The Helicobacter pylori methylome is acid-responsive due to regulation by the two-component system ArsRS and the type I DNA methyltransferase HsdM1 (HP0463).

In addition to its role in genome protection, DNA methylation can regulate gene expression. In this study, we characterized the impact of acidity, phase variation, and the ArsRS TCS on the expression of the Type I m6A DNA methyltransferase HsdM1 (HP0463) of Helicobacter pylori 26695 and their subsequent effects on the methylome. Transcription of hsdM1 increases at least fourfold in the absence of the sensory histidine kinase ArsS, the major acid-sensing protein of H. pylori. hsdM1 exists in the phase-variable operon hsdR1-hsdM1. Phase-locking hsdR1 (HP0464), the restriction endonuclease gene, has significant impacts on the transcription of hsdM1. To determine the impacts of methyltransferase transcription patterns on the methylome, we conducted methylome sequencing on samples cultured at pH 7 or pH 5. We found differentially methylated motifs between these growth conditions and that deletions of arsS and/or hsdM1 interfere with the epigenetic acid response. Deletion of arsS leads to altered activity of HsdM1 and multiple other methyltransferases under both pH conditions indicating that the ArsRS TCS, in addition to direct effects on regulon transcription during acid acclimation, may also indirectly impact gene expression via regulation of the methylome. We determined the target motif of HsdM1 (HP0463) to be the complementary bipartite sequence pair 5'-TCAm6AVN6TGY-3' and 3'-AGTN6GAm6ACA-5'. This complex regulation of DNA methyltransferases, and thus differential methylation patterns, may have implications for the decades-long persistent infection by H. pylori. IMPORTANCE This study expands the possibilities for complex, epigenomic regulation in Helicobacter pylori. We demonstrate that the H. pylori methylome is plastic and acid sensitive via the two-component system ArsRS and the DNA methyltransferase HsdM1. The control of a methyltransferase by ArsRS may allow for a layered response to changing acidity. Likely, an early response whereby ArsR~P affects regulon expression, including the methyltransferase hsdM1. Then, a somewhat later effect as the altered methylome, due to altered HsdM1 expression, subsequently alters the expression of other genes involved in acclimation. The intermediate methylation of certain motifs supports the hypothesis that methyltransferases play a regulatory role. Untangling this additional web of regulation could play a key role in understanding H. pylori colonization and persistence.

Surveying the scope of aromatic decarboxylations catalyzed by prenylated-flavin dependent enzymes.

The prenylated-flavin mononucleotide-dependent decarboxylases (also known as UbiD-like enzymes) are the most recently discovered family of decarboxylases. The modified flavin facilitates the decarboxylation of unsaturated carboxylic acids through a novel mechanism involving 1,3-dipolar cyclo-addition chemistry. UbiD-like enzymes have attracted considerable interest for biocatalysis applications due to their ability to catalyse (de)carboxylation reactions on a broad range of aromatic substrates at otherwise unreactive carbon centres. There are now ∼35 000 protein sequences annotated as hypothetical UbiD-like enzymes. Sequence similarity network analyses of the UbiD protein family suggests that there are likely dozens of distinct decarboxylase enzymes represented within this family. Furthermore, many of the enzymes so far characterized can decarboxylate a broad range of substrates. Here we describe a strategy to identify potential substrates of UbiD-like enzymes based on detecting enzyme-catalysed solvent deuterium exchange into potential substrates. Using ferulic acid decarboxylase (FDC) as a model system, we tested a diverse range of aromatic and heterocyclic molecules for their ability to undergo enzyme-catalysed H/D exchange in deuterated buffer. We found that FDC catalyses H/D exchange, albeit at generally very low levels, into a wide range of small, aromatic molecules that have little resemblance to its physiological substrate. In contrast, the sub-set of aromatic carboxylic acids that are substrates for FDC-catalysed decarboxylation is much smaller. We discuss the implications of these findings for screening uncharacterized UbiD-like enzymes for novel (de)carboxylase activity.

Bonding Interactions in Uranyl α-Diimine Complexes: A Spectroscopic and Electrochemical Study of the Impacts of Ligand Electronics and Extended Conjugation.

Uranyl complexes of aryl-substituted α-diimine ligands gbha (UO2-1a-f) and phen-BIAN (UO2-2a-f) [gbha (1) = glyoxal bis(2-hydroxyanil); phen-BIAN (2) = N,N'-bis(iminophenol)acenaphthene; R = OMe (a), t-bu (b), H (c), Me (d), F (e), and naphthyl (f)] were designed, prepared, and characterized by X-ray diffraction, FT-IR, NMR, UV-vis, and electrochemical methods. These ligand frameworks contain a salen-type O-N-N-O binding pocket but are redox-noninnocent, leading to unusual metal complex behaviors. Here, we describe three solid-state structures of uranyl complexes UO2-1b, UO2-1c, and UO2-1f and observe manifestations of ligand noninnocence for the U(VI) complexes UO2-1b and UO2-1c. The impacts of accessible π-systems and ligand substitution on the axial uranium-oxo interactions were evaluated spectroscopically via the intraligand charge-transfer (ILCT) processes that dominate the absorption spectra of these complexes and through changes to the asymmetric (ν3) O═U═O stretching frequency. This, in combination with electrochemical data, reveals the effects of the inclusion of the conjugated acenaphthene backbone and the importance of ligand electronic structure on uranyl's bonding interactions.

Specific adsorption of perchlorate anions on Pt{hkl} single crystal electrodes.

The voltammetry of Pt{111}, Pt{100}, Pt{110} and Pt{311} single crystal electrodes as a function of perchloric acid concentration (0.05-2.00 M) has been studied in order to test the assertion made in recent reports by Watanabe et al. that perchlorate anions specifically adsorb on polycrystalline platinum. Such an assertion would have significant ramifications for our understanding of electrocatalytic processes at platinum surfaces since perchlorate anions at low pH have classically been assumed not to specifically adsorb. For Pt{111}, it is found that OHad and electrochemical oxide states are both perturbed significantly as perchloric acid concentration is increased. We suggest that this is due to specific adsorption of perchlorate anions competing with OHad for adsorption sites. The hydrogen underpotential deposition (H UPD) region of Pt{111} however remains unchanged although evidence for perchlorate anion decomposition to chloride on Pt{111} is reported. In contrast, for Pt{100} no variation in the onset of electrochemical oxide formation is found nor any shift in the potential of the OHad state which normally results from the action of specifically adsorbing anions. This suggests that perchlorate anions are non-specifically adsorbed on this plane although strong changes in all H UPD states are observed as perchloric acid concentration is increased. This manifests itself as a redistribution of charge from the H UPD state situated at more positive potential to the one at more negative potential. For Pt{110} and Pt{311}, marginal changes in the onset of electrochemical oxide formation are recorded, associated with specific adsorption of perchlorate. Specific adsorption of perchlorate anions on Pt{111} is deleterious to electrocatalytic activity in relation to the oxygen reduction reaction (ORR) as measured using a rotating disc electrode (RDE) in a hanging meniscus configuration. This study supports previous work suggesting that a large component of the ORR activity on platinum is governed by simple site blocking by specifically adsorbed anions and/or electrosorbed oxide.

Electron paramagnetic resonance as a tool to determine the sodium charge storage mechanism of hard carbon.

Hard carbon is a promising negative electrode material for rechargeable sodium-ion batteries due to the ready availability of their precursors and high reversible charge storage. The reaction mechanisms that drive the sodiation properties in hard carbons and subsequent electrochemical performance are strictly linked to the characteristic slope and plateau regions observed in the voltage profile of these materials. This work shows that electron paramagnetic resonance (EPR) spectroscopy is a powerful and fast diagnostic tool to predict the extent of the charge stored in the slope and plateau regions during galvanostatic tests in hard carbon materials. EPR lineshape simulation and temperature-dependent measurements help to separate the nature of the spins in mechanochemically modified hard carbon materials synthesised at different temperatures. This proves relationships between structure modification and electrochemical signatures in the galvanostatic curves to obtain information on their sodium storage mechanism. Furthermore, through ex situ EPR studies we study the evolution of these EPR signals at different states of charge to further elucidate the storage mechanisms in these carbons. Finally, we discuss the interrelationship between EPR spectroscopy data of the hard carbon samples studied and their corresponding charging storage mechanism.

Cardiac complications of cancer therapies.

The quest of defeating cancer and improving prognosis in survivors has generated remarkable strides forward in research and have advanced the development of new antineoplastic therapies. These achievements, combined with rapid screening and early detection, have considerably extended the life expectancy of patients surviving multiple types of malignancies. Consequently, chemotherapy-related toxicity in several organ systems, especially the cardiovascular system, has surfaced as one of the leading causes of morbidity and mortality among cancer survivors. Recent evidence classifies chemotherapy-induced cardiotoxicity as the second-leading cause of morbidity and mortality, closely comparing with secondary cancer malignancies. While a certain degree of cardiotoxicity has been reported to accompany most chemotherapies, including anthracyclines, anti-metabolites, and alkylating agents, even the latest targeted cancer therapies such as immune checkpoint inhibitors and tyrosine kinase inhibitors have been associated with acute and chronic cardiac sequelae. In this chapter, we focus on describing the principal mechanism(s) for each class of chemotherapeutic agents that lead to cardiotoxicity and the innovative translational research approaches that are currently being explored to prevent or treat cancer therapy-induced cardiotoxicity and related cardiac complications.

Reduction in acute gastroenteritis hospitalizations among US children after introduction of rotavirus vaccine: analysis of hospital discharge data from 18 US states.

BACKGROUND: In 2006, RotaTeq (RV5) was recommended for routine vaccination of United States (US) infants. We compared hospitalization rates for acute gastroenteritis among US children aged <5 years during pre-RV5 rotavirus seasons from 2000 through 2006 with those during the post-RV5 2007 and 2008 seasons. METHODS: Using 100% hospital discharge data from 18 states, accounting for 49% of the US population, we calculated acute gastroenteritis hospitalization rates for children aged <5 years by rotavirus season, 8 age groups (0-2, 3-5, 6-11, 12-17, 18-23, 24-35, 36-47, and 48-59 months), and state. RESULTS: Compared with the median rate for the 2000-2006 rotavirus seasons (101.1 hospitalizations per 10,000 children), the rates for 2007 and 2008 (85.5 and 55.5 hospitalizations per 10,000 children) were 16% and 45% lower, respectively. Children aged 0-2 months had a 28% reduction, those aged 6-23 months had a reduction of 50%, and children aged 3-5 months and 24-59 months had reductions ranging between 42% and 45% during the 2008 rotavirus season, compared with the median rate for 2000-2006 rotavirus seasons. CONCLUSIONS: The introduction of the RV5 vaccine was associated with a dramatic reduction in hospitalizations for acute gastroenteritis among US children during the 2008 rotavirus season.

Racial disparities in diarrhea-associated hospitalizations among children in five US States, before and after introduction of rotavirus vaccine.

Racial differences in diarrheal disease have not been systematically examined, and the impact of rotavirus vaccine on these differences has not been assessed. We compared diarrhea-associated hospitalizations by race/ethnicity among children <5 years pre- (2000-2006) and post- (2007 and 2008) rotavirus vaccine introduction in five US states. Pre-vaccine hospitalization rates were greater among whites versus blacks and Hispanics. However, black (versus non-black) infants <6 months and white (versus non-white) children ≥ 1 year had higher rates. In 2008, racial disparities for children 12-35 months resolved, but higher hospitalization rates among black infants <6 months persisted, highlighting the need for timely vaccination.