    SciTech Connect

    Campione, Salvatore; Capolino, Filippo

    2016-01-25

    In this study, we investigate the effect on wave propagation of array packing and electromagnetic coupling between spheres in a three-dimensional (3D) lattice of microspheres with large permittivity that exhibit strong magnetic polarizability. We report on the complex wavenumber of Bloch waves in the lattice when each sphere is assumed to possess both electric and magnetic dipoles and full electromagnetic coupling is accounted for. While for small material-filling fractions we always determine one dominant mode with low attenuation constant, the same does not happen for large filling fractions, when electromagnetic coupling is included. In the latter case we peculiarly observe two dominant modes with low attenuation constant, dominant in different frequency ranges. The filling fraction threshold for which two dominant modes appear varies for different metamaterial constituents, as proven by considering spheres made by either titanium dioxide or lead telluride. As further confirmation of our findings, we retrieve the complex propagation constant of the dominant mode(s) via a field fitting procedure employing two sets of waves (direct and reflected) pertaining to two distinct modes, strengthening the presence of the two distinct dominant modes for increasing filling fractions. However, given that one mode only, with transverse polarization, at any given frequency, is dominant and able to propagate inside the lattice, we are able to accurately treat the metamaterial that is known to exhibit artificial magnetism as a homogeneous material with effective parameters, such as the refractive index. Results clearly show that the account of both electric and magnetic scattering processes in evaluating all electromagnetic intersphere couplings is essential for a proper description of the electromagnetic propagation in lattices.

  10. Modelling real disease dynamics with behaviourally adaptive complex networks. Comment on "Coupled disease-behavior dynamics on complex networks: A review" by Z. Wang et al.

    NASA Astrophysics Data System (ADS)

    Small, Michael

    2015-12-01

    Mean field compartmental models of disease transmission have been successfully applied to a host of different scenarios, and the Kermack-McKendrick equations are now a staple of mathematical biology text books. In Susceptible-Infected-Removed format these equations provide three coupled first order ordinary differential equations with a very mild nonlinearity and they are very well understood. However, underpinning these equations are two important assumptions: that the population is (a) homogeneous, and (b) well-mixed. These assumptions become closest to being true for diseases infecting a large portion of the population for which inevitable individual effects can be averaged away. Emerging infectious disease (such as, in recent times, SARS, avian influenza, swine flu and ebola) typically does not conform to this scenario. Individual contacts and peculiarities of the transmission network play a vital role in understanding the dynamics of such relatively rare infections - particularly during the early stages of an outbreak.

  11. Mixed-metal supramolecular complexes coupling phosphine-containing Ru(II) light absorbers to a reactive Pt(II) through polyazine bridging ligands.

    PubMed

    Swavey, Shawn; Fang, Zhenglai; Brewer, Karen J

    2002-05-06

    Supramolecular bimetallic Ru(II)/Pt(II) complexes [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) and their synthons [(tpy)Ru(L)(BL)](n)()(+) (where L = Cl(-), CH(3)CN, or PEt(2)Ph; tpy = 2,2':6',2''-terpyridine; and BL = 2,2'-bipyrimidine (bpm) or 2,3-bis(2-pyridyl)pyrazine (dpp)) have been synthesized and studied by cyclic voltammetry, electronic absorption spectroscopy, mass spectral analysis, and (31)P NMR. The mixed-metal bimetallic complexes couple phosphine-containing Ru chromophores to a reactive Pt site. These complexes show how substitution of the monodentate ligand on the [(tpy)RuCl(BL)](+) synthons can tune the properties of these light absorbers (LA) and incorporate a (31)P NMR tag by addition of the PEt(2)Ph ligand. The redox potentials for the Ru(III/II) couples occur at values greater than 1.00 V versus the Ag/AgCl reference electrode and can be tuned to more positive potentials on going from Cl(-) to CH(3)CN or PEt(2)Ph (E(1/2) = 1.01, 1.55, and 1.56 V, respectively, for BL = bpm). The BL(0/-) couple at -1.03 (bpm) and -1.05 V (dpp) for [(tpy)Ru(PEt(2)Ph)(BL)](2+) shifts dramatically to more positive potentials upon the addition of the PtCl(2) moiety to -0.34 (bpm) and -0.50 V (dpp) for the [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) bridged complex. The lowest energy electronic absorption for these complexes is assigned as the Ru(d pi) --> BL(pi*) metal-to-ligand charge transfer (MLCT) transition. These MLCT transitions are tuned to higher energy in the monometallic synthons when Cl(-) is replaced by CH(3)CN or PEt(2)Ph (516, 452, and 450 nm, for BL = bpm, respectively) and to lower energy when Pt(II)Cl(2) is coordinated to the bridging ligand (560 and 506 nm for BL = bpm or dpp). This MLCT state displays a broad emission at room temperature for all the dpp systems with the [(tpy)Ru(PEt(2)Ph)(dpp)PtCl(2)](2+) system exhibiting an emission centered at 750 nm with a lifetime of 56 ns. These supramolecular complexes [(tpy)Ru(PEt(2)Ph)(BL)PtCl(2)](2+) represent the

  12. Cell adhesion controlled by adhesion G protein-coupled receptor GPR124/ADGRA2 is mediated by a protein complex comprising intersectins and Elmo-Dock.

    PubMed

    Hernández-Vásquez, Magda Nohemí; Adame-García, Sendi Rafael; Hamoud, Noumeira; Chidiac, Rony; Reyes-Cruz, Guadalupe; Gratton, Jean Philippe; Côté, Jean-François; Vázquez-Prado, José

    2017-07-21

    Developmental angiogenesis and the maintenance of the blood-brain barrier involve endothelial cell adhesion, which is linked to cytoskeletal dynamics. GPR124 (also known as TEM5/ADGRA2) is an adhesion G protein-coupled receptor family member that plays a pivotal role in brain angiogenesis and in ensuring a tight blood-brain barrier. However, the signaling properties of GPR124 remain poorly defined. Here, we show that ectopic expression of GPR124 promotes cell adhesion, additive to extracellular matrix-dependent effect, coupled with filopodia and lamellipodia formation and an enrichment of a pool of the G protein-coupled receptor at actin-rich cellular protrusions containing VASP, a filopodial marker. Accordingly, GPR124-expressing cells also displayed increased activation of both Rac and Cdc42 GTPases. Mechanistically, we uncover novel direct interactions between endogenous GPR124 and the Rho guanine nucleotide exchange factors Elmo/Dock and intersectin (ITSN). Small fragments of either Elmo or ITSN1 that bind GPR124 blocked GPR124-induced cell adhesion. In addition, Gβγ interacts with the C-terminal tail of GPR124 and promotes the formation of a GPR124-Elmo complex. Furthermore, GPR124 also promotes the activation of the Elmo-Dock complex, as measured by Elmo phosphorylation on a conserved C-terminal tyrosine residue. Interestingly, Elmo and ITSN1 also interact with each other independently of their GPR124-recognition regions. Moreover, endogenous phospho-Elmo and ITSN1 co-localize with GPR124 at lamellipodia of adhering endothelial cells, where GPR124 expression contributes to polarity acquisition during wound healing. Collectively, our results indicate that GPR124 promotes cell adhesion via Elmo-Dock and ITSN. This constitutes a previously unrecognized complex formed of atypical and conventional Rho guanine nucleotide exchange factors for Rac and Cdc42 that is putatively involved in GPR124-dependent angiogenic responses. © 2017 by The American Society for

  13. Evaluation of nitrogen nuclear hyperfine and quadrupole coupling parameters for the proximal imidazole in myoglobin-azide, -cyanide, and -mercaptoethanol complexes by electron spin echo envelope modulation spectroscopy.

    PubMed

    Magliozzo, R S; Peisach, J

    1993-08-24

    Electron spin echo envelope modulation (ESEEM) spectroscopy and computer simulation of spectra has been used to evaluate the nitrogen nuclear hyperfine and quadrupole coupling parameters for the proximal imidazole nitrogen directly coordinated to iron in three low-spin heme complexes, myoglobin-azide, -cyanide, and -mercaptoethanol (MbN3, MbCN, and MbRS). The variability in the weak electron-nuclear coupling parameters reveals the electronic flexibility within the heme group that depends on properties of the exogenous ligands. For example, the isotropic component of the nitrogen nuclear hyperfine coupling ranges from 4.4 MHz for MbN3 to 2.2 MHz for both MbCN and MbRS. The weaker coupling in MbCN and MbRS is taken as evidence for delocalization of unpaired electron spin from iron into the exogenous anionic ligands. The value of e2Qq, the nuclear quadrupole coupling constant for the axial imidazole nitrogen in MbCN and MbRS, was 2.5 MHz but was significantly larger, 3.2 MHz, in MbN3. This large value is considered evidence for a weakened sigma bond between the proximal imidazole and ferric iron in this form, and for a feature contributing to the origin of the high spin-low spin equilibrium exhibited by MbN3 [Beetlestone, J., & George, P. (1964) Biochemistry 5, 707-714]. The ESEEM results have allowed a correlation to be made between the orientation of the g tensor axes, the orientation of the p-pi orbital of the proximal imidazole nitrogen, and sigma- and pi-bonding features of the axial ligands. Furthermore, the proximal imidazole is suggested to act as a pi-acceptor in low-spin heme complexes in order to support strong sigma electron donation from the lone pair orbital to iron. An evaluation of the nitrogen nuclear hyperfine coupling parameters for the porphyrin pyrrole sites in MbRS reveals a large inequivalence in isotropic components consistent with an orientation of rhombic axes (and g tensor axes) that eclipses the Fe-Npyrrole vector directions.

  14. Palladium(ii)-Acetylacetonato Complexes with Mesoionic Carbenes: Synthesis, Structures and Their Application in the Suzuki-Miyaura Cross Coupling Reaction.

    PubMed

    Hettmanczyk, Lara; Schmid, Bianca; Hohloch, Stephan; Sarkar, Biprajit

    2016-11-17

    A series of novel palladium(ii) acetylacetonato complexes bearing mesoionic carbenes (MICs) have been synthesized and characterized. The synthesis of the complexes of type (MIC)Pd(acac)I (MIC = 1-mesityl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene (1), 1,4-(2,4,6-methyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (2), 1,4-(2,6-diisopropyl)-phenyl-3-methyl-1,2,3-triazol-5-ylidene (3); acac = acetylacetonato) via direct metalation starting from the corresponding triazolium iodides and palladium(ii) acetylacetonate is described herein. All complexes were characterized by ¹H- and (13)C-NMR spectroscopy and high resolution mass spectrometry. Additionally, two of the complexes were characterized by single crystal X-ray crystallography confirming a square-planar coordination geometry of the palladium(ii) center. A delocalized bonding situation was observed within the triazolylidene rings as well as for the acac ligand respectively. Complex 2 was found to be an efficient pre-catalyst for the Suzuki-Miyaura cross coupling reaction between aryl-bromides or -chlorides with phenylboronic acid.

  15. Determination of size and element composition distributions of complex colloids by sedimentation field-flow fractionation—inductively coupled plasma mass spectrometry

    USGS Publications Warehouse

    Murphy, Deirdre M.

    1993-01-01

    Sedimentation field-flow fractionation (SdFFF) and inductively coupled plasma mass spectrometry (ICP-MS) have been directly combined and the resulting SdFFF-ICP-MS instrument can be used to produce element based size distributions of colloidal samples. Using appropriate tracer elements the size distributions of specific components can be picked out from a complex mixture. Changes in chemical composition of mixtures as a function of particle size can be readily monitored by plotting appropriate element atomic ratio distributions. These applications have been illustrated using data obtained with samples of the clay minerals kaolinite and illite and a natural suspended particulate matter from the Darling River (Australia).

  16. Detection of Maillard reaction products by a coupled HPLC-Fraction collector technique and FTIR characterization of Cu(II)-complexation with the isolated species

    NASA Astrophysics Data System (ADS)

    Ioannou, Aristos; Daskalakis, Vangelis; Varotsis, Constantinos

    2017-08-01

    The isolation of reaction products of asparagine with reducing sugars at alkaline pH and high temperature has been probed by a combination of high performance liquid chromatography (HPLC) coupled with a Fraction Collector. The UV-vis and FTIR spectra of the isolated Maillard reaction products showed structure-sensitive changes as depicted by deamination events and formation of asparagine-saccharide conjugates. The initial reaction species of the Asn-Gluc reaction were also characterized by Density Functional Theory (DFT) methods. Evidence for Cu (II) metal ion complexation with the Maillard reaction products is supported by UV-vis and FTIR spectroscopy.

  17. Base assisted C-C coupling between carbonyl and polypyridyl ligands in a Ru-NADH-type carbonyl complex.

    PubMed

    Ghosh, Debashis; Fukushima, Takashi; Kobayashi, Katsuaki; Sen, Susan; Kitagawa, Susumu; Kato, Tatsuhisa; Tanaka, Koji

    2017-03-27

    A reaction of a ruthenium(ii) NAD-type complex, [Ru(tpy)(pbn)(Cl)](+) (tpy = 2,2':6',2''-terpyridine; pbn = 2-(pyridin-2-yl)benzo[b][1,5]naphthyridine), with pressurized CO (2 MPa) at 150 °C in H2O selectively produced a two-electron reduced ruthenium(ii)-NADH-type carbonyl complex, [Ru(tpy)(pbnHH)(CO)](2+) (pbnHH = 2-(pyridin-2-yl)-5,10-dihydrobenzo[b][1,5]naphthyridine), rather than the oxidized [Ru(tpy)(pbn)(CO)](2+) complex. Indeed, [Ru(tpy)(pbnHH)(CO)](2+) was quantitatively oxidized to [Ru(tpy)(pbn)(CO)](2+) upon treatment with one equiv. of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ). The reactivity of [Ru(tpy)(pbnHH)(CO)](2+) with various bases was studied herein. Treatment of [Ru(tpy)(pbnHH)(CO)](2+) with a suitable organic base, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), resulted in the formation of a new five-membered Ru-CO-bridge metallacycle quantitatively in acetonitrile under air at room temperature. A probable mechanism was proposed for this reaction based on UV-vis, NMR, and EPR spectral studies and other experimental data. Furthermore, a reaction of the five membered Ru-CO-bridge metallacycle with NH4PF6 in CH3CN : H2O (1 : 1) under air smoothly produced another new six-membered Ru-OCO-bridge complex. A mechanism for the formation of a Ru-OCO-bridge complex was also proposed here on the basis of H2O(18) experiments, DDQ treatment and other experimental data. These newly synthesized complexes appended with NAD-type ligands may have potential use as renewable hydride sources for organic reductions.

  18. A time convolution less density matrix approach to the nonlinear optical response of a coupled system-bath complex

    SciTech Connect

    Richter, Marten Knorr, Andreas

    2010-04-15

    Time convolution less density matrix theory (TCL) is a powerful and well established tool to investigate strong system-bath coupling for linear optical spectra. We show that TCL equations can be generalised to the nonlinear optical response up to a chosen order in the optical field. This goal is achieved via an time convolution less perturbation scheme for the reduced density matrices of the electronic system. In our approach, the most important results are the inclusion of a electron-phonon coupling non-diagonal in the electronic states and memory effects of the bath: First, the considered model system is introduced. Second, the time evolution of the statistical operator is expanded with respect to the external optical field. This expansion is the starting point to explain how a TCL theory can treat the response up to in a certain order in the external field. Third, new TCL equations, including bath memory effects, are derived and the problem of information loss in the reduced density matrix is analysed. For this purpose, new dimensions are added to the reduced statistical operator to compensate lack of information in comparison with the full statistical operator. The theory is benchmarked with a two level system and applied to a three level system including non-diagonal phonon coupling. In our analysis of pump-probe experiments, the bath memory is influenced by the system state occupied between pump and probe pulse. In particular, the memory of the bath influences the dephasing process of electronic coherences developing during the time interval between pump and probe pulses.

  19. Selenium-ligated palladium(II) complexes as highly active catalysts for carbon-carbon coupling reactions: the Heck reaction.

    PubMed

    Yao, Qingwei; Kinney, Elizabeth P; Zheng, Chong

    2004-08-19

    Three selenium-ligated Pd(II) complexes were readily synthesized and shown to be extremely active catalysts for the Heck reaction of various aryl bromides, including deactivated and heterocyclic ones. The catalytic activity of the selenide-based Pd(II) complexes not only rivals but vastly outperforms that of the corresponding phosphorus and sulfur analogues. Practical advantages of the selenium-based catalysts include their straightforward synthesis and high activity in the absence of any additives as well as the enhanced stability of the selenide ligands toward air oxidation.

  20. Complex coupled distributed feedback laser monolithically integrated with electroabsorption modulator and semiconductor optical amplifier at 1.3-micrometer wavelength

    NASA Astrophysics Data System (ADS)

    Gerlach, Philipp; Peschke, Martin; Wenger, Thomas; Saravanan, Brem K.; Hanke, Christian; Lorch, Steffen; Michalzik, Rainer

    2006-04-01

    We report on the design and experimental results of monolithically integrated optoelectronic devices containing distributed feedback (DFB) laser, electroabsorption modulator (EAM), and semiconductor optical amplifier (SOA). Common InGaAlAs multiple quantum well (MQW) layers are used in all device sections. The incorporation of local lateral metal gratings in the DFB section enables device fabrication by single-step epitaxial growth. The emission wavelength is λ=1.3 micrometer. More than 2 mW single-mode fiber-coupled output power as well as 10 dB/2 V static extinction ratio have been achieved. Modulation experiments clearly show 10 Gbit/s capability.

  1. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states.

    PubMed

    Godtliebsen, Ian H; Christiansen, Ove

    2015-10-07

    It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.

  2. High-performance liquid chromatography coupled with post-column dual-bioactivity assay for simultaneous screening of xanthine oxidase inhibitors and free radical scavengers from complex mixture.

    PubMed

    Li, D Q; Zhao, J; Li, S P

    2014-06-06

    Xanthine oxidase (XO) can catalyze hypoxanthine and xanthine to generate uric acid and reactive oxygen species (ROS), including superoxide anion radical (O₂(•-)) and hydrogen peroxide. XO inhibitors and free radical scavengers are beneficial to the treatment of gout and many related diseases. In the present study, an on-line high-performance liquid chromatography (HPLC) coupled with post-column dual-bioactivity assay was established and successfully applied to simultaneously screening of XO inhibitors and free radical scavengers from a complex mixture, Oroxylum indicum extract. The integrated system of HPLC separation, bioactivity screening and mass spectrometry identification was proved to be simple and effective for rapid and sensitive screening of individual bioactive compounds in complex mixtures. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Calculating vibrational spectra without determining excited eigenstates: Solving the complex linear equations of damped response theory for vibrational configuration interaction and vibrational coupled cluster states

    NASA Astrophysics Data System (ADS)

    Godtliebsen, Ian H.; Christiansen, Ove

    2015-10-01

    It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde.

  4. Intermolecular C-C Coupling Between 1-Methyl-1,2,3-Triazole and 2,2'-Bipyridine or 1,10-Phenanthroline at Mo(II) Complexes.

    PubMed

    Riera, Lucia; Pérez, Julio; Fombona, Sergio; Díaz, Jesús

    2017-09-14

    Unsupported 1-methyl-1,2,3-triazole has been coordinated to {Mo(3-methallyl)(CO)2(N-N)} (N-N= 2,2'-bipyridine, bipy; or 1,10-phenanthroline,phen) fragments yielding cationic complexes which can be regarded as metalated triazolium salts. Their reactivity towards a strong base led to the deprotonation of the C5-H group of the triazole moiety, followed by an intermolecular nucleophilic attack to the ortho CH group of a bipy or phen ligand affording cyclic, bimetallic dearomatized C-C coupling products. The reaction of the neutral bipy derivative with an acid led to the formation of dihydropyridyl units by protonation of a CH group of the dearomatized rings, the dimeric nature of complexes being mantained upon protonation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Structural basis of G protein-coupled receptor-Gi protein interaction: formation of the cannabinoid CB2 receptor-Gi protein complex.

    PubMed

    Mnpotra, Jagjeet S; Qiao, Zhuanhong; Cai, Jian; Lynch, Diane L; Grossfield, Alan; Leioatts, Nicholas; Hurst, Dow P; Pitman, Michael C; Song, Zhao-Hui; Reggio, Patricia H

    2014-07-18

    In this study, we applied a comprehensive G protein-coupled receptor-Gαi protein chemical cross-linking strategy to map the cannabinoid receptor subtype 2 (CB2)-Gαi interface and then used molecular dynamics simulations to explore the dynamics of complex formation. Three cross-link sites were identified using LC-MS/MS and electrospray ionization-MS/MS as follows: 1) a sulfhydryl cross-link between C3.53(134) in TMH3 and the Gαi C-terminal i-3 residue Cys-351; 2) a lysine cross-link between K6.35(245) in TMH6 and the Gαi C-terminal i-5 residue, Lys-349; and 3) a lysine cross-link between K5.64(215) in TMH5 and the Gαi α4β6 loop residue, Lys-317. To investigate the dynamics and nature of the conformational changes involved in CB2·Gi complex formation, we carried out microsecond-time scale molecular dynamics simulations of the CB2 R*·Gαi1β1γ2 complex embedded in a 1-palmitoyl-2-oleoyl-phosphatidylcholine bilayer, using cross-linking information as validation. Our results show that although molecular dynamics simulations started with the G protein orientation in the β2-AR*·Gαsβ1γ2 complex crystal structure, the Gαi1β1γ2 protein reoriented itself within 300 ns. Two major changes occurred as follows. 1) The Gαi1 α5 helix tilt changed due to the outward movement of TMH5 in CB2 R*. 2) A 25° clockwise rotation of Gαi1β1γ2 underneath CB2 R* occurred, with rotation ceasing when Pro-139 (IC-2 loop) anchors in a hydrophobic pocket on Gαi1 (Val-34, Leu-194, Phe-196, Phe-336, Thr-340, Ile-343, and Ile-344). In this complex, all three experimentally identified cross-links can occur. These findings should be relevant for other class A G protein-coupled receptors that couple to Gi proteins. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  6. Isotope Coded Protein Labeling Coupled Immunoprecipitation (ICPL-IP): A Novel Approach for Quantitative Protein Complex Analysis From Native Tissue*

    PubMed Central

    Vogt, Andreas; Fuerholzner, Bettina; Kinkl, Norbert; Boldt, Karsten; Ueffing, Marius

    2013-01-01

    High confidence definition of protein interactions is an important objective toward the understanding of biological systems. Isotope labeling in combination with affinity-based isolation of protein complexes has increased in accuracy and reproducibility, yet, larger organisms—including humans—are hardly accessible to metabolic labeling and thus, a major limitation has been its restriction to small animals, cell lines, and yeast. As composition as well as the stoichiometry of protein complexes can significantly differ in primary tissues, there is a great demand for methods capable to combine the selectivity of affinity-based isolation as well as the accuracy and reproducibility of isotope-based labeling with its application toward analysis of protein interactions from intact tissue. Toward this goal, we combined isotope coded protein labeling (ICPL)1 with immunoprecipitation (IP) and quantitative mass spectrometry (MS). ICPL-IP allows sensitive and accurate analysis of protein interactions from primary tissue. We applied ICPL-IP to immuno-isolate protein complexes from bovine retinal tissue. Protein complexes of immunoprecipitated β-tubulin, a highly abundant protein with known interactors as well as the lowly expressed small GTPase RhoA were analyzed. The results of both analyses demonstrate sensitive and selective identification of known as well as new protein interactions by our method. PMID:23268931

  7. Isotope coded protein labeling coupled immunoprecipitation (ICPL-IP): a novel approach for quantitative protein complex analysis from native tissue.

    PubMed

    Vogt, Andreas; Fuerholzner, Bettina; Kinkl, Norbert; Boldt, Karsten; Ueffing, Marius

    2013-05-01

    High confidence definition of protein interactions is an important objective toward the understanding of biological systems. Isotope labeling in combination with affinity-based isolation of protein complexes has increased in accuracy and reproducibility, yet, larger organisms--including humans--are hardly accessible to metabolic labeling and thus, a major limitation has been its restriction to small animals, cell lines, and yeast. As composition as well as the stoichiometry of protein complexes can significantly differ in primary tissues, there is a great demand for methods capable to combine the selectivity of affinity-based isolation as well as the accuracy and reproducibility of isotope-based labeling with its application toward analysis of protein interactions from intact tissue. Toward this goal, we combined isotope coded protein labeling (ICPL)(1) with immunoprecipitation (IP) and quantitative mass spectrometry (MS). ICPL-IP allows sensitive and accurate analysis of protein interactions from primary tissue. We applied ICPL-IP to immuno-isolate protein complexes from bovine retinal tissue. Protein complexes of immunoprecipitated β-tubulin, a highly abundant protein with known interactors as well as the lowly expressed small GTPase RhoA were analyzed. The results of both analyses demonstrate sensitive and selective identification of known as well as new protein interactions by our method.

  8. Conservation laws, radiative decay rates, and excited state localization in organometallic complexes with strong spin-orbit coupling.

    PubMed

    Powell, B J

    2015-06-30

    There is longstanding fundamental interest in 6-fold coordinated d(6) (t(2g)(6)) transition metal complexes such as [Ru(bpy)3](2+) and Ir(ppy)3, particularly their phosphorescence. This interest has increased with the growing realisation that many of these complexes have potential uses in applications including photovoltaics, imaging, sensing, and light-emitting diodes. In order to design new complexes with properties tailored for specific applications a detailed understanding of the low-energy excited states, particularly the lowest energy triplet state, T1, is required. Here we describe a model of pseudo-octahedral complexes based on a pseudo-angular momentum representation and show that the predictions of this model are in excellent agreement with experiment - even when the deviations from octahedral symmetry are large. This model gives a natural explanation of zero-field splitting of T1 and of the relative radiative rates of the three sublevels in terms of the conservation of time-reversal parity and total angular momentum modulo two. We show that the broad parameter regime consistent with the experimental data implies significant localization of the excited state.

  9. Preferencial Affinity of Humic-Metal Interactions Coupled With Phosphatase Hydrolysis of Humic-Organic Phosphorus Complex

    USDA-ARS?s Scientific Manuscript database

    Information is limited on the enzymatic hydrolysis of P compounds associated with indigenous Humic (HA) and fulvic (FA) acids extracted from an Ultisol, and even less information is available on the resistance to phosphatase hydrolysis of known P compounds complexed to HA and FA. Little information ...

  10. Evaluation of Multi-tRNA Synthetase Complex by Multiple Reaction Monitoring Mass Spectrometry Coupled with Size Exclusion Chromatography

    PubMed Central

    Kim, Jun Seok; Lee, Cheolju

    2015-01-01

    Eight aminoacyl-tRNA synthetases (M, K, Q, D, R, I, EP and LARS) and three auxiliary proteins (AIMP1, 2 and 3) are known to form a multi-tRNA synthetase complex (MSC) in mammalian cells. We combined size exclusion chromatography (SEC) with reversed-phase liquid chromatography multiple reaction monitoring mass spectrometry (RPLC-MRM-MS) to characterize MSC components and free ARS proteins in human embryonic kidney (HEK 293T) cells. Crude cell extract and affinity-purified proteins were fractionated by SEC in non-denaturing state and ARSs were monitored in each fraction by MRM-MS. The eleven MSC components appeared mostly in earlier SEC fractions demonstrating their participation in complex formation. TARSL2 and AIMP2-DX2, despite their low abundance, were co-purified with KARS and detected in the SEC fractions, where MSC appeared. Moreover, other large complex-forming ARS proteins, such as VARS and FARS, were detected in earlier fractions. The MRM-MS results were further confirmed by western blot analysis. Our study demonstrates usefulness of combined SEC-MRM analysis for the characterization of protein complexes and in understanding the behavior of minor isoforms or variant proteins. PMID:26544075

  11. Concerted proton-coupled electron transfers in aquo/hydroxo/oxo metal complexes: Electrochemistry of [OsII(bpy)2py(OH2)]2+ in water

    PubMed Central

    Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel; Teillout, Anne-Lucie

    2009-01-01

    Kinetic analysis of the successive oxidative cyclic voltammetric responses of [OsII(bpy)2py(OH2)]2+ in buffered water, together with determination of H/D isotope effects, has allowed the determination of the mechanisms of the successive proton-coupled electron transfers that convert the OsII-aquo complex into the OsIII-hydroxo complex and the later into the OsIV-oxo complex. The stepwise pathways prevail over the concerted pathway in the first case. However, very large concentrations of a base, such as acetate, trigger the beginning of a concerted reaction. The same trend appears, but to a much larger extent, when high local concentration of carboxylates are attached close to the Os complex. The OsIII-hydroxo/OsIV-oxo couple is globally much slower and concerted pathways predominate over the stepwise pathways. Water is, however, not an appropriate proton acceptor in this respect. Other bases, such as citrate or phosphate, are instead quite effective for triggering concerted pathways. Here, we suggest factors causing these contrasting behaviors, providing a practical illustration of the prediction that concerted processes are an efficient way of avoiding high-energy intermediates. Observation of a strong decelerating effect of inactive ions together with the positive role of high local concentrations of carboxylates to initiate a concerted route underscores the variety of structural and medium factors that may operate to modulate and control the occurrence of concerted pathways. These demonstrations and analyses of the occurrence of concerted pathways in an aquo–hydroxo–oxo series are expected to serve as guidelines for studies in term of methodology and factor analysis. PMID:19584254

  12. Kinetically coupled folding of a single HIV-1 glycoprotein 41 complex in viral membrane fusion and inhibition.

    PubMed

    Jiao, Junyi; Rebane, Aleksander A; Ma, Lu; Gao, Ying; Zhang, Yongli

    2015-06-02

    HIV-1 glycoprotein 41 (gp41) mediates viral entry into host cells by coupling its folding energy to membrane fusion. Gp41 folding is blocked by fusion inhibitors, including the commercial drug T20, to treat HIV/AIDS. However, gp41 folding intermediates, energy, and kinetics are poorly understood. Here, we identified the folding intermediates of a single gp41 trimer-of-hairpins and measured their associated energy and kinetics using high-resolution optical tweezers. We found that folding of gp41 hairpins was energetically independent but kinetically coupled: Each hairpin contributed a folding energy of ∼-23 kBT, but folding of one hairpin successively accelerated the folding rate of the next one by ∼20-fold. Membrane-mimicking micelles slowed down gp41 folding and reduced the stability of the six-helix bundle. However, the stability was restored by cooperative folding of the membrane-proximal external region. Surprisingly, T20 strongly inhibited gp41 folding by actively displacing the C-terminal hairpin strand in a force-dependent manner. The inhibition was abolished by a T20-resistant gp41 mutation. The energetics and kinetics of gp41 folding established by us provides a basis to understand viral membrane fusion, infection, and therapeutic intervention.

  13. Infrared diode laser spectroscopy of the Ne-D2O van der Waals complex: Strong Coriolis and angular-radial coupling

    NASA Astrophysics Data System (ADS)

    Li, Song; Zheng, Rui; Zhu, Yu; Duan, Chuanxi

    2011-10-01

    Four internal-rotation/vibration bands of the Ne-D2O complex have been measured in the v2 bend region of D2O using a tunable infrared diode laser spectrometer to probe a slit supersonic expansion. Three ortho bands are excited from the ground state Σ(000) to the Σ and Π(111, υ2 = 1) internal rotor states and the n = 1, Σ(000, υ2 = 1) stretching-internal rotor combination state. Strong perturbations between the excited vibrational states are evident. The observed spectra are analyzed separately with a three-state J-dependent Coriolis plus J-independent angular-radial coupling model [M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 106, 3078 (1997), 10.1063/1.473051] and a three-state Coriolis coupling model [R. C. Cohen and R. J. Saykally, J. Chem. Phys. 95, 7891 (1991), 10.1063/1.461318]. The former model works more successfully than the latter. Molecular constants for the ground and excited vibrational states of ortho 20Ne-D2O isotopomer as well as the Coriolis and angular-radial coupling constants are determined accurately. The van der Waals stretching frequency is estimated to be νs = 24.85 cm-1 in the ground state and decreases to about 20.8 cm-1 upon vibrational excitation of the D2O bend.

  14. Infrared diode laser spectroscopy of the Ne-D2O van der Waals complex: strong Coriolis and angular-radial coupling.

    PubMed

    Li, Song; Zheng, Rui; Zhu, Yu; Duan, Chuanxi

    2011-10-07

    Four internal-rotation/vibration bands of the Ne-D(2)O complex have been measured in the v(2) bend region of D(2)O using a tunable infrared diode laser spectrometer to probe a slit supersonic expansion. Three ortho bands are excited from the ground state Σ(0(00)) to the Σ and Π(1(11), υ(2) = 1) internal rotor states and the n = 1, Σ(0(00), υ(2) = 1) stretching-internal rotor combination state. Strong perturbations between the excited vibrational states are evident. The observed spectra are analyzed separately with a three-state J-dependent Coriolis plus J-independent angular-radial coupling model [M. J. Weida and D. J. Nesbitt, J. Chem. Phys. 106, 3078 (1997)] and a three-state Coriolis coupling model [R. C. Cohen and R. J. Saykally, J. Chem. Phys. 95, 7891 (1991)]. The former model works more successfully than the latter. Molecular constants for the ground and excited vibrational states of ortho (20)Ne-D(2)O isotopomer as well as the Coriolis and angular-radial coupling constants are determined accurately. The van der Waals stretching frequency is estimated to be ν(s) = 24.85 cm(-1) in the ground state and decreases to about 20.8 cm(-1) upon vibrational excitation of the D(2)O bend.

  15. New Ru(II)/Os(II)-polypyridyl complexes for coupling to TiO2 surfaces through acetylacetone functionality and studies on interfacial electron-transfer dynamics.

    PubMed

    Banerjee, Tanmay; Biswas, Abul Kalam; Sahu, Tuhin Subhra; Ganguly, Bishwajit; Das, Amitava; Ghosh, Hirendra Nath

    2014-09-28

    New Ru(ii)- and Os(ii)-polypyridyl complexes have been synthesized with pendant acetylacetone (acac) functionality for anchoring on nanoparticulate TiO2 surfaces with a goal of developing an alternate sensitizer that could be utilized for designing an efficient dye-sensitized solar cell (DSSC). Time-resolved transient absorption spectroscopic studies in the femtosecond time domain have been carried out. The charge recombination rates are observed to be very slow, compared with those for strongly coupled dye molecules having catechol as the anchoring functionality. The results of such studies reveal that electron-injection rates from the metal complex-based LUMO to the conduction band of TiO2 are faster than one would expect for an analogous complex in which the chromophoric core and the anchoring moiety are separated with multiple saturated C-C linkages. Such an observation is rationalized based on computational studies, and a relatively smaller spatial distance between the dye LUMO and the TiO2 surface accounted for this. Results of this study are compared with those for analogous complexes having a gem-dicarboxy group as the anchoring functionality for covalent binding to the TiO2 surface to compare the role of binding functionalities on electron-transfer dynamics.

  16. A cyanide-bridged trinuclear Fe(II)-Ru(II)-Fe(II) complex with three stable states: synthesis, crystal structures, electronic couplings and magnetic properties.

    PubMed

    Ma, Xiao; Hu, Sheng-Min; Tan, Chun-Hong; Wen, Yue-Hong; Zhu, Qi-Long; Shen, Chao-Jun; Sheng, Tian-Lu; Wu, Xin-Tao

    2012-10-21

    Treatment of trans-(Ph-tpy)Ru(PPh(3))(CN)(2) (Ph-tpy = 4'-phenyl-2,2':6',2''-terpyridine, PPh(3) = triphenylphosphine) with 2 equiv of Cp(dppe)Fe(NCCH(3))Br (dppe = bis(diphenylphosphino)ethane) in the presence of NH(4)PF(6) produced a trinuclear cyanide-bridged complex, trans-[Cp(dppe)Fe(CN)(Ph-tpy)Ru(PPh(3))(CN)Fe(dppe)Cp][PF(6)](2) (1[PF(6)](2)). Its one-electron oxidation product (1[PF(6)](3)) and two-electron-oxidation product (1[PF(6)](4)) were obtained by oxidation with (Cp)(2)FePF(6) and AgPF(6), respectively. Firstly, the crystal structures of the cyanide-bridged complexes with three stable states were fully characterized. The reversible electrochemistry measurement of 1(2)(+) shows the presence of a long range intervalence interaction between the external iron centres. Both 1(3)(+) and 1(4)(+) were considered to be Class II mixed valence complexes according to the classification of Robin and Day. Magnetic analysis indicated the presence of a moderately strong antiferromagnetic coupling between the two remote Fe(III) ions across the Fe-NC-Ru-CN-Fe array in 1(4)(+). This proves that the Ru(II)-dicyano complex is a bridging ligand that can transmit electro- and magneto-communication.

  17. Enzyme-Coupled Nanoparticles-Assisted Laser Desorption Ionization Mass Spectrometry for Searching for Low-Mass Inhibitors of Enzymes in Complex Mixtures

    NASA Astrophysics Data System (ADS)

    Salwiński, Aleksander; Da Silva, David; Delépée, Raphaël; Maunit, Benoît

    2014-04-01

    In this report, enzyme-coupled magnetic nanoparticles (EMPs) were shown to be an effective affinity-based tool for finding specific interactions between enzymatic targets and the low-mass molecules in complex mixtures using classic MALDI-TOF apparatus. EMPs used in this work act as nonorganic matrix enabling ionization of small molecules without any interference in the low-mass range (enzyme-coupled nanoparticles-assisted laser desorption ionization MS, ENALDI MS) and simultaneously carry the superficial specific binding sites to capture inhibitors present in a studied mixture. We evaluated ENALDI approach in two complementary variations: `ion fading' (IF-ENALDI), based on superficial adsorption of inhibitors and `ion hunting' (IH-ENALDI), based on selective pre-concentration of inhibitors. IF-ENALDI was applied for two sets of enzyme-inhibitor pairs: tyrosinase-glabridin and trypsin-leupeptin and for the real plant sample: Sparrmannia discolor leaf and stem methanol extract. The efficacy of IH-ENALDI was shown for the pair of trypsin-leupeptin. Both ENALDI approaches pose an alternative for bioassay-guided fractionation, the common method for finding inhibitors in the complex mixtures.

  18. Enzyme-coupled nanoparticles-assisted laser desorption ionization mass spectrometry for searching for low-mass inhibitors of enzymes in complex mixtures.

    PubMed

    Salwiński, Aleksander; Da Silva, David; Delépée, Raphaël; Maunit, Benoît

    2014-04-01

    In this report, enzyme-coupled magnetic nanoparticles (EMPs) were shown to be an effective affinity-based tool for finding specific interactions between enzymatic targets and the low-mass molecules in complex mixtures using classic MALDI-TOF apparatus. EMPs used in this work act as nonorganic matrix enabling ionization of small molecules without any interference in the low-mass range (enzyme-coupled nanoparticles-assisted laser desorption ionization MS, ENALDI MS) and simultaneously carry the superficial specific binding sites to capture inhibitors present in a studied mixture. We evaluated ENALDI approach in two complementary variations: 'ion fading' (IF-ENALDI), based on superficial adsorption of inhibitors and 'ion hunting' (IH-ENALDI), based on selective pre-concentration of inhibitors. IF-ENALDI was applied for two sets of enzyme-inhibitor pairs: tyrosinase-glabridin and trypsin-leupeptin and for the real plant sample: Sparrmannia discolor leaf and stem methanol extract. The efficacy of IH-ENALDI was shown for the pair of trypsin-leupeptin. Both ENALDI approaches pose an alternative for bioassay-guided fractionation, the common method for finding inhibitors in the complex mixtures.

  19. A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper-Lewis Acid Complex.

    PubMed

    Lionetti, Davide; de Ruiter, Graham; Agapie, Theodor

    2016-04-20

    The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is hyponitrite (N2O2(2-)), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium-tricopper complex generating a trans-hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the hyponitrite species with Brønsted acids leads to the generation of N2O, demonstrating the viability of the hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable hyponitrite intermediate.

  20. Calculation of Heats of Formation for Zn Complexes: Comparison of Density Functional Theory, Second Order Perturbation Theory, Coupled-Cluster and Complete Active Space Methods

    PubMed Central

    Weaver, Michael N.; Ma, Dongxia; Kim, Hyun Jung

    2013-01-01

    Heats of formation were predicted for nine ZnX complexes (X= Zn, H, O, F2, S, Cl, Cl2, CH3, (CH3)2) using fourteen density functionals, MP2 calculations and the CCSD and CCSD(T) coupled-cluster methods. Calculations utilized the correlation consistent cc-pVTZ and aug-cc-pVTZ basis sets. Heats of formation were most accurately predicted by the TPSSTPSS and TPSSKCIS density functionals, and the BLYP, B3LYP, MP2, CCSD and CCSD(T) levels were among the poorest performing methods based on accuracy. A wide range of Zn2 equilibrium bond distances were predicted, indicating that many of the studied levels of theory may be unable to adequately describe this transition metal dimer. To further benchmark the accuracy of the density functional methods, high-level CASSCF and CASPT2 calculations were performed to estimate bond dissociation energies, equilibrium bond lengths and heats of formation for the diatomic Zn complexes and the latter two quantities were compared with the results of DFT, MP2 and coupled-cluster calculations as well as experimental values. PMID:24409106

  1. αT-Catenin Is a Constitutive Actin-binding α-Catenin That Directly Couples the Cadherin·Catenin Complex to Actin Filaments*

    PubMed Central

    Wickline, Emily D.; Dale, Ian W.; Merkel, Chelsea D.; Heier, Jonathon A.; Stolz, Donna B.

    2016-01-01

    α-Catenin is the primary link between the cadherin·catenin complex and the actin cytoskeleton. Mammalian αE-catenin is allosterically regulated: the monomer binds the β-catenin·cadherin complex, whereas the homodimer does not bind β-catenin but interacts with F-actin. As part of the cadherin·catenin complex, αE-catenin requires force to bind F-actin strongly. It is not known whether these properties are conserved across the mammalian α-catenin family. Here we show that αT (testes)-catenin, a protein unique to amniotes that is expressed predominantly in the heart, is a constitutive actin-binding α-catenin. We demonstrate that αT-catenin is primarily a monomer in solution and that αT-catenin monomer binds F-actin in cosedimentation assays as strongly as αE-catenin homodimer. The β-catenin·αT-catenin heterocomplex also binds F-actin with high affinity unlike the β-catenin·αE-catenin complex, indicating that αT-catenin can directly link the cadherin·catenin complex to the actin cytoskeleton. Finally, we show that a mutation in αT-catenin linked to arrhythmogenic right ventricular cardiomyopathy, V94D, promotes homodimerization, blocks β-catenin binding, and in cardiomyocytes disrupts localization at cell-cell contacts. Together, our data demonstrate that αT-catenin is a constitutively active actin-binding protein that can physically couple the cadherin·catenin complex to F-actin in the absence of tension. We speculate that these properties are optimized to meet the demands of cardiomyocyte adhesion. PMID:27231342

  2. A Coupled Thermo-Mechanical Simulation on Squeeze Casting Solidification Process of Three-Dimensional Geometrically Complex Components

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Han, Zhiqiang; Wang, Feifan; Sun, Jue; Xu, Shanxin

    A coupled thermo-mechanical simulation method for three-dimensional squeeze casting components has been developed. The simulation was achieved by using ANSYS Parametric Design Language (APDL). The effect of volume shrinkage due to cooling and solidification, the effect of pressure on the latent heat release, the mutual dependence of interfacial heat transfer and casting deformation, and materials behavior under elevated temperatures were taken into account in the simulation. A step-shaped trial casting was simulated, which demonstrates the ability of the method to simulate the pressure transmission and decline inside the casting as well as the distribution and evolution of the interfacial heat transfer coefficient. Finally, the method was applied to simulate the solidification of an automotive sub-frame component, based on which the squeeze casting process of the component was optimized.

  3. Proton coupled electron transfer and redox-active tyrosine Z in the photosynthetic oxygen-evolving complex.

    PubMed

    Keough, James M; Jenson, David L; Zuniga, Ashley N; Barry, Bridgette A

    2011-07-27

    Proton coupled electron transfer (PCET) reactions play an essential role in many enzymatic processes. In PCET, redox-active tyrosines may be involved as intermediates when the oxidized phenolic side chain deprotonates. Photosystem II (PSII) is an excellent framework for studying PCET reactions, because it contains two redox-active tyrosines, YD and YZ, with different roles in catalysis. One of the redox-active tyrosines, YZ, is essential for oxygen evolution and is rapidly reduced by the manganese-catalytic site. In this report, we investigate the mechanism of YZ PCET in oxygen-evolving PSII. To isolate YZ(•) reactions, but retain the manganese-calcium cluster, low temperatures were used to block the oxidation of the metal cluster, high microwave powers were used to saturate the YD(•) EPR signal, and YZ(•) decay kinetics were measured with EPR spectroscopy. Analysis of the pH and solvent isotope dependence was performed. The rate of YZ(•) decay exhibited a significant solvent isotope effect, and the rate of recombination and the solvent isotope effect were pH independent from pH 5.0 to 7.5. These results are consistent with a rate-limiting, coupled proton electron transfer (CPET) reaction and are contrasted to results obtained for YD(•) decay kinetics at low pH. This effect may be mediated by an extensive hydrogen-bond network around YZ. These experiments imply that PCET reactions distinguish the two PSII redox-active tyrosines.

  4. A photo- and electrochemical investigation of BODIPY-cobaloxime complexes for hydrogen production, coupled with quantum chemical calculations.

    PubMed

    Manton, Jennifer C; Long, Conor; Vos, Johannes G; Pryce, Mary T

    2014-03-21

    Two BODIPY-cobaloxime complexes; [{Co(dmgH)2Cl}{3-[bis-(4-ethyl-3,5-dimethyl-1H-pyrrol-2-yl)-methyl]-pyridine-borondiflouride}] (1a) and [{Co(dmgH)2Cl}{4-[bis-(4-ethyl-3,5-dimethyl-1H-pyrrol-2-yl)-methyl]-pyridine-borondiflouride}] (2a) (BODIPY = boron dipyrromethene), (dmgH = dimethylglyoxime) have been synthesised and studied as model catalytic systems for the generation of hydrogen gas in aqueous media. Under photochemical conditions, neither complex catalysed the reduction of water to hydrogen. However, both complexes showed considerable activity under electrochemical conditions. Turn-over-numbers for hydrogen production of 1.65 × 10(4) and 1.08 × 10(4) were obtained for 1a and 2a respectively following potentiostatic electrolysis at -1.2 V vs. Ag/AgCl after 1 hour. Quantum chemical calculations were performed to provide an explanation for the lack of photochemical activity.

  5. How to identify the most effective control measures based on disease-behavior coupled mechanisms?. Comment on "Coupled disease-behavior dynamics on complex networks: A review" by Z. Wang et al.

    NASA Astrophysics Data System (ADS)

    Sun, Gui-Quan; Jin, Zhen

    2015-12-01

    Modelling infectious diseases on complex networks is a significant tool to understand the transmission of epidemics in human society, and consequently it has commanded increasing attention in the community of mathematicians, physicists, epidemiologists, public health policy-makers and so on [1-4]. Human behavior responses are associated with the emergence of infectious disease, for instance, wearing masks [5], staying away from a thick crowd [6], cutting contacts with infected individuals [7] and receiving a vaccination [8]. However, infectious diseases and human behavior were often modeled as independent systems in the literature, despite the fact that in the real world they are often mutually influential on each other, and hence their coupling exerts significant impacts on disease spread [9,10].

  6. The toluene-Ar complex: S0 and S1 van der Waals modes, changes to methyl rotation, and torsion-van der Waals vibration coupling.

    PubMed

    Gascooke, Jason R; Lawrance, Warren D

    2013-02-28

    The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 ← S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are ∣V3(S1)∣ = 33.4 ± 1.0 cm(-1), ∣V3(S0)∣ = 20.0 ± 1.0 cm(-1), V6(S1) = -10.7 ± 1.0 cm(-1), and V6(S0) = -1.7 ± 1.0 cm(-1). The methyl rotor is also found to couple with van der Waals vibration; specifically, the m(") = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m(") = 1. The coupling constant is determined to be 1.9 cm(-1), which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.

  7. Steric and Electronic Influence on Proton-Coupled Electron-Transfer Reactivity of a Mononuclear Mn(III)-Hydroxo Complex.

    PubMed

    Rice, Derek B; Wijeratne, Gayan B; Burr, Andrew D; Parham, Joshua D; Day, Victor W; Jackson, Timothy A

    2016-08-15

    A mononuclear hydroxomanganese(III) complex was synthesized utilizing the N5 amide-containing ligand 2-[bis(pyridin-2-ylmethyl)]amino-N-2-methyl-quinolin-8-yl-acetamidate (dpaq(2Me) ). This complex is similar to previously reported [Mn(III)(OH)(dpaq(H))](+) [Inorg. Chem. 2014, 53, 7622-7634] but contains a methyl group adjacent to the hydroxo moiety. This α-methylquinoline group in [Mn(III)(OH)(dpaq(2Me))](+) gives rise to a 0.1 Å elongation in the Mn-N(quinoline) distance relative to [Mn(III)(OH)(dpaq(H))](+). Similar bond elongation is observed in the corresponding Mn(II) complex. In MeCN, [Mn(III)(OH)(dpaq(2Me))](+) reacts rapidly with 2,2',6,6'-tetramethylpiperidine-1-ol (TEMPOH) at -35 °C by a concerted proton-electron transfer (CPET) mechanism (second-order rate constant k2 of 3.9(3) M(-1) s(-1)). Using enthalpies and entropies of activation from variable-temperature studies of TEMPOH oxidation by [Mn(III)(OH)(dpaq(2Me))](+) (ΔH(‡) = 5.7(3) kcal(-1) M(-1); ΔS(‡) = -41(1) cal M(-1) K(-1)), it was determined that [Mn(III)(OH)(dpaq(2Me))](+) oxidizes TEMPOH ∼240 times faster than [Mn(III)(OH)(dpaq(H))](+). The [Mn(III)(OH)(dpaq(2Me))](+) complex is also capable of oxidizing the stronger O-H and C-H bonds of 2,4,6-tri-tert-butylphenol and xanthene, respectively. However, for these reactions [Mn(III)(OH)(dpaq(2Me))](+) displays, at best, modest rate enhancement relative to [Mn(III)(OH)(dpaq(H))](+). A combination of density function theory (DFT) and cyclic voltammetry studies establish an increase in the Mn(III)/Mn(II) reduction potential of [Mn(III)(OH)(dpaq(2Me))](+) relative to [Mn(III)(OH)(dpaq(H))](+), which gives rise to a larger driving force for CPET for the former complex. Thus, more favorable thermodynamics for [Mn(III)(OH)(dpaq(2Me))](+) can account for the dramatic increase in rate with TEMPOH. For the more sterically encumbered substrates, DFT computations suggest that this effect is mitigated by unfavorable steric interactions between the

  8. Crystal structure of LGR4-Rspo1 complex: insights into the divergent mechanisms of ligand recognition by leucine-rich repeat G-protein-coupled receptors (LGRs).

    PubMed

    Xu, Jin-Gen; Huang, Chunfeng; Yang, Zhengfeng; Jin, Mengmeng; Fu, Panhan; Zhang, Ni; Luo, Jian; Li, Dali; Liu, Mingyao; Zhou, Yan; Zhu, Yongqun

    2015-01-23

    Leucine-rich repeat G-protein-coupled receptors (LGRs) are a unique class of G-protein-coupled receptors characterized by a large extracellular domain to recognize ligands and regulate many important developmental processes. Among the three groups of LGRs, group B members (LGR4-6) recognize R-spondin family proteins (Rspo1-4) to stimulate Wnt signaling. In this study, we successfully utilized the "hybrid leucine-rich repeat technique," which fused LGR4 with the hagfish VLR protein, to obtain two recombinant human LGR4 proteins, LGR415 and LGR49. We determined the crystal structures of ligand-free LGR415 and the LGR49-Rspo1 complex. LGR4 exhibits a twisted horseshoe-like structure. Rspo1 adopts a flat and β-fold architecture and is bound in the concave surface of LGR4 in the complex through electrostatic and hydrophobic interactions. All the Rspo1-binding residues are conserved in LGR4-6, suggesting that LGR4-6 bind R-spondins through an identical surface. Structural analysis of our LGR4-Rspo1 complex with the previously determined LGR4 and LGR5 structures revealed that the concave surface of LGR4 is the sole binding site for R-spondins, suggesting a one-site binding model of LGR4-6 in ligand recognition. The molecular mechanism of LGR4-6 is distinct from the two-step mechanism of group A receptors LGR1-3 and the multiple-interface binding model of group C receptors LGR7-8, suggesting LGRs utilize the divergent mechanisms for ligand recognition. Our structures, together with previous reports, provide a comprehensive understanding of the ligand recognition by LGRs.

  9. Ab initio and coupled-perturbed density functional theory estimation of zero-field splittings in MnII transition metal complexes.

    PubMed

    Zein, Samir; Neese, Frank

    2008-08-28

    The paper presents a method comparison for the prediction of zero-field splitting (ZFS) parameters in a series of Mn (II) coordination complexes. The test set consists of Mn (II) complexes that are experimentally well-characterized by X-ray diffraction and high-field electron paramagnetic resonance. Their ZFS parameters have been calculated using density functional theory (DFT) as well as complete active space self-consistent field (CASSCF) methods. It is shown that the recently introduced coupled-perturbed spin-orbit coupling (CP-SOC) approach [ Neese, F. J. Chem. Phys. 2007, 127, 164112 ] together with hybrid-DFT functionals leads to a slope of the correlation line (plot of experimental vs calculated D values) that is essentially unity provided that the direct spin-spin interaction is properly included in the treatment. This is different from our previous DFT study on the same series of complexes where a severe overestimation of the D parameter has been found [ Zein, S. ; Duboc, C. ; Lubitz, W. ; Neese, F. Inorg. Chem. 2008, 47, 134 ]. CASSCF methods have been used to evaluate the ZFS in an "ab initio ligand-field" type treatment. The study demonstrates that a substantial part of the relevant physics is lost in such a treatment since only excitations within the manganese d-manifold are accounted for. Thus, a severe underestimation of the D parameter has been found. Because the CASSCF calculations in combination with quasidegenerate perturbation theory treats the SOC to all orders, we have nevertheless verified that second-order perturbation theory is an adequate approximation in the case of the high-spin d (5) configuration.

  10. Switching from antiferromagnetic to ferromagnetic coupling in heptanuclear [M(t)6M(c)](n+) complexes by going from an achiral to a chiral triplesalen ligand.

    PubMed

    Mukherjee, Chandan; Hoeke, Veronika; Stammler, Anja; Bögge, Hartmut; Schnack, Jürgen; Glaser, Thorsten

    2014-07-07

    The chiral triplesalen ligand H6chand(RR) has been used to synthesize the chiral heptanuclear complexes [{(chand(RR))Mn(III)3}2{Fe(II)(CN)6}](ClO4)2 ((RR)[Mn(III)6Fe(II)](ClO4)2) and [{(chand(RR))Fe(III)3}2{Fe(II)(CN)6}](ClO4)2 ((RR)[Fe(III)6Fe(II)](ClO4)2), which have been characterized by single-crystal X-ray diffraction, mass spectrometry, elemental analysis, FT-IR, Mössbauer, and UV-vis spectroscopies, electrochemistry, as well as DC and AC magnetic susceptibility measurements. The half-wave potential of the Fe(III)/Fe(II) couple in (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+) is E1/2 = +0.21 and +0.75 V vs. Fc(+)/Fc, respectively, which (i) corresponds to a strong stabilization of the reduced Fe(II) species compared to the redox couple of free [Fe(II/III)(CN)6](4-/3-) and (ii) indicates a significant difference of the electronic coupling with the {(chand(RR))M(t)}(3+) units (M(t) = Mn(III), Fe(III)). Analysis of the DC magnetic data (μeffvs. T, VTVH) of both complexes by a full-matrix diagonalization of the spin-Hamiltonian including isotropic exchange, zero-field splitting with full consideration of the relative orientation of the D tensors and Zeeman interactions reveals ferromagnetic interactions of JMn-Mn = +0.17 ± 0.02 cm(-1) with DMn = -3.4 ± 0.3 cm(-1) for (RR)[Mn(III)6Fe(II)](2+) and JFe-Fe = +0.235 ± 0.005 cm(-1) with DFe = 0 for (RR)[Fe(III)6Fe(II)](2+). The comparison of the molecular structures of (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+) with those of the heptanuclear complexes [M(t)6M(c)](n+) using the achiral triplesalen ligand (talen(t-Bu2))(6-) reveals significant differences in the ligand folding, smaller C-C bond distances in the central phloroglucinol ring and larger HOMA values. This indicates more aromatic character and less heteroradialene contribution in (RR)[Mn(III)6Fe(II)](2+) and (RR)[Fe(III)6Fe(II)](2+), which explains the switching from antiferromagnetic coupling in [M(t)6M(c)](n+) to ferromagnetic

  11. Inversion of peak elution order prevents uniform time alignment of complex liquid-chromatography coupled to mass spectrometry datasets.

    PubMed

    Mitra, Vikram; Smilde, Age; Hoefsloot, Huub; Suits, Frank; Bischoff, Rainer; Horvatovich, Péter

    2014-12-19

    Retention time alignment is one of the most challenging steps in processing LC-MS datasets of complex proteomics samples acquired within a differential profiling study. A large number of time alignment methods have been developed for accurate pre-processing of such datasets. These methods generally assume that common compounds elute in the same order but they do not test whether this assumption holds. If this assumption is not valid, alignments based on a monotonic retention time function will lose accuracy for peaks that depart from the expected order of the retention time correspondence function. To address this issue, we propose a quality control method that assesses if a pair of complex LC-MS datasets can be aligned with the same alignment performance based on statistical tests before correcting retention time shifts. The algorithm first confirms the presence of an adequate number of common peaks (>∼100 accurately matched peak pairs), then determines if the probability for a conserved elution order of those common peaks is sufficiently high (>0.01) and finally performs retention time alignment of two LC-MS chromatograms. This procedure was applied to LC-MS and LC-MS/MS datasets from two different inter-laboratory proteomics studies showing that a large number of common peaks in chromatograms acquired by different laboratories change elution order with considerable retention time differences.

  12. Fast Photochemical Oxidation of Proteins Coupled to Multidimensional Protein Identification Technology (MudPIT): Expanding Footprinting Strategies to Complex Systems

    NASA Astrophysics Data System (ADS)

    Rinas, Aimee; Jones, Lisa M.

    2015-04-01

    Peptides containing the oxidation products of hydroxyl radical-mediated protein footprinting experiments are typically much less abundant than their unoxidized counterparts. This is inherent to the design of the experiment as excessive oxidation may lead to undesired conformational changes or unfolding of the protein, skewing the results. Thus, as the complexity of the systems studied using this method expands, the detection and identification of these oxidized species can be increasingly difficult with the limitations of data-dependent acquisition (DDA) and one-dimensional chromatography. Here we report the application of multidimensional protein identification technology (MudPIT) in combination with hydroxyl radical footprinting as a method to increase the identification of quantifiable peptides in these experiments. Using this method led to a 37% increase in unique peptide identifications as well as a 70% increase in protein group identifications over one-dimensional data-dependent acquisition on the same samples. Furthermore, we demonstrate the combination of these methods as a means to investigate megadalton complexes.

  13. On the Complex Coupling Between the Production of Ozone and Secondary Organic Aerosol in Polluted Urban Regions

    NASA Astrophysics Data System (ADS)

    Stewart, D. R.; Stockwell, W. R.; Morris, V. R.; Fitzgerald, R. M.

    2016-12-01

    The major photochemical processes that produce ozone and aerosols are coupled together strongly in the polluted urban atmosphere. Aerosols are either directly emitted or formed through the same kind of chemistry that leads to the production of ozone. The aerosols produced through atmospheric chemistry are known as secondary aerosols and they may be composed of inorganic (nitrates, sulfates) or organic compounds. Wind blown dust and soot are two examples of primary aerosols. The component of secondary inorganic aerosols includes compounds such as ammonium nitrate, ammonium bisulfate and ammonium sulfate. Secondary organic aerosols are a very important component of PM with strong implications for health. The formation of secondary organic aerosol is linked with ozone photochemistry through the reactions of volatile organic compounds (VOC). The oxidation of VOC produces radicals that convert nitric oxide to nitrogen dioxide that photolyze to produce ozone. Larger VOC (those with more carbon atoms) undergo a number of oxidation cycles that add oxygen atoms to large organic molecules. The vapor pressure of many of these highly oxidized compounds is sufficiently low that they condense to produce secondary organic aerosols. The Community Multi-scale Air Quality model (CMAQ) and other chemical simulations have been made to quantify the relationship between varying emissions of VOC and NOx and the production of inorganic and secondary organic aerosols. The results from this analysis will be presented.

  14. Interplay of Electronic Cooperativity and Exchange Coupling in Regulating the Reactivity of Diiron(IV)-oxo Complexes towards C-H and O-H Bond Activation.

    PubMed

    Ansari, Azaj; Ansari, Mursaleem; Singha, Asmita; Rajaraman, Gopalan

    2017-07-26

    Activation of inert C-H bonds such as those of methane are extremely challenging for chemists but in nature, the soluble methane monooxygenase (sMMO) enzyme readily oxidizes methane to methanol by using a diiron(IV) species. This has prompted chemists to look for similar model systems. Recently, a (μ-oxo)bis(μ-carboxamido)diiron(IV) ([Fe(IV)2 O(L)2 ](2+) L=N,N-bis-(3',5'-dimethyl-4'-methoxypyridyl-2'-methyl)-N'-acetyl-1,2-diaminoethane) complex has been generated by bulk electrolysis and this species activates inert C-H bonds almost 1000 times faster than mononuclear Fe(IV) =O species and at the same time selectively activates O-H bonds of alcohols. The very high reactivity and selectivity of this species is puzzling and herein we use extensive DFT calculations to shed light on this aspect. We have studied the electronic and spectral features of diiron {Fe(III) -μ(O)-Fe(III) }(+2) (complex I), {Fe(III) -μ(O)-Fe(IV) }(+3) (II), and {Fe(IV) -μ(O)-Fe(IV) }(+4) (III) complexes. Strong antiferromagnetic coupling between the Fe centers leads to spin-coupled S=0, S=3/2, and S=0 ground state for species I-III respectively. The mechanistic study of the C-H and O-H bond activation reveals a multistate reactivity scenario where C-H bond activation is found to occur through the S=4 spin-coupled state corresponding to the high-spin state of individual Fe(IV) centers. The O-H bond activation on the other hand, occurs through the S=2 spin-coupled state corresponding to an intermediate state of individual Fe(IV) centers. Molecular orbital analysis reveals σ-π/π-π channels for the reactivity. The nature of the magnetic exchange interaction is found to be switched during the course of the reaction and this offers lower energy pathways. Significant electronic cooperativity between two metal centers during the course of the reaction has been witnessed and this uncovers the reason behind the efficiency and selectivity observed. The catalyst is found to prudently choose the

  15. Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: theory, implementation, and examples.

    PubMed

    Bravaya, Ksenia B; Zuev, Dmitry; Epifanovsky, Evgeny; Krylov, Anna I

    2013-03-28

    Theory and implementation of complex-scaled variant of equation-of-motion coupled-cluster method for excitation energies with single and double substitutions (EOM-EE-CCSD) is presented. The complex-scaling formalism extends the EOM-EE-CCSD model to resonance states, i.e., excited states that are metastable with respect to electron ejection. The method is applied to Feshbach resonances in atomic systems (He, H(-), and Be). The dependence of the results on one-electron basis set is quantified and analyzed. Energy decomposition and wave function analysis reveal that the origin of the dependence is in electron correlation, which is essential for the lifetime of Feshbach resonances. It is found that one-electron basis should be sufficiently flexible to describe radial and angular electron correlation in a balanced fashion and at different values of the scaling parameter, θ. Standard basis sets that are optimized for not-complex-scaled calculations (θ = 0) are not sufficiently flexible to describe the θ-dependence of the wave functions even when heavily augmented by additional sets.

  16. Insights into dehydrogenative coupling of alcohols and amines catalyzed by a (PNN)-Ru(II) hydride complex: unusual metal-ligand cooperation.

    PubMed

    Zeng, Guixiang; Li, Shuhua

    2011-11-07

    Density functional theory calculations were performed to elucidate the mechanism of dehydrogenative coupling of primary alcohols and amines mediated by a PNN-Ru(II) hydride complex (PNN = (2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine)). A plausible reaction pathway was proposed which contains three stages: (1) The alcohol dehydrogenation reaction to generate the aldehyde and H(2); (2) The aldehyde-amine condensation reaction to form the hemiaminal intermediate; (3) The dehydrogenation process of the hemiaminal intermediate to yield the final amide product with the liberation of H(2). The first and third stages occur via a similar pathway: (a) Proton transfer from the substrate to the PNN ligand; (b) Intramolecular rearrangement of the deprotonated substrate to form an anagostic complex; (c) Hydride transfer from the deprotonated substrate to the Ru center to yield the trans-dihydride intermediate and the aldehyde (or amide); (d) Benzylic proton migration from the PNN ligand to the metal center forming a dihydrogen complex and subsequent H(2) liberation to regenerate the catalyst. In all these steps, the metal-ligand cooperation plays an essential role. In proton transfer steps (a) and (d), the metal-ligand cooperation is achieved through the aromatization/dearomatization processes of the PNN ligand. While in steps (b) and (c), their collaboration are demonstrated by the formation of an anagostic interaction between Ru and the C-H bond and two ionic hydrogen bonds supported by the PNN ligand.

  17. Complex-scaled equation-of-motion coupled-cluster method with single and double substitutions for autoionizing excited states: Theory, implementation, and examples

    SciTech Connect

    Bravaya, Ksenia B.; Zuev, Dmitry; Epifanovsky, Evgeny; Krylov, Anna I.

    2013-03-28

    Theory and implementation of complex-scaled variant of equation-of-motion coupled-cluster method for excitation energies with single and double substitutions (EOM-EE-CCSD) is presented. The complex-scaling formalism extends the EOM-EE-CCSD model to resonance states, i.e., excited states that are metastable with respect to electron ejection. The method is applied to Feshbach resonances in atomic systems (He, H{sup -}, and Be). The dependence of the results on one-electron basis set is quantified and analyzed. Energy decomposition and wave function analysis reveal that the origin of the dependence is in electron correlation, which is essential for the lifetime of Feshbach resonances. It is found that one-electron basis should be sufficiently flexible to describe radial and angular electron correlation in a balanced fashion and at different values of the scaling parameter, {theta}. Standard basis sets that are optimized for not-complex-scaled calculations ({theta} = 0) are not sufficiently flexible to describe the {theta}-dependence of the wave functions even when heavily augmented by additional sets.

  18. Dissociative electron attachment to the H2O molecule. II. Nuclear dynamics on coupled electronic surfaces within the local complex potential model

    NASA Astrophysics Data System (ADS)

    Haxton, Daniel J.; Rescigno, T. N.; McCurdy, C. W.

    2007-01-01

    We report the results of a first-principles study of dissociative electron attachment to H2O . The cross sections were obtained from nuclear dynamics calculations carried out in full dimensionality within the local complex potential model by using the multiconfiguration time-dependent Hartree method. The calculations employ our previously obtained global, complex-valued, potential-energy surfaces for the three ( B12 , A12 , and B22 ) electronic Feshbach resonances involved in this process. These three metastable states of H2O- undergo several degeneracies, and we incorporate both the Renner-Teller coupling between the B12 and A12 states as well as the conical intersection between the A12 and B22 states into our treatment. The nuclear dynamics are inherently multidimensional and involve branching between different final product arrangements as well as extensive excitation of the diatomic fragment. Our results successfully mirror the qualitative features of the major fragment channels observed, but are less successful in reproducing the available results for some of the minor channels. We comment on the applicability of the local complex potential model to such a complicated resonant system.

  19. Speciation analysis of inorganic tin by on-column complexation ion chromatography with inductively coupled plasma mass spectrometry and electrospray mass spectrometry.

    PubMed

    Huang, Li; Yang, Die; Guo, Xiangquan; Chen, Zuliang

    2014-11-14

    Inductively coupled plasma-mass spectrometry (ICP-MS) and electrospray mass spectrometry (ESI-MS) were used as complementary methods to identify Sn-pentaacetic acid (DTPA) complex formation. ESI-MS was used to initially confirm the formation of [Sn(DTPA)](3-) and [Sn(DTPA)](1-) and their MS spectra suggest these tin complexes were stable in solution. On-column complexation of tin with DTPA and the separation of [Sn(DTPA)](3-) and [Sn(DTPA)](1-) was performed on anion-exchange chromatography with an mobile phase containing 20mM NH4NO3 and 3mM DTPA at pH 6.0, and the subsequent detection of [Sn(DTPA)](3-) and [Sn(DTPA)](1-) was achieved by ICP-MS. Linear plots were obtained in a concentration range of 1.0-1000 μg L(-1) with detection limits ranging from 0.1 to 0.3 μg L(-1). The developed procedure allows the simultaneous determination of [Sn(DTPA)](3-) and [Sn(DTPA)](1-) in less than 5 min with a RSD between 2.1 and 2.7%. The recoveries of [Sn(DTPA)](3-) and [Sn(DTPA)](1-) were found to be 96.8 and 99.4%, respectively, when the sample was spiked with 20 μg L(-1) standard. Finally, the proposed procedure was used for the determination of tin species in contaminated water.

  20. Advances in ultra-high performance liquid chromatography coupled to tandem mass spectrometry for sensitive detection of several food allergens in complex and processed foodstuffs.

    PubMed

    Planque, M; Arnould, T; Dieu, M; Delahaut, P; Renard, P; Gillard, N

    2016-09-16

    Sensitive detection of food allergens is affected by food processing and foodstuff complexity. It is therefore a challenge to detect cross-contamination in food production that could endanger an allergic customer's life. Here we used ultra-high performance liquid chromatography coupled to tandem mass spectrometry for simultaneous detection of traces of milk (casein, whey protein), egg (yolk, white), soybean, and peanut allergens in different complex and/or heat-processed foodstuffs. The method is based on a single protocol (extraction, trypsin digestion, and purification) applicable to the different tested foodstuffs: chocolate, ice cream, tomato sauce, and processed cookies. The determined limits of quantitation, expressed in total milk, egg, peanut, or soy proteins (and not soluble proteins) per kilogram of food, are: 0.5mg/kg for milk (detection of caseins), 5mg/kg for milk (detection of whey), 2.5mg/kg for peanut, 5mg/kg for soy, 3.4mg/kg for egg (detection of egg white), and 30.8mg/kg for egg (detection of egg yolk). The main advantage is the ability of the method to detect four major food allergens simultaneously in processed and complex matrices with very high sensitivity and specificity.

  1. C-C and C-N Couplings Following Hydride Addition on Isocyanide Cyclopolyenyl Dimolybdenum Complexes to Give Tethered Aldimine and Aminocarbene Derivatives.

    PubMed

    Alvarez, Belén; Alvarez, M Angeles; García, M Esther; García-Vivó, Daniel; Ruiz, Miguel A

    2017-10-09

    Reaction of [Mo2 Cp2 (μ-κ(1) :κ(1) ,η(6) -PMes*)(CO)2 ] with S or Se followed by protonation with [H(OEt2 )2 ](BAr'4 ) gave the cationic derivatives [Mo2 Cp2 {μ-κ(2)P,E :κ(1)P ,η(5) -EP(C6 H3 tBu3 )}(CNR)(CO)2 ](BAr'4 ) (E=S; R=tBu, iPr, Ph, 4-C6 H4 OMe, Xyl; or E=Se; R=tBu; Ar'=3,5-C6 H3 (CF3 )2 ). Reaction of the latter with K[BHsBu3 ] yielded the aldimine complexes [Mo2 Cp2 {μ-κ(2)P,E :κ(2)P,N ,η(4) -SP(C6 H3 tBu3 (CHNR))}(CO)2 ] and their aminocarbene isomers [Mo2 Cp2 {μ-κ(2)P,E :κ(2)P,C ,η(4) -SP(C6 H3 tBu3 (NRCH))}(CO)2 ] (R ≠ Xyl), following C-C and C-N couplings, respectively. Monitoring of these reactions revealed that the initial H(-) attack takes place at a Cp ligand to give cyclopentadiene intermediates [Mo2 Cp{μ-κ(2)P,S :κ(1)P ,η(5) -SP(C6 H3 tBu3 )}(η(4) -C5 H6 )(CNR)(CO)2 ], which then undergo C-H oxidative addition to give the hydride isomers [Mo2 Cp2 {μ-κ(2)P,S :κ(1)P ,η(3) -SP(C6 H3 tBu3 )}(H)(CNR)(CO)2 ]. In turn, the latter rearrange to give the aldimine and aminocarbene complexes. DFT calculations revealed that the hydride intermediates first undergo migratory insertion of the isocyanide ligand into the Mo-H bond to give unobservable formimidoyl intermediates, which then evolve either by nucleophilic attack of the N atom on the C6 ring (C-N coupling) or by migratory insertion of the formimidoyl ligand into the C6 ring (C-C coupling). Our data suggest that increasing the size of the substituent R at the isocyanide ligand destabilizes the aldimine isomer to a greater extent, thus favoring formation of the aminocarbene complex. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Methanol-Triggered Vapochromism Coupled with Solid-State Spin Switching in a Nickel(II)-Quinonoid Complex.

    PubMed

    Kar, Paramita; Yoshida, Masaki; Shigeta, Yasuhiro; Usui, Akane; Kobayashi, Atsushi; Minamidate, Takaaki; Matsunaga, Noriaki; Kato, Masako

    2017-02-20

    A highly methanol-selective vapochromic response has been realized in a Ni(II) -quinonoid complex, [Ni(HL(Me) )2 ] (H2 L(Me) =4-methylamino-6-methyliminio-3-oxocyclohexa-1,4-dien-1-olate) which exhibits a reversible structural transformation including a coordination geometrical change between the square-planar and octahedral structure by the selective uptake of methanol vapor. This was accompanied by a remarkable color change between purple and orange, as well as temperature-robust spin-state switching in the solid state under ambient conditions. It is remarkable that the properties are derived by the fine structural modification of the quinonoid ligand such as methyl or ethyl analogues. Such a system has high potential for applications in memory devices as well as chemical sensors and smart responsive materials.

  3. Single-molecule magnet behaviour in a tetrathiafulvalene-based electroactive antiferromagnetically coupled dinuclear dysprosium(III) complex.

    PubMed

    Pointillart, Fabrice; Le Gal, Yann; Golhen, Stéphane; Cador, Olivier; Ouahab, Lahcène

    2011-09-05

    The reactions between the [Ln(tta)(3)]·2H(2)O precursors (tta(-)=2-thenoyltrifluoroacetonate anion) and the tetrathiafulvalene-3-pyridine-N-oxide ligands (L(1)) lead to dinuclear complexes of formula [{Ln(tta)(3)(L(1))}(2)]·xCH(2)Cl(2) (x=0.5 for Ln=Dy(III) (1) and x=0 for Ln=Gd(III) (2)). The crystal structure reveals that two {Ln(tta)(3)} moieties are bridged by two donors through the nitroxide groups. The Dy(III) centre adopts a distorted square antiprismatic oxygenated polyhedron structure. The antiferromagnetic nature of the exchange interaction between the two Dy(III) ions has been determined by two methods: 1) an empirical method using the [Dy(hfac)(3)(L(2))(2)] mononuclear complex as a model (3) (hfac(-)=1,1,1,5,5,5-hexafluoroacetylacetonate anion, L(2)=tetrathiafulvaleneamido-2-pyridine-N-oxide ligand), and 2) assuming an Ising model for the Dy(III) ion giving an exchange energy of -2.30 cm(-1), g=19.2 in the temperature range of 2-10 K. The antiferromagnetic interactions have been confirmed by a quantitative determination of J for the isotropic Gd(III) derivative (J=-0.031 cm(-1), g=2.003). Compound 1 displays a slow magnetisation relaxation without applied external magnetic fields. Alternating current susceptibility shows a thermally activated behaviour with pre-exponential factors of 5.48(4)×10(-7) s and an energy barrier of 87(1) K. The application of an external field of 1.6 kOe compensates the antiferromagnetic interactions and opens a new quantum tunnelling path. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Coupling Gd-DTPA with a bispecific, recombinant protein anti-EGFR-iRGD complex improves tumor targeting in MRI

    PubMed Central

    XIN, XIAOYAN; SHA, HUIZI; SHEN, JINGTAO; ZHANG, BING; ZHU, BIN; LIU, BAORUI

    2016-01-01

    Recombinant anti-epidermal growth factor receptor-internalizing arginine-glycine-aspartic acid (anti-EGFR single-domain antibody fused with iRGD peptide) protein efficiently targets the EGFR extracellular domain and integrin αvβ/β5, and shows a high penetration into cells. Thus, this protein may improve penetration of conjugated drugs into the deep zone of gastric cancer multicellular 3D spheroids. In the present study, a novel tumor-targeting contrast agent for magnetic resonance imaging (MRI) was developed, by coupling gadolinium-diethylene triamine pentaacetate (Gd-DTPA) with the bispecific recombinant anti-EGFR-iRGD protein. The anti-EGFR-iRGD protein was extracted from Escherichia coli and Gd was loaded onto the recombinant protein by chelation using DTPA anhydride. Single-targeting agent anti-EGFR-DTPA-Gd, which served as the control, was also prepared. The results of the present study showed that anti-EGFR-iRGD-DTPA-Gd exhibited no significant cyto toxicity to human gastric carcinoma cells (BGC-823) under the experimental conditions used. Compared with a conventional contrast agent (Magnevist), anti-EGFR-iRGD-DTPA-Gd showed higher T1 relaxivity (10.157/mM/sec at 3T) and better tumor-targeting ability. In addition, the signal intensity and the area under curve for the enhanced signal time in tumor, in vivo, were stronger than Gd-DTPA alone or the anti-EGFR-Gd control. Thus, Gd-labelled anti-EGFR-iRGD has potential as a tumor-targeting contrast agent for improved MRI. PMID:27035336

  5. Multicomponent linchpin couplings. Reaction of dithiane anions with terminal epoxides, epichlorohydrin, and vinyl epoxides: efficient, rapid, and stereocontrolled assembly of advanced fragments for complex molecule synthesis.

    PubMed

    Smith, Amos B; Pitram, Suresh M; Boldi, Armen M; Gaunt, Matthew J; Sfouggatakis, Chris; Moser, William H

    2003-11-26

    The development, application, and advantages of a one-flask multicomponent dithiane linchpin coupling protocol, over the more conventional stepwise addition of dithiane anions to electrophiles leading to the rapid, efficient, and stereocontrolled assembly of highly functionalized intermediates for complex molecule synthesis, are described. Competent electrophiles include terminal epoxides, epichlorohydrin, and vinyl epoxides. High chemoselectivity can be achieved with epichlorohydrin and vinyl epoxides. For vinyl epoxides, the steric nature of the dithiane anion is critical; sterically unencumbered dithiane anions afford S(N)2 adducts, whereas encumbered anions lead primarily to SN2' adducts. Mechanistic studies demonstrate that the SN2' process occurs via syn addition to the vinyl epoxide. Integration of the multicomponent tactic with epichlorohydrin and vinyl epoxides permits the higher-order union of four and five components.

  6. A fully-coupled upwind discontinuous Galerkin method for incompressible porous media flows: High-order computations of viscous fingering instabilities in complex geometry

    NASA Astrophysics Data System (ADS)

    Scovazzi, G.; Huang, H.; Collis, S. S.; Yin, J.

    2013-11-01

    We present a new approach to the simulation of viscous fingering instabilities in incompressible, miscible displacement flows in porous media. In the past, high resolution computational simulations of viscous fingering instabilities have always been performed using high-order finite difference or Fourier-spectral methods which do not posses the flexibility to compute very complex subsurface geometries. Our approach, instead, by means of a fully-coupled nonlinear implementation of the discontinuous Galerkin method, possesses a fundamental differentiating feature, in that it maintains high-order accuracy on fully unstructured meshes. In addition, the proposed method shows very low sensitivity to mesh orientation, in contrast with classical finite volume approximation used in porous media flow simulations. The robustness and accuracy of the method are demonstrated in a number of challenging computational problems.

  7. Proton-Coupled Electron Transfer During the S-State Transitions of the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Amin, Muhamed; Vogt, Leslie; Szejgis, Witold; Vassiliev, Serguei; Brudvig, Gary W; Bruce, Doug; Gunner, M R

    2015-06-18

    The oxygen-evolving complex (OEC) of photosystem II (PSII) is a unique Mn4O5Ca cluster that catalyzes water oxidation via four photoactivated electron transfer steps. As the protein influence on the redox and protonation chemistry of the OEC remains an open question, we present a classical valence model of the OEC that allows the redox state of each Mn and the protonation state of bridging μ-oxos and terminal waters to remain in equilibrium with the PSII protein throughout the redox cycle. We find that the last bridging oxygen loses its proton during the transition from S0 to S1. Two possible S2 states are found depending on the OEC geometry: S2 has Mn4(IV) with a proton lost from a terminal water (W1) trapped by the nearby D1-D61 if O5 is closer to Mn4, or Mn1(IV), with partial deprotonation of D1-H337 and D1-E329 if O5 is closer to Mn1. In S3, the OEC is Mn4(IV) with W2 deprotonated. The estimated OEC Em's range from +0.7 to +1.3 V, enabling oxidation by P680(+), the primary electron donor in PSII. In chloride-depleted PSII, the proton release increases during the S1 to S2 transition, leaving the OEC unable to properly advance through the water-splitting cycle.

  8. Coupled binding-bending-folding: The complex conformational dynamics of protein-DNA binding studied by atomistic molecular dynamics simulations.

    PubMed

    van der Vaart, Arjan

    2015-05-01

    Protein-DNA binding often involves dramatic conformational changes such as protein folding and DNA bending. While thermodynamic aspects of this behavior are understood, and its biological function is often known, the mechanism by which the conformational changes occur is generally unclear. By providing detailed structural and energetic data, molecular dynamics simulations have been helpful in elucidating and rationalizing protein-DNA binding. This review will summarize recent atomistic molecular dynamics simulations of the conformational dynamics of DNA and protein-DNA binding. A brief overview of recent developments in DNA force fields is given as well. Simulations have been crucial in rationalizing the intrinsic flexibility of DNA, and have been instrumental in identifying the sequence of binding events, the triggers for the conformational motion, and the mechanism of binding for a number of important DNA-binding proteins. Molecular dynamics simulations are an important tool for understanding the complex binding behavior of DNA-binding proteins. With recent advances in force fields and rapid increases in simulation time scales, simulations will become even more important for future studies. This article is part of a Special Issue entitled Recent developments of molecular dynamics. Copyright © 2014. Published by Elsevier B.V.

  9. Electronic Structure and Bonding in Iron(II) and Iron(I) Complexes Bearing Bisphosphine Ligands of Relevance to Iron-Catalyzed C–C Cross-Coupling

    PubMed Central

    2015-01-01

    Chelating phosphines are effective additives and supporting ligands for a wide array of iron-catalyzed cross-coupling reactions. While recent studies have begun to unravel the nature of the in situ-formed iron species in several of these reactions, including the identification of the active iron species, insight into the origin of the differential effectiveness of bisphosphine ligands in catalysis as a function of their backbone and peripheral steric structures remains elusive. Herein, we report a spectroscopic and computational investigation of well-defined FeCl2(bisphosphine) complexes (bisphosphine = SciOPP, dpbz, tBudppe, or Xantphos) and known iron(I) variants to systematically discern the relative effects of bisphosphine backbone character and steric substitution on the overall electronic structure and bonding within their iron complexes across oxidation states implicated to be relevant in catalysis. Magnetic circular dichroism (MCD) and density functional theory (DFT) studies demonstrate that common o-phenylene and saturated ethyl backbone motifs result in small but non-negligible perturbations to 10Dq(Td) and iron–bisphosphine bonding character at the iron(II) level within isostructural tetrahedra as well as in five-coordinate iron(I) complexes FeCl(dpbz)2 and FeCl(dppe)2. Notably, coordination of Xantphos to FeCl2 results in a ligand field significantly reduced relative to those of its iron(II) partners, where a large bite angle and consequent reduced iron–phosphorus Mayer bond orders (MBOs) could play a role in fostering the unique ability of Xantphos to be an effective additive in Kumada and Suzuki–Miyaura alkyl–alkyl cross-couplings. Furthermore, it has been found that the peripheral steric bulk of the SciOPP ligand does little to perturb the electronic structure of FeCl2(SciOPP) relative to that of the analogous FeCl2(dpbz) complex, potentially suggesting that differences in the steric properties of these ligands might be more important in

  10. Mössbauer and DFT study of the ferromagnetically coupled diiron(IV) precursor to a complex with an Fe(IV)(2)O(2) diamond core.

    PubMed

    Martinho, Marlène; Xue, Genqiang; Fiedler, Adam T; Que, Lawrence; Bominaar, Emile L; Münck, Eckard

    2009-04-29

    Recently, we reported the reaction of the (mu-oxo)diiron(III) complex 1 ([Fe(III)(2)(mu-O)(mu-O(2)H(3))(L)(2)](3+), L = tris(3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) with 1 equiv of H(2)O(2) to yield a diiron(IV) intermediate, 2 (Xue, G.; Fiedler, A. T.; Martinho, M.; Munck, E.; Que, L., Jr. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 20615-20). Upon treatment with HClO(4), complex 2 converted to a species with an Fe(IV)(2)(mu-O)(2) diamond core that serves as the only synthetic model to date for the diiron(IV) core proposed for intermediate Q of soluble methane monooxygenase. Here we report detailed Mossbauer and density functional theory (DFT) studies of 2. The Mossbauer studies reveal that 2 has distinct Fe(IV) sites, a and b. Studies in applied magnetic fields show that the spins of sites a and b (S(a) = S(b) = 1) are ferromagnetically coupled to yield a ground multiplet with S = 2. Analysis of the applied field spectra of the exchange-coupled system yields for site b a set of parameters that matches those obtained for the mononuclear [LFe(IV)(O)(NCMe)](2+) complex, showing that site b (labeled Fe(O)) has a terminal oxo group. Using the zero-field splitting parameters of [LFe(IV)(O)(NCMe)](2+) for our analysis of 2, we obtained parameters for site a that closely resemble those reported for the nonoxo Fe(IV) complex [(beta-BPMCN)Fe(IV)(OH)(OO(t)Bu)](2+), suggesting that a (labeled Fe(OH)) coordinates a hydroxo group. A DFT optimization performed on 2 yielded an Fe-Fe distance of 3.39 A and an Fe-(mu-O)-Fe angle of 131 degrees , in good agreement with the results of our previous EXAFS study. The DFT calculations reproduce the Mossbauer parameters (A-tensors, electric field gradient, and isomer shift) of 2 quite well, including the observation that the largest components of the electric field gradients of Fe(O) and Fe(OH) are perpendicular. The ferromagnetic behavior of 2 seems puzzling given that the Fe-(mu-O)-Fe angle is large but can be explained by noting

  11. Mössbauer and DFT Study of the Ferromagnetically Coupled Diiron(IV) Precursor to a Complex with an FeIV2O2 Diamond Core

    PubMed Central

    Martinho, Marlène; Xue, Genqiang; Fiedler, Adam T.; Que, Lawrence; Bominaar, Emile L.; Münck, Eckard

    2009-01-01

    Recently we reported the reaction of the (μ-oxo)diiron(III) complex 1 ([FeIII2(μ-O)(μ-O2H3)(L)2]3+, L = tris(3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) with 1 equivalent of H2O2 to yield a diiron(IV) intermediate, 2 (Xue, Fiedler, Martinho, Münck, and Que, Proc. Natl. Acad. Sci. U.S.A.2008, 105, 20615-20). Upon treatment with HClO4 complex 2 converted to a species with an FeIV2(μ-O)2 diamond core that serves as the only synthetic model to date for the diiron(IV) core proposed for intermediate Q of soluble methane monooxygenase. Here we report detailed Mössbauer and density functional theory (DFT) studies of 2. The Mössbauer studies reveal that 2 has distinct FeIV sites, a and b. Studies in applied magnetic fields show that the spins of sites a and b (Sa = Sb = 1) are ferromagnetically coupled to yield a ground multiplet with S = 2. Analysis of the applied field spectra of the exchange-coupled system yields for site b a set of parameters that matches those obtained for the mononuclear [LFeIV(O)(NCMe)]2+ complex, showing that site b (labeled FeO) has a terminal oxo group. Using the zero-field splitting parameters of [LFeIV(O)(NCMe)]2+ for our analysis of 2, we obtained parameters for site a that closely resemble those reported for the non-oxo FeIV complex [(β-BPMCN)FeIV(OH)(OOtBu)]2+, suggesting that a (labeled FeOH) coordinates a hydroxo group. A DFT optimization performed on 2 yielded an Fe-Fe distance of 3.39 Å and an Fe-(μ-O)-Fe angle of 131 degrees, in good agreement with the results of our previous EXAFS study. The DFT calculations reproduce the Mössbauer parameters (A-tensors, electric field gradient and isomer shift) of 2 quite well, including the observation that the largest components of the electric field gradients of FeO and FeOH are perpendicular. The ferromagnetic behavior of 2 is puzzling given that the Fe-(μ-O)-Fe angle is large but can be explained by noting that the orbital structures of FeO and FeOH are such that the unpaired

  12. Diazotization-coupling reaction-based selective determination of nitrite in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy.

    PubMed

    Zhang, Kaige; Hu, Yuling; Li, Gongke

    2013-11-15

    A simple, rapid and selective method based on diazotization-coupling reaction for determination of nitrite ion in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was developed. Based on diazotization-coupling reaction, nitrite was transformed into azo dye, which has strong SHINERS activity. Subsequently the concentration of nitrite ion can be determined indirectly from the SHINERS of azo dye. The SHINERS active substrate was composed of gold nanoparticle as core with an ultrathin silica shell having pinhole on the surface. Various factors that influence reaction and SHINERS intensity were investigated. Under the optimal conditions, the linearity was observed in the range of 0.5-6.0 mg L(-1) with good correlation coefficient (r(2)>0.9793). The relative standard deviations (RSDs) for five replicate measurements were less than 14.5%. The limit of detections of the method (S/N=3) were 0.07, 0.08 and 0.10 mg L(-1) at 1137, 1395 and 1432 cm(-1), respectively, without sample preconcentration. The selectivity of the proposed method was also tested. The performance of SHINERS to determine the concentration of nitrite in food, biological and environmental samples was evaluated. The results indicate that SHINERS shows great potential as a useful analytical tool for trace analysis of nitrite in real samples. This proposed method provides a practical protocol for determination of compounds with weak Raman response, and can be expanded for the indirect detection of iodate ion, phenols and aromatic amines.

  13. Effects of a nearby Mn delta layer on the optical properties of an InGaAs/GaAs quantum well

    SciTech Connect

    Balanta, M. A. G. Brasil, M. J. S. P.; Iikawa, F.; Brum, J. A.; Mendes, Udson C.; Danilov, Yu. A.; Dorokhin, M. V.; Vikhrova, Olga V.; Zvonkov, Boris N.

    2014-11-28

    We investigated the effects of nearby Mn ions on the confined states of a InGaAs/GaAs quantum well through circularly polarized and magneto-optical measurements. The addition of a Mn delta-doping layer at the barrier close to the well gives rise to surprisingly narrow absorption peaks in the photoluminescence excitation spectra. The peaks become increasingly stronger for decreasing spacer-layer thicknesses between the quantum well and the Mn layer. Most of the peaks were identified based on self-consistent calculations; however, we observed additional peaks that cannot be identified with quantum well transitions, which origin we attribute to an enhanced exciton-phonon coupling. Finally, we discuss possible effects related to the exciton magneto-polaron complex in the reinforcement of the photoluminescence excitation peaks.

  14. Luminescence dynamics and {sup 13}C NMR characteristics of dinuclear complexes exhibiting coupled lanthanide(III) cation pairs

    SciTech Connect

    Matthews, K.D.; Bailey-Folkes, S.A.; Kahwa, I.A.

    1992-08-20

    Luminescence and cross-polarization magic angle spinning (CP-MAS) {sup 13}C NMR properties of lanthanide dinuclear macrocyclic complexes of a compartmental Schiff base chelate (1) derived from the condensation of 2,6-diformyl-p-cresol and 3,6-dioxa-1,8-octanediamine are reported. The Schiff base chromophore in 1 is a strong light absorber and an efficient sensitizer for intense Tb{sup 3+}({sup 5}D{sub 4}) and Eu{sup 3+}({sup 5}D{sub 0})(T < 110 K ) emission which does not exhibit self-quenching effects. Emission from Tb{sup 3+} is sensitized by the ligand singlet state; in striking contrast, Eu{sup 3+} emission is sensitized by the triplet state and reveals an unusual nonradiative quenching process at T > 110 K with a thermal barrier of {approx} 2300 cm{sup {minus}1}. Weak emission is observed from Dy{sup 3+}({sup 4}F{sub 9/2}), Sm{sup 3+}({sup 4}G{sub 5/2}), and Pr{sup 3+}({sup 1}D{sub 2}) diluted in Gd{sup 3+} (i.e., from Gd{sup 3+}-Ln{sup 3+} heteropairs, Ln = Pr, Sm, Dy). Intramolecular metal-metal (Ln-Ln = 4 {Angstrom}) interactions account for the greatly quenched emission from Sm{sup 3+}-Sm{sup 3+} and Dy{sup 3+}-Dy{sup 3+} homopairs compared to Gd{sup 3+}-Ln heteropairs (Ln = Sm, Dy). Gd{sup 3+}-Ln{sup 3+} emission lifetimes at 77 K are 1610 (Tb{sup 3+}), 890 (Eu{sup 3+}), 14 (Dy{sup 3+}) and {approx} 13 {mu}s (Sm{sup 3+}). Nonradiative relaxation processes at 77 K in dilute Ln{sup 3+}:Gd{sub 2}1(NO{sub 3}){sub 4}{center_dot}H{sub 2}O, being temperature independent for Sm{sup 3+} and Eu{sup 3+} but temperature dependent for Tb{sup 3+}, follow the energy gap law with {alpha} {approx} - 10{sup {minus}3} cm and B {approx} 2 x 10{sup 8} s{sup {minus}1}. CP-MAS data show paramagnetic broadening of {sup 13}C resonances which increases with the magnetic moment of Ln{sup 3+}. Surprisingly, no significant shifts in resonance positions corresponding to the changing nature of paramagnetic Ln{sup 3+} ions are observed. 43 refs., 8 figs., 2 tabs.

  15. Coupling fast all-season soil strength land surface model with weather research and forecasting model to assess low-level icing in complex terrain

    NASA Astrophysics Data System (ADS)

    Sines, Taleena R.

    Icing poses as a severe hazard to aircraft safety with financial resources and even human lives hanging in the balance when the decision to ground a flight must be made. When analyzing the effects of ice on aviation, a chief cause for danger is the disruption of smooth airflow, which increases the drag force on the aircraft therefore decreasing its ability to create lift. The Weather Research and Forecast (WRF) model Advanced Research WRF (WRF-ARW) is a collaboratively created, flexible model designed to run on distributed computing systems for a variety of applications including forecasting research, parameterization research, and real-time numerical weather prediction. Land-surface models, one of the physics options available in the WRF-ARW, output surface heat and moisture flux given radiation, precipitation, and surface properties such as soil type. The Fast All-Season Soil STrength (FASST) land-surface model was developed by the U.S. Army ERDC-CRREL in Hanover, New Hampshire. Designed to use both meteorological and terrain data, the model calculates heat and moisture within the surface layer as well as the exchange of these parameters between the soil, surface elements (such as snow and vegetation), and atmosphere. Focusing on the Presidential Mountain Range of New Hampshire under the NASA Experimental Program to Stimulate Competitive Research (EPSCoR) Icing Assessments in Cold and Alpine Environments project, one of the main goals is to create a customized, high resolution model to predict and assess ice accretion in complex terrain. The purpose of this research is to couple the FASST land-surface model with the WRF to improve icing forecasts in complex terrain. Coupling FASST with the WRF-ARW may improve icing forecasts because of its sophisticated approach to handling processes such as meltwater, freezing, thawing, and others that would affect the water and energy budget and in turn affect icing forecasts. Several transformations had to take place in order

  16. The Cockayne syndrome B protein, involved in transcription-coupled DNA repair, resides in an RNA polymerase II-containing complex.

    PubMed Central

    van Gool, A J; Citterio, E; Rademakers, S; van Os, R; Vermeulen, W; Constantinou, A; Egly, J M; Bootsma, D; Hoeijmakers, J H

    1997-01-01

    Transcription-coupled repair (TCR), a subpathway of nucleotide excision repair (NER) defective in Cockayne syndrome A and B (CSA and CSB), is responsible for the preferential removal of DNA lesions from the transcribed strand of active genes, permitting rapid resumption of blocked transcription. Here we demonstrate by microinjection of antibodies against CSB and CSA gene products into living primary fibroblasts, that both proteins are required for TCR and for recovery of RNA synthesis after UV damage in vivo but not for basal transcription itself. Furthermore, immunodepletion showed that CSB is not required for in vitro NER or transcription. Its central role in TCR suggests that CSB interacts with other repair and transcription proteins. Gel filtration of repair- and transcription-competent whole cell extracts provided evidence that CSB and CSA are part of large complexes of different sizes. Unexpectedly, there was no detectable association of CSB with several candidate NER and transcription proteins. However, a minor but significant portion (10-15%) of RNA polymerase II was found to be tightly associated with CSB. We conclude that within cell-free extracts, CSB is not stably associated with the majority of core NER or transcription components, but is part of a distinct complex involving RNA polymerase II. These findings suggest that CSB is implicated in, but not essential for, transcription, and support the idea that Cockayne syndrome is due to a combined repair and transcription deficiency. PMID:9312053

  17. Synthesis of zwitterionic palladium complexes and their application as catalysts in cross-coupling reactions of aryl, heteroaryl and benzyl bromides with organoboron reagents in neat water.

    PubMed

    Ramakrishna, V; Dastagiri Reddy, N

    2017-07-04

    N-(3-Chloro-2-quinoxalinyl)-N'-arylimidazolium salts (aryl = 2,6-diisopropylphenyl [HL1Cl]Cl, aryl = mesityl [HL2Cl]Cl) have been synthesized by treating 2,3-dichloroquinoxaline with the corresponding N'-arylimidazole in neat water. Facile reactions of these imidazolium salts with Pd(PPh3)4 and Pd2(dba)3/PPh3 (dba = dibenzyledene acetone) at 50 °C have afforded zwitterionic palladium(ii) complexes [Pd(HL1)(PPh3)Cl2] (I) and [Pd(HL2)(PPh3)Cl2] (II) in excellent yields. I and II have been tested for their ability to catalyze Suzuki-Miyaura cross coupling (SMC) reactions in neat water/K2CO3 and are found to be highly active for carrying out these reactions between aryl bromides and organoboron reagents. Furthermore, the scope of the catalyst I was also examined by employing (hetero)aryl bromides, hydrophilic aryl bromides, benzyl bromides and various organoboron reagents. More than 80 aryl/benzyl bromide-arylboronic acid combinations were screened in neat water/K2CO3 and it was found that I was a versatile catalyst, which produced biaryls/diarylmethanes in excellent yields. A TON of 82 000 was achieved by using I. Studies on the mechanism have also been carried out to investigate the involvement of carbene complexes in the catalytic path. Poison tests and a two-phase test were also conducted and the results are reported.

  18. Complex mechanism of the gas phase reaction between formic acid and hydroxyl radical. Proton coupled electron transfer versus radical hydrogen abstraction mechanisms.

    PubMed

    Anglada, Josep M

    2004-08-11

    The gas phase reaction between formic acid and hydroxyl radical has been investigated with high level quantum mechanical calculations using DFT-B3LYP, MP2, CASSCF, QCISD, and CCSD(T) theoretical approaches in connection with the 6-311+G(2df,2p) and aug-cc-pVTZ basis sets. The reaction has a very complex mechanism involving several elementary processes, which begin with the formation of a reactant complex before the hydrogen abstraction by hydroxyl radical. The results obtained in this investigation explain the unexpected experimental fact that hydroxyl radical extracts predominantly the acidic hydrogen of formic acid. This is due to a mechanism involving a proton coupled electron-transfer process. The calculations show also that the abstraction of formyl hydrogen has an increased contribution at higher temperatures, which is due to a conventional hydrogen abstraction radical type mechanism. The overall rate constant computed at 298 K is 6.24 x 10(-13) cm3 molecules(-1) s(-1), and compares quite well with the range from 3.2 +/- 1 to 4.9 +/- 1.2 x 10(-13) cm3 molecules(-1) s(-1), reported experimentally.

  19. CRISPR-Cas type I-A Cascade complex couples viral infection surveillance to host transcriptional regulation in the dependence of Csa3b

    PubMed Central

    He, Fei; Vestergaard, Gisle; Peng, Wenfang; She, Qunxin

    2017-01-01

    Abstract CRISPR-Cas (clustered regularly interspaced short palindromic repeats and the associated genes) constitute adaptive immune systems in bacteria and archaea and they provide sequence specific immunity against foreign nucleic acids. CRISPR-Cas systems are activated by viral infection. However, little is known about how CRISPR-Cas systems are activated in response to viral infection or how their expression is controlled in the absence of viral infection. Here, we demonstrate that both the transcriptional regulator Csa3b, and the type I-A interference complex Cascade, are required to transcriptionally repress the interference gene cassette in the archaeon Sulfolobus. Csa3b binds to two palindromic repeat sites in the promoter region of the cassette and facilitates binding of the Cascade to the promoter region. Upon viral infection, loading of Cascade complexes onto crRNA-matching protospacers leads to relief of the transcriptional repression. Our data demonstrate a mechanism coupling CRISPR-Cas surveillance of protospacers to transcriptional regulation of the interference gene cassette thereby allowing a fast response to viral infection. PMID:27980065

  20. Enhanced fluorescence sensitivity by coupling yttrium-analyte complexes and three-way fast high-performance liquid chromatography data modeling.

    PubMed

    Alcaraz, Mirta R; Culzoni, María J; Goicoechea, Héctor C

    2016-01-01

    The present study reports a sensitive chromatographic method for the analysis of seven fluoroquinolones (FQs) in environmental water samples, by coupling yttrium-analyte complex and three-way chromatographic data modeling. This method based on the use of HPLC-FSFD does not require complex or tedious sample treatments or enrichment processes before the analysis, due to the significant fluorescence increments of the analytes reached by the presence of Y(3+). Enhancement achieved for the FQs signals obtained after Y(3+) addition reaches 103- to 1743-fold. Prediction results corresponding to the application of MCR-ALS to the validation set showed relative error of prediction (REP%) values below 10% in all cases. A recovery study that includes the simultaneous determination of the seven FQs in three different environmental aqueous matrices was conducted. The recovery studies assert the efficiency and the accuracy of the proposed method. The LOD values calculated are in the order of part per trillion (below 0.5 ng mL(-1) for all the FQs, except for enoxacin). It is noteworthy to mention that the method herein proposed, which does not include pre-concentration steps, allows reaching LOD values in the same order of magnitude than those achieved by more sophisticated methods based on SPE and UHPLC-MS/MS.

  1. Coupling solid-phase microextraction with ambient mass spectrometry using surface coated wooden-tip probe for rapid analysis of ultra trace perfluorinated compounds in complex samples.

    PubMed

    Deng, Jiewei; Yang, Yunyun; Fang, Ling; Lin, Li; Zhou, Haiyun; Luan, Tiangang

    2014-11-18

    Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified.

  2. Ligand noninnocence of thiolate/disulfide in dinuclear copper complexes: solvent-dependent redox isomerization and proton-coupled electron transfer.

    PubMed

    Thomas, Andrew M; Lin, Bo-Lin; Wasinger, Erik C; Stack, T Daniel P

    2013-12-18

    Copper thiolate/disulfide interconversions are related to the functions of several important proteins such as human Sco1, Cu-Zn superoxide dismutase (SOD1), and mammalian zinc-bonded metallothionein. The synthesis and characterization of well-defined synthetic analogues for such interconversions are challenging yet provide important insights into the mechanisms of such redox processes. Solvent-dependent redox isomerization and proton-coupled electron transfer mimicking these interconversions are observed in two structurally related dimeric μ,η(2):η(2)-thiolato Cu(II)Cu(II) complexes by various methods, including X-ray diffraction, XAS, NMR, and UV-vis. Spectroscopic evidence shows that a solvent-dependent equilibrium exists between the dimeric μ-thiolato Cu(II)Cu(II) state and its redox isomeric μ-disulfido Cu(I)Cu(I) form. Complete formation of μ-disulfido Cu(I)Cu(I) complexes, however, only occurs after the addition of 2 equiv of protons, which promote electron transfer from thiolate to Cu(II) and formation of disulfide and Cu(I) via protonation of the coordinating ligand. Proton removal reverses this reaction. The reported unusual reductive protonation/oxidative deprotonation of the metal centers may serve as a new chemical precedent for how related proteins manage Cu ions in living organisms.

  3. TULP3 bridges the IFT-A complex and membrane phosphoinositides to promote trafficking of G protein-coupled receptors into primary cilia.

    PubMed

    Mukhopadhyay, Saikat; Wen, Xiaohui; Chih, Ben; Nelson, Christopher D; Lane, William S; Scales, Suzie J; Jackson, Peter K

    2010-10-01

    Primary cilia function as a sensory signaling compartment in processes ranging from mammalian Hedgehog signaling to neuronal control of obesity. Intraflagellar transport (IFT) is an ancient, conserved mechanism required to assemble cilia and for trafficking within cilia. The link between IFT, sensory signaling, and obesity is not clearly defined, but some novel monogenic obesity disorders may be linked to ciliary defects. The tubby mouse, which presents with adult-onset obesity, arises from mutation in the Tub gene. The tubby-like proteins comprise a related family of poorly understood proteins with roles in neural development and function. We find that specific Tubby family proteins, notably Tubby-like protein 3 (TULP3), bind to the IFT-A complex. IFT-A is linked to retrograde ciliary transport, but, surprisingly, we find that the IFT-A complex has a second role directing ciliary entry of TULP3. TULP3 and IFT-A, in turn, promote trafficking of a subset of G protein-coupled receptors (GPCRs), but not Smoothened, to cilia. Both IFT-A and membrane phosphoinositide-binding properties of TULP3 are required for ciliary GPCR localization. TULP3 and IFT-A proteins both negatively regulate Hedgehog signaling in the mouse embryo, and the TULP3-IFT-A interaction suggests how these proteins cooperate during neural tube patterning.

  4. Electron transfer reactivity of the aqueous iron(IV)–oxo complex. Outer-sphere vs proton-coupled electron transfer

    DOE PAGES

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2016-06-18

    Here, the kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, FeIV(H2O)5O2+ (hereafter FeIVaqO2+), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN)32+ (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS–/ABTS2–, phenothiazines, CoII(dmgBF2)2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. FeIVaqO2+ oxidizes even Ce(III) (E0 in 1 M HClO4 = 1.7more » V) with a rate constant greater than 104 M–1 s–1. In 0.10 M aqueous HClO4 at 25 °C, the reactions of Os(phen)32+ (k = 2.5 × 105 M–1 s–1), IrCl63– (1.6 × 106), ABTS2– (4.7 × 107), and Fe(cp)(C5H4CH2OH) (6.4 × 107) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen)32+ and of ferrocenes remained unchanged in the acidity range 0.05 < [H+] < 0.10 M, ruling out prior protonation of FeIVaqO2+ and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k22 + E0Fe/0.059) = 17.2 ± 0.8, where k22 and E0Fe are the self-exchange rate constant and reduction potential, respectively, for the FeIVaqO2+/FeIIIaqO+ couple. Comparison with literature work suggests k22 < 10–5 M–1 s–1 and thus E0(FeIVaqO2+/FeIIIaqO+) > 1.3 V. For proton-coupled electron transfer, the reduction potential is estimated at E0 (FeIVaqO2+, H+/FeIIIaqOH2+) ≥ 1.95 V.« less

  5. Determination of aminopolycarboxylic acids at ultra-trace levels by means of online coupling ion exchange chromatography and inductively coupled plasma-mass spectrometry with indirect detection via their Pd²⁺-complexes.

    PubMed

    Nette, David; Seubert, Andreas

    2015-07-16

    A new indirect IC-ICP-MS method for the determination of aminopolycarboxylic acids in water samples is described. It is based on the addition of an excess of Pd(II) to water samples. The analytes are forced into very strong and negatively charged palladium complexes, separated by ion exchange chromatography and detected by their palladium content, utilizing an on-line coupled ICP-MS. This method is suitable to determine the concentration of 8 aminopolycarboxylic acids (nitrilotriacetic acid (NTA), (2-carboxyethyl) iminodiacetic acid (β-ADA), methylglycinediacetic acid (MGDA), 2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA), diethylene triamine pentaacetic acid (DTPA), ethylendiamine tetraacetic acid (EDTA), 1,3-diaminopropane tetraacetic acid (1,3-PDTA) and 1,2-diaminopropane tetraacetic acid (1,2-PDTA) at the ng kg(-1) level. The method is faster and easier than the established gas chromatography (GC)-method ISO 16588:2002 and up to two orders of magnitude more sensitive than the ion pair chromatography based method of DIN 38413-8. Analytic performance is superior to ISO 16588:2002 and the comparability is good. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Removal of high-salinity matrices through polymer-complexation-ultrafiltration for the detection of trace levels of REEs using inductively coupled plasma mass spectrometry.

    PubMed

    Duan, Hualing; Lin, Jijun; Gong, Zhenbin; Huang, Jiahua; Yang, Shifeng

    2015-10-01

    The polymer-complexation-ultrafiltration (PCUF) technique was applied to separate trace levels of rare earth elements (REEs), including scandium, yttrium and the lanthanides, from high-salinity matrices prior to their determination by inductively coupled plasma mass spectrometry (ICP-MS). The REEs were converted into REE-polymer complexes using the water-soluble polymer polyacrylic acid (PAA) at a specified pH, retained on the ultrafiltration membrane of centrifugal filter units, and finally eluted using diluted nitric acid to achieve separation from matrices with relatively high levels of various inorganic ions, such as sodium, potassium, calcium, magnesium, and chlorine ions. Numerous factors affecting the PCUF efficiency were optimized. The optimal conditions included the addition of 30 mg L(-1) of PAA, a pH of 7.5, a reaction time of 40 min at room temperature, and 5.0 mL of 3% nitric acid (v/v) eluent. Under these conditions, the analytes were quantitatively separated and recovered, with a resulting relative standard deviation (RSD) of less than 4.0% (0.05 µg L(-1), n=5) and standard addition recoveries between 89.2% (La) and 95.8% (Sm) for matrices of various salinities. The blank samples for the method ranged from 0.0003 µg L(-1) (Dy) to 0.0031 µg L(-1) (Sc), and the limits of quantification (LOQs, 10σ) were between 0.0006 µg L(-1) (Dy) and 0.0026 µg L(-1) (Sc). Furthermore, the salinity of the sample exhibited no effect on the REE-polymer complex formation process. Finally, the method was successfully applied for the determination of trace levels of dissolved Sc, Y, and lanthanides in coastal and estuarine seawater samples.

  7. Rebuilding a macromolecular membrane complex at the atomic scale: case of the Kir6.2 potassium channel coupled to the muscarinic acetylcholine receptor M2.

    PubMed

    Sapay, Nicolas; Estrada-Mondragon, Argel; Moreau, Christophe; Vivaudou, Michel; Crouzy, Serge

    2014-09-01

    Ion channel-coupled receptors (ICCR) are artificial proteins built from a G protein-coupled receptor and an ion channel. Their use as molecular biosensors is promising in diagnosis and high-throughput drug screening. The concept of ICCR was initially validated with the combination of the muscarinic receptor M2 with the inwardly rectifying potassium channel Kir6.2. A long protein engineering phase has led to the biochemical characterization of the M2-Kir6.2 construct. However, its molecular mechanism remains to be elucidated. In particular, it is important to determine how the activation of M2 by its agonist acetylcholine triggers the modulation of the Kir6.2 channel via the M2-Kir6.2 linkage. In the present study, we have developed and validated a computational approach to rebuild models of the M2-Kir6.2 chimera from the molecular structure of M2 and Kir6.2. The protocol was first validated on the known protein complexes of the μ-opioid Receptor, the CXCR4 receptor and the Kv1.2 potassium channel. When applied to M2-Kir6.2, our protocol produced two possible models corresponding to two different orientations of M2. Both models highlights the role of the M2 helices I and VIII in the interaction with Kir6.2, as well as the role of the Kir6.2 N-terminus in the channel opening. Those two hypotheses will be explored in a future experimental study of the M2-Kir6.2 construct.

  8. Prediction Models of Retention Indices for Increased Confidence in Structural Elucidation during Complex Matrix Analysis: Application to Gas Chromatography Coupled with High-Resolution Mass Spectrometry.

    PubMed

    Dossin, Eric; Martin, Elyette; Diana, Pierrick; Castellon, Antonio; Monge, Aurelien; Pospisil, Pavel; Bentley, Mark; Guy, Philippe A

    2016-08-02

    Monitoring of volatile and semivolatile compounds was performed using gas chromatography (GC) coupled to high-resolution electron ionization mass spectrometry, using both headspace and liquid injection modes. A total of 560 reference compounds, including 8 odd n-alkanes, were analyzed and experimental linear retention indices (LRI) were determined. These reference compounds were randomly split into training (n = 401) and test (n = 151) sets. LRI for all 552 reference compounds were also calculated based upon computational Quantitative Structure-Property Relationship (QSPR) models, using two independent approaches RapidMiner (coupled to Dragon) and ACD/ChromGenius software. Correlation coefficients for experimental versus predicted LRI values calculated for both training and test set compounds were calculated at 0.966 and 0.949 for RapidMiner and at 0.977 and 0.976 for ACD/ChromGenius, respectively. In addition, the cross-validation correlation was calculated at 0.96 from RapidMiner and the residual standard error value obtained from ACD/ChromGenius was 53.635. These models were then used to predict LRI values for several thousand compounds reported present in tobacco and tobacco-related fractions, plus a range of specific flavor compounds. It was demonstrated that using the mean of the LRI values predicted by RapidMiner and ACD/ChromGenius, in combination with accurate mass data, could enhance the confidence level for compound identification from the analysis of complex matrixes, particularly when the two predicted LRI values for a compound were in close agreement. Application of this LRI modeling approach to matrixes with unknown composition has already enabled the confirmation of 23 postulated compounds, demonstrating its ability to facilitate compound identification in an analytical workflow. The goal is to reduce the list of putative candidates to a reasonable relevant number that can be obtained and measured for confirmation.

  9. Electrons and proton transfer in chloroplasts in silico: 1. The effect of topological factors on energy coupling in chloroplasts with a nonuniform distribution of protein complexes

    NASA Astrophysics Data System (ADS)

    Vershubskii, A. V.; Tikhonov, A. N.

    2017-05-01

    This paper presents a theoretical study of the effects of topological factors (density of thylakoid packing in grana) on the efficiency of energy coupling in chloroplasts. The study is based on a mathematical model of electron and proton transport processes coupled to ATP synthesis in chloroplasts. The model was developed by the authors earlier, and the nonuniform distribution of electron transport and ATP synthase complexes in the membranes of granal and intergranal thylakoids was taken into account in the model. The results of numerical experiments enabled the analysis of the distribution of lateral profiles of the transmembrane pH difference and the concentrations of mobile plastoquinone and plastocyanin electron transporters in granal and intergranal thylakoids and the dependence of this distribution on the metabolic state of class B chloroplasts (photosynthetic control state or the conditions of intensive ATP synthesis). Moreover, the influence of topological factors (the density of thylakoid packing in grana and the degree of thylakoid swelling) that affect the rate of diffusion of protons and mobile electron carriers in the intrathylakoid space and in the interthylakoidal gap was investigated. The results of numerical experiments that involved the variation of geometric parameters of the system revealed the influence of thylakoid thickness and the distance between the granal thylakoids on the lateral pH profiles inside the thylakoids (pHi) and in the interthylakoidal gap (pHo). Acidification of the intrathylakoid space characterized by the pHi value increased concomitantly to the increase of the width of the interthylakoidal gap l o and decreased concomitantly to the increase of the width of the intrathylakoidal space l i.

  10. Electron Transport in a Dioxygenase-Ferredoxin Complex: Long Range Charge Coupling between the Rieske and Non-Heme Iron Center

    PubMed Central

    Jono, Ryota; Shimizu, Kentaro

    2016-01-01

    Dioxygenase (dOx) utilizes stereospecific oxidation on aromatic molecules; consequently, dOx has potential applications in bioremediation and stereospecific oxidation synthesis. The reactive components of dOx comprise a Rieske structure Cys2[2Fe-2S]His2 and a non-heme reactive oxygen center (ROC). Between the Rieske structure and the ROC, a universally conserved Asp residue appears to bridge the two structures forming a Rieske-Asp-ROC triad, where the Asp is known to be essential for electron transfer processes. The Rieske and ROC share hydrogen bonds with Asp through their His ligands; suggesting an ideal network for electron transfer via the carboxyl side chain of Asp. Associated with the dOx is an itinerant charge carrying protein Ferredoxin (Fdx). Depending on the specific cognate, Fdx may also possess either the Rieske structure or a related structure known as 4-Cys-[2Fe-2S] (4-Cys). In this study, we extensively explore, at different levels of theory, the behavior of the individual components (Rieske and ROC) and their interaction together via the Asp using a variety of density function methods, basis sets, and a method known as Generalized Ionic Fragment Approach (GIFA) that permits setting up spin configurations manually. We also report results on the 4-Cys structure for comparison. The individual optimized structures are compared with observed spectroscopic data from the Rieske, 4-Cys and ROC structures (where information is available). The separate pieces are then combined together into a large Rieske-Asp-ROC (donor/bridge/acceptor) complex to estimate the overall coupling between individual components, based on changes to the partial charges. The results suggest that the partial charges are significantly altered when Asp bridges the Rieske and the ROC; hence, long range coupling through hydrogen bonding effects via the intercalated Asp bridge can drastically affect the partial charge distributions compared to the individual isolated structures. The

  11. Development of a 3D coupled physical-biogeochemical model for the Marseille coastal area (NW Mediterranean Sea): what complexity is required in the coastal zone?

    PubMed

    Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane

    2013-01-01

    Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007-2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model.

  12. Development of a 3D Coupled Physical-Biogeochemical Model for the Marseille Coastal Area (NW Mediterranean Sea): What Complexity Is Required in the Coastal Zone?

    PubMed Central

    Fraysse, Marion; Pinazo, Christel; Faure, Vincent Martin; Fuchs, Rosalie; Lazzari, Paolo; Raimbault, Patrick; Pairaud, Ivane

    2013-01-01

    Terrestrial inputs (natural and anthropogenic) from rivers, the atmosphere and physical processes strongly impact the functioning of coastal pelagic ecosystems. The objective of this study was to develop a tool for the examination of these impacts on the Marseille coastal area, which experiences inputs from the Rhone River and high rates of atmospheric deposition. Therefore, a new 3D coupled physical/biogeochemical model was developed. Two versions of the biogeochemical model were tested, one model considering only the carbon (C) and nitrogen (N) cycles and a second model that also considers the phosphorus (P) cycle. Realistic simulations were performed for a period of 5 years (2007–2011). The model accuracy assessment showed that both versions of the model were able of capturing the seasonal changes and spatial characteristics of the ecosystem. The model also reproduced upwelling events and the intrusion of Rhone River water into the Bay of Marseille well. Those processes appeared to greatly impact this coastal oligotrophic area because they induced strong increases in chlorophyll-a concentrations in the surface layer. The model with the C, N and P cycles better reproduced the chlorophyll-a concentrations at the surface than did the model without the P cycle, especially for the Rhone River water. Nevertheless, the chlorophyll-a concentrations at depth were better represented by the model without the P cycle. Therefore, the complexity of the biogeochemical model introduced errors into the model results, but it also improved model results during specific events. Finally, this study suggested that in coastal oligotrophic areas, improvements in the description and quantification of the hydrodynamics and the terrestrial inputs should be preferred over increasing the complexity of the biogeochemical model. PMID:24324589

  13. Hollow porous ionic liquids composite polymers based solid phase extraction coupled online with high performance liquid chromatography for selective analysis of hydrophilic hydroxybenzoic acids from complex samples.

    PubMed

    Dai, Xingping; Wang, Dongsheng; Li, Hui; Chen, Yanyi; Gong, Zhicheng; Xiang, Haiyan; Shi, Shuyun; Chen, Xiaoqing

    2017-02-10

    Polar and hydrophilic properties of hydroxybenzoic acids usually made them coelute with interferences in high performance liquid chromatography (HPLC) analysis. Then selective analysis of them was necessary. Herein, hollow porous ionic liquids composite polymers (PILs) based solid phase extraction (SPE) was firstly fabricated and coupled online with HPLC for selective analysis of hydroxybenzoic acids from complex matrices. Hollow porous PILs were firstly synthesized using Mobil Composition of Matter No. 48 (MCM-48) spheres as sacrificial support, 1-vinyl-3-methylimidazolium chloride (VMIM(+)Cl(-)) as monomer, and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Various parameters affecting synthesis, adsorption and desorption behaviors were investigated and optimized. Steady-state adsorption studies showed the resulting hollow porous PILs exhibited high adsorption capacity, fast adsorption kinetics, and excellent specific adsorption. Subsequently, the application of online SPE system was studied by selective analysis of protocatechuic acid (PCA), 4-hydroxybenzoic acid (4-HBA), and vanillic acid (VA) from Pollen Typha angustifolia. The obtained limit of detection (LOD) varied from 0.002 to 0.01μg/mL, the linear range (0.05-5.0μg/mL) was wide with correlation coefficient (R) from 0.9982 to 0.9994, and the average recoveries at three spiking levels ranged from 82.7 to 102.4%, with column-to-column relative standard deviation (RSD) below 8.1%. The proposed online method showed good accuracy, precision, specificity and convenience, which opened up a universal and efficient route for selective analysis of hydroxybenzoic acids from complex samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. NMR studies of solid pentachlorophenol-4-methylpyridine complexes exhibiting strong OHN hydrogen bonds: geometric H/D isotope effects and hydrogen bond coupling cause isotopic polymorphism.

    PubMed

    Ip, Brenda C K; Shenderovich, Ilya G; Tolstoy, Peter M; Frydel, Jaroslaw; Denisov, Gleb S; Buntkowsky, Gerd; Limbach, Hans-Heinrich

    2012-11-26

    We have studied the hydrogen bond interactions of (15)N labeled 4-methylpyridine (4-MP) with pentachlorophenol (PCP) in the solid state and in polar solution using various NMR techniques. Previous spectroscopic, X-ray, and neutron crystallographic studies showed that the triclinic 1:1 complex (4-MPPCP) exhibits the strongest known intermolecular OHN hydrogen bond in the solid state. By contrast, deuteration of the hydrogen bond gives rise to the formation of a monoclinic structure exhibiting a weaker hydrogen bond. By performing NMR experiments at different deuterium fractions and taking advantage of dipolar (1)H-(15)N recoupling under combined fast MAS and (1)H decoupling, we provide an explanation of the origin of the isotopic polymorphism of 4-MPPCP and improve previous chemical shift correlations for OHN hydrogen bonds. Because of anharmonic ground state vibrations, an ODN hydrogen bond in the triclinic form exhibits a shorter oxygen-hydron and a longer oxygen-nitrogen distance as compared to surrounding OHN hydrogen bonds, which also implies a reduction of the local dipole moment. The dipole-dipole interaction between adjacent coupled OHN hydrogen bonds which determines the structure of triclinic 4-MPPCP is then reduced by deuteration, and other interactions become dominant, leading to the monoclinic form. Finally, the observation of stronger OHN hydrogen bonds by (1)H NMR in polar solution as compared to the solid state is discussed.

  15. Strong Coupling between the Hydrogen Bonding Environment and Redox Chemistry during the S2 to S3 Transition in the Oxygen-Evolving Complex of Photosystem II.

    PubMed

    Isobe, Hiroshi; Shoji, Mitsuo; Shen, Jian-Ren; Yamaguchi, Kizashi

    2015-10-29

    We have studied the early phase of the S2 → S3 transition in the oxygen-evolving complex (OEC) of photosystem II using the hybrid density functional theory with a quantum mechanical model composed of 338-341 atoms. Special attention is given to the vital role of water molecules in the vicinity of the Mn4CaO5 core. Our results demonstrate how important the dynamic behavior of surrounding water molecules is in mediating critical chemical transformations such as binding and deprotonation of substrates and hydration of the catalytic site and identify a strong coupling of water-chain relocation near the redox-active tyrosine residue Tyr161 (TyrZ) with oxidation of the Mn4CaO5 cluster by TyrZ(•+). The oxidation reaction is further promoted when the catalytic site is more solvated by water. These results indicate the importance of surrounding water molecules in biological catalysts as they ultimately lead to effective catalytic function and/or favorable electron-transfer dynamics.

  16. Myosin subfragment 1 structures reveal a partially bound nucleotide and a complex salt bridge that helps couple nucleotide and actin binding.

    PubMed

    Risal, Dipesh; Gourinath, S; Himmel, Daniel M; Szent-Györgyi, Andrew G; Cohen, Carolyn

    2004-06-15

    Structural studies of myosin have indicated some of the conformational changes that occur in this protein during the contractile cycle, and we have now observed a conformational change in a bound nucleotide as well. The 3.1-A x-ray structure of the scallop myosin head domain (subfragment 1) in the ADP-bound near-rigor state (lever arm =45 degrees to the helical actin axis) shows the diphosphate moiety positioned on the surface of the nucleotide-binding pocket, rather than deep within it as had been observed previously. This conformation strongly suggests a specific mode of entry and exit of the nucleotide from the nucleotide-binding pocket through the so-called "front door." In addition, using a variety of scallop structures, including a relatively high-resolution 2.75-A nucleotide-free near-rigor structure, we have identified a conserved complex salt bridge connecting the 50-kDa upper and N-terminal subdomains. This salt bridge is present only in crystal structures of muscle myosin isoforms that exhibit a strong reciprocal relationship (also known as coupling) between actin and nucleotide affinity.

  17. The three-dimensional structure of the gallium complex of azoverdin, a siderophore of Azomonas macrocytogenes ATCC 12334, determined by NMR using residual dipolar coupling constants.

    PubMed

    Wasielewski, Emeric; Atkinson, R Andrew; Abdallah, Mohamed A; Kieffer, Bruno

    2002-10-15

    In iron-deficient conditions, Azomonas macrocytogenes ATCC 12334 excretes a fluorescent siderophore called azoverdin, which is composed of a six-amino-acid peptide chain linked to a chromophore. Azoverdin chelates iron(III) very strongly, solubilizing it and transporting it back into the cells using an outer-membrane receptor. This compound is related to the pyoverdins, the peptidic siderophores of Pseudomonas, but differs in the site on the chromophore at which the peptide is covalently linked. This feature identifies azoverdin as a member of a new class of pyoverdins: the isopyoverdins. We report the three-dimensional structure of azoverdin-Ga(III) in solution. The use of orientational constraints obtained from the measurement of residual dipolar couplings using samples dissolved in a liquid crystalline medium allowed us to define the absolute configuration of the metal complex, which is Delta. The structure is characterized by a U-shape adopted by the peptide chain, with the N(delta)-acetyl-N(delta)-hydroxyornithine side chains adopting extended conformations in order to chelate the gallium ion. This conformation leaves a large open space permitting access to the gallium ion. The structural consequences of the particular isopyoverdin chemical structure are discussed in the context of the three-dimensional structures of other pyoverdins.

  18. Electron transfer reactivity of the aqueous iron(IV)–oxo complex. Outer-sphere vs proton-coupled electron transfer

    SciTech Connect

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2016-06-18

    Here, the kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, FeIV(H2O)5O2+ (hereafter FeIVaqO2+), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN)32+ (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS–/ABTS2–, phenothiazines, CoII(dmgBF2)2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. FeIVaqO2+ oxidizes even Ce(III) (E0 in 1 M HClO4 = 1.7 V) with a rate constant greater than 104 M–1 s–1. In 0.10 M aqueous HClO4 at 25 °C, the reactions of Os(phen)32+ (k = 2.5 × 105 M–1 s–1), IrCl63– (1.6 × 106), ABTS2– (4.7 × 107), and Fe(cp)(C5H4CH2OH) (6.4 × 107) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen)32+ and of ferrocenes remained unchanged in the acidity range 0.05 < [H+] < 0.10 M, ruling out prior protonation of FeIVaqO2+ and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k22 + E0Fe/0.059) = 17.2 ± 0.8, where k22 and E0Fe are the self-exchange rate constant and reduction potential

  19. Electron transfer reactivity of the aqueous iron(IV)–oxo complex. Outer-sphere vs proton-coupled electron transfer

    SciTech Connect

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2016-06-18

    Here, the kinetics of oxidation of organic and inorganic reductants by aqueous iron(IV) ions, FeIV(H2O)5O2+ (hereafter FeIVaqO2+), are reported. The substrates examined include several water-soluble ferrocenes, hexachloroiridate(III), polypyridyl complexes M(NN)32+ (M = Os, Fe and Ru; NN = phenanthroline, bipyridine and derivatives), HABTS–/ABTS2–, phenothiazines, CoII(dmgBF2)2, macrocyclic nickel(II) complexes, and aqueous cerium(III). Most of the reductants were oxidized cleanly to the corresponding one-electron oxidation products, with the exception of phenothiazines which produced the corresponding oxides in a single-step reaction, and polypyridyl complexes of Fe(II) and Ru(II) that generated ligand-modified products. FeIVaqO2+ oxidizes even Ce(III) (E0 in 1 M HClO4 = 1.7 V) with a rate constant greater than 104 M–1 s–1. In 0.10 M aqueous HClO4 at 25 °C, the reactions of Os(phen)32+ (k = 2.5 × 105 M–1 s–1), IrCl63– (1.6 × 106), ABTS2– (4.7 × 107), and Fe(cp)(C5H4CH2OH) (6.4 × 107) appear to take place by outer sphere electron transfer (OSET). The rate constants for the oxidation of Os(phen)32+ and of ferrocenes remained unchanged in the acidity range 0.05 < [H+] < 0.10 M, ruling out prior protonation of FeIVaqO2+ and further supporting the OSET assignment. A fit to Marcus cross-relation yielded a composite parameter (log k22 + E0Fe/0.059) = 17.2 ± 0.8, where k22 and E0Fe are the self-exchange rate constant and reduction potential

  20. Polynuclear platinum phosphanido/phosphinito complexes: formation of P-O and P-O-P bonds through reductive coupling processes.

    PubMed

    Ara, Irene; Forniés, Juan; Ibáñez, Susana; Mastrorilli, Piero; Todisco, Stefano; Gallo, Vito

    2016-02-07

    A mixture of the asymmetric complexes of formula [(RF)2Pt(μ-Ph2PO)(μ-PPh2)Pt(μ-PPh2)2Pt(solv)(solv')] [(1-(solv)(solv')] (solv, solv' = acetone, H2O, CH3CN) has been prepared by reaction of [(RF)2Pt(II)(μ-PPh2)2Pt(II)(μ-PPh2)2Pt(II)(NCCH3)2] with AgClO4 in CH3CN/acetone. The lability of the Pt-solvent bonds allows the displacement of the coordinated solvent molecules by dppm or Cl(-) and the isolation of the tri- or hexanuclear phosphanido/phosphinito Pt(ii) complexes [(C6F5)2Pt(μ-PPh2)(μ-PPh2O)Pt(μ-PPh2)2Pt(dppm)] (2) or [NBu4]2[(C6F5)2Pt(μ-PPh2)(μ-PPh2O)Pt(μ-PPh2)2Pt(μ-Cl)2Pt(μ-PPh2)2Pt(μ-PPh2)(μ-PPh2O)Pt(C6F5)2] (as a mixture of the two possible isomers 4a and 4b). Complex 2 reacts with AgClO4 to form the tetranuclear derivative [(C6F5)2Pt(μ-PPh2)(μ-PPh2O)Pt(μ-PPh2)2Pt(dppm)Ag(OClO3)] (3), which displays two Pt-Ag donor-acceptor bonds. The mixture of the hexanuclear isomers 4a-4b reacts with Tl(acac) producing the acetylacetonato complex [NBu4][(C6F5)2Pt(μ-PPh2)(μ-PPh2O)Pt(μ-PPh2)2Pt(acac)] (5) which, upon reaction with HCl, yields back the mixture of 4a-4b. The reaction of 4a-4b with PPh3 produces [NBu4][(C6F5)2Pt(μ-PPh2)(μ-PPh2O)Pt(μ-PPh2)2Pt(Cl)(PPh3)] (6) as a mixture of isomers with the chloro ligand located syn (6a) or anti (6b) to the PPh2O(-) group. Either the reaction of 6 with AgClO4 or the treatment of 5 with HPPh3ClO4 results in the formation of the species [(C6F5)2Pt(II)(μ-PPh2)2Pt(I)(μ-PPh2OPPh2)Pt(I)(PPh3)] (7) (44 VEC), which can be explained as the consequence of a PPh2O/PPh2 reductive coupling and a rearrangement of ligands in the molecule generating a Pt(ii),Pt(i),Pt(i) compound. All complexes were characterised in the solid state by XRD (only one of the isomers, in the cases of 4 and 6) and in solution by NMR spectroscopy.

  1. Carbon–Hydrogen Bond Activation, C–N Bond Coupling, and Cycloaddition Reactivity of a Three-Coordinate Nickel Complex Featuring a Terminal Imido Ligand

    PubMed Central

    2015-01-01

    The three-coordinate imidos (dtbpe)Ni=NR (dtbpe = tBu2PCH2CH2PtBu2, R = 2,6-iPr2C6H3, 2,4,6-Me3C6H2 (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HC≡CPh to form the amide acetylide species (dtbpe)Ni{NH(Ar)}(C≡CPh). In the case of R = 2,6-iPr2C6H3, reductive carbonylation results in formation of the (dtbpe)Ni(CO)2 along with the N–C coupled product keteneimine PhCH=C=N(2,6- iPr2C6H3). Given the ability of the Ni=N bond to have biradical character as suggested by theoretical analysis, H atom abstraction can also occur in (dtbpe)Ni=N{2,6-iPr2C6H3} when this species is treated with HSn(nBu)3. Likewise, the microscopic reverse reaction—conversion of the Ni(I) anilide (dtbpe)Ni{NH(2,6-iPr2C6H3)} to the imido (dtbpe)Ni=N{2,6-iPr2C6H3}—is promoted when using the radical Mes*O• (Mes* = 2,4,6-tBu3C6H2). Reactivity studies involving the imido complexes, in particular (dtbpe)Ni=N{2,6-iPr2C6H3}, are also reported with small, unsaturated molecules such as diphenylketene, benzylisocyanate, benzaldehyde, and carbon dioxide, including the formation of C–N and N–N bonds by coupling reactions. In addition to NMR spectroscopic data and combustion analysis, we also report structural studies for all the cycloaddition reactions involving the imido (dtbpe)Ni=N{2,6-iPr2C6H3}. PMID:25437507

  2. Carbon–hydrogen bond activation, C–N bond coupling, and cycloaddition reactivity of a three-coordinate nickel complex featuring a terminal imido ligand

    DOE PAGES

    Mindiola, Daniel J.; Waterman, Rory; Iluc, Vlad M.; ...

    2014-12-01

    Here, the three-coordinate imidos (dtbpe)Ni=NR (dtbpe = tBu2PCH2CH2PtBu2, R = 2,6-iPr2C6H3, 2,4,6-Me3C6H2 (Mes), and 1-adamantyl (Ad)), which contain a legitimate Ni–N double bond as well as basic imido nitrogen based on theoretical analysis, readily deprotonate HC≡CPh to form the amide acetylide species (dtbpe)Ni{NH(Ar)}(C≡CPh). In the case of R = 2,6-iPr2C6H3, reductive carbonylation results in formation of the (dtbpe)Ni(CO)2 along with the N–C coupled product keteneimine PhCH=C=N(2,6- iPr2C6H3). Given the ability of the Ni=N bond to have biradical character as suggested by theoretical analysis, H atom abstraction can also occur in (dtbpe)Ni=N{2,6-iPr2C6H3} when this species is treated with HSn(nBu)3. Likewise, themore » microscopic reverse reaction—conversion of the Ni(I) anilide (dtbpe)Ni{NH(2,6-iPr2C6H3)} to the imido (dtbpe)Ni=N{2,6-iPr2C6H3}—is promoted when using the radical Mes*O• (Mes* = 2,4,6-tBu3C6H2). Reactivity studies involving the imido complexes, in particular (dtbpe)Ni=N{2,6-iPr2C6H3}, are also reported with small, unsaturated molecules such as diphenylketene, benzylisocyanate, benzaldehyde, and carbon dioxide, including the formation of C–N and N–N bonds by coupling reactions. In addition to NMR spectroscopic data and combustion analysis, we also report structural studies for all the cycloaddition reactions involving the imido (dtbpe)Ni=N{2,6-iPr2C6H3}.« less

  3. Fourier-transform spectroscopy and coupled-channels deperturbation treatment of the A {sup 1{Sigma}+}-b {sup 3{Pi}} complex of KCs

    SciTech Connect

    Kruzins, A.; Klincare, I.; Nikolayeva, O.; Tamanis, M.; Ferber, R.; Pazyuk, E. A.; Stolyarov, A. V.

    2010-04-15

    The laser-induced fluorescence (LIF) A {sup 1{Sigma}+}-b {sup 3{Pi}{yields}}X {sup 1{Sigma}+} spectra of the KCs molecule were recorded in a near infrared region by a Fourier-transform spectrometer with a resolution of 0.03 cm{sup -1}. Overall more than 200 collisionally enhanced LIF spectra were rotationally assigned to {sup 39}K{sup 133}Cs and {sup 41}K{sup 133}Cs isotopomers yielding more than 3400 rovibronic term values of the strongly mixed singlet A {sup 1{Sigma}+} and triplet b {sup 3{Pi}} states with the uncertainty of 0.003-0.01 cm{sup -1}. Experimental data massive starts from the lowest vibrational level v{sub A}=0 of the singlet and nonuniformly covers the energy range E is an element of [10 040,13 250] cm{sup -1} with rotational quantum numbers J{sup '} is an element of [7,225]. Besides the dominating regular A {sup 1{Sigma}+}-b {sup 3{Pi}}{sub {Omega}=0} interactions, the weak local heterogeneous A {sup 1{Sigma}+}-b {sup 3{Pi}}{sub {Omega}=1} perturbations have been discovered and analyzed. Coupled-channels deperturbation analysis of the experimental {sup 39}K{sup 133}Cs e-parity term values of the A {sup 1{Sigma}+}-b {sup 3{Pi}}{sub {Omega}=0,1,2} complex was accomplished in the framework of the phenomenological 4x4 Hamiltonian accounting implicitly for regular interactions with the remote {sup 1{Pi}} and {sup 3{Sigma}+} states. The diabatic potential energy curves of the A {sup 1{Sigma}+} and b {sup 3{Pi}} states, as well as relevant spin-orbit coupling matrix elements, were defined analytically with the expanded Morse oscillators model. The obtained parameters reproduce 95% of experimental data field of the {sup 39}K{sup 133}Cs isotopomer with a standard deviation of 0.004 cm{sup -1}, which is consistent with the uncertainty of the experiment. Reliability of the derived parameters was confirmed by a good agreement between the predicted and experimental term values of the {sup 41}K{sup 133}Cs isotopomer. The calculated relative intensity

  4. Human spliceosomal protein CWC22 plays a role in coupling splicing to exon junction complex deposition and nonsense-mediated decay

    PubMed Central

    Alexandrov, Andrei; Colognori, David; Shu, Mei-Di; Steitz, Joan A.

    2012-01-01

    The multiprotein exon junction complex (EJC) that is deposited upstream of spliced junctions orchestrates downstream events in the life of a metazoan mRNA, including its surveillance via the nonsense-mediated decay (NMD) pathway. However, the mechanism by which the spliceosome mediates EJC formation is not well understood. We show that human eIF4G-like spliceosomal protein (h)CWC22 directly interacts with the core EJC component eIF4AIII in vitro and in vivo; mutations at the predicted hCWC22/eIF4AIII interface disrupt association. In vivo depletion of hCWC22, as for yeast Cwc22p, causes a splicing defect, resulting in decreased levels of mature cellular mRNAs. Nonetheless, hCWC22 depletion yields increased levels of spliced RNA from the unusual nonsense codon-containing U22 host gene, which is a natural substrate of NMD. To test whether hCWC22 acts in NMD through coupling splicing to EJC deposition, we searched for mutations in hCWC22 that affect eIF4AIII deposition without affecting splicing. Addition of hCWC22(G168Y) with a mutation at the putative hCWC22/eIF4AIII interface exacerbates the defect in splicing-dependent deposition of eIF4AIII(T334V) with a mutation reported to be in direct contact with mRNA, linking hCWC22 to the process of EJC deposition in vitro. Importantly, the addition of hCWC22(G168Y) affects deposition of eIF4AIII(T334V) without inhibiting splicing or the efficiency of deposition of the endogenous eF4AIII(WT) in the same reaction, demonstrating hCWC22’s specific role in eIF4AIII deposition in addition to its role in splicing. The essential splicing factor CWC22 has, therefore, acquired functions in EJC assembly and NMD during evolution from single-celled to complex eukaryotes. PMID:23236153

  5. Magnetic Interactions in the Copper Complex (L-Aspartato)(1,10-phenanthroline)copper(II) Hydrate. An Exchange-Coupled Extended System with Two Dissimilar Copper Ions.

    PubMed

    Brondino, Carlos D.; Calvo, Rafael; Atria, Ana María; Spodine, Evgenia; Nascimento, Otaciro R.; Peña, Octavio

    1997-07-02

    We report EPR measurements in single-crystal samples at the microwave frequencies 9.8 and 34.3 GHz and magnetic susceptibility measurements in polycrystalline samples for the ternary complex of copper with aspartic acid and phenanthroline, (L-aspartato)(1,10-phenanthroline)copper(II) hydrate. The crystal lattice of this compound is composed of two dissimilar copper ions identified as Cu(A) and Cu(B), which are in two types of copper chains called A and B, respectively, running parallel to the b crystal axis. The copper ions in the A chains are connected by the aspartic acid molecule, and those in the B chains by a chemical path that involves a carboxylate bridge and a hydrogen bond. Both chains are held together by a complex network of hydrogen bonds and by hydrophobic interactions between aromatic amines. Magnetic susceptibility data indicate a Curie-Weiss behavior in the studied temperature range (2-300 K). The EPR spectra at 9.8 GHz display a single exchange collapsed resonance for any magnetic field orientation, in the so-called strong exchange regime. Those at 34.3 GHz are within the so-called weak exchange regime and display two resonances which belong to each type of copper ion chain. The decoupling of the spectra at 34.3 GHz using a theory based on Anderson's model for the case of two weakly exchange coupled spins S = (1)/(2) allows one to obtain the angular variation of the squares of the g-factor and the peak-to-peak line width of each resonance. This model also allows one to evaluate the exchange parameter |J(AB)/k| = 2.7(6) mK associated with the chemical path connecting dissimilar copper ions. The line width data obtained for each component of the spectra at 34.3 GHz are analyzed in terms of a model based on Kubo and Tomita's theory, to obtain the exchange parameters |J(A)/k| = 0.77(2) K and |J(B)/k| = 1.44(2) K associated with the chemical paths connecting the similar copper ions of types A and B, respectively.

  6. Three-dimensional seismic structure and moment tensors of non-double-couple earthquakes at the Hengill-Grensdalur volcanic complex, Iceland

    USGS Publications Warehouse

    Miller, A.D.; Julian, B.R.; Foulger, G.R.

    1998-01-01

    The volcanic and geothermal areas of Iceland are rich sources of non-double-couple (non-DC) earthquakes. A state-of-the-art digital seismometer network deployed at the Hengill-Grensdalur volcanic complex in 1991 recorded 4000 small earthquakes. We used the best recorded of these to determine 3-D VP and VP/VS structure tomographically and accurate earthquake moment tensors. The VP field is dominated by high seismic wave speed bodies interpreted as solidified intrusions. A widespread negative (-4 per cent) VP/VS anomaly in the upper 4 km correlates with the geothermal field, but is too strong to be caused solely by the effect of temperature upon liquid water or the presence of vapour, and requires in addition mineralogical or lithological differences between the geothermal reservoir and its surroundings. These may be caused by geothermal alteration. Well-constrained moment tensors were obtained for 70 of the best-recorded events by applying linear programming methods to P- and S-wave polarities and amplitude ratios. About 25 per cent of the mechanisms are, within observational error, consistent with DC mechanisms consistent with shear faulting. The other 75 per cent have significantly non-DC mechanisms. Many have substantial explosive components, one has a substantial implosive component, and the deviatoric component of many is strongly non-DC. Many of the non-DC mechanisms are consistent, within observational error, with simultaneous tensile and shear faulting. However, the mechanisms occupy a continuum in source-type parameter space and probably at least one additional source process is occurring. This may be fluid flow into newly formed cracks, causing partial compensation of the volumetric component. Studying non-shear earthquakes such as these has great potential for improving our understanding of geothermal processes and earthquake source processes in general.

  7. New approach on volatile contents determination in silicate melt inclusions: A coupling X-ray microtomography and geochemical approach in Los Humeros caldera complex (Eastern Mexican Volcanic Belt)

    NASA Astrophysics Data System (ADS)

    Creon, L.; Levresse, G.; Carrasco Nuñez, G.

    2016-12-01

    Volatile contents and magma degassing behavior are known to affect the style, frequency, and intensity of near-surface magmatic processes. For this reason, much effort have been devoted to characterize the volatile evolution of shallow magmatic systems to better constrain volcanic history. Silicate melt inclusions (SMI) represent samples of melt that were isolated from the bulk magma at depth, thus preserving the PTX conditions of the pre-eruptive material. SMI are often affected by the formation of a bubble after trapping; this is a natural consequence of the PVTX properties of crystal-melt-volatile systems. Previous workers have recognized that bubble formation is an obstacle, which affects the interpretation of SMI trapping conditions based only on analysis of the glass phase. Indeed, they explained that bubbles can contain a significant percentage of the volatiles, particularly for those with low solubility in the melt (e.g. CO2). In this study, we propose to define the pre-eruptive PTX conditions of Los Humeros magma chamber using SMI from the various eruption events within 460 and 30 Ka. An innovative analytical coupling has been used in order to determine: (1) the volume of the SMI glass and bubble, using high resolution 3D X-ray microtomography; (2) the density and composition of the bubbles, using Raman spectroscopy; (3) the volatile element contents in glass, using NanoSIMS; and, (4) the major elements composition of the glass, using EPMA. The recalculated volatile concentrations of the total SMI (glass + bubble), illustrate clearly that the volatile content determinations using only the glass phase, underestimate drastically the total volatile content and therefore induce significant error on the determination of the pre-eruptive volcanic budget and on the constrain on the volcanic and thermal history. This study had moreover highlighted the complex evolution of Los Humeros composite magma chamber and, gave constrains for geothermal exploration purpose.

  8. Gintonin, newly identified compounds from ginseng, is novel lysophosphatidic acids-protein complexes and activates G protein-coupled lysophosphatidic acid receptors with high affinity.

    PubMed

    Hwang, Sung Hee; Shin, Tae-Joon; Choi, Sun-Hye; Cho, Hee-Jung; Lee, Byung-Hwan; Pyo, Mi Kyung; Lee, Jun-Ho; Kang, Jiyeon; Kim, Hyeon-Joong; Park, Chan-Woo; Shin, Ho-Chul; Nah, Seung-Yeol

    2012-02-01

    Recently, we isolated a subset of glycolipoproteins from Panax ginseng, that we designated gintonin, and demonstrated that it induced [Ca2+]i transients in cells via G protein-coupled receptor (GPCR) signaling pathway(s). However, active components responsible for Ca2+ mobilization and the corresponding receptor(s) were unknown. Active component(s) for [Ca2+]i transients of gintonin were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry and ion-mobility mass spectrometry, respectively. The corresponding receptor(s)were investigated through gene expression assays. We found that gintonin contains LPA C18:2 and other LPAs. Proteomic analysis showed that ginseng major latex-like protein and ribonuclease-like storage proteins are protein components of gintonin. Gintonin induced [Ca2+]i transients in B103 rat neuroblastoma cells transfected with human LPA receptors with high affinity in order of LPA2 >LPA5 > LPA1 > LPA3 > LPA4. The LPA1/LPA3 receptor antagonist Ki16425 blocked gintonin action in cells expressing LPA1 or LPA3. Mutations of binding sites in the LPA3 receptor attenuated gintonin action. Gintonin acted via pertussis toxin (PTX)-sensitive and -insensitive G protein-phospholipase C (PLC)-inositol 1,4,5-trisphosphate (IP3)-Ca2+ pathways. However, gintonin had no effects on other receptors examined. In human umbilical vein endothelial cells (HUVECs) gintonin stimulated cell proliferation and migration. Gintonin stimulated ERK1/2 phosphorylation. PTX blocked gintonin-mediated migration and ERK1/2 phosphorylation. In PC12 cells gintonin induced morphological changes, which were blocked by Rho kinase inhibitorY-27632. Gintonin contains GPCR ligand LPAs in complexes with ginseng proteins and could be useful in the development of drugs targeting LPA receptors.

  9. Hetero-oligomeric Complex between the G Protein-coupled Estrogen Receptor 1 and the Plasma Membrane Ca2+-ATPase 4b*

    PubMed Central

    Tran, Quang-Kim; VerMeer, Mark; Burgard, Michelle A.; Hassan, Ali B.; Giles, Jennifer

    2015-01-01

    The new G protein-coupled estrogen receptor 1 (GPER/GPR30) plays important roles in many organ systems. The plasma membrane Ca2+-ATPase (PMCA) is essential for removal of cytoplasmic Ca2+ and for shaping the time courses of Ca2+-dependent activities. Here, we show that PMCA and GPER/GPR30 physically interact and functionally influence each other. In primary endothelial cells, GPER/GPR30 agonist G-1 decreases PMCA-mediated Ca2+ extrusion by promoting PMCA tyrosine phosphorylation. GPER/GPR30 overexpression decreases PMCA activity, and G-1 further potentiates this effect. GPER/GPR30 knockdown increases PMCA activity, whereas PMCA knockdown substantially reduces GPER/GPR30-mediated phosphorylation of the extracellular signal-related kinase (ERK1/2). GPER/GPR30 co-immunoprecipitates with PMCA with or without treatment with 17β-estradiol, thapsigargin, or G-1. Heterologously expressed GPER/GPR30 in HEK 293 cells co-localizes with PMCA4b, the main endothelial PMCA isoform. Endothelial cells robustly express the PDZ post-synaptic density protein (PSD)-95, whose knockdown reduces the association between GPER/GPR30 and PMCA. Additionally, the association between PMCA4b and GPER/GPR30 is substantially reduced by truncation of either or both of their C-terminal PDZ-binding motifs. Functionally, inhibition of PMCA activity is significantly reduced by truncation of GPER/GPR30's C-terminal PDZ-binding motif. These data strongly indicate that GPER/GPR30 and PMCA4b form a hetero-oligomeric complex in part via the anchoring action of PSD-95, in which they constitutively affect each other's function. Activation of GPER/GPR30 further inhibits PMCA activity through tyrosine phosphorylation of the pump. These interactions represent cross-talk between Ca2+ signaling and GPER/GPR30-mediated activities. PMID:25847233

  10. Hetero-oligomeric Complex between the G Protein-coupled Estrogen Receptor 1 and the Plasma Membrane Ca2+-ATPase 4b.

    PubMed

    Tran, Quang-Kim; VerMeer, Mark; Burgard, Michelle A; Hassan, Ali B; Giles, Jennifer

    2015-05-22

    The new G protein-coupled estrogen receptor 1 (GPER/GPR30) plays important roles in many organ systems. The plasma membrane Ca(2+)-ATPase (PMCA) is essential for removal of cytoplasmic Ca(2+) and for shaping the time courses of Ca(2+)-dependent activities. Here, we show that PMCA and GPER/GPR30 physically interact and functionally influence each other. In primary endothelial cells, GPER/GPR30 agonist G-1 decreases PMCA-mediated Ca(2+) extrusion by promoting PMCA tyrosine phosphorylation. GPER/GPR30 overexpression decreases PMCA activity, and G-1 further potentiates this effect. GPER/GPR30 knockdown increases PMCA activity, whereas PMCA knockdown substantially reduces GPER/GPR30-mediated phosphorylation of the extracellular signal-related kinase (ERK1/2). GPER/GPR30 co-immunoprecipitates with PMCA with or without treatment with 17β-estradiol, thapsigargin, or G-1. Heterologously expressed GPER/GPR30 in HEK 293 cells co-localizes with PMCA4b, the main endothelial PMCA isoform. Endothelial cells robustly express the PDZ post-synaptic density protein (PSD)-95, whose knockdown reduces the association between GPER/GPR30 and PMCA. Additionally, the association between PMCA4b and GPER/GPR30 is substantially reduced by truncation of either or both of their C-terminal PDZ-binding motifs. Functionally, inhibition of PMCA activity is significantly reduced by truncation of GPER/GPR30's C-terminal PDZ-binding motif. These data strongly indicate that GPER/GPR30 and PMCA4b form a hetero-oligomeric complex in part via the anchoring action of PSD-95, in which they constitutively affect each other's function. Activation of GPER/GPR30 further inhibits PMCA activity through tyrosine phosphorylation of the pump. These interactions represent cross-talk between Ca(2+) signaling and GPER/GPR30-mediated activities.

  11. Improving the WRF model's (version 3.6.1) simulation over sea ice surface through coupling with a complex thermodynamic sea ice model (HIGHTSI)

    NASA Astrophysics Data System (ADS)

    Yao, Yao; Huang, Jianbin; Luo, Yong; Zhao, Zongci

    2016-06-01

    Sea ice plays an important role in the air-ice-ocean interaction, but it is often represented simply in many regional atmospheric models. The Noah sea ice scheme, which is the only option in the current Weather Research and Forecasting (WRF) model (version 3.6.1), has a problem of energy imbalance due to its simplification in snow processes and lack of ablation and accretion processes in ice. Validated against the Surface Heat Budget of the Arctic Ocean (SHEBA) in situ observations, Noah underestimates the sea ice temperature which can reach -10 °C in winter. Sensitivity tests show that this bias is mainly attributed to the simulation within the ice when a time-dependent ice thickness is specified. Compared with the Noah sea ice model, the high-resolution thermodynamic snow and ice model (HIGHTSI) uses more realistic thermodynamics for snow and ice. Most importantly, HIGHTSI includes the ablation and accretion processes of sea ice and uses an interpolation method which can ensure the heat conservation during its integration. These allow the HIGHTSI to better resolve the energy balance in the sea ice, and the bias in sea ice temperature is reduced considerably. When HIGHTSI is coupled with the WRF model, the simulation of sea ice temperature by the original Polar WRF is greatly improved. Considering the bias with reference to SHEBA observations, WRF-HIGHTSI improves the simulation of surface temperature, 2 m air temperature and surface upward long-wave radiation flux in winter by 6, 5 °C and 20 W m-2, respectively. A discussion on the impact of specifying sea ice thickness in the WRF model is presented. Consistent with previous research, prescribing the sea ice thickness with observational information results in the best simulation among the available methods. If no observational information is available, we present a new method in which the sea ice thickness is initialized from empirical estimation and its further change is predicted by a complex thermodynamic

  12. Electron Transfer and Proton-Coupled Electron Transfer Reactivity and Self-Exchange of Synthetic [2Fe–2S] Complexes: Models for Rieske and mitoNEET Clusters

    PubMed Central

    2015-01-01

    This report describes the thermochemistry, proton-coupled electron transfer (PCET) reactions and self-exchange rate constants for a set of bis-benzimidazolate-ligated [2Fe–2S] clusters. These clusters serve as a model for the chemistry of biological Rieske and mitoNEET clusters. PCET from [Fe2S2(Prbbim)(PrbbimH)]2– (4) and [Fe2S2(Prbbim)(PrbbimH2)]1– (5) to TEMPO occurs via concerted proton–electron transfer (CPET) mechanisms (PrbbimH2 = 4,4-bis-(benzimidazol-2-yl)heptane). Intermolecular electron transfer (ET) self-exchange between [Fe2S2(Prbbim)2]2– (1) and [Fe2S2(Prbbim)2]3– (2) occurs with a rate constant of (1.20 ± 0.06) × 105 M–1 s–1 at 26 °C. A similar self-exchange rate constant is found for the related [2Fe–2S] cluster [Fe2S2(SArO)2]2–/3–, SArO2– = thiosalicylate. These are roughly an order of magnitude slower than that reported for larger [4Fe–4S] clusters and 1 order of magnitude faster than that reported for N-ligated high-spin iron complexes. These results suggest that the rate of intermolecular ET to/from [Fe–S] clusters is modulated by cluster size. The measured PCET self-exchange rate constant for 1 and 4 at −30 °C is (3.8 ± 0.7) × 104 M–1 s–1. Analysis of rate constants using the Marcus cross-relation suggests that this process likely occurs via a concerted proton–electron transfer (CPET) mechanism. The implications of these findings to biological systems are also discussed, including the conclusion that histidine-ligated [2Fe–2S] clusters should not have a strong bias to undergo concerted e–/H+ transfers. PMID:24592857

  13. Bead-probe complex capture a couple of SINE and LINE family from genomes of two closely related species of East Asian cyprinid directly using magnetic separation.

    PubMed

    Tong, Chaobo; Guo, Baocheng; He, Shunping

    2009-02-19

    Short and long interspersed elements (SINEs and LINEs, respectively), two types of retroposons, are active in shaping the architecture of genomes and powerful tools for studies of phylogeny and population biology. Here we developed special protocol to apply biotin-streptavidin bead system into isolation of interspersed repeated sequences rapidly and efficiently, in which SINEs and LINEs were captured directly from digested genomic DNA by hybridization to bead-probe complex in solution instead of traditional strategy including genomic library construction and screening. A new couple of SINEs and LINEs that shared an almost identical 3'tail was isolated and characterized in silver carp and bighead carp of two closely related species. These SINEs (34 members), designated HAmo SINE family, were little divergent in sequence and flanked by obvious TSD indicated that HAmo SINE was very young family. The copy numbers of this family was estimated to 2 x 105 and 1.7 x 105 per haploid genome by Real-Time qPCR, respectively. The LINEs, identified as the homologs of LINE2 in other fishes, had a conserved primary sequence and secondary structures of the 3'tail region that was almost identical to that of HAmo SINE. These evidences suggest that HAmo SINEs are active and amplified recently utilizing the enzymatic machinery for retroposition of HAmoL2 through the recognition of higher-order structures of the conserved 42-tail region. We analyzed the possible structures of HAmo SINE that lead to successful amplification in genome and then deduced that HAmo SINE, SmaI SINE and FokI SINE that were similar in sequence each other, were probably generated independently and created by LINE family within the same lineage of a LINE phylogeny in the genomes of different hosts. The presented results show the advantage of the novel method for retroposons isolation and a pair of young SINE family and its partner LINE family in two carp fishes, which strengthened the hypotheses containing the

  14. Developmental coupling of larval and adult stages in a complex life cycle: insights from limb regeneration in the flour beetle, Tribolium castaneum

    PubMed Central

    2013-01-01

    Background A complex life cycle, such as complete metamorphosis, is a key innovation that can promote diversification of species. The evolution of a morphologically distinct larval stage is thought to have enabled insects to occupy broader ecological niches and become the most diverse metazoan taxon, yet the extent to which larval and adult morphologies can evolve independently remains unknown. Perturbation of larval limb regeneration allows us to generate larval legs and antennae with altered limb morphologies, which may be used to explore the developmental continuity that might exist between larval and adult appendages. In this study, we determined the roles of several appendage patterning transcription factors, abrupt (ab), dachshund (dac), Distal-less (Dll), and spineless (ss), in the red flour beetle, Tribolium castaneum, during larval appendage regeneration. The functions of these genes in regenerating and non-regenerating limbs were compared using RNA interference. Results During limb regeneration, dac and ss were necessary to re-pattern the same larval structures as those patterned during embryogenesis. Removal of these two genes led to larval appendage patterning defects that were carried over to the adult legs. Surprisingly, even though maternal knockdown of ab had minimal effects on limb allocation and patterning in the embryo, it was necessary for blastema growth, an earlier phase of regeneration. Finally, knockdown of Dll prevented the blastema-like bumps from re-differentiating into appendages. Conclusions Our results suggest that, similar to vertebrates, the re-patterning phase of Tribolium larval limb regeneration relies on the same genes that are used during embryonic limb patterning. Thus, the re-patterning phase of regeneration is likely to be regulated by taxon-specific patterning mechanisms. Furthermore, Ab and Dll appear to play important roles during blastema proliferation and re-differentiation, respectively. Finally, our results show that

  15. Bead-probe complex capture a couple of SINE and LINE family from genomes of two closely related species of East Asian cyprinid directly using magnetic separation

    PubMed Central

    Tong, Chaobo; Guo, Baocheng; He, Shunping

    2009-01-01

    Background Short and long interspersed elements (SINEs and LINEs, respectively), two types of retroposons, are active in shaping the architecture of genomes and powerful tools for studies of phylogeny and population biology. Here we developed special protocol to apply biotin-streptavidin bead system into isolation of interspersed repeated sequences rapidly and efficiently, in which SINEs and LINEs were captured directly from digested genomic DNA by hybridization to bead-probe complex in solution instead of traditional strategy including genomic library construction and screening. Results A new couple of SINEs and LINEs that shared an almost identical 3'tail was isolated and characterized in silver carp and bighead carp of two closely related species. These SINEs (34 members), designated HAmo SINE family, were little divergent in sequence and flanked by obvious TSD indicated that HAmo SINE was very young family. The copy numbers of this family was estimated to 2 × 105 and 1.7 × 105 per haploid genome by Real-Time qPCR, respectively. The LINEs, identified as the homologs of LINE2 in other fishes, had a conserved primary sequence and secondary structures of the 3'tail region that was almost identical to that of HAmo SINE. These evidences suggest that HAmo SINEs are active and amplified recently utilizing the enzymatic machinery for retroposition of HAmoL2 through the recognition of higher-order structures of the conserved 42-tail region. We analyzed the possible structures of HAmo SINE that lead to successful amplification in genome and then deduced that HAmo SINE, SmaI SINE and FokI SINE that were similar in sequence each other, were probably generated independently and created by LINE family within the same lineage of a LINE phylogeny in the genomes of different hosts. Conclusion The presented results show the advantage of the novel method for retroposons isolation and a pair of young SINE family and its partner LINE family in two carp fishes, which strengthened

  16. Dynamic coupling among channel flow, plateau growth, foreland shortening, and the formation of metamorphic core complexes: Application to the Tibetan plateau

    NASA Astrophysics Data System (ADS)

    Rey, P. F.; Teyssier, C.; Whitney, D. L.

    2009-04-01

    Gravitational potential energy stored in an orogenic plateau can be sufficiently strong to deform the surrounding region (foreland), hence contributing to both plateau growth and collapse. Gravity-driven channel flow from the plateau lower crust into the foreland lower crust, or channel extrusion, has been proposed as a main contributor to the eastward growth of the Tibetan plateau, possibly driving the lower crust channel as far as 1000 km beneath the foreland (eg. Royden et al., 2008). On the basis of numerical modeling using temperature-dependent viscosities and densities, we show that four processes impose severe limitations to channel extrusion: (1) cooling of the extruded channel, (2) convective motion in the plateau channel, (3) surface extension of the plateau, and (4) erosion of the plateau edge. Model results show that peak velocities in the extrusion channel drop rapidly (in less than a few My) from ca. 5 cm/year to less than 1 cm/year, owing to the rapid cooling in the channel from 750-850°C to 650-550°C as it travels into the foreland region. Channel flow extrusion is further slowed when convective flow initiates in the plateau channel as a result of only a few percent drop in density. This convection inhibits laminar flow in the channel, reduces the peak horizontal velocity in the channel to a few mm, and even drives a counter flow at the base of the channel, preventing its propagation toward the foreland. If the foreland is actively pulled away from the plateau (extending boundaries), the plateau upper crust undergoes extension and the lower crust moves up efficiently into a metamorphic core complex, which inhibits flow of the channel away from the plateau and even generates a counter flow from the foreland to the metamorphic core complex. If the foreland is fixed, the same phenomenon occurs as long as the foreland upper crust undergoes shortening (likely weakened by high pore fluid pressure), which enhances extension of the plateau and upward flow

  17. An assumption-violating application of the Lawrance-Knight deconvolution procedure: A retrieval of electronic coupling mechanisms underlying complex spectra

    NASA Astrophysics Data System (ADS)

    Altunata, Selen; Field, Robert W.

    2001-04-01

    The Lawrance-Knight (L-K) deconvolution method is a spectral inversion scheme which allows one to relate an absorption or a fluorescence spectrum to the energies and couplings of the zero-order states via analytical expressions. In order to obtain accurate results, the L-K method can only be applied to spectra that arise from one precisely defined zero-order picture. Namely, a single bright state must be coupled directly to a background of noninteracting dark states, the "direct coupling model." In most situations, the zero-order picture that gives rise to a particular absorption or a fluorescence spectrum is not known a priori. Nonetheless, it is typically assumed that the zero-order circumstances governing the spectral intensities are as described above, and the L-K method has been applied indiscriminantly to the spectra of a variety of systems such as pyrazine, acetylene, and naphthalene to extract zero-order parameters. We show here that if the L-K algorithm is applied to spectra where the underlying zero-order picture departs from the direct coupling limit, the resulting output has characteristic qualitative and quantitative features that reflect this situation. By applying the L-K method to a series of simulated spectra, we recover from a pattern of patterns new information about the couplings among the dark states. We have specifically considered the alternative picture of a single bright state coupled to a background of non-interacting states by a doorway-mediated mechanism. We demonstrate here that the L-K algorithm can be employed to distinguish between the contrasting doorway-mediated and direct coupling schemes, and also to obtain coupling matrix elements.

  18. Age Modulates Fe3O4 Nanoparticles Liver Toxicity: Dose-Dependent Decrease in Mitochondrial Respiratory Chain Complexes Activities and Coupling in Middle-Aged as Compared to Young Rats

    PubMed Central

    Baratli, Yosra; Charles, Anne-Laure; Wolff, Valérie; Ben Tahar, Lotfi; Smiri, Leila; Bouitbir, Jamal; Zoll, Joffrey; Sakly, Mohsen; Auger, Cyril; Vogel, Thomas; Abdelmelek, Hafedh; Geny, Bernard

    2014-01-01

    We examined the effects of iron oxide nanoparticles (IONPs) on mitochondrial respiratory chain complexes activities and mitochondrial coupling in young (3 months) and middle-aged (18 months) rat liver, organ largely involved in body iron detoxification. Isolated liver mitochondria were extracted using differential centrifugations. Maximal oxidative capacities (Vmax, complexes I, III, and IV activities), Vsucc (complexes II, III, and IV activities), and Vtmpd, (complex IV activity), together with mitochondrial coupling (Vmax/V0) were determined in controls conditions and after exposure to 250, 300, and 350 μg/ml Fe3O4 in young and middle-aged rats. In young liver mitochondria, exposure to IONPs did not alter mitochondrial function. In contrast, IONPs dose-dependently impaired all complexes of the mitochondrial respiratory chain in middle-aged rat liver: Vmax (from 30 ± 1.6 to 17.9 ± 1.5; P < 0.001), Vsucc (from 33.9 ± 1.7 to 24.3 ± 1.0; P < 0.01), Vtmpd (from 43.0 ± 1.6 to 26.3 ± 2.2 µmol O2/min/g protein; P < 0.001) using Fe3O4 350 µg/ml. Mitochondrial coupling also decreased. Interestingly, 350 μg/ml Fe3O4 in the form of Fe3+ solution did not impair liver mitochondrial function in middle-aged rats. Thus, IONPs showed a specific toxicity in middle-aged rats suggesting caution when using it in old age. PMID:24949453

  19. Spin-lattice relaxation of ligand nuclei in slowly reorienting paramagnetic complexes in the electronic doublet spin state ( S = {1}/{2}). A theoretical approach for strongly coupled two-spin systems

    NASA Astrophysics Data System (ADS)

    Benetis, Nikolas P.

    In this paper a general theory for treating the spin-lattice relaxation of a ligand nucleus (denoted by I) is derived for a metal complex in a doublet electron spin state ( S = {1}/{2}). The dipole-dipole SI interaction is treated for the case where the electron spin is also strongly coupled to the metal nucleus K. The SK interaction considered here is the hyperfine coupling, both scalar (SC) and dipolar (DD). The present theory is valid for slowly reorienting complexes in solution and can, furthermore, incorporate relaxation effects of the electron spin S, and the metal nucleus K due to processes which are faster than, and independent of, reorientation, i.e., for processes that fulfil the strong narrowing conditions. The effects of chemical exchange of the ligands and of anisotropic reorientation of the complex are also studied. Together with our previous studies of paramagnetic complexes with electron spin S ≧ 1, that have been recently reviewed by J. Kowalewski, L. Nordenskiöld, N. Benetis, and P. O. Westlund, ( Prog. NMR Spectrosc.17, 141 (1985)), the present work completes the elementary relaxation features of ligand nuclei of metal complexes in the slow motional regime. The present theory is shown to be more general than the theory of Bertini and co-workers ( J. Magn. Reson.59 , 213 (1984)), which can be obtained as a limit of the present approach by decoupling the reorientation from the motions of the S-K two spin system. The treatment of a strongly coupled two-spin system is emphasized since it provides a necessary step to the treatment of the relaxation of paramagnetic doublets.

  20. AlAr3(THF): highly efficient reagents for cross-couplings with aryl bromides and chlorides catalyzed by the economic palladium complex of PCy3.

    PubMed

    Ku, Shih-Lun; Hui, Xin-Ping; Chen, Chien-An; Kuo, Yi-Ying; Gau, Han-Mou

    2007-10-07

    Novel and highly efficient cross couplings of aryl bromides and chlorides with AlAr3(THF) (Ar = Ph, 2,4,6-Me3C6H2, 2-naphthyl or 4-Me3SiC6H4) catalyzed by the economic palladium catalyst of PCy3 are reported without the use of a base and under mild reaction conditions at room temperature or temperatures < or = 60 degrees C even for couplings of bulky aryl halides and the Al(2,4,6-Me3C6H2)3(THF) reagent.

  1. Superexchange contributions to distance dependence of electron transfer/transport: exchange and electronic coupling in oligo(para-phenylene)- and oligo(2,5-thiophene)-bridged donor-bridge-acceptor biradical complexes.

    PubMed

    Kirk, Martin L; Shultz, David A; Stasiw, Daniel E; Lewis, Geoffrey F; Wang, Guangbin; Brannen, Candice L; Sommer, Roger D; Boyle, Paul D

    2013-11-13

    The preparation and characterization of three new donor-bridge-acceptor biradical complexes are described. Using variable-temperature magnetic susceptibility, EPR hyperfine coupling constants, and the results of X-ray crystal structures, we evaluate both exchange and electronic couplings as a function of bridge length for two quintessential molecular bridges: oligo(para-phenylene), β = 0.39 Å(-1) and oligo(2,5-thiophene), β = 0.22 Å(-1). This report represents the first direct comparison of exchange/electronic couplings and distance attenuation parameters (β) for these bridges. The work provides a direct measurement of superexchange contributions to β, with no contribution from incoherent hopping. The different β values determined for oligo(para-phenylene) and oligo(2,5-thiophene) are due primarily to the D-B energy gap, Δ, rather than bridge-bridge electronic couplings, H(BB). This is supported by the fact that the H(BB) values extracted from the experimental data for oligo(para-phenylene) (H(BB) = 11,400 cm(-1)) and oligo(2,5-thiophene) (12,300 cm(-1)) differ by <10%. The results presented here offer unique insight into the intrinsic molecular factors that govern H(DA) and β, which are important for understanding the electronic origin of electron transfer and electron transport mediated by molecular bridges.

  2. Homogeneous and heterogenized Au(III) Schiff base-complexes as selective and general catalysts for self-coupling of aryl boronic acids.

    PubMed

    González-Arellano, C; Corma, A; Iglesias, M; Sánchez, F

    2005-04-21

    A series of homogeneous and heterogenized gold metal complexes show high activity and selectivity for the homocoupling of a large variety of aryl boronic acids, being of general utility for the synthesis of C2-symmetric biaryls.

  3. Spectroscopic and magnetic studies of erbium(III)-TEMPO complex as a potential single-molecule magnet: Interplay of the crystal-field and exchange coupling effects

    NASA Astrophysics Data System (ADS)

    Karbowiak, Mirosław; Rudowicz, Czesław; Nakamura, Takeshi; Murakami, Rina; Ishida, Takayuki

    2016-10-01

    Crystallographic, spectroscopic, and magnetic studies of three-center systems: lanthanoid-Ln3+ ions doubly-coordinated by TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals [Ln-TEMPO2] are reported. The temperature dependence of alternating-current magnetic susceptibility indicates the single-molecule-magnet behavior of Er-TEMPO2, exhibiting relatively slow magnetization relaxation. Well-resolved absorption spectra were obtained only for Er-TEMPO2. Other samples yielded spectra not amenable for meaningful interpretation. The crystal-field parameters (CFPs) determined from the measured Er3+-energy levels served as starting CFPs for fitting the direct-current magnetic susceptibility result. Compatibility of the so-determined and fine-tuned CFPs, and interplay between crystal-field-related effects and exchange-coupling effects are considered. Exchange couplings in Ln-TEMPO2 appear antiferromagnetic and unexpectedly large.

  4. The (CH2)2O-H2O hydrogen bonded complex. Ab Initio calculations and Fourier transform infrared spectroscopy from neon matrix and a new supersonic jet experiment coupled to the infrared AILES beamline of synchrotron SOLEIL.

    PubMed

    Cirtog, M; Asselin, P; Soulard, P; Tremblay, B; Madebène, B; Alikhani, M E; Georges, R; Moudens, A; Goubet, M; Huet, T R; Pirali, O; Roy, P

    2011-03-31

    A series of hydrogen bonded complexes involving oxirane and water molecules have been studied. In this paper we report on the vibrational study of the oxirane-water complex (CH(2))(2)O-H(2)O. Neon matrix experiments and ab initio anharmonic vibrational calculations have been performed, providing a consistent set of vibrational frequencies and anharmonic coupling constants. The implementation of a new large flow supersonic jet coupled to the Bruker IFS 125 HR spectrometer at the infrared AILES beamline of the French synchrotron SOLEIL (Jet-AILES) enabled us to record first jet-cooled Fourier transform infrared spectra of oxirane-water complexes at different resolutions down to 0.2 cm(-1). Rovibrational parameters and a lower bound of the predissociation lifetime of 25 ps for the v(OH)(b) = 1 state have been derived from the rovibrational analysis of the ν(OH)(b) band contour recorded at respective rotational temperatures of 12 K (Jet-AILES) and 35 K (LADIR jet).

  5. Carbon-carbon cross-coupling reactions catalyzed by a two-coordinate nickel(II)-bis(amido) complex via observable Ni(I) , Ni(II) , and Ni(III) intermediates.

    PubMed

    Lipschutz, Michael I; Tilley, T Don

    2014-07-07

    Recently, the development of more sustainable catalytic systems based on abundant first-row metals, especially nickel, for cross-coupling reactions has attracted significant interest. One of the key intermediates invoked in these reactions is a Ni(III) -alkyl species, but no such species that is part of a competent catalytic cycle has yet been isolated. Herein, we report a carbon-carbon cross-coupling system based on a two-coordinate Ni(II) -bis(amido) complex in which a Ni(III) -alkyl species can be isolated and fully characterized. This study details compelling experimental evidence of the role played by this Ni(III) -alkyl species as well as those of other key Ni(I) and Ni(II) intermediates. The catalytic cycle described herein is also one of the first examples of a two-coordinate complex that competently catalyzes an organic transformation, potentially leading to a new class of catalysts based on the unique ability of first-row transition metals to accommodate two-coordinate complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. High performance of a cobalt–nitrogen complex for the reduction and reductive coupling of nitro compounds into amines and their derivatives

    PubMed Central

    Zhou, Peng; Jiang, Liang; Wang, Fan; Deng, Kejian; Lv, Kangle; Zhang, Zehui

    2017-01-01

    Replacement of precious noble metal catalysts with low-cost, non-noble heterogeneous catalysts for chemoselective reduction and reductive coupling of nitro compounds holds tremendous promise for the clean synthesis of nitrogen-containing chemicals. We report a robust cobalt–nitrogen/carbon (Co–Nx/C-800-AT) catalyst for the reduction and reductive coupling of nitro compounds into amines and their derivates. The Co–Nx/C-800-AT catalyst was prepared by the pyrolysis of cobalt phthalocyanine–silica colloid composites and the subsequent removal of silica template and cobalt nanoparticles. The Co–Nx/C-800-AT catalyst showed extremely high activity, chemoselectivity, and stability toward the reduction of nitro compounds with H2, affording full conversion and >97% selectivity in water after 1.5 hours at 110°C and under a H2 pressure of 3.5 bar for all cases. The hydrogenation of nitrobenzene over the Co–Nx/C-800-AT catalyst can even be smoothly performed under very mild conditions (40°C and a H2 pressure of 1 bar) with an aniline yield of 98.7%. Moreover, the Co–Nx/C-800-AT catalyst has high activity toward the transfer hydrogenation of nitrobenzene into aniline and the reductive coupling of nitrobenzene into other derivates with high yields. These processes were carried out in an environmentally friendly manner without base and ligands. PMID:28232954

  7. The coupling of cerebral blood flow and oxygen metabolism with brain activation is similar for simple and complex stimuli in human primary visual cortex.

    PubMed

    Griffeth, Valerie E M; Simon, Aaron B; Buxton, Richard B

    2015-01-01

    Quantitative functional MRI (fMRI) experiments to measure blood flow and oxygen metabolism coupling in the brain typically rely on simple repetitive stimuli. Here we compared such stimuli with a more naturalistic stimulus. Previous work on the primary visual cortex showed that direct attentional modulation evokes a blood flow (CBF) response with a relatively large oxygen metabolism (CMRO2) response in comparison to an unattended stimulus, which evokes a much smaller metabolic response relative to the flow response. We hypothesized that a similar effect would be associated with a more engaging stimulus, and tested this by measuring the primary human visual cortex response to two contrast levels of a radial flickering checkerboard in comparison to the response to free viewing of brief movie clips. We did not find a significant difference in the blood flow-metabolism coupling (n=%ΔCBF/%ΔCMRO2) between the movie stimulus and the flickering checkerboards employing two different analysis methods: a standard analysis using the Davis model and a new analysis using a heuristic model dependent only on measured quantities. This finding suggests that in the primary visual cortex a naturalistic stimulus (in comparison to a simple repetitive stimulus) is either not sufficient to provoke a change in flow-metabolism coupling by attentional modulation as hypothesized, that the experimental design disrupted the cognitive processes underlying the response to a more natural stimulus, or that the technique used is not sensitive enough to detect a small difference.

  8. Energy-Storage Applications for a pH Gradient between Two Benzimidazole-Ligated Ruthenium Complexes That Engage in Proton-Coupled Electron-Transfer Reactions in Solution.

    PubMed

    Motoyama, Daisuke; Yoshikawa, Kai; Ozawa, Hiroaki; Tadokoro, Makoto; Haga, Masa-Aki

    2017-06-05

    The judicious selection of pairs of benzimidazole-ligated ruthenium complexes allowed the construction of a rechargeable proton-coupled electron-transfer (PCET)-type redox battery. A series of ruthenium(II) and -(III) complexes were synthesized that contain substituted benzimidazoles that engage in PCET reactions. The formation of intramolecular Ru-C cyclometalation bonds stabilized the resulting ruthenium(III) complexes, in which pKa values of the imino N-H protons on the benzimidazoles are usually lower than those for the corresponding ruthenium(II) complexes. As a proof-of-concept study for a solution redox battery based on such PCET reactions, the charging/discharging cycles of several pairs of ruthenium complexes were examined by chronopotentiometry in an H-type device with half-cells separated by a Nafion membrane in unbuffered CH3CN/H2O (1/1, v/v) containing 0.1 M NaCl. During the charging/discharging cycles, the pH value of the solution gradually changed accompanied by a change of the open-circuit potential (OCP). The changes for the OCP and pH value of the solution in the anodic and cathodic half-cells were in good agreement with the predicted values from the Pourbaix diagrams for the pairs of ruthenium complexes used. Accordingly, the careful selection of pairs of ruthenium complexes with a sufficient potential gradient and a suitably large pKa difference is crucial: the charge generated between the two ruthenium complexes changes the OCP and the pH difference between the two cells in an unbuffered solution, given that the PCET reactions occur at both electrodes and that discharging leads to the original state. Because the electric energy is stored as a pH gradient between the half-cells, new possibilities for PCET-type rocking-chair redox batteries arise.

  9. Roles of subunit NuoL in the proton pumping coupling mechanism of NADH:ubiquinone oxidoreductase (complex I) fro