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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Ionic Liquid‐Driven Modulation of DNA Brush Morphology on Nanoparticle Surfaces

Here, the morphology of DNA is strongly influenced by its surrounding environment, including factors such as pH, salt type and valency, and the presence of polymers. Inorganic salts are known to reduce the DNA chain length through mechanisms like electrostatic screening and ion bridging. In contrast, ionic liquids, a new class of organic salts, have previously been found to increase the DNA chain length, indicating a distinct mode of interaction between the ionic liquid and DNA chains. This study utilizes self-assembled DNA-AuNPs as a model system to examine changes in the DNA chain morphology and the nanoscale interaction mechanisms in an ionic liquid environment. The DNA chain lengths are measured in solution using X-ray scattering measurements at varying concentrations of two imidazolium ([$BMIM$] acetate and [$EMIM$] acetate) based ionic liquids. Additionally, Molecular Dynamics (MD) simulations are performed mimicking the experimental system. Our results suggest an interplay of electrostatic and groove-binding interactions governing the DNA chain morphology, which depends on IL concentration and the composition of the DNA chains. It has been found that for DNA chains with majority ssDNA, electrostatic interaction dominate, however with increasing composition of double strands, the DNA chains exhibit compaction due to a non-electrostatic hydrophobic groove-binding mechanism.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Quantitative trait locus mapping combined with variant and transcriptome analyses identifies a cluster of gene candidates underlying the variation in leaf wax between upland and lowland switchgrass ecotypes

Switchgrass (Panicum virgatum L.) is a promising warm-season candidate energy crop. It occurs in two ecotypes, upland and lowland, which vary in a number of phenotypic traits, including leaf glaucousness. To initiate trait mapping, two F 2 mapping populations were developed by crossing two different F 1 sibs derived from a cross between the tetraploid lowland genotype AP13 and the tetraploid upland genotype VS16, and high-density linkage maps were generated. Quantitative trait locus (QTL) analyses of visually scored leaf glaucousness and of hydrophobicity of the abaxial leaf surface measured using a drop shape analyzer identified highly significant colocalizing QTL on chromosome 7K (Chr07K). Using a multipronged approach, we identified a cluster of genes including Pavir.7KG077009, which encodes a Type III polyketide synthase-like protein, and Pavir.7KG013754 and Pavir.7KG030500, two highly similar genes that encode putative acyl-acyl carrier protein (ACP) thioesterases, as strong candidates underlying the QTL. The lack of homoeologs for any of the three genes on Chr07N, the relatively low level of identity with other switchgrass KCS proteins and thioesterases, as well as the organization of the surrounding region suggest that Pavir.7KG077009 and Pavir.7KG013754/Pavir.7KG030500 were duplicated into a fast-evolving chromosome region, which led to their neofunctionalization. Furthermore, sequence analyses showed all three genes to be absent in the two upland compared to the two lowland accessions analyzed. This study provides an example of and practical guide for trait mapping and candidate gene identification in a complex genetic system by combining QTL mapping, transcriptomics and variant analysis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Natively oxidized amino acid residues in the spinach PS I-LHC I supercomplex

Reactive oxygen species (ROS) production is an unavoidable byproduct of electron transport under aerobic conditions. Photosystem II (PS II), the cytochrome b 6 /ƒ complex and Photosystem I (PS I) are all demonstrated sources of ROS. It has been proposed that PS I produces substantial levels of a variety of ROS including O$_{2}^{·-}$, 1 O 2 , H 2 O 2 and, possibly, ∙OH, however, the site(s) of ROS production within PS I has been the subject of significant debate. We hypothesize that amino acid residues close to the sites of ROS generation will be more susceptible to oxidative modification than distant residues. In this study, we have identified oxidized amino acid residues in spinach PS I which was isolated from field-grown spinach. The modified residues were identified by high-resolution tandem mass spectrometry. As expected, many of the modified residues lie on the surface of the complex. However, a well-defined group of oxidized residues, both buried and surface-exposed, lead from the chl a’ of P 700 to the surface of PS I. These residues (PsaB: 609 F, 611 E, 617 M, 619 W, 620 L, and PsaF: 139 L, 142 A, 143 D) may identify a preferred route for ROS, probably 1 O 2 , to egress the complex from the vicinity of P 700 . Additionally, two buried residues located in close proximity to A1B (PsaB: 712 H and 714 S) were modified, which may be consistent with A 1B being a source of O$_{2}^{·-}$. Surprisingly, no oxidatively modified residues were identified in close proximity to the 4Fe-FS clusters F X , F A or F B . These cofactors had been identified as a principal targets for ROS damage in the photosystem. Finally, a large number of residues located in the hydrophobic cores of Lhca1-Lhca4 are oxidatively modified. These appear to be the result of 1 O 2 production by the distal antennae for the photosystem.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Hydrogen Bonding Stiffens Peptide Amphiphile Supramolecular Filaments by Aza-Glycine Residues

Peptide amphiphiles (PAs) are a class of molecules comprised of short amino acid sequences conjugated to hydrophobic moieties that may exhibit self-assembly in water into supramolecular structures. Here, we investigate here how mechanical properties of hydrogels formed by PA supramolecular nanofibers are affected by hydrogen bond densities within their internal structure by substituting glycine for aza-glycine (azaG) residues. We found that increasing the number of PA molecules that contain azaG up to 5 mol% in PA supramolecular nanofibers increases their persistence length fivefold and decreases their diffusion coefficients as measured by fluorescence recovery after photobleaching. When these PAs are used to create hydrogels, their bulk storage modulus (G') was found to increase as azaG PA content in the supramolecular assemblies increases up to a value of 10 mol% and beyond this value a decrease was observed, likely due to diminished levels of nanofiber entanglement in the hydrogels as a direct result of increased supramolecular rigidity. Interestingly, we found that the bioactivity of the scaffolds toward dopaminergic neurons derived from induced pluripotent stem cells can be enhanced directly by persistence length independently of storage modulus. We hypothesize that this is due to interactions between the cells and the extracellular environment across different size scales: from filopodia adhering to individual nanofiber bundles to cell adhesion sites that interact with the hydrogel as a bulk substrate. Fine tuning of hydrogen bond density in self-assembling peptide biomaterials such as PAs provides an approach to control nanoscale stiffness as part of an overall strategy to optimize bioactivity in these supramolecular systems. supramolecular biomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Optimization of peptide amphiphile-lipid raft interaction by changing peptide amphiphile lipophilicity

Various peptide amphiphile (PA) molecules have been developed to promote bone regeneration. Previously we discovered that a peptide amphiphile with a palmitic acid tail (C 16 ) attenuates the signaling threshold of leucine-rich amelogenin peptide (LRAP)-mediated Wnt activation by increasing membrane lipid raft mobility. In the current study, we found that treatment of murine ST2 cells with an inhibitor (Nystatin) or Caveolin-1-specific siRNA abolishes the effect of C 16 PA, indicating that Caveolin-mediated endocytosis is required. Here, to determine whether hydrophobicity of the PA tail plays a role in its signaling effect, we modified the length of the tail (C 12 , C 16 and C 22 ) or composition (cholesterol). While shortening the tail (C 12 ) decreased the signaling effect, lengthening the tail (C 22 ) had no prominent effect. On the other hand, the cholesterol PA displayed a similar function as the C 16 PA at the same concentration of 0.001% w/v. Interestingly, a higher concentration of C 16 PA (0.005%) is cytotoxic while cholesterol PA at the higher concentration (0.005%) is well-tolerated by cells. Use of the cholesterol PA at 0.005% enabled a further reduction of the signaling threshold of LRAP to 0.20 nM, compared to 0.25 nM at 0.001%. Caveolin-mediated endocytosis is also required for cholesterol PA, as evidenced by Caveolin-1 siRNA knockdown experiments. We further demonstrated that the noted effects of cholesterol PA are also observed in human bone marrow mesenchymal stem cells (BMMSCs). Taken together, these results indicate that the cholesterol PA modulates lipid raft/caveolar dynamics, thereby increasing receptor sensitivity for activation of canonical Wnt signaling.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Macroscale Control of Reactivity using 3D Printed Materials with Intrinsic Catalytic Properties

The morphology of heterogeneous catalysts can impact their performance. However, standard manufacturing methods like extrusion or pelleting offer little options for tailoring catalyst shape. Herein, stereolithographic 3D printing is used to produce catalysts with controlled topologies to enhance their performance. A series of magnetic stir-bar compartments (SBC) were 3D printed and tested as catalysts for sucrose hydrolysis. The SBC were printed using acrylic acid (AA) and 1,6-hexanediol diacrylate (HDDA) as acid sites and hydrophobic crosslinking domains, respectively. Variations in the number and tilt direction of the SBC blades produced significant changes in their apparent catalytic activities. These changes resulted from differences in the fraction of active surface effectively interacting with the reactants in solution, as revealed by computational fluid dynamics simulations. Moreover, varying HDDA:AA ratios in SBC regulated reactant-surface interactions to control catalytic activity. Overall, 3D printing catalysts enables quick performance optimization by simultaneously controlling macroscopic structure and molecular composition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Large-area nanostructured surfaces with tunable zeta potentials

Through a refined fabrication protocol based on block-copolymer self-assembly we synthesize nanostructured surfaces with conical nanopillars of different height (60, 120, and 200 nm) in hexagonal arrays with uniform spacing (~50 nm) over large areas (>cm 2 ). While the nanostructured surfaces fabricated on silicon substrates display superhydrophilic behavior, superhydrophobic properties are attained by coating with octadecyltrichlorosilane (OTS). Negative zeta potentials for all the studied surfaces are reported by electrokinetic flow measurements with aqueous KCl solutions at different concentrations (1 and 10 mM) and pH values between 4 and 8. While the surface nanostructure reduces the zeta potential magnitude, the hydrophobic OTS coating enhances it. Experimental results can be accounted for by a site-dissociation model for the surface charge density. The reported wetting properties and zeta potential tunability makes the studied surfaces particularly relevant for applications such as energy conversion and storage, membrane-based water treatment and molecular separation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Tailoring biogenic straw insulation from additive manufacturing

In the pursuit of carbon-storing materials that could help accomplish high levels of building sustainability, wheat straw has emerged as a promising alternative to fossil fuel-based building materials. Straw is 100% biodegradable and abundant agricultural waste used in the construction 400 years ago, and it has been reported to have the lowest embodied carbon when measured against other typical insulating materials. Here, in this study, we report additive manufacturing of carbon-sequestration insulation panel materials by upcycling cellulose fibrils from wheat straw. Cellulose obtained from alkaline and 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation shows thermal conductivity of 0.036 W m -1 K -1 , alongside elastic and flexural modulus of 900 MPa and 502 MPa, respectively. In addition, an in-situ hydrophobic treatment in the cellulose-based insulation panels is achieved with an average water contact angle of 133.7° Furthermore, the extrusion-based additive manufacturing of a 3D-printable ink obtained by mixing the cellulose and silica aerogel precursor is accomplished, with the printed material exhibiting structural integrity, thus showing great potential towards the development of state-of-the-art, sustainable materials for carbon-sequestration building applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Flame-retardant cellulose-aerogel composite from agriculture waste for building insulation

Bio-based thermal insulation materials are in high demand due to their availability, reproducibility, and carbon-sequestration nature. However, high flammability, moisture condensation, and high thermal conductivity of biogenic material are major concerns for sustainable building applications. In this study, we report the fire-retardant cellulose aerogel insulation nanocomposites derived from wheat straw and silica aerogel, in which sodium bicarbonate improves its fire retardancy. We combined blended straw fibers and hammermilled straw fibers to create a structural hierarchy composite. The blended straw, with its longer and thicker size, served as reinforcement, while the hammermilled straw fibers acted as filler. This hierarchical structure was further integrated with aerogel for applications in green buildings. The as-prepared materials show a low thermal conductivity of 24.1 mW/m.K, high flexural modulus of 736 MPa, hydrophobicity with a water contact angle of 110.42°, and excellent fire retardancy. Altogether, this work provides an effective method for the synthesis of fire-retardant biogenic thermal insulation materials and shows a promising way for next-generation bio-based insulation materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Carbon nanotube coated metal mesh: Bridging nanoscale and macroscale

A novel hybrid structure has been developed by growing carbon nanotubes (CNTs) on a metal mesh that functions as a literally unlimitedly extendable backbone. This hybrid material structure provides a new approach of extending CNTs’ advantageous properties such as ultrahigh thermal and electrical conductivities, high sensitivity to gases, and distinctive wettability for different liquids with chemical inertness to macroscale—otherwise available only in nano- and microscales. In this feasibility work, CNTs were grown on a Type 316 stainless steel (SS) mesh by self-catalytical chemical vapor deposition (CVD) without the need of an externally added catalyst or catalyst support. For the radially aligned and entangled CNT forest on the SS mesh, the average CNT diameter is around 50 nm, while the length varies from 20 to 25 µm. High-resolution transmission electron microscopy analysis revealed the multiwall structure of the CNTs with >30 rolled-up graphitic sheets. Raman spectra of the CNTs showed a dominant G band, indicating a well-ordered graphitic nanostructure. Being highly hydrophobic with a water contact angle of ∼145° and oleophilic, the CNT-coated SS mesh could be used in fluid separation and organic contaminant removal from water. Moreover, CNTs are recognized for their exceptional thermal conductivity and the CNT-coated mesh offers a supportive structure with directly connected CNTs for efficient heat transfer. Proof of concept has been achieved for the CNT-coated mesh’s potentials as a liquid filter and an thermal interface material (TIM). Specifically, the CNT-coated mesh demonstrated the capability of capturing water from a water-organic mixture with a 100 % efficiency while allowing organic liquids to pass through the filter. Furthermore, when used as a TIM, the CNT-coated mesh reduced the interfacial thermal impedance by >30 %.

Carbon nanotubes (CNTS)↗
DOE OSTI2025

Visualization of in-situ chemical flow through sand using neutron radiography

Chemical movement through soil is an important process in agriculture and ecology. Observing the spatial and temporal dynamics of these processes using conventional chemical ecology methods requires techniques that are destructive and/or lack resolution. Neutron radiography has the capability to allow chemical motion through sand/soil to be tracked with high spatial and temporal resolution, and we show that it allows for the motion of hydrophobic and hydrophilic chemicals to be distinguished. This technique can have an important impact on introducing neutron radiography to a wider community and into our understanding of chemical communication dynamics between plants and movement of applied chemicals in agricultural soils.

MORRIS, KATHRYN [Xavier University]↗
DOE OSTI2021

Traction-separation response of bilayer graphene interfaces: The role of an intercalated single atomic layer of water molecules and hydroxyl groups

Molecular dynamics simulations of the normal and shear traction-separation response of dry and wet bilayer graphene interfaces were performed. The influence of a single, atomic layer of water molecules sandwiched between graphene layers and hydroxyl functionalization on one or both layers were investigated. Hydroxyl groups provided a shielding effect during normal separation while favoring stick-slip friction under sliding conditions. The single, atomic layer of water molecules confined between hydrophilic and asymmetric hydrophobic/hydrophilic surfaces was found to ease sliding friction. The mechanisms arose from the balance between the attractive and repulsive graphene/water interactions through bridges of single water molecules between the two surfaces and the structure of the water monolayer under confinement for which an out-of-plane water/water hydrogen bond network could not be developed. The single, atomic layer of water molecules reduced the sliding friction the most when both surfaces were hydrophilic and lowered the sliding friction of the asymmetric hydrophobic/hydrophilic interfaces to that when both surfaces were hydrophobic. An optimal hydroxyl surface coverage of less than 10% may exist for efficient water lubrication, with diminishing effect with increasing number of hydroxyl groups. Finally, the findings offer a design strategy for assembling bilayer graphene interfaces with tailored friction and sliding contact properties.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Twin-screw granulation: Mechanistic understanding of the effect of material properties on key granule quality attributes through the analysis of mixing dynamics and granulation rate mechanisms

This study focuses on understanding the effect of material properties on granule quality attributes through the analysis of mixing dynamics and granulation rate mechanisms. Powder wettability, binder viscosity, and liquid-to-solid (L/S) ratio were the factors that were investigated in this study. Further, the mixing occurring inside the twin-screw granulator (TSG) was quantitatively assessed by obtaining the axial dispersion coefficient from the experimentally measured residence time distribution (RTD) curves. It was observed that the quality of the nuclei fed to the kneading zone significantly affected the mixing dynamics. The quality of nuclei was governed by nucleation kinetics, which in turn was principally affected by the liquid saturation of the nuclei and the ratio of drop penetration time and encounter time, which in turn were affected by the L/S ratio and binder viscosity respectively. The hydrophobicity of the blend mainly affected the extent of nucleation. The type of nuclei entering the kneading zone and mixing dynamics in the TSG also determined whether the granulation growth mechanism was “layering-dominant” or “viscous-dominant”. It was also shown that the resultant granule quality attributes were a reflection of the growth mechanisms. Ultimately, a mechanistic link between material properties, mixing dynamics, granulation rate mechanisms, and granule quality attributes was established.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quantifying biofilm propagation on chemically modified surfaces

Conditions affecting biofilm formation differ among bacterial species and this presents a challenge to studying biofilms in the lab. This work leverages functionalized silanes to control surface chemistry in the study of early biofilm propagation, quantified with a semi-automated image processing algorithm. These methods support the study of Pantoea sp. YR343, a gram-negative bacterium isolated from the poplar rhizosphere. We found that Pantoea sp. YR343 does not readily attach to hydrophilic surfaces but will form biofilms with a “honeycomb” morphology on hydrophobic surfaces. Our image processing algorithm described here quantified the evolution of the honeycomb morphology over time, and found the propagation to display a logarithmic behavior. This methodology was repeated with a flagella-deficient fliR mutant of Pantoea sp. YR343 which resulted in reduced surface attachment. Quantifiable differences between Pantoea WT and ΔfliR biofilm morphologies were captured by the image processing algorithm, further demonstrating the insight gained from these methods.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Nanoparticle-mediated antagonism of sustained endosomal signaling of the calcitonin receptor-like receptor provides enhanced and persistent relief of oral cancer pain

By improving the delivery and tumor retention of chemotherapeutics, nanomedicines hold potential for cancer treatment. The usefulness of nanoparticle (NP)-encapsulated analgesics for the cancer pain treatment is comparatively unexplored. We investigated whether NPs encapsulating olcegepant (OCP), an antagonist of the calcitonin receptor-like receptor (CLR) for the calcitonin gene-related peptide (CGRP), effectively relieved oral cancer pain in mice. Because persistent endosomal CLR signaling in Schwann cells mediates craniofacial pain, we reasoned that the predisposition of NPs to accumulate in endosomes could be leveraged to effectively relieve oral cancer pain. By expressing biosensors for activated CLR, Gα proteins and β-arrestins in HEK293T and Schwann cells, we found that CGRP activates CLR signaling first at the plasma membrane and then in early, late and recycling endosomes and the cis- and trans-Golgi apparatus. We synthesized biocompatible NPs encapsulating OCP and fluorophores by integrating hydrophobic ion pairing nanoformulation with Flash NanoPrecipitation. NPs slowly released OCP and accumulated in early endosomes, leading to sustained inhibition of endosomal CLR signaling in HEK293T and Schwann cells. Oral cancers were established in mice, which led to heightened pain-like responses. After intra-tumoral injection, NPs were retained in tumors for at least one week. OCP-loaded NPs almost completely reversed allodynia and hyperalgesia for a prolonged period, whereas unencapsulated OCP had small and transient effects. The NP accumulation in endosomal sites of pain signaling, the sustained release of antagonist, and the retention of NPs in tumors explain their beneficial actions. Thus, NP-encapsulation holds promise for the relief of painful cancers that are inadequately treated by opioids.

Calcitonin gene-related peptide↗
DOE OSTI2022

Revealing the mechanism of surfactant-promoted enzymatic hydrolysis of dilute acid pretreated bamboo

Here, to improve the enzymatic digestibility of dilute acid pretreated bamboo residue (DABR), surfactants including PEG 4000 and Tween 80 were added to prevent the non-productive adsorption between residual lignin and enzyme. At the optimal loadings (e.g., 0.2 and 0.3 g surfactant/g lignin), the enzymatic digestibility of DABR improved from 29.4% to 64.6% and 61.6% for PEG 4000 and Tween 80, respectively. Furthermore, the promoting mechanism of these surfactants on enzymatic hydrolysis was investigated by real-time surface plasmon resonance (SPR) and fluorescence spectroscopy. Results from SPR analysis showed that Tween 80 outperformed PEG 4000 in terms of dissociating the irreversible cellulase adsorption onto lignin. Fluorescence quenching mechanism revealed that PEG 4000 and Tween 80 intervened the interaction between lignin and cellulase by hydrogen bonds/Van der Waals and hydrophobic action, respectively. This work provided an in-depth understanding of the mechanisms of PEG 4000 and Tween 80 on enhancing the enzymatic hydrolysis efficiency.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Locking out water at 100°C

We report that thermophilic proteins, present in organisms that live at high temperatures, denature at much higher temperatures compared with their mesophilic counterparts. How these proteins stand the heat has long been researched and is particularly interesting because homologous pairs of thermophilic and mesophilic proteins show a high degree of structural and sequence similarity. In early studies of thermophilic proteins, the proportion of solvent-accessible charged residues was found to be increased at the expense of polar residues. Further analyses confirmed this and also noted strengthening of hydrophobic cores by branched apolar residues. At the same time, whether thermophilic proteins actually need to be more or less flexible than their mesophilic counterparts and the potential usefulness of surface loop deletion has been debated.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Generative $β$-hairpin design using a residue-based physicochemical property landscape

De novo peptide design is a new frontier that has broad application potential in the biological and biomedical fields. Most existing models for de novo peptide design are largely based on sequence homology that can be restricted based on evolutionarily derived protein sequences and lack the physicochemical context essential in protein folding. Generative machine learning for de novo peptide design is a promising way to synthesize theoretical data that are based on, but unique from, the observable universe. In this study, we created and tested a custom peptide generative adversarial network intended to design peptide sequences that can fold into the -hairpin secondary structure. This deep neural network model is designed to establish a preliminary foundation of the generative approach based on physicochemical and conformational properties of 20 canonical amino acids, for example, hydrophobicity and residue volume, using extant structure-specific sequence data from the PDB. The beta generative adversarial network model robustly distinguishes secondary structures of hairpin from α helix and intrinsically disordered peptides with an accuracy of up to 96% and generates artificial -hairpin peptide sequences with minimum sequence identities around 31% and 50% when compared against the current NCBI PDB and nonredundant databases, respectively. These results highlight the potential of generative models specifically anchored by physicochemical and conformational property features of amino acids to expand the sequence-to-structure landscape of proteins beyond evolutionary limits.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗