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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Does feroxyhyte occur on the surface of Mars

The physical, chemical and paragenetic properties of delta-FeOOH in the form of the mineral feroxyhyte are discussed in relation to the possible composition of the red-brown surface coating of Mars. It is pointed out that the deep-brown ferromagnetic FeOOH polymorph will adhere to magnets such as those on the Viking Lander at Mars ambient temperatures and exhibits spectral maxima in the range 2.95-3.4 m similar to those observed in remote sensing spectra of Mars. The redox properties of the formation of feroxyhyte are shown to be compatible with postulated processes on the Martian surface, and with the results of some of the Viking biological experiments. It is thus concluded that feroxyhyte has the magnetic, chemisorption, spectral, redox and paragenetic properties to suggest its consideration as a possible component of the Martian surface.

Burns, R. G.↗
DOE OSTI2026

Metalloproteins in an Era of Modern Crystallography and Why the Beamline Matters

The Structural Molecular Biology (SMB) macromolecular crystallography (MC) group at the Stanford Synchrotron Radiation Lightsource (SSRL) have developed state-of-the-art capabilities tailored for metalloenzyme structural analysis. Metalloproteins sit at the center of biology’s most audacious chemistry. From multi-electron redox catalysis to radical rearrangements and light-driven transformations, metal sites give proteins access to reaction landscapes that would otherwise be inaccessible under ambient conditions. Yet their study presents a fundamental paradox for MC studies: the very X-rays we use to reveal atomic structure can alter the electronic states we seek to understand. As the field moves beyond static snapshots toward mechanistic insight, success increasingly depends on our ability to maintain metal centers in their native state throughout the experiment. The SSRL SMB-MC beamlines integrate a suite of capabilities specifically designed to address these challenges. By combining in situ spectroscopic verification, intelligent dose management, controlled reaction initiation, optimized anomalous diffraction, and real-time crystallographic diffraction analysis, these tools enable researchers to interrogate metalloproteins with unprecedented rigor. This article explores how these complementary approaches are reshaping our ability to capture metalloprotein chemistry, and what this means for mechanistic studies at synchrotron beamlines.

Maggiolo, Ailiena O. [SLAC National Accelerator La↗
DOE OSTI2020

The organic redox transistor for neuromorphic computing

Inspired by the in-memory computing architectures of biological systems, neuromorphic computing using crossbar arrays of artificial synapses based on non-volatile memory (NVM) devices with variable conductances has emerged as a new paradigm to enable massively parallel and ultra-low power computing hardware for data centric applications. Although inference has been demonstrated successfully using crossbars based on a variety of NMV technologies, efficient learning and scaling to large arrays (>10 6 elements) remains a challenge due to the synaptic elements' non-ideal electrical characteristics which degrades ANN accuracy. A further challenge is that in the conductive state memristors draw large currents >μA resulting in significant voltage drops in the interconnect wires and increased probability of failure in scaled arrays. We suggest the organic polymer redox transistor (RT) is an alternate approach that could solve many of these challenges, enabling both inference and parallel outer product updates, as recently demonstrated by Fuller et al. An RT consists of redox-active channel and gate electrodes in contact with a liquid or solid electrolyte. lon insertion through the electrolyte controls the channel electronic conductivity, while electron transfer through an external circuit maintains overall charge neutrality. Unlike a rechargeable battery, in the RT the voltage built-up across the electrolyte is kept to a minimum (typically <100 mV) by using the same material for the gate and channel. Elimination of the voltage offset simplifies integration of the RT into programmable arrays by enabling the use of various selectors. RTs based on inorganic and organic materials have been recently demonstrated with conductance tuning occurring at potentials of just a few mV and hundreds to thousands of linearly and symmetrically programmable conductance states, enabling near ideal accuracy in neural network simulations. Introduced in the 1980's, redox transistors with metallic gate electrodes and organic channel materials, also known as organic electrochemical transistors (OECTs), have been explored for a variety of applications such as chem- and bio-sensing, neural interfaces, and low cost printed circuits. A typical channel material for OECTs is the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS). PEDOT is a p-type semiconducting polymer with mobile positively charged polarons that hop chain-to-chain.

Talin, Albert Alec↗
DOE OSTI2022

Optical O 2 Sensors Also Respond to Redox Active Molecules Commonly Secreted by Bacteria

From a metabolic perspective, molecular oxygen (O 2 ) is arguably the most significant constituent of Earth’s atmosphere. Nearly every facet of microbial physiology is sensitive to the presence and concentration of O 2 , which is the most favorable terminal electron acceptor used by organisms and also a dangerously reactive oxidant. As O 2 has such sweeping implications for physiology, researchers have developed diverse approaches to measure O 2 concentrations in natural and laboratory settings. Recent improvements to phosphorescent O 2 sensors piqued our interest due to the promise of optical measurement of spatiotemporal O 2 dynamics. However, we found that our preferred bacterial model, Pseudomonas aeruginosa PA14, secretes more than one molecule that quenches such sen sors, complicating O 2 measurements in PA14 cultures and biofilms. Assaying supernatants from cultures of 9 bacterial species demonstrated that this phenotype is common: all super natants quenched a soluble O 2 probe substantially. Phosphorescent O 2 probes are often embedded in solid support for protection, but an embedded probe called O 2 NS was quenched by most supernatants as well. Measurements using pure compounds indicated that quenching is due to interactions with redox-active small molecules, including phena zines and flavins. Uncharged and weakly polar molecules like pyocyanin were especially potent quenchers of O 2 NS. These findings underscore that optical O 2 measurements made in the presence of bacteria should be carefully controlled to ensure that O 2 , and not bacterial secretions, is measured, and motivate the design of custom O 2 probes for specific organisms to circumvent sensitivity to redox-active metabolites.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Extracellular Charge Transport in Microbial Redox Chains: Linking the Living and Non-Living Worlds

The fundamental process of electron transfer (ET) within and between molecules dictates all biological energy conversion strategies, including respiration and photosynthesis. This project resulted in a comprehensive physics-based understanding of the mechanisms and limits of redox networks that mediate and regulate electron transport through microbial metabolic pathways, with special emphasis on environmental microbes that can acquire energy by catalyzing anodic or cathodic reactions on solid-state electrodes (extracellular electron transfer, or EET). By performing electron transfer to/from electrodes, such microbes may be used as biocatalysts for converting the energy stored in diverse chemical fuels to electricity, or vice versa (microbial electrosynthesis), in renewable energy technologies.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Terabase-Scale Coassembly of a Tropical Soil Microbiome

Petabases of reads are being produced by environmental metagenome sequencing. An essential step in analyzing these data is metagenome assembly, the computational reconstruction of genome sequences from microbial communities. “Coassembly” of metagenomic sequence data, in which multiple samples are assembled together, enables more complete detection of microbial genomes in an environment than “multiassembly,” in which samples are assembled individually.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Environmental matrix and moisture are key determinants of microbial phenotypes expressed in a reduced complexity soil-analog

Soil moisture and porosity regulate microbial metabolism by influencing factors such as redox conditions, substrate availability, and soil connectivity. However, the inherent biological, chemical, and physical heterogeneity of soil complicates laboratory investigations into microbial phenotypes that mediate community metabolism. This difficulty arises from challenges in accurately representing the soil environment and in establishing a tractable microbial community that limits confounding variables. To address these challenges in our investigation of community metabolism, we use a reduced-complexity microbial consortium grown in a soil analog using a glass-bead matrix amended with chitin. Long-read and short-read metagenomes, metatranscriptomes, metaproteomes, and metabolomes were analyzed to test the effects of soil structure and moisture on chitin degradation. Our soil structure analog system greatly altered microbial expression profiles compared to the liquid-only incubations, emphasizing the importance of incorporating environmental parameters, like pores and surfaces, for understanding microbial phenotypes relevant to soil ecosystems. These changes were mainly driven by differences in overall expression of chitin-degrading Streptomyces species and stress-tolerant Ensifer. Our findings suggest that the success of Ensifer in a structured environment is likely related to its ability to repurpose carbon via the glyoxylate shunt while potentially using polyhydroxyalkanoate granules as a C source. We also identified traits like motility, stress resistance, and biofilm formation that underlie the degradation of chitin across our treatments and inform how they may ultimately alter carbon use efficiency. Together our results demonstrate that community functions like decomposition are sensitive to environmental conditions and more complex than the multi-enzyme pathways involved in depolymerization.

Rodriguez-Ramos, Josue A↗
NASA NTRSDate not supplied

Investigating Biological Responses to Deep Space Radiation for Missions Beyond Low Earth Orbit (LEO) using Yeast

To enable long-term spaceflight missions and establish habitation on the Moon and Mars, we require a comprehensive understanding of the effects of chronic deep space radiation exposure on humans. BioSentinel is NASA’s first biological CubeSat to venture beyond Low Earth Orbit (LEO). It utilizes Saccharomyces cerevisiae (budding yeast) as a model organism to study biological responses to deep space radiation. Yeast share significant genetic homology with humans, including basic cellular metabolism and DNA repair mechanisms. In addition, unlike human cell cultures, yeast can survive the duration and constraints of a deep space mission. BioSentinel measures biological responses using an optical system and alamarBlue oxidation-reduction (redox) dye. Two strains of yeast are studied - a wild-type and a rad51 mutant strain that is deficient in DNA repair. Changes in metabolism and growth are monitored throughout the nominal 6-month mission. Preliminary tests indicate a significant change in the alamarBlue response to low-dose ionizing radiation (IR). Additionally, rad51 cells have shown an IR dose-dependent decrease in glucose uptake and accumulation of oxidized NADH (NAD+). These biomolecules are involved in reactions responsible for basic cell processes, including growth and development, signaling, and respiration. The current study expanded upon previous data by exposing yeast to deep space-relevant radiation. Glucose and NADH/NAD+ assays were conducted on yeast subjected to varying dosages of high-energy Fe-56 and simulated galactic cosmic rays (GCRs). The resulting data was analyzed using Excel and GraphPad Prism. A particular focus was to identify biomolecules resulting from aerobic respiration, which requires the presence of oxygen, or anaerobic processes. As long-term spaceflight missions draw near, it is increasingly important to characterize biological processes affected by the conditions of deep space. Studying biomolecular damage caused by deep space radiation may enable the development of engineering controls or biomedical therapeutics that mitigate health complications for future astronauts.

Kyra Keenan↗
NASA NTRS2009

Selective functionalization of carbon nanotube tips allowing fabrication of new classes of nanoscale sensing and manipulation tools

Embodiments in accordance with the present invention relate to techniques for the growth and attachment of single wall carbon nanotubes (SWNT), facilitating their use as robust and well-characterized tools for AFM imaging and other applications. In accordance with one embodiment, SWNTs attached to an AFM tip can function as a structural scaffold for nanoscale device fabrication on a scanning probe. Such a probe can trigger, with nanometer precision, specific biochemical reactions or conformational changes in biological systems. The consequences of such triggering can be observed in real time by single-molecule fluorescence, electrical, and/or AFM sensing. Specific embodiments in accordance with the present invention utilize sensing and manipulation of individual molecules with carbon nanotubes, coupled with single-molecule fluorescence imaging, to allow observation of spectroscopic signals in response to mechanically induced molecular changes. Biological macromolecules such as proteins or DNA can be attached to nanotubes to create highly specific single-molecule probes for investigations of intermolecular dynamics, for assembling hybrid biological and nanoscale materials, or for developing molecular electronics. In one example, electrical wiring of single redox enzymes to carbon nanotube scanning probes allows observation and electrochemical control over single enzymatic reactions by monitoring fluorescence from a redox-active cofactor or the formation of fluorescent products. Enzymes ''nanowired'' to the tips of carbon nanotubes in accordance with embodiments of the present invention, may enable extremely sensitive probing of biological stimulus-response with high spatial resolution, including product-induced signal transduction.

Wade, Lawrence A.↗
NASA NTRS2003

Treatment of Spacecraft Wastewater Using a Hollow Fiber Membrane Biofilm Redox Control Reactor

The purpose of this project was to develop and evaluate design concepts for biological treatment reactors for the purification of spacecraft wastewater prior to reverse osmosis treatment. The motivating factor is that wastewater recovery represents the greatest single potential reduction in the resupply requirements for crewed space missions. Spacecraft wastewater composition was estimated from the characteristics of the three major component streams: urine/flush water, hygiene water, and atmospheric condensate. The key characteristics of composite spacecraft wastewater are a theoretical oxygen demand of 4519 mg/L, of which 65% is nitrogenous oxygen demand, in a volume of 11.5 liter/crew-day. The organic carbon to nitrogen ratio of composite wastewater is 0.86. Urine represents 93% of nitrogen and 49% of the organic carbon in the composite wastestream. Various bioreaction scenarios were evaluated to project stoichiometric oxygen demands and the ability of wastewater carbon to support denitrification. Ammonia nitrification to the nitrite oxidation state reduced the oxygen requirement and enabled wastewater carbon to provide nearly complete denitrification. A conceptual bioreactor design was established using hollow fiber membranes for bubbleless oxygen transfer in a gravity-free environment, in close spatial juxtaposition to a second interspaced hollow fiber array for supplying molecular hydrogen. Highly versatile redox control and an enhanced ability to engineer syntrophic associations are stated advantages. A prototype reactor was constructed using a microporous hollow fiber membrane module for aeration. Maintaining inlet gas pressure within 0.25 psi of the external water pressure resulted in bubble free operation with no water ingress into hollow fiber lumens. Recommendations include the design and operational testing of hollow fiber bioreactors using: 1) Partial nitrification/nitrite predenitrification; 2) Limited aeration for simultaneous nitrification/denitrification or for nitrite reduction/ammonia oxidation; 3) Hydrogenotrophic denitrification.

Smith, Daniel P.↗
DOE OSTI2020

Direct Measurement of Crossover and Interfacial Resistance of Ion-Exchange Membranes in All-Vanadium Redox Flow Batteries

Among various components commonly used in redox flow batteries (RFBs), the separator plays a significant role, influencing resistance to current as well as capacity decay via unintended crossover. It is well-established that the ohmic overpotential is dominated by the membrane and interfacial resistance in most aqueous RFBs. The ultimate goal of engineering membranes is to improve the ionic conductivity while keeping crossover at a minimum. One of the major issues yet to be addressed is the contribution of interfacial phenomena in the influence of ionic and water transport through the membrane. In this work, we have utilized a novel experimental system capable of measuring the ionic crossover in real-time to quantify the permeability of ionic species. Specifically, we have focused on quantifying the contributions from the interfacial resistance to ionic crossover. The trade-off between the mass and ionic transport impedance caused by the interface of the membranes has been addressed. The MacMullin number has been quantified for a series of electrolyte configurations and a correlation between the ionic conductivity of the contacting electrolyte and the Nafion® membrane has been established. The performance of individual ion-exchange membranes along with a stack of various separators have been explored. We have found that utilizing a stack of membranes is significantly beneficial in reducing the electroactive species crossover in redox flow batteries compared to a single membrane of the same fold thickness. For example, we have demonstrated that the utilization of five layers of Nafion ® 211 membrane reduces the crossover by 37% while only increasing the area-specific resistance (ASR) by 15% compared to a single layer Nafion ® 115 membrane. Therefore, the influence of interfacial impedance in reducing the vanadium ion crossover is substantially higher compared to a corresponding increase in ASR, indicating that mass and ohmic interfacial resistances are dissimilar. We have expanded our analysis to a combination of commercially available ion-exchange membranes and provided a design chart for membrane selection based on the application of interest (short duration/high-performance vs. long-term durability). The results of this study provide a deeper insight into the optimization of all-vanadium redox flow batteries (VRFBs).

UV/Vis spectroscopy↗
DOE OSTI2022

Elucidation of complex respiratory chains: a straightforward strategy to monitor electron transfer between cytochromes

Abstract Cytochromes are electron transfer (ET) proteins essential in various biological systems, playing crucial roles in the respiratory chains of bacteria. These proteins are particularly abundant in electrogenic microorganisms and are responsible for the efficient delivery of electrons to the cells’ exterior. The capability of sending electrons outside the cells open new avenues to be explored for emerging biotechnological applications in bioremediation, microbial electrosynthesis, and bioenergy fields. To develop these applications, it is critical to identify the different redox partners and to elucidate the stepwise ET along the respiratory paths. However, investigating direct ET events between proteins with identical features in nearly all spectroscopic techniques is extremely challenging. Nuclear magnetic resonance (NMR) spectroscopy offers the possibility to overcome this difficulty by analysing the alterations of the spectral signatures of each protein caused by electron exchange events. The uncrowded NMR spectral regions containing the heme resonances of the cytochromes display unique and distinct signatures in the reduced and oxidized states, which can be explored to monitor ET within the redox complex. In this study, we present a strategy for a fast and straightforward monitorization of ET between c-type cytochromes, using as model a triheme periplasmic cytochrome and a membrane-associated monoheme cytochrome from the electrogenic bacterium Geobacter sulfurreducens. The comparison between the 1D 1H NMR spectra obtained for samples containing the two cytochromes and for samples containing the individual proteins clearly demonstrated a unidirectional ET within the redox complex. This strategy provides a simple and straightforward means to elucidate complex biologic respiratory ET chains.

Morgado, Leonor (ORCID:0000000237605180)↗
DOE OSTI2024

Cu site differentiation in tetracopper(I) sulfide clusters enables biomimetic N 2 O reduction

Copper clusters feature prominently in both metalloenzymes and synthetic nanoclusters that mediate catalytic redox transformations of gaseous small molecules. Such reactions are critical to biological energy conversion and are expected to be crucial parts of renewable energy economies. However, the precise roles of individual metal atoms within clusters are difficult to elucidate, particularly for cluster systems that are dynamic under operating conditions. Here, we present a metal site-specific analysis of synthetic Cu 4 (μ 4 -S) clusters that mimic the Cu Z active site of the nitrous oxide reductase enzyme. Leveraging the ability to obtain structural snapshots of both inactive and active forms of the synthetic model system, we analyzed both states using resonant X-ray diffraction anomalous fine structure (DAFS), a technique that enables X-ray absorption profiles of individual metal sites within a cluster to be extracted independently. Using DAFS, we found that a change in cluster geometry between the inactive and active states is correlated to Cu site differentiation that is presumably required for efficient activation of N 2 O gas. More precisely, we hypothesize that the Cu δ+ ∙∙∙Cu δ- pairs produced upon site differentiation are poised for N 2 O activation, as supported by computational modeling. These results provide an unprecedented level of detail on the roles of individual metal sites within the synthetic cluster system and how those roles interplay with cluster geometry to impact the reactivity function. We expect this fundamental knowledge to inform understanding of metal clusters in settings ranging from (bio)molecular to nanocluster to extended solid systems involved in energy conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Inference of photosynthetic capacity parameters from chlorophyll a fluorescence is affected by redox state of PSII reaction centers

Solar-induced chlorophyll fluorescence (SIF) has been used to infer photosynthetic capacity parameters (e.g., the maximum carboxylation rate V cmax , and the maximum electron transport rate J max ). However, the precise mechanism and practical utility of such approach under dynamic environments remain unclear. In this study, we used the balance between the light and carbon reactions to derive theoretical equations relating chlorophyll a fluorescence (ChlF) emission and photosynthetic capacity parameters, and formulated testable hypotheses regarding the dynamic relationships between the true total ChlF emitted from PSII (SIF PSII ) and V cmax and J max . We employed concurrent measurements of gas exchanges and ChlF parameters for 15 species from six biomes to test the formulated hypotheses across species, temperatures, and limitation state of carboxylation. Our results revealed that SIF PSII alone is incapable of informing the variations in V cmax and J max across species, even when SIF PSII is determined under the same environmental conditions. In contrast, the product of SIF PSII and the fraction of open PSII reactions q L , which indicates the redox state of PSII, is a strong predictor of both V cmax and J max , although their precise relationships vary somewhat with environmental conditions. Our findings suggest the redox state of PSII strongly influences the relationship between SIF PSII and V cmax and J max .

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRSDate not supplied

Tracking Metabolic Changes in Microbial Culture using Redox Measurements

During long-term space missions, microbial cultures accumulate the effects of low-dose radiation, microgravity, and other factors; altered growth and metabolic activity may occur before viability effects. This could affect functionality of bioreactors or other bio-enabled mission systems, as well as shed light on human health. Spaceflight microbiology studies beyond the low Earth orbit exposure afforded by the ISS have been limited. Nanosatellites offer an increasingly popular alternative for deep space missions. However, the communications delay requires biofluidic automation of a pre-defined experimental protocol, and the lack of sample return (reliance on sensors in flight) can significantly limit feasible investigations. Previous biological CubeSats (PharmaSat, O/OREOS, EcAMSat) have used alamarBlue, an off-the-shelf formulation of the redox indicator dye resazurin, to track metabolic activity, as will BioSentinel, the upcoming interplanetary microbiology experiment. A series of ground experiments (see abstracts by Liddell, Santa Maria, and A. Kim) were conducted using a microbial culture system outfitted with an electrochemical sensor array (electrical conductivity, pH, oxidation-reduction potential, and dissolved oxygen) with alamarBlue and the same strain of Saccharomyces cerevisiae as BioSentinel. By improving mapping of measured changes in alamarBlue kinetics to physicochemical changes, and ultimately to biological alterations such as shifted metabolic pathways, this work supplements data analyses from past missions and planning for future missions using alamarBlue to characterize space radiation effects. Initial results indicate that alamarBlue acts like a redox buffer; its presence significantly changes redox kinetics in otherwise identical cultures. The initial color change (blue resazurin reduced to red/pink resorufin) appears as a redox plateau. A second plateau, likely corresponding to the second color transition (resorufin to the colorless hydroresorufin), occurs at a lower redox value. The relationship to carbon source exhaustion, dissolved oxygen depletion, cell death, and measured redox potential is complex and still under study.

Tracking↗
DOE OSTI2022

The role of lignin in the conversion of wheat straw to cellobionic acid by Neurospora crassa HL10

An engineered Neurospora crassa strain (HL10) naturally produces cellulases, cellobiose dehydrogenase (CDH), and heterologously expresses laccase. It can convert Avicel (cellulose) to cellobionic acid (cellobionate) without any enzyme addition at high yields. However, the addition of a catalytic amount of artificial redox mediators was required to achieve a high yield conversion. When a lignocellulosic substrate like wheat straw was used as the carbon source, it was found that adding exogenous artificial redox mediators did not improve cellobionate yield. We hypothesized that lignin and lignin degradation products were able to serve as redox mediators for the CDH-laccase conversion system. Experiments were designed to prove the hypothesis. When N. crassa HL10 was grown on Avicel, the addition of enzyme hydrolyzed lignin (EHL) can achieve a similar level of cellobionate production as with ABTS addition. The addition of EHL can increase the cellobionate production rate in the CDH-laccase bi-enzyme system using cellobiose as the substrate. The formation of lignin radicals, and the quenching of lignin radicals by reduced CDH, were verified by an electron paramagnetic resonance (EPR) experiment, providing further evidence that lignin radicals can serve as the electron acceptor of reduced CDH. Hence, lignocellulosic biomass is a self-sufficient substrate for the production of cellobionate. The conversion of the lignocellulosic substrate to cellobionate using N. crassa HL10 can be achieved without any exogenous enzyme addition or redox mediator addition.

59 BASIC BIOLOGICAL SCIENCES↗