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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Structure based modification of Bluetongue virus helicase protein VP6 to produce a viable VP6-truncated BTV

Highlights: • NMR analysis on BTV VP6 reveals two large loop regions. • The loss of a loop (aa 34–130) does not affect the overall fold of the protein. • A region of VP6 (aa 34–92) is not required for BTV replication. • A region of VP6 (aa 93–130) plays an essential role in the virus replication. - Abstract: Bluetongue virus core protein VP6 is an ATP hydrolysis dependent RNA helicase. However, despite much study, the precise role of VP6 within the viral capsid and its structure remain unclear. To investigate the requirement of VP6 in BTV replication, we initiated a structural and biological study. Multinuclear nuclear magnetic resonance spectra were assigned on his-tagged full-length VP6 (329 amino acid residues) as well as several truncated VP6 variants. The analysis revealed a large structured domain with two large loop regions that exhibit significant conformational exchange. One of the loops (amino acid position 34–130) could be removed without affecting the overall fold of the protein. Moreover, using a BTV reverse genetics system, it was possible to demonstrate that the VP6-truncated BTV was viable in BHK cells in the absence of any helper VP6 protein, suggesting that a large portion of this loop region is not absolutely required for BTV replication.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Early life ethanol exposure causes long-lasting disturbances in rat mesenchymal stem cells via epigenetic modifications

Highlights: • Ethanol exposure alters proliferation and differentiation of MSCs. • Ethanol exposure suppresses osteogenesis and adipogenesis of MSCs. • H3K27me3-associated genes/pathways are affected in ethanol-exposed MSCs. • Expression of lineage-specific genes is dysregulated in ethanol-exposed MSCs. - Abstract: Fetal alcohol syndrome (FAS) is a birth defect due to maternal alcohol consumption during pregnancy. Because mesenchymal stem cells (MSCs) are the main somatic stem cells in adults and may contribute to tissue homeostasis and repair in adulthood, we investigated whether early life ethanol exposure affects MSCs and contributes to the propensity for disease onset in later life. Using a rodent model of FAS, we found that ethanol exposure (5.25 g/kg/day) from postnatal days 4 to 9 in rat pups (mimic of human third trimester) caused long-term anomalies in bone marrow-derived MSCs. MSCs isolated from ethanol-exposed animals were prone to neural induction but resistant to osteogenic and adipogenic inductions compared to their age-matched controls. The altered differentiation may contribute to the severe trabecular bone loss seen in ethanol-exposed animals at 3 months of age as well as overt growth retardation. Expression of alkaline phosphatase, osteocalcin, aP2, and PPARγ were substantially inhibited, but BDNF was up-regulated in MSCs isolated from ethanol-exposed 3 month-old animals. Several signaling pathways were distorted in ethanol-exposed MSCs via altered trimethylation at histone 3 lysine 27. These results demonstrate that early life ethanol exposure can have long-term impacts in rat MSCs by both genetic and epigenetic mechanisms.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

The small molecule 2-phenylethynesulfonamide induces covalent modification of p53

p53 is a tumor suppressor protein which is either lost or inactivated in a large majority of tumors. The small molecule 2-phenylethynesulfonamide (PES) was originally identified as the inhibitor of p53 effects on the mitochondrial death pathway. In this report we demonstrate that p53 protein from PES-treated cells was detected in reduced mobility bands between molecular weights 95–220 kDa. Resolution of p53 aggregates on urea gel was unable to reduce the high molecular weight p53 aggregates, which were shown to be primarily located in the nucleus. Therefore, our data suggest that PES exerts its effects through covalent cross-linking and nuclear retention of p53. - Highlights: • p53 protein is in high molecular weight complexes in the nucleus of PES-treated cells. • PES is a drug that inhibits pro-apoptotic p53 action at the mitochondria. • We propose that PES action involves cross-linking and nuclear retention of p53.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

GnT-V promotes chemosensitivity to gemcitabine in bladder cancer cells through β1,6 GlcNAc branch modification of human equilibrative nucleoside transporter 1

Human equilibrative nucleoside transporter 1 (hENT1) transports nucleoside analogue drugs across cellular membranes and is necessary for the uptake of many anti-tumor drugs. Gemcitabine is a frontline agent of chemotherapy for bladder cancer despite its limited efficacy due to chemoresistance, there is an acute need to decipher mechanisms underlying chemosensitivity to gemcitabinein in bladder cancer cells. Here we report a novel role for N-acetylglucosaminyltransferase V (GnT-V) in gemcitabine chemosensitivity. In this study, we found that GnT-V expression affected cell death rate to gemcitabine in different bladder cancer cells and down-regulation of GnT-V inhibited the gemcitabine sensitivity with time and dose dependent way in T24 cells. Moreover, mechanistic investigations showed that silencing GnT-V caused dramatic decrease of β1,6 GlcNAc structure on hENT1 leading to apparently decreased accumulation of hENT1 at plasma membrane, and therefore result in less uptake of gemcitabine in T24/shRNA cells. Together, our present study indicated that GnT-V enhances gemcitabine chemosensitivity via modulation of hENT1 N-glycosylation and transport activity in T24 cells, providing new insights into how N-glycosylation drives antitumor drug sensitivity during chemotherapy for patients with cancer.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

The role of precursor modification on the production of graphite foam

A high-conductivity graphite foam developed at Oak Ridge National Laboratory (ORNL) owes its unique thermal properties to the highly aligned graphitic structure along the cell walls. The material exhibits a peak in thermal conductivity at temperatures like that of highly ordered natural graphite, indicating the foam has an extremely graphitic nature. This paper explores the manufacturing process to identify processing conditions that most affect the properties of the foam, such that the production of the foam can be easily tailored to different applications. This paper examines processing conditions from the precursor preparation as well as additives to the precursor, such as graphene, on the resulting foam structure and thermal properties. It was found that heat treating the precursor mesophase to increase melt viscosity and decrease off gassing during foaming decreased the thermal conductivity of the final foams, however, it resulted in smaller pores. Additions of graphene platelets decreases the thermal conductivity of the foams while simultaneously decreasing the pore size as well. In conclusion, these tradeoffs are evident and present the manufacturer options to tailor the foams.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The structural modification and magnetism of many-layer epitaxial graphene implanted with low-energy light ions

Modifying the properties of graphene has gained wide interest for a plethora of potential applications, including spintronics. One approach has demonstrated that proton irradiation can induce ferromagnetism in graphene as well as in graphite. However, little is known about how the protons interact with graphene, the mechanism that creates the ferromagnetism, or whether the protons remain in the graphene. Here we report an investigation, broadly relevant to graphitic carbon, using low-energy (360–2000 eV) ions of hydrogen, deuterium, and helium implanted into multilayer epitaxial graphene. Complementary x-ray and neutron reflectivity demonstrate that essentially all of the implanted hydrogen remains chemisorbed in graphene. In situ x-ray diffraction reveals significantly different rates of interlayer expansion of the multilayer graphene. Analysis of these data demonstrates that the interlayer expansion arises entirely from the interstitials created by the ions and not from hydrogen that remains in the graphene. The results also establish a quantitative measure of the layer expansion due to carbon interstitials. Magnetometry and x-ray diffraction studies show that the magnetic moment relates to the amount of interstitial carbon rather than the amount of hydrogen, demonstrating that the induced room-temperature ferromagnetism arises directly from the disrupted bonding of the carbon lattice.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nano-modification to improve the ductility of cementitious composites

Effect of nano-sized mineral additions on ductility of engineered cementitious composites (ECC) containing high volumes of fly ash was investigated at different hydration degrees. Various properties of ECC mixtures with different mineral additions were compared in terms of microstructural properties of matrix, fiber-matrix interface, and fiber surface to assess improvements in ductility. Microstructural characterization was made by measuring pore size distributions through mercury intrusion porosimetry (MIP). Hydration characteristics were assessed using thermogravimetric analysis/differential thermal analysis (TGA/DTA), and fiber-matrix interface and fiber surface characteristics were assessed using scanning electron microscopy (SEM) through a period of 90 days. Moreover, compressive and flexural strength developments were monitored for the same period. Test results confirmed that mineral additions could significantly improve both flexural strength and ductility of ECC, especially at early ages. Cheaper Nano-CaCO{sub 3} was more effective compared to nano-silica. However, the crystal structure of CaCO{sub 3} played a very important role in the range of expected improvements.

36 MATERIALS SCIENCE↗