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DOE OSTI2014

Molecular Dynamics Study of the Proposed Proton Transport Pathways in [FeFe]-Hydrogenase

Possible proton channels in Clostridium pasteurianum [FeFe]-hydrogenase were investigated with molecular dynamics simulations. This study was undertaken to discern proposed channels, compare their properties, evaluate the functional channel, and to provide insight into the features of an active proton channel. Our simulations suggest that protons are not transported through water wires. Instead, a five-residue motif (E282, S319, E279, HOH, C299) was found to be the likely channel, consistent with experimental observations. This channel connects the surface of the enzyme and the di-thiomethylamine bridge of the catalytic H-cluster, permitting the transport of protons. The channel was found to have a persistent hydrogen bonded core (residues E279 to S319), with less persistent hydrogen bonds at the ends of the channel. The hydrogen bond occupancy in this network was found to be sensitive to the protonation state of the residues in the channel, with different protonation states enhancing or stabilizing hydrogen bonding in different regions of the network. Single site mutations to non-hydrogen bonding residues break the hydrogen bonding network at that residue, consistent with experimental observations showing catalyst inactivation. In many cases, these mutations alter the hydrogen bonding in other regions of the channel which may be equally important in catalytic failure. A correlation between the protein dynamics near the proton channel and the redox partner binding regions was also found as a function of protonation state. The likely mechanism of proton movement in [FeFe]-hydrogenases is discussed based on the structural analysis presented here. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at Pacific Northwest National Laboratory, and a portion of the research was performed using PNNL Institutional Computing at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

biomimetics↗

DOE OSTI2018

AIM2 accelerates the atherosclerotic plaque progressions in ApoE−/− mice

Highlights: • Our study demonstrated that AIM2 plays an important role in atherosclerosis. • We found that AIM2 could mediate GSDMD-N and pyroptosis in VSMCs for the first time. • We first found that AIM2 could affect ICAM-1 and macrophage recruitment in atherosclerosis. • We first found that ox-LDL can promote AIM2 expression through NF-κB signaling. Plaque formation is initiated and triggered by cell death in the vascular wall, which gradually leads to the progression of atherosclerosis. Pyroptosis is a newly discovered form of programmed cell death. Absent in melanoma 2 (AIM2), a member of the HIN-200 protein family, plays an important role in activating inflammasomes. However, the role and mechanism of AIM2 in atherosclerotic plaque progression has not been thoroughly elucidated to date. The effect of pyroptosis and the mechanism for this effect were investigated in apolipoprotein E-deficient (ApoE−/−) mice. AIM2 overexpression and inhibition were studied in ApoE−/− mice that were fed a high-fat diet. The specific role of AIM2 in vascular smooth muscle cells (VSMCs) was explored in vitro. The results showed that high fat diet increases the expression of AIM2, ICMA-1, GSDMD-N, which could be mediated by AIM2 expression. The plaque lesion area is lager with AIM2 overexpression. Moreover, TUNEL-positive cells were increased when AIM2 was overexpressed. With increased AIM2, macrophages were enhanced. In vitro studies showed that AIM2 and GSDMD-N expression correlated with ox-LDL levels in a concentration dependent manner. AIM2 expression is associated with NF-κB signaling activity and can be inhibited by NF-κB inhibitor. AIM2 mediated GSDMD activity through ASC, caspase1 pathway. EthD-III and TUNEL staining showed that AIM2 mediates pyroptosis in VSMCs. Our study suggests that AIM2 is not only a regular of inflammasome but also an active participant in atherosclerosis.

60 APPLIED LIFE SCIENCES↗

NASA NTRS2000

EphB2 guides axons at the midline and is necessary for normal vestibular function

Mice lacking the EphB2 receptor tyrosine kinase display a cell-autonomous, strain-specific circling behavior that is associated with vestibular phenotypes. In mutant embryos, the contralateral inner ear efferent growth cones exhibit inappropriate pathway selection at the midline, while in mutant adults, the endolymph-filled lumen of the semicircular canals is severely reduced. EphB2 is expressed in the endolymph-producing dark cells in the inner ear epithelium, and these cells show ultrastructural defects in the mutants. A molecular link to fluid regulation is provided by demonstrating that PDZ domain-containing proteins that bind the C termini of EphB2 and B-ephrins can also recognize the cytoplasmic tails of anion exchangers and aquaporins. This suggests EphB2 may regulate ionic homeostasis and endolymph fluid production through macromolecular associations with membrane channels that transport chloride, bicarbonate, and water.

Non-NASA Center↗

DOE OSTI2023

Analysis of neptunium oxides produced through modified direct denitration

Production of neptunium-237 ( 237 Np) target materials for plutonium-238 ( 238 Pu) radioisotope thermoelectric generators (RTGs) for deep space exploration requires advanced chemistry and engineering development. Currently, the domestic Pu-238 Supply Program at Oak Ridge National Laboratory produces neptunium dioxide (NpO 2 ) for target material using a modified direct denitration (MDD) flowsheet. Although the chemistry, reaction mechanisms, and product characteristics of MDD are well understood for uranium, corresponding studies of the neptunium system are still needed to continue optimization of target material properties, production equipment design, and production flowsheets. Here, the objective of this work is to characterize crystalline phases, morphology, surface texture, and particle size of NpO 2 produced via MDD reactions. Solid-phase characterization techniques, including powder X-ray diffraction (pXRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), were employed to achieve this objective. Subsequent data processing using the Morphological Analysis for Material Attribution (MAMA) software was performed to analyze particle morphology and size. Broadly, the powders were found to contain a mixture of NpO 2 and Np 2 O 5 after denitration with a variety of morphologies. After high-firing, the product was found to be NpO 2 with a typical polycrystalline oxide morphology and a grain size ranging from 0.72 to 0.94 µm. These analyses provide knowledge on the reaction pathway for a non-traditional NpO 2 synthesis method and offer additional unique insight into production-scale environments for transuranic materials.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2021

Maize tissue culture, transformation, and genome editing

The importance of maize (Zea mays L.) to global agriculture, world economy, and food security is widely known and increasing. Current maize breeding programs are deeply integrated with recent and rapid technological advances in genome sequencing, computational biology, and new genotyping and phenotyping technologies. Transformation and genome editing capabilities are a central hub to an array of advanced molecular and breeding approaches to crop improvement. Tissue culture and somatic embryogenesis play essential and central roles in maize transformation biology. Synergistic applications of maize transformation, advanced genomics, and genome editing provide a potent interdependent triad for functional genomics research and advanced molecular breeding. Implementation of advanced capabilities to transform maize and conduct genome editing will profoundly influence the dynamics of global agriculture ushering in a new era of varietal development and molecular breeding. With over 60.9 Mha planted in 2019 alone, biotech maize accounts for 31% of the world’s maize production. Up to 10% higher yields are achieved using new varieties generated using genetic modification technologies compared to similar conventional varieties. By extension, the impact new varietal releases developed through genome editing will likely be more significant. Further, advances in transformation and genome editing technologies will facilitate an even wider applicability for the development of new varieties with increasingly complex traits. The introduction of biochemical pathways and the use of synthetic biology have become increasingly more attainable. The future is of genotype independent maize transformation and genome editing, as the working platform will impact world agriculture, global food security, and plant science well into the future.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2013

Feedstock Supply System Design and Economics for Conversion of Lignocellulosic Biomass to Hydrocarbon Fuels

The U.S. Department of Energy promotes the production of a range of liquid fuels and fuel blendstocks from lignocellulosic biomass feedstocks by funding fundamental and applied research that advances the state of technology in biomass collection, conversion, and sustainability. As part of its involvement in this program, the Idaho National Laboratory (INL) investigates the feedstock logistics economics and sustainability of these fuels. Between 2000 and 2012, INL conducted a campaign to quantify the economics and sustainability of moving biomass from standing in the field or stand to the throat of the biomass conversion process. The goal of this program was to establish the current costs based on conventional equipment and processes, design improvements to the current system, and to mark annual improvements based on higher efficiencies or better designs. The 2012 programmatic target was to demonstrate a delivered biomass logistics cost of 35 USD/dry ton. This goal was successfully achieved in 2012 by implementing field and process demonstration unit-scale data from harvest, collection, storage, preprocessing, handling, and transportation operations into INL’s biomass logistics model. Looking forward to 2017, the programmatic target is to supply biomass to the conversion facilities at a total cost of 80 USD/dry ton and on specification with in-feed requirements. The goal of the 2017 Design Case is to enable expansion of biofuels production beyond highly productive resource areas by breaking the reliance of cost-competitive biofuel production on a single, abundant, low-cost feedstock. If this goal is not achieved, biofuel plants are destined to be small and/or clustered in select regions of the country that have a lock on low-cost feedstock. To put the 2017 cost target into perspective of past accomplishments of the cellulosic ethanol pathway, the 80 USD target encompasses total delivered feedstock cost, including both grower payment and logistics costs, while meeting all conversion in-feed quality targets. The 2012 35 USD programmatic target included only logistics costs with a limited focus on biomass quality

09 BIOMASS FUELS↗

DOE OSTI2015

Transition Analysis of Promising U.S. Future Fuel Cycles Using ORION

The US Department of Energy Office of Fuel Cycle Technologies performed an evaluation and screening (E&S) study of nuclear fuel cycle options to help prioritize future research and development decisions. Previous work for this E&S study focused on establishing equilibrium conditions for analysis examples of 40 nuclear fuel cycle evaluation groups (EGs) and evaluating their performance according to a set of 22 standardized metrics. Following the E&S study, additional studies are being conducted to assess transitioning from the current US fuel cycle to future fuel cycle options identified by the E&S study as being most promising. These studies help inform decisions on how to effectively achieve full transition, estimate the length of time needed to undergo transition from the current fuel cycle, and evaluate performance of nuclear systems and facilities in place during the transition. These studies also help identify any barriers to achieve transition. Oak Ridge National Laboratory (ORNL) Fuel Cycle Options Campaign team used ORION to analyze the transition pathway from the existing US nuclear fuel cycle—the once-through use of low-enriched-uranium (LEU) fuel in thermal-spectrum light water reactors (LWRs) —to a new fuel cycle with continuous recycling of plutonium and uranium in sodium fast reactors (SFRs). This paper discusses the analysis of the transition from an LWR to an SFR fleet using ORION, highlights the role of lifetime extensions of existing LWRs to aid transition, and discusses how a slight delay in SFR deployment can actually reduce the time to achieve an equilibrium fuel cycle.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2020

Challenges for and Pathways Toward Solid-State Batteries

Solid-state batteries utilizing lithium metal anodes have the potential to enable batteries with a specific energy of >500 Wh/kg and an energy density of >1,500 Wh/L for thousands of cycles. When optimized they will improve the energy efficiency, operating temperature range, sustainability, and safety at a lower cost compared to projections for advanced Li-ion batteries. This improved performance is critical for the widespread adoption of electric vehicles and may enable future applications such as electric aviation. Expectations for solid-state batteries are high, there are significant materials and processing challenges that need to be overcome. Some of these challenges are well known; others are more subtle and are just becoming known. The challenges and their solutions must be clearly identified to realize high-energy solid-state Li metal batteries. In the United States, the U.S. Department of Energy (DOE) funds the majority of energy storage research and development, including solid state battery research. Web of Science publication analysis shows that worldwide DOE is second largest funder. Work on solid state batteries is distributed across different arms of DOE and is coordinated at headquarters to ensure a broad national portfolio for advanced batteries, including lithium batteries and solid-state battery devices. We note that university and national laboratory researchers in the US with a long-standing interest in solid state batteries is a small, integrated community with recognized impact for publications, patents and startup companies. The opportunity for this group to engage for research with international colleagues is growing, fostered by periodic bilateral meetings supported by DOE and by the recent joint US German research program for lithium battery interface studies. These are valuable opportunities to speed solid-state battery development. The ORNL led virtual workshop, overviewed here, confirms the community’s shared vision of the exciting advances, opportunities, and challenges. Further, we are seeing that this workshop has spawned several new informal collaborations and draft proposals. This encourages us to propose future discussion. On May 11, 2020, Oak Ridge National Laboratory (ORNL) hosted a 6-hour, on-line national workshop to discuss recent advances and most the prominent obstacles to realizing solid-state Li metal batteries. The workshop included more than 30+ experts from national laboratories, universities, and companies, all of whom have worked on solid-state batteries for multiple years. The participants shared recent advances, many not yet in print, illustrating that the community has gained significant new insights for solid-state Li battery materials over the last 5 years. In this report, the major outcomes of the workshop are organized to identify the gaps in our scientific knowledge for four core materials science areas: (1) Li metal anodes, (2) the solid electrolyte in contact with Li metal, (3) active cathode materials and solid-state composite cathodes, and (4) solid electrolytes. Illustrative examples and discussions are reported with the more comprehensive issues in the report. Discussion of additional challenges related to processing of solid-state battery materials and to the designs and architectures for mechanically robust, long-lived batteries received less attention due to time constraints. These are good themes for deeper discussion at a follow-on workshop, where a complete list of critical research topics can be identified.

25 ENERGY STORAGE↗

DOE OSTI2025

CRCNS US-France Research Proposal: Collaborative Research: Encoding reward expectation in Drosophilia

The fruit fly Drosophila melanogaster has been a valuable model for investigating the genetic and neural bases that underlie learning and memory. Early and most current studies use basic behavior conditioning protocols to study learning in controlled laboratory settings. More recently, the ability to transgenically manipulate many of the brain neurons in the fruit fly with exquisite specificity, and the recent knowledge of the synaptic ‘connectome’ of the fruit fly brain, makes these animals almost unique as a comprehensive model for studies of learning, memory and motivated behavior. In fact, the connectome has revealed many types of new connections that had until now been overlooked. Within this context, the thesis of this proposal is that studies of learning and memory will be greatly enhanced by using more sophisticated means for evaluating memory representations, such as have been developed in vertebrates, and combining those studies with information from the connectome guided by computational modelling. We propose to push beyond the boundaries of existing conditioning protocols for fruit flies to investigate more complex memory representations. In particular, we will investigate the function of reinforcement pathways in relation to the absence of expected reinforcement. More specifically, we propose a series of experiments designed to investigate the memory representations in fruit flies when an expected consequence of a Conditioned Stimulus (CS) fails to occur. Although studies have evaluated how this failure can establish extinction memory for the CS, our studies will go beyond studying extinction. Specifically, we predict that in Drosophila when a CS is associated with a failed expectation of an appetitive food reinforcement it will acquire aversive value, and vice versa for a failed expectation of an aversive reinforcer. We combine these studies with manipulations of reinforcement pathways in the CNS inspired from the connectome, iteratively knitted in with established computational models. Intellectual Merit: The concept of reinforcement expectation and incentive contrast have been influential in the development of studies of associative learning in mammals. These questions are particularly challenging to answer in vertebrates because they require exquisite cellular, temporal, and genetic specificity of experimental manipulations. The recent development of work with identified neurons and their connectomes makes the larval and adult fly brains ripe as models for pushing our understanding of neural bases for these higher- order conditioning phenomena. Broader Impacts: Public health: These analyses and the conceptual framework of prediction error processing underlying them have a profound impact on our understanding of reinforcement-related behavior in humans, including monetary rewards and the mnemonic consequences of traumatic experiences, and for pathologies of the dopamine reinforcement system. Educational: This project will provide interdisciplinary training for postdoctoral researchers, Ph.D. and undergraduate students. The PIs will act as co-supervisors or mentors of students working in the different labs via face-to-face and internet-based technologies. We will also work with ASU’s award-winning Ask- A-Biologist program. This is an online science program designed to enrich the learning experiences of students of all ages and to provide classroom material for use by K-12 teachers. We will develop an extension of a game developed under a prior NSF award, and the new game will include modules to teach K-12 students about how insects learn. We will also integrate into the AAB site a program developed by a collaborator (B Gerber) at the Leibniz Institut für Neurobiologie, Magdeburg, and now in use in schools in Germany, to teach K-12 students how to train animals using the fruit fly larval learning paradigm. Underrepresented groups: All PIs will work with their university offices of Academic Diversity and Equal Opportunity for reaching underrepresented students.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

Genome-wide characterization of the soybean DOMAIN OF UNKNOWN FUNCTION 679 membrane protein gene family highlights their potential involvement in growth and stress response

The DMP (DUF679 membrane proteins) family is a plant-specific gene family that encodes membrane proteins. The DMP family genes are suggested to be involved in various programmed cell death processes and gamete fusion during double fertilization in Arabidopsis. However, their functional relevance in other crops remains unknown. This study identified 14 genes from the DMP family in soybean (Glycine max) and characterized their physiochemical properties, subcellular location, gene structure, and promoter regions using bioinformatics tools. Additionally, their tissue-specific and stress-responsive expressions were analyzed using publicly available transcriptome data. Phylogenetic analysis of 198 DMPs from monocots and dicots revealed six clades, with clade-I encoding senescence-related AtDMP1/2 orthologues and clade-II including pollen-specific AtDMP8/9 orthologues. The largest clade, clade-III, predominantly included monocot DMPs, while monocot- and dicot-specific DMPs were assembled in clade-IV and clade-VI, respectively. Evolutionary analysis suggests that soybean GmDMPs underwent purifying selection during evolution. Using 68 transcriptome datasets, expression profiling revealed expression in diverse tissues and distinct responses to abiotic and biotic stresses. The genes Glyma.09G237500 and Glyma.18G098300 showed pistil-abundant expression by qPCR, suggesting they could be potential targets for female organ-mediated haploid induction. Furthermore, cis-acting regulatory elements primarily related to stress-, hormone-, and light-induced pathways regulate GmDMPs, which is consistent with their divergent expression and suggests involvement in growth and stress responses. Overall, our study provides a comprehensive report on the soybean GmDMP family and a framework for further biological functional analysis of DMP genes in soybean or other crops.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1990

Gravitropism of cucumber hypocotyls: biophysical mechanism of altered growth

The biophysical basis for the changes in cell elongation rate during gravitropism was examined in aetiolated cucumber (Cucumis sativus L.) hypocotyls. Bulk osmotic pressures on the two sides of the stem and in the epidermal cells were not altered during the early time course of gravitropism. By the pressure-probe technique, a small increase in turgor (0.3 bar, 30 kPa) was detected on the upper (inhibited) side, whereas there was a negligible decrease in turgor on the lower (stimulated) side. These small changes in turgor and water potential appeared to be indirect, passive consequences of the altered growth and the small resistance for water movement from the xylem, and indicated that the change in growth was principally due to changes in wall properties. The results indicate that the hydraulic conductance of the water-transport pathway was large (.25 h-1 bar-1) and the water potential difference supporting cell expansion was no greater than 0.3 bar (30 kPa). From pressure-block experiments, it appeared that upon gravitropic stimulation (1) the yield threshold of the lower half of the stem did not decrease and (2) the wall on the upper side of the stem was not made more rigid by a cross-linking process. Mechanical measurements of the stress/strain properties of the walls showed that the initial development of gravitropism did not involve an alteration of the mechanical behaviour of the isolated walls. Thus, gravitropism in cucumber hypocotyls occurs principally by an alteration of the wall relaxation process, without a necessary change in wall mechanical properties.

Non-NASA Center↗

NASA NTRS1996

Light-modulated abundance of an mRNA encoding a calmodulin-regulated, chromatin-associated NTPase in pea

A CDNA encoding a 47 kDa nucleoside triphosphatase (NTPase) that is associated with the chromatin of pea nuclei has been cloned and sequenced. The translated sequence of the cDNA includes several domains predicted by known biochemical properties of the enzyme, including five motifs characteristic of the ATP-binding domain of many proteins, several potential casein kinase II phosphorylation sites, a helix-turn-helix region characteristic of DNA-binding proteins, and a potential calmodulin-binding domain. The deduced primary structure also includes an N-terminal sequence that is a predicted signal peptide and an internal sequence that could serve as a bipartite-type nuclear localization signal. Both in situ immunocytochemistry of pea plumules and immunoblots of purified cell fractions indicate that most of the immunodetectable NTPase is within the nucleus, a compartment proteins typically reach through nuclear pores rather than through the endoplasmic reticulum pathway. The translated sequence has some similarity to that of human lamin C, but not high enough to account for the earlier observation that IgG against human lamin C binds to the NTPase in immunoblots. Northern blot analysis shows that the NTPase MRNA is strongly expressed in etiolated plumules, but only poorly or not at all in the leaf and stem tissues of light-grown plants. Accumulation of NTPase mRNA in etiolated seedlings is stimulated by brief treatments with both red and far-red light, as is characteristic of very low-fluence phytochrome responses. Southern blotting with pea genomic DNA indicates the NTPase is likely to be encoded by a single gene.

NASA Discipline Number 40-50↗

DOE OSTI2022

H2@Scale Program Multi-Party Cooperative Research and Development Agreement: California Hydrogen Infrastructure Research Consortium Task (Cooperative Research and Development Final Report, CRADA Number CRD-18-00754)

Many stakeholders are working on hydrogen and fuel cell products, markets, requirements, mandates, and policies. California has been leading the way for hydrogen infrastructure and fuel cell electric vehicle (FCEV) deployment. This leadership has advanced a hydrogen network that is not duplicated anywhere in the United States and is unique in the world for its focus on providing a retail fueling experience. In addition, the advancements have identified many lessons learned for hydrogen infrastructure development, deployment, and operation. Other interested states and countries are using California's experience as a model case, making success in California paramount to enabling market acceleration and uptake in the United States. The technical research capability of the national laboratories can be used to assist California in decisions and evaluations, as well as to verify solutions to problems impacting the industry. Because these challenges cannot be addressed by one agency or one laboratory, a hydrogen research consortium has been organized to combine and collaborate. The collaboration aims to ensure that data are available to evaluate projects and inform decision makers, independently verify and validate component solutions, provide experimental results for future hydrogen infrastructure, increase the availability of technical experts for quick-need issues for California hydrogen infrastructure development, deployment, operation, and technology advances. The proposed tasks include data collection from operational stations, component failure fix verification (i.e. nozzle freeze lock), new fueling methods for medium and heavy duty applications, and ensuring hydrogen quality is maintained. U.S. leadership for hydrogen technologies is rooted in California, a location for implementing many H2@Scale pathways such as reducing curtailment and stranded resources, reducing petroleum use and emissions, and developing and creating jobs.

08 HYDROGEN↗

DOE OSTI2024

Post-translational modifications: emerging directors of cell-fate decisions during endoplasmic reticulum stress in Arabidopsis thaliana

Homeostasis of the endoplasmic reticulum (ER) is critical for growth, development, and stress responses. Perturbations causing an imbalance in ER proteostasis lead to a potentially lethal condition known as ER stress. In ER stress situations, cell-fate decisions either activate pro-life pathways that reestablish homeostasis or initiate pro-death pathways to prevent further damage to the organism. Understanding the mechanisms underpinning cell-fate decisions in ER stress is critical for crop development and has the potential to enable translation of conserved components to ER stress-related diseases in metazoans. Post-translational modifications (PTMs) of proteins are emerging as key players in cell-fate decisions in situations of imbalanced ER proteostasis. In this review, we address PTMs orchestrating cell-fate decisions in ER stress in plants and provide evidence-based perspectives for where future studies may focus to identify additional PTMs involved in ER stress management.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2020

Oxophilicity Drives Oxygen Transfer at a Palladium–Silver Interface for Increased CO Oxidation Activity

A single-layer AgO x phase grown on Ag(111) efficiently transfers oxygen to Pd domains at room temperature, rendering the Pd-decorated surface highly reactive toward CO oxidation. Here, oxygen transfer from AgO x to Pd and the surface reactivity toward CO were investigated as a function of the Pd coverage using X-ray photoelectron spectroscopy, surface infrared spectroscopy of adsorbed CO, temperature-programmed reaction spectroscopy, and density functional theory (DFT) calculations. Our results show that all of the oxygen from the AgO x layer (~0.375 monolayer) migrates to the surface of Pd during formation of a nearly complete Pd bilayer at 300 K and that the oxygen coverages generated on Pd increase as the Pd cluster size decreases, reaching values that exceed the oxygen concentration in the AgO x layer by as much as a factor of 2. Experimental measurements and DFT calculations show that preferential binding of oxygen on the edges of the Pd clusters enhances the oxygen coverage on Pd clusters of decreasing size and produces a heterogeneous spatial distribution of oxygen. CO adsorbs in high coverages at 100 K by binding on both the terraces and O-rich edges of the Pd clusters. During subsequent heating, oxidation of the adsorbed CO consumes nearly all of the oxygen that transferred from AgO x to the Pd domains; in contrast, the pure AgO x layer exhibits limited reactivity toward CO adsorbed at 100 K. These results demonstrate that differences in oxophilicity drive facile oxygen transfer from Ag to the edges of Pd nanoclusters and thereby give rise to an efficient pathway for CO oxidation on bimetallic PdAg surfaces. The cooperation between the Pd and Ag domains results in near-interfacial chemistry that may be broadly important in catalysis by bimetallic alloys.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1993

Calcium and signal transduction in plants

Environmental and hormonal signals control diverse physiological processes in plants. The mechanisms by which plant cells perceive and transduce these signals are poorly understood. Understanding biochemical and molecular events involved in signal transduction pathways has become one of the most active areas of plant research. Research during the last 15 years has established that Ca2+ acts as a messenger in transducing external signals. The evidence in support of Ca2+ as a messenger is unequivocal and fulfills all the requirements of a messenger. The role of Ca2+ becomes even more important because it is the only messenger known so far in plants. Since our last review on the Ca2+ messenger system in 1987, there has been tremendous progress in elucidating various aspects of Ca(2+) -signaling pathways in plants. These include demonstration of signal-induced changes in cytosolic Ca2+, calmodulin and calmodulin-like proteins, identification of different Ca2+ channels, characterization of Ca(2+) -dependent protein kinases (CDPKs) both at the biochemical and molecular levels, evidence for the presence of calmodulin-dependent protein kinases, and increased evidence in support of the role of inositol phospholipids in the Ca(2+) -signaling system. Despite the progress in Ca2+ research in plants, it is still in its infancy and much more needs to be done to understand the precise mechanisms by which Ca2+ regulates a wide variety of physiological processes. The purpose of this review is to summarize some of these recent developments in Ca2+ research as it relates to signal transduction in plants.

NASA Program Space Biology↗

NASA NTRS1990

Microsurgical removal of epidermal and cortical cells: evidence that the gravitropic signal moves through the outer cell layers in primary roots of maize

There is general agreement that during root gravitropism some sort of growth-modifying signal moves from the cap to the elongation zone and that this signal ultimately induces the curvature that leads to reorientation of the root. However, there is disagreement regarding both the nature of the signal and the pathway of its movement from the root cap to the elongation zone. We examined the pathway of movement by testing gravitropism in primary roots of maize (Zea mays L.) from which narrow (0.5 mm) rings of epidermal and cortical tissue were surgically removed from various positions within the elongation zone. When roots were girdled in the apical part of the elongation zone gravitropic curvature occurred apical to the girdle but not basal to the girdle. Filling the girdle with agar allowed curvature basal to the girdle to occur. Shallow girdles, in which only two or three cell layers (epidermis plus one or two cortical cell layers) were removed, prevented or greatly delayed gravitropic curvature basal to the girdle. The results indicate that the gravitropic signal moves basipetally through the outermost cell layers, perhaps through the epidermis itself.

NASA Discipline Number 29-20↗

DOE OSTI2018

Outbreak investigations of foot and mouth disease virus in Nepal between 2010 and 2015 in the context of historical serotype occurrence

Abstract Foot and Mouth Disease ( FMD ) is endemic in Nepal and causes substantial economic losses in the livestock industry. The goal of this study was to perform an epidemiological analysis of FMD outbreaks reported to the Veterinary Epidemiology Center, Tripureshwor, Nepal during 2010–2015, in order to strengthen the National FMD Control Program. These current data were considered in the context of historical data on FMD virus ( FMDV ) serotypes detected in the country between 1965 and 2015. During 2010–2015, a total of 1333 livestock holdings reported FMD outbreaks in Nepal. On average, 71.2 animals were affected in each outbreak, with a case fatality rate of 3.6%. FMD was reported throughout the country, and the proportion of affected holdings was not significantly among eco‐zones, regions, or species. The Hill eco‐zone had the highest number of holdings affected (782), followed by Mountain (304), and Terai (247). When analysed by the developmental region, the Western (381) and Central (368) Developmental Regions had the highest numbers of holdings affected. Cattle were the most frequently affected species (39%), followed by buffalo (33%), and goats (19%). FMD occurred throughout the year, with peaks in winter (December/January) and in the pre‐monsoon period (April/May). Between 1965 and 2015 FMDV serotype O had the highest prevalence (81%), followed by Asia‐1 (11%), A (6%), and C (2%). Serotype C was not detected after 1996, and only serotype O was reported after 2011. These descriptive analyses provide critical landmarks to establish baselines, and document early progress of the ongoing Progressive Control Pathway of FMD ( PCP ‐ FMD ) which could be useful in Nepal and other South Asian nations.

59 BASIC BIOLOGICAL SCIENCES↗