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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

An experimental and kinetic modeling study of the ignition of 2-methyl decane

Ignition delay times (IDTs) of 2-methyl decane (C 11 H 24 -2) are measured in a high-pressure shock tube and in a rapid compression machine at equivalence ratios in the range 0.5–2.0 at 90 % dilution, at temperatures in the range 600–1430 K and at pressures of 15 and 30 bar. To clarify the effect of the branched methyl group on fuel oxidation, IDTs of n-undecane (nC 11 H 24 ) are also measured at similar conditions to those measured for C 11 H 24 -2. A new chemical kinetic mechanism, using C3MechV4.0.1 as the core chemistry, is developed and validated against the new experimental data. The thermodynamic properties of the fuel (RH), alkyl (Ṙ), alkyl peroxy (RȮ 2 ), hydroperoxy-alkyl (Q̇OOH), and peroxy hydroperoxy alkyl (Ȯ 2 QOOH) radicals are updated in both the C 11 H 24 -2 and nC 11 H24 models using THERM25. A reaction path flux analysis for C 11 H 24 -2 at different temperatures was conducted. Compared to nC 11 H 24 , C 11 H 24 -2 shows slower reactivity. At low and intermediate temperatures, the chain propagation pathway Q̇OOH ↔ C 11 cyclic ether + ȮH is favored for C 11 H 24 -2, while the chain branching pathway Q̇OOH ↔ Ȯ 2 QOOH ↔ C 11 carbonyl hydroperoxide (KHP) + ȮH is suppressed, leading to lower reactivity compared to nC 11 H 24 . At high temperatures, the presence of the branched methyl group inhibits the direct decomposition of the fuel, resulting in reduced C 2 H 4 formation, which in turn suppresses the reactivity of the fuel.

2-methyl decane↗
DOE OSTI2020

Clumped 13 CH 2 D and 12 CHD 2 compositions of methyl groups from wood and synthetic monomers: Methods, experimental and theoretical calibrations, and initial results

Methyl groups are found in numerous biogenic and synthetic materials including geologically preserved materials such as wood. The carbon and hydrogen isotope compositions of methyl groups are used as tracers in biogeochemical cycles, as paleothermometers, and to determine the hydrogen isotopic composition of ancient rain. Here we present analyses of resolved 13 C–D ( 13 CH 2 D) and D–D ( 12 CHD 2 ) clumped isotope compositions of methyl groups as new variables for the study of methyl groups in the present and past. We first present chemical methods to extract, purify, and derivatize methyl groups from methoxyl (R–O–CH 3 ) groups as CH 3 F and CH 3 Cl, and high-resolution mass spectrometric techniques to determine the clumped isotope compositions of these species. We achieve precisions for 13 C–D clumping of ±0.25‰ and D–D clumping of ±2.5‰. We anchor our clumped isotopic measurements to a thermodynamic reference frame by first calculating the theoretical temperature dependences of 13 C–D and D–D clumping in CH 3 Cl, then placing our measurements onto this reference frame through experimental internal isotopic equilibration of CH 3 Cl at 200 °C. Finally, we provide and analyze an initial dataset of clumped 13 C–D and D–D compositions of methyl groups from various commercial/synthetic monomers and environmental woods. We observe ranges in clumped isotope compositions of ~11‰ in 13 C–D and ~48‰ in D–D, and systematic differences within these ranges between methyl groups from commercial monomers and wood. Specifically, commercial clumped 13 C–D compositions are between 0 and 3‰, which correspond to apparent equilibrium temperatures between 170 °C and the infinite temperature limit. In contrast, the clumped 13 C–D compositions of wood methoxyl groups are distinctively high (9.50–11.25‰) and 3–6‰ higher than would be expected if formed in internal isotopic equilibrium at Earth-surface temperatures. Commercial/synthetic methyl and wood methoxyl clumped D–D compositions are also distinct: -5 to +13‰ in commercial monomers vs. -35 to -8‰ in wood—such negative values cannot result from formation in isotopic equilibrium and require kinetic processes to have occurred. Overall, these results indicate that wood methoxyl groups are formed out of isotopic equilibrium and that clumped isotope compositions of methyl groups may be useful tracers of methyl group sources and sinks in the environment. For instance, isotopic clumping in methyl groups may be useful for understanding controls on isotopic clumping in methane produced by methylotrophic methanogens.

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

Theory of Cation Solvation in the Helmholtz Layer of Li-Ion Battery Electrolytes

The solvation environments of Li + in conventional nonaqueous battery electrolytes, such as LiPF 6 in mixtures of ethylene carbaronate (EC) and ethyl methyl carbonate (EMC), are often used to rationalize transport properties and solid electrolyte interphase (SEI) formation. Solvation environments in the compact electrical double layer (EDL) next to the electrode, also known as the Helmholtz layer, determine (partially) what species can react to form the SEI, with bulk solvation environments often being used as a proxy. Here, we develop and test a theory of cation solvation in the Helmholtz layer of nonaqueous Li-ion battery electrolytes. First, we validate the theory against bulk and diffuse EDL atomistic molecular dynamics (MD) simulations of LiPF 6 EC/EMC mixtures as a function of surface charge, where we find the theory can qualitatively capture the solvation environments. Next, we turn to the Helmholtz layer, where we find the main effect of the solvation structures next to the electrode is an apparent reduction in the number of binding sites between Li + and the solvents, again where we find reasonable agreement with our developed theory. Finally, by solving a simplified version of the theory, we find that the probability of Li + binding to each solvent remains equal to the bulk probability, suggesting that the bulk solvation environments are a reasonable place to start when understanding battery electrolytes. Our developed formalism can be parametrized from bulk MD simulations and used to predict the solvation environments in the Helmholtz layer through reducing the number of available coordination sites, which can be used to determine what could react and form the SEI.

Helmholtz↗
DOE OSTI2025

Structure of active methyl-CoM reductase, Earth’s main methane producer

Summary Our work reveals the structure of the active state of Methyl-Coenzyme M Reductase (MCR), the key and rate-limiting enzyme in biological methane formation. We find large differences between the active Ni(I) and inactive Ni(II) proteins and provide insight into how nature makes and breaks the C-H bond of methane. The Ni(II)-F430 center in inactive MCR contains four planar nitrogen ligands, a lower axial glutamine oxo, and an upper axial thiolate. The Ni(I)-enzyme replaces the axial ligands with a single water. The one-electron redox change results in movement of the Ni ion and upward swing of the β-lactam ring in the tetrapyrrole coupled to a domino-like protein quake through second sphere residues, inter-subunit interactions, a substrate tunnel, affecting even the dimensions of the unit cell. These structural changes lead Ni(I)-MCR to release a charge clamp that, in the Ni(II) state, locks down substrate Coenzyme B. Determining the Ni(I)-MCR structure required development of rigorous anaerobic crystallographic techniques. Validation of the MCR redox state was accomplished by in-line and parallel spectroscopic and unit cell analyses. This structure has large implications for developing technologies to limit methane emissions and efficiently produce biofuels. Methodology described here will enhance structural biology for other oxygen-sensitive enzymes.

09 BIOMASS FUELS↗
DOE OSTI2025

Rational Design of Methylated Triazine‐Based Linear Conjugated Polymers for Efficient CO 2 Photoreduction with Water

The development of semiconducting conjugated polymers for photoredox catalysis holds great promise for sustainable utilization of solar energy. In this work, a new family of porous methylated triazine‐based linear conjugated polymers is reported that enable efficient photoreduction of carbon dioxide (CO 2 ) with water (H 2 O) vapor, in the absence of any additional photosensitizer, sacrificial agents or cocatalysts. It is demonstrated that the key lies in the generation of methylated triazine linkages through a facile condensation reaction between benzamidine and acetic anhydride, which impedes the formation of conventional triazine‐based frameworks. It is also shown that regulating conjugated linear backbones with different lengths of electron‐donated benzyl units provides a facile means to modulate their optical properties and the exciton dissociation, thereby affording more long‐lived photogenerated charge carriers and boosting charge separation and transfer. A high‐performance carbon monoxide (CO) production rate of 218.9 µmol g −1 h −1 is achieved with ≈ 100% CO selectivity, which is accompanied by exceptional H 2 O oxidation to oxygen (O 2 ). It anticipates this new study will advance synthetic approaches toward polymeric semiconductors and facilitate new possibilities for triazine‐based conjugated polymers with promising potential in artificial photocatalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Tunable Crosslinked Ether Polymer Network Electrolytes for High‐Performance All‐Solid‐State Sodium Batteries

All-solid-state batteries (ASSBs) are critical for achieving high energy density and enhanced safety. Solid polymer electrolytes (SPEs) offer key advantages over other electrolytes, including improved safety, flexibility, and interfacial contact. Among the SPEs, ether-based polymers are widely studied due to their ease of processing and high ionic conductivity (σi) in the amorphous state. In this work, the introduction of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) into an SPE matrix composed of poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) (PEG2k), and sodium bis(fluorosulfonyl)imide (NaFSI) salt is investigated to facilitate the formation of amorphous, high σ i SPEs through end-group engineering and polymer ratio optimization. PEGMEMA enhances structural integrity via crosslinking with PEGDA through its methacrylate group, while its methyl end group aids ion conduction. A 2:1:7 ratio of PEGDA:PEGMEMA:PEG2k exhibits a σi of 1.16 x 10 -4 S cm -1 and oxidative stability up to 4.4 V at 60 °C. A solid-state cell incorporating this SPE, a Na 2/3 Ni 1/3 Mn 2/3 O 2 (NM12) cathode, and a sodium-metal anode demonstrates excellent cycling stability, retaining over 80 % of its initial capacity for 150 cycles at 60 °C. The findings highlight the potential of end-group engineering in improving the electrochemical performance of SPEs.

25 ENERGY STORAGE↗
NASA NTRS1984

Nitrite reduction in paracoccus halodenitrificans: Evidence for the role of a cd-type cytochrome in ammonia formation

Cell-free extracts prepared from Paracoccus halodenitrificans catalyzed the reduction of nitrate to ammonia in the presence of dithionite and methyl viologen. Enzyme activity was located in the soluble fraction and was associated with a cytochrome whose spectral properties resembled those of a cd-type cytochrome. Unlike the sissimilatory cd-cytochrome nitrate reductase associated with the membrane fraction of P. halodenitrificans, this soluble cd-cytochrome did not reduce nitrite to nitrous oxide.

Hochstein, L. I.↗
DOE OSTI2020

Plasmon-Mediated Intramolecular Methyl Migration with Nanoscale Spatial Control

Plasmonic materials interact strongly with light to focus and enhance electromagnetic radiation down to nanoscale volumes. Due to this localized confinement, materials that support localized surface plasmon resonances are capable of driving energetically unfavorable chemical reactions. In certain cases, the plasmonic nanostructures are able to preferentially catalyze the formation of specific photoproducts, which offers an opportunity for the development of solar-driven chemical synthesis. Here, using plasmonic environments, we report inducing an intramolecular methyl migration reaction, forming 4-methylpyridine from N-methylpyridinium. Using both experimental and computational methods, we were able to confirm the identity of the N-methylpyridinium by making spectral comparisons against possible photoproducts. This reaction involves breaking a C–N bond and forming a new C–C bond, highlighting the ability of plasmonic materials to drive complex and selective reactions. Additionally, we observe that the product yield depends strongly on optical illumination conditions. This is likely due to steric hindrance in specific regions on the nanostructured plasmonic substrate, providing an optical handle for driving plasmonic catalysis with spatial specificity. Furthermore, this work adds yet another class of reactions accessible by surface plasmon excitation to the ever-growing library of plasmon-mediated chemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Bubble-Free Frontal Polymerization of Acrylates via Redox-Initiated Free Radical Polymerization

Thermal frontal polymerization (FP) of acrylate monomers mixed with conventional peroxide initiators leads to significant bubble formation at the polymerizing front, limiting their practical applications. Redox initiators present a promising alternative to peroxide initiators, as they prevent the formation of gaseous byproducts during initiator decomposition and lower the front temperature, thereby enabling bubble-free FP. In this study, we investigate the FP of acrylate monomers of varying functionalities, including methyl methacrylate (MMA), 1,6-hexanediol diacrylate (HDDA), and trimethylolpropane triacrylate (TMPTA), using N,N -dimethylaniline/benzoyl peroxide (DMA/BPO) redox couple at room temperature and compare their front behavior, pot life, and bubble formation with those of same resin systems mixed with a conventional peroxide initiator, Luperox 231. The use of redox couples in FP of acrylates shows promise for rapid, energy-efficient manufacturing of polyacrylates and can enable new applications such as 3D printing and composite manufacturing.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Does Simulated Weightlessness Alter the Methylation Status of Gene Promoters During Bone Remodeling?

The skeleton interacts with its environment in a way that resembles a mechanostat - through a controlled process of bone remodeling, namely local formation and resorption, to maintain a healthy structure. During weightlessness, astronauts lose structure in weight-bearing bones due to decreased formation by osteoblasts and increased resorption by osteoclasts. In contrast, increased mechanical loading through exercise targets bone remodeling to remove and repair microdamage, improving structural integrity. In fact, recent advances in astronaut exercise regimens have prevented the deleterious changes in skeletal structure during spaceflight. However, knowledge of the molecular underpinnings of the skeletal response to spaceflight and to mechanical stimulation is limited. We propose that epigenetic modification, specifically DNA methylation, may influence osteoblast differentiation and activity during spaceflight and exercise. We hypothesize that simulated weightlessness hypermethylates pro-osteoblastogenic gene promoters and decreases expression of osteoblastogenic genes. Oppositely, we hypothesize that mechanical loading hypomethylates pro-osteoblastogenic gene promoters and increases expression of osteoblastogenic genes.

Stevick, Rebecca J.↗
DOE OSTI2022

Computational Predictions of the Hydrolysis of 2,4,6-Trinitrotoluene (TNT) and 2,4-Dinitroanisole (DNAN)

Hydrolysis is a common transformation reaction that can affect the environmental fate of many organic compounds. In this study, three proposed mechanisms of alkaline hydrolysis of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitroaniline (DNAN) were investigated with plane-wave density functional theory (DFT) combined with ab initio and classical molecular dynamics (AIMD/MM) free energy simulations, Gaussian basis set DFT calculations, and correlated molecular orbital theory calculations. Most of the computations in this study were carried out using the Arrows web based tools. For each mechanism: Meisenheimer complex formation, nucleophilic aromatic substitution, and proton abstraction reaction energies and activation barriers were calculated for the reaction at each relevant site. For TNT, it was found that the most kinetically favorable first hydrolysis steps involve Meisenheimer complex formation by attachment of OH$^{-}$ at the C1 and C3 arene carbons and proton abstraction from the methyl group. The nucleophilic aromatic substitution reactions at the C2 and C4 arene carbons were found to be thermodynamically favorable. However, the calculated activation barriers were slightly lower than previous studies, but still found to be $\Delta$G$^{\ddagger} \approx 18$ kcal/mol using PBEo AIMD/MM free energy simulations, suggesting the reactions are not kinetically significant. For DNAN, the barriers of nucleophilic aromatic substitution were even greater ($\Delta$G$^{\ddagger} > 29$ kcal/mol PBEo AIMD/MM). Further, the most favorable hydrolysis reaction for DNAN was found to be a two-step process in which the hydroxyl first attacks the C1 carbon to form a Meisenheimer complex at the C1 arene carbon C1-(OCH$_3$)OH$^{-}$, subsequently, the methoxy anion (-OCH$_3$) at the C1 arene carbon dissociates and the proton shuttles from the C1-OH to the dissociated methoxy group, resulting in methanol and an aryloxy anion.

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

Aromatic heterobicycle-fused porphyrins: impact on aromaticity and excited state electron transfer leading to long-lived charge separation

A new synthetic method to fuse benzo[4,5]imidazo[2,1-a]isoindole to the porphyrin periphery at the β,β-positions has been developed, and its impact on the aromaticity and electronic structures is investigated. Reactivity investigation of the fused benzoimidazo-isoindole component reveals fluorescence quenching of a zinc porphyrin (AMIm-2) upon treatment with a Brønsted acid. The reaction of the zinc porphyrin (AMIm-2) with methyl iodide initiated a new organic transformation, resulting in the ring-opening of isoindole with the formation of an aldehyde and dimethylation of the benzoimidazo component. The fused benzoimidazo-isoindole component acted as a good ligand to bind platinum(II), forming novel homobimetallic and heterobimetallic porphyrin complexes. The fusion of benzoimidazo-isoindole on the porphyrin ring resulted in bathochromically shifted absorptions and emissions, reflecting the extended conjugation of the porphyrin π-system. Time-resolved emission and transient absorption spectroscopy revealed stable excited state species of the benzoimidazo-isoindole fused porphyrins. Zinc porphyrin AMIm-2 promoted excited state electron transfer upon coordinating with an electron acceptor, C60, generating a long-lived charge-separated state, in the order of 37.4 μs. The formation of the exceptionally long-lived charge-separated state is attributed to the involvement of both singlet and triplet excited states of AMIm-2, which is rarely reported in porphyrins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2012

Photochemistry of Pyrimidine in Astrophysical Ices: Formation of Nucleobases and Other Prebiotic Species

Nucleobases are N-heterocycles that are the informational subunits of DNA and RNA. They are divided into two molecular groups: pyrimidine bases (uracil, cytosine, and thymine) and purine bases (adenine and guanine). Nucleobases have been detected in meteorites, and their extraterrestrial origin confirmed by isotopic measurements. Although no N-heterocycles have ever been observed in the ISM, the positions of the 6.2- m interstellar emission features suggest a population of such molecules is likely to be present. However, laboratory experiments have shown that the ultraviolet (UV) irradiation of pyrimidine in ices of astrophysical relevance such as H2O, NH3, CH3OH, CH4, CO, or combinations of these at low temperature (less than or equal to 20 K) leads to the formation of several pyrimidine derivatives including the nucleobases uracil and cytosine, as well as precursors such as 4(3H)-pyrimidone and 4-aminopyrimidine. Quantum calculations on the formation of 4(3H)-pyrimidone and uracil from the irradiation of pyrimidine in pure H2O ices are in agreement with their experimental formation pathways.10 In those residues, other species of prebiotic interest such as urea as well as the amino acids glycine and alanine could also be identified. However, only very small amounts of pyrimidine derivatives containing CH3 groups could be detected, suggesting that the addition of methyl groups to pyrimidine is not an efficient process. For this reason, the nucleobase thymine was not observed in any of the samples. In this work, we study the formation of nucleobases and other photo-products of prebiotic interest from the UV irradiation of pyrimidine in ices containing H2O, NH3, CH3OH, and CO, mixed in astrophysical proportions.

Nuevo, Michel↗
DOE OSTI2024

Online characterization of primary and secondary emissions of particulate matter and acidic molecules from a modern fleet of city buses

The potential impact of transitioning from conventional fossil fuel to a non-fossil-fuel vehicle fleet was investigated by measuring primary emissions via extractive sampling of bus plumes and assessing secondary mass formation using the Gothenburg Potential Aerosol Mass (Go:PAM) reactor from 76 in-use transit buses. Online chemical characterization of gaseous and particulate emissions from these buses was conducted using chemical ionization mass spectrometry (CIMS) with acetate as the reagent ion, coupled with the Filter Inlet for Gases and AEROsols (FIGAERO). Acetate reagent ion chemistry selectively ionizes acidic compounds, including organic and inorganic acids, as well as nitrated and sulfated organics. A significant reduction (48 %–98 %) in fresh particle emissions was observed in buses utilizing compressed natural gas (CNG), biodiesels like rapeseed methyl ester (RME) and hydrotreated vegetable oil (HVO), and hybrid-electric HVO (HVO HEV ) compared to diesel (DSL). However, secondary particle formation from photooxidation of emissions was substantial across all the fuel types. The median ratio of particle mass emission factors of aged to fresh emissions increased in the following order: DSL buses at 4.0, HVO buses at 6.7, HVO HEV buses at 10.5, RME buses at 10.8, and CNG buses at 84. Of the compounds that can be identified by CIMS, fresh gaseous emissions from all Euro V/EEV (Enhanced Environmentally friendly Vehicle) buses, regardless of fuel type, were dominated by nitrogen-containing compounds such as nitrous acid (HONO), nitric acid (HNO 3 ), and isocyanic acid (HNCO), alongside small monoacids (C 1 –C 3 ). Notably, the emission of nitrogen-containing compounds was lower in Euro VI buses equipped with more advanced emission control technologies. Secondary gaseous organic acids correlated strongly with gaseous HNO 3 signals (R 2 =0.85–0.99) in Go:PAM, but their moderate to weak correlations with post-photooxidation secondary particle mass suggest that they are not reliable tracers of secondary organic aerosol formation from bus exhaust. Our study highlights that non-regulated compounds and secondary pollutant formation, not currently addressed in legislation, are crucial considerations in the evaluation of environmental impacts of future fuel and engine technology shifts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Inorganic Sulfur Species Formed upon Heterogeneous OH Oxidation of Organosulfates: A Case Study of Methyl Sulfate

In this report recent studies reveal that organosulfates at the particle surface can be oxidized by gas-phase OH radicals with significant rates. Inorganic sulfur species, such as the bisulfate ion (HSO 4 - ) and sulfate ion (SO 4 2- ), can be formed upon these heterogeneous oxidation processes through the formation and subsequent reactions of sulfate radical anions (SO 4 •- ) in the particle phase. However, the amount of inorganic sulfur species produced in these heterogeneous oxidation reactions is not known. We investigate the heterogeneous OH oxidation of sodium methyl sulfate (CH 3 SO 4 Na), the smallest organosulfate detected in atmospheric particles, using an oxidation flow reactor at a relative humidity of 75%. We quantify the kinetics by measuring the decay of CH 3 SO 4 Na and the amount of HSO 4 - and SO 4 2- formed upon oxidation using ion chromatography. Kinetic measurements determine the heterogeneous OH reaction rate to be (5.72 ± 0.14) x 10 -13 cm 3 molecule -1 s -1 , with an effective OH uptake coefficient, γ eff , of 0.31 ± 0.06. The molar yield of inorganic sulfur species, defined as the total number of moles of HSO 4 - and SO 4 2- formed per mole of CH 3 SO 4 Na consumed upon oxidation, is found to be significant and has an average value of 0.62 ± 0.18 upon oxidation. A kinetic model is developed to describe the kinetics and inorganic sulfur species formation upon oxidation. Model simulations suggest that CH 3 SO 4 Na tends to decompose rapidly into formaldehyde and SO 4 •- , and the reaction of SO 4 •- with CH 3 SO 4 Na plays a significant role in both governing the kinetics and the formation of inorganic sulfur species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Inhibition of DNA methylation in P. soloecismus alters algae productivity

Eukaryotic organisms regulate the organization, structure, and accessibility of their genomes through chromatin remodeling that can be inherited as epigenetic modifications. These DNA and histone protein modifications are ultimately responsible for an organism’s molecular adaptation to the environment, resulting in distinctive phenotypes. Epigenetic manipulation of algae holds yet untapped potential for the optimization of biofuel production and bioproduct formation; however, epigenetic machinery and modes-of-action have not been well characterized in algae. We sought to determine the extent to which the biofuel platform species Picochlorum soloecismus utilizes DNA methylation to regulate its genome. We found candidate genes with domains for DNA methylation in the P. soloecismus genome. Whole-genome bisulfite sequencing revealed DNA methylation in all three cytosine contexts (CpG, CHH, and CHG). While global DNA methylation is low overall (~1.15%), it occurs in appreciable quantities (12.1%) in CpG dinucleotides in a bimodal distribution in all genomic contexts, though terminators contain the greatest number of CpG sites per kilobase. The P. soloecismus genome becomes hypomethylated during the growth cycle in response to nitrogen starvation. Algae cultures were treated daily across the growth cycle with 20 μM 5-aza-2'-deoxycytidine (5AZA) to inhibit propagation of DNA methylation in daughter cells. 5AZA treatment significantly increased optical density and forward and side scatter of cells across the growth cycle (16 days). This increase in cell size and complexity correlated with a significant increase (~66%) in lipid accumulation. Site specific CpG DNA methylation was significantly altered with 5AZA treatment over the time course, though nitrogen starvation itself induced significant hypomethylation in CpG contexts. Genes involved in several biological processes, including fatty acid synthesis, had altered methylation ratios in response to 5AZA; we hypothesize that these changes are potentially responsible for the phenotype of early induction of carbon storage as lipids. This is the first report to utilize epigenetic manipulation strategies to alter algal physiology and phenotype. Collectively, these data suggest these strategies can be utilized to fine-tune metabolic responses, alter growth, and enhance environmental adaption of microalgae for desired outcomes.

5-aza-2'-deoxycytidine↗
DOE OSTI2024

The crystal structure of methanogen McrD , a methyl‐coenzyme M reductase‐associated protein

Methyl‐coenzyme M reductase (MCR) is a multi‐subunit (α 2 β 2 γ 2 ) enzyme responsible for methane formation via its unique F 430 cofactor. The genes responsible for producing MCR ( mcrA , mcrB and mcrG ) are typically colocated with two other highly conserved genes mcrC and mcrD . We present here the high‐resolution crystal structure for McrD from a human gut methanogen Methanomassiliicoccus luminyensis strain B10. The structure reveals that McrD comprises a ferredoxin‐like domain assembled into an α + β barrel‐like dimer with conformational flexibility exhibited by a functional loop. The description of the M. luminyensis McrD crystal structure contributes to our understanding of this key conserved methanogen protein typically responsible for promoting MCR activity and the production of methane, a greenhouse gas.

59 BASIC BIOLOGICAL SCIENCES↗