A new pathway for heterogenization of molecular catalysts by non-covalent interactions with carbon nanoreactors

A novel approach to heterogenisation of catalytic molecules is demonstrated using the nanoscale graphitic step-edges inside hollow graphitised carbon nanofibres (GNFs). The presence of the fullerene C60 moiety within a fullerene-salen CuII complex is essential for anchoring the catalyst within the GNF nanoreactor as demonstrated by comparison with the analogous catalyst complex without the fullerene group. The presence of the catalyst at the step-edges of the GNFs is confirmed by high resolution transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) with UV/Vis spectroscopy demonstrating only negligible (c.a. 3 %) desorption of the fullerene-salen CuII complex from the GNFs into solution under typical reaction conditions. The catalyst immobilised in GNFs shows good catalytic activity and selectivity towards styrene epoxidation, comparable to the analogous catalyst in solution. Moreover, the fullerene-salen CuII complex in GNFs demonstrates excellent stability and recyclability as it can be readily separated from the reaction mixture and employed in multiple reaction cycles with minimal loss of activity, which is highly advantageous compared to catalysts not stabilised by the graphitic step-edges that desorb rapidly from GNFs

Tuning the interactions between electron spins in fullerene-based triad systems

A series of six fullerene-linker-fullerene triads have been prepared by the stepwise addition of the fullerene cages to bridging moieties thus allowing the systematic variation of fullerene cage (C60 or C70) and linker (oxalate or terephthalate) and enabling precise control over the inter-fullerene separation. The fullerene triads exhibit good solubility in common organic solvents, have linear geometries and are diastereomerically pure. Cyclic voltammetric measurements demonstrate the excellent electron accepting capacity of all triads, with up to 6 electrons taken up per molecule in the potential range between -2.3 and 0.2 V (vs. Fc+/Fc). No significant electronic interactions between fullerene cages are observed in the ground state indicating that the individual properties of each C60 or C70 cage are retained within the triads. The electron-electron interactions in the electrochemically generated dianions of these triads, with one electron per fullerene cage were studied by EPR spectroscopy. The nature of electron-electron coupling observed at 77 K can be described as an equilibrium between a doublet and triplet state biradical which depends on the interfullerene spacing. The shorter oxalate-bridged triads exhibit stronger spin-spin coupling with triplet character, while in the longer terephthalate-bridged triads the intramolecular spin-spin coupling is significantly reduced

Human base excision repair enzymes apurinic/apyrimidinic endonuclease1 (APE1), DNA polymerase β and poly(ADP-ribose) polymerase 1: interplay between strand-displacement DNA synthesis and proofreading exonuclease activity

We examined interactions between base excision repair (BER) DNA intermediates and purified human BER enzymes, DNA polymerase β (pol β), apurinic/apyrimidinic endonuclease (APE1) and poly(ADP-ribose) polymerase-1 (PARP-1). Studies under steady-state conditions with purified BER enzymes and BER substrates have already demonstrated interplay between these BER enzymes that is sensitive to the respective concentrations of each enzyme. Therefore, in this study, using conditions of enzyme excess over substrate DNA, we further examine the question of interplay between BER enzymes on BER intermediates. The results reveal several important differences compared with data obtained using steady-state assays. Excess PARP-1 antagonizes the action of pol β, producing a complete block of long patch BER strand-displacement DNA synthesis. Surprisingly, an excess of APE1 stimulates strand-displacement DNA synthesis by pol β, but this effect is blocked by PARP-1. The APE1 exonuclease function appears to be modulated by the other BER proteins. Excess APE1 over pol β may allow APE1 to perform both exonuclease function and stimulation of strand-displacement DNA synthesis by pol β. This enables pol β to mediate long patch sub-pathway. These results indicate that differences in the stoichiometry of BER enzymes may regulate BER

All-fullerene-based cells for nonaqueous redox flow batteries

Redox flow batteries have the potential to revolutionize our use of intermittent sustainable energy sources such as solar and wind power by storing the energy in liquid electrolytes. Our concept study utilizes a novel electrolyte system, exploiting derivatized fullerenes as both anolyte and catholyte species in a series of battery cells, including a symmetric, single species system which alleviates the common problem of membrane crossover. The prototype multielectron system, utilizing molecular based charge carriers, made from inexpensive, abundant, and sustainable materials, principally, C and Fe, demonstrates remarkable current and energy densities and promising long-term cycling stability

Comparison of alkene hydrogenation in carbon nanoreactors of different diameters: probing the effects of nanoscale confinement on ruthenium nanoparticle catalysis

The catalytic properties of ruthenium nanoparticles (RuNPs) supported in carbon nanoreactors of different diameters – single walled carbon nanotubes (SWNTs, width of cavity 1.5 nm) and hollow graphitised nanofibers (GNFs, width of cavity 50-70 nm) – were evaluated using exploratory alkene hydrogenation reactions and compared to RuNPs adsorbed on the surface of SWNT or deposited on carbon black in commercially available Ru/C. Supercritical CO2 is shown to be essential to enable efficient transport of reactants to the catalytic RuNPs, particularly for the very narrow RuNP@SWNT nanoreactors. Though the RuNPs in SWNT are observed to be highly active, they simultaneously reduce the accessible volume of very narrow SWNTs by 30-40 % resulting in lower overall turnover numbers (TONs). In contrast, RuNPs confined in wider GNFs were completely accessible and demonstrated remarkable activity compared to unconfined RuNPs on the outer surface of SWNTs or carbon black. Control of the nanoscale environment around the catalytic RuNPs significantly enhances the stability of the catalyst and influences the local concentration of reactant molecules in close proximity to the RuNPs, illustrating the comparable importance of confinement to that of metal loading and size of NPs in the catalyst. Interestingly, extreme spatial confinement also appeared not to be the best strategy for controlling the selectivity of hydrogenations in a competitive reaction of norbornene and benzonorbornadiene, with wider RuNP@GNF nanoreactors displaying enhanced selectivity for the hydrogenation of the aromatic group containing alkene (benzonorbornadiene). This is attributed to the presence of nanoscale graphitic step-edges within the GNF making them an attractive alternative to the extremely narrow SWNT nanoreactors for preparative catalysis

Creation of a library of induced pluripotent stem cells from Parkinsonian patients.

Induced pluripotent stem cells (iPSCs) are becoming an important source of pre-clinical models for research focusing on neurodegeneration. They offer the possibility for better understanding of common and divergent pathogenic mechanisms of brain diseases. Moreover, iPSCs provide a unique opportunity to develop personalized therapeutic strategies, as well as explore early pathogenic mechanisms, since they rely on the use of patients' own cells that are otherwise accessible only post-mortem, when neuronal death-related cellular pathways and processes are advanced and adaptive. Neurodegenerative diseases are in majority of unknown cause, but mutations in specific genes can lead to familial forms of these diseases. For example, mutations in the superoxide dismutase 1 gene lead to the motor neuron disease amyotrophic lateral sclerosis (ALS), while mutations in the SNCA gene encoding for alpha-synuclein protein lead to familial Parkinson's disease (PD). The generations of libraries of familial human ALS iPSC lines have been described, and the iPSCs rapidly became useful models for studying cell autonomous and non-cell autonomous mechanisms of the disease. Here we report the generation of a comprehensive library of iPSC lines of familial PD and an associated synucleinopathy, multiple system atrophy (MSA). In addition, we provide examples of relevant neural cell types these iPSC can be differentiated into, and which could be used to further explore early disease mechanisms. These human cellular models will be a valuable resource for identifying common and divergent mechanisms leading to neurodegeneration in PD and MSA

The green box: An electronically versatile perylene diimide macrocyclic host for fullerenes

The powerful electron accepting ability of fullerenes makes them ubiquitous components in biomimetic donor–acceptor systems that model the intermolecular electron transfer processes of Nature’s photosynthetic center. Exploiting perylene diimides (PDIs) as components in cyclic host systems for the noncovalent recognition of fullerenes is unprecedented, in part because archetypal PDIs are also electron deficient, making dyad assembly formation electronically unfavorable. To address this, we report the strategic design and synthesis of a novel large, macrocyclic receptor composed of two covalently strapped electron-rich bis-pyrrolidine PDI panels, nicknamed the “Green Box” due to its color. Through the principle of electronic complementarity, the Green Box exhibits strong recognition of pristine fullerenes (C60/70), with the noncovalent ground and excited state interactions that occur upon fullerene guest encapsulation characterized by a range of techniques including electronic absorption, fluorescence emission, NMR and time-resolved EPR spectroscopies, cyclic voltammetry, mass spectrometry, and DFT calculations. While relatively low polarity solvents result in partial charge transfer in the host donor–guest acceptor complex, increasing the polarity of the solvent medium facilitates rare, thermally allowed full electron transfer from the Green Box to fullerene in the ground state. The ensuing charge separated radical ion paired complex is spectroscopically characterized, with thermodynamic reversibility and kinetic stability also demonstrated. Importantly, the Green Box represents a seminal type of C60/70 host where electron-rich PDI motifs are utilized as recognition motifs for fullerenes, facilitating novel intermolecular, solvent tunable ground state electronic communication with these guests. The ability to switch between extremes of the charge transfer energy continuum is without precedent in synthetic fullerene-based dyads

Межлабораторные сравнительные испытания в минералогических работах

 Introduction. Activities of FSBI “VIMS” are aimed at ensuring accuracy and comparability of the results of mineralogical analyses accompanying exploration and technological work. Evaluation of the research result quality is carried out with the help of various metrological instruments, one of which is an interlaboratory comparison test.Purpose. The purpose of interlaboratory comparison tests (ICTs) is to assess the results of X-ray quantitative phase analysis of an artificial mixture of minerals and to confirm the level of competence of testing laboratories.Methods. The procedure for conducting interlaboratory comparison tests is as follows: development of the programme and its approval; collecting and registering applications from laboratories, willing to participate in the ICT programme; preparation and simultaneous sending of control samples with accompanying information materials to those participating in the experiment; statistical processing of obtained results; drawing up, approval and circulation of documents confirming participation of the laboratories. The control sample is a homogenized artificial mixture of minerals (quartz, kaolinite, calcite and pyrite). The accuracy (quality) control of test results was carried out by X-ray quantitative phase analysis.Results. The ICT results showed a high level of competence of testing laboratories. For unreliable and unsatisfactory results percentages total less than 11%, the percentage for unfulfilled results is equal to zero. Interlaboratory comparison tests in mineralogical works are an important means for controlling competence of testing laboratories.Введение: Деятельность ФГБУ «ВИМС» направлена на обеспечение точности и сопоставимости результатов минералого-аналитических исследований, сопровождающих геологоразведочные и технологические работы. Оценка качества результатов исследований осуществляется метрологическими инструментами, одним из которых являются межлабораторные сравнительные испытания. Цель работы: Цель межлабораторных сравнительных испытаний (МСИ) – оценка результатов рентгенографического количественного фазового анализа искусственной смеси минералов и подтверждение технической компетентности испытательных лабораторий.Методы исследования: Порядок проведения межлабораторных сравнительных испытаний: разработка программы и ее утверждение; сбор и регистрация заявок от лабораторий, желающих принять участие в Программе МСИ; подготовка и единовременная рассылка образцов для контроля с сопутствующими информационными материалами участникам эксперимента; статистическая обработка полученных результатов; оформление, утверждение и рассылка документов, подтверждающих участие лабораторий. Образец для контроля представлен гомогенизированной искусственной смесью минералов (кварц, каолинит, кальцит и пирит). Контроль точности (качества) результатов испытаний осуществлялся рентгенографическим количественным фазовым анализом.Результаты: Результаты МСИ показали высокий уровень компетентности испытательных лабораторий. Суммарный процент сомнительных и неудовлетворительных результатов составил менее 11%, процент невыполненных равен нулю. Межлабораторные сравнительные испытания в минералогических работах являются важным инструментом для контроля компетентности испытательных лабораторий

Chemical reactions at the graphitic step-edge: changes in product distribution of catalytic reactions as a tool to explore the environment within carbon nanoreactors

A series of explorative cross-coupling reactions have been developed to investigate the local nanoscale environment around catalytically active Pd(II)complexes encapsulated within hollow graphitised nanofiber (GNF). Two new fullerene-containing and fullerene-free Pd(II)Salen catalysts have been synthesised, and their activity and selectivity towards different substrates has been explored in nanoreactors. The catalysts not only show a significant increase in activity and stability upon heterogenisation at the graphitic step-edges inside the GNF channel, but also exhibit a change in selectivity affected by the confinement which alters the distribution of isomeric products of the reaction. Furthermore, the observed selectivity changes reveal unprecedented details regarding the location and orientation of the catalyst molecules inside the GNF nanoreactor, inaccessible by any spectroscopic or microscopic techniques, thus shedding light on the precise reaction environment inside the molecular catalyst-GNF nanoreactor. Keywords: nanoreactor, catalysis, fullerene, salen, cross-couplin