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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Analyzing impact of $\mathrm{DER}$ on $\mathrm{FIDVR}$ - comparison of $\mathrm{EMT}$ simulation of a combined transmission and distribution grid with aggregated positive sequence models

The increase in percentage of distributed energy resources (DERs) brings in a degree of uncertainty in bulk power system planning and operations. Further, the presence of 1 - φ induction motors introduces the possibility of motor stalling and fault induced delayed voltage recovery (FIDVR). With newer versions of IEEE Std 1547™ there can be the opportunity to obtain dynamic voltage support from DERs. In this report, the impact of DERs providing dynamic voltage on the dynamic behavior of 1 - φ induction motors is examined in detail along with an exploration of the need for simulation platforms that go beyond positive sequence. The studies discussed here are carried out both in detailed electromagnetic time domain and in positive sequence domain for comparison.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Tradeoffs in forest resilience to satellite-based estimates of water and productivity losses

Climate change is expected to intensify the global hydrological cycle via increased evapotranspiration (ET). Changes in ET have important consequences for water-related ecosystem services as well as for forest productivity. Forests play a critical role in ET: active trees sequester carbon at the expense of losing water, yet if they are not active, water remains in the trees, but productivity stalls. Here, we estimated the capacity of forests to recover (resilience) from extreme water or productivity losses based on modeled ET through remote sensing methods across the conterminous USA. Results show there is a spatial tradeoff in resilience to water or productivity losses. Forests were more resilient to water loss in the drier west, and more resilient to productivity loss in the wetter east. Still, resilience was highly heterogeneous across the continent. Projections under climate change indicate both declines and increases of up to 13% in forest resilience, with broad regional trends but high spatial heterogeneity within regions. This study brings crucial satellite-based insights on how water dynamics, and consequentially productivity and water provision in forests, might be impacted by climate change.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

A bimodular PKS platform that expands the biological design space

Traditionally engineered to produce novel bioactive molecules, Type I modular polyketide synthases (PKSs) could be engineered as a new biosynthetic platform for the production of de novo fuels, commodity chemicals, and specialty chemicals. Previously, our investigations manipulated the first module of the lipomycin PKS to produce short chain ketones, 3-hydroxy acids, and saturated, branched carboxylic acids. Building upon this work, we have expanded to multi-modular systems by engineering the first two modules of lipomycin to generate unnatural polyketides as potential biofuels and specialty chemicals in Streptomyces albus. First, we produce 20.6 mg/L of the ethyl ketone, 4,6 dimethylheptanone through a reductive loop exchange in LipPKS1 and a ketoreductase knockouts in LipPKS2. Furthermore, we then show that an AT swap in LipPKS1 and a reductive loop exchange in LipPKS2 can produce the potential fragrance 3-isopropyl-6-methyltetrahydropyranone. Highlighting the challenge of maintaining product fidelity, in both bimodular systems we observed side products from premature hydrolysis in the engineered first module and stalled dehydration in reductive loop exchanges. Collectively, our work expands the biological design space and moves the field closer to the production of "designer" biomolecules.

09 BIOMASS FUELS↗
DOE OSTI2020

Structure and Function of BorB, the Type II Thioesterase from the Borrelidin Biosynthetic Gene Cluster

α/β hydrolases make up a large and diverse protein superfamily. In natural product biosynthesis, cis-acting thioesterase α/β hydrolases can terminate biosynthetic assembly lines and release products by hydrolyzing or cyclizing the biosynthetic intermediate. Thioesterases can also act in trans, removing aberrant intermediates and restarting stalled biosynthesis. Knockout of this "editing" function leads to reduced product titers. The borrelidin biosynthetic gene cluster from Streptomyces parvulus Tü4055 contains a hitherto uncharacterized stand-alone thioesterase, borB. In this work, we demonstrate that purified BorB cleaves acyl substrates with a preference for propionate, which supports the hypothesis that it is also an editing thioesterase. The crystal structure of BorB shows a wedgelike hydrophobic substrate binding crevice that limits substrate length. To investigate the structure-function relationship, we made chimeric BorB variants using loop regions from characterized homologues with different specificities. BorB chimeras slightly reduced activity, arguing that the modified region is a not major determinant of substrate preference. Overall, the structure-function relationships described here contribute to the process of elimination for understanding thioesterase specificity and, ultimately, engineering and applying trans-acting thioesterases in biosynthetic assembly lines.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Nonenergy Biomass Carbon Removal and Storage (BiCRS): Assessing Durability of Nongaseous Carbon Products Across Terrestrial Storage Fates

Biomass Carbon Removal and Storage, or BiCRS, pathways use plants or algae that remove carbon dioxide from the atmosphere through photosynthesis and store it underground or in long-lived products. While some BiCRS approaches generate an energy product, all BiCRS approaches generate a carbon product. A new subset of BiCRS approaches focus on the storage of these raw or converted carbon products for generation of carbon credits. However, the durability of these approaches is highly variable as carbon products vary widely in their “form” and the conditions of their “fate.” We organize our thinking about carbon products and their durability around these two primary axes. The durability of carbon product “forms” is mediated by chemical recalcitrance and ranges substantially across agricultural residues, municipal solid waste, woody biomass, and nongaseous products of thermochemical conversion (e.g., biochars and bio-oils). Meanwhile, terrestrial storage “fates” vary in the mechanism employed to stall decay, including surface storage, dry storage, shallow anoxic storage, and deep or geologic anoxic storage (or injection). Each mechanism has different implications for suitability with different feedstock forms as well as long-term risks. We present a framework for assessing durability of solid or liquid raw and conversion carbon products under terrestrial storage fates, highlighting knowns, unknowns, and research priorities moving forward.

09 BIOMASS FUELS↗
DOE OSTI2021

Cometabolic Vinyl Chloride Degradation at Acidic pH Catalyzed by Acidophilic Methanotrophs Isolated from Alpine Peat Bogs

Remediation of toxic chlorinated ethenes via microbial reductive dechlorination can lead to ethene formation; however, the process stalls in acidic groundwater, leading to the accumulation of carcinogenic vinyl chloride (VC). This study explored the feasibility of cometabolic VC degradation by moderately acidophilic methanotrophs. Furthermore, two novel isolates, Methylomonas sp. strain JS1 and Methylocystis sp. strain MJC1, were obtained from distinct alpine peat bogs located in South Korea. Both isolates cometabolized VC with CH 4 as the primary substrate under oxic conditions at pH at or below 5.5. VC cometabolism in axenic cultures occurred in the presence (10 μM) or absence (<0.01 μM) of copper, suggesting that VC removal had little dependence on copper availability, which regulates expression and activity of soluble and particulate methane monooxygenases in methanotrophs. The model neutrophilic methanotroph Methylosinus trichosporium strain OB3b also grew and cometabolized VC at pH 5.0 regardless of copper availability. Bioaugmentation of acidic peat soil slurries with methanotroph isolates demonstrated enhanced VC degradation and VC consumption below the maximum concentration level of 2 μg L –1 . Community profiling of the microcosms suggested species-specific differences, indicating that robust bioaugmentation with methanotroph cultures requires further research.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Reactivity and Mechanisms of Methane, Ethane, and Benzene C–H Amination with an Iodine(III) Bistriflimide Complex

The iodine(III) bistriflamide complex (C 6 F 5 ) III I(NTf 2 ) 2 in HNTf 2 (bistriflimide acid; (CF 3 SO 2 ) 2 NH) selectively aminates methane and ethane. At a 100 °C reaction with methane after 3 h, it resulted in the exclusive formation of MeNTf 2 with a yield of approximately 40%. For ethane, at 100 °C in 2 h, a > 80% yield was found for a combination of monofunctionalized and difunctionalized amination products. In contrast to alkanes giving functionalized products, the reaction of (C 6 F 5 ) III I(NTf 2 ) 2 with benzene resulted in being stalled at (C 6 F 5 )I III (Ph)(NTf 2 ) with a <5% conversion to PhNTf 2 even at 120 °C. PWPB95-D3(BJ) density functional theory calculations indicate that C–H activation is the lowest energy pathway to break the hydrocarbon bonds and is lower in energy than radical, electron-transfer, proton-coupled electron-transfer, or hydride substitution pathways. For methane, from the (C 6 F 5 )I III (CH 3 )(NTf 2 ) intermediate, there is a one-step amine functionalization mechanism that avoids a carbocation intermediate. For ethane, from the (C 6 F 5 )I III (Et)(NTf 2 ) intermediate, dynamics simulations suggest the possibility of a competitive two-step functionalization pathway that involves a short-lived carbocation intermediate. As a result, a reaction coordinate strain analysis provides a straightforward model for understanding the relative reactivity rates for alkyl versus aryl functionalization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Stability Criteria for Self-Propagating Reaction Waves in Co/Al Multilayers

The propagation of self-sustained formation reactions in sputter-deposited Co/Al multilayers is known to exhibit a design-dependent instability. Multilayers having thin bilayers (<55 nm period) exhibit stable propagating waves, whereas those with a larger period react unstably. The specific two-dimensional (2D) instability observed involves the transverse propagation of a band in front of a stalled front commonly referred to as a “spin band.” Previous finite-element studies have shown that these instabilities are thermodynamically driven by the forward conduction of heat away from the flame front. However, the magnitude of that loss is inherently tied to the bilayer design in traditional bimetallic multilayers, which couples any proposed stability criteria to a varying critical diffusion distance. Here, this work utilizes a recently developed class of materials known as “inert-mediated reactive multilayers” to decouple the thermodynamic and kinetic contributions to propagating wave stability by reducing the stored chemical energy density in normally stable bilayer designs. By depositing an inert product phase (B2-CoAl) within the mid-plane of Co and Al reactant layers, spin instabilities arise as a function of both diluted volume and critical diffusion distance. From there, a stability criterion is determined for Co/Al multilayers based on enthalpy loss from the reaction zone, and its physical significance is explored.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unusual Base Pair between Two 2-Thiouridines and Its Implication for Nonenzymatic RNA Copying

2-Thiouridine (s 2 U) is a nucleobase modification that confers enhanced efficiency and fidelity both on modern tRNA codon translation and on nonenzymatic and ribozyme-catalyzed RNA copying. We have discovered an unusual base pair between two 2-thiouridines that stabilizes an RNA duplex to a degree that is comparable to that of a native A:U base pair. High-resolution crystal structures indicate similar base-pairing geometry and stacking interactions in duplexes containing s 2 U:s 2 U compared to those with U:U pairs. Notably, the C=O···H–N hydrogen bond in the U:U pair is replaced with a C=S···H–N hydrogen bond in the s 2 U:s 2 U base pair. The thermodynamic stability of the s 2 U:s 2 U base pair suggested that this self-pairing might lead to an increased error frequency during nonenzymatic RNA copying. However, competition experiments show that s 2 U:s 2 U base-pairing induces only a low level of misincorporation during nonenzymatic RNA template copying because the correct A:s 2 U base pair outcompetes the slightly weaker s 2 U:s 2 U base pair. In addition, even if an s 2 U is incorrectly incorporated, the addition of the next base is greatly hindered. This strong stalling effect would further increase the effective fidelity of nonenzymatic RNA copying with s 2 U. Our findings suggest that s 2 U may enhance the rate and extent of nonenzymatic copying with only a minimal cost in fidelity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Formation of a Large Cold Groundwater Mantle Helium Anomaly and High Temperature Geothermal Resources in Response to Bimodal Magmatism Near Roosevelt Hot Springs and Utah FORGE, Milford Valley, Southwest Utah

Abstract A large mantle helium anomaly and separate domains of high heat flow are the predominant manifestations of bimodal magmatic activity in the Milford valley. The mantle helium anomaly (1.9–2.6 R/Ra) covers 270 km 2 and is subdivided into two separated domains: a cold shallow groundwater regime and high temperature hydrothermal activity. The zone of anomalous heat flow covers >100 km 2 and is also subdivided into two adjacent domains, comprising hydrothermal activity at Roosevelt Hot Springs (RHS) (3–7 W/m 2 ) and conductive heat flow (100–180 mW/m 2 ). While the transfer of heat and mantle helium at RHS are coupled, heat and helium transfer are decoupled in the adjacent cold groundwater regime to the west. Both the mantle helium and geothermal anomalies are attributed to recent mafic‐felsic magmatic intrusions of >400 km 3 , however, the absence of volcanic eruptions <500,000 years indicates magmas stall before rising to shallow crustal level <10 km depth. Deep level magmatism produces a felsic composition melt, which is inferred to be responsible for the widespread and near uniform range of diluted mantle helium values. A thick and impermeable mass of crystalline granitic basement rock at the mid‐crustal level divides the ascent of mantle helium into separate flow paths. It may also impede the rise of buoyant magma trapping thermal energy that facilitates partial melting, slow cooling, and development of a thick thermal aureole. Partitioning of convective and conductive thermal regimes and independent flow paths supplying deeply derived helium characterize the development of a large long‐lived magma‐related geothermal system.

Geochemistry & Geophysics↗
DOE OSTI2025

Role of Diurnal Cycle of Insolation on the MJO Propagation in the Maritime Continent

The diurnal cycle of convection in the Maritime Continent (MC) has been hypothesized to act as a barrier to the eastward propagation of the Madden‐Julian oscillation (MJO). To test this hypothesis, we use a regional model with realistic MJO to simulate an event from the boreal spring of 2013 that weakened and stalled over the MC. Two simulations are conducted: one that includes the diurnal cycle of insolation (CTL), and another without it (NO_DC). The MJO in the simulations was identified and tracked using a large‐scale precipitation tracking method that distinguishes propagation and non‐propagation unlike the usual Real‐time Multivariate MJO method. In the NO_DC simulation, the absence of diurnal heating reduces land precipitation, allowing more continuous eastward MJO propagation. An analysis of moist static energy budget reveals that MJO maintenance in NO_DC is due to increased longwave heating and reduced advection, whereas the persistent MJO propagation in NO_DC is due to increased advection and reduced longwave heating and surface latent heat flux. These processes, however, may vary across different parts of the MC, emphasizing the complexity of MJO propagation across the MC.

Zhou, Xin [National Center for Atmospheric Researc↗
DOE OSTI2020

Selective inhibition of human translation termination by a drug-like compound

Methods to directly inhibit gene expression using small molecules hold promise for the development of new therapeutics targeting proteins that have evaded previous attempts at drug discovery. Among these, small molecules including the drug-like compound PF-06446846 (PF846) selectively inhibit the synthesis of specific proteins, by stalling translation elongation. These molecules also inhibit translation termination by an unknown mechanism. Using cryo-electron microscopy (cryo-EM) and biochemical approaches, we show that PF846 inhibits translation termination by arresting the nascent chain (NC) in the ribosome exit tunnel. The arrested NC adopts a compact α-helical conformation that induces 28 S rRNA nucleotide rearrangements that suppress the peptidyl transferase center (PTC) catalytic activity stimulated by eukaryotic release factor 1 (eRF1). These data support a mechanism of action for a small molecule targeting translation that suppresses peptidyl-tRNA hydrolysis promoted by eRF1, revealing principles of eukaryotic translation termination and laying the foundation for new therapeutic strategies.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Structural understanding of non-nucleoside inhibition in an elongating herpesvirus polymerase

All herpesviruses encode a conserved DNA polymerase that is required for viral genome replication and serves as an important therapeutic target. Currently available herpesvirus therapies include nucleoside and non-nucleoside inhibitors (NNI) that target the DNA-bound state of herpesvirus polymerase and block replication. Here we report the ternary complex crystal structure of Herpes Simplex Virus 1 DNA polymerase bound to DNA and a 4-oxo-dihydroquinoline NNI, PNU-183792 (PNU), at 3.5 Å resolution. PNU bound at the polymerase active site, displacing the template strand and inducing a conformational shift of the fingers domain into an open state. These results demonstrate that PNU inhibits replication by blocking association of dNTP and stalling the enzyme in a catalytically incompetent conformation, ultimately acting as a nucleotide competing inhibitor (NCI). Sequence conservation of the NCI binding pocket further explains broad-spectrum activity while a direct interaction between PNU and residue V823 rationalizes why mutations at this position result in loss of inhibition.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Trans-crustal structural control of CO 2 -rich extensional magmatic systems revealed at Mount Erebus Antarctica

Erebus volcano, Antarctica, with its persistent phonolite lava lake, is a classic example of an evolved, CO 2 -rich rift volcano. Seismic studies provide limited images of the magmatic system. Here we show using magnetotelluric data that a steep, melt-related conduit of low electrical resistivity originating in the upper mantle undergoes pronounced lateral re-orientation in the deep crust before reaching shallower magmatic storage and the summit lava lake. The lateral turn represents a structural fault-valve controlling episodic flow of magma and CO 2 vapour, which replenish and heat the high level phonolite differentiation zone. This magmatic valve lies within an inferred, east-west structural trend forming part of an accommodation zone across the southern termination of the Terror Rift, providing a dilatant magma pathway. Unlike H 2 O-rich subduction arc volcanoes, CO 2 -dominated Erebus geophysically shows continuous magmatic structure to shallow crustal depths of < 1 km, as the melt does not experience decompression-related volatile supersaturation and viscous stalling.

58 GEOSCIENCES↗
DOE OSTI2025

Molecular model of TFIIH recruitment to the transcription-coupled repair machinery

Transcription-coupled repair (TCR) is a vital nucleotide excision repair sub-pathway that removes DNA lesions from actively transcribed DNA strands. Binding of CSB to lesion-stalled RNA Polymerase II (Pol II) initiates TCR by triggering the recruitment of downstream repair factors. Yet it remains unknown how transcription factor IIH (TFIIH) is recruited to the intact TCR complex. Combining existing structural data with AlphaFold predictions, we build an integrative model of the initial TFIIH-bound TCR complex. We show how TFIIH can be first recruited in an open repair-inhibited conformation, which requires subsequent CAK module removal and conformational closure to process damaged DNA. In our model, CSB, CSA, UVSSA, elongation factor 1 (ELOF1), and specific Pol II and UVSSA-bound ubiquitin moieties come together to provide interaction interfaces needed for TFIIH recruitment. STK19 acts as a linchpin of the assembly, orienting the incoming TFIIH and bridging Pol II to core TCR factors and DNA. Molecular simulations of the TCR-associated CRL4CSA ubiquitin ligase complex unveil the interplay of segmental DDB1 flexibility, continuous Cullin4A flexibility, and the key role of ELOF1 for Pol II ubiquitination that enables TCR. Collectively, these findings elucidate the coordinated assembly of repair proteins in early TCR.

Paul, Tanmoy↗
DOE OSTI2025

Structural insights into transcriptional regulation by the helicase RECQL5

Abstract Transcription poses a major challenge for genome stability. The RECQL5 helicase helps safeguard genome integrity and is the only member of the human RecQ helicase family that directly binds to RNA polymerase II (Pol II) and affects its progression. While RECQL5 mitigates transcription stress in cells, the molecular mechanism underlying this phenomenon is unclear. Here, we use cryo-electron microscopy to determine the structures of stalled human Pol II elongation complexes (ECs) bound to RECQL5. Our structures reveal the molecular interactions stabilizing RECQL5 binding to the Pol II EC and highlight its role as a transcriptional roadblock. Additionally, we find that, in its nucleotide-free state, RECQL5 twists the downstream DNA in the EC and, upon nucleotide binding, undergoes a conformational change that allosterically induces Pol II toward a post-translocation state. We propose that this mechanism may help restart Pol II elongation and, therefore, contribute to reducing transcription stress.

Biochemistry & Molecular Biology↗
DOE OSTI2021

Targeted disruption of pi–pi stacking in Malaysian banana lectin reduces mitogenicity while preserving antiviral activity

Lectins, carbohydrate-binding proteins, have been regarded as potential antiviral agents, as some can bind glycans on viral surface glycoproteins and inactivate their functions. However, clinical development of lectins has been stalled by the mitogenicity of many of these proteins, which is the ability to stimulate deleterious proliferation, especially of immune cells. We previously demonstrated that the mitogenic and antiviral activities of a lectin (banana lectin, BanLec) can be separated via a single amino acid mutation, histidine to threonine at position 84 (H84T), within the third Greek key. The resulting lectin, H84T BanLec, is virtually non-mitogenic but retains antiviral activity. Decreased mitogenicity was associated with disruption of pi–pi stacking between two aromatic amino acids. To examine whether we could provide further proof-of-principle of the ability to separate these two distinct lectin functions, we identified another lectin, Malaysian banana lectin (Malay BanLec), with similar structural features as BanLec, including pi–pi stacking, but with only 63% amino acid identity, and showed that it is both mitogenic and potently antiviral. We then engineered an F84T mutation expected to disrupt pi–pi stacking, analogous to H84T. As predicted, F84T Malay BanLec (F84T) was less mitogenic than wild type. However, F84T maintained strong antiviral activity and inhibited replication of HIV, Ebola, and other viruses. The F84T mutation disrupted pi–pi stacking without disrupting the overall lectin structure. These findings show that pi–pi stacking in the third Greek key is a conserved mitogenic motif in these two jacalin-related lectins BanLec and Malay BanLec, and further highlight the potential to rationally engineer antiviral lectins for therapeutic purposes.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Synthetic antibacterial minerals: harnessing a natural geochemical reaction to combat antibiotic resistance

The overuse of antibiotics in clinical and livestock settings is accelerating the selection of multidrug resistant bacterial pathogens. Antibiotic resistant bacteria result in increased mortality and financial strain on the health care and livestock industry. The development of new antibiotics has stalled, and novel strategies are needed as we enter the age of antibiotic resistance. Certain naturally occurring clays have been shown to have antimicrobial properties and kill antibiotic resistant bacteria. Harnessing the activity of compounds within these clays that harbor antibiotic properties offers new therapeutic opportunities for fighting the potentially devastating effects of the post antibiotic era. However, natural samples are highly heterogenous and exhibit variable antibacterial effectiveness, therefore synthesizing minerals of high purity with reproducible antibacterial activity is needed. Here we describe for the first time synthetic smectite clay minerals and Fe-sulfide microspheres that reproduce the geochemical antibacterial properties observed in natural occurring clays. We show that these mineral formulations are effective at killing the ESKAPE pathogens ( Enterococcus sp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter sp., Pseudomonas aeruginosa and Enterobacter sp.) by maintaining Fe 2+ solubility and reactive oxygen species (ROS) production while buffering solution pH, unlike the application of metals alone. Our results represent the first step in utilizing a geochemical process to treat antibiotic resistant topical or gastrointestinal infections in the age of antibiotic resistance.

58 GEOSCIENCES↗