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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Isolation, structural modification of macrophin from endophytic fungus Phoma macrostoma and their cytotoxic potential

Four known metabolites, macrophin (1), rosellisin (2), 2-(2-hydroxy-5-6-methoxy-3-methylene-1,4-benzodioxin-2(3H)-one (3), and methoxyphenoxyacrylic acid (4) were isolated, for the first time, from an endophytic fungus, Phoma macrostoma inhabiting the inner tissue of medicinal plant Glycyrrhiza glabra Linn. Their structures were characterized by comparison of their NMR data with literature data, and X-ray diffraction data of macrophin (1) as described herein for the first time. The compounds (1–4) were evaluated for their growth-inhibitory activities against a panel of cancer cell lines. Of these substances, macrophin (1) showed prominent cytotoxic activity against the MDA-MB-231, T47D, MCF-7, and MIAPaCa-2 cancer-cell lines with IC{sub 50} values of 14.8, 8.12, 13.0, and 0.9 μM, respectively. This biological significance has prompted us to generate a series of five acylated analogs (1a–1e) of 1 to conduct structure–activity relationship (SAR) study. The result illustrates all the analogues (1a–1e) were more potent than 1 against MDMB-231 and MIAPaCa-2 cancer cell lines. The compound 1d, an n-butanoyl substituent, has been proven to be three-fold more potent than 1 with IC{sub 50} values of 0.3 and 3.7 µM against MIAPaCa-2 and MDMB-231 cell lines, respectively.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Characterization and modification of enzymes in the 2-ketoisovalerate biosynthesis pathway of Ralstonia eutropha H16

2-Ketoisovalerate is an important cellular intermediate for the synthesis of branched-chain amino acids as well as other important molecules, such as pantothenate, coenzyme A, and glucosinolate. This ketoacid can also serve as a precursor molecule for the production of biofuels, pharmaceutical agents, and flavor agents in engineered organisms, such as the betaproteobacterium Ralstonia eutropha. The biosynthesis of 2-ketoisovalerate from pyruvate is carried out by three enzymes: acetohydroxyacid synthase (AHAS, encoded by ilvBH), acetohydroxyacid isomeroreductase (AHAIR, encoded by ilvC), and dihydroxyacid dehydratase (DHAD, encoded by ilvD). In this study, enzymatic activities and kinetic parameters were determined for each of the three R. eutropha enzymes as heterologously purified proteins. AHAS, which serves as a gatekeeper for the biosynthesis of all three branched-chain amino acids, demonstrated the tightest regulation through feedback inhibition by l-valine (IC50 = 1.2 mM), l-isoleucine (IC50 = 2.3 mM), and l-leucine (IC50 = 5.4 mM). Intermediates in the valine biosynthesis pathway also exhibit feedback inhibitory control of the AHAS enzyme. In addition, AHAS has a very weak affinity for pyruvate (K-M = 10.5 mu M) and is highly selective towards 2-ketobutyrate (R = 140) as a second substrate. AHAIR and DHAD are also inhibited by the branched-chain amino acids, although to a lesser extent when compared to AHAS. Experimental evolution and rational site-directed mutagenesis revealed mutants of the regulatory subunit of AHAS (IlvH) (N11S, T34I, A36V, T104S, N11F, G14E, and N29H), which, when reconstituted with wild-type IlvB, lead to AHAS having reduced valine, leucine, and isoleucine sensitivity. The study of the kinetics and inhibition mechanisms of R. eutropha AHAS, AHAIR, and DHAD has shed light on interactions between these enzymes and the products they produce; it, therefore, can be used to engineer R. eutropha strains with optimal production of 2-ketoisovalerate for value-added materials.

Lu, JN↗
DOE OSTI2018

Modification of Thermo-Mechanical Properties of Recycled PET by Vinyl Acetate (VAc) Monomer Grafting Using Gamma Irradiation

Vinyl acetate (VAc) monomer of different percentage was grafted onto the recycled polyethylene terephthalate (r-PET) films using gamma irradiation. The properties of these modified films were characterized by Fourier transform infrared spectroscopy (FTIR), mechanical properties testing (Tensile strength, Elongation at break), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The Tensile Strength (TS) of the modified PET film increased by 132.25 % to the highest value of 50.12 MPa at 15% VAc monomer concentration at 3 kGy gamma dose, while the elongation at break (EB) decreased by 31.83 %. FTIR was used to investigate the molecular interaction of the modified films. TGA revealed that curve of the modified PET film shifted toward higher temperature region by 95 °C, which is very close to that of PET film made from virgin flakes. The results indicate that modified PET films of better mechanical and thermal properties were successfully prepared using VAc monomer grafting by gamma irradiation technique.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Potential of pinhão Coat as Constituents of Starch Based Films Using Modification Techniques

The potential of lignocellulosic fibers obtained by dry grinding of pinhão coat as fillers in starch filmogenic solutions for packaging applications was evaluated in this work. To improve the incorporation of this waste into the starch solutions different physical and chemical treatments were conducted. Thereafter, morphology, chemical structure, crystallinity and water absorption of the pinhão coat powders were determined. The composites were also characterized regarding their morphology, chemical structure, crystallinity, mechanical properties, water vapor permeability and hydrophilicity. Poor fiber/matrix adhesion and high water absorption of the fibers were evidenced. Consequently, water vapor permeability of composites was increased by incorporating the fibers. Moreover, mechanical properties were improved and the morphological results were used to support the water absorption differences among the powders. Regarding the food packaging applications, starch/pinhão coat composites appeared as promising materials to reach the requirements of respiring food products.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural Modification of Starch Nanoparticles Via Graft Copolymerization Using KMnO{sub 4}, HClO{sub 4} and HNO{sub 3} Redox Pair

The novelty addressed here is commenced with a view to use our formerly prepared starch nanoparticles (SNPs) of size around 80–100 nm as a starting substrate for grafting meth acrylic acid (MAA) using KMnO{sub 4}, HClO{sub 4} in presence of HNO{sub 3} as innovative redox pair in aqueous medium. This was done to see the effect of SNPs with respect to well-dispersed nanosized particles, large surface areas, biodegradability and reactivity on the rate and extent of grafting. Besides; maximize the graft yield and graft reaction efficiency and reduce the homopolymer formation to lower extent. This could be accomplished via an in-depth assessment into the chief factors affecting the polymerization reaction such as initiator, monomer, SNPs and acid concentrations, time and temperature of polymerization, and liquor ratio. The results obtained indicate that the magnitude of the polymer yield including graft yield, graft reaction efficiency and homopolymer formation are determined by these factors. The structure of the resultant copolymers was confirmed instrumentally by Fourier transforms infrared spectroscopy; while both the surface morphology, crystalline structure and thermal properties were characterized by scanning electron microscopy, X-ray diffraction and thermal gravimetric analysis. Furthermore, the resultant copolymers were evaluated as environmental remediation materials via cadmium ions and cationic dyes removal from their solutions with different extent; in addition to higher swelling and chemical resistance in water as polar solvent and hydrochloric acid as acidic solution. The anticipated mechanisms involved in the synthesis are reported.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Modification of Poly(L-lactide) via a Pectinate Polymethylphenylsilane-co-poly(ε-caprolactone)

To solve the problem of the hard and brittle mechanical properties of poly(L-lactide) (PLLA), a novel pectinate polymethylphenylsilane-co-poly(ε-caprolactone) (PCL-PMPS-PCL) has been designed to modify PLLA via the hydrolysis polycondensnsation of methylphenyldimethoxysilane and ring-opening polymerization of ε-caprolactone. The triblock copolymer is characterized with {sup 1}HNMR and GPC. It is harmonized with PLLA in chloroform to make smooth blending film. Incorporation of PCL-PMPS-PCL lowers T{sub g} of PLLA, enhances the macromolecular mobility, and facilitates PLLA to form defective crystals. Compared to the brittle PLLA, the cross section of blends is rough and uneven. With the blending amount of PCL-PMPS-PCL going up, the tensile strength curve has a downward glacis, while the elongation at a break climbs upward, and reaches 25% at 10 wt%, exhibiting that the typical characteristics of ductile material. At the same time, the tensile strength for 10 wt% PCL-PMPS-PCL/PLLA reserve about 60 MPa, so PCL-PMPS-PCL can serve as a candidate of plasticizing PLLA.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Modification of the Structure and Magnetic Properties of Cobalt-Doped Ferrihydrite Nanoparticles Under Heat Treatment

Nanoparticles of antiferromagnetic materials acquire the magnetic moment due to the surface effects and structural defects. According to the Neel hypothesis, magnetic moment μ{sub P} of a particle containing N magnetically active atoms with magnetic moment J can be estimated as μ{sub P} ∼ J · N{sup n} or μ{sub P} ∼ V{sup n}, where V is the particle volume. Numerous studies of the magnetic properties of ferrihydrite 5Fe{sub 2}O{sub 3}⋅9H{sub 2}O and ferritin revealed a value of n ≈ 1/2 for this material, in which Fe atoms have the octahedral surrounding of anions. We investigate the effect of low-temperature annealing of cobalt-doped ferrihydrite nanoparticles on their average size and magnetic properties. Using the Mössbauer spectroscopy study, we demonstrate that doping with Co makes Fe atoms enter the anion tetrahedra which leads to an increase in the exponent n〉1/2 in the expression μ{sub P} ∼ J · N{sup n}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Surface modification and optical properties of metal doped indium sulfide thin films

Indium sulfide (In{sub 2}S{sub 3}) thin films were prepared by chemical bath deposition method in same deposition conditions, and then doped by metals including Ag, Al and Cu. Produced films post annealed at 400 °C temperature about 1 h. The effects of different metal-doping on structural, morphological and optical properties of the films were investigated by means of X-ray diffraction, scanning electron microscopy, atomic force microscopy and UV–Vis spectroscopy analyses. Produced indium sulfide thin film was amorphous and doping process lead to shifts peaks in lower angles. Morphology and nanostructure of doped films changed completely. Compact doped films have been formed. Optical constants of the produced thin films were calculated using Kramers–Kronig relations on reflectivity curves. Different doping impurities changed optical curves and band gaps.

77 NANOSCIENCE AND NANOTECHNOLOGY↗