DOCSLIB.ORG

Hydroxylamine As an Intermediate in Ammonia Oxidation by Globally Abundant Marine Archaea

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Hydroxylamine As an Intermediate in Ammonia Oxidation by Globally Abundant Marine Archaea Hydroxylamine as an intermediate in ammonia oxidation by globally abundant marine archaea Neeraja Vajralaa,1, Willm Martens-Habbenab,1, Luis A. Sayavedra-Sotoa, Andrew Schauerc, Peter J. Bottomleyd, David A. Stahlb, and Daniel J. Arpa,2 Departments of aBotany and Plant Pathology and dMicrobiology, Oregon State University, Corvallis, OR 97331; and Departments of bCivil and Environmental Engineering and cEarth and Space Science, University of Washington, Seattle, WA 98195 Edited by Edward F. DeLong, Massachusetts Institute of Technology, Cambridge, MA, and approved December 7, 2012 (received for review August 17, 2012) The ammonia-oxidizing archaea have recently been recognized as or cytochromes c554 and cM552 critical for energy conversion in a significant component of many microbial communities in the AOB (8–15). Thus, either the product of NH3 oxidation is not biosphere. Although the overall stoichiometry of archaeal chemo- NH2OH or, alternatively, these phylogenetically deeply branch- − autotrophic growth via ammonia (NH3) oxidation to nitrite (NO2 ) ing thaumarchaea use a novel biochemistry for NH2OH oxida- is superficially similar to the ammonia-oxidizing bacteria, genome tion and electron transfer (8). sequence analyses point to a completely unique biochemistry. The In an attempt to gain further insights into the biochemistry and only genomic signature linking the bacterial and archaeal bioche- physiology of these unique archaeal nitrifiers, we here investigated Nitrosopumilus maritimus mistries of NH3 oxidation is a highly divergent homolog of the the role of NH2OH in metabolism. ammonia monooxygenase (AMO). Although the presumptive These studies were complicated by the extremely oligotrophic product of the putative AMO is hydroxylamine (NH2OH), the ab- character of this organism contributing to very low cell densities sence of genes encoding a recognizable ammonia-oxidizing bacte- in culture (16). To overcome the challenge of working with low ria-like hydroxylamine oxidoreductase complex necessitates either cell density cultures of N. maritimus, we established a method to a novel enzyme for the oxidation of NH2OH or an initial oxidation concentrate cells on nylon membrane filters such that the cells − product other than NH2OH. We now show through combined remained competent for NH3-dependent NO2 formation and physiological and stable isotope tracer analyses that NH2OH is oxygen (O2) uptake. This method enabled us to carry out relatively SCIENCES both produced and consumed during the oxidation of NH3 to short duration physiological studies and stable isotope tracer ENVIRONMENTAL − NO2 by Nitrosopumilus maritimus, that consumption is coupled experiments directed at determining if N. maritimus can oxidize − to energy conversion, and that NH2OH is the most probable prod- exogenous NH2OH to NO2 while consuming O2 and producing uct of the archaeal AMO homolog. Thus, despite their deep phy- ATP, and if NH2OH is an intermediate in NH3 oxidation pathway logenetic divergence, initial oxidation of NH3 by bacteria and of N. maritimus. archaea appears mechanistically similar. They however diverge bio- chemically at the point of oxidation of NH2OH, the archaea possibly Results − catalyzing NH2OH oxidation using a novel enzyme complex. N. maritimus Oxidizes NH2OH to NO2 . The apparent lack of genes encoding a recognizable AOB-like HAO complex in the genome − N. maritimus icrobial oxidation of ammonia (NH ) to nitrite (NO ), the of has generated considerable interest in the 3 2 fi Mfirst step in nitrification, plays a central role in the global pathway of NH3 oxidation in AOA (8). Because puri cation and cycling of nitrogen. Recent studies have established that marine direct biochemical characterization of AMO enzymes has thus far been unsuccessful, we aimed to determine if N. maritimus and terrestrial representatives of an abundant group of archaea, − could convert NH2OH to NO2 . To determine if N. maritimus now classified as Thaumarchaeota, are autotrophic NH3 oxidizers − – can oxidize NH2OH to NO2 , it was necessary to expose the (1 5). Despite increasing evidence that ammonia-oxidizing N. maritimus + archaea (AOA) generally outnumber ammonia-oxidizing bacte- cells to NH2OH in the absence of the NH4 used to grow the culture. Hence, a technique was developed to con- ria (AOB), and likely nitrify in most natural environments, very μ fi little is known about their physiology or supporting biochemistry centrate the cells onto 0.2- m pore size nylon membrane lters (6, 7). Genome sequence analyses have pointed to a unique using a vacuum manifold system. The manifold system allowed simultaneous filtration of several liters of culture. In addition to pathway for NH3 oxidation, likely using copper as a major redox + active metal, and coupled to a variant of the hydroxypropionate/ concentrating the cells and separating them from residual NH4 in the medium, the nylon membranes served as a solid support hydroxybutyrate cycle (8). However, the only genome sequence for convenient handling of concentrated cells in subsequent in- feature that associates the archaeal pathway for NH oxidation 3 cubation assays. The membrane-associated N. maritimus cells ac- with that of the better characterized AOB is a divergent variant tively oxidized NH for several hours. of the ammonia monooxygenase (AMO), which may or may not 3 To investigate whether NH2OH can be oxidized by N. maritimus, be a functional equivalent of the bacterial AMO. Thus, the − a series of short-term NO accumulation assays was conducted, supporting biochemistry of a biogeochemically significant group 2 in which membrane-associated N. maritimus cells were exposed of microorganisms remains unresolved (8, 9). to various concentrations of NH OH. Irrespective of the initial Among the AOB, as represented by the model organism 2 Nitrosomonas europaea,NH3 is first oxidized to hydroxylamine (NH OH) by AMO, an enzyme composed of three subunits 2 Author contributions: N.V., W.M.-H., L.A.S.-S., P.J.B., D.A.S., and D.J.A. designed research; encoded by amoC, amoA, and amoB genes (7). NH2OH is sub- − N.V., W.M.-H., L.A.S.-S., and D.A.S. performed research; A.S. contributed new reagents/ sequently oxidized to NO2 by the hydroxylamine oxidoreductase analytic tools; N.V., W.M.-H., L.A.S.-S., A.S., P.J.B., D.A.S., and D.J.A. analyzed data; and (HAO) (7), a heme-rich enzyme encoded by the hao gene (7). Of N.V., W.M.-H., L.A.S.-S., and D.A.S. wrote the paper. fl the four electrons released from the oxidation of NH2OH to The authors declare no con ict of interest. − NO2 , two are transferred to the terminal oxidase for respiratory This article is a PNAS Direct Submission. purposes and two are transferred to AMO for further oxidation 1N.V. and W.M.-H. contributed equally to this work. of NH3 (7). Although all available genome sequences for the 2To whom correspondence should be addressed. E-mail: [email protected]. amoB amoC AOA contain homologs of the bacterial AMO ( , , This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. and amoA), there are no obvious homologs of AOB-like HAO, 1073/pnas.1214272110/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1214272110 PNAS Early Edition | 1of6 Downloaded by guest on September 25, 2021 concentration of NH2OH (50–200 μM), N. maritimus oxidized − ∼50 μMNH2OH to NO2 over 20 h (Fig. 1). During the first 30 min of exposure to 200 μMNH2OH, the rate of NH2OH- − dependent NO2 production was equal to the rate of NH3-de- − pendent NO2 production [0.19 ± 0.01 μmol/(min × mg protein)]. With longer incubation times, the rate of NH2OH oxidation de- creased gradually and finally stopped after accumulation of − ∼50 μMofNO2 (Fig. 1). Addition of 1 mM NH2OH led to a − complete inhibition of the NO2 formation (Fig. 1), reflecting a toxicity at higher concentrations also observed for AOB (17). Attempts to grow N. maritimus on NH2OH as sole energy source failed as previously observed in N. europaea (18). Acetylene (C2H2) (19) and allylthiourea (ATU) (20) are specific inhibitors of NH3 oxidation by AMO in AOB and AOA (19–21). In the present work, the ability of N. maritimus to oxidize NH3 or NH2OH in presence of either C2H2 or ATU was analyzed − by monitoring NO2 accumulation. C2H2 (0.1%) was added to the headspace of sealed bottles containing membrane-attached N. maritimus cells in synthetic crenarchaeota medium (SCM) con- + taining either NH4 or NH2OH. C2H2 completely inhibited NH3- − dependent NO2 accumulation but had no effect on NH2OH- − dependent NO2 production (Fig. S1 A and B)aspreviously observed in N. europaea (19). Similarly, the addition of ATU also − inhibited NH3-dependent NO2 production but did not inhibit − NH2OH-dependent NO2 production (Fig. S1 A and B)(20). These results clearly indicate that N. maritimus can oxidize Fig. 2. Stoichiometry of NH2OH oxidation in N. maritimus.O2 uptake (solid − NH2OH and its oxidation is independent of the AMO activity squares), NH2OH consumed (open circles), NO2 produced (gray triangles); (Fig. S1 A and B). Data are means of triplicates, with variation of less than 10%. Incubations were carried out for 8 min while the conditions were at optimum (i.e., the NH2OH Oxidation Is Coupled to O2 Uptake in N. maritimus. Further unavoidable degradation of NH2OH did not interfere with the stoichiome- experiments were conducted to determine if oxidation of NH2OH try). The experiment was repeated at least three times and produced similar − results. Error bars represent SEM. to NO2 by N. maritimus is accompanied by consumption of a stoichiometric amount of O2. To test this, NH2OH consumption, − O2 uptake, and NO2 accumulation were independently deter- 1NH3:1.5 O2 previously reported for both the bacterial and ar- mined (Fig. 2). The rate of NH2OH-dependent O2 consumption − by N. maritimus remained constant for 8 min at a rate of 0.20 ± chaeal oxidation of NH3 to NO2 (16, 23).
Load more

Recommended publications
  • A Biochemical Rationale for the Discrete Behavior of Nitroxyl and Nitric Oxide in the Cardiovascular System
    A biochemical rationale for the discrete behavior of nitroxyl and nitric oxide in the cardiovascular system Katrina M. Miranda*†‡, Nazareno Paolocci§, Tatsuo Katori§, Douglas D. Thomas*, Eleonora Ford¶, Michael D. Bartbergerʈ, Michael G. Espey*, David A. Kass§, Martin Feelisch**, Jon M. Fukuto¶, and David A. Wink*† *Radiation Biology Branch, Building 10, Room B3-B69, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; §Division of Cardiology, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, MD 21287; ¶Department of Molecular and Medical Pharmacology, Center for the Health Sciences, University of California, Los Angeles, CA 90095; ʈDepartment of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095; and **Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130 Edited by Louis J. Ignarro, University of California School of Medicine, Los Angeles, CA, and approved May 20, 2003 (received for review February 20, 2003) The redox siblings nitroxyl (HNO) and nitric oxide (NO) have often cellular thiol functions (14, 15). Conversely, NO reacts only indi- been assumed to undergo casual redox reactions in biological sys- rectly with thiols after RNOS formation (17). tems. However, several recent studies have demonstrated distinct Contrasting effects are also apparent in vivo or ex vivo,for pharmacological effects for donors of these two species. Here, infu- example in models of ischemia reperfusion injury. Exposure to NO sion of the HNO donor Angeli’s salt into normal dogs resulted in donors at the onset of reperfusion provides protection against elevated plasma levels of calcitonin gene-related peptide, whereas reperfusion injury in the heart and other organs (18–20).
    [Show full text]
  • Kinetics of Oxidation of Hydrazine & Hydroxylamine by N
    Indian Journal of Chemistry VoL I5A, AUQust 1977, pp. 713-715 Kinetics of Oxidation of Hydrazine & Hydroxylamine by N-Chlorobenzamide B. S. RAWAT & M. C. AGRAWAL Department of Chemistry, Harcourt Butler Technological Institute, Kanpur 208002 Received 16 December 1976; accepted 28 February 1977 The rates of oxidation of hydrazine and hydroxylamine by N-chlorobenzamide (NCB) have been measured in hydrochloric acid media. The reactions follow identical kinetics. being first order each in [NCB]. [H+] and [CI-] and show independent nature to the reducing substrates. Added salt and solvent effects are negligible. Molecular chlorine obtained from the reaction of NCB and HCI has been found to be the effective oxidant. XIDATION of hydrazine- and hydroxylamine- excess of NCB at 40°. The results conformed to by a variety of oxidants in aqueous solutions the reactions (1 and 2), O has been studied. In general, hydrazine is N2H4+2C6HsCONHCI = N2+2C6HsCONH2+2HCl quantitatively converted into nitrogen but other ... (1) products such as ammonia and hydrazoic acid have also been reported. 2NH20H+CaHsCONHCI = N2+C6HsCONH2 It was interesting that the oxidation of hydroxyl- +2H20 +HCl ... (2) amine by ferricyanide" showed a variable stoichio- and are in accord with the results of Singh and metry depending upon the relative concentrations coworkers+ who have experimentally obtained nitro- of the reactants. Both hydrazine and hydroxyl- gen and benzamide as the end-products of the amine were quantitatively estimated in strong acidic reaction. solutions by N-chlorobenzamide4• In this paper the results of the kinetics of oxidation of hydrazine Results and hydroxylamine by N-chlorobenzamide (NCB) Effects of varyi1lg [NeB] and [substrates]- are recorded and a suitable mechanism is proposed.
    [Show full text]
  • Molecule Based on Evans Blue Confers Superior Pharmacokinetics and Transforms Drugs to Theranostic Agents
    Novel “Add-On” Molecule Based on Evans Blue Confers Superior Pharmacokinetics and Transforms Drugs to Theranostic Agents Haojun Chen*1,2, Orit Jacobson*2, Gang Niu2, Ido D. Weiss3, Dale O. Kiesewetter2, Yi Liu2, Ying Ma2, Hua Wu1, and Xiaoyuan Chen2 1Department of Nuclear Medicine, Xiamen Cancer Hospital of the First Affiliated Hospital of Xiamen University, Xiamen, China; 2Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland; and 3Laboratory of Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland One of the major design considerations for a drug is its The goal of drug development is to achieve high activity and pharmacokinetics in the blood. A drug with a short half-life in specificity for a desired biologic target. However, many potential the blood is less available at a target organ. Such a limitation pharmaceuticals that meet these criteria fail as therapeutics because dictates treatment with either high doses or more frequent doses, of unfavorable pharmacokinetics, in particular, rapid blood clearance, both of which may increase the likelihood of undesirable side effects. To address the need for additional methods to improve which prevents the achievement of therapeutic concentrations. For the blood half-life of drugs and molecular imaging agents, we some drugs, the administration of large or frequently repeated doses developed an “add-on” molecule that contains 3 groups: a trun- is required to achieve and maintain therapeutic levels (1) but can, in cated Evans blue dye molecule that binds to albumin with a low turn, increase the probability of undesired side effects.
    [Show full text]
  • Hidden Complexities in the Reaction of H2O2 and HNO Revealed by Ab Initio Quantum Chemical Cite This: Phys
    PCCP PAPER Hidden complexities in the reaction of H2O2 and HNO revealed by ab initio quantum chemical Cite this: Phys. Chem. Chem. Phys., 2017, 19, 29549 investigations† Daniel Beckett, Marc Edelmann, Jonathan D. Raff and Krishnan Raghavachari* Nitroxyl (HNO) and hydrogen peroxide have both been implicated in a variety of reactions relevant to environmental and physiological processes and may contribute to a unique, unexplored, pathway for the production of nitrous acid (HONO) in soil. To investigate the potential for this reaction, we report an in-depth investigation of the reaction pathway of H2O2 and HNO forming HONO and water. We find the breaking of the peroxide bond and a coupled proton transfer in the first step leads to hydrogen nitryl (HNO2) and an endogenous water, with an extrapolated NEVPT2 (multireference perturbation theory) barrier of 29.3 kcal molÀ1. The first transition state is shown to possess diradical character linking the far peroxide oxygen to the bridging, reacting, peroxide oxygen. The energy of this first step, when calculated using hybrid density functional theory, is shown to depend heavily on the amount of Hartree–Fock exchange in the functional, with higher amounts leading to a higher barrier and more diradical character. Additionally, high amounts of spin contamination cause CCSD(T) to significantly overestimate the TS1 barrier with a value of 36.2 kcal molÀ1 when using the stable UHF wavefunction as the reference wavefunction. However, when using the restricted Hartree–Fock reference wavefunction, the TS1 CCSD(T) energy is lowered to yield a barrier of 31.2 kcal molÀ1, in much better agreement with the Received 29th August 2017, NEVPT2 result.
    [Show full text]
  • Nitroaromatic Antibiotics As Nitrogen Oxide Sources
    Review biomolecules Nitroaromatic Antibiotics as Nitrogen Oxide Sources Review Allison M. Rice, Yueming Long and S. Bruce King * Nitroaromatic Antibiotics as Nitrogen Oxide Sources Department of Chemistry and Biochemistry, Wake Forest University, Winston-Salem, NC 27101, USA; Allison M. Rice , Yueming [email protected] and S. Bruce (A.M.R.); King [email protected] * (Y.L.) * Correspondence: [email protected]; Tel.: +1-336-702-1954 Department of Chemistry and Biochemistry, Wake Forest University, Winston-Salem, NC 27101, USA; [email protected]: Nitroaromatic (A.M.R.); [email protected] antibiotics (Y.L.) show activity against anaerobic bacteria and parasites, finding * Correspondence: [email protected]; Tel.: +1-336-702-1954 use in the treatment of Heliobacter pylori infections, tuberculosis, trichomoniasis, human African trypanosomiasis, Chagas disease and leishmaniasis. Despite this activity and a clear need for the Abstract: Nitroaromatic antibiotics show activity against anaerobic bacteria and parasites, finding usedevelopment in the treatment of new of Heliobacter treatments pylori forinfections, these conditio tuberculosis,ns, the trichomoniasis, associated toxicity human Africanand lack of clear trypanosomiasis,mechanisms of action Chagas have disease limited and their leishmaniasis. therapeutic Despite development. this activity Nitroaro and a clearmatic need antibiotics for require thereductive development bioactivation of new treatments for activity for theseand this conditions, reductive the associatedmetabolism toxicity can convert
    [Show full text]
  • Efficient Surface Formation Route of Interstellar Hydroxylamine Through NO Hydrogenation II: the Multilayer Regime in Interstellar Relevant Ices
    1 Efficient Surface Formation Route of Interstellar Hydroxylamine through NO Hydrogenation II: the multilayer regime in interstellar relevant ices G. Fedoseev1, a), S. Ioppolo1, ‡, T. Lamberts1, 2, J. F. Zhen1, H. M. Cuppen2, H. Linnartz1 1Sackler Laboratory for Astrophysics, Leiden Observatory, University of Leiden, PO Box 9513, NL 2300 RA Leiden, The Netherlands 2Institute for Molecules and Materials, Radboud University Nijmegen, PO Box 9010, NL 6500 GL Nijmegen, The Netherlands Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final (N2O, NH2OH) and intermediate (HNO, NH2O·, etc.) products is discussed. The main conclusion is that hydroxylamine formation takes place via a fast and barrierless mechanism and it is found to be even more abundantly formed in a water-rich environment at lower temperatures. In parallel, we experimentally verify the non-formation of hydroxylamine upon UV photolysis of NO ice at cryogenic temperatures as well as the non-detection of NC- and NCO-bond bearing species after UV processing of NO in carbon monoxide-rich ices. Our results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and β-alanine) in gas phase reaction schemes.
    [Show full text]
  • Caprolactam 99/00-4
    Caprolactam 99/00-4 March 2001 TABLE OF CONTENTS Page I EXECUTIVE SUMMARY - 1 - A. SYNOPSIS - 1 - B. TECHNOLOGY DEVELOPMENTS - 1 - 1. Enhancements to Conventional Technology - 2 - 2. Caprolactam from Alternative Sources - 2 - C. TECHNO-ECONOMICS - 5 - 1. Enhancements to Conventional Technology - 5 - 2. Routes Based on Butadiene - 5 - D. COMMERCIAL STATUS - 8 - 1. Consumption - 8 - 2. Supply/Demand Balance - 9 - 3. Trade - 9 - 4. Ammonium Sulfate - 10 - E. STRATEGIC ISSUES - 12 - 1. Cyclicality - 12 - 2. Nylon Feedstocks from One Source - 13 - F. NYLON RECYCLING - 14 - G. CONCLUSIONS - 15 - II INTRODUCTION - 16 - A. AIM OF THE STUDY - 1 - B. OVERVIEW - 17 - 1. Enhancements to Conventional Technology - 17 - 2. Caprolactam from Alternative Sources - 17 - C. CHEM SYSTEMS PRODUCTION COST METHODOLOGY - 20 - 1. Capital Cost Estimation - 20 - (a) Battery Limits Investment - 20 - (b) Off-Sites Investment - 21 - (c) Contractor Charges(2) Typically 15-25 Percent of Installed BL and OS Costs - 22 - (d) Project Contingency Allowance(2) - 22 - (e) Working Capital - 22 - (f) Other Project Costs(3) - 23 - (1) Start-Up/Commissioning Costs - 23 - (2) Miscellaneous Owner’s Costs - 23 - 2. Cost of Production Elements - 24 - (a) Battery Limits - 24 - (b) Production Costs - 25 - (1) Labor - 25 - TABLE OF CONTENTS (Continued) Page III CAPROLACTAM FROM AROMATIC-DERIVED FEEDSTOCKS - 26 - A. COMMERCIAL TECHNOLOGIES - 26 - 1. Overview - 26 - 2. Process Chemistry - 26 - (a) Cyclohexanone Synthesis - 26 - (b) Oxime Formation with Cyclohexanone Using Hydroxylamine
    [Show full text]
  • Toxicological Profile for Hydrazines. US Department Of
    TOXICOLOGICAL PROFILE FOR HYDRAZINES U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service Agency for Toxic Substances and Disease Registry September 1997 HYDRAZINES ii DISCLAIMER The use of company or product name(s) is for identification only and does not imply endorsement by the Agency for Toxic Substances and Disease Registry. HYDRAZINES iii UPDATE STATEMENT Toxicological profiles are revised and republished as necessary, but no less than once every three years. For information regarding the update status of previously released profiles, contact ATSDR at: Agency for Toxic Substances and Disease Registry Division of Toxicology/Toxicology Information Branch 1600 Clifton Road NE, E-29 Atlanta, Georgia 30333 HYDRAZINES vii CONTRIBUTORS CHEMICAL MANAGER(S)/AUTHOR(S): Gangadhar Choudhary, Ph.D. ATSDR, Division of Toxicology, Atlanta, GA Hugh IIansen, Ph.D. ATSDR, Division of Toxicology, Atlanta, GA Steve Donkin, Ph.D. Sciences International, Inc., Alexandria, VA Mr. Christopher Kirman Life Systems, Inc., Cleveland, OH THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS: 1 . Green Border Review. Green Border review assures the consistency with ATSDR policy. 2 . Health Effects Review. The Health Effects Review Committee examines the health effects chapter of each profile for consistency and accuracy in interpreting health effects and classifying end points. 3. Minimal Risk Level Review. The Minimal Risk Level Workgroup considers issues relevant to substance-specific minimal risk levels (MRLs), reviews the health effects database of each profile, and makes recommendations for derivation of MRLs. HYDRAZINES ix PEER REVIEW A peer review panel was assembled for hydrazines. The panel consisted of the following members: 1. Dr.
    [Show full text]
  • On the Distinction Between Nitroxyl and Nitric Oxide Using Nitronyl Nitroxides
    Published on Web 05/26/2010 On the Distinction between Nitroxyl and Nitric Oxide Using Nitronyl Nitroxides Uri Samuni,† Yuval Samuni,‡ and Sara Goldstein*,§ Department of Chemistry and Biochemistry, Queens College, City UniVersity of New York, Flushing, New York 11367, and Department of Prosthodontics, School of Dental Medicine, and Institute of Chemistry, The Accelerator Laboratory, The Hebrew UniVersity of Jerusalem, Jerusalem 91904, Israel Received March 8, 2010; E-mail: [email protected] Abstract: A better understanding of the origins of NO and HNO and their activities and biological functions requires accurate methods for their detection and quantification. The unique reaction of NO with nitronyl nitroxides such as 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (C-PTIO), which yields the corresponding imino nitroxides, is widely used for NO detection (mainly by electron paramagnetic resonance spectroscopy) and for modulation of NO-induced physiological functions. The present study demonstrates that HNO readily reacts with nitronyl nitroxides, leading to the formation of the respective imino nitroxides and hydroxylamines via a complex mechanism. Through the use of the HNO donor Angeli’s salt (AS) with metmyoglobin as a competing agent, the rate constant for C-PTIO reduction by HNO has been determined to be (1.4 ( 0.2) × 105 M-1 s-1 at pH 7.0. This reaction yields the corresponding nitronyl • hydroxylamine C-PTIO-H and NO, which is trapped by C-PTIO to form NO2 and the corresponding imino • nitroxide, C-PTI. NO2 oxidizes the nitronyl and imino nitroxides to their respective oxoammonium cations, which decay mainly via comproportionation with the nitronyl and imino hydroxylamines.
    [Show full text]
  • Nitroxyl-Mediated Peroxide Modification of Polypropylene
    Nitroxyl-Mediated Peroxide Modification of Polypropylene by Benjamin Rhys Jones A thesis submitted to the Department of Chemical Engineering In conformity with the requirements for the degree of Master of Applied Science Queen’s University Kingston, Ontario, Canada (May 2021) Copyright ©Benjamin Rhys Jones, 2021 Abstract The thermal stability of alkoxyamine derivatives of polypropylene (PP) is examined through studies of model hydrocarbon systems and atactic-PP substrates. Primary, secondary and tertiary alkoxyamines are integral to modern techniques for modifying the architecture of linear PP materials, and detailed knowledge of their stability at polymer processing temperatures is needed to further understand the underlying principles of nitroxyl-based formulations. GC analysis of alkoxyamines derived from 2,4-dimethylpentane + TEMPO show that the tertiary regioisomer is susceptible to disproportionation to alkene + HOTEMPO at temperatures as low as 140 oC. Extension of these thermolysis experiments to atactic PP-g-HOTEMPO mirrored the model compound results, with appreciable extents of nitroxyl generation observed over a 20 min timescale at 180 oC. This reaction extent is not expected to dramatically alter the performance of nitroxyl-based formulations that modify the structure and composition of PP homopolymers. The yield of H-atom abstraction by peroxide-derived alkoxy radicals is another fundamental reaction that underlies polyolefin modifications. Indirect measures based on analysis of peroxide byproducts are supplemented with a fluorescence spectroscopy method that quantifies polymer- bound alkoxyamines. H-atom transfer from high density polyethylene (HDPE) and poly(ethylene-co-propylene) (EPR) was gained by using napthoyloxy-TEMPO, whose fluorophore supports a highly sensitive analytical method. This technique is extended to studies of reactive HDPE/EPR blending to ascertain the extent of peroxide migration from one phase to the other during the compounding process.
    [Show full text]
  • Fluorine-18-Labeled Fluorescent Dyes for Dual-Mode Molecular Imaging
    molecules Review Fluorine-18-Labeled Fluorescent Dyes for Dual-Mode Molecular Imaging Maxime Munch 1,2,*, Benjamin H. Rotstein 1,2 and Gilles Ulrich 3 1 University of Ottawa Heart Institute, Ottawa, ON K1Y 4W7, Canada; [email protected] 2 Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8M5, Canada 3 Institut de Chimie et Procédés pour l’Énergie, l’Environnement et la Santé (ICPEES), UMR CNRS 7515, École Européenne de Chimie, Polymères et Matériaux (ECPM), 25 rue Becquerel, CEDEX 02, 67087 Strasbourg, France; [email protected] * Correspondence: [email protected]; Tel.: +1-613-696-7000 Academic Editor: Emmanuel Gras Received: 30 November 2020; Accepted: 16 December 2020; Published: 21 December 2020 Abstract: Recent progress realized in the development of optical imaging (OPI) probes and devices has made this technique more and more affordable for imaging studies and fluorescence-guided surgery procedures. However, this imaging modality still suffers from a low depth of penetration, thus limiting its use to shallow tissues or endoscopy-based procedures. In contrast, positron emission tomography (PET) presents a high depth of penetration and the resulting signal is less attenuated, allowing for imaging in-depth tissues. Thus, association of these imaging techniques has the potential to push back the limits of each single modality. Recently, several research groups have been involved in the development of radiolabeled fluorophores with the aim of affording dual-mode PET/OPI probes used in preclinical imaging studies of diverse pathological conditions such as cancer, Alzheimer’s disease, or cardiovascular diseases. Among all the available PET-active radionuclides, 18F stands out as the most widely used for clinical imaging thanks to its advantageous characteristics (t1/2 = 109.77 min; 97% β+ emitter).
    [Show full text]
  • Nitroxyl (Hno) and Carbonylnitrenes
    INVESTIGATION OF REACTIVE INTERMEDIATES: NITROXYL (HNO) AND CARBONYLNITRENES by Tyler A. Chavez A dissertation submitted to the Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland February 2016 © 2016 Tyler A. Chavez All rights reserved Abstract Membrane inlet mass spectrometry (MIMS) is a well-established method used to detect gases dissolved in solution through the use of a semipermeable hydrophobic membrane that allows the dissolved gases, but not the liquid phase, to enter a mass spectrometer. Interest in the unique biological activity of azanone (nitroxyl, HNO) has highlighted the need for new sensitive and direct detection methods. Recently, MIMS has been shown to be a viable method for HNO detection with nanomolar sensitivity under physiologically relevant conditions (Chapter 2). In addition, this technique has been used to explore potential biological pathways to HNO production (Chapter 3). Nitrenes are reactive intermediates containing neutral, monovalent nitrogen atoms. In contrast to alky- and arylnitrenes, carbonylnitrenes are typically ground state singlets. In joint synthesis, anion photoelectron spectroscopic, and computational work we studied the three nitrenes, benzoylnitrene, acetylnitrene, and trifluoroacetylnitrene, with the purpose of determining the singlet-triplet splitting (ΔEST = ES – ET) in each case (Chapter 7). Further, triplet ethoxycarbonylnitrene and triplet t-butyloxycarbonylnitrene have been observed following photolysis of sulfilimine precursors by time-resolved infrared (TRIR) spectroscopy (Chapter 6). The observed growth kinetics of nitrene products suggest a contribution from both the triplet and singlet nitrene, with the contribution from the singlet becoming more prevalent in polar solvents. Advisor: Professor John P. Toscano Readers: Professor Kenneth D.
    [Show full text]