Structural Characterization of the Metalized Radical Cations of Adenosine ([Ade+Li-H]•+ and [Ade+Na-H]•+) by Infrared Multiphoton Dissociation Spectroscopy and Theoretical Studies.

Nucleoside radicals are key intermediates in the process of DNA damage, and alkali metal ions are a common group of ions in living organisms. However, so far, there has been a significant lack of research on the structural effects of alkali metal ions on nucleoside free radicals. In this study, we report a new method for generating metalized nucleoside radical cations in the gas phase. The radical cations [Ade+M-H]•+ (M = Li, Na) are generated by the 280 nm ultraviolet photodissociation (UVPD) of the precursor ions of lithiated and sodiated ions of 2-iodoadenine in a Fourier transform ion cyclotron resonance (FT ICR) cell. Further infrared multiphoton dissociation (IRMPD) spectra of both radical cations were recorded in the region of 2750-3750 cm-1. By combining these results with theoretical calculations, the most stable isomers of both radicals can be identified, which share the common characteristics of triple coordination patterns of the metal ions. For both radical species, the lowest-energy isomers undergo hydrogen transfer. Although the sugar ring in the most stable isomer of [Ade+Li-H]•+ is in a (South, syn) conformation similar to that of [Ado+Na]+, [Ade+Na-H]•+ is distinguished by the unexpected opening of the sugar ring. Their theoretical spectra are in good agreement with experimental spectra. However, due to the flexibility of the structures and the complexity of their potential energy surfaces, the hydrogen transfer pathways still need to be further studied. Considering that the free radicals formed directly after C-I cleavage have some similar spectral characteristics, the existence of these corresponding isomers cannot be ruled out. The findings imply that the structures of nucleoside radicals may be significantly influenced by the attached alkali metal ions. More detailed experiments and theoretical calculations are still crucial.

Enzyme polymorphism, oxygen and injury: a lipidomic analysis of flight-induced oxidative damage in a succinate dehydrogenase d (Sdhd)-polymorphic insect.

When active tissues receive insufficient oxygen to meet metabolic demand, succinate accumulates and has two fundamental effects: it causes ischemia-reperfusion injury while also activating the hypoxia-inducible factor pathway (HIF). The Glanville fritillary butterfly (Melitaea cinxia) possesses a balanced polymorphism in Sdhd, shown previously to affect HIF pathway activation and tracheal morphology and used here to experimentally test the hypothesis that variation in succinate dehydrogenase affects oxidative injury. We stimulated butterflies to fly continuously in a respirometer (3 min duration), which typically caused episodes of exhaustion and recovery, suggesting a potential for cellular injury from hypoxia and reoxygenation in flight muscles. Indeed, flight muscle from butterflies flown on consecutive days had lipidome profiles similar to those of rested paraquat-injected butterflies, but distinct from those of rested untreated butterflies. Many butterflies showed a decline in flight metabolic rate (FMR) on day 2, and there was a strong inverse relationship between the ratio of day 2 to day 1 FMR and the abundance of sodiated adducts of phosphatidylcholines and co-enzyme Q (CoQ). This result is consistent with elevation of sodiated lipids caused by disrupted intracellular ion homeostasis in mammalian tissues after hypoxia-reperfusion. Butterflies carrying the Sdhd M allele had a higher abundance of lipid markers of cellular damage, but the association was reversed in field-collected butterflies, where focal individuals typically flew for seconds at a time rather than continuously. These results indicate that Glanville fritillary flight muscles can be injured by episodes of high exertion, but injury severity appears to be determined by an interaction between SDH genotype and behavior (prolonged versus intermittent flight).

Consecutive loss of two benzyl radicals from the [M + Na]+ adduct ions of pyrogallol tribenzyl ether and its derivatives.

The electrospray ionization-collision-induced dissociation mass spectra of nine pyrogallol tribenzyl ethers, 2-10, and a catechol dibenzyl ether, 11, that bear various functional groups or larger structural extensions have been studied with respect to the occurrence of a highly characteristic consecutive loss of two benzyl radicals from the sodiated molecular ions, [M + Na]+. It is shown that this specific fragmentation reaction strongly dominates other fragmentation routes, such as loss of carbon monoxide, formaldehyde and water. In addition, elimination of benzaldehyde occurs as a minor fragmentation channel in most cases. In contrast to these aryl-benzyl ethers, the consecutive two-fold loss of C7H7• is suppressed in the [M + Na]+ ions of dibenzyl ethers derived from multiply benzylated gallocatechin and catechin, where the elimination of benzyl alcohol prevails the primary fragmentation almost completely. The secondary fragmentation of the [M + Na]+ ions, which also comprises the two-fold loss of C7H7•, as well as a remarkable primary fragmentation of a flavene-based congener leading to particularly stable sodium-free chromylium product ions is also presented. † Deceased.

Unexpected hydrated ions in the detection of sodium adduct coumarins using electrospray tandem mass spectrometry.

A series of coumarins were analyzed using electrospray ionization quadrupole time-of-flight tandem mass spectrometry in the positive-ion mode. Unexpected hydrated ions ([M + H2O + Na]+) was observed upon collision-induced dissociation of the sodiated ions ([M + Na]+) of eight coumarins. Several factors which affected relative abundance of [M + H2O + Na]+ ions such as collision energy, concentration and solvent were investigated. None of them have effect on the relative abundance of [M + H2O + Na]+. However, the peak of hydrated ions was not detected in the further collision-induced dissociation of protonated ions of coumarins. Apigenin and Quercetin sharing similar benzopyrone structural unit with coumarins are selected for tandem mass spectrometry analysis. There were no hydrated ions in their tandem mass spectrometry spectra of the precursor [M + Na]+ ions. Thus, both coumarins and sodium were necessary for the formation of [M + H2O + Na]+. Together with the result that hydrated ions are not formed by hydrolysis reactions, a six-membered ring structure which involves with the formation of [M + H2O + Na]+ was presented. And D-labeling experiment indicates that the H2O molecule did not come from solvent.

Tunable Electrocatalytic Behavior of Sodiated MoS2 Active Sites toward Efficient Sulfur Redox Reactions in Room-Temperature Na-S Batteries.

Room-temperature (RT) sodium-sulfur (Na-S) batteries hold great promise for large-scale energy storage due to the advantages of high energy density, low cost, and resource abundance. The research progress on RT Na-S batteries, however, has been greatly hindered by the sluggish kinetics of the sulfur redox reactions. Herein, an elaborate multifunctional architecture, consisting of N-doped carbon skeletons and tunable MoS2 sulfiphilic sites, is fabricated via a simple one-pot reaction followed by in situ sulfurization. Beyond the physical confinement and chemical binding of polarized N-doped carbonaceous microflowers, the MoS2 active sites play a key role in catalyzing polysulfide redox reactions, especially the conversion from long-chain Na2 Sn (4 ≤ n ≤ 8) to short-chain Na2 S2 and Na2 S. Significantly, the electrocatalytic activity of MoS2 can be tunable via adjusting the discharge depth. It is remarkable that the sodiated MoS2 exhibits much stronger binding energy and electrocatalytic behavior compared to MoS2 sites, effectively enhancing the formation of the final Na2 S product. Consequently, the S cathode achieves superior electrochemical performance in RT Na-S batteries, delivering a high capacity of 774.2 mAh g-1 after 800 cycles at 0.2 A g-1 , and an ultrahigh capacity retention with a capacity decay rate of only 0.0055% per cycle over 2800 cycles.