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At least 1,243 records · Page 69

Pseudomonas aeruginosa Dps (PA0962) Functions in H 2 O 2 Mediated Oxidative Stress Defense and Exhibits In Vitro DNA Cleaving Activity

We report the structural, biochemical, and functional characterization of the product of gene PA0962 from Pseudomonas aeruginosa PAO1. The protein, termed Pa Dps, adopts the Dps subunit fold and oligomerizes into a nearly spherical 12-mer quaternary structure at pH 6.0 or in the presence of divalent cations at neutral pH and above. The 12-Mer Pa Dps contains two di-iron centers at the interface of each subunit dimer, coordinated by conserved His, Glu, and Asp residues. In vitro, the di-iron centers catalyze the oxidation of Fe 2+ utilizing H 2 O 2 (not O 2 ) as an oxidant, suggesting Pa Dps functions to aid P. aeruginosa to survive H 2 O 2 -mediated oxidative stress. In agreement, a P. aeruginosa Δdps mutant is significantly more susceptible to H 2 O 2 than the parent strain. The Pa Dps structure harbors a novel network of Tyr residues at the interface of each subunit dimer between the two di-iron centers, which captures radicals generated during Fe 2+ oxidation at the ferroxidase centers and forms di-tyrosine linkages, thus effectively trapping the radicals within the Dps shell. Surprisingly, incubating Pa Dps and DNA revealed unprecedented DNA cleaving activity that is independent of H 2 O 2 or O 2 but requires divalent cations and 12-mer Pa Dps.

59 BASIC BIOLOGICAL SCIENCES↗

A Multiomic Approach to Understand How Pleurotus eryngii Transforms Non-Woody Lignocellulosic Material

Pleurotus eryngii is a grassland-inhabiting fungus of biotechnological interest due to its ability to colonize non-woody lignocellulosic material. Genomic, transcriptomic, exoproteomic, and metabolomic analyses were combined to explain the enzymatic aspects underlaying wheat–straw transformation. Up-regulated and constitutive glycoside–hydrolases, polysaccharide–lyases, and carbohydrate–esterases active on polysaccharides, laccases active on lignin, and a surprisingly high amount of constitutive/inducible aryl–alcohol oxidases (AAOs) constituted the suite of extracellular enzymes at early fungal growth. Higher enzyme diversity and abundance characterized the longer-term growth, with an array of oxidoreductases involved in depolymerization of both cellulose and lignin, which were often up-regulated since initial growth. These oxidative enzymes included lytic polysaccharide monooxygenases (LPMOs) acting on crystalline polysaccharides, cellobiose dehydrogenase involved in LPMO activation, and ligninolytic peroxidases (mainly manganese-oxidizing peroxidases), together with highly abundant H2O2-producing AAOs. Interestingly, some of the most relevant enzymes acting on polysaccharides were appended to a cellulose-binding module. This is potentially related to the non-woody habitat of P. eryngii (in contrast to the wood habitat of many basidiomycetes). Additionally, insights into the intracellular catabolism of aromatic compounds, which is a neglected area of study in lignin degradation by basidiomycetes, were also provided. The multiomic approach reveals that although non-woody decay does not result in dramatic modifications, as revealed by detailed 2D-NMR and other analyses, it implies activation of the complete set of hydrolytic and oxidative enzymes characterizing lignocellulose-decaying basidiomycetes.

59 BASIC BIOLOGICAL SCIENCES↗

Evidence for a cytokine-sensitive network of iron-associated genes that protects pancreatic islets against ferroptosis

Background/Objectives: The micronutrient iron is closely connected to inflammation and is among the complex factors contributing to beta-cell failure in diabetes. High levels of dietary iron increase the risk of developing type 2 diabetes, and excessive iron uptake by beta-cells can cause oxidative stress and inhibit function. Elevated levels of proinflammatory cytokines in obese individuals, such as interleukin (IL)-1beta and IL-6, increase the risk of developing type 2 diabetes, and there is evidence that these low levels of circulating cytokines can lead to islet dysfunction. Methods: In this study, gene microarray and other data were analyzed for expression differences in islets treated for 48 h with 10 pg/mL IL-1beta + 20 pg/mL IL-6 as a model of low-grade inflammation versus untreated. Results: Three iron-associated genes were among the most cytokine-sensitive in the mouse genome: Hamp, Steap4, and Lcn2. These proteins are all involved with increasing/retaining cellular iron. We hypothesized that increased cellular iron would lead to increased susceptibility to ferroptosis. Surprisingly, 24 h pre-exposure to low-grade inflammation, which upregulates this iron-gene network, prevented subsequent erastin-induced ferroptosis. We also found that Steap4 overexpression reduced islet dysfunction caused by high-dose proinflammatory cytokines (10× low-dose), suggesting an overall protective effect. Steap4 overexpression also upregulated Hamp and Lcn2, suggesting Steap4 regulates these cytokine-sensitive iron genes.; in contrast, ferritin and ferroportin gene expression, which are not sensitive to cytokines, were unchanged. Conclusions: These data suggest an inflammation-induced network of genes involved in cellular iron uptake and retention plays a protective role in islets against oxidative stress and ferroptosis.

IL-1β↗

YPK9 and WHI2 Negatively Interact during Oxidative Stress

Yeast PARK9 (YPK9) shares homology with human ATP13A2, which encodes a polyamine transporter implicated in juvenile forms of Parkinson’s disease. We used YPK9 to gain insight into how ATP13A2 affects cell growth and sensitivity to oxidative stress. Surprisingly, the YPK9 deletion strain from the Saccharomyces cerevisiae deletion collection (YKO) in wildtype BY4741 (mating type a) grew faster and was more resistant to hydrogen peroxide than a commercial, putative parental BY4741 wildtype strain (BY4741 COM ). In contrast, deleting YPK9 from BY4741 COM rendered it very sensitive to hydrogen peroxide, suggesting its background is different from that of the deletion collection. Whole-genome sequencing revealed that BY4741 COM and BY4741 COM ypk9Δ contain a novel premature stop codon near the 3' end of WHI2 (WHI2 G1324T ), whereas the collection’s YPK9 deletion strain contains WHI2, which encodes a 486 amino acid protein, Whi2p. Replacing full-length WHI2 with the sequence coding for the predicted truncation (Whi2p E442* ) rendered strains more sensitive to hydrogen peroxide, whereas the converse replacement rendered them more resistant. The sequences of WHI2 in 20 randomly chosen strains from the collection encode the full-length protein, indicating that the putative parental BY4741 WHI2 G1324T strain’s genetic background differs from that of the deletion collection. Examination of WHI2 sequences in several commonly used wildtype S. cerevisiae strains and isolates revealed other Whi2p truncations that might yield altered phenotypes. Together, these results demonstrate a novel premature stop codon in WHI2 that renders yeast sensitive to hydrogen peroxide; they also reveal a negative genetic interaction between WHI2 and YPK9 in the presence of hydrogen peroxide in the BY4741 background.

59 BASIC BIOLOGICAL SCIENCES↗

Computational and Experimental 1H-NMR Study of Hydrated Mg-Based Minerals

Magnesium oxide (MgO) can convert to different magnesium-containing compounds depending on exposure and environmental conditions. Many MgO-based phases contain hydrated species allowing 1H-nuclear magnetic resonance (NMR) spectroscopy to be used in the characterization and quantification of proton-containing phases; however, surprisingly limited examples have been reported. Here, 1H-magic angle spinning (MAS) NMR spectra of select Mg-based minerals are presented and assigned. These experimental results are combined with computational NMR density functional theory (DFT) periodic calculations to calibrate the predicted chemical shielding results. This correlation is then used to predict the NMR shielding for a series of different MgO hydroxide, magnesium chloride hydrate, magnesium perchlorate, and magnesium cement compounds to aid in the future assignment of 1H-NMR spectra for complex Mg phases.

1H-NMR↗

Photo-Switching of Protein Dynamical Collectivity

We examine changes in the picosecond structural dynamics with irreversible photobleaching of red fluorescent proteins (RFP) mCherry, mOrange2 and TagRFP-T. Measurements of the protein dynamical transition using terahertz time-domain spectroscopy show in all cases an increase in the turn-on temperature in the bleached state. The result is surprising given that there is little change in the protein surface, and thus, the solvent dynamics held responsible for the transition should not change. A spectral analysis of the measurements guided by quasiharmonic calculations of the protein absorbance reveals that indeed the solvent dynamical turn-on temperature is independent of the thermal stability/photostate however the protein dynamical turn-on temperature shifts to higher temperatures. This is the first demonstration of switching the protein dynamical turn-on temperature with protein functional state. The observed shift in protein dynamical turn-on temperature relative to the solvent indicates an increase in the required mobile waters necessary for the protein picosecond motions, that is, these motions are more collective. Melting-point measurements reveal that the photobleached state is more thermally stable, and structural analysis of related RFP’s shows that there is an increase in internal water channels as well as a more uniform atomic root mean squared displacement. These observations are consistent with previous suggestions that water channels form with extended light excitation providing O2 access to the chromophore and subsequent fluorescence loss. We report that these same channels increase internal coupling enhancing thermal stability and collectivity of the picosecond protein motions. The terahertz spectroscopic characterization of the protein and solvent dynamical onsets can be applied generally to measure changes in collectivity of protein motions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Structure of the Diphtheria Toxin at Acidic pH: Implications for the Conformational Switching of the Translocation Domain

Diphtheria toxin, an exotoxin secreted by Corynebacterium that causes disease in humans by inhibiting protein synthesis, enters the cell via receptor-mediated endocytosis. The subsequent endosomal acidification triggers a series of conformational changes, resulting in the refolding and membrane insertion of the translocation (T-)domain and ultimately leading to the translocation of the catalytic domain into the cytoplasm. Here, we use X-ray crystallography along with circular dichroism and fluorescence spectroscopy to gain insight into the mechanism of the early stages of pH-dependent conformational transition. For the first time, we present the high-resolution structure of the diphtheria toxin at a mildly acidic pH (5–6) and compare it to the structure at neutral pH (7). We demonstrate that neither catalytic nor receptor-binding domains change their structure upon this acidification, while the T-domain undergoes a conformational change that results in the unfolding of the TH2–3 helices. Surprisingly, the TH1 helix maintains its conformation in the crystal of the full-length toxin even at pH 5. This contrasts with the evidence from the new and previously published data, obtained by spectroscopic measurements and molecular dynamics computer simulations, which indicate the refolding of TH1 upon the acidification of the isolated T-domain. The overall results imply that the membrane interactions of the T-domain are critical in ensuring the proper conformational changes required for the preparation of the diphtheria toxin for the cellular entry.

59 BASIC BIOLOGICAL SCIENCES↗

Estimation of the Chances to Find New Phenomena at the LHC in a Model-Agnostic Combinatorial Analysis

In this paper, we estimate the number of event topologies that have the potential to be produced in 𝑝𝑝 collisions at the Large Hadron Collider (LHC) without violating kinematic and other constraints. We use numerical calculations and combinatorics, guided by large-scale Monte Carlo simulations of Standard Model (SM) processes. Then, we set the upper limit on the probability that new physics may escape detection, assuming a model-agnostic approach. The calculated probability is unexpectedly large, and the fact that LHC has not found new physics until now is not entirely surprising. Theoretical limitations and experimental challenges in observing new physics within the studied exclusive event classes are examined.

BSM↗

Evaluation of the Function of the ASFV KP177R Gene, Encoding for Structural Protein p22, in the Process of Virus Replication and in Swine Virulence

African swine fever virus (ASFV) causes a devastating disease of swine that has caused outbreaks in Central Europe since 2007, spreading into Asia in 2018. ASFV is a large, structurally complex virus with a large dsDNA genome encoding for more than 160 genes, most of them still uncharacterized. p22, encoded by the ASFV gene KP177R, is an early transcribed, structural virus protein located in the ASFV particle. Although its exact function is unknown, p22 has recently been identified as an interacting partner of several host proteins. Here, we describe the development of a recombinant ASFV (ASFV-G-ΔKP177R) lacking the KP177R gene as a tool to evaluate the role of p22 in virus replication and virulence in swine. The recombinant ASFV-G-ΔKP177R demonstrated that the KP177R gene is non-essential for ASFV replication in primary swine macrophages, with virus yields similar to those of the parental, highly virulent field isolate Georgia2010 (ASFV-G). In addition, experimental infection of domestic pigs with ASFV-G-ΔKP177R produced a clinical disease similar to that caused by the parental ASFV-G. Therefore, and surprisingly, p22 does not seem to be involved in virus replication or virulence in swine.

59 BASIC BIOLOGICAL SCIENCES↗

Growth and Stability of Stratiform Carrollite (CuCo2S4) in the Tenke-Fungurume Ore District, Central African Copperbelt

Abstract Carrollite (CuCo2S4) is the main ore mineral of the critical battery metal cobalt, yet, surprisingly, detailed characterization of its thermodynamic properties and of its trace element contents remain sparse in the scientific literature. To fill these knowledge gaps, we generated the first thermodynamic data set for carrollite using well-characterized samples obtained from the stratiform sulfide mineralization style at Fungurume 88 deposit in the Democratic Republic of Congo. Detailed mineralogical investigation of these same samples suggests that carrollite has limited ability to incorporate other ‘sweetener’ elements (except Cu and Ni) by substitution mechanisms. Modeling using CHNOSZ 2.0.0. software and an integrated Cu-Co-S-O thermodynamic data set provides insights into the stability of carrollite relative to other Co-bearing minerals under physicochemical conditions relevant to the Central African Copperbelt. Further exploration of these models indicates that dropping redox potential in the mineralizing system is insufficient to explain the mineral-scale and deposit-scale zonation patterns commonly observed in Cu-Co deposits of the Central African Copperbelt. Instead, factors such as increasing pH, decreasing T, decreasing sulfur activity, or some combination of changing physicochemical parameters may need to be invoked to explain these zonation trends. At the Fungurume 88 deposit, the absence of linnaeite (Co3S4) suggests that ore precipitation occurred at temperatures cooler than 211 °C. From our pH-logfO2 diagrams, and relative to higher temperatures, such a lower T regime is marked by a greater degree of offset between the modeled Cu and Co solubility contours, thus facilitating a more differentiated and zoned distribution of these two metals at the deposit scale. Our models are offered to the geoscience community as exceptionally useful tools for modeling and visualizing the Cu-Co-S-O systematics and may be applied to a variety of geological and geometallurgical questions in the Central African Copperbelt and other deposits elsewhere.

Mineralogy↗

Voyager 1 and 2 Observations of a Change in the Nature of Magnetic Fluctuations in the VLISM with Increasing Distance from the Heliopause

Voyager 2 (V2) crossed the heliopause at 119.0 au on 2018 day 309, after which it observed compressive (longitudinal) magnetic field fluctuations along the average magnetic field direction in the very local interstellar medium (VLISM) at distances from 119.00 to 121.48 au and latitudes 32.°2 to 32.°4 S in heliographic inertial coordinates from 2018 day 309 to 2019 day 230. This result confirms the observations of longitudinal magnetic field fluctuations by Voyager 1 (V1) between 124.14 and 128.71 au at 34.°6N (∼2–7 au upwind of the heliopause) from 2013 day 133 to 2014 day 235. V1 crossed the heliopause at 121.58 au and 34.°5N on 2012 day 238. It came as a surprise to find it seemed that V1 observed transverse (Alfvénic) fluctuations of B between 131.40 and 135.98 au at latitude 34.°6–34.°7N (∼10–14 au upwind of the heliopause) from 2015 day 145 to 2016 day 248. The most recent V1 observations show the possible presence of transverse fluctuations of B in the VLISM from 141.44 to 146.01 au at 34.°7–34.°8N (∼20–24 au from the heliopause) between 2018 day 75 and 2019 day 178. Together, these observations show that longitudinal (compressive) magnetic field fluctuations are transmitted through the heliopause from the heliosheath into the VLISM, and are then converted into transverse (Alfvénic) fluctuations at ∼130 au (∼8 au from the heliopause) that are observed out at 146 au (∼24 au from the heliopause).

79 ASTRONOMY AND ASTROPHYSICS↗

Emission-line Data Cubes of the HH 32 Stellar Jet

We analyze data cubes of over 60 emission lines in the HH 32 stellar jet acquired with the Keck Cosmic Web Imager (KCWI). The data cover the less explored blue portion of the spectrum between 3586 and 6351 Å and have both high spectral (R ∼ 10,000) and spatial (≲1″) resolution. The study includes all three major ionization states of oxygen, three Balmer lines, multiple lines of Fe ii and Fe iii, and the first data cubes ever acquired for important unblended diagnostic lines such as He ii λ4686, Ca i λ3933, and Mg i] λ4571. The data cubes generally sort according to excitation and have a relatively continuous progression from the highest-excitation ions (He ii, O iii) through the intermediate-excitation ions (O i and H i) to the lowest-excitation ions (Ca ii and Mg i). Merging the KCWI cubes with Hubble Space Telescope images leads to several new insights about the flow, including evidence for bow shocks, partial bow shocks, spur shocks, Mach disks, jet deflection shocks, a wiggling jet, and potential shock precursors. The most surprising result is that one of the velocity components of Fe ii in the Mach disk suddenly increases in flux relative to other lines by a factor of two, implying that the Mach disk vaporizes dust in the jet. Hence, jets must accelerate or entrain dust to speeds of over 300 km s{sup −1} without destroying the grains.

79 ASTRONOMY AND ASTROPHYSICS↗

Mean Estimate Distances for Galaxies with Multiple Estimates in NED-D

Numerous research topics rely on an improved cosmic distance scale (e.g., cosmology, gravitational waves) and the NASA/IPAC Extragalactic Database of Distances (NED-D) supports those efforts by tabulating multiple redshift-independent distances for 12,000 galaxies (e.g., Large Magellanic Cloud (LMC) zero-point). Six methods for securing a mean estimate distance (MED) from the data are presented (e.g., indicator and Decision Tree). All six MEDs yield surprisingly consistent distances for the cases examined, including for the key benchmark LMC and M106 galaxies. The results underscore the utility of the NED-D MEDs in bolstering the cosmic distance scale and facilitating the identification of systematic trends.

79 ASTRONOMY AND ASTROPHYSICS↗

Earth as a Proxy Exoplanet: Deconstructing and Reconstructing Spectrophotometric Light Curves

Point-source spectrophotometric (single-point) light curves of Earth-like planets contain a surprising amount of information about the spatial features of those worlds. Spatially resolving these light curves is important for assessing time-varying surface features and the existence of an atmosphere, which in turn is critical to life on Earth and significant for determining habitability on exoplanets. Given that Earth is the only celestial body confirmed to harbor life, treating it as a proxy exoplanet by analyzing time-resolved spectral images provides a benchmark in the search for habitable exoplanets. The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) provides such an opportunity, with observations of ∼5000 full-disk sunlit Earth images each year at 10 wavelengths with high temporal frequency. We disk-integrate these spectral images to create single-point light curves and decompose them into principal components (PCs). Using machine-learning techniques to relate the PCs to six preselected spatial features, we find that the first and fourth PCs of the single-point light curves, contributing ∼83.23% of the light-curve variability, contain information about low and high clouds, respectively. Surface information relevant to the contrast between land and ocean reflectance is contained in the second PC, while individual land subtypes are not easily distinguishable (<0.1% total light-curve variation). We build an Earth model by systematically altering the spatial features to derive causal relationships to the PCs. This model can serve as a baseline for analyzing Earth-like exoplanets and guide wavelength selection and sampling strategies for future observations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Environmental Effects in Herschel Observations of the Ionized Carbon Content of Star-forming Dwarf Galaxies in the Virgo Cluster

We use archival Herschel data to examine the singly ionized carbon ([C II]) content of 14 star-forming dwarf galaxies in the Virgo cluster. We use spectral energy distribution fits to far-infrared, mid-infrared, near-infrared, optical, and ultraviolet data to derive the total infrared continuum (TIR) for these galaxies. We compare the [C II]/TIR ratio for dwarf galaxies in the central part of Virgo to those in the southern part of the cluster and to galaxies with similar TIR luminosities and metallicities in the Herschel Dwarf Galaxy Survey (DGS) sample of field dwarf galaxies to look for signs of [C II] formation independent of star formation. Our analysis indicates that the sample of Virgo dwarfs in the central part of the cluster has significantly higher values of [C II]/TIR than the sample from the southern part of the cluster and the sample from the DGS, while the southern sample is consistent with the DGS. This [C II]/TIR excess implies that a significant fraction of the [C II] in the dwarf galaxies in the cluster center has an origin other than star formation and is likely to be due to environmental processes in the central part of the cluster. We also find a surprisingly strong correlation between [C II]/TIR and the local ram pressure felt by the dwarf galaxies in the cluster. In this respect, we claim that the excess [C II] we see in these galaxies is likely to be due to formation in ram-pressure shocks.

79 ASTRONOMY AND ASTROPHYSICS↗

Magnetogenesis by Wave-driven Momentum Exchange

When multiple species interact with an electrostatic ion acoustic wave, they can exchange momentum, despite the lack of momentum in the field itself. Furthermore, the resulting force on the electrons can have a curl, and thus give rise to compensating electric fields with curl on magnetohydrodynamic timescales. As a result, a magnetic field can be generated. Surprisingly, in some astrophysical settings, this mechanism can seed magnetic fields with growth rates even larger than through the traditional Biermann battery.

79 ASTRONOMY AND ASTROPHYSICS↗

Flux Ropes, Turbulence, and Collisionless Perpendicular Shock Waves: High Plasma Beta Case

With the onset of solar maximum and the expected increased prevalence of interplanetary shock waves, Parker Solar Probe is likely to observe numerous shocks in the next few years. An outstanding question that has received surprisingly little attention has been how turbulence interacts with collisionless shock waves. Turbulence in the supersonic solar wind is described frequently as a superposition of a majority 2D and a minority slab component. Here we formulate a collisional perpendicular shock-turbulence transmission problem in a way that enables investigation of the interaction and transmission of quasi-perpendicular fluctuations such as magnetic flux ropes/islands and vortices as well as entropy and acoustic modes in the large plasma beta regime. We focus on the transmission of an upstream spectrum of these modes, finding that the downstream spectral amplitude is typically increased significantly (a factor of 10 or more), and that the upstream spectral index of the inertial range, and indeed the general spectral shape, is unchanged for the downstream magnetic variance, kinetic energy, and density variance. A comparison of the theoretically predicted downstream magnetic variance, kinetic energy, and density variance spectra with those observed at 1, 5, and 84 au by Wind, Ulysses, and Voyager 2 shows excellent agreement. The overall theoretically predicted characteristics of the transmission of turbulence across shocks observed in the solar wind appear to be largely consistent with recent observational studies by Pitňa et al. and Borovsky.

79 ASTRONOMY AND ASTROPHYSICS↗

A Possible Tidal Disruption Event Candidate in the Black Hole Binary System of OJ 287

The BL Lacertae OJ 287 is a supermassive black hole binary system with complex physics of its irregular flares. During 2016 October–2017 April, a surprising outburst in the X-ray, UV, and optical bands was detected, while no variability was seen in the γ-ray light curve. During the outburst, the X-ray light curves were dominated by the soft X-rays, whose peak in luminosity was ~10 46 erg s -1 —more than 10 times higher than the mean level before the outburst—and a "softer-when-brighter" phenomenon was exhibited. These above phenomena have been reported by some previous works. The hardness ratio showed negligible evolution with flare time and soft X-ray luminosity. Critically, the luminosity of the soft X-rays decayed following a power law of $t$ -5/3 , which occurs in most tidal disruption events (TDEs), and a similar trend can be seen in the UV and optical bands during the soft X-ray declining period. Helium and oxygen narrow emission lines are strengthened prominently in the optical spectra of post outburst epochs, that could be attributed to the surrounding gas caused by TDE. In conclusion, we discuss three possible origins of the event, including the jet's precession, the aftereffects of the black hole–disk impaction, and the TDE. Our results show that the TDE is the more likely scenario to explain the outburst.

79 ASTRONOMY AND ASTROPHYSICS↗