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991.
Xenia Engelmann Deesha D. Malik Teresa Corona Katrin Warm Erik R. Farquhar Marcel Swart Wonwoo Nam Kallol Ray 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4052-4056
The generation of a nonheme oxoiron(IV) intermediate, [(cyclam)FeIV(O)(CH3CN)]2+ ( 2 ; cyclam=1,4,8,11‐tetraazacyclotetradecane), is reported in the reactions of [(cyclam)FeII]2+ with aqueous hydrogen peroxide (H2O2) or a soluble iodosylbenzene (sPhIO) as a rare example of an oxoiron(IV) species that shows a preference for epoxidation over allylic oxidation in the oxidation of cyclohexene. Complex 2 is kinetically and catalytically competent to perform the epoxidation of olefins with high stereo‐ and regioselectivity. More importantly, 2 is likely to be the reactive intermediate involved in the catalytic epoxidation of olefins by [(cyclam)FeII]2+ and H2O2. In spite of the predominance of the oxoiron(IV) cores in biology, the present study is a rare example of high‐yield isolation and spectroscopic characterization of a catalytically relevant oxoiron(IV) intermediate in chemical oxidation reactions. 相似文献
992.
Nava Núñez M. Y. Martínez-de la Cruz A. López-Cuéllar E. 《Research on Chemical Intermediates》2019,45(3):1475-1492
Research on Chemical Intermediates - BiOI microspheres were synthesized by using mild conditions under microwave irradiation and applying short reaction times. The effect of the reaction medium in... 相似文献
993.
Iván Ayuso-Fernández Dr. Antonio L. De Lacey Prof. Dr. Francisco J. Cañada Dr. Francisco J. Ruiz-Dueñas Prof. Dr. Angel T. Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2708-2712
To investigate how ligninolytic peroxidases acquired the uniquely high redox potential they show today, their ancestors were resurrected and characterized. Unfortunately, the transient Compounds I (CI) and II (CII) from peroxide activation of the enzyme resting state (RS) are unstable. Therefore, the reduction potentials (E°′) of the three redox couples (CI/RS, CI/CII and CII/RS) were estimated (for the first time in a ligninolytic peroxidase) from equilibrium concentrations analyzed by stopped-flow UV/Vis spectroscopy. Interestingly, the E°′ of rate-limiting CII reduction to RS increased 70 mV from the common peroxidase ancestor to extant lignin peroxidase (LiP), and the same boost was observed for CI/RS and CI/CII, albeit with higher E°′ values. A straightforward correlation was found between the E°′ value and the progressive displacement of the proximal histidine Hϵ1 chemical shift in the NMR spectra, due to the higher paramagnetic effect of the heme Fe3+. More interestingly, the E°′ and NMR data also correlated with the evolutionary time, revealing that ancestral peroxidases increased their reduction potential in the evolution to LiP thanks to molecular rearrangements in their heme pocket during the last 400 million years. 相似文献
994.
Herrejón-Escutia Martín Solorio-Díaz Gildardo Vergara-Hernández Héctor Javier López-Martínez Edgar Vázquez-Gómez Octavio 《Journal of Thermal Analysis and Calorimetry》2019,137(2):399-410
Journal of Thermal Analysis and Calorimetry - A model was developed to predict the formation of austenite and dilatometric behavior during continuous heating in AISI 1045 steel, which has an... 相似文献
995.
Bartomeu Galmés Daniel Martínez Maria F. Infante-Carrió Dr. Antonio Franconetti Prof. Dr. Antonio Frontera 《Chemphyschem》2019,20(9):1135-1144
This article analyzes the interplay between nitro's π-hole and halogen–bonding (XB) interactions in nitroarenes. Remarkable cooperativity effects are observed when π–hole and XB interactions coexist in the same complex. The nitroarene presents two π-holes, one approximately over the N atom of the nitro group and the other over the aromatic ring, being the former more positive. The interplay between both interactions has been analyzed in terms of energetic and geometric features of the complexes, which are computed at the RI-MP2/def2-TZVPD level of theory. Molecular electrostatic potential (MEP) surface calculations have been used to explore the variation of the MEP values at the π-hole upon the formation of halogen bonding interactions between the nitroarene and CF3X (X=Cl, Br and I) molecules. In addition, the Bader's theory of atoms in molecules” (AIM) is used to characterize the interactions by means of the distribution of bond critical points and bond paths and to analyze their strengthening or weakening depending upon the variation of charge density at critical points. The aforementioned computational methods are adequate to examine how these interactions mutually influence each other. Natural bond orbital (NBO) and noncovalent interaction plot (NCIPlot) computational tools have been also used in some representative complexes to further analyze cooperativity effects. Finally, the Cambridge Structural Database (CSD) is used to provide some experimental evidence. 相似文献
996.
Alén B Fuster D Muñoz-Matutano G Martínez-Pastor J González Y Canet-Ferrer J González L 《Physical review letters》2008,101(6):067405
We study the metal-insulator transition in individual self-assembled quantum wires and report optical evidence of metallic liquid condensation at low temperatures. First, we observe that the temperature and power dependence of the single nanowire photoluminescence follow the evolution expected for an electron-hole liquid in one dimension. Second, we find novel spectral features that suggest that in this situation the expanding liquid condensate compresses the exciton gas in real space. Finally, we estimate the critical density and critical temperature of the phase transition diagram at n{c} approximately 1 x 10;{5} cm;{-1} and T{c} approximately 35 K, respectively. 相似文献
997.
Rentenier A Ruiz LF Díaz-Tendero S Zarour B Moretto-Capelle P Bordenave-Montesquieu D Bordenave-Montesquieu A Hervieux PA Alcamí M Politis MF Hanssen J Martín F 《Physical review letters》2008,100(18):183401
We have determined absolute charge transfer and fragmentation cross sections in He2++C60 collisions in the impact-energy range 0.1-250 keV by using a combined experimental and theoretical approach. We have found that the cross sections for the formation of He+ and He0 are comparable in magnitude, which cannot be explained by the sole contribution of pure single and double electron capture but also by contribution of transfer-ionization processes that are important even at low impact energies. The results show that multifragmentation is important only at impact energies larger than 40 keV; at lower energies, sequential C2 evaporation is the dominant process. 相似文献
998.
Horner DA Miyabe S Rescigno TN McCurdy CW Morales F Martín F 《Physical review letters》2008,101(18):183002
Recent experiments on double photoionization of H2 with photon energies between 160 and 240 eV have revealed body-frame angular distributions that suggest classical two-slit interference effects may be present when one electron carries most of the available energy and the second electron is not observed. We report precise quantum mechanical calculations that reproduce the experimental findings. They reveal that the interpretation in terms of classical diffraction is only appropriate at substantially higher photon energies. At the energies considered in the experiment we offer an alternative explanation based on the mixing of two nondiffractive contributions by circularly polarized light. 相似文献
999.
In this work, erythrocytes from carp were used as a nucleated cell model to test the hypothesis that the phthalocyanines (zinc - ZnPc and chloroaluminium -AlClPc) enhance ultrasonically induced damage in vitro. In order to confirm and complete our earlier investigation, the influence of ultrasound (US) and phthalocyanines (Pcs) on unresearched cellular components, was studied. Red blood cells were exposed to 1 MHz continuous ultrasound wave (0.61 and/or 2.44 W/cm2) in the presence or absence of phthalocyanines (3 μM). To identify target cell damage, we studied hemolysis, membrane fluidity and morphology of erythrocytes. To demonstrate the changes in the fluidity of plasma membrane we used the spectrofluorimetric methods using two fluorescence probes: 1-[4-(trimethylamino)phenyl]-6-phenyl-1,3,5,-hexatriene (TMA-DPH) and 1,6-diphenyl-1,3,5-hexatriene (DPH). The effect of US and Pcs on nucleated erythrocytes morphology was estimated on the basis of microscopic observation.The enhancement of ultrasonically induced membrane damage by both phthalocyanines was observed in case of hemolysis, and membrane surface fluidity, in comparison to ultrasound. The authors also observed changes in the morphology of erythrocytes. The obtained results support the hypothesis that the Pcs enhance ultrasonically induced cell damage in vitro.Furthermore, the influence of ultrasound on phthalocyanines (Pcs) in medium and in cells was tested. The authors observed changes in the phthalocyanines absorption spectra in the medium and the increase in the intensity of phthalocyanines fluorescence in the cells. These data can suggest changes in the structure of phthalocyanines after ultrasound action. 相似文献
1000.
E. Martínez J. Marian M.H. Kalos J.M. Perlado 《Journal of computational physics》2008,227(8):3804-3823
A novel parallel kinetic Monte Carlo (kMC) algorithm formulated on the basis of perfect time synchronicity is presented. The algorithm is intended as a generalization of the standard n-fold kMC method, and is trivially implemented in parallel architectures. In its present form, the algorithm is not rigorous in the sense that boundary conflicts are ignored. We demonstrate, however, that, in their absence, or if they were correctly accounted for, our algorithm solves the same master equation as the serial method. We test the validity and parallel performance of the method by solving several pure diffusion problems (i.e. with no particle interactions) with known analytical solution. We also study diffusion-reaction systems with known asymptotic behavior and find that, for large systems with interaction radii smaller than the typical diffusion length, boundary conflicts are negligible and do not affect the global kinetic evolution, which is seen to agree with the expected analytical behavior. Our method is a controlled approximation in the sense that the error incurred by ignoring boundary conflicts can be quantified intrinsically, during the course of a simulation, and decreased arbitrarily (controlled) by modifying a few problem-dependent simulation parameters. 相似文献