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An enzyme-mediated approach for the assembly of singly modified RNA constructs in which specific G residues are replaced with th G, an emissive isomorphic G surrogate, is reported. Transcription in the presence of th G and native nucleoside triphosphates enforces initiation with the unnatural analogue, yielding 5'-end modified transcripts that can be mono-phosphorylated and ligated to provide longer site-specifically modified RNA constructs. The scope of this unprecedented enzymatic approach to non-canonical purine-containing RNAs is explored via the assembly of several altered hammerhead (HH) ribozymes and a singly modified HH substrate. By strategically modifying key positions, a mechanistic insight into the ribozyme-mediated cleavage is gained. Additionally, the emissive features of the modified nucleoside and its responsiveness to environmental changes can be used to monitor cleavage in real time by steady state fluorescence spectroscopy.

To display favorable fluorescent properties, the non-emissive native nucleosides need to be modified. Here we present a motif that relies on conjugating 5-membered aromatic heterocycles (e.g., thiophene) to a 6-azapyrimidine (1,2,4-triazine) core. Synthetic accessibility and desirable photophysical properties make these nucleosides attractive candidates for enzymatic incorporation and biochemical assays. While 6-azauridine triphosphate is known to be poorly tolerated by polymerases in RNA synthesis, we illustrate that conjugating a thiophene ring at position 5 overcomes such limitations, facilitating its T7 RNA polymerase-mediated in vitro transcription incorporation into RNA constructs. We further show that the modified transcripts can be ligated to longer oligonucleotides to form singly modified RNAs, as illustrated for an A-site hairpin model RNA construct, which was employed to visualize aminoglycoside antibiotics binding.

BackgroundFew studies have examined how antiplatelet therapies are selected during the routine care of acute myocardial infarction patients, particularly relative to the patient's estimated mortality and bleeding risks.Methods and resultsWe examined patients presenting with acute myocardial infarction treated with percutaneous coronary intervention at 233 US hospitals in the TRANSLATE-ACS observational study from April 2010 to October 2012. We developed a multivariable logistic regression model to identify factors associated with prasugrel selection. Prasugrel use rates and associated 1-year risk-adjusted major adverse cardiovascular events and Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO) moderate/severe bleeding outcomes were also examined in relation to predicted mortality and bleeding using the validated Acute Coronary Treatment and Intervention Outcomes (ACTION) risk prediction scores. Among 11 969 patients, 3123 (26%) received prasugrel at the time of percutaneous coronary intervention. The strongest factors associated with prasugrel use included cardiogenic shock (odds ratio [OR] 1.68, 95% CI 1.25-2.26), drug-eluting stent use (OR 1.45, 95% CI 1.31-1.62), and ST-segment elevation myocardial infarction presentation (OR 1.23, 95% CI 1.12-1.35). Older age (OR 0.57, 95% CI 0.0.53-0.61), dialysis (OR 0.56, 95% CI 0.32-0.96), prior history of stroke/transient ischemic attack (OR 0.52, 95% CI 0.38-0.73), and interhospital transfer (OR 0.50, 95% CI 0.46-0.55) were associated with lowest prasugrel selection. Prasugrel was used less often than clopidogrel in patients at higher predicted bleeding risk (21.9% versus 29.7%, P

Polymyxin B is an antibiotic used against multi-resistant gram negative infections, despite observed nephrotoxicity. Here we report the synthesis of functionalized derivatives of polymyxin B and its per-guanidinylated derivative in order to further explore the structural requirements necessary to facilitate uptake of the antibiotic into mammalian cells. We also investigate the possibility of using these novel scaffolds as molecular transporters. At nanomolar concentrations, both are capable of delivering large cargo (>300 kDa) into living cells. Their uptake depends exclusively on cell surface heparan sulfate. Mechanistic studies indicate these novel transporters are internalized through caveolae-mediated pathways and confocal microscopy show colocalization with lysosomes. The polymyxin-based transporters demonstrate cytosolic delivery through the delivery of a ribosome-inactivating toxin. Furthermore, the natural polymyxin scaffold can be incorporated into liposomes and enhance their intracellular uptake. In addition to demonstrating the ability of the polymyxin scaffold to facilitate internalization into mammalian cells, these observations suggest the potential use of polymyxin and guanidinopolymyxin for intracellular delivery.

BackgroundAn individual's socioeconomic status (SES) is associated with health outcomes and mortality, yet it is unknown whether accounting for SES can improve risk-adjustment models for 30-day outcomes among Centers for Medicare & Medicaid Services beneficiaries hospitalized with heart failure.Methods and resultsWe linked clinical data on hospitalized patients with heart failure in the Get With The Guidelines-Heart Failure database (January 2005 to December 2011) with Centers for Medicare & Medicaid Services claims and county-level SES data from the 2012 Area Health Resources Files. We compared the discriminatory capabilities of multivariable models that adjusted for SES, patient, and hospital characteristics to determine whether county-level SES data improved prediction or changed hospital rankings for 30-day all-cause mortality and rehospitalization. After adjusting for patient and hospital characteristics, median household income (per $5000 increase) was inversely associated with odds of 30-day mortality (odds ratio, 0.97; 95% confidence interval, 0.95-1.00; P=0.032) and the percentage of people with at least a high school diploma (per 5 U increase) was associated with lower odds of 30-day rehospitalization (odds ratio, 0.95; 95% confidence interval, 0.91-0.99). After adjustment for county-level SES data, relative to whites, Hispanic ethnicity (odds ratio, 0.70; 95% confidence interval, 0.58-0.83) and black race (odds ratio, 0.57; 95% confidence interval, 0.50-0.65) remained significantly associated with lower 30-day mortality, but had similar 30-day rehospitalization. County-level SES did not improve risk adjustment or change hospital rankings for 30-day mortality or rehospitalization.ConclusionsCounty-level SES data are modestly associated with 30-day outcomes for Centers for Medicare & Medicaid Services beneficiaries hospitalized with heart failure, but do not improve risk adjustment models based on patient characteristics alone.

BackgroundReturning home after the hospital is a primary aim for healthcare; however, additional postacute care (PAC) services are sometimes necessary for returning stroke patients to their pre-event status. Recent trends in hospital discharge disposition specifying PAC use have not been examined across age groups or health insurance types.Methods and resultsWe examined trends in discharge to inpatient rehabilitation facilities (IRFs), skilled nursing facilities (SNFs), home with home health (HH), and home without services for 849 780 patients ≥18 years of age with ischemic or hemorrhagic stroke at 1687 hospitals participating in Get With The Guidelines-Stroke. Multivariable analysis was used to identify factors associated with discharge to any PAC (IRF, SNF, or HH) versus discharge home without services. From 2003 to 2011, there was a 2.1% increase (unadjusted P=0.001) in PAC use after a stroke hospitalization. Change was greatest in SNF use, an 8.3% decrease over the period. IRF and HH increased 6.9% and 3.6%, respectively. The 2 strongest clinical predictors of PAC use after acute care were patients not ambulating on the second day of their hospital stay (ambulation odds ratio [OR], 3.03; 95% confidence interval [CI], 2.86 to 3.23) and those who failed a dysphagia screen or had an order restricting oral intake (OR, 2.48; 95% CI, 2.37 to 2.59).ConclusionsFour in 10 stroke patients are discharged home without services. Although little has changed overall in PAC use since 2003, further research is needed to explain the shift in service use by type and its effect on outcomes.

Returning home after the hospital is a primary aim for healthcare; however, additional postacute care (PAC) services are sometimes necessary for returning stroke patients to their pre-event status. Recent trends in hospital discharge disposition specifying PAC use have not been examined across age groups or health insurance types. We examined trends in discharge to inpatient rehabilitation facilities (IRFs), skilled nursing facilities (SNFs), home with home health (HH), and home without services for 849 780 patients ≥18 years of age with ischemic or hemorrhagic stroke at 1687 hospitals participating in Get With The Guidelines-Stroke. Multivariable analysis was used to identify factors associated with discharge to any PAC (IRF, SNF, or HH) versus discharge home without services. From 2003 to 2011, there was a 2.1% increase (unadjusted P=0.001) in PAC use after a stroke hospitalization. Change was greatest in SNF use, an 8.3% decrease over the period. IRF and HH increased 6.9% and 3.6%, respectively. The 2 strongest clinical predictors of PAC use after acute care were patients not ambulating on the second day of their hospital stay (ambulation odds ratio [OR], 3.03; 95% confidence interval [CI], 2.86 to 3.23) and those who failed a dysphagia screen or had an order restricting oral intake (OR, 2.48; 95% CI, 2.37 to 2.59). Four in 10 stroke patients are discharged home without services. Although little has changed overall in PAC use since 2003, further research is needed to explain the shift in service use by type and its effect on outcomes.

The fastidious behavior of T7 RNA polymerase limits the incorporation of synthetic nucleosides into RNA transcripts, particularly at or near the promoter. The practically exclusive use of GTP for transcription initiation further compounds this challenge, and reactions with GTP analogs, where the heterocyclic nucleus has been altered, have not, to our knowledge, been demonstrated. The enzymatic incorporation of (th)GTP, a newly synthesized isomorphic fluorescent nucleotide with a thieno[3,4-d]pyrimidine core, is explored. The modified nucleotide can initiate and maintain transcription reactions, leading to the formation of fully modified and highly emissive RNA transcripts with (th)G replacing all guanosine residues. Short and long modified transcripts are synthesized in comparable yields to their natural counterparts. To assess proper folding and function, transcripts were used to assemble a hammerhead ribozyme with all permutations of natural and modified enzyme and substrate strands. The (th)G modified substrate was effectively cleaved by the natural RNA enzyme, demonstrating the isomorphic features of the nucleoside and its ability to replace G residues while retaining proper folding. In contrast, the (th)G modified enzyme showed little cleavage ability, suggesting the modifications likely disrupted the catalytic center, illustrating the significance of the Hoogsteen face in mediating appropriate contacts. Importantly, the ribozyme cleavage reaction of the emissive fluorescent transcripts could be followed in real time by fluorescence spectroscopy. Beyond their utility as fluorescent probes in biophysical and discovery assays, the results reported point to the potential utility of such isomorphic nucleosides in probing specific mechanistic questions in RNA catalysis and RNA structural analysis.

Semisynthetic derivatives of the clinically useful aminoglycosides tobramycin and amikacin were prepared by selectively modifying their 6'' positions with a variety of hydrogen bond donors and acceptors. Their binding to the rRNA A-site was probed using an in vitro FRET-based assay, and their antibacterial activities against several resistant strains (e.g., Pseudomonas aeruginosa, Klebsiella pneumonia, MRSA) were quantified by determining minimum inhibitory concentrations (MICs). The most potent derivatives were evaluated for their eukaryotic cytotoxicity. Most analogues displayed higher affinity for the bacterial A-site than the parent compounds. Although most tobramycin analogues exhibited no improvement in antibacterial activity, several amikacin analogues showed potent and broad-spectrum antibacterial activity against resistant bacteria. Derivatives tested for eukaryotic cytotoxicity exhibited minimal toxicity, similar to the parent compounds.

Adenosine deaminase, a major enzyme involved in purine metabolism, converts an isomorphic fluorescent analogue of adenosine (thA) to an isomorphic inosine analogue (thI), which possesses distinct spectral features, allowing one to monitor the enzyme-catalyzed reaction and its inhibition in real time. The utility of this sensitive fluorescently-monitored transformation for the high throughput detection and analysis of ADA inhibitors is demonstrated.

Looking for targets: while the bactericidal activity of polymyxins is attributed to changes in membrane permeation, we show that these antibiotics can bind prokaryotic and eukaryotic A-sites, domains responsible for translational decoding. Polymyxin B, colistin and analogues also hinder eukaryotic translation in vitro. These new targets and effects might be partially responsible for the plethora of adverse effects by these potent bactericidal agents.

Research has been conducted on opportunistic pathogen Bacteriodes fragilis. Results demonstrate that plasmid-encoded Hin invertase homologue which is present in B. fragilis binds to the invertible regions.