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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Tuning crosslinking of hybrid preceramic polymers in vat photopolymerization toward controlled ceramic yields

Control of preceramic polymer crosslinking for UV-curable processing is essential for fine 3D printing with high ceramic conversion for sustainable polymer-derived ceramics (PDC) engineering. While various factors influencing ceramic yield have been studied, the systematic exploration of the relationship between crosslinking and ceramic yield, especially when crosslinking increases volatile elements, remains open for further investigation. This study addresses this gap by utilizing vat photopolymerization (VP) additive manufacturing (AM) as a versatile platform for controlling preceramic crosslinking and ceramic yield. By rationally designing and tuning the photochemical crosslinking through digital light processing (DLP), we demonstrate that the ceramic yield can be enhanced from 64% to over 86%, even with added volatile elements. We reveal that the post-pyrolysis ceramic yield can be closely correlated with the pre-pyrolysis crosslinking of the preceramic network represented by its stiffness. This correlation thereby suggests a fast, energy-efficient, non-destructive methodology to predict and improve ceramic yield. Combined with these findings, our one-pot thiol-ene hybridization of polycarbosilane and polycarbosiloxane via DLP offers an exemplary method to generate hybrid preceramic polymers with tailored material properties toward target applications, and potentially even higher ceramic yields. This study thus contributes to achieving better resource- and energy-efficient preceramic polymer and PDC processing routes toward sustainable, advanced organic–inorganic materials manufacturing.

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

Snapshots of C-S Cleavage in Egt2 Reveals Substrate Specificity and Reaction Mechanism

Sulfur incorporation in the biosynthesis of ergothioneine, a histidine thiol derivative, differs from other well-characterized transsulfurations. A combination of a mononuclear non-heme iron enzyme-catalyzed oxidative C-S bond formation and a subsequent pyridoxal 5'-phosphate (PLP)-mediated C-S lyase reaction leads to the net transfer of a sulfur atom from a cysteine to a histidine. In this study, we structurally and mechanistically characterized a PLP-dependent C-S lyase Egt2, which mediates the sulfoxide C-S bond cleavage in ergothioneine biosynthesis. A cation-π interaction between substrate and enzyme accounts for Egt2's preference of sulfoxide over thioether as a substrate. Using mutagenesis and structural biology, we captured three distinct states of the Egt2 C-S lyase reaction cycle, including a labile sulfenic intermediate captured in Egt2 crystals. Additionally, chemical trapping and high-resolution mass spectrometry were used to confirm the involvement of the sulfenic acid intermediate in Egt2 catalysis.

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

Copper transformation, speciation, and detoxification in anoxic and suboxic freshwater sediments

The complex chemistry of copper (Cu) in freshwater sediments at low concentrations is not well understood. We evaluated the transformation processes of Cu added to freshwater sediments under suboxic and anoxic conditions. Freshwater sediments from three sources in Michigan with different characteristics (Spring Creek, River Raisin, and Maple Lake) were spiked with 30 or 60 mg kg -1 Cu and incubated under a nitrogen atmosphere. After 28-d, each treatment subset was amended with organic matter (OM) to promote anoxic conditions and evaluate its effects on Cu speciation. OM addition triggered a shift from suboxic to anoxic conditions, and sequential extractions showed that Cu accordingly shifted from acid-soluble to oxidizable fractions. Extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed that Cu sulfides dominated all anoxic samples except for Spring Creek 30 mg kg -1 , where Cu(I) was predominantly complexed to thiol groups of OM. Covellite and chalcopyrite (CuFeS 2 ) were the predominant Cu species in nearly all anoxic samples, as determined by Raman spectroscopy, scanning electron microscopy, and X-ray absorption near-edge structure (XANES) spectroscopy. Copper reduction also occurred under suboxic conditions: for two of three sediments, around 80% had been reduced to Cu(I), while the remaining 20% persisted as Cu(II) complexed to OM. However, in the third coarsest (i.e., Spring Creek), around 50% of the Cu had been reduced, forming Cu(I)-OM complexes, while the remainder was Cu(II)-OM complexes. Toxicity tests showed that survival of H. azteca and D. magna were significantly lower in suboxic treatments. Anoxic sediments triggered a near-complete transformation of Cu to sulfide minerals, reducing its toxicity.

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

A biohybrid strategy for enabling photoredox catalysis with low-energy light

Natural systems drive the high-energy reactions of photosynthesis with efficient and broadband energy capture. Transition-metal photocatalysts similarly convert light into chemical reactivity, and yet suffer from light-limited operation and require blue-to-UV excitation. In photosynthesis, both light capture and reactivity have been optimized by separation into distinct sites. In this work, inspired by this modular architecture, we synthesized a biohybrid photocatalyst by covalent attachment of the photosynthetic light-harvesting protein R-phycoerythrin (RPE) to the transition-metal photocatalyst tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy) 3 ] 2+ ). Spectroscopic investigation found that absorbed photoenergy was efficiently funneled from RPE to [Ru(bpy) 3 ] 2+ . The utility of the biohybrid photocatalyst was demonstrated via an increase in yields for a thiol-ene coupling reaction and a cysteinyl-desulfurization reaction, including recovered reactivity at red wavelengths where [Ru(bpy) 3 ] 2+ alone does not absorb.

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

Electrocatalytic oxygen evolution with pure and substituted M 6 (SR) 12 (M=Pd, Fe, Rh) complexes

The development of new technologies to generate fuels from water splitting requires highly active and cost-effective catalysts. Organometallic complexes have attracted considerable interests due to their scientific significance and their ability to efficiently photo- and electro-catalyze H 2 and O 2 evolution reactions. Here, we combine density functional theory (DFT) and computational electrochemical analysis to predict the oxygen evolution reaction (OER) activity of a series of organometallic complexes containing methyl thiol ligands and compare it to that of Ni complex. Here, we find that the OER activity versus the diameter of the hexagonal ring shows a maximum activity which corresponds to that of Ni complex. We also find an existence of linear correlations of the adsorption energies with the ring diameter of the oxidized complexes. In an effort to improve the OER activity of these complexes, we substitute a metal cation with Ni, and we show that Ni-doped complexes give rise to smaller overpotentials. The enhanced overpotential can be explained in terms of the overall affinity of active sites for reactive species resulting in a shift of their binding energies. Finally, we find that substituting Fe atoms into small organometallic Ni complex does not appear to have the same influence that has been observed in bulk materials. We believe these predictions will help guide catalyst design by identifying active and robust OER catalysts, capable to reduce the energy required for the anodic water oxidation. Reducing anodic overpotentials will help reduce the overall energy requirements of both H 2 evolution and CO 2 reduction systems.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Trace elements, oxidative status and antioxidant capacity as biomarkers in very low birth weight infants

Reference data on trace elements, oxidative status and antioxidants in very low birth weight infants (VLBW) are limited and need to be updated for use in clinical settings. Serum and urine of 30 VLBW infants (mean weight, 1167 g) at mean age of 23.8 (t0) and 37.8 (t1) days were analyzed. Cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), selenium (Se) and zinc (Zn), nitrate/nitrite (NOx), catalase (CAT), CuZnFeMn-superoxide dismutases (CuZnFeMn-SODs), total antioxidant capacity (SAC: sum of thiols, proteins, bilirubin, uric acid, β-beta-carotene, ascorbic acid, vitamin E) and total oxidative status (SOS: sum of lipo- and hydroperoxides) were determined. A higher urinary excretion of Cu and Zn was observed at t0 than at t1; while an increase in urine Cd was found at t1 respect to t0. A deficiency in serum levels of Cu and Zn was also found. A lower CAT activity, a higher total oxidants level (SOS) and a reduction of total antioxidant barriers (SAC) were observed in some infants. No Fe and Mn deficiency or Hg overload was found; also CuZnFeMn-SODs and NOx levels did not change. The findings showed that losses of trace elements and incomplete mineral body stores were more pronounced in the earlier life stage (at 23.8th day) than later on; moreover, antioxidant defenses were poor and lipo- and hydroperoxides were higher still at 5 weeks of infants’ life. - Highlights: • Trace elements, oxidants, antioxidants in very low birth weight infants are assessed. • Serum deficiency and urinary loss of Cu and Zn are observed soon after birth. • Oxidative stress and poor antioxidant capacity are found in the first weeks of life.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Development of copper thiolate organometallic compound as thermal sensitive coating for energy storage system safety

Safety and reliability are primary concerns for the deployment of lithium-ion batteries, especially in electric vehicles (EV) and larger-scale energy storage systems (ESS). Current technology in battery management systems (BMS) includes cell voltage monitoring and positioning temperature sensors in selected locations. For a system with hundreds to thousands of individual batteries, single-point temperature monitoring is inadequate to detect hot spots and cell overheating, which could lead to thermal runaway. Here, we have developed a temperature-sensitive copper-thiol compound that can be directly coated onto battery pouch foils to enable early detection of thermal runaway. Upon reaching specific temperatures, this compound releases a sulfur-containing detectable gas, which can be identified using chemically specific gas sensors to trigger an early warning signal. Such a signal propagate through air offers broad signal coverage and enables a more comprehensive approach to large-area temperature monitoring. The Cu-ethanethiol coating is designed to release volatile gases when the substrate surface temperature exceeds 70 °C, with continuous outgassing as the temperature increases. The compound is composed of Cu, S, Cl, hydrocarbons and trace amounts of oxygen. Upon heating, the oxidation state of Cu(I) transitions to Cu (II), accompanied by gas release. Thermogravimetric analysis coupled with mass spectrometry correlated well with the onset of gas release temperature and emission of sulfur-containing volatile gases. Additionally, an acrylic overcoat is applied to enhance the adhesion of the thermally sensitive compound film to the battery pouch foil. This coating is expected to offer an additional safety layer for ESS, alerting possible thermal runaway events before a failure occurs, thereby allowing sufficient time to implement a mitigation plan.

Early warning systems↗
DOE OSTI2019

Influence of side-chain length on long-term release kinetics from poly(2-oxazoline)-drug conjugate networks

Four drug-conjugated poly(2-alkyl-2-oxazoline) (PAOx) networks with different hydrophobicity were synthesized via copolymerization of either 2-methyl-, 2-ethyl-, 2-propyl- or 2-butyl-2-oxazoline with the functional monomer, 2-dec-9-enyl-2-oxazoline. The incorporation of a labile ester linkage between the polymer and the drug benazepril allowed for sustained drug release over periods of months with the release rates strongly depending on the hydrophobicity of the polymer pendant groups. Drug loading of 13 ± 2 wt% was used with 10 mol% crosslinking sites simply by tuning the thiol-ene stoichiometry. The networks exhibited negligible cell toxicity but cell repulsion was observed for hydrogels based on poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline) while those based on poly(2-n-propyl-2-oxazoline) and poly(2-n-butyl-2-oxaoline) showed cell adhesion. Furthermore, these results suggest that PAOx networks have great potential as drug delivery devices for long-lasting drug release applications.

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

Investigation of the structure, filler interaction and degradation of disulfide elastomers made by Reversible Radical Recombination Polymerization (R3P)

In this paper we report the synthesis and analysis of cyclic polydisulfides, their redox depolymerization as well as their interaction with carbon black. Cyclic poly(3,6-dioxa-1,8-octanedithiol)s (pDODT) were synthesized by Reversible Radical Recombination Polymerization (R3P). R3P is a scalable “green” polymerization process using triethylamine (TEA), H 2 O 2 and air for the polymerization of dithiol monomers. pDODTs were synthesized in 5 and 20 g batches. The effect of peroxide concentration (3, 5, 10, 20, 30%) was investigated. It was found that the molecular weights increased exponentially with increasing peroxide concentrations. At 30% peroxide concentration pDODTs with M n up to 400,000 g/mol and polydispersity of 2 were obtained. 700 and 800 MHz NMR were used for investigating the chemical structure of the polymers. The absence of thiol end group signals in polymers made with > 10wt % H 2 O 2 and M n < 100,000 g/mol, including a sample of a fractionated polymer with starting Mn = 600,000 g/mol, verified cyclic structures. Dithiothreitol reduced the polymers to monomer and a small percentage of oligomers. Carbon black was shown to increase the moduli of high molecular weight pDODTs. Swelling tests in chloroform showed that polymers made with 20 and 30w% peroxide swelled 14 and 10 times of their starting weight without dissolving, indicating chemical interaction between the polymers and carbon black. In conclusion, further analysis of these interesting elastomers, available at the 20 g scale, is in progress.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Quantitative site-specific reactivity profiling of S-nitrosylation in mouse skeletal muscle using cysteinyl peptide enrichment coupled with mass spectrometry

S-nitrosylation (SNO) is an important reversible thiol oxidation event that has been increasingly recognized for its role in cell signaling. While many proteins susceptible to S-nitrosylation have been reported, site-specific identification of physiologically relevant SNO modifications remains an analytical challenge due to the low-abundance and labile nature of the modification. Herein we present further improvement and optimization of the recently reported, resin-assisted cysteinyl peptide enrichment protocol for SNO identification and the extension of this application to mouse skeletal muscle to identify specific sites sensitive to S-nitrosylation by quantitative reactivity profiling. The results of our data indicate that the protein- and peptide-level enrichment protocols provide comparable specificity and coverage of SNO-peptide identifications. S-nitrosylation reactivity profiling was performed by quantitatively comparing the site-specific SNO modification levels in samples treated with S-nitrosoglutathione (GSNO), an NO donor, at two different physiologically relevant concentrations (i.e., 10 μM and 100 μM). The reactivity profiling experiments overall identified 489 SNO-modified cysteine sites from 197 proteins with the specificity of 95.2% at the unique-peptide-level based on the percentage of Cys-peptides. Among these sites, 260 sites from 135 proteins were observed with relatively high reactivity to S-nitrosylation; such SNO-sensitive sites are more likely to be physiologically relevant. Many of the SNO-sensitive proteins are preferentially localized in mitochondria, contractile fiber and actin cytoskeleton, suggesting the susceptibility of these subcellular compartments to redox regulation. Moreover, the SNO-sensitive proteins seem to be primarily involved in metabolic pathways, including TCA cycle, glycolysis/gluconeogenesis, glutathione metabolism, and fatty acid metabolism, suggesting the importance of redox regulation in muscle metabolism and insulin action.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Improving mitochondrial function with SS-31 reverses age-related redox stress and improves exercise tolerance in aged mice

Sarcopenia and exercise intolerance are major contributors to reduced quality of life in the elderly for which there are few effective treatments. We tested whether enhancing mitochondrial function and reducing mitochondrial oxidant production with SS-31 (elamipretide) could restore redox balance and improve skeletal muscle function in aged mice. Young (5 mo) and aged (26 mo) female C57BL/6Nia mice were treated for 8-weeks with 3 mg/kg/day SS-31. Mitochondrial function was assessed in vivo using 31P and optical spectroscopy. SS-31 reversed age-related decline in maximum mitochondrial ATP production (ATPmax) and coupling of oxidative phosphorylation (P/O). Despite the increased in vivo mitochondrial capacity, mitochondrial protein expression was either unchanged or reduced in the treated aged mice and respiration in permeabilized gastrocnemius (GAS) fibers was not different between the aged and aged+SS-31 mice. Treatment with SS-31 also restored redox homeostasis in the aged skeletal muscle. The glutathione redox status was more reduced and thiol redox proteomics indicated a robust reversal of cysteine S- glutathionylation post-translational modifications across the skeletal muscle proteome. The gastrocnemius in the age +SS-31 mice was more fatigue resistant with significantly greater mass compared to aged controls. This contributed to a significant increase in treadmill endurance compared to both pretreatment and untreated control values. These results demonstrate that the shift of redox homeostasis due to mitochondrial oxidant production in aged muscle is a key factor in energetic defects and exercise intolerance. Treatment with SS-31 restores redox homeostasis, improves mitochondrial quality, and increases exercise tolerance without an increase in mitochondrial content. Since elamipretide is currently in clinical trials these results indicate it may have direct translational value for improving exercise tolerance and quality of life in the elderly.

aging, fatigue, mitochondria, oxidative stress, sk↗
DOE OSTI2019

Ligands representing important functional groups of natural organic matter facilitate Fe redox transformations and resulting binding environments

Functional groups in natural organic matter have the potential to interact with and stabilize iron (Fe) redox species (ferric, ferrous) through complexation reactions. Iron complexes with cysteine, arginine and histidine are used to investigate the extent to which specific functional groups present in these amino acids might hinder the oxidation of Fe 2+ or promote the reduction of Fe 3+ . Iron complexes are synthesized by addition of ferrous or ferric salts to cysteine, arginine and histidine solutions at pH 7. The Fe-amino acid complexes are analysed using X-ray Absorption Spectroscopy (XAS), theoretical CTM4XAS (Charge Transfer Multiplet for XAS) calculations, and vibrational spectroscopy (FTIR and Raman). In addition, oxidation of the amino acids is determined by linear sweep voltammetry and chemical equilibrium modeling is used to predict the speciation of Fe in complexes with the amino acids. It is observed the extent of Fe redox transformation is affected by the electron donating capability of the ligand with which Fe reacts. In particular, the extent of Fe 3+ reduction is related to the oxidation of the ligand with 80, 14 and 0% Fe 3+ reduction by cysteine, arginine and histidine, respectively. Conversely, Fe 2+ is preserved by cysteine (80%) > arginine (77%) > histidine (62%). The chemical forms of Fe in these mixed Fe oxidation-state systems include Fe-organic complexes and Fe precipitates. XAS and vibrational spectroscopy indicate thiol-S and amino-N bind Fe in complexes with cysteine. While amino-N and guanidyl-N functional groups of arginine bind Fe, carboxylate-O binding and the formation of Fe precipitates are only observed when Fe 3+ is the predominant redox species. Whereas Fe precipitates seem to prevail in Fe(III)-histidine, distinct organic (Fe—O/N—C) and mineral (Fe—O—Fe) or mixed organic-mineral (Fe(O/N—C) x (O—Fe) y ) coordination environments occur in Fe(II)-histidine with ~60% Fe 2+ ; in either case, Fe—N(imidazole) binding is not evident. The ligand atoms to which Fe binds and the inherent reduction capacity of the ligand appear to mediate Fe redox transformations. The proportion of ferric iron (Fe 3+ ) seems to determine whether a precipitate forms. Consistent with spectroscopic data, chemical equilibrium modeling using experimental solution conditions and fractional Fe 2+ and Fe 3+ concentrations obtained from CTM4XAS predict the formation of Fe(II)- and Fe(III)-amino acid complexes and hydrolyzed Fe species; these calculations however also predict the formation of Fe oxide precipitates in all Fe complexes. The results presented in this study help to explain the co-occurrence of Fe 2+ and Fe 3+ in natural environments where organic matter is present. They also highlight the role specific organic functional groups play on the formation and stabilization of Fe(II, III)-organic complexes and precipitates, and thus on the Fe redox cycle which affects Fe bioavailability and mobility in terrestrial and subsurface environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Charge Retention by Organometallic Dications on Self-Assembled Monolayer Surfaces

Charge retention by mass-selected ruthenium trisbipyridine dications, or Ru(bpy)32+, soft-landed onto self-assembled monolayer (SAM) surfaces of 1H, 1H, 2H, 2H-perfluorodecane-1-thiol (FSAM), 11-mercaptoundecanoic acid (COOH-SAM), and 11-amino-1-undecanethiol (HSAM) on gold was examined using in situ time-resolved secondary ion mass spectrometry in a Fourier transform ion cyclotron resonance apparatus (FT-ICR SIMS). FT-ICR SIMS analysis was performed during ion soft-landing and for 8–15 hours after the ion beam was switched off. Our results demonstrate efficient retention of the doubly charged precursor ion on the FSAM and COOH-SAM surfaces manifested by the abundant Ru(bpy)32+ ions in the SIMS spectra. In contrast, only the singly charged Ru(bpy)3+ and Ru(bpy)2+ ions were observed on HSAM, indicating rapid loss of at least one charge by the deposited dications. The signal of Ru(bpy)32+ on COOH-SAM remained almost constant for more than 8 hours after the end of ion soft-landing, while a relatively fast decay followed by a plateau region was observed on the FSAM surface. However, we found that SIMS analysis of Ru(bpy)32+ ions soft-landed onto FSAM is complicated by facile ion-molecule reactivity occurring either on the surface or in the SIMS plume, making it difficult to accurately measure the charge reduction kinetics. Efficient retention of the doubly charged Ru(bpy)32+ ions on COOH-SAM is remarkably different from facile neutralization of protonated peptides deposited onto this surface reported in previous studies. Our results indicate different mechanisms of charge reduction of protonated molecules and permanent ions, such as Ru(bpy)32+, on SAM surfaces. Thus, we propose that proton loss is the major charge reduction channel for the protonated species, while electron transfer through the insulating SAM is responsible for the charge loss by permanent ions. Fundamental understanding of charge reduction phenomena is essential for controlled preparation of catalytically active substrates using ion soft-landing.

charge reduction↗
DOE OSTI2017

Surface-induced dissociation of methanol cations: A non-ergodic process

Here, dissociation of methanol molecular cations, CH 3 OH + , to CH 2 OH + on collision with a self-assembled monolayer surface of fluorinated alkyl thiol on gold 111 crystal has been studied at 12.5 eV collision energy. Two energetically and spatially distinct processes contribute to the dissociation process: one involving loss of very large amount of energy approaching the initial kinetic energy of the primary ions with scattering of fragment ions over a broad angular range between surface normal and surface parallel while the second process results from small amount of energy loss with fragment ions scattered over a narrow angular range close to the surface parallel. There is a third process with relatively small contribution to total dissociation whose characteristics are very similar to the low energy loss process. Finally, these results demonstrate that surface-induced dissociation of methanol cations via hydrogen loss is non-ergodic.

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

Modifying the resolving cysteine affects the structure and hydrogen peroxide reactivity of peroxiredoxin 2

Peroxiredoxin 2 (Prdx2) is a thiol peroxidase with an active site Cys (C52) that reacts rapidly with H 2 O 2 and other peroxides. The sulfenic acid product condenses with the resolving Cys (C172) to form a disulfide which is recycled by thioredoxin or GSH via mixed disulfide intermediates or undergoes hyperoxidation to the sulfinic acid. C172 lies near the C terminus, outside the active site. It is not established whether structural changes in this region, such as mixed disulfide formation, affect H 2 O 2 reactivity. To investigate, we designed mutants to cause minimal (C172S) or substantial (C172D and C172W) structural disruption. Stopped flow kinetics and mass spectrometry showed that mutation to Ser had minimal effect on rates of oxidation and hyperoxidation, whereas Asp and Trp decreased both by 100-fold. To relate to structural changes, we solved the crystal structures of reduced WT and C172S Prdx2. The WT structure is highly similar to that of the published hyperoxidized form. C172S is closely related but more flexible and as demonstrated by size exclusion chromatography and analytical ultracentrifugation, a weaker decamer. Size exclusion chromatography and analytical ultracentrifugation showed that the C172D and C172W mutants are also weaker decamers than WT, and small-angle X-ray scattering analysis indicated greater flexibility with partially unstructured regions consistent with C-terminal unfolding. We propose that these structural changes around C172 negatively impact the active site geometry to decrease reactivity with H 2 O 2 . This is relevant for Prdx turnover as intermediate mixed disulfides with C172 would also be disruptive and could potentially react with peroxides before resolution is complete.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Sorption kinetics and stability of conventional adsorbents for mercury remediation

In-situ remediation of mercury at numerous contaminated sites worldwide is a challenging and costly endeavor due to the persistency of this contaminant. In this study, we evaluated eight commercially available sorbent media ranging from carbon-, clays- and silica-based materials (PBC– Biochar, eSorb – Sorbster, nsPAC – Powdered Activated Carbon, fsPAC – Powdered Activated Carbon with Mackinawite, F300 – Filtrasorb 300, Si-SH – Silica Thiol, eBind – RemBind, Q-Clay – Organoclay PM-199), for their effectiveness in sorbing mercury (Hg 2+ ) and mercury complexed with dissolved organic matter (Hg-DOM). Under the chosen experimental conditions of this study, results showed that in the absence of DOM, the kinetic rates of Hg 2+ sorption onto the evaluated sorbents were in the order of 0.31 min-1 (Si-SH) to 2.98 min -1 (nsPAC), whereas in the presence of DOM, the rates varied from 0.16 min-1 (F300) to 0.95 min -1 (nsPAC). The measured sorption capacity for Hg 2+ in the absence of DOM varied from 3.02 mg/g (Q-Clay) to 35.15 mg/g (Si-SH), whereas in the presence of DOM, calculated partition coefficient (KD) ranged from 69.7 mL/g (Q-Clay) to 41,510 mL/g (Si-SH). Furthermore, kinetic data suggest liquid film diffusion was the rate-limiting steps governing mercury sorption onto the studied media. Overall, the obtained study parameters (kinetics/isotherm) are particularly important in informing robust engineering designs for deployment of the vast majority of evaluated sorbents. Thus, sorbent-based strategies offer viable solutions for cost-effective cleanup of mercury at industrially contaminated sites.

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

Mutation of an active site-adjacent residue in VIM indirectly dictates interactions with and blunts inhibition by D-captopril

Activity assays and X-ray crystallographic studies were undertaken to elucidate the inhibitory mechanism of captopril stereoisomers on Verona integron-encoded metallo-β-lactamases, specifically VIM-20, VIM-31, and VIM-15. All three VIM-2-like variants (VIM-20, VIM-31, and VIM-15) and VIM-2 expressed in Escherichia coli exhibited catalytic activity with comparable steady-state kinetic parameters. Among the tested thiol drugs (L- and D-captopril, D,L-thiorphan, and 2,3-dimercaprol), IC50 analyses indicated that D-captopril and 2,3-dimercaprol were more potent inhibitors against the VIM enzymes examined in this study. Notably, the IC50 value of D-captopril against VIM-31 was an exception, closely resembling that of L-captopril. To elucidate this exceptional inhibitory potency of D-captopril and its binding mode in the active site of VIM-31, high-resolution crystal structures of VIM-20, VIM-31, and VIM-15 in complex with both L- and D-captopril are reported. These findings will help evaluate whether the identified potent inhibitor D-captopril could be further developed as a pan inhibitor targeting the VIM-family enzymes.

Silwal, Surendra Bikram↗
DOE OSTI2015

Luminescent hybrid lanthanide sulfates and lanthanide sulfonate-carboxylates with 1,10-phenanthroline involving in-situ oxidation of 2-mercaptonbenzoic acid

A series of lanthanide sulfates and lanthanide sulfonate-carboxylates, [Ln{sub 2}(phen){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O){sub 2}]{sub n} (I:Ln=Nd(1a), Sm(1b), Eu(1c), phen=1,10-phenanthroline) and [Ln(phen)(2-SBA)(BZA)]{sub n} (II: Ln=Sm(2a), Eu(2b), Dy(2c), 2-SBA=2-sulfobenzoate, BZA=benzoate) have been hydrothermally synthesized from lanthanide oxide, 2-mercaptonbenzoic acid with phen as auxiliary ligand and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, TG analyses and luminescence spectroscopy. Interestingly, SO{sub 4}{sup 2−} anions in I came from the in situ deep oxidation of thiol groups of 2-mercaptonbenzoic acid while 2-sulfobenzoate and benzoate ligands in II from the middle oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. Compounds I are organic–inorganic hybrid lanthanide sulfates, which have rare one-dimensional column-like structures. Complexes II are binuclear lanthanide sulfonate-carboxylates with 2-sulfobenzoate and benzoate as bridges and 1,10-phenanthroline as terminal. Photoluminescence studies reveal that complexes I and II exhibit strong lanthanide characteristic emission bands in the solid state at room temperature. - Graphical abstract: Lanthanide sulfates and lanthanide sulfonate-carboxylates have been hydrothermally synthesized. Interestingly, sulfate anions, 2-sulfobenzoate and benzoate ligands came from the in situ oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. - Highlights: • In situ oxidation and desulfuration reactions of 2-mercaptonbenzoic acid. • The organic–inorganic hybrid lanthanide sulfates with one-dimensional column-like structure. • The dinuclear lanthanide sulfonate-carboxylates. • The emission spectra exhibit the characteristic transition of {sup 5}D{sub 0}→{sup 7}F{sub J} (J=0–4) of the Eu(III)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗