For the past several decades, we have been able to directly probe the motion of atoms that is associated with chemical transformations and which occurs on the femtosecond (10−15-s) timescale. ...However, studying the inner workings of atoms and molecules on the electronic timescale has become possible only with the recent development of isolated attosecond (10−18-s) laser pulses. Such pulses have been used to investigate atomic photoexcitation and photoionization and electron dynamics in solids, and in molecules could help explore the prompt charge redistribution and localization that accompany photoexcitation processes. In recent work, the dissociative ionization of H2 and D2 was monitored on femtosecond timescales and controlled using few-cycle near-infrared laser pulses. Here we report a molecular attosecond pump-probe experiment based on that work: H2 and D2 are dissociatively ionized by a sequence comprising an isolated attosecond ultraviolet pulse and an intense few-cycle infrared pulse, and a localization of the electronic charge distribution within the molecule is measured that depends-with attosecond time resolution-on the delay between the pump and probe pulses. The localization occurs by means of two mechanisms, where the infrared laser influences the photoionization or the dissociation of the molecular ion. In the first case, charge localization arises from quantum mechanical interference involving autoionizing states and the laser-altered wavefunction of the departing electron. In the second case, charge localization arises owing to laser-driven population transfer between different electronic states of the molecular ion. These results establish attosecond pump-probe strategies as a powerful tool for investigating the complex molecular dynamics that result from the coupling between electronic and nuclear motions beyond the usual Born-Oppenheimer approximation.
Ovule formation is a complex developmental process in plants, with a strong impact on the production of seeds. Ovule primordia initiation is controlled by a gene network, including components of the ...signaling pathways of auxin, brassinosteroids and cytokinins. By contrast, gibberellins (GAs) and DELLA proteins, the negative regulators of GA signaling, have never been shown to be involved in ovule initiation. Here, we provide molecular and genetic evidence that points to DELLA proteins as novel players in the determination of ovule number in
and in species of agronomic interest, such as tomato and rapeseed, adding a new layer of complexity to this important developmental process. DELLA activity correlates positively with ovule number, acting as a positive factor for ovule initiation. In addition, ectopic expression of a dominant DELLA in the placenta is sufficient to increase ovule number. The role of DELLA proteins in ovule number does not appear to be related to auxin transport or signaling in the ovule primordia. Possible crosstalk between DELLA proteins and the molecular and hormonal network controlling ovule initiation is also discussed.
Quorum sensing (QS) is a bacterial cell-cell communication process that relies on the production and detection of extracellular signal molecules called autoinducers. QS allows bacteria to perform ...collective activities. Vibrio cholerae, a pathogen that causes an acute disease, uses QS to repress virulence factor production and biofilm formation. Thus, molecules that activate QS in V. cholerae have the potential to control pathogenicity in this globally important bacterium. Using a whole-cell high-throughput screen, we identified eleven molecules that activate V. cholerae QS: eight molecules are receptor agonists and three molecules are antagonists of LuxO, the central NtrC-type response regulator that controls the global V. cholerae QS cascade. The LuxO inhibitors act by an uncompetitive mechanism by binding to the pre-formed LuxO-ATP complex to inhibit ATP hydrolysis. Genetic analyses suggest that the inhibitors bind in close proximity to the Walker B motif. The inhibitors display broad-spectrum capability in activation of QS in Vibrio species that employ LuxO. To the best of our knowledge, these are the first molecules identified that inhibit the ATPase activity of a NtrC-type response regulator. Our discovery supports the idea that exploiting pro-QS molecules is a promising strategy for the development of novel anti-infectives.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Effects of high-pressure shift freezing (HPSF) at 200 MPa/-20 °C on physical, functional and thermal properties of egg white and egg yolk from three egg types were studied. The phase transition time ...in HPSF was shorter compared to atmospheric freezing (about 25% for egg yolk and 56% for egg white) due to the high degree of supercooling. The effect of freezing on functional properties seems to be related to different degrees of protein denaturation depending of the freezing/pressure level. Partial protein unfolding (suggested by higher free sulfhydryl) was observed after freezing at atmospheric pressure, especially for egg yolk. On the other hand, higher protein aggregation due to lower thermal denaturation enthalpy (50% in egg yolk and 70% in egg white) was found in HPSF samples, supported by decrease of protein solubility, disappear of electrophoretic bands and increase in viscoelasticity (G′ and G″ values).
•Egg white and yolk of three eggs types were frozen under high-pressure shift freezing (HPSF).•HPSF process led to a significant reduction in the phase transition time.•Egg yolk was more affected by the freezing process, with less change at atmospheric pressure.•Freezing induced gelling of yolk egg and aggregation of white egg proteins.
Most tumours have an aberrantly activated lipid metabolism
that enables them to synthesize, elongate and desaturate fatty acids to support proliferation. However, only particular subsets of cancer ...cells are sensitive to approaches that target fatty acid metabolism and, in particular, fatty acid desaturation
. This suggests that many cancer cells contain an unexplored plasticity in their fatty acid metabolism. Here we show that some cancer cells can exploit an alternative fatty acid desaturation pathway. We identify various cancer cell lines, mouse hepatocellular carcinomas, and primary human liver and lung carcinomas that desaturate palmitate to the unusual fatty acid sapienate to support membrane biosynthesis during proliferation. Accordingly, we found that sapienate biosynthesis enables cancer cells to bypass the known fatty acid desaturation pathway that is dependent on stearoyl-CoA desaturase. Thus, only by targeting both desaturation pathways is the in vitro and in vivo proliferation of cancer cells that synthesize sapienate impaired. Our discovery explains metabolic plasticity in fatty acid desaturation and constitutes an unexplored metabolic rewiring in cancers.
Respiratory syncytial virus (RSV) is the most frequent cause of hospitalization and an important cause of death in infants in the developing world. The relative contribution of social, biologic, and ...clinical risk factors to RSV mortality in low-income regions is unclear.
To determine the burden and risk factors for mortality due to RSV in a low-income population of 84,840 infants.
This was a prospective, population-based, cross-sectional, multicenter study conducted between 2011 and 2013. Hospitalizations and deaths due to severe lower respiratory tract illness (LRTI) were recorded during the RSV season. All-cause hospital deaths and community deaths were monitored. Risk factors for respiratory failure (RF) and mortality due to RSV were assessed using a hierarchical, logistic regression model.
A total of 2,588 (65.5%) infants with severe LRTI were infected with RSV. A total of 157 infants (148 postneonatal) experienced RF or died with RSV. RSV LRTI accounted for 57% fatal LRTI tested for the virus. A diagnosis of sepsis (odds ratio OR, 17.03; 95% confidence interval CI, 13.14-21.16 for RF) (OR, 119.39; 95% CI, 50.98-273.34 for death) and pneumothorax (OR, 17.15; 95% CI, 13.07-21.01 for RF) (OR, 65.49; 95% CI, 28.90-139.17 for death) were the main determinants of poor outcomes.
RSV was the most frequent cause of mortality in low-income postneonatal infants. RF and death due to RSV LRTI, almost exclusively associated with prematurity and cardiopulmonary diseases in industrialized countries, primarily affect term infants in a developing world environment. Poor outcomes at hospitals are frequent and associated with the cooccurrence of bacterial sepsis and clinically significant pneumothoraxes.
The connection between pharmacokinetic models and system theory has been established for a long time. In this approach, the drug concentration is seen as the output of a system whose input is the ...drug administered at different times. In this article we further explore this connection. We show that system theory can be used to easily accommodate any therapeutic regime, no matter its complexity, allowing the identification of the pharmacokinetic parameters by means of a non-linear regression analysis. We illustrate how to exploit the properties of linear systems to identify non-linearities in the pharmacokinetic data. We also explore the use of bootstrapping as a way to compare populations of pharmacokinetic parameters and how to handle the common situation of using multiple hypothesis tests as a way to distinguish two different populations. Finally, we demonstrate how the bootstrap values can be used to estimate the distribution of derived parameters, as can be the allometric scale factors.
Background
The presence of SARS‐CoV‐2 RNA in plasma has been linked to disease severity and mortality. We compared RT‐qPCR to droplet digital PCR (ddPCR) to detect SARS‐CoV‐2 RNA in plasma from ...COVID‐19 patients (mild, moderate, and critical disease).
Methods
The presence/concentration of SARS‐CoV‐2 RNA in plasma was compared in three groups of COVID‐19 patients (30 outpatients, 30 ward patients and 30 ICU patients) using both RT‐qPCR and ddPCR. Plasma was obtained in the first 24h following admission, and RNA was extracted using eMAG. ddPCR was performed using Bio‐Rad SARS‐CoV‐2 detection kit, and RT‐qPCR was performed using GeneFinder™ COVID‐19 Plus RealAmp Kit. Statistical analysis was performed using Statistical Package for the Social Science.
Results
SARS‐CoV‐2 RNA was detected, using ddPCR and RT‐qPCR, in 91% and 87% of ICU patients, 27% and 23% of ward patients and 3% and 3% of outpatients. The concordance of the results obtained by both methods was excellent (Cohen's kappa index = 0.953). RT‐qPCR was able to detect 34/36 (94.4%) patients positive for viral RNA in plasma by ddPCR. Viral RNA load was higher in ICU patients compared with the other groups (P < .001), by both ddPCR and RT‐qPCR. AUC analysis revealed Ct values (RT‐qPCR) and viral RNA load values (ddPCR) can similarly differentiate between patients admitted to wards and to the ICU (AUC of 0.90 and 0.89, respectively).
Conclusion
Both methods yielded similar prevalence of RNAemia between groups, with ICU patients showing the highest (>85%). RT‐qPCR was as useful as ddPCR to detect and quantify SARS‐CoV‐2 RNAemia in plasma.
Vibrio cholerae, the causative agent of the disease cholera, uses a cell to cell communication process called quorum sensing to control biofilm formation and virulence factor production. The major V. ...cholerae quorum-sensing signal CAI-1 has been identified as (S)-3-hydroxytridecan-4-one, and the CqsA protein is required for CAI-1 production. However, the biosynthetic route to CAI-1 remains unclear. Here we report that (S)-adenosylmethionine (SAM) is one of the two biosynthetic substrates for CqsA. CqsA couples SAM and decanoyl-coenzyme A to produce a previously unknown but potent quorum-sensing molecule, 3-aminotridec-2-en-4-one (Ea-CAI-1). The CqsA mechanism is unique; it combines two enzymatic transformations, a β,γ-elimination of SAM and an acyltransferase reaction into a single PLP-dependent catalytic process. Ea-CAI-1 is subsequently converted to CAI-1, presumably through the intermediate tridecane-3,4-dione (DK-CAI-1). We propose that the Ea-CAI-1 to DK-CAI-1 conversion occurs spontaneously, and we identify the enzyme responsible for the subsequent step: conversion of DK-CAI-1 into CAI-1. SAM is the substrate for the synthesis of at least three different classes of quorum-sensing signal molecules, indicating that bacteria have evolved a strategy to leverage an abundant substrate for multiple signaling purposes.
Background
Anti‐SARS‐CoV‐2 S antibodies prevent viral replication. Critically ill COVID‐19 patients show viral material in plasma, associated with a dysregulated host response. If these antibodies ...influence survival and viral dissemination in ICU‐COVID patients is unknown.
Patients/Methods
We studied the impact of anti‐SARS‐CoV‐2 S antibodies levels on survival, viral RNA‐load in plasma, and N‐antigenaemia in 92 COVID‐19 patients over ICU admission.
Results
Frequency of N‐antigenaemia was >2.5‐fold higher in absence of antibodies. Antibodies correlated inversely with viral RNA‐load in plasma, representing a protective factor against mortality (adjusted HR CI 95%, p): (S IgM AUC ≥ 60: 0.44 0.22; 0.88, 0.020); (S IgG AUC ≥ 237: 0.31 0.16; 0.61, <0.001). Viral RNA‐load in plasma and N‐antigenaemia predicted increased mortality: (N1‐viral load ≥2.156 copies/ml: 2.25 1.16; 4.36, 0.016); (N‐antigenaemia: 2.45 1.27; 4.69, 0.007).
Conclusions
Low anti‐SARS‐CoV‐2 S antibody levels predict mortality in critical COVID‐19. Our findings support that these antibodies contribute to prevent systemic dissemination of SARS‐CoV‐2.
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