Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Environ Plan A ; 55(7): 1799-1804, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37969422

RESUMO

The article introduces a book forum on Isabella Weber's book, "How China Escaped Shock Therapy." The book is notable not only for the way that it reinterprets, substantively and theoretically, the story of China's world-altering economic transformation, but also for the truly original kind of book that it is.

2.
Environ Plan A ; 55(3): 621-635, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37180846

RESUMO

The theme issue 'Making Space for the New State Capitalism' brings together insights from critical economic geography and heterodox political economy through a series of papers published in three installments, each accompanied by an introductory essay written by the guest editors. In this, the second of these introductory commentaries, we explore the consequences of embracing relationality, spatiotemporality and uneven development, together with the second group of papers. Introducing a final group of papers, the third installment will address the challenges and opportunities of thinking conjuncturally.

3.
Phys Chem Chem Phys ; 22(11): 6326-6334, 2020 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-32134067

RESUMO

This paper reports measurements of the temperature dependence of the rate constants for H-atom abstraction reactions from propane and n-butane by the light isotopic H-atom muonium (Mu), kMu(T), over temperatures in the range 300 K to 435 K. Simple Arrhenius fits to these data yield activation energies, E, that are some 2-4 times lower than E found from corresponding fits for the H + propane and H + n-butane reactions studied elsewhere, both experimentally and theoretically, and fit over a similar temperature range. These activation energies E are also much lower than estimated from zero-point-energy corrected vibrationally adiabatic potential barriers, both results suggesting that quantum tunneling plays an important role in determining kMu(T) and for the Mu + propane reaction in particular. The results are expected to pose a considerable challenge to reaction rate theory for isotopic H-atom reactions in alkane systems.

4.
Angew Chem Int Ed Engl ; 55(47): 14580-14583, 2016 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-27739628

RESUMO

The chemistry of metal hydrides is implicated in a range of catalytic processes at metal centers. Gaining insight into the formation of such sites by protonation and/or electronation is therefore of significant value in fully exploiting the potential of such systems. Here, we show that the muonium radical (Mu. ), used as a low isotopic mass analogue of hydrogen, can be exploited to probe the early stages of hydride formation at metal centers. Mu. undergoes the same chemical reactions as H. and can be directly observed due to its short lifetime (in the microseconds) and unique breakdown signature. By implanting Mu. into three models of the [FeFe]-hydrogenase active site we have been able to detect key muoniated intermediates of direct relevance to the hydride chemistry of these systems.

5.
Langmuir ; 32(3): 664-72, 2016 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-26716949

RESUMO

The transfer rate of a probe molecule across the interfacial layer of a water-in-oil (w/o) microemulsion was investigated using a combination of transverse field muon spin rotation (TF-µSR), avoided level crossing muon spin resonance (ALC-µSR), and Monte Carlo simulations. Reverse microemulsions consist of nanometer-sized water droplets dispersed in an apolar solvent separated by a surfactant monolayer. Although the thermodynamic, static model of these systems has been well described, our understanding of their dynamics is currently incomplete. For example, what is the rate of solute transfer between the aqueous and apolar solvents, and how this is influenced by the structure of the interface? With an appropriate choice of system and probe molecule, µSR offers a unique opportunity to directly probe these interfacial transfer dynamics. Here, we have employed a well characterized w/o microemulsion stabilized by bis(2-ethylhexyl) sodium sulfosuccinate (Aerosol OT), with allyl alcohol (CH2═CH-CH2-OH, AA) as the probe. Resonances due to both muoniated radicals, CMuH2-C*H-CH2-OH and C*H2-CHMu-CH2-OH, were observed with the former being the dominant species. All resonances displayed solvent dependence, with those in the microemulsion observed as a single resonance located at intermediate magnetic fields to those present in either of the pure solvents. Observation of a single resonance is strong evidence for interfacial transfer being in the fast exchange limit. Monte Carlo calculations of the ΔM = 0 ALC resonances are consistent with the experimental data, indicating exchange rates greater than 10(9) s(-1), placing the rate of interfacial transfer at the diffusion limit.

6.
J Am Chem Soc ; 133(46): 18606-9, 2011 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-22035325

RESUMO

Paramagnetic hydrides are likely intermediates in hydrogen-evolving enzymic and molecular systems. Herein we report the first spectroscopic characterization of well-defined paramagnetic bridging hydrides. Time-resolved FTIR spectroelectrochemical experiments on a subsecond time scale revealed that single-electron transfer to the µ-hydride di-iron dithiolate complex 1 generates a 37-electron valence-delocalized species with no gross structural reorganization of the coordination sphere. DFT calculations support and (1)H and (2)H EPR measurements confirmed the formation an S = ½ paramagnetic complex (g = 2.0066) in which the unpaired spin density is essentially symmetrically distributed over the two iron atoms with strong hyperfine coupling to the bridging hydride (A(iso) = -75.8 MHz).


Assuntos
Hidrogênio/química , Ferro/química , Magnetismo , Compostos Organometálicos/química , Teoria Quântica , Enxofre/química , Catálise , Modelos Moleculares , Estrutura Molecular , Espectroscopia de Infravermelho com Transformada de Fourier
7.
J Am Chem Soc ; 133(4): 1112-21, 2011 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-21182249

RESUMO

The reactivity of protein bound iron-sulfur clusters with nitric oxide (NO) is well documented, but little is known about the actual mechanism of cluster nitrosylation. Here, we report studies of members of the Wbl family of [4Fe-4S] containing proteins, which play key roles in regulating developmental processes in actinomycetes, including Streptomyces and Mycobacteria, and have been shown to be NO responsive. Streptomyces coelicolor WhiD and Mycobacterium tuberculosis WhiB1 react extremely rapidly with NO in a multiphasic reaction involving, remarkably, 8 NO molecules per [4Fe-4S] cluster. The reaction is 10(4)-fold faster than that observed with O(2) and is by far the most rapid iron-sulfur cluster nitrosylation reaction reported to date. An overall stoichiometry of [Fe(4)S(4)(Cys)(4)](2-) + 8NO → 2[Fe(I)(2)(NO)(4)(Cys)(2)](0) + S(2-) + 3S(0) has been established by determination of the sulfur products and their oxidation states. Kinetic analysis leads to a four-step mechanism that accounts for the observed NO dependence. DFT calculations suggest the possibility that the nitrosylation product is a novel cluster [Fe(I)(4)(NO)(8)(Cys)(4)](0) derived by dimerization of a pair of Roussin's red ester (RRE) complexes.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Ferro/metabolismo , Óxido Nítrico/metabolismo , Processamento de Proteína Pós-Traducional , Enxofre/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo , Animais , Bovinos , Modelos Moleculares , Conformação Proteica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...