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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Structural mechanisms of TRPV6 inhibition by ruthenium red and econazole

TRPV6 is a calcium-selective ion channel implicated in epithelial Ca 2+ uptake. TRPV6 inhibitors are needed for the treatment of a broad range of diseases associated with disturbed calcium homeostasis, including cancers. Here we combine cryo-EM, calcium imaging, and mutagenesis to explore molecular bases of human TRPV6 inhibition by the antifungal drug econazole and the universal ion channel blocker ruthenium red (RR). Econazole binds to an allosteric site at the channel’s periphery, where it replaces a lipid. In contrast, RR inhibits TRPV6 by binding in the middle of the ion channel’s selectivity filter and plugging its pore like a bottle cork. Despite different binding site locations, both inhibitors induce similar conformational changes in the channel resulting in closure of the gate formed by S6 helices bundle crossing. The uncovered molecular mechanisms of TRPV6 inhibition can guide the design of a new generation of clinically useful inhibitors.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2012

Structural mechanism of Staphylococcus aureus Hfq binding to an RNA A-tract

Hfq is a post-transcriptional regulator that plays a key role in bacterial gene expression by binding AU-rich sequences and A-tracts to facilitate the annealing of sRNAs to target mRNAs and to affect RNA stability. To understand how Hfq from the Gram-positive bacterium Staphylococcus aureus (Sa) binds A-tract RNA, we determined the crystal structure of an Sa Hfq–adenine oligoribonucleotide complex. The structure reveals a bipartite RNAbinding motif on the distal face that is composed of a purine nucleotide-specificity site (R-site) and a non-discriminating linker site (L-site). The (R–L)- binding motif, which is also utilized by Bacillus subtilis Hfq to bind (AG) 3 A, differs from the (A–R–N) tripartite poly(A) RNA-binding motif of Escherichia coli Hfq whereby the Sa Hfq R-site strongly prefers adenosine, is more aromatic and permits deeper insertion of the adenine ring. R-site adenine-stacking residue Phe30, which is conserved among Grampositive bacterial Hfqs, and an altered conformation about β3 and β4 eliminate the adenosine-specificity site (A-site) and create the L-site. Binding studies show that Sa Hfq binds (AU) 3 A≈(AG) 3 A ≥ (AC) 3 A > (AA) 3 A and L-site residue Lys33 plays a significant role. The (R–L) motif is likely utilized by Hfqs from most Gram-positive bacteria to bind alternating (A–N) n RNA.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Structure, mechanical, and frictional properties of hydrogenated fullerene-like amorphous carbon film prepared by direct current plasma enhanced chemical vapor deposition

In this study, fullerene like carbon (FL-C) is introduced in hydrogenated amorphous carbon (a-C:H) film by employing a direct current plasma enhanced chemical vapor deposition. The film has a low friction and wear, such as 0.011 and 2.3 × 10{sup −9}mm{sup 3}/N m in the N{sub 2}, and 0.014 and 8.4 × 10{sup −8}mm{sup 3}/N m in the humid air, and high hardness and elasticity (25.8 GPa and 83.1%), to make further engineering applications in practice. It has several nanometers ordered domains consisting of less frequently cross-linked graphitic sheet stacks. We provide new evidences for understanding the reported Raman fit model involving four vibrational frequencies from five, six, and seven C-atom rings of FL-C structures, and discuss the structure evolution before or after friction according to the change in the 1200 cm{sup −1} Raman band intensity caused by five- and seven-carbon rings. Friction inevitably facilitates the transformation of carbon into FL-C nanostructures, namely, the ultra low friction comes from both such structures within the carbon film and the sliding induced at friction interface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Optical layout and mechanical structure of polarimeter-interferometer system for Experimental Advanced Superconducting Tokamak

A Far-InfaRed (FIR) three-wave POlarimeter-INTerferometer (POINT) system for measurement current density profile and electron density profile is under development for the EAST tokamak. The FIR beams are transmitted from the laser room to the optical tower adjacent to EAST via ∼20 m overmoded dielectric waveguide and then divided into 5 horizontal chords. The optical arrangement was designed using ZEMAX, which provides information on the beam spot size and energy distribution throughout the optical system. ZEMAX calculations used to optimize the optical layout design are combined with the mechanical design from CATIA, providing a 3D visualization of the entire POINT system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Structural mechanism of allosteric activation of TRPML1 by PI(3,5)P 2 and rapamycin

Transient receptor potential mucolipin 1 (TRPML1) is a Ca 2+ -permeable, nonselective cation channel ubiquitously expressed in the endolysosomes of mammalian cells and its loss-of-function mutations are the direct cause of type IV mucolipidosis (MLIV), an autosomal recessive lysosomal storage disease. TRPML1 is a ligand-gated channel that can be activated by phosphatidylinositol 3,5-bisphosphate [PI(3,5)P 2 ] as well as some synthetic small-molecule agonists. Recently, rapamycin has also been shown to directly bind and activate TRPML1. Interestingly, both PI(3,5)P 2 and rapamycin have low efficacy in channel activation individually but together they work cooperatively and activate the channel with high potency. To reveal the structural basis underlying the synergistic activation of TRPML1 by PI(3,5)P 2 and rapamycin, we determined the high-resolution cryoelectron microscopy (cryo-EM) structures of the mouse TRPML1 channel in various states, including apo closed, PI(3,5)P 2 -bound closed, and PI(3,5)P 2 /temsirolimus (a rapamycin analog)-bound open states. These structures, combined with electrophysiology, elucidate the molecular details of ligand binding and provide structural insight into how the TRPML1 channel integrates two distantly bound ligand stimuli and facilitates channel opening.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Structural Mechanisms and the Thermodynamic Description of the Isosymmetric Orbital Ordering in Rare-Earth Manganites

The observed specific features of the orbital phase transition in AMnO{sub 3} (A = La, Pr, …, Lu) are shown to be due to the appearance, at high temperatures, of rotational distortions of the cubic lattice, which cause anion displacements, which induce an “internal field” coinciding in symmetry with the order parameter, which describe the ordering of octahedra distorted due to the Jahn–Teller effect (orbital ordering). The effect of this “field” substantially determines the orbital ordering type, its temperature, and the phase transition order. The comparative analysis of the orbitally ordered states is performed for the entire AMnO{sub 3} series in both the framework of the phenomenological theory of phase transitions and on the base of the three-minimum multi-sublattice model proposed in this report. The peculiarities of magnetic transitions in manganites determined by the specific features of their structures are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

The Development of Expansion Plug Wedge Test for Clad Tubing Structure Mechanical Property Evaluation

To determine the tensile properties of irradiated fuel cladding in a hot cell, a simple test was developed at the Oak Ridge National Laboratory (ORNL) and is described fully in US Patent Application 20060070455, “Expanded plug method for developing circumferential mechanical properties of tubular materials.” This method is designed for testing fuel rod cladding ductility in a hot cell using an expandable plug to stretch a small ring of irradiated cladding material. The specimen strain is determined using the measured diametrical expansion of the ring. This method removes many complexities associated with specimen preparation and testing. The advantages are the simplicity of measuring the test component assembly in the hot cell and the direct measurement of the specimen’s strain. It was also found that cladding strength could be determined from the test results.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2019

Structural, mechanical, and antibacterial features of curcumin/polyurethane nanocomposites

Various types of bacteria inhabit many surfaces thus causing problems which can have very strong impact on human health. Here we present a study of photophysical, mechanical, and antibacterial properties of curcumin/polyurethane nanocomposites prepared by swell-encapsulation-shrink method. The prepared nanocomposites have been characterized for degree of swelling, surface morphology, mechanical properties, chemical contents, photoluminescence, hydrophobicity, potentials for singlet oxygen generation, and antibacterial activity. Dynamic mechanical analysis has shown slight changes of glass temperature of curcumin/polyurethane nanocomposites due to blue light irradiation. It was found that nanocomposites have very strong photoluminescence, become photoactive upon blue light irradiation at 470 nm and generate singlet oxygen. Conducted antibacterial tests have shown very strong activity of these nanocomposites especially toward Escherichia coli. These bacteria strains have been eliminated completely only after 1 h irradiation by blue light. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 47283. © 2018 Wiley Periodicals, Inc.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mechanical structure of the nucleon and the baryon octet: twist-2 case

We investigate the gravitational form factors (GFFs) of the nucleon and the baryon octet, decomposed into their flavor components, utilizing a pion mean-field approach grounded in the large N c limit of Quantum Chromodynamics (QCD). Our focus is on the contributions from the twist-2 operators to the flavor-triplet and octet GFFs, and we decompose the mass, angular momentum, and D-term form factors of the nucleon into their respective flavors. The strange quark contributions are found to be relatively mild for the mass and angular momentum form factors, while providing significant corrections to the D-term form factor. In the course of examining the flavor decomposition of the GFFs, we uncover that the effects of twist-4 operators play a crucial role. While the gluonic contributions are suppressed by the packing fraction of the instanton vacuum in the twist-2 case, contributions from twist-4 operators are of order unity, necessitating its explicit consideration.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

First-Principle Calculations on the Structural, Mechanical, and Electronic Properties of Mn{sub 2}RuSi and Mn{sub 2}RuGe Under Pressure

The second- and third-order elastic constants of the new Inverse Heusler compounds Mn{sub 2}RuZ (Z = Si, Ge) are determined from the first-principle calculations combined with homogeneous deformation methods. In terms of the second- and third- order elastic constants, the effective second-order elastic constants of Mn{sub 2}RuZ (Z = Si, Ge) are also presented. Besides, the pressure dependence of the brittle/ductile properties, elastic anisotropy factor, Young’s modulus, and Debye temperature is further investigated. It is found that both Mn{sub 2}RuSi and Mn{sub 2}RuGe display ductile nature at ground state and Mn{sub 2}RuGe has better ductility than Mn{sub 2}RuSi under different pressures. This phenomenon is improved by the Young’s modulus. Finally, the density of states of Mn{sub 2}RuZ (Z = Si, Ge) under different pressures is also calculated in order to reveal the origin of the effect of pressure on the the ductility of Mn{sub 2}RuZ (Z = Si, Ge).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗