The two redox states of the human NEET proteins’ [2Fe–2S] clusters

The NEET proteins constitute a unique class of [2Fe–2S] proteins. The metal ions bind to three cysteines and one histidine. The proteins’ clusters exist in two redox states; the oxidized protein (containing two FeIII ions) can transfer the cluster to apo-acceptor protein(s), while the reduced form (containing one ferrous ion) remains bound to the protein frame. Here, we perform in silico and in vitro studies on human NEET proteins in both reduced and oxidized forms. Quantum chemical calculations on all available human NEET proteins structures suggest that reducing the cluster weakens the Fe–NHis and Fe–SCys bonds, similar to what is seen in other Fe–S proteins (e.g., ferredoxin and Rieske protein). We further show that the extra electron in the [2Fe–2S]+ clusters of one of the NEET proteins (mNT) is localized on the His-bound iron ion, consistently with our previous spectroscopic studies. Kinetic measurements demonstrate that the mNT [2Fe–2S]+ is released only by an increase in temperature. Thus, the reduced state of human NEET proteins [2Fe–2S] cluster is kinetically inert. This previously unrecognized kinetic inertness of the reduced state, along with the reactivity of the oxidized state, is unique across all [2Fe–2S] proteins. Finally, using a coevolutionary analysis, along with molecular dynamics simulations, we provide insight on the observed allostery between the loop L2 and the cluster region. Specifically, we show that W75, R76, K78, K79, F82 and G85 in the latter region share similar allosteric characteristics in both redox states. Graphic abstract

Interaction of HCO+ Cations With Interstellar Negative Grains. Quantum Chemical Investigation and Astrophysical Implications

In cold galactic molecular clouds, dust grains are coated by icy mantles and are prevalently charged negatively, because of the capture of the electrons in the gas. The interaction of the charged grains with gaseous cations is known to neutralize them. In this work, we focus on the chemical consequences of the neutralization process of HCO+, often the most abundant cation in molecular clouds. More specifically, by means of electronic structure calculations, we have characterized the energy and the structure of all possible product species once the HCO+ ion adsorbs on water clusters holding an extra electron. Two processes are possible: (i) electron transfer from the negative water cluster to the HCO+ ion or (ii) a proton transfer from HCO+ to the negative water cluster. Energetic considerations favor electron transfer. Assuming this scenario, two limiting cases have been considered in astrochemical models: (a) all the neutralized HCO+ is retained as neutral HCO adsorbed on the ice and (b) all the neutralized HCO+ gets desorbed to the gas phase as HCO. None of the two limiting cases appreciably contribute to the HCO abundance on the grain surfaces or in the gas.

By an eccentric whim of fate or on the centralized schedule from above?

In recent years, with the light hand of three nimble yankees: S.Perlmutter, A.Riess and B.Schmidt - almost the whole world community suddenly sparked with very outlandish for many (and erstwhile unknown) problem of dark energy and dark matter. Whereas for natural philosophers there is nothing mysterious about it. Especially when you consider that multilayer ignored by modern science is inherent not only in habitual biological bodies, but also in crystals (possessing at least two additional sheaths) as well as, possibly, even in some evolutionarily advanced planets. Though, undoubtedly, the bulk of dark matter falls on Universe noosphere. As for dark energy, it is, rather, a kind of epistemological paradox that depends entirely on the position of observing subject. After all, on the periphery of a topologically closed Universe, any sober observer, by and large, won’t just find a single dark erg or even an extra electron-volt. However, besides these two clearly contrived pseudo-riddles, in his article the author also undertakes to solve the genuine disturbing minds cosmic mystery associated with so-called “grande silentium universi”. Well and to what extent he succeeded really in that - it's up for you already to decide, dear colleagues!

Double anchor indolo[3,2-b]indole derived metal-free dyes with extra electron donors as efficient sensitizers for dye-sensitized solar cells

Two new di-acceptors metal-free organic dyes based on indolo[3,2-b]indole donor backbone with extra electron donors were designed, synthesized, and applied for dye-sensitized solar cells (DSSCs). In this study, the effect...

Matily Herbal Drink May Reduce Oxidative Stress, Hyperglycemia, and Hyperlipidemia and Increases Immunity - Case Study Reports

Oxygen is an element indispensable for all aerobic organisms to sustain life (1). Cells produce energy mainly in the mitochondria through oxidative phosphorylation, a series of electron transfer in the Electron Transport Chain (ETC), where oxygen is the final electron acceptor. During this process, it creates free radicles by the mitochondria. Oxidative stress produces free radicals. A 70 Kgs man may produce nearly 2 Kg of free radicals in his body in a year (2). It is comparatively a huge amount. Examples offree radicals with one or more unpaired electrons are superoxide, hydroxyl, andnitric oxide radicals (1, 3). A molecule like oxygen is stable when it shares its electrons in the paired state, when it loses or gains an extra electron, it becomes unstable. This condition leads them to “steal” or take it from other biomolecules. This process leaves the biomolecules in the oxidative state, which can start pathological conditions. For example, when Low-Density Lipoproteins when becomingoxidized, causes atherosclerosis in the blood vessels and cause plaques inside the arteries (4).

Diverting Radical-Anionic C-H Amidation to a C-N/C-O Cascade for the Construction of Hydroxyisoindolines from Unprotected Amides

<p>An intramolecular C(sp³)-H amidation proceeds in the presence of <i>t</i>-BuOK, molecular oxygen, and DMF. The success of this reaction hinges on the deprotonation of a mildly acidic N-H bond and selective radical activation of a benzylic C(sp³)-H bond towards hydrogen atom transfer (HAT)<i>. </i>DFT calculations suggest a thermodynamically favorable sequence of steps mediated by the generation of a radical-anion intermediate. As this intermediate starts to form a two-centered/three-electron (<i>2c,3e)</i>C-N bond, the extra electron is “ejected” into the π*-orbital of the aromatic core. The resulting cyclic radical-anion is readily oxidized by molecular oxygen to forge the C-N bond of the product. The transformation of a relatively weak reductant into a stronger reductant (i.e., “reductant upconversion”) allows one to use mild oxidants such as molecular oxygen. In contrast, the second stage of NH/CH activation forms a highly stabilized radical-anion intermediate incapable of electron transfer to molecular oxygen. Hence, the oxidation is impossible and an alternative reaction path opens via coupling between the radical anion intermediate and either superoxide or hydroperoxide radical. The hydroperoxide intermediate transforms into the final hydroxyisoindoline products under basic conditions. The use of TEMPO as an additive was found to activate less reactive amides. The combination of experimental and computational data outlines a conceptually new mechanism for the conversion of unprotected amides into hydroxyisoindolines proceeding as a sequence of C-H amidation and C-H oxidation.</p>

Diverting Radical-Anionic C-H Amidation to a C-N/C-O Cascade for the Construction of Hydroxyisoindolines from Unprotected Amides

<p>An intramolecular C(sp³)-H amidation proceeds in the presence of <i>t</i>-BuOK, molecular oxygen, and DMF. The success of this reaction hinges on the deprotonation of a mildly acidic N-H bond and selective radical activation of a benzylic C(sp³)-H bond towards hydrogen atom transfer (HAT)<i>. </i>DFT calculations suggest a thermodynamically favorable sequence of steps mediated by the generation of a radical-anion intermediate. As this intermediate starts to form a two-centered/three-electron (<i>2c,3e)</i>C-N bond, the extra electron is “ejected” into the π*-orbital of the aromatic core. The resulting cyclic radical-anion is readily oxidized by molecular oxygen to forge the C-N bond of the product. The transformation of a relatively weak reductant into a stronger reductant (i.e., “reductant upconversion”) allows one to use mild oxidants such as molecular oxygen. In contrast, the second stage of NH/CH activation forms a highly stabilized radical-anion intermediate incapable of electron transfer to molecular oxygen. Hence, the oxidation is impossible and an alternative reaction path opens via coupling between the radical anion intermediate and either superoxide or hydroperoxide radical. The hydroperoxide intermediate transforms into the final hydroxyisoindoline products under basic conditions. The use of TEMPO as an additive was found to activate less reactive amides. The combination of experimental and computational data outlines a conceptually new mechanism for the conversion of unprotected amides into hydroxyisoindolines proceeding as a sequence of C-H amidation and C-H oxidation.</p>

Modification of excitation and charge transfer in cavity quantum-electrodynamical chemistry

Energy transfer in terms of excitation or charge is one of the most basic processes in nature, and understanding and controlling them is one of the major challenges of modern quantum chemistry. In this work, we highlight that these processes as well as other chemical properties can be drastically altered by modifying the vacuum fluctuations of the electromagnetic field in a cavity. By using a real-space formulation from first principles that keeps all of the electronic degrees of freedom in the model explicit and simulates changes in the environment by an effective photon mode, we can easily connect to well-known quantum-chemical results such as Dexter charge-transfer and Förster excitation-transfer reactions, taking into account the often-disregarded Coulomb and self-polarization interaction. We find that the photonic degrees of freedom introduce extra electron–electron correlations over large distances and that the coupling to the cavity can drastically alter the characteristic charge-transfer behavior and even selectively improve the efficiency. For excitation transfer, we find that the cavity renders the transfer more efficient, essentially distance-independent, and further different configurations of highest efficiency depending on the coherence times. For strong decoherence (short coherence times), the cavity frequency should be in between the isolated excitations of the donor and acceptor, while for weak decoherence (long coherence times), the cavity should enhance a mode that is close to resonance with either donor or acceptor. Our results highlight that changing the photonic environment can redefine chemical processes, rendering polaritonic chemistry a promising approach toward the control of chemical reactions.

An interpretation of the cosmic ray e+ + e− spectrum from 10GeV to 3TeV measured by CALET on the ISS

A combined interpretation of the Calorimetric Electron Telescope (CALET) [Formula: see text] spectrum up to 3[Formula: see text]TeV and the AMS-02 positron spectrum up to 500[Formula: see text]GeV was performed and the results are discussed. To parametrize the background electron flux, we assume a smoothly broken power-law spectrum with an exponential cutoff for electrons and fit this parametrization to the measurements, with either a pulsar or 3-body decay of fermionic Dark Matter (DM) as the extra electron–positron pair source responsible for the positron excess. We found that depending on the parameters for the background, both DM decay and the pulsar model can explain the combined measurements. While the DM decay scenario is constrained by the Fermi-LAT [Formula: see text]-ray measurement, we show that 3-body decay of a 800[Formula: see text]GeV DM can be compatible with the [Formula: see text]-ray flux measurement. We discuss the capability of CALET to discern decaying DM models from a generic pulsar source scenario, based on simulated data for five years of data-taking.

Mechanism of fatty acid decarboxylation catalyzed by a non-heme iron oxidase (UndA): a QM/MM study

QM/MM calculations reveal that the fatty acid decarboxylase UndA employs the FeIII–OO˙− complex to initiate the β-H abstraction with the monodentate coordination mode. The iron center accepts the extra electron of the substrate radical.