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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 OSTI2020

Microwave‐assisted hydrodistillation of the essential oil from Algerian Pimpinella anisum seeds

Abstract Essential oils (EOs) from anise seeds ( Pimpinella anisum ) collected in the Algerian region were extracted by microwave‐assisted hydrodistillation (MAHD) and hydrodistillation (HD). The oil yield (%), chemical composition, energetic consumption and the antimicrobial properties were evaluated of the obtained EO. The yields obtained by both processes were 2.81 ± 0.01% for 90 minutes and 3.30 ± 0.05% for 330 minutes for MAHD and HD, respectively. The determination of the chemical composition of EOs by GC‐MS revealed the presence of a majority compound, trans ‐anethole 81.52% and 91.31% for MAHD and HD, respectively. The other main compounds present in the oils for MAHD and HD were, respectively: methyl chavicol (estragole) (0.63%‐1.39%), cis ‐anethole (0.23%‐0.34%), anisaldehyde (1.1%‐1.57%), anisyl methyl ketone (0.28%‐0.13%), trans ‐methyl isoellgenol (0.31%‐0.17%), γ ‐himachalene (0.5%‐0.36%), trans ‐pseudoisoeugenyl 2‐methylbutyrate (6.53%‐2.53%) and epoxy‐pseudoisoeugenyl 2‐methylbutyrate (2.01%‐0.56%). The EO obtained by MAHD detected other compounds, fenchone 0.41%, limonene 0.68%, cis ‐jasmolacatone extra C 0.41%, trans ‐isolongifolanone 0.2% and α ‐himachalene 0.16%. The energetic consumption by MAHD was significantly less than HD. Theoretical data from mathematical modelling were compared with practical data, and the coefficient of determination was between 0.93 and 0.97. The sensibility of bacterial strains to the essential oil obtained by MAHD is marked relatively to that obtained by HD, and for the sensibility of fungal strains, it was conserved. The MAHD process revealed a good yield of anise seeds EOs while reducing extraction time and energetic consumption. The EO extracted by this process revealed the presence of other compounds while improving antibacterial activity.

Boumahdi, Yamina↗
DOE OSTI2023

Characterization of promoter elements of isoprene‐responsive genes and the ability of isoprene to bind START domain transcription factors

Abstract Isoprene has recently been proposed to be a signaling molecule that can enhance tolerance of both biotic and abiotic stress. Not all plants make isoprene, but all plants tested to date respond to isoprene. We hypothesized that isoprene interacts with existing signaling pathways rather than requiring novel mechanisms for its effect on plants. We analyzed the cis‐regulatory elements (CREs) in promoters of isoprene‐responsive genes and the corresponding transcription factors binding these promoter elements to obtain clues about the transcription factors and other proteins involved in isoprene signaling. Promoter regions of isoprene‐responsive genes were characterized using the Arabidopsis cis‐regulatory element database. CREs bind ARR1, Dof, DPBF, bHLH112, GATA factors, GT‐1, MYB, and WRKY transcription factors, and light‐responsive elements were overrepresented in promoters of isoprene‐responsive genes; CBF‐, HSF‐, WUS‐binding motifs were underrepresented. Transcription factors corresponding to CREs overrepresented in promoters of isoprene‐responsive genes were mainly those important for stress responses: drought‐, salt/osmotic‐, oxidative‐, herbivory/wounding and pathogen‐stress. More than half of the isoprene‐responsive genes contained at least one binding site for TFs of the class IV (homeodomain leucine zipper) HD‐ZIP family, such as GL2, ATML1, PDF2, HDG11, ATHB17. While the HD‐zipper‐loop‐zipper (ZLZ) domain binds to the L1 box of the promoter region, a special domain called the steroidogenic acute regulatory protein‐related lipid transfer, or START domain, can bind ligands such as fatty acids (e.g., linolenic and linoleic acid). We tested whether isoprene might bind in such a START domain. Molecular simulations and modeling to test interactions between isoprene and a class IV HD‐ZIP family START‐domain‐containing protein were carried out. Without membrane penetration by the HDG11 START domain, isoprene within the lipid bilayer was inaccessible to this domain, preventing protein interactions with membrane bound isoprene. The cross‐talk between isoprene‐mediated signaling and other growth regulator and stress signaling pathways, in terms of common CREs and transcription factors could enhance the stability of the isoprene emission trait when it evolves in a plant but so far it has not been possible to say what how isoprene is sensed to initiate signaling responses.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Design, synthesis and biological evaluation of some novel diastereoselective β-lactams bearing 2-mercaptobenzothiazole and benzoquinoline

We report the synthesis of some novel β-lactam hybrids of 2-mercaptobenzothiazole and benzoquinoline. These compounds were synthesized by a [2 + 2]-cycloaddition reaction of imines 8a-d and ketenes derived from substituted acetic acids. The reaction was totally diastereoselective leading exclusively to the formation of cis-β-lactams 10a-m. All products were obtained in good to excellent yields and their structures were established based on IR, {sup 1}H NMR, {sup 13}C NMR spectral data and elemental analysis. Schiff bases 8a-d and β-lactam hybrids 10a-m were evaluated for antimicrobial activities against six bacterial species. The minimum inhibitory concentration (MIC) values indicate that two of the β-lactams, 10k and 10m, have good activities against the two Gram-negative bacteria, E. coli and P. aeruginosa, while three of the Schiff bases, 8a-c, are active against P. aeruginosa and the Gram-positive pathogen S. aureus. The molecular and cellular basis for these observed antibacterial properties are not determined. Moreover, the five most active compounds showed acceptably low cytotoxicity (less than 25% cell growth inhibition after 72 h of incubation) against the MCF-7 cell line, and below 10% in vitro hemolytic activity at 50 and 200 µM concentrations. These results suggest a need for further inquiry into the reason for why these compounds are bioactive, and as to what their full biological activities and antibiotic potential may be. The cis stereochemistry of β-lactam 10a was confirmed by X-ray crystallographic studies.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Early Stage Hepatocellular Carcinomas Not Feasible for Ultrasound-Guided Radiofrequency Ablation: Comparison of Transarterial Chemoembolization Alone and Combined Therapy with Transarterial Chemoembolization and Radiofrequency Ablation

PurposeTo report the results of combined therapy with transarterial chemoembolization (TACE) and radiofrequency ablation (RFA) for early stage hepatocellular carcinoma (HCC) considered infeasible for ultrasound (US)-guided RFA in comparison with those of TACE monotherapy.MethodsFrom January 2007 through December 2010, 91 patients with early or very early stage HCC infeasible for US-guided RFA received either TACE alone (TACE group; n = 54) or TACE immediately followed by RFA (TACE–RFA group; n = 37) as a first-line treatment. 1-month tumor response, time to progression (TTP), and overall survival (OS) rates were calculated. Univariate and multivariate analyses were performed to identify prognostic factors.ResultsTACE–RFA group showed a better 1-month tumor response than TACE group (P < .001). The mean TTP was 29.7 ± 3.4 months (95 % confidence intervals [CIs] 23.0–36.5) in TACE group and 34.9 ± 2.8 months (95 % CIs 29.4–40.4) in TACE–RFA group. TACE–RFA group had a significantly longer TTP (P = .014). Cumulative 1-, 2-, and 3-year OS rates in the TACE and TACE–RFA groups were 91, 79, and 71 % and 100, 97, and 93 %, respectively (P = .008). Initial treatment of TACE was found to be the only significant risk factor for tumor progression and OS in multivariate analysis.ConclusionTACE–RFA combination therapy appears superior to TACE monotherapy in terms of 1-month tumor response, TTP, and OS when performed for early stage HCC infeasible for US-guided RFA.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

The SEEL motif and members of the MYB-related REVEILLE transcription factor family are important for the expression of LORELEI in the synergid cells of the Arabidopsis female gametophyte

Synergid cells in the micropylar end of the female gametophyte are required for critical cell–cell signaling interactions between the pollen tube and the ovule that precede double fertilization and seed formation in flowering plants. LORELEI (LRE) encodes a putative GPI-anchored protein that is expressed primarily in the synergid cells, and together with FERONIA, a receptor-like kinase, it controls pollen tube reception by the receptive synergid cell. Still, how LRE expression is controlled in synergid cells remains poorly characterized. We identified candidate cis-regulatory elements enriched in LRE and other synergid cell-expressed genes. One of the candidate motifs (‘TAATATCT’) in the LRE promoter was an uncharacterized variant of the Evening Element motif that we named as the Short Evening Element-like (SEEL) motif. Deletion or point mutations in the SEEL motif of the LRE promoter resulted in decreased reporter expression in synergid cells, demonstrating that the SEEL motif is important for expression of LRE in synergid cells. Additionally, we found that LRE expression is decreased in the loss of function mutants of REVEILLE (RVE) transcription factors, which are clock genes known to bind the SEEL and other closely related motifs. Here, we propose that RVE transcription factors regulate LRE expression in synergid cells by binding to the SEEL motif in the LRE promoter. Identification of cis-regulatory elements and transcription factors involved in the expression of LRE will serve as a foundation to characterize the gene regulatory networks in synergid cells.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Bias Voltage-Dependent Impedance Spectroscopy Analysis of Hydrothermally Synthesized ZnS Nanoparticles

In this report, bias voltage-dependent dielectric and electron transport properties of ZnS nanoparticles were discussed. ZnS nanoparticles were synthesized by introducing a modified hydrothermal process. The powder XRD pattern indicates the phase purity, and field emission scanning electron microscope image demonstrates the morphology of the synthesized sample. The optical band gap energy (E{sub g }= 4.2 eV) from UV measurement explores semiconductor behavior of the synthesized material. The electrical properties were performed at room temperature using complex impedance spectroscopy (CIS) technique as a function of frequency (40 Hz-10 MHz) under different forward dc bias voltages (0-1 V). The CIS analysis demonstrates the contribution of bulk resistance in conduction mechanism and its dependency on forward dc bias voltages. The imaginary part of the impedance versus frequency curve exhibits the existence of relaxation peak which shifts with increasing dc forward bias voltages. The dc bias voltage-dependent ac and dc conductivity of the synthesized ZnS was studied on thin film structure. A possible hopping mechanism for electrical transport processes in the system was investigated. Finally, it is worth to mention that this analysis of bias voltage-dependent dielectric and transport properties of as-synthesized ZnS showed excellent properties for emerging energy applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Functional analysis of the rice rubisco activase promoter in transgenic Arabidopsis

Highlights: Black-Right-Pointing-Pointer Rice rubisco activase promoter was analyzed in transgenic Arabidopsis system. Black-Right-Pointing-Pointer Region conferring tissue specific and light inducible expression of Rca was identified. Black-Right-Pointing-Pointer -58 to +43 bp region mediates tissue-specific expression of rice Rca. Black-Right-Pointing-Pointer Light inducible expression of rice Rca is mediated by -297 to -58 bp region. Black-Right-Pointing-Pointer Rice nuclear proteins bind specifically with the light inducible region. -- Abstract: To gain a better understanding of the regulatory mechanism of the rice rubisco activase (Rca) gene, variants of the Rca gene promoter (one full-length and four deletion mutants) fused to the coding region of the bacterial reporter gene {beta}-glucuronidase (GUS) were introduced into Arabidopsis via Agrobacterium-mediated transformation. Our results show that a 340 bp fragment spanning from -297 to +43 bp relative to the transcription initiation site is enough to promote tissue-specific and light-inducible expression of the rice Rca gene as done by the full-length promoter (-1428 to +43 bp). Further deletion analysis indicated that the region conferring tissue-specificity of Rca expression is localized within a 105 bp fragment from -58 to +43 bp, while light-inducible expression of Rca is mediated by the region from -297 to -58 bp. Gel shift assays and competition experiments demonstrated that rice nuclear proteins bind specifically with the fragment conferring light responsiveness at more than one binding site. This implies that multiple cis-elements may be involved in light-induced expression of the rice Rca gene. These works provide a useful reference for understanding transcriptional regulation mechanism of the rice Rca gene, and lay a strong foundation for further detection of related cis-elements and trans-factors.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

24-Methylenecycloartanyl ferulate, a major compound of γ-oryzanol, promotes parvin-beta expression through an interaction with peroxisome proliferator-activated receptor-gamma 2 in human breast cancer cells

Parvin-β is an adaptor protein that binds to integrin-linked kinase (ILK) and is significantly downregulated in breast tumors and breast cancer cell lines. We treated the breast cancer cell line MCF7 with 24-methylenecycloartanyl ferulate (24-MCF), a γ-oryzanol compound. We observed upregulation of parvin-β (GenBank Accession No. (AF237769)) and peroxisome proliferator-activated receptor (PPAR)-γ2 (GenBank Accession No. (NM-015869)). Among γ-oryzanol compounds, only treatment with 24-MCF led to the formation of reverse transcription-PCR products of parvin-β (650 and 500 bp) and PPAR-γ2 (580 bp) in MCF7 cells, but not in T47D, SK-BR-3, or MDA-MB-231 cells. 24-MCF treatment increased the mRNA and protein levels of parvin-β in MCF7 cells in a dose-dependent manner. We hypothesized that there is a correlation between parvin-β expression and induction of PPAR-γ2. This hypothesis was investigated by using a promoter-reporter assay, chromatin immunoprecipitation, and an electrophoretic mobility shift assay. 24-MCF treatment induced binding of PPAR-γ2 to a peroxisome proliferator response element-like cis-element (ACTAGGACAAAGGACA) in the parvin-β promoter in MCF7 cells in a dose-dependent manner. 24-MCF treatment significantly decreased anchorage-independent growth and inhibited cell movement in comparison to control treatment with dimethyl sulfoxide. 24-MCF treatment reduced the levels of GTP-bound Rac1 and Cdc42. Evaluation of Akt1 inhibition by 24-MCF revealed that the half maximal effective concentration was 33.3 μM. Docking evaluations revealed that 24-MCF binds to the ATP-binding site of Akt1(PDB ID: (3OCB)) and the compound binding energy is -8.870 kcal/mol. Taken together, our results indicate that 24-MCF treatment increases parvin-β expression, which may inhibit ILK downstream signaling. - Highlights: • Treatment with 24-MCF increases gene expression of parvin-β and PPAR-ϒ2 in MCF7 cells. • PPAR-ϒ2 interacts with the parvin-β gene via its peroxisome proliferator response element-like cis-element. • 24-MCF treatment inhibits anchorage-dependent growth of MCF7 cells. • 24-MCF treatment inhibits MCF7 cell migration and Rac1 and Cdc42 activation. • 24-MCF may be a new ATP-competitive Akt1 inhibitor that binds to the ATP-binding site of Akt1.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Understanding the molecular mechanisms of reprogramming

Despite the profound and rapid advancements in reprogramming technologies since the generation of the first induced pluripotent stem cells (iPSCs) in 2006[1], the molecular basics of the process and its implications are still not fully understood. Recent work has suggested that a subset of TFs, so called “Pioneer TFs”, play an important role during the stochastic phase of iPSC reprogramming [2–6]. Pioneer TFs activities differ from conventional transcription factors in their mechanism of action. They bind directly to condensed chromatin and elicit a series of chromatin remodeling events that lead to opening of the chromatin. Chromatin decondensation by pioneer factors progressively occurs during cell division and in turn exposes specific gene promoters in the DNA to which TFs can now directly bind to promoters that are readily accessible[2, 6]. Here, we will summarize recent advancements on our understanding of the molecular mechanisms underlying reprogramming to iPSC as well as the implications that pioneer Transcription Factor activities might play during different lineage conversion processes. - Highlights: • Pioneer transcription factor activity underlies the initial steps of iPSC generation. • Reprogramming can occur by cis- and/or trans- reprogramming events. • Cis-reprogramming implies remodeling of the chromatin for enabling TF accessibility. • Trans-reprogramming encompasses direct binding of Tfs to their target gene promoters.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

The crystal structure of red fluorescent protein TagRFP-T reveals the mechanism of its superior photostability

The red fluorescent protein variant TagRFP-T has greatly improved photostability over its parent molecule, TagRFP, but the underlying mechanism leading to this improvement is to date unknown. The 1.95 Å resolution crystallographic structure of TagRFP-T showed that its chromophore exists as a mixture of cis and trans coplanar isomers in roughly equal proportions. Interestingly, both isomers are able to fluoresce, a property that has never been observed in any other fluorescent protein. We propose a “circular restoration model” for TagRFP-T to explain its superior photostability: There are four co-existing chromophore states (cis/trans protonated/ionized state) that can be driven by light to transform from one state into another. This model also explains how TagRPF-T essentially eliminates the temporary dark state (reversible photobleaching). - Highlights: • The 1.95 Å resolution crystal structure of TagRFP-T was determined. • The chromophore of TagRFP-T contains a mixture of cis and trans coplanar isomers. • A “circular restoration model” was proposed to explain the superior photostability. • The chromophore can reversibly convert between cis/trans protonated/ionized states. • The light-driven conversion reduce the dark state (reversible photobleaching).

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

MiR-509-3-5p causes aberrant mitosis and anti-proliferative effect by suppression of PLK1 in human lung cancer A549 cells

MicroRNAs (miRNAs) are potent post-transcriptional regulators of gene expression and play roles in DNA damage response (DDR). PLK1 is identified as a modulator of DNA damage checkpoint. Although down-regulation of PLK1 by certain microRNAs has been reported, little is known about the interplay between PLK1 and miR-509-3-5p in DDR. Here we have demonstrated that miR-509-3-5p repressed PLK1 expression by targeting PLK1 3′-UTR, thereby causing mitotic aberration and growth arrest of human lung cancer A549 cells. Repression of PLK1 by miR-509-3-5p was further evidenced by over-expression of miR-509-3-5p in A549, HepG2 and HCT116p53{sup −/−} cancer cells, in which PLK1 protein was suppressed. Consistently, miR-509-3-5p was stimulated, while PLK1 protein was down-regulated in A549 cells exposed to CIS and ADR, suggesting that suppression of PLK1 by miR-509-3-5p is a component of CIS/ADR-induced DDR pathway. Flow cytometry and immunofluorescence labeling showed that over-expression of miR-509-3-5p in A549 induced G2/M arrest and aberrant mitosis characterized by abnormal bipolar mitotic spindles, condensed chromosomes, lagging DNA and chromosome bridges. In addition, over-expression of miR-509-3-5p markedly blocked A549 cell proliferation and sensitized the cells to CIS and ADR treatment. Taken together, miR-509-3-5p is a feasible suppressor for cancer by targeting PLK1. Our data may provide aid in potential design of combined chemotherapy and in our better understanding of the roles of microRNAs in response to DNA damage. - Highlights: • MiR-509-3-5p represses PLK1 expression by targeting PLK1 3ГЉВ№-UTR. • Expression of miR-509-3-5p is induced and PLK1 repressed upon DNA damage. • Overexpression of miR-509-3-5p induces G2/M arrest and aberrant mitosis. • MiR-509-3-5p inhibits cell proliferation and sensitizes cells to DNA damage agents.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Giantin is required for coordinated production of aggrecan, link protein and type XI collagen during chondrogenesis

Highlights: • Specificity of giantin for intracellular traffic of cartilage ECM is proposed. • Loss of giantin result in decreased of aggrecan, link protein and hyaluronan. • Loss of giantin cause increased type XI collagen. • Giantin is involved in perichondrium differentiation. Extracellular matrix (ECM) constitutes a proper micro-environment for cell proliferation, migration and differentiation, as well as playing pivotal roles in developmental processes including endochondral ossification. Cartilage ECM is mainly composed of fibrous proteins, including collagen, proteoglycan, and hyaluronan. Because almost all ECM components are transported by intracellular vesicular transport systems, molecules that mediate vesicle transport are also important for endochondral ossification. Giantin, encoded by the Golgb1 gene, is a tethering factor for coatomer 1 (COPI) vesicles and functions in the cis-medial Golgi compartments. An insertion mutation in the Golgb1 gene, resulting in a lack of giantin protein expression, has been detected in ocd/ocd rats that exhibit a pleiotropic phenotype including osteochondrodysplasia. To reveal the function of giantin in chondrogenesis, the present study assessed the effects of loss of giantin expression on cartilage ECM and Golgi morphology. Giantin was expressed in normal, but not in ocd/ocd, chondrocytes in the epiphyseal areas of embryonic femurs, whereas GM130 was expressed in both normal and ocd/ocd chondrocytes. The staining intensities of safranin O and azan (aniline blue) were reduced and enhanced, respectively, in epiphyseal cartilage of ocd/ocd femurs. Immunostaining showed that levels of type II collagen and fibronectin were comparable in normal and ocd/ocd cartilage. Levels of type XI collagen were higher, while levels of aggrecan, link protein and hyaluronan were lower, in ocd/ocd than in normal cartilage, although semi-quantitative RT-PCR showed similar levels of type XI collagen, aggrecan and link protein mRNAs in normal and ocd/ocd cartilage. Isolated chondrocytes of ocd/ocd and normal rats showed similar immunostaining patterns for cis-, medial-, and trans-Golgi marker proteins, whereas monolayers of ocd/ocd chondrocytes showed reduced levels of aggrecan and link protein and increased level of type XI collagen in spite of similar transcripts levels. These findings suggest that giantin plays a pivotal role in coordinated production of aggrecan, link protein and type XI collagen in chondrocytes, and that loss of giantin causes osteochondrodysplasia with disturbance of these ECM components.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Evaluation of synthetic promoters in Physcomitrella patens

Highlights: • Cis-elements can be randomly assembled to construct short plant promoters. • Synthetic promoters have higher mRNA expression level than the endogenous PpAct7. • Synthetic promoters have similar protein expression levels to AtUBQ10 promoter. Securing a molecular toolbox including diverse promoters is essential for genome engineering. However, native promoters have limitations such as the available number or the length of the promoter. In this work, three short synthetic promoters were characterized by using the yellow fluorescent protein Venus. All of the tested promoters were active and showed higher mRNA expression than housekeeping gene PpAct7, and similar protein expression level to the AtUBQ10 promoter. This study shows that few cis-regulatory elements are enough to establish a strong promoter for continuous expression of genes in plants. Along with this, the study enhance the number of available promotors to be used in P. patens. It also demonstrates the potential to construct multiple non-native promoters on demand, which would aid to resolve one bottleneck in multiple pathway expression in P. patens and other plants.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

The gene expression of two endoplasmic reticulum aminopeptidase 1 isoforms is regulated by distinct posttranscriptional mechanisms

Highlights: • ERAP1 contains two isoforms that exchange 3′ untranslated regions of mRNA. • One of ERAP1 isoform is suppressed the protein expression posttranscriptionally. • We identified cis-elements that repressed the alternative splicing within ERAP1. • IFN-γ stimulation affects transcription and the alternative splicing of ERAP1. Endoplasmic Reticulum Aminopeptidase 1 (ERAP1) is a multifunctional enzyme belonging to the M1 family of aminopeptidases and shown to be associated with various autoimmune diseases. Human ERAP1 protein has two isoforms produced by alternative splicing of the 3′ terminal exon, although their functional differences have not yet been fully clarified. In this study, we showed that the isoforms undergo different posttranscriptional regulation mechanisms via their respective 3′ untranslated regions. Using a reporter system, we identified several cis-elements that are important for the regulation of alternative splicing. Finally, we revealed a close relationship between the transcriptional induction of the ERAP1 gene by interferon-gamma and the alternative splicing. These results suggest that the two ERAP1 isoforms function under different pathophysiological conditions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2026

Oxidative Deboronation of Boronic Acids by Hydrogen Peroxide in Planta Generates Borate for Cross-Linking of Rhamnogalacturonan II

Vascular plants require boron to cross-link the rhamnogalacturonan-II (RG-II) domain of pectin to form functional cell walls. Boronic acids, which form reversible esters with cis-diols like borate, have been proposed to influence RG-II cross-linking, though the mechanism remains unclear. We used suspension-cultured rose cells adapted to grow without boron to investigate the effect of boronic acids on RG-II dimerization. When grown with phenylboronic acid (PBA) as the sole boron source, nearly all RG-II was crosslinked, whereas methylboronic acid (MBA) only partially restored cross-linking. In contrast, in vitro assays showed that homogeneous RG-II monomers did not dimerize with alkyl or aryl boronic acids unless supplemented with hydrogen peroxide (H2O2), which oxidatively converts boronic acids to boric acid. Real-time NMR spectroscopy and density functional theory calculations provided insight into the reaction mechanism and energetics of oxidation respectively. Together, our data show that exogenous boronic acids are a source of boric acid for plants, and that the deboronation reaction generates aryl or alkyl alcohol byproducts that can undergo further chemical modification in planta. The fate and potential roles of these byproducts in planta remain to be determined.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Selective carboxylation of alkenes with CO 2 to form unsaturated carboxylic acid on Sc-exchanged MFI zeolite

Utilization of CO 2 in chemical synthesis as C1 carbon feedstock to introduce a carboxylic group into alkene is valuable for producing unsaturated carboxylic acids. Selective carboxylation of alkenes at targeted positions can be used to regulate the production of such specific unsaturated carboxylic acids or functionalize hydrocarbon plastics that possess residual C=C double bonds. In this study, we investigated the carboxylation of 1-butene and 2-butene (as representative alkene) with CO 2 on Sc-exchanged MFI zeolites using density functional theory calculations. Here, we find that similar to ethylene, the carboxylation of butene is also rate-limited by the β–H transfer. We examined carboxylation at the C1 and C2 positions of 1-butene and cis and trans isomers for 2-butene. Based on activation barriers of the β–H transfer, our results demonstrate that Sc-MFI zeolite preferably carboxylates at the terminal position of butene. In the case of 2-butene, carboxylation of the trans isomer is more favorable than the cis isomer. Furthermore, We show that the energy of degenerate orbitals of C, O and H atoms (involved in the β–H transfer) in the metallalactone ring regulates the activation energy of the β–H transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Autoignition of trans -decalin, a diesel surrogate compound: Rapid compression machine experiments and chemical kinetic modeling

Decahydronaphthalene (decalin), with both cis and trans isomers, is a bicyclic alkane that is found in aviation fuels, diesel fuels, and alternative fuels from tar sands and oil shales. Between the two decalin isomers, trans-decalin has a lower cetane number, is energetically more stable, and has a lower boiling point. Moreover, trans-decalin has often been chosen as a surrogate component to represent two-ring naphthenes in transportation fuels. Recognizing the importance of understanding the chemical kinetics of trans-decalin in the development of surrogate models, an experimental and modeling study has been conducted. Experimentally, the autoignition characteristics of trans-decalin were investigated using a rapid compression machine (RCM) by using trans-decalin/O2/N2 mixtures at compressed pressures of PC=10–25 bar, low-to-intermediate compressed temperatures of TC=620–895 K, and varying equivalence ratios of Φ=0.5, 1.0, and 2.0. These new experimental data demonstrate the effects of pressure, fuel loading, and oxygen concentration on autoignition of trans-decalin. The current RCM data of trans-decalin at lower temperatures were also found to complement well with the literature shock tube data of decalin (mixture of cis+trans) at higher temperatures. Furthermore, a chemical kinetic model for the oxidation of trans-decalin has been developed with new reaction rates and pathways, including, for the first time, a fully-detailed representation of low-temperature chemical kinetics for transdecalin. This model shows good agreement with the overall ignition delay results of the current RCM experiments and the literature shock tube studies. Chemical kinetic analyses of the developed model were further conducted to help identify the fuel decomposition pathways and the reactions controlling the autoignition at varying conditions.

10 SYNTHETIC FUELS↗
DOE OSTI2023

Identification of over ten thousand candidate structured RNAs in viruses and phages

Structured RNAs play crucial roles in viruses, exerting influence over both viral and host gene expression. However, the extensive diversity of structured RNAs and their ability to act in cis or trans positions pose challenges for predicting and assigning their functions. While comparative genomics approaches have successfully predicted candidate structured RNAs in microbes on a large scale, similar efforts for viruses have been lacking. In this study, we screened over 5 million DNA and RNA viral sequences, resulting in the prediction of 10,006 novel candidate structured RNAs. These predictions are widely distributed across taxonomy and ecosystem. We found transcriptional evidence for 206 of these candidate structured RNAs in the human fecal microbiome. These candidate RNAs exhibited evidence of nucleotide covariation, indicative of selective pressure maintaining the predicted secondary structures. Our analysis revealed a diverse repertoire of candidate structured RNAs, encompassing a substantial number of putative tRNAs or tRNA-like structures, Rho-independent transcription terminators, and potentially cis-regulatory structures consistently positioned upstream of genes. In summary, our findings shed light on the extensive diversity of structured RNAs in viruses, offering a valuable resource for further investigations into their functional roles and implications in viral gene expression and pave the way for a deeper understanding of the intricate interplay between viruses and their hosts at the molecular level.

59 BASIC BIOLOGICAL SCIENCES↗