Enhanced sorption and destruction of PFAS by biochar-enabled advanced reduction process.

The biochar-enabled advanced reduction process (ARP) was developed for enhanced sorption (by biochar) and destruction of PFAS (by ARP) in water. First, the biochar (BC) was functionalized by iron oxide (FeO), zero valent iron (ZVI), and chitosan (chi) to produce four biochars (BC, FeO-BC, ZVI-chi-BC, and chi-BC) with improved physicochemical properties (e.g.

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

Methyl-coenzyme M reductase (MCR) is a multi-subunit (αβγ) enzyme responsible for methane formation via its unique F 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.

Biochar and surfactant synergistically enhanced PFAS destruction in UV/sulfite system at neutral pH.

The UV/sulfite-based advanced reduction process (ARP) emerges as an effective strategy to combat per- and polyfluoroalkyl substances (PFAS) pollution in water. Yet, the UV/sulfite-ARP typically operates at highly alkaline conditions (e.g.

The Active-Site [4Fe-4S] Cluster in the Isoprenoid Biosynthesis Enzyme IspH Adopts Unexpected Redox States during Ligand Binding and Catalysis.

()-4-Hydroxy-3-methylbut-2-enyl diphosphate reductase, or IspH (formerly known as LytB), catalyzes the terminal step of the bacterial methylerythritol phosphate (MEP) pathway for isoprene synthesis. This step converts ()-4-hydroxy-3-methylbut-2-enyl diphosphate (HMBPP) into one of two possible isomeric products, either isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). This reaction involves the removal of the C4 hydroxyl group of HMBPP and addition of two electrons.

The two-electron reduced A cluster in acetyl-CoA synthase: Preparation, characteristics and mechanistic implications.

Acetyl-CoA synthase (ACS) is a central enzyme in the carbon and energy metabolism of certain anaerobic species of bacteria and archaea that catalyzes the direct synthesis and cleavage of the acetyl CC bond of acetyl-CoA by an unusual enzymatic mechanism of special interest for its use of organonickel intermediates. An FeS cluster associated with a proximal, reactive Ni and distal spectator Ni comprise the active site metal complex, known as the A cluster. Experimental and theoretical methods have uncovered much about the ACS mechanism, but have also opened new unanswered questions about the structure and reactivity of the A cluster in various intermediate forms.

Expression of divergent methyl/alkyl coenzyme M reductases from uncultured archaea.

Methanogens and anaerobic methane-oxidizing archaea (ANME) are important players in the global carbon cycle. Methyl-coenzyme M reductase (MCR) is a key enzyme in methane metabolism, catalyzing the last step in methanogenesis and the first step in anaerobic methane oxidation. Divergent mcr and mcr-like genes have recently been identified in uncultured archaeal lineages.

Synthesis, characterization, and electrocatalytic activity of bis(pyridylimino)isoindoline Cu(II) and Ni(II) complexes.

Two NNN pincer complexes of Cu(ii) and Ni(ii) with BPIMe- [BPIMe- = 1,3-bis((6-methylpyridin-2-yl)imino)isoindolin-2-ide] have been prepared and characterized structurally, spectroscopically, and electrochemically. The single crystal structures of the two complexes confirmed their distorted trigonal bipyramidal geometry attained by three equatorial N-atoms from the ligand and two axially positioned water molecules to give [Cu(BPIMe)(H2O)2]ClO4 and [Ni(BPIMe)(H2O)2]ClO4. Electrochemical studies of Cu(ii) and Ni(ii) complexes have been performed in acetonitrile to identify metal-based and ligand-based redox activity.

Methanosarcina acetivorans contains a functional ISC system for iron-sulfur cluster biogenesis.

Background: The production of methane by methanogens is dependent on numerous iron-sulfur (Fe-S) cluster proteins; yet, the machinery involved in Fe-S cluster biogenesis in methanogens remains largely unknown. Methanogen genomes encode uncharacterized homologs of the core components of the ISC (IscS and IscU) and SUF (SufBC) Fe-S cluster biogenesis systems found in bacteria and eukaryotes. Methanosarcina acetivorans contains three iscSU and two sufCB gene clusters.

Quantitative, real-time in vivo tracking of magnetic nanoparticles using multispectral optoacoustic tomography (MSOT) imaging.

The goal of this work was to demonstrate real-time tracking of in vivo nanoparticle concentrations utilizing multispectral optoacoustic tomography (MSOT). Combining the high contrast of optical imaging with the high resolution of ultrasound imaging, MSOT was utilized for non-invasive, real-time tomographic imaging of particles in mice and the results calibrated against analysis of tissue samples with electron paramagnetic resonance (EPR) spectroscopy. In a longitudinal study, the pharmacokinetics (pK) and biodistribution of Cyanine-7 (Cy7) conjugated superparamagnetic iron oxide nanoparticles (Cy7-SPIONs) were monitored after intravenous administration into the tail vein of healthy B6-albino mice.

Photoreduction of CHCl in Aqueous SPEEK/HCO Solutions Involving Free Radicals.

Exposure of sulfonated poly(ether etherketone), SPEEK, in aqueous solutions to 350 nm photons induced reduction of CHCl to CHCl and chloride ions in the presence of HCOH/HCO buffers or poly(vinyl alcohol), PVA. The kinetics of the SPEEK-sensitized photoreaction was characterized by quantum yields of halide ion formation, ϕ(Cl), evaluated from in situ determinations of [Cl]. Particularly efficient reductions took place when formate buffers served as H atom donors in the absence of air and with excess CHCl.

Assembly of Methyl Coenzyme M Reductase in the Methanogenic Archaeon Methanococcus maripaludis.

Methyl coenzyme M reductase (MCR) is a complex enzyme that catalyzes the final step in biological methanogenesis. To better understand its assembly, the recombinant MCR from the thermophile (rMCR) was expressed in the mesophile The rMCR was posttranslationally modified correctly and contained McrD and the unique nickel tetrapyrrole coenzyme F Subunits of the native (MCR) were largely absent, suggesting that the recombinant enzyme was formed by an assembly of cotranscribed subunits. Strong support for this hypothesis was obtained by expressing a chimeric operon comprising the His-tagged from and the from in The His-tagged purified rMCR then contained the McrA and the McrBDG.

Mode of action uncovered for the specific reduction of methane emissions from ruminants by the small molecule 3-nitrooxypropanol.

Ruminants, such as cows, sheep, and goats, predominantly ferment in their rumen plant material to acetate, propionate, butyrate, CO2, and methane. Whereas the short fatty acids are absorbed and metabolized by the animals, the greenhouse gas methane escapes via eructation and breathing of the animals into the atmosphere. Along with the methane, up to 12% of the gross energy content of the feedstock is lost.

Spectroscopic and redox studies of valence-delocalized [Fe2S2](+) centers in thioredoxin-like ferredoxins.

Reduced forms of the C56S and C60S variants of the thioredoxin-like Clostridium pasteurianum [Fe2S2] ferredoxin (CpFd) provide the only known examples of valence-delocalized [Fe2S2](+) clusters, which constitute a fundamental building block of all higher nuclearity Fe-S clusters. In this work, we have revisited earlier work on the CpFd variants and carried out redox and spectroscopic studies on the [Fe2S2](2+,+) centers in wild-type and equivalent variants of the highly homologous and structurally characterized Aquifex aeolicus ferredoxin 4 (AaeFd4) using EPR, UV-visible-NIR absorption, CD and variable-temperature MCD, and protein-film electrochemistry. The results indicate that the [Fe2S2](+) centers in the equivalent AaeFd4 and CpFd variants reversibly interconvert between similar valence-localized S = 1/2 and valence-delocalized S = 9/2 forms as a function of pH, with pKa values in the range 8.

Elucidating the process of activation of methyl-coenzyme M reductase.

Methyl-coenzyme M reductase (MCR) catalyzes the reversible reduction of methyl-coenzyme M (CH3-S-CoM) and coenzyme B (HS-CoB) to methane and heterodisulfide CoM-S-S-CoB (HDS). MCR contains the hydroporphinoid nickel complex coenzyme F430 in its active site, and the Ni center has to be in its Ni(I) valence state for the enzyme to be active. Until now, no in vitro method that fully converted the inactive MCRsilent-Ni(II) form to the active MCRred1-Ni(I) form has been described.

Different modes of carbon monoxide binding to acetyl-CoA synthase and the role of a conserved phenylalanine in the coordination environment of nickel.

Acetyl-CoA synthase (ACS) catalyzes the reversible condensation of CO and CH3 units at a unique Ni-Fe cluster, the A cluster, to form an acetyl-Ni intermediate that subsequently reacts with CoA to produce acetyl-CoA. ACS is a component of the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) in Archaea and CO dehydrogenase/ACS (CODH/ACS) in bacteria; in both systems, intraprotein CO channeling takes place between the CODH and ACS active sites. Previous studies indicated that protein conformational changes control the chemical reactivity of the A cluster and suggested the involvement of a conserved Phe residue that moves concomitantly into and out of the coordination environment of Ni.

A closer look at the spectroscopic properties of possible reaction intermediates in wild-type and mutant (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase.

(E)-4-Hydroxy-3-methylbut-2-enyl diphosphate reductase (IspH or LytB) catalyzes the terminal step of the MEP/DOXP pathway where it converts (E)-4-hydroxy-3-methylbut-2-enyl diphosphate (HMBPP) into the two products, isopentenyl diphosphate and dimethylallyl diphosphate. The reaction involves the reductive elimination of the C4 hydroxyl group, using a total of two electrons. Here we show that the active form of IspH contains a [4Fe-4S] cluster and not the [3Fe-4S] form.

Hydrolysis of glycosides with microgel catalysts.

A dormant macromolecular catalyst was prepared by polymerization of an aqueous styrene-butyl acrylate miniemulsion in the presence of a new polymerizable pentadentate ligand. The catalyst was activated by binding Cu(II) ions to the ligand site and then explored for its ability to hydrolyze glycosidic bonds in alkaline solution. The performance was correlated to the catalytic activity shown by low molecular weight analogs.

Log-scale dose response of inhibitors on a chip.

We demonstrate the accommodation of log-scale concentration gradients of inhibitors on a single microfluidic chip with a semidirect dilution capability of reagents for the determination of the half-inhibitory concentration or IC(50). The chip provides a unique tool for hosting a wide-range of concentration gradient for studies that require an equal distribution of measuring points on a logarithmic scale. Using Matrix metalloproteinase IX and three of its inhibitors, marimastat, batimastat, and CP471474, we evaluated the IC(50) of each inhibitor with a single experiment.

Creation of stepwise concentration gradient in picoliter droplets for parallel reactions of matrix metalloproteinase II and IX.

We present a new methodology for generating a stepwise concentration gradient in a series of microdroplets by using monolithic micro valves that act as "faucets" in micrometer-scale. A distinct concentration gradient of a substrate was generated for the determination of the kinetic parameters of two different enzymes using only 10 picoliter-scale droplets. With a single experiment on a chip, we obtained K(M) and k(cat) values of matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9), and compared the catalytic competence of the two enzymes.

Methyl-coenzyme M reductase from Methanothermobacter marburgensis.

Methyl-coenzyme M reductase catalyzes the reversible synthesis of methane from methyl-coenzyme M in methanogenic and ANME-1 and ANME-2 Archaea. The purification procedure for methyl-coenzyme M reductase from Methanothermobacter marburgensis is described. The procedure is an accumulation of almost 30 years of research on MCR starting with the first purification described by Ellefson and Wolfe (Ellefson, W.

Regenerable Fe-Mn-ZnO/SiO2 sorbents for room temperature removal of H2S from fuel reformates: performance, active sites, Operando studies.

Fe- and Mn-promoted H(2)S sorbents Fe(x)-Mn(y)-Zn(1-x-y)O/SiO(2) (x, y = 0, 0.025) for desulfurization of model fuel reformates at room temperature were prepared, tested and characterized. Sulfur uptake capacity at 25 °C significantly exceeds that of both commercial unsupported ZnO sorbents and un-promoted supported ZnO/SiO(2) sorbents.

Paramagnetic intermediates of (E)-4-hydroxy-3-methylbut-2-enyl diphosphate synthase (GcpE/IspG) under steady-state and pre-steady-state conditions.

(E)-4-Hydroxy-3-methylbut-2-enyl diphosphate synthase (GcpE/IspG) converts 2-C-methyl-D-erythritol-2,4-cyclodiphosphate (MEcPP) into (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP) in the penultimate step of the methyl-erythritol phosphate (MEP) pathway for isoprene biosynthesis. MEcPP is a cyclic compound and the reaction involves the opening of the ring and removal of the C3 hydroxyl group consuming a total of two electrons. The enzyme contains a single [4Fe-4S] cluster in its active site.

Tight coupling of partial reactions in the acetyl-CoA decarbonylase/synthase (ACDS) multienzyme complex from Methanosarcina thermophila: acetyl C-C bond fragmentation at the a cluster promoted by protein conformational changes.

Direct synthesis and cleavage of acetyl-CoA are carried out by the bifunctional CO dehydrogenase/acetyl-CoA synthase enzyme in anaerobic bacteria and by the acetyl-CoA decarbonylase/synthase (ACDS) multienzyme complex in Archaea. In both systems, a nickel- and Fe/S-containing active site metal center, the A cluster, catalyzes acetyl C-C bond formation/breakdown. Carbonyl group exchange of [1-(14)C]acetyl-CoA with unlabeled CO, a hallmark of CODH/ACS, is weakly active in ACDS, and exchange with CO(2) was up to 350 times faster, indicating tight coupling of CO release at the A cluster to CO oxidation to CO(2) at the C cluster in CO dehydrogenase.

Determination of kinetic parameters, Km and kcat, with a single experiment on a chip.

We have demonstrated a multistep enzyme reaction on a chip to determine the key kinetic parameters of enzyme reaction. We designed and fabricated a fully integrated microfluidic chip to have sample metering, mixing, and incubation functionalities. The chip generates a gradient of reagent concentrations in 11 parallel processors.