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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Characterizing Complex Gas–Solid Interfaces with in Situ Spectroscopy: Oxygen Adsorption Behavior on Fe–N–C Catalysts

Electrocatalysts for the oxygen reduction reaction within polymer electrolyte membrane fuel cells based on iron, nitrogen, and carbon elements (Fe–N–C) are receiving significant research attention as they offer an inexpensive alternative to catalysts based on platinum-group metals. Although both the performance and the fundamental understanding of Fe–N–C catalysts have improved over the past decade, there remains a need to differentiate the relative activity of different active sites. Toward this goal, our study is focused on characterizing the interactions between O 2 and a set of five structurally different Fe–N–C materials. Detailed characterization of the Fe speciation was performed with 57 Fe Mössbauer spectroscopy and soft X-ray absorption spectroscopy of the Fe L 3,2 -edge, whereas nitrogen chemical states were investigated with X-ray photoelectron spectroscopy (XPS). In addition to initial sXAS and XPS measurements performed in ultra-high vacuum (UHV), measurements were also performed (at the identical location) in an atmosphere of 100 mTorr of O 2 at 80 °C (O 2 -rich). XPS and sXAS results reveal the presence of several types of FeNxCy adsorption sites. FeNxCy sites that are proposed as the most active ones do not show significant change (based on the techniques used in this study) when their environment is changed from UHV to O 2 -rich. Correlation with Mössbauer and sXAS results suggests that this is most likely due to the persistence of strongly adsorbed O 2 molecules from their previous exposure to air. However, other species do show spectroscopic changes from UHV conditions to O 2 -rich. This implies that these sites have a weaker interaction with O 2 that results in their desorption in vacuum conditions and re-adsorption when exposed to the O 2 -rich environment. The nature of these weakly and strongly O 2 -adsorbing FeN x C y sites is discussed in the context of different synthetic and processing parameters employed to fabricate each of these five Fe–N–C materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Exploring Trends on Coupling Mechanisms toward C 3 Product Formation in CO (2) R

Challenges in improving catalysts for electrochemical CO 2 reduction require a clear understanding of the reaction mechanisms that lead to products of higher value. Here, we use density functional theory (DFT) to determine the most competitive coupling mechanisms leading to C 3 products on Cu(100) and Cu(511). We exhaustively consider surface coupling pathways between CO* and different C 2 intermediates. On Cu(100), CO* coupling with acetaldehyde was identified as a notable step for C 3 product formation. On Cu(511), local field stabilizations enable an additional coupling step between HCCH* and CO*. This suggests that there is more than one possible pathway toward forming C 3 intermediates. Our simulations show that much like C 2 formation, C 3 formation prefers stepped surfaces with (100)-like sites and that local field stabilization can play a pivotal role in certain coupling steps.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Plasmonic Hot-Carrier Generation and Catalysis in Ti 3 C 2 O 2 from Real-Time TDDFT Simulations

Photoinduced hot electrons are central to plasmon-driven catalysis. Atomically thin Ti 3 C 2 O 2 , with high carrier density and broad optical absorption, offers a promising platform for plasmon-driven reactions. However, comprehensive investigations of its plasmon resonance, hot-carrier generation, and plasmonic catalytic performance remain limited. In this work, real-time time-dependent density functional theory (rt-TDDFT) was employed to study Ti 3 C 2 O 2 ’s plasmon excitation and hot-carrier generation from nonradiative plasmon damping. The temporal evolution of the dipole moment reveals plasmon resonance in Ti 3 C 2 O 2 , followed by strong plasmon damping that redistributes the stored energy to generate hot carriers. Ti 3 C 2 O 2 with low oxygen vacancy concentration (O v -Ti 3 C 2 O 2 ) exhibits plasmonic behavior resembling the pristine surface, and the plasmon-generated hot electrons can markedly reduce the dissociation barrier of CO 2 at the oxygen vacancy. These findings provide fundamental insights into the plasmonic properties of Ti 3 C 2 O 2 and how they drive its catalytic performance in surface reactions, which is valuable for advancing plasmon-driven catalysis.

CO2 reduction↗
DOE OSTI2021

Access to Perfluorometallacyclopentane Complexes of Cobalt through the [(MeCN) 4 Co(C 4 F 8 )][PF 6 ] Precursor

Here, the acetonitrile ligands in [(MeCN) 4 Co(C 4 F 8 )][PF 6 ] were found to be labile toward ligand substitution reactions, allowing for the preparation of [(MeCN)(tpy)Co(C 4 F 8 )][PF 6 ], [(tpy)CoBr(C 4 F 8 )], [(bpy) 2 Co(C 4 F 8 )][PF 6 ], and [(cis-κ 2 -pym-PPh 2 ) 2 Co(C 4 F 8 )][PF 6 ] (tpy = 2,2':6',2"-terpyridine, bpy = 2,2'-bipyridine, and pym-PPh 2 = diphenyl(2-pyrimidyl)phosphine). All of the aforementioned complexes have been structurally characterized by X-ray diffraction. Additionally, an improved procedure for the preparation of [(MeCN) 4 Co(C 4 F 8 )][X] (X = PF 6 or BF 4 ) is reported.

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

Biocatalytic Synthesis of α-Amino Esters via Nitrene C–H Insertion

α-Amino esters are precursors to noncanonical amino acids used in developing small-molecule therapeutics, biologics, and tools in chemical biology. α-C–H amination of abundant and inexpensive carboxylic acid esters through nitrene transfer presents a direct approach to α-amino esters. Methods for nitrene-mediated amination of the protic α-C–H bonds in carboxylic acid esters, however, are underdeveloped. This gap arises because hydrogen atom abstraction (HAA) of protic C–H bonds by electrophilic metal-nitrenoids is slow: metal-nitrenoids preferentially react with polarity-matched, hydridic C–H bonds, even when weaker protic C–H bonds are present. This study describes the discovery and evolution of highly stable protoglobin nitrene transferases that catalyze the enantioselective intermolecular amination of the α-C–H bonds in carboxylic acid esters. We developed a high-throughput assay to evaluate the activity and enantioselectivity of mutant enzymes together with their sequences using the Every Variant Sequencing (evSeq) method. Furthermore, the assay enabled the identification of enantiodivergent enzymes that function at ambient conditions in Escherichia coli whole cells and whose activities can be enhanced by directed evolution for the amination of a range of substrates.

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

Alkane Dehydrogenation and H/D Exchange by a Cationic Pincer-Ir(III) Hydride: Cooperative C–H Addition and β -H Elimination Modes Induce Anomalous Selectivity

We report that the cationic iridium complex ( iPr PCP)IrH + catalyzes the transfer-dehydrogenation of alkanes to give alkenes and hydrogen isotope exchange (HIE) of alkanes and arenes. Contrary to established selectivity trends found for C–H activation by transition metal complexes, strained cycloalkanes, including cyclopentane, cycloheptane, and cyclooctane, undergo C–H addition much more readily than n-alkanes, which in turn are much more reactive than cyclohexane. Aromatic C–H bonds also undergo H/D exchange much less rapidly than those of the strained cycloalkanes, but much more favorably than cyclohexane. The order of reactivity toward dehydrogenation correlates qualitatively with the reaction thermodynamics, but the magnitude is much greater than can be explained by thermodynamics. Accordingly, the cycloalkenes corresponding to the strained cycloalkanes undergo hydrogenation much more readily than cyclohexene, despite the less favorable thermodynamics of such hydrogenations. Here, computational (DFT) studies allow rationalization of the origin of reactivity and the unusual selectivity. Specifically, the initial C–H addition is strongly assisted by β-agostic interactions, which are particularly favorable for the strained cycloalkanes. Subsequent to α-C–H addition, the H atom of the β-agostic C–H bond is transferred directly to the hydride ligand of ( iPr PCP)IrH + to give a dihydrogen ligand.

02 PETROLEUM↗
DOE OSTI2025

Uncovering the True Active Sites in Ni–N–C Catalysts for CO 2 Electroreduction

Understanding and designing active sites in single-atom catalysts (SACs) requires going beyond static models to capture their dynamic evolution under realistic electrochemical conditions. Here, in this work, we develop an integrated theoretical framework that accounts for operational conditions, by combining grand canonical density functional theory (GC-DFT) with machine-learning-accelerated sampling, to uncover structure–activity–stability relationships in Ni–N–C SACs for the CO 2 reduction reaction (CO 2 RR). A library of NiN x C 4–x (x = 0–4) motifs─representing coordination defects likely formed during high-temperature synthesis─was systematically evaluated. Under working conditions, these sites were found to undergo hydrogenation, and NiN 3 C 1_ H 1 was identified as the most probable active site. At reducing potentials, hydrogen adsorbs spontaneously at C–Ni bridge sites rather than Ni top sites, while subsurface hydrogen facilitates bent CO 2 adsorption crucial for activation. High CO 2 RR selectivity toward CO arises from site separation: Ni centers drive CO2RR, while the hydrogen evolution reaction (HER) occurs at the C–Ni bridge or N sites and from thermodynamic suppression of HER at moderate hydrogen coverage. At more negative potentials, a shift in the CO 2 RR rate-determining process (RDP) and Ni out-of-surface displacement induced by coadsorption of H and H 2 O jointly reduce activity and selectivity. Thus, both the high CO2RR selectivity of Ni–N–C catalysts and its reversal with more negative potentials can be rationalized by accounting for hydrogenated surfaces. This highlights the necessity of modeling realistic; in situ conditions. This framework provides generalizable insights into the dynamic behavior of active sites in SACs, offering guidance for the rational design of active and robust catalysts for a wide range of electrochemical reactions.

25 ENERGY STORAGE↗
DOE OSTI2023

Gas phase synthesis of the C40 nano bowl C 40 H 10

Nanobowls represent vital molecular building blocks of end-capped nanotubes and fullerenes detected in combustion systems and in deep space such as toward the planetary nebula TC-1, but their fundamental formation mechanisms have remained elusive. By merging molecular beam experiments with electronic structure calculations, we reveal a complex chain of reactions initiated through the gas-phase preparation of benzocorannulene (C 24 H 12 ) via ring annulation of the corannulenyl radical (C 20 H 9 • ) by vinylacetylene (C 4 H 4 ) as identified isomer-selectively in situ via photoionization efficiency curves and photoion mass-selected threshold photoelectron spectra. In silico studies provided compelling evidence that the benzannulation mechanism can be expanded to pentabenzocorannulene (C 40 H 20 ) followed by successive cyclodehydrogenation to the C40 nanobowl (C 40 H 10 ) – a fundamental building block of buckminsterfullerene (C 60 ). This high-temperature pathway opens up isomer-selective routes to nanobowls via resonantly stabilized free-radical intermediates and ring annulation in circumstellar envelopes of carbon stars and planetary nebulae as their descendants eventually altering our insights of the complex chemistry of carbon in our Galaxy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Lowering the operating temperature of protonic ceramic electrochemical cells to <450 °C

Protonic ceramic electrochemical cells (PCECs) can be employed for power generation and sustainable hydrogen production. Lowering the PCEC operating temperature can facilitate its scale-up and commercialization. However, achieving high energy efficiency and long-term durability at low operating temperatures is a long-standing challenge. Here, in this work, we report a simple and scalable approach for fabricating ultrathin, chemically homogeneous, and robust proton-conducting electrolytes and demonstrate an in situ formed composite positive electrode, Ba 0.62 Sr 0.38 CoO 3–δ –Pr 1.44 Ba 0.11 Sr 0.45 Co 1.32 Fe 0.68 O 6–δ , which significantly reduces ohmic resistance, positive electrode–electrolyte contact resistance and electrode polarization resistance. The PCECs attain high power densities in fuel-cell mode (~0.75 W cm –2 at 450 °C and ~0.10 W cm –2 at 275 °C) and exceptional current densities in steam electrolysis mode (–1.28 A cm –2 at 1.4 V and 450 °C). At 600 °C, the PCECs achieve a power density of ~2 W cm –2 . Additionally, we demonstrate the direct utilization of methane and ammonia for power generation at <450 °C. Our PCECs are also stable for power generation and hydrogen production at 400 °C.

25 ENERGY STORAGE↗
DOE OSTI2021

High light and temperature reduce photosynthetic efficiency through different mechanisms in the C 4 model Setaria viridis

C 4 plants frequently experience high light and high temperature conditions in the field, which reduce growth and yield. However, the mechanisms underlying these stress responses in C 4 plants have been under-explored, especially the coordination between mesophyll (M) and bundle sheath (BS) cells. We investigated how the C4 model plant Setaria viridis responded to a four-hour high light or high temperature treatment at photosynthetic, transcriptomic, and ultrastructural levels. Although we observed a comparable reduction of photosynthetic efficiency in high light or high temperature treated leaves, detailed analysis of multi-level responses revealed important differences in key pathways and M/BS specificity responding to high light and high temperature. We provide a systematic analysis of high light and high temperature responses in S. viridis, reveal different acclimation strategies to these two stresses in C 4 plants, discover unique light/temperature responses in C 4 plants in comparison to C 3 plants, and identify potential targets to improve abiotic stress tolerance in C 4 crops.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Targeted synthesis and reaction mechanism discussion of Mo 2 C based insertion-type electrodes for advanced pseudocapacitors

Mo 2 C is one of the few compounds that possess good electronic conductivity. Meanwhile, it possesses a natural 1D zigzag tunnel structure that is ideally suited for fast ion diffusion. Here, an effective approach is demonstrated for fabrication of structurally stable N-doped Mo 2 C/C nanobelts. They demonstrate high and fast energy storage ability with initial capacitances of 1139 C g -1 at 1 mV s-1, 151 C g -1 at an extremely high scan rate of 2000 mV s -1 and 208 C g -1 at a discharge current density of 200 A g -1 . After electrochemical activation of cycling, the capacity is continuously enhanced and much higher capacitances of 2523 C g -1 at 1 mV s -1 and 1403 C g -1 at 50 A g -1 are achieved after 15,000 cycles at 50 mV s -1 . Using the power law, it is evaluated that a surface-controlled capacitive process makes the main contribution to the capacity, which is over 90% when the scan rates are higher than 10 mV s -1 and still high as 73% at 1 mV s -1 . From in situ synchrotron XRD, it is found that there is a negligible change in the crystal structure and volume during charging/discharging, reflecting an insertion-type charge storage mechanism.

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

Photoemission from hybrid states of Cl@C 60 before and after a stabilizing charge transfer

Photoionization calculations of the endofullerene molecule Cl@C 60 with an open-shell chlorine atom are performed in the linear response density functional theory based on a spherical jellium model of C 60 . Cross sections for atom–fullerene hybrid photoemission studied show the effects of the hybridization symmetry, the giant plasmon and the molecular cavity. Comparisons with the results of Ar@C 60 provide insights into the role of a shell-closing electron and its influence on the dynamics. The results for Cl@C 60 are further compared with those of a more stable configuration that results after a C 60 electron transfers to Cl forming Cl–@${{\text{C}}_{60}}^{+}$. This comparison reveals noticeable differences in the ionization properties of the antibonding hybrid state while the bonding hybrid remains nearly unaltered showing a magnification covering the entire giant plasmon energy range. Furthermore, these predictions should raise interest in probing the molecular configuration using photoelectron spectroscopy.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2024

Designing Ta C Virtual Substrates for Vertical Al x Ga 1 − x N Power Electronics Devices

Power electronics are critical for a sustainable energy future, playing a key role in electrification and integration of renewable energy sources into the grid. Advances in ultrawide band gap materials are needed to handle higher powers in smaller form factors while reducing electrical and thermal losses. High Al content Al x Ga 1 − x N is theoretically capable of meeting these demands, but its impact in power electronics has been severely restricted by a lack of substrates that can satisfy conductivity, lattice matching, and/or thermal expansion requirements. We demonstrate that electrically conductive Ta C can be used as a virtual substrate for Al x Ga 1 − x N heteroepitaxy. Scaleably sputtered Ta C grown on Al 2 O 3 , followed by high-temperature face-to-face annealing, produces a thin film Ta C template with an effective hexagonal lattice constant matched to Al 0.70 Ga 0.30 N . Annealing of the Ta C promotes recrystallization, significantly improving crystallinity and reducing crystalline defects from as-deposited columnar grains to a step-and-terrace surface morphology, enabling the subsequent growth of high-quality Al 0.70 Ga 0.30 N by molecular beam epitaxy. X-ray diffraction and scanning transmission electron microscopy confirm that the Al x Ga 1 − x N layer is heteroepitaxially aligned, strain-free, and lattice-matched, transitioning abruptly from Ta C to Al x Ga 1 − x N without intermediate phases. These results demonstrate Ta C virtual substrates as electrically conductive, lattice-matched, and thermally compatible templates for vertical Al x Ga 1 − x N devices that can meet the growing power needs of a sustainable energy future. Published by the American Physical Society 2024

36 MATERIALS SCIENCE↗
DOE OSTI2024

Impact of Sugarcane Cultivation on C Cycling in Southeastern United States Following Conversion From Grazed Pastures

ABSTRACT The expansion of sugarcane, a tropical high‐yielding feedstock, will likely reshape the Southeastern United States (SE US) bioenergy landscape. However, the sustainability of sugarcane, particularly as it displaces grazed pastures, is highly uncertain. Here, we investigated how pasture conversion to sugarcane in subtropical Florida impacts net ecosystem CO 2 exchange (NEE) and net ecosystem carbon (C) balance (NECB). Measurements were made over three full growth cycles (> 3 years) in sugarcane—plant cane, PC; first ratoon cane, FRC; second ratoon cane, SRC—and in improved (IM) and semi‐native (SN) pastures, which make up ca. 37% of agricultural land in the region. Immediately following conversion, PC was a stronger net source of CO 2 than pastures, indicating the importance of CO 2 losses related to land disturbance. Sugarcane, however, shifted to a strong net sink of CO 2 after first regrowth, and overall sugarcane was a stronger net CO 2 sink than pastures. Both stand age and low water availability during cane emergence and tillering substantially decreased its potential gross CO 2 uptake. Accounting for all C gains and removals (i.e., NECB), greater frequency of burn events and repeated harvest increased removals and overall made sugarcane a stronger C source relative to pastures despite substantial C inputs from the previous land use and a stronger CO 2 sink strength. Time since conversion substantially reduced C losses from sugarcane, and the NECB of SRC was similar to that of IM pasture but lower than that of SN pasture, indicating a rapid shift in the NECB of cane. We conclude that the C‐balance implications following conversion will depend on the proportion of IM versus SN pastures converted to sugarcane. Furthermore, our findings suggest that no‐burn harvest management strategies will be critical to the development of a sustainable bioenergy landscape in SE US.

Gomez‐Casanovas, Nuria↗
DOE OSTI2022

Mesophyll conductance response to short-term changes in p CO 2 is related to leaf anatomy and biochemistry in diverse C 4 grasses

Mesophyll CO 2 conductance (g m ) in C 3 species responds to short-term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C 3 species, there is less information on g m responses to short-term changes in environmental conditions such as partial pressure of CO 2 (pCO 2 ) across diverse C 4 species and the potential determinants of these responses. Using 16 C 4 grasses we investigated the response of g m to short-term changes in pCO 2 and its relationship with leaf anatomy and biochemistry. In general, g m increased as pCO 2 decreased (statistically significant increase in 12 species), with percentage increases in gm ranging from +13% to +250%. Greater increase in g m at low pCO 2 was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO 2 responses of g m were also able to maintain their leaf water-use efficiencies (TE i ) under low CO 2 . Our study advances understanding of CO 2 response of g m in diverse C 4 species, identifies the key leaf traits related to this response and has implications for improving C 4 photosynthetic models and TE i through modification of g m .

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

K 2P channel C-type gating involves asymmetric selectivity filter order-disorder transitions

K 2P potassium channels regulate cellular excitability using their selectivity filter (C-type) gate. C-type gating mechanisms, best characterized in homotetrameric potassium channels, remain controversial and are attributed to selectivity filter pinching, dilation, or subtle structural changes. The extent to which such mechanisms control C-type gating of innately heterodimeric K 2P s is unknown. Here, combining K 2P 2.1 (TREK-1) x-ray crystallography in different potassium concentrations, potassium anomalous scattering, molecular dynamics, and electrophysiology, we uncover unprecedented, asymmetric, potassium-dependent conformational changes that underlie K 2P C-type gating. These asymmetric order-disorder transitions, enabled by the K 2P heterodimeric architecture, encompass pinching and dilation, disrupt the S1 and S2 ion binding sites, require the uniquely long K 2P SF2-M4 loop and conserved “M3 glutamate network,” and are suppressed by the K 2P C-type gate activator ML335. These findings demonstrate that two distinct C-type gating mechanisms can operate in one channel and underscore the SF2-M4 loop as a target for K 2P channel modulator development.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Gas-phase formation of the resonantly stabilized 1-indenyl (C 9 H 7 • ) radical in the interstellar medium

The 1-indenyl (C 9 H 7 • ) radical, a prototype aromatic and resonantly stabilized free radical carrying a six- and a five-membered ring, has emerged as a fundamental molecular building block of nonplanar polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanostructures in deep space and combustion systems. However, the underlying formation mechanisms have remained elusive. Here, we reveal an unconventional low-temperature gas-phase formation of 1-indenyl via barrierless ring annulation involving reactions of atomic carbon [C( 3 P)] with styrene (C 6 H 5 C 2 H 3 ) and propargyl (C 3 H 3 • ) with phenyl (C 6 H 5 • ). Macroscopic environments like molecular clouds act as natural low-temperature laboratories, where rapid molecular mass growth to 1-indenyl and subsequently complex PAHs involving vinyl side-chained aromatics and aryl radicals can occur. These reactions may account for the formation of PAHs and their derivatives in the interstellar medium and carbonaceous chondrites and could close the gap of timescales of their production and destruction in our carbonaceous universe.

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

Mid-day photomixotrophy by Roseiflexus spp. and implications for the 13 C content of hot spring cyanobacterial mats

Microbial mats inhabiting extreme environments have been studied as modern analogs of stromatolites. Mats in Octopus Spring and Mushroom Spring, Yellowstone National Park, are predominated by unicellular photoautotrophic cyanobacteria (Synechococcus spp.), which are thought to cross-feed filamentous photoheterotrophic bacteria (mainly Roseiflexus spp.), except under early morning anoxic conditions when Roseiflexus spp. have been shown to fix dissolved inorganic carbon (DIC). Transcription patterns, however, suggest that Roseiflexus spp. may perform photomixotrophy, in which DIC is incorporated together with organic compounds during the daytime. We investigated the roles played by Synechococcus spp. and Roseiflexus spp. in DIC and organic matter uptake in mid-day light and oxic mats. Mass spectrometry was used to show that 13 C-bicarbonate uptake under infrared (IR) light (utilized by anoxygenic phototrophs) or visible-minus-blue light (V-B) (used by cyanobacteria) was about two-thirds and one-third, respectively, of that incorporated in full light. Laser-ablation mass spectrometry analysis demonstrated that 13 C incorporation under V-B light was restricted to the uppermost portion of the mat, whereas 13 C incorporation under IR light was maximal in deeper mat layers. 13 C-acetate, -propionate, -lactate, and -glycolate were incorporated to an equal or greater extent under IR and full light. Incorporation of 13 C into peptides showed that both Synechococcus spp. and Roseiflexus spp. were active in DIC uptake, whereas Roseiflexus spp. exhibited greater uptake of 13 C-organic acids, especially glycolate and lactate, into peptides. Peptides of proteins of the 3-hydroxypropionate pathway were labeled. Thus, Roseiflexus spp. appears to exhibit photomixotrophy throughout the day.

Roseiflexus↗