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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Advances in Cell Wall Matrix Research with a Focus on Mixed-Linkage Glucan

Mixed β(1,3;1,4)-linkage glucan (MLG) is commonly found in the monocot lineage, at particularly high levels in the Poaceae family, but also in the evolutionally distant genus, Equisetum. MLG has several properties that make it unique from other plant cell wall polysaccharides. It consists of β1,4-linked polymers of glucose interspersed with β1,3-linkages, but the presence of β1,3-linkages provides quite different physical properties compared to its closest form of the cell wall component, cellulose. The mechanisms of MLG biosynthesis have been investigated to understand whether single or multiple enzymes are required to build mixed linkages in the glucan chain. Currently, MLG synthesis by a single enzyme is supported by mutagenesis analyses of cellulose synthase-like F6, the major MLG synthase, but further investigation is needed to gather mechanistic insights. Because of transient accumulation of MLG in elongating cells and vegetative tissues, several hypotheses have been proposed to explain the role of MLG in the plant cell wall. Studies have been carried out to identify gene expression regulators during development and light cycles as well as enzymes involved in MLG organization in the cell wall. A role of MLG as a storage molecule in grains is evident, but the role of MLG in vegetative tissues is still not well understood. Characterization of a cell wall component is difficult due to the complex heterogeneity of the plant cell wall. Furthermore, as detailed in this review, recent exciting research has made significant impacts in the understanding of MLG biology in plants.

Transglucosylase/hydrolase (XTH)↗
NASA NTRS1994

Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L

In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, alpha-actin, alpha-tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin-related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express.

Non-NASA Center↗
DOE OSTI2024

Plant Cell Wall Loosening by Expansins

Expansins comprise an ancient group of cell wall proteins ubiquitous in land plants and their algal ancestors. During cell growth, they facilitate passive yielding of the wall's cellulose networks to turgor-generated tensile stresses, without evidence of enzymatic activity. Expansins are also implicated in fruit softening and other developmental processes and in adaptive responses to environmental stresses and pathogens. The major expansin families in plants include α-expansins (EXPAs), which act on cellulose-cellulose junctions, and β-expansins, which can act on xylans. EXPAs mediate acid growth, which contributes to wall enlargement by auxin and other growth agents. The genomes of diverse microbes, including many plant pathogens, also encode expansins designated expansin-like X. Expansins are proposed to disrupt noncovalent bonding between laterally aligned polysaccharides (notably cellulose), facilitating wall loosening for a variety of biological roles.

Cell Biology↗
DOE OSTI2022

Structure of the divergent human astrovirus MLB capsid spike

Despite their worldwide prevalence and association with human disease, the molecular bases of human astrovirus (HAstV) infection and evolution remain poorly characterized. Here, we report the structure of the capsid protein spike of the divergent HAstV MLB clade (HAstV MLB). While the structure shares a similar folding topology with that of classical-clade HAstV spikes, it is otherwise strikingly different. We find no evidence of a conserved receptor-binding site between the MLB and classical HAstV spikes, suggesting that MLB and classical HAstVs utilize different receptors for host-cell attachment. We provide evidence for this hypothesis using a novel HAstV infection competition assay. Comparisons of the HAstV MLB spike structure with structures predicted from its sequence reveal poor matches, but template-based predictions were surprisingly accurate relative to machine-learning-based predictions. Our data provide a foundation for understanding the mechanisms of infection by diverse HAstVs and can support structure determination in similarly unstudied systems.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2002

In vitro cell irradiation systems based on 210Po alpha source: construction and characterisation

One way of studying the risk to human health of low-level radiation exposure is to make biological experiments on living cell cultures. Two 210Po alpha-particle emitting devices, with 0.5 and 100 MBq activity, were designed and constructed to perform such experiments irradiating monolayers of cells. Estimates of dose rate at the cell surface were obtained from measurements by a PIPS alpha-particle spectrometer and from calculations by the SRIM 2000, Monte Carlo charged particle transport code. Particle fluence area distributions were measured by solid state nuclear track detectors. The design and dosimetric characterisation of the devices are discussed. c2002 Elsevier Science Ltd. All rights reserved.

Alpha Particles↗
DOE OSTI2022

Dynamics of pectic homogalacturonan in cellular morphogenesis and adhesion, wall integrity sensing and plant development

Homogalacturonan (HG) is the most abundant pectin subtype in plant cell walls. Although it is a linear homopolymer, its modification states allow for complex molecular encoding. HG metabolism affects its structure, chemical properties, mobility and binding capacity, allowing it to interact dynamically with other polymers during wall assembly and remodelling and to facilitate anisotropic cell growth, cell adhesion and separation, and organ morphogenesis. HGs have also recently been found to function as signalling molecules that transmit information about wall integrity to the cell. Here we highlight recent advances in our understanding of the dual functions of HG as a dynamic structural component of the cell wall and an initiator of intrinsic and environmental signalling. Here, we also predict how HG might interconnect the cell wall, plasma membrane and intracellular components with transcriptional networks to regulate plant growth and development.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1992

Is receptor oligomerization causally linked to activation of the EGF receptor kinase?

Transduction of a signal from an extracellular peptide hormone to produce an intracellular response is often mediated by a cell surface receptor, which is usually a glycoprotein. The secondary intracellular signal(s) generated after hormone binding to the receptor have been intensively studied. The nature of the primary signal generated by ligand binding to the receptor is understood less well in most cases. The particular case of the epidermal growth factor (EGF) receptor is analyzed, and evidence for or against two dissimilar models of primary signal transduction is reviewed. Evidence for the most widely accepted current model is found to be unconvincing. Evidence for the other model is substantial but indirect; a direct test of this model remains to be done.

Non-NASA Center↗
DOE OSTI2024

Structural basis of selective TRPM7 inhibition by the anticancer agent CCT128930

TRP channels are implicated in various diseases, but high structural similarity between them makes selective pharmacological modulation challenging. Here, we study the molecular mechanism underlying specific inhibition of the TRPM7 channel, which is essential for cancer cell proliferation, by the anticancer agent CCT128930 (CCT). Using cryo-EM, functional analysis, and MD simulations, we show that CCT binds to a vanilloid-like (VL) site, stabilizing TRPM7 in the closed non-conducting state. Similar to other allosteric inhibitors of TRPM7, NS8593 and VER155008, binding of CCT is accompanied by displacement of a lipid that resides in the VL site in the apo condition. Moreover, we demonstrate the principal role of several residues in the VL site enabling CCT to inhibit TRPM7 without impacting the homologous TRPM6 channel. Hence, our results uncover the central role of the VL site for the selective interaction of TRPM7 with small molecules that can be explored in future drug design.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

FTO regulates myoblast proliferation by controlling CCND1 expression in an m6A-YTHDF2-dependent manner

Highlights: • Silencing FTO delays cell cycle and inhibits cell proliferation. • FTO regulates cell proliferation depending on its m{sup 6}A demethylation activity. • Silencing FTO suppresses CCND1 expression via YTHDF2-mediated mRNA degradation. • Knockdown YTHDF2 eliminates the cell cycle arrest in FTO-deficient cells. N6-Methyladenosine (m{sup 6}A) modification is the most abundant chemical modification in mRNA, and it participates in various biological processes, such as cell differentiation and proliferation. However, little is known about the function of m{sup 6}A demethylase fat mass and obesity-associated (FTO) in myoblast proliferation. Here, we demonstrated that knockdown of FTO can significantly inhibit myoblast proliferation and promote apoptosis. RNA sequencing analysis revealed that a lot of downregulated genes in FTO knockdown cells are associated with cell cycle and apoptosis. Furthermore, silencing FTO drastically decreased cyclin D1 (CCND1) expression through YTHDF2-mediated mRNA degradation, thereby delaying the progression of G1 phase, and leading to impaired myoblast proliferation. These findings unraveled that FTO regulates myoblast proliferation by controlling CCND1 expression in an m{sup 6}A-YTHDF2-dependent manner, which highlights the critical roles of m{sup 6}A modification in myoblast proliferation.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1996

Space Station Biological Research Project: Reference Experiment Book

The Space Station Biological Research Project (SSBRP), which is the combined efforts of the Centrifuge Facility (CF) and the Gravitational Biology Facility (GBF), is responsible for the development of life sciences hardware to be used on the International Space Station to support cell, developmental, and plant biology research. The SSBRP Reference Experiment Book was developed to use as a tool for guiding this development effort. The reference experiments characterize the research interests of the international scientific community and serve to identify the hardware capabilities and support equipment needed to support such research. The reference experiments also serve as a tool for understanding the operational aspects of conducting research on board the Space Station. This material was generated by the science community by way of their responses to reference experiment solicitation packages sent to them by SSBRP scientists. The solicitation process was executed in two phases. The first phase was completed in February of 1992 and the second phase completed in November of 1995. Representing these phases, the document is subdivided into a Section 1 and a Section 2. The reference experiments contained in this document are only representative microgravity experiments. They are not intended to define actual flight experiments. Ground and flight experiments will be selected through the formal NASA Research Announcement (NRA) and Announcement of Opportunity (AO) experiment solicitation, review, and selection process.

Johnson, Catherine↗
NASA NTRS1991

Altered cell function in microgravity

The paper overviews published results from investigations of changes in basic biological parameters taking place as a result of spaceflight exposure. These include changes in the rates of the DNA, mRNA, and protein biosyntheses; changes in the growth rate of an organism; and alterations in the cytoskeleton structure, differentiation, hormone accumulation, and collagen matrix secretion. These results, obtained both in complex biological organisms and on cultured cells, suggest that a basic cellular function is influenced and changed by microgravity. Many of the above mentioned changes are also found to take place in aging cells.

Hughes-Fulford, Millie↗
DOE OSTI2020

NMT1 and NMT2 are lysine myristoyltransferases regulating the ARF6 GTPase cycle

Abstract Lysine fatty acylation in mammalian cells was discovered nearly three decades ago, yet the enzymes catalyzing it remain unknown. Unexpectedly, we find that human N-terminal glycine myristoyltransferases (NMT) 1 and 2 can efficiently myristoylate specific lysine residues. They modify ADP-ribosylation factor 6 (ARF6) on lysine 3 allowing it to remain on membranes during the GTPase cycle. We demonstrate that the NAD + -dependent deacylase SIRT2 removes the myristoyl group, and our evidence suggests that NMT prefers the GTP-bound while SIRT2 prefers the GDP-bound ARF6. This allows the lysine myrisotylation-demyristoylation cycle to couple to and promote the GTPase cycle of ARF6. Our study provides an explanation for the puzzling dissimilarity of ARF6 to other ARFs and suggests the existence of other substrates regulated by this previously unknown function of NMT. Furthermore, we identified a NMT/SIRT2-ARF6 regulatory axis, which may offer new ways to treat human diseases.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2015

Modeling the Effects of Spaceflight on the Posterior Eye in VIIP

Purpose: Visual Impairment and Intracranial Pressure (VIIP) syndrome is a new and significant health concern for long-duration space missions. Its etiology is unknown, but is thought to involve elevated intracranial pressure (ICP)that induces connective tissue changes and remodeling in the posterior eye (Alexander et al. 2012). Here we study the acute biomechanical response of the lamina cribrosa (LC) and optic nerve to elevations in ICP utilizing finite element (FE) modeling. Methods: Using the geometry of the posterior eye from previous axisymmetric FE models (Sigal et al. 2004), we added an elongated optic nerve and optic nerve sheath, including the pia and dura. Tissues were modeled as linear elastic solids. Intraocular pressure and central retinal vessel pressures were set at 15 mmHg and 55 mmHg, respectively. ICP varied from 0 mmHg (suitable for standing on earth) to 30 mmHg (representing severe intracranial hypertension, thought to occur in space flight). We focused on strains and deformations in the LC and optic nerve (within 1 mm of the LC) since we hypothesize that they may contribute to vision loss in VIIP. Results: Elevating ICP from 0 to 30 mmHg significantly altered the strain distributions in both the LC and optic nerve (Figure), notably leading to more extreme strain values in both tension and compression. Specifically, the extreme (95th percentile) tensile strains in the LC and optic nerve increased by 2.7- and 3.8-fold, respectively. Similarly, elevation of ICP led to a 2.5- and 3.3-fold increase in extreme (5th percentile) compressive strains in the LC and optic nerve, respectively. Conclusions: The elevated ICP thought to occur during spaceflight leads to large acute changes in the biomechanical environment of the LC and optic nerve, and we hypothesize that such changes can activate mechanosensitive cells and invoke tissue remodeling. These simulations provide a foundation for more comprehensive studies of microgravity effects on human vision, e.g. to guide biological studies in which cells and tissues are mechanically loaded in a ranger elevant for microgravity conditions.

gravitational physiology↗
NASA NTRS1994

Space shuttle flight (STS-45) of L8 myoblast cells results in the isolation of a nonfusing cell line variant

Myoblast cell cultures have been widely employed in conventional (1g) studies of biological processes because characteristics of intact muscle can be readily observed in these cultured cells. We decided to investigate the effects of spaceflight on muscle by utilizing a well characterized myoblast cell line (L8 rat myoblasts) as cultured in the recently designed Space Tissue Loss Flight Module "A" (STL-A). The STL-A is a "state of the art," compact, fully contained, automated cell culture apparatus which replaces a single mid-deck locker on the Space Shuttle. The L8 cells were successfully flown in the STL-A on the Space Shuttle STS-45 mission. Upon return to earth, reculturing of these spaceflown L8 cells (L8SF) resulted in their unexpected failure to fuse and differentiate into myotubes. This inability of the L8SF cells to fuse was found to be a permanent phenotypic alteration. Scanning electron microscopic examination of L8SF cells growing at 1g on fibronectin-coated polypropylene fibers exhibited a strikingly different morphology as compared to control cells. In addition to their failure to fuse into myotubes, L8SF cells also piled up on top of each other. When assayed in fusion-promoting soft agar, L8SF cells gave rise to substantially more and larger colonies than did either preflight (L8AT) or ground control (L8GC) cells. All data to this point indicate that flying L8 rat myoblasts on the Space Shuttle for a duration of 7-10 d at subconfluent densities results in several permanent phenotypic alterations in these cells.

STS-45 Shuttle Project↗
DOE OSTI2022

Real-time bioelectronic sensing of environmental contaminants

Real-time chemical sensing is crucial for applications in environmental and health monitoring. Biosensors can detect a variety of molecules through genetic circuits that use these chemicals to trigger the synthesis of a coloured protein, thereby producing an optical signal. However, the process of protein expression limits the speed of this sensing to approximately half an hour, and optical signals are often difficult to detect in situ. Here we combine synthetic biology and materials engineering to develop biosensors that produce electrical readouts and have detection times of minutes. Here we programmed Escherichia coli to produce an electrical current in response to specific chemicals using a modular, eight-component, synthetic electron transport chain. As designed, this strain produced current following exposure to thiosulfate, an anion that causes microbial blooms, within 2 min. This amperometric sensor was then modified to detect an endocrine disruptor. The incorporation of a protein switch into the synthetic pathway and encapsulation of the bacteria with conductive nanomaterials enabled the detection of the endocrine disruptor in urban waterway samples within 3 min. Our results provide design rules to sense various chemicals with mass-transport-limited detection times and a new platform for miniature, low-power bioelectronic sensors that safeguard ecological and human health.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Single-cell proteomics of Arabidopsis leaf mesophyll reveals dynamic protein responses to water-deficit stress

Background The application of single-cell omics tools to biological systems can provide unique insights into diverse cellular populations and their heterogeneous responses to internal and external perturbations. Thus far, most single-cell studies in plant systems have been limited to RNA-sequencing approaches, which only provide indirect readouts of cellular functions. Results Here, we present a single-cell proteomics workflow for plant cells that integrates tape-sandwich protoplasting, piezoelectric cell sorting, nanoPOTS sample preparation, and ion mobility-based MS data acquisition method for label-free single-cell proteomics analysis of Arabidopsis leaf mesophyll cells. From a single leaf protoplast, over 3,000 proteins were quantified with high precision. The workflow is demonstrated to identify stress associated changes in protein abundance by analyzing 117 protoplasts from well-watered and water-deficit stressed plants. Additionally, we describe a new approach for constructing covarying protein networks at the single-cell level and demonstrate how single-cell protein covariation analysis can reveal previously unrecognized protein functions while also capturing stress-induced changes in protein–protein dynamics. Conclusions The label-free scProteomic approach presented here represents a significant advance through the demonstration of a facile protoplast isolation method combined with deep and precise proteomic coverage of Arabidopsis leaf mesophyll cell types. We believe this study will serve as an informative reference to future plant scProteomic investigations.

Arabidopsis↗
NASA NTRS1987

Proton gradients in intact cyanobacteria

The internal pH values of two unicellular cyanobacterial strains were determined with electron spin resonance probes, over an external pH range of 6 to 9, in the light and in the dark. The slow growing, thylakoid-lacking Gloeobacter violaceus was found to have a low capacity for maintaining a constant internal pH. The distribution pattern of weak acid and amine nitroxide spin probes across the cell membranes of this organism, in the light and in the dark, was consistent with the assumption that it contains a single intracellular compartment. At an external pH of 7.0, intracellular pH was 6.8 in the dark and 7.2 in the light. The cells of Agmenellum quadruplicatum, a marine species, were found to contain two separate compartments; in the dark, the pH of the cytoplasmic and the intrathylakoid spaces were calculated to be 7.2 and 5.5, respectively. Upon illumination, the former increased and the latter decreased by about 0.5 pH units.

Non-NASA Center↗