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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Synthesis and characterization of zinc borophosphates with ANA-zeotype framework by the microwave method

Zinc borophosphate (NH{sub 4}){sub 16}[Zn{sub 16}B{sub 8}P{sub 24}O{sub 96}] (denoted as ZnBP-ANA) with ANA-zeotype structure has been synthesized by employing microwave-assisted solvothermal synthesis in the reaction system ZnCl{sub 2}∙6H{sub 2}O-(NH{sub 4}){sub 2}HPO{sub 4}–H{sub 3}BO{sub 3} using ethylene glycol as a co-solvent. The influences of various experimental parameters, such as reaction temperature, solvent ratio, zinc precursors and reactive power, have been systematically investigated. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), and so on. Small and homogeneous ZnBP-ANA single crystal with regular cube morphology are crystallized by using microwave solvothermal synthesis method within a shorter time, and its grain size decreases with power. - Graphical abstract: Tailor-made ANA zeolites with varied size can be prepared by simply changing the reaction power. - Highlights: • Zinc borophosphate zeolites with ANA-zeotype structures were prepared by microwave technique. • The size of crystals could be controlled by tuning power. • Synthesis period can be significantly reduced by raising reaction temperature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Microstructural, optical and electrical investigations of Sb-SnO{sub 2} thin films deposited by spray pyrolysis

Highlights: • We controlled structural, morphological, electrical, optical and physical (such as band gap energy) properties by altering the Sb doping concentration. • Variation in bandgap with Sb concentration is in agreement with the Burstein–Moss hypothesis and this hypothesis was further confirmed by plotting E{sub g} vs n{sup 2/3}. • The resistivity and mobility are in the range of 1.512–6.624 × 10{sup −3} Ω cm and 9.75–22.96 cm{sup 2} V{sup −1} s{sup −1}. The e-density lies between 4.11 × 10{sup 19} and 4.24 × 10{sup 20} cm{sup −3}. • We observed that Sb substitution in SnO{sub 2} lattice decreases the crystallite size and the possible reason for this is the creation of Sb monolayer on the surface of SnO{sub 2} crystallite. - Abstract: The structural, optical and electrical properties of spray deposited antimony (Sb) doped tin oxide (SnO{sub 2}) thin films, prepared from SnCl{sub 4} precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0 to 1.5 wt.% of Sb. The analysis of X-ray diffraction patterns revealed that the as deposited doped and undoped tin oxide thin films are pure crystalline tetragonal rutile phase of tin oxide which belongs to the space group P4{sub 2}/mnm (number 136). The surface morphological examination with field emission scanning electron microscopy (FESEM) revealed the fact that the grains are closely packed and pores/voids between the grains are very few. The resistivity (ρ) and mobility (μ) are in the range of 1.512 × 10{sup −3}–6.624 × 10{sup −3} Ω cm and 9.75–22.96 cm{sup 2} V{sup −1} s{sup −1}. The electron density lies between 4.11 × 10{sup 19} and 4.24 × 10{sup 20} cm{sup −3}. A thorough electrical investigation reveals that the film's resistivity depends on carrier concentration. It is found that ionized impurity scattering is the dominant mechanism, which limits the mobility of the carriers. The transmittance spectra for as-deposited films were recorded in the wavelength range of 200–1000 nm. The transmittance of the films was observed to increase from 57% to 68% (at 800 nm) on initial addition of Sb (up to [Sb]/[Sn] = 0.5 wt.%) and then it is decreased for higher level of antimony doping ([Sb]/[Sn] >0.5 wt.%)

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis, characterization, and catalytic application of ordered mesoporous carbon–niobium oxide composites

Graphical abstract: The ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process. - Highlights: • Ordered mesoporous carbon–niobium oxide composites were synthesized. • The content of Nb{sub 2}O{sub 5} in the composites could be tuned from 38 to 75%. • Niobium species were highly dispersed in amorphous carbon framework walls. • The composites exhibited good catalytic performance in the dehydration of fructose. - Abstract: Ordered mesoporous carbon–niobium oxide composites have been synthesized by a multi-component co-assembly method associated with a carbonization process using phenolic resol as carbon source, niobium chloride as precursor and amphiphilic triblock copolymer Pluronic F127 as template. The resulting materials were characterized using a combination of techniques including differential scanning calorimetry–thermogravimetric analysis, N{sub 2} physical adsorption, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show that with increasing the content of Nb{sub 2}O{sub 5} from 38 to 75% the specific surface area decreases from 306.4 to 124.5 m{sup 2} g{sup −1}, while the ordered mesoporous structure is remained. Niobium species is well dispersed in the amorphous carbon framework. The mesoporous carbon–niobium oxide composites exhibit high catalytic activity in the dehydration of fructose to 5-hydroxymethylfurfural. A 100% conversion of fructose and a 76.5% selectivity of 5-hydroxymethylfurfural were obtained over the carbon–niobium oxide composite containing 75% Nb{sub 2}O{sub 5} under the investigated reaction conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis and luminescent properties of Tb3+ doped BaLa2ZnO5 nanoparticles

Highlights: • First combustion-synthesis report of BaLa{sub 2-x}ZnO{sub 5}:xTb{sup 3+} nanophosphors. • Lattice parameters and atomic positions have been refined. • Critical distance for non-radiative energy transfer has been calculated. • These nanophosphors are suitable candidate for solid state lighting. • Some blue to green color tunability has been found. - Abstract: Nanophosphor powders of composition BaLa{sub 2}ZnO{sub 5}:Tb{sup 3+} have been synthesized via using urea assisted solution combustion method using metal nitrates as the precursor materials. The structural, morphological and luminescent properties have been investigated by powder X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The Rietveld analysis showed that these nanophosphors crystallize in the tetrahedral phase with the 14/mcm (140) space group. The crystallite size was determined by Scherer formula and was found to be 70 nm. The photoluminescent excitation of these nanocrystals at 278 nm yielded the characteristic emission peaks at 545 nm and 489 nm due to {sup 5}D{sub 4} → {sup 7}F{sub 5} (magnetic-dipole) and {sup 5}D{sub 4} → {sup 7}F{sub 6} (electric-dipole) transitions, respectively. The optimum activator concentration was found to be 3 mol% and the concentration quenching arising from the over-doping was attributed to the quadrupole–quadrupole interactions. The excellent luminescent profile of these nano-scaled particles suggests their auspicious applications in the solid-state lighting and display technology.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

Nanocluster Rearrangement Forms a Family of Ordered Cerium–Titanium Bimetallic Metal–Organic Frameworks with Three Different Nodes, Nanocavities, and Thermal Stabilities

Metal–organic frameworks (MOFs) provide a versatile platform for incorporating multiple metal ions within a single crystalline framework, yet achieving spatial and stoichiometric order in heterometallic nodes remains a synthetic challenge. Building on our previously reported, highly thermally stable Ce/Ti bimetallic MOF NU-3000, we identified and isolated two additional crystalline phases, NU-2998 and NU-2999, that arise from the same Ce/Ti nanocluster precursor under modified solvothermal conditions. Systematic variation of reaction temperature, time, solvent ratio, and modulator concentration directs the assembly of these distinct frameworks. Structural analysis and comprehensive characterization studies reveal that these MOFs each feature an unreported nodal geometry with nanocavities of different sizes. NU-2998 even adopts an unreported topology, denoted nui , that features an elongated pore spanning 4 nm. Together, these findings establish a synthesis route that starts with a nanocluster and ends with a set of bimetallic MOFs, offering a glimpse into the pathway-dependent assembly of multimetallic porous materials. Finally, we evaluated the thermal stability of each additional analogue and compared them to NU-3000, providing further insight into material stability. NU-3000 maintained the highest thermal stability and was evaluated as a catalyst for CO oxidation at elevated temperatures.

bimetallic MOFs↗
DOE OSTI2015

Genomic distribution of B-vitamin auxotrophy and uptake transporters in environmental bacteria from the Chloroflexi phylum

Bacteria from the Chloroflexi phylum are dominant members of phototrophic microbial mat communities in terrestrial thermal environments. Vitamins of B-group are key intermediates (precursors) in the biosynthesis of indispensable enzyme cofactors driving numerous metabolic processes in all forms of life. A genomics-based reconstruction and comparative analysis of respective biosynthetic and salvage pathways and riboswitch regulons in over 20 representative Chloroflexi genomes revealed a widespread auxotrophy for some of the vitamins. The most prominent predicted phenotypic signature, auxotrophy for vitamins B1 and B7 was experimentally confirmed for the best studied model organism Chloroflexus aurantiacus. These observations along with identified candidate genes for the respective uptake transporters pointed to B vitamin exchange as an important aspect of syntrophic metabolism in microbial communities. Inferred specificities of homologous substrate-binding components of ABC transporters for vitamins B1 (ThiY) and B2 (RibY) were verified by thermofluorescent shift approach. A functional activity of the thiamine-specific transporter ThiXYZ from C. aurantiacus was experimentally verified by genetic complementation in E. coli. Expanding the integrative approach, which was applied here for a comprehensive analysis of B-vitamin metabolism in Chloroflexi would allow reconstruction of metabolic interdependencies in microbial communities.

Chloroflexi↗
DOE OSTI2014

Surface chemistry of a Cu(I) beta-diketonate precursor and the atomic layer deposition of Cu{sub 2}O on SiO{sub 2} studied by x-ray photoelectron spectroscopy

The surface chemistry of the bis(tri-n-butylphosphane) copper(I) acetylacetonate, [({sup n}Bu{sub 3}P){sub 2}Cu(acac)] and the thermal atomic layer deposition (ALD) of Cu{sub 2}O using this Cu precursor as reactant and wet oxygen as coreactant on SiO{sub 2} substrates are studied by in-situ x-ray photoelectron spectroscopy (XPS). The Cu precursor was evaporated and exposed to the substrates kept at temperatures between 22 °C and 300 °C. The measured phosphorus and carbon concentration on the substrates indicated that most of the [{sup n}Bu{sub 3}P] ligands were released either in the gas phase or during adsorption. No disproportionation was observed for the Cu precursor in the temperature range between 22 °C and 145 °C. However, disproportionation of the Cu precursor was observed at 200 °C, since C/Cu concentration ratio decreased and substantial amounts of metallic Cu were present on the substrate. The amount of metallic Cu increased, when the substrate was kept at 300 °C, indicating stronger disproportionation of the Cu precursor. Hence, the upper limit for the ALD of Cu{sub 2}O from this precursor lies in the temperature range between 145 °C and 200 °C, as the precursor must not alter its chemical and physical state after chemisorption on the substrate. Five hundred ALD cycles with the probed Cu precursor and wet O{sub 2} as coreactant were carried out on SiO{sub 2} at 145 °C. After ALD, in-situ XPS analysis confirmed the presence of Cu{sub 2}O on the substrate. Ex-situ spectroscopic ellipsometry indicated an average film thickness of 2.5 nm of Cu{sub 2}O deposited with a growth per cycle of 0.05 Å/cycle. Scanning electron microscopy and atomic force microscopy (AFM) investigations depicted a homogeneous, fine, and granular morphology of the Cu{sub 2}O ALD film on SiO{sub 2}. AFM investigations suggest that the deposited Cu{sub 2}O film is continuous on the SiO{sub 2} substrate.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis of Hybrid Materials Based on Iron Nanoparticle-Decorated Multiwalled Carbon Nanotubes

Fe-containing nanoparticles have been grown for the first time on the surface of multiwalled carbon nanotubes by metalorganic chemical vapor deposition using iron acetylacetonate, Fe(acac){sub 3}, as a precursor. The resultant hybrid nanomaterial has been characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and thermogravimetric analysis. The results demonstrate that the synthesized material consists of multiwalled carbon nanotubes whose surface is decorated with iron nanoparticles.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Optimizing New Dark Energy Experiments

Next generation “Stage IV” dark energy experiments under design during this grant, and now under construction, will enable the determination of the properties of dark energy and dark matter to unprecedented precision using multiple complementary probes. The most pressing challenge in these experiments is the characterization and understanding of the systematic errors present within any given experimental configuration and the resulting impact on the accuracy of our constraints on dark energy physics. The DETF and the P5 panel in their reports recommended “Expanded support for ancillary measurements required for the long-term program and for projects that will improve our understanding and reduction of the dominant systematic measurement errors.” Looking forward to the next generation Stage IV experiments we have developed a program to address the most important potential systematic errors within these experiments. Using data from current facilities it has been feasible and timely to undertake a detailed investigation of the systematic errors. In this DOE grant we studied of the source and impact of the dominant systematic effects in dark energy measurements, and developed new analysis tools and techniques to minimize their impact. Progress under this grant is briefly reviewed in this technical report. This work was a necessary precursor to the coming generations of wide-deep probes of the nature of dark energy and dark matter. The research has already had an impact on improving the efficiencies of all Stage III and IV dark energy experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

A Genome-Scale Metabolic Model of Anabaena 33047 to Guide Genetic Modifications to Overproduce Nylon Monomers

Nitrogen fixing-cyanobacteria can significantly improve the economic feasibility of cyanobacterial production processes by eliminating the requirement for reduced nitrogen. Anabaena sp. ATCC 33047 is a marine, heterocyst forming, nitrogen fixing cyanobacteria with a very short doubling time of 3.8 h. We developed a comprehensive genome-scale metabolic (GSM) model, iAnC892, for this organism using annotations and content obtained from multiple databases. iAnC892 describes both the vegetative and heterocyst cell types found in the filaments of Anabaena sp. ATCC 33047. iAnC892 includes 953 unique reactions and accounts for the annotation of 892 genes. Comparison of iAnC892 reaction content with the GSM of Anabaena sp. PCC 7120 revealed that there are 109 reactions including uptake hydrogenase, pyruvate decarboxylase, and pyruvate-formate lyase unique to iAnC892. iAnC892 enabled the analysis of energy production pathways in the heterocyst by allowing the cell specific deactivation of light dependent electron transport chain and glucose-6-phosphate metabolizing pathways. The analysis revealed the importance of light dependent electron transport in generating ATP and NADPH at the required ratio for optimal N2 fixation. When used alongside the strain design algorithm, OptForce, iAnC892 recapitulated several of the experimentally successful genetic intervention strategies that over produced valerolactam and caprolactam precursors.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Effect of annealing temperature on structural, morphological and electrical properties of nanoparticles TiO{sub 2} thin films by sol-gel method

In this paper, the sol-gel method is used to prepare nanoparticles titanium dioxide (TiO{sub 2}) thin films at different annealing temperature. The prepared sol was deposited on the p-SiO{sub 2} substrates by spin coating technique under room temperature. The nanoparticles TiO{sub 2} solution was synthesized using Ti{OCH(CH_3)_2}{sub 4} as a precursor with an methanol solution at a molar ratio 1:10. The prepared TiO{sub 2} sols will further validate through structural, morphological and electrical properties. From the X-ray diffraction (XRD) analysis, as-deposited films was found to be amorphous in nature and tend to transform into tetragonal anatase and rutile phase as the films annealed at 573 and 773 K, respectively. The diversification of the surface roughness was characterized by atomic force microscopy (AFM) indicated the roughness and thickness very dependent on the annealing temperature. The two-point probe electrical resistance and conductance of nanoparticles TiO{sub 2} thin films were determined by the DC current-voltage (IV) analysis. From the I-V measurement, the electrical conductance increased as the films annealed at higher temperature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Co-hydrotreatment of Bio-oil and Waste Cooking Oil to Produce Transportation Fuels

This paper reports the co-hydrotreatment of the heavy bio-oil fraction with waste cooking oil (WCO) using NiMo/γ-Al 2 O 3 catalyst, followed by the distillation of resulting deoxygenated oil and the characterization of resulting fuel cuts. The heavy BTG bio-oil fraction was obtained by removing the very reactive light-oxygenated compounds via rotary evaporation, subsequently mixed with 1-butanol. The resulting oil was blended with WCO and subjected to a two-step co-hydrotreatment process. The first step, called “stabilization,” is aimed at saturating highly reactive hydrogen-deficient compounds. The second step, called “deoxygenation,” aimed to remove bio-oil oxygen, primarily as H 2 O. This study examined the impact of varying bio-oil concentrations (0, 10, 20, 30, 40 wt.% of WCO) on the upgraded oil's yield, composition, and fuel properties. The resulting hydrotreated oil was distilled into gasoline-range, kerosene-range, and diesel-range hydrocarbons at <150 °C, 150 to 250 °C, and 250 to 350 °C, respectively. The yield of the hydrotreated oil indicates that as the bio-oil concentration increases, the amounts of coke (0.7 to 2.4 %) and water (2 to 10 wt. %) increase while the organic layer yields decrease (80 to 63 %). The coke yield was comparable to the coke yield obtained when co-processing the pyrolytic lignin fraction. This suggests that coke is formed from both the sugar oligomers and the lignin-derived oligomers. The UV-fluorescence analysis on the hydrotreated oil shows that more polycondensed and conjugated ring compounds formed as the bio-oil concentration is increased. These compounds are precursors of coke. FTIR results showed that most raw materials were converted to biofuels after the hydrotreatment. To achieve less than 1 wt. % of coke yield, blends with up to 20 wt. % pyrolysis oil should be used. An increase in bio-oil concentration leads to a slight increase in gasoline yield and a decrease in kerosene and diesel yields. The identified carbon species found in the fuel cuts include n-paraffin, iso-paraffin, cycloparaffin, and aromatics. Further, the jet fuel cut (kerosene) was characterized by density, surface tension, and viscosity. Our product conforms to the standard specifications for sustainable aviation fuels (Jet A-1). Further research is suggested to fine-tune the operating parameters for achieving reduced coke yield and enhanced kerosene yield.

09 BIOMASS FUELS↗
DOE OSTI2019

Formation of two-dimensional transition metal oxide nanosheets with nanoparticles as intermediates

According to the article, two-dimensional (2D) materials have attracted significant interest because of their large surface-to-volume ratios and electron confinement. Compared to common 2D materials such as graphene or metal hydroxides, with their intrinsic layered atomic structures, the formation mechanisms of 2D metal oxides with a rocksalt structure are not well understood. Here, we report the formation process for 2D cobalt oxide and cobalt nickel oxide nanosheets, after analysis by in situ liquid-phase transmission electron microscopy. Our observations reveal that three-dimensional (3D) nanoparticles are initially formed from the molecular precursor solution and then transform into 2D nanosheets. Ab initio calculations show that a small nanocrystal is dominated by positive edge energy, but when it grows to a certain size, the negative surface energy becomes dominant, driving the transformation of the 3D nanocrystal into a 2D structure. Uncovering these growth pathways, including the 3D-to-2D transition, provides opportunities for future material design and synthesis in solution.

Chemistry↗
DOE OSTI2026

Solvent selection for a biomass-to-bioproduct pipeline through integrated reductive catalytic fractionation and microbial funneling

The growing significance of lignin-first biorefineries, which focus on upgrading the aromatics resulting from lignin depolymerization, presents opportunities for bioproduct synthesis using microbial strains capable of funneling a diverse array of phenolics into a single commodity chemical. In this study, we evaluated a biomass-to-bioproduct pipeline involving the reductive catalytic fractionation (RCF) of poplar biomass followed by biological funneling with a Novosphingobium aromaticivorans strain that produces 2-pyrone-4,6-dicarboxylic acid (PDC), a potential bioplastic precursor. Considering the impact of solvent on RCF reactor operating pressure, and the potential inhibitory effects of solvent on downstream microbial funneling, we performed an analysis of six pure solvents, namely methanol, ethanol, isopropanol, isobutanol, 1,4-dioxane and ethylene glycol, and different variations of their aqueous mixtures comprising 5 to 50 vol% water. For each pure solvent and solvent/water system, we measured phenolic monomer yields in the RCF process and PDC yields from the phenolic monomers. We then developed correlation models that relate phenolic monomer yields from RCF-derived samples to Hansen solubility parameters to determine solvent descriptors that contribute to high yields. Furthermore, we developed an integrated biorefinery system to estimate the minimum selling price (MSP) of PDC and the associated carbon footprint to identify solvent systems with better costs and sustainability metrics. These analyses resulted in the 50 vol% methanol/water system being identified as optimal because it reduces RCF reactor pressure and is compatible with microbial funneling with N. aromaticivorans. This solvent system produced 63 g PDC per kg biomass (264 g PDC per kg lignin) from 85 g phenolic monomers per kg biomass at a reduced reactor pressure of 48 bar (reduced by 26% compared to our previous poplar-to-PDC pipeline). The MSP for this system is $\$$13.98 per kg of purified PDC (carbon footprint of 1.47 kg CO 2 e per kg), which is about 24% lower than a previously described poplar-to-PDC pipeline and 46% lower than a lignin-to-PDC pipeline that used pure methanol as the solvent. The results from this study illustrate improvements that can be made in lignocellulosic biorefineries that are compatible with the hybrid chemical and biological processes needed to gain value from lignin.

Sripada, Sarada [Great Lakes Bioenergy Research Ce↗
DOE OSTI2014

Magnetocaloric effect in as-cast Gd{sub 1−x}Y{sub x} alloys with x = 0.0, 0.1, 0.2, 0.3, 0.4

In this report, we present the magnetocaloric effect of Gd{sub 1−x}Y{sub x} alloys (0.0 ≤ × ≤ 0.4) prepared by arc-melting from high purity Gd and Y precursors in inert atmosphere. The formation of Gd{sub 1−x}Y{sub x} solid solutions was verified by means of X-ray diffraction analysis across the compositional series; also, residual secondary phases Gd and Y were present. Magnetic characterization performed by Vibrating Sample Magnetometry at a maximum applied field of 3.0 T showed a drastic reduction of the magnetization saturation (from 233 emu/g for x = 0.0 to 183 emu/g for x = 0.4), due to a dilution effect of the Y alloying, together with a marked Curie temperature decrease from 296 K to 196 K between x = 0.0 and x = 0.4. The second-order character of the magnetic transition was established by Arrot plots for all the cases. On the other hand, the magnetic entropy variation, determined from numerical integration of Maxwell relation displayed excellent values above 5.30 J/kg K for alloys with x < 0.3 due to the steep transition of the thermomagnetic curves.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Affinity maturation in a human humoral response to influenza hemagglutinin

Affinity maturation of the B cell antigen receptor (BCR) is a conserved and crucial component of the adaptive immune response. BCR lineages, inferred from paired heavy- and light-chain sequences of rearranged Ig genes from multiple descendants of the same naive B cell precursor (the lineages’ unmutated common ancestor, “UCA”), make it possible to reconstruct the underlying somatic evolutionary history. We present here an extensive structural and biophysical analysis of a lineage of BCRs directed against the receptor binding site (RBS) of subtype H1 influenza virus hemagglutinin (HA). The lineage includes 8 antibodies detected directly by sequencing, 3 in 1 principal branch and 5 in the other. When bound to HA, the heavy-chain third complementarity determining region (HCDR3) fits with an invariant pose into the RBS, but in each of the 2 branches, the rest of the Fab reorients specifically, from its position in the HA-bound UCA, about a hinge at the base of HCDR3. New contacts generated by the reorientation compensate for contacts lost as the H1 HA mutated during the time between the donor’s initial exposure and the vaccination that preceded sampling. Our data indicate that a “pluripotent” naive response differentiated, in each branch, into 1 of its possible alternatives. This property of naive BCRs and persistence of multiple branches of their progeny lineages can offer broader protection from evolving pathogens than can a single, linear pathway of somatic mutation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Mechanistic insight into protein modification and sulfur mobilization activities of noncanonical E1 and associated ubiquitin-like proteins of Archaea

Here we provide the first detailed biochemical study of a noncanonical E1-like enzyme with broad specificity for cognate ubiquitin-like (Ubl) proteins that mediates Ubl protein modification and sulfur mobilization to form molybdopterin and thiolated tRNA. Isothermal titration calorimetry and in vivo analyses proved useful in discovering that environmental conditions, ATP binding and Ubl type controlled the mechanism of association of the Ubl protein with its cognate E1-like enzyme (SAMP and UbaA of the archaeon Haloferax volcanii, respectively). Further analysis revealed ATP hydrolysis triggered the formation of thioester and peptide bonds within the Ubl:E1-like complex. Importantly, the thioester was an apparent precursor to Ubl protein modification but not sulfur mobilization. Comparative modeling to MoeB/ThiF guided the discovery of key residues within the adenylation domain of UbaA that were needed to bind ATP as well as residues that were specifically needed to catalyze the downstream reactions of sulfur mobilization and/or Ubl protein modification. UbaA was also found to be Ubl-automodified at lysine residues required for early (ATP binding) and late (sulfur mobilization) stages of enzyme activity revealing multiple layers of auto-regulation. Cysteine residues, distinct from the canonical E1 ‘active site’ cysteine, were found important in UbaA function supporting a model that this non-canonical E1 is structurally flexible in its active site to allow Ubl~adenylate, Ubl~E1-like thioester and cysteine persulfide(s) intermediates to form.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Syntrophic Co-Cultures of Clostridium Organisms to Produce Higher Alcohols & Other C6-C8 Metabolites (Final Report)

The goal of this project was to advance the systems biology understanding and predictive modeling of synthetic & syntrophic Clostridium microbial consortia, focusing on elucidation of metabolic networks and environmental signals in the consortia. The project has direct applicability to lignocellulosic-biomass based production of higher alcohols as advanced biofuels and C6-C8 metabolites, that can be used as chemicals or serve as biofuel precursors. This project studied and optimized three synthetic syntrophic systems. It examined the population dynamics using flow-cytometry, time-lapse microscopy and PCR analysis. 13C-based tracer analyses was used to examine the metabolite exchange between the syntrophic cell populations and the impact of those interactions on the transcriptome of the individual populations. To enhance our analytical and predictive capabilities, genome-scale models (GSMs) for these syntrophies was developed. RNAseq data for these syntrophic coculture systems were acquired to enable a molecular level understanding of the syntrophies aiming to identify the genetic networks of each organism in the co-culture and compare those against the networks of pure cultures.

09 BIOMASS FUELS↗