Yeast nitrogen utilization in the phyllosphere during plant lifespan under regulation of autophagy

PubMed Central

Shiraishi, Kosuke; Oku, Masahide; Kawaguchi, Kosuke; Uchida, Daichi; Yurimoto, Hiroya; Sakai, Yasuyoshi

2015-01-01

Recently, microbe-plant interactions at the above-ground parts have attracted great attention. Here we describe nitrogen metabolism and regulation of autophagy in the methylotrophic yeast Candida boidinii, proliferating and surviving on the leaves of Arabidopsis thaliana. After quantitative analyses of yeast growth on the leaves of A. thaliana with the wild-type and several mutant yeast strains, we showed that on young leaves, nitrate reductase (Ynr1) was necessary for yeast proliferation, and the yeast utilized nitrate as nitrogen source. On the other hand, a newly developed methylamine sensor revealed appearance of methylamine on older leaves, and methylamine metabolism was induced in C. boidinii, and Ynr1 was subjected to degradation. Biochemical and microscopic analysis of Ynr1 in vitro during a shift of nitrogen source from nitrate to methylamine revealed that Ynr1 was transported to the vacuole being the cargo for biosynthetic cytoplasm-to-vacuole targeting (Cvt) pathway, and degraded. Our results reveal changes in the nitrogen source composition for phyllospheric yeasts during plant aging, and subsequent adaptation of the yeasts to this environmental change mediated by regulation of autophagy. PMID:25900611

Testing the ability of non-methylamine osmolytes present in kidney cells to counteract the deleterious effects of urea on structure, stability and function of proteins.

PubMed

Khan, Sheeza; Bano, Zehra; Singh, Laishram R; Hassan, Md Imtaiyaz; Islam, Asimul; Ahmad, Faizan

2013-01-01

Human kidney cells are under constant urea stress due to its urine concentrating mechanism. It is believed that the deleterious effect of urea is counteracted by methylamine osmolytes (glycine betaine and glycerophosphocholine) present in kidney cells. A question arises: Do the stabilizing osmolytes, non-methylamines (myo-inositol, sorbitol and taurine) present in the kidney cells also counteract the deleterious effects of urea? To answer this question, we have measured structure, thermodynamic stability (ΔG D (o)) and functional activity parameters (K m and k cat) of different model proteins in the presence of various concentrations of urea and each non-methylamine osmolyte alone and in combination. We observed that (i) for each protein myo-inositol provides perfect counteraction at 1∶2 ([myo-inositol]:[urea]) ratio, (ii) any concentration of sorbitol fails to refold urea denatured proteins if it is six times less than that of urea, and (iii) taurine regulates perfect counteraction in a protein specific manner; 1.5∶2.0, 1.2∶2.0 and 1.0∶2.0 ([taurine]:[urea]) ratios for RNase-A, lysozyme and α-lactalbumin, respectively.

Testing the Ability of Non-Methylamine Osmolytes Present in Kidney Cells to Counteract the Deleterious Effects of Urea on Structure, Stability and Function of Proteins

PubMed Central

Khan, Sheeza; Bano, Zehra; Singh, Laishram R.; Hassan, Md. Imtaiyaz; Islam, Asimul; Ahmad, Faizan

2013-01-01

Human kidney cells are under constant urea stress due to its urine concentrating mechanism. It is believed that the deleterious effect of urea is counteracted by methylamine osmolytes (glycine betaine and glycerophosphocholine) present in kidney cells. A question arises: Do the stabilizing osmolytes, non-methylamines (myo-inositol, sorbitol and taurine) present in the kidney cells also counteract the deleterious effects of urea? To answer this question, we have measured structure, thermodynamic stability (ΔG D o) and functional activity parameters (K m and k cat) of different model proteins in the presence of various concentrations of urea and each non-methylamine osmolyte alone and in combination. We observed that (i) for each protein myo-inositol provides perfect counteraction at 1∶2 ([myo-inositol]:[urea]) ratio, (ii) any concentration of sorbitol fails to refold urea denatured proteins if it is six times less than that of urea, and (iii) taurine regulates perfect counteraction in a protein specific manner; 1.5∶2.0, 1.2∶2.0 and 1.0∶2.0 ([taurine]:[urea]) ratios for RNase-A, lysozyme and α-lactalbumin, respectively. PMID:24039776

Methylamine-Sensitive Amperometric Biosensor Based on (His)6-Tagged Hansenula polymorpha Methylamine Oxidase Immobilized on the Gold Nanoparticles

PubMed Central

Stasyuk, Nataliya Ye.; Smutok, Oleh V.; Zakalskiy, Andriy E.; Zakalska, Oksana M.; Gonchar, Mykhailo V.

2014-01-01

A novel methylamine-selective amperometric bienzyme biosensor based on recombinant primary amine oxidase isolated from the recombinant yeast strain Saccharomyces cerevisiae and commercial horseradish peroxidase is described. Two amine oxidase preparations were used: free enzyme (AMO) and covalently immobilized on the surface of gold nanoparticles (AMO-nAu). Some bioanalytical parameters (sensitivity, selectivity, and storage stability) of the developed biosensors were investigated. The sensitivity for both sensors is high: 1450 ± 113 and 700 ± 30 A−1 ·M−1 ·m−2 for AMO-nAu biosensor, respectively. The biosensors exhibit the linear range from 15 μM to 150 μM (AMO-nAu) and from 15 μM to 60 μM (AMO). The developed biosensor demonstrated a good selectivity toward methylamine (MA) (signal for dimethylamine and trimethylamine is less than 5% and for ethylamine 15% compared to MA output) and reveals a satisfactory storage stability. The constructed amperometric biosensor was used for MA assay in real samples of fish products in comparison with chemical method. The values obtained with both approaches different methods demonstrated a high correlation. PMID:25136590

Purification and characterization of the amine dehydrogenase from a facultative methylotroph.

PubMed

Coleman, J P; Perry, J J

1984-01-01

Strain RA-6 is a pink-pigmented organism which can grow on a variety of substrates including methylamine. It can utilize methylamine as sole source of carbon via an isocitrate lyase negative serine pathway. Methylamine grown cells contain an inducible primary amine dehydrogenase [primary amine: (acceptor) oxidoreductase (deaminating)] which is not present in succinate grown cells. The amine dehydrogenase was purified to over 90% homogeneity. It is an acidic protein (isoelectric point of 5.37) with a molecular weight of 118,000 containing subunits with approximate molecular weights of 16,500 and 46,000. It is active on an array of primary terminal amines and is strongly inhibited by carbonyl reagents. Cytochrome c or artificial electron acceptors are required for activity; neither NAD nor NADP can serve as primary electron acceptor.

The large amplitude motions of methylamine from the perspective of the highly correlated ab initio methods

NASA Astrophysics Data System (ADS)

Senent, M. L.

2018-01-01

CCSD(T)-F12 theory in connection with extended basis sets is employed to determine the electronic ground state spectroscopic parameters of methylamine at low temperatures. The geometry, the rotational constants, all the fundamental frequencies, the dipole moment and its components, and the centrifugal distortion constants, are provided. The ground vibrational state rotational constants were found to be A0 = 103067.15 MHz, B0 = 22588.29 MHz, and C0 = 21710.50 MHz and the dipole moment to be 1.4071D. Fermi displacements of the vibrational bands are predicted. The low vibrational energy levels corresponding to the large amplitude motions are determine variationally using a flexible three-dimensional model depending on three variables: the HNH bending, the NH2 wagging and the CH3 torsional coordinates. The computed levels are compared with previous experimental and calculated energies. Methylamine parameters are very sensitive to the level of ab initio calculations.

Luminescent amine sensor based on europium(III) chelate.

PubMed

Petrochenkova, Nataliya V; Mirochnik, Anatolii G; Emelina, Tatyana B; Sergeev, Alexander A; Leonov, Andrei A; Voznesenskii, Sergey S

2018-07-05

The effect of methylamine vapor on luminescence of Eu(III) tris-benzoylacetonate (I) immobilized in thin-layer chromatography plates has been investigated. It has been revealed that interaction of I with analyte vapor results in increase of the intensity of Eu(III) luminescence. The mechanism of the effect of methylamine vapors on intensification of the Eu(III) luminescence has been suggested using the data of IR spectroscopy and quantum chemistry calculations. The mechanism of luminescence sensitization consists in bonding of an analyte molecule with a water molecule into the coordination sphere of Eu(III). As a result, the bond of a water molecule with the luminescence centre weakens, rigid structural fragment including europium ion, water and methylamine molecules forms. The presence of such fragment must naturally promote decrease of influence of OH-vibrations on luminescence of the complex I. Copyright © 2018 Elsevier B.V. All rights reserved.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide

DOE PAGES

Wheeler, Lance M.; Moore, David T.; Ihly, Rachelle; ...

2017-11-23

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer - composed of a metal halide perovskite-methylamine complex - from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning themore » absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. In conclusion, this work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.« less

Gas chromatographic/mass spectrometric determination of carbon isotope composition in unpurified samples: methamphetamine example.

PubMed

Low, I A; Liu, R H; Legendre, M G; Piotrowski, E G; Furner, R L

1986-10-01

A gas chromatograph/quadrupole mass spectrometer system, operated in electron impact/selected ion monitoring mode, is used to determine the intensity ratio of the m/z 59 and the m/z 58 ions of the [C3H8N]+ fragment derived from methamphetamine samples synthesized with varying amounts of 13C-labeled methylamine. Crude products are introduced into the gas chromatograph without prior cleanup. The ratios measured were in excellent agreement with those calculated. A change in 0.25% use of 13C-methylamine is sufficient for product differentiation. The feasibility of using isotope labeling and subsequent mass spectrometric isotope ratio measurement as the basis of a compound tracing mechanism is discussed. Specifically, if methamphetamine samples manufactured from legal sources are asked to incorporate distinct 13C compositions, their sources can be traced when samples are diverted into illegal channels. Samples derived from illicit preparations can also be traced if the manufacturers of a precursor (methylamine in this case) incorporate distinct 13C compositions in their products.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide.

PubMed

Wheeler, Lance M; Moore, David T; Ihly, Rachelle; Stanton, Noah J; Miller, Elisa M; Tenent, Robert C; Blackburn, Jeffrey L; Neale, Nathan R

2017-11-23

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer-composed of a metal halide perovskite-methylamine complex-from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning the absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. This work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheeler, Lance M.; Moore, David T.; Ihly, Rachelle

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer - composed of a metal halide perovskite-methylamine complex - from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning themore » absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. In conclusion, this work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.« less

Pseudoalteromonas haloplanktis produces methylamine, a volatile compound active against Burkholderia cepacia complex strains.

PubMed

Sannino, Filomena; Parrilli, Ermenegilda; Apuzzo, Gennaro Antonio; de Pascale, Donatella; Tedesco, Pietro; Maida, Isabel; Perrin, Elena; Fondi, Marco; Fani, Renato; Marino, Gennaro; Tutino, Maria Luisa

2017-03-25

The Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 has been reported to produce several Volatile Organic Compounds (VOCs), which are able to inhibit the growth of Burkholderia cepacia complex (Bcc) strains, opportunistic pathogens responsible for the infection of immune-compromised patients. However, no specific antibacterial VOCs have been identified to date. The purpose of the present study was to identify specific VOCs that contribute to Bcc inhibition by the Antarctic strain. When grown on defined medium containing D-gluconate and L-glutamate as carbon, nitrogen and energy sources, P. haloplanktis TAC125 is unable to inhibit the growth of Bcc strains. However, single addition of several amino acids to the defined medium restores the P. haloplanktis TAC125 inhibition ability. With the aim of identifying specific volatile compound/s responsible for Bcc inhibition, we set up an apparatus for VOC capture, accumulation, and storage. P. haloplanktis TAC125 was grown in an automatic fermenter which was connected to a cooling system to condense VOCs present in the exhaust air outlet. Upon addition of methionine to the growth medium, the VOC methylamine was produced by P. haloplanktis TAC125. Methylamine was found to inhibit the growth of several Bcc strains in a dose-dependent way. Although it was reported that P. haloplanktis TAC125 produces VOCs endowed with antimicrobial activity, this is the first demonstration that methylamine probably contributes to the anti-Bcc activity of P. haloplanktis TAC125 VOCs. Copyright © 2016 Elsevier B.V. All rights reserved.

Semicarbazide-sensitive amine oxidase substrates potentiate hydralazine hypotension: possible role of hydrogen peroxide.

PubMed

Vidrio, Horacio; Medina, Martha; González-Romo, Pilar; Lorenzana-Jiménez, Marte; Díaz-Arista, Patricia; Baeza, Alejandro

2003-11-01

The relation between inhibition of semicarbazide-sensitive amine oxidase (SSAO) and vasodilation by hydralazine (HYD) was evaluated in chloralose/urethane-anesthetized rats pretreated with various substrates of the enzyme and subsequently administered a threshold hypotensive dose of the vasodilator. The SSAO substrates benzylamine, phenethylamine, and methylamine potentiate the hypotensive response to HYD. Methylamine, which was studied in greater detail because of its status as a possible endogenous SSAO substrate, does not influence the response to the reference vasodilator pinacidil; it does enhance HYD relaxation in aortic rings obtained from pretreated rats. Experiments designed to identify the product of SSAO activity responsible for potentiation by methylamine suggest involvement of hydrogen peroxide (H2O2), as evidenced by the findings that such potentiation is abolished by additional pretreatment with the H2O2-metabolizing enzyme catalase, and that the plasma concentration of H2O2 is increased by methylamine and decreased by HYD. These results are interpreted as a substantiation of the relation between the known SSAO inhibitory effect of HYD and its vasodilator activity. Pretreatment with the SSAO substrates would increase production of H2O2 in vascular smooth muscle and thus magnify the influence of this vasoconstrictor agent on vascular tone. In these conditions, the decrease in H2O2 production and hence in vascular tone caused by SSAO inhibition by HYD would also be magnified. It is speculated that inhibition of vascular SSAO could represent a novel mechanism of vasodilation.

Free-Energy Landscape and Proton Transfer Pathways in Oxidative Deamination by Methylamine Dehydrogenase.

PubMed

Zelleke, Theodros; Marx, Dominik

2017-01-18

The rate-determining step in the reductive half-reaction of the bacterial enzyme methylamine dehydrogenase, which is proton abstraction from the native substrate methylamine, is investigated using accelerated QM/MM molecular dynamics simulations at room temperature. Generation of the multidimensional thermal free-energy landscape without restriction of the degrees of freedom beyond a multidimensional reaction subspace maps two rather similar pathways for the underlying proton transfer to one of two aspartate carboxyl oxygen atoms, termed OD1 and OD2, which hydrogen bond with Thr122 and Trp108, respectively. Despite significant large-amplitude motion perpendicular to the one-dimensional proton transfer coordinate, due to fluctuations of the donor-acceptor distance of about 3 Å, it is found that the one-dimensional proton transfer free-energy profiles are essentially identical to the minimum free-energy pathways on the multidimensional free-energy landscapes for both proton transfer channels. Proton transfer to one of the acceptor oxygen atoms-the OD2 site-is slightly favored in methylamine dehydrogenase by approximately 2 kcal mol -1 , both kinetically and thermodynamically. Mechanistic analyses reveal that the hydrogen bond between Thr122β and OD1 is always present in the transition state independently of the proton transfer channel. Population analysis confirms that the electronic charge gained upon oxidation of the substrate is delocalized within the ring systems of the tryptophan tryptophylquinone cofactor. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interkingdom Cross-Feeding of Ammonium from Marine Methylamine-Degrading Bacteria to the Diatom Phaeodactylum tricornutum.

PubMed

Suleiman, Marcel; Zecher, Karsten; Yücel, Onur; Jagmann, Nina; Philipp, Bodo

2016-12-15

Methylamines occur ubiquitously in the oceans and can serve as carbon, nitrogen, and energy sources for heterotrophic bacteria from different phylogenetic groups within the marine bacterioplankton. Diatoms, which constitute a large part of the marine phytoplankton, are believed to be incapable of using methylamines as a nitrogen source. As diatoms are typically associated with heterotrophic bacteria, the hypothesis came up that methylotrophic bacteria may provide ammonium to diatoms by degradation of methylamines. This hypothesis was investigated with the diatom Phaeodactylum tricornutum and monomethylamine (MMA) as the substrate. Bacteria supporting photoautotrophic growth of P. tricornutum with MMA as the sole nitrogen source could readily be isolated from seawater. Two strains, Donghicola sp. strain KarMa, which harbored genes for both monomethylamine dehydrogenase and the N methylglutamate pathway, and Methylophaga sp. strain M1, which catalyzed MMA oxidation by MMA dehydrogenase, were selected for further characterization. While strain M1 grew with MMA as the sole substrate, strain KarMa could utilize MMA as a nitrogen source only when, e.g., glucose was provided as a carbon source. With both strains, release of ammonium was detected during MMA utilization. In coculture with P. tricornutum, strain KarMa supported photoautotrophic growth with 2 mM MMA to the same extent as with the equimolar amount of NH 4 Cl. In coculture with strain M1, photoautotrophic growth of P. tricornutum was also supported, but to a much lower degree than by strain KarMa. This proof-of-principle study with a synthetic microbial community suggests that interkingdom cross-feeding of ammonium from methylamine-degrading bacteria is a contribution to phytoplankton growth which has been overlooked so far. Interactions between diatoms and heterotrophic bacteria are important for marine carbon cycling. In this study, a novel interaction is described. Bacteria able to degrade monomethylamine, which is a ubiquitous organic nitrogen compound in marine environments, can provide ammonium to diatoms. This interkingdom metabolite transfer enables growth under photoautotrophic conditions in coculture, which would not be possible in the respective monocultures. This proof-of-principle study calls attention to a so far overlooked contribution to phytoplankton growth. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Interkingdom Cross-Feeding of Ammonium from Marine Methylamine-Degrading Bacteria to the Diatom Phaeodactylum tricornutum

PubMed Central

Suleiman, Marcel; Zecher, Karsten; Yücel, Onur; Jagmann, Nina

2016-01-01

ABSTRACT Methylamines occur ubiquitously in the oceans and can serve as carbon, nitrogen, and energy sources for heterotrophic bacteria from different phylogenetic groups within the marine bacterioplankton. Diatoms, which constitute a large part of the marine phytoplankton, are believed to be incapable of using methylamines as a nitrogen source. As diatoms are typically associated with heterotrophic bacteria, the hypothesis came up that methylotrophic bacteria may provide ammonium to diatoms by degradation of methylamines. This hypothesis was investigated with the diatom Phaeodactylum tricornutum and monomethylamine (MMA) as the substrate. Bacteria supporting photoautotrophic growth of P. tricornutum with MMA as the sole nitrogen source could readily be isolated from seawater. Two strains, Donghicola sp. strain KarMa, which harbored genes for both monomethylamine dehydrogenase and the N methylglutamate pathway, and Methylophaga sp. strain M1, which catalyzed MMA oxidation by MMA dehydrogenase, were selected for further characterization. While strain M1 grew with MMA as the sole substrate, strain KarMa could utilize MMA as a nitrogen source only when, e.g., glucose was provided as a carbon source. With both strains, release of ammonium was detected during MMA utilization. In coculture with P. tricornutum, strain KarMa supported photoautotrophic growth with 2 mM MMA to the same extent as with the equimolar amount of NH4Cl. In coculture with strain M1, photoautotrophic growth of P. tricornutum was also supported, but to a much lower degree than by strain KarMa. This proof-of-principle study with a synthetic microbial community suggests that interkingdom cross-feeding of ammonium from methylamine-degrading bacteria is a contribution to phytoplankton growth which has been overlooked so far. IMPORTANCE Interactions between diatoms and heterotrophic bacteria are important for marine carbon cycling. In this study, a novel interaction is described. Bacteria able to degrade monomethylamine, which is a ubiquitous organic nitrogen compound in marine environments, can provide ammonium to diatoms. This interkingdom metabolite transfer enables growth under photoautotrophic conditions in coculture, which would not be possible in the respective monocultures. This proof-of-principle study calls attention to a so far overlooked contribution to phytoplankton growth. PMID:27694241

Rapid removal of acetimidoyl groups from proteins and peptides. Applications to primary structure determination.

PubMed Central

Dubois, G C; Robinson, E A; Inman, J K; Perham, R N; Appella, E

1981-01-01

Methylamine buffers can be used for the rapid quantitative removal of acetimidoyl groups from proteins and peptides modified by treatment with ethyl or methyl acetimidate. The half-life for displacement of acetimidoyl groups from fully amidinated proteins incubated in 3.44 M-methylamine/HCl buffer at pH 11.5 and 25 degrees C was approx. 26 min; this half life is 29 times less than that observed in ammonia/HCl buffer under the same conditions of pH and amine concentration. Incubation of acetimidated proteins with methylamine for 4 h resulted in greater than 95% removal of acetimidoyl groups. No deleterious effects on primary structure were detected by amino acid analysis or by automated Edman degradation. Reversible amidination of lysine residues, in conjunction with tryptic digestion, has been successfully applied to the determination of the amino acid sequence of an acetimidated mouse immunoglobulin heavy chain peptide. The regeneration of amino groups in amidinated proteins and peptides by methylaminolysis makes amidination a valuable alternative to citraconoylation and maleoylation in structural studies. PMID:6803762

Aerobic Biodegradation of N-Nitrosodimethylamine by the Propanotroph Rhodococcus ruber ENV425▿

PubMed Central

Fournier, Diane; Hawari, Jalal; Halasz, Annamaria; Streger, Sheryl H.; McClay, Kevin R.; Masuda, Hisako; Hatzinger, Paul B.

2009-01-01

The propanotroph Rhodococcus ruber ENV425 was observed to rapidly biodegrade N-nitrosodimethylamine (NDMA) after growth on propane, tryptic soy broth, or glucose. The key degradation intermediates were methylamine, nitric oxide, nitrite, nitrate, and formate. Small quantities of formaldehyde and dimethylamine were also detected. A denitrosation reaction, initiated by hydrogen atom abstraction from one of the two methyl groups, is hypothesized to result in the formation of n-methylformaldimine and nitric oxide, the former of which decomposes in water to methylamine and formaldehyde and the latter of which is then oxidized further to nitrite and then nitrate. Although the strain mineralized more than 60% of the carbon in [14C]NDMA to 14CO2, growth of strain ENV425 on NDMA as a sole carbon and energy source could not be confirmed. The bacterium was capable of utilizing NDMA, as well as the degradation intermediates methylamine and nitrate, as sources of nitrogen during growth on propane. In addition, ENV425 reduced environmentally relevant microgram/liter concentrations of NDMA to <2 ng/liter in batch cultures, suggesting that the bacterium may have applications for groundwater remediation. PMID:19542346

Using Hyperfine Structure to Quantify the Effects of Substitution on the Electron Distribution Within a Pyridine Ring: a Study of 2-, 3-, and 4-PICOLYLAMINE

NASA Astrophysics Data System (ADS)

McDivitt, Lindsey M.; Himes, Korrina M.; Bailey, Josiah R.; McMahon, Timothy J.; Bird, Ryan G.

2017-06-01

The ground state rotational spectra of the three methylamine substituted pyridines, 2-, 3-, and 4-picolylamine, were collected and analyzed over the frequency range of 7-17.5 GHz using chirped-pulsed Fourier transform microwave spectroscopy. All three molecules show a distinctive quadrupole splitting, which is representative of the local electronic environment around the two different ^{14}N nuclei, with the pyridine nitrogen being particularly sensitive to the pi-electron distribution within the ring. The role that the position of the methylamine group plays on the quadrupole coupling constants on both nitrogens will be discussed and compared to other substituted pyridines.

Thin-Film Transformation of NH4 PbI3 to CH3 NH3 PbI3 Perovskite: A Methylamine-Induced Conversion-Healing Process.

PubMed

Zong, Yingxia; Zhou, Yuanyuan; Ju, Minggang; Garces, Hector F; Krause, Amanda R; Ji, Fuxiang; Cui, Guanglei; Zeng, Xiao Cheng; Padture, Nitin P; Pang, Shuping

2016-11-14

Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH 4 PbI 3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH 3 NH 3 PbI 3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH 4 PbI 3 -to-CH 3 NH 3 PbI 3 transformation process. The chemical origins of this transformation are studied at various length scales. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new room temperature gas sensor based on pigment-sensitized TiO2 thin film for amines determination.

PubMed

Yanxiao, Li; Xiao-bo, Zou; Xiao-wei, Huang; Ji-yong, Shi; Jie-wen, Zhao; Holmes, Mel; Hao, Limin

2015-05-15

A new room temperature gas sensor was fabricated with pigment-sensitized TiO2 thin film as the sensing layer. Four natural pigments were extracted from spinach (Spinacia oleracea), red radish (Raphanus sativus L), winter jasmine (Jasminum nudiflorum), and black rice (Oryza sativa L. indica) by ethanol. Natural pigment-sensitized TiO2 sensor was prepared by immersing porous TiO2 films in an ethanol solution containing a natural pigment for 24h. The hybrid organic-inorganic formed films here were firstly exposed to atmospheres containing methylamine vapours with concentrations over the range 2-10 ppm at room temperature. The films sensitized by the pigments from black-rice showed an excellent gas-sensitivity to methylamine among the four natural pigments sensitized films due to the anthocyanins. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of methylamine (r=0.931). At last, the black rice pigment sensitized TiO2 thin film was used to determine the biogenic amines generated by pork during storage. The developed films had good sensitivity to analogous gases such as putrscine, and cadaverine that will increase during storage. Copyright © 2014 Elsevier B.V. All rights reserved.

Ozone Promotes Chloropicrin Formation by Oxidizing Amines to Nitro Compounds.

PubMed

McCurry, Daniel L; Quay, Amanda N; Mitch, William A

2016-02-02

Chloropicrin formation has been associated with ozonation followed by chlorination, but the reaction pathway and precursors have been poorly characterized. Experiments with methylamine demonstrated that ozonation converts methylamine to nitromethane at ∼100% yield. Subsequent chlorination converts nitromethane to chloropicrin at ∼50% yield under the conditions evaluated. Similarly high yields from other primary amines were limited to those with functional groups on the β-carbon (e.g., the carboxylic acid in glycine) that facilitate carbon-carbon bond cleavage to release nitromethyl anion. Secondary amines featuring these reactive primary amines as functional groups (e.g., secondary N-methylamines) formed chloropicrin at high yields, likely by facile dealkylation to release the primary nitro compound. Chloropicrin yields from tertiary amines were low. Natural water experiments, including derivatization to transform primary and secondary amines to less reactive carbamate functional groups, indicated that primary and secondary amines were the dominant chloropicrin precursors during ozonation/chlorination. Ozonation followed by chlorination of the primary amine side chain of lysine demonstrated low yields (∼0.2%) of chloropicrin, but high yields (∼17%) of dichloronitrolysine, a halonitroalkane structural analogue to chloropicrin. However, chloropicrin yields increased and dichloronitrolysine yields decreased in the absence of hydroxyl radical scavengers, suggesting that future research should characterize the potential occurrence of such halonitroalkane analogues relative to natural radical scavenger (e.g., carbonate) concentrations.

The pH Dependence of Brown Carbon Formation in Maillard Chemistry

NASA Astrophysics Data System (ADS)

Hawkins, L. N.; Welsh, H.; Alexander, M. V.

2017-12-01

Secondary organic aerosol (SOA) composes a non-negligible fraction of brown carbon (BrC), and typically appears as small, nitrated aromatics or larger, highly functionalized humic-like substances (HULIS). Both nitrated aromatics and HULIS contain nitrogen, indicating the importance of nitrogen to light-absorbing aerosol. It is therefore unsurprising that BrC, when generated in aqueous phase reactions (aqBrC) between amines and small aldehydes, often resembles atmospheric HULIS. The effects of pH and aqueous phase oxidation on absorptivity and composition were simulated using bulk (microliter) samples under a variety of experimental conditions, including evaporation. The system of amines and small aldehydes included methylamine, ammonium sulfate, glyoxal, and methylglyoxal. Chemical composition of these products was characterized using an Aerosol Chemical Speciation Monitor (ACSM) and a desorption-based atmospheric pressure chemical ionization (APCI) spectrometer. The results of this study indicate that methylamine and methylglyoxal form the most absorptive BrC, cloud processing serves to increase BrC absorptivity, and the generated BrC is highly persistent to oxidative and photodegradation. Lowering the pH to values below 6 reduces absorptivity at shorter wavelengths, but produces a new shoulder beyond 400 nm indicating new chromophore formation. Results of this research also show that evaporation increased formation of large molecular fragments (m/z > 100). Furthermore, the mass spectra showed significant formation of these larger fragments in methylamine systems with little evidence for similar compounds in ammonium sulfate systems. Systems with methylglyoxal had higher absorptivity than all other systems, although in both methylamine and ammonium sulfate systems, glyoxal appeared to result in a higher percentage of large fragments than methylglyoxal. Lastly, hydroxyl radical degradation seemed to have a minimal effect on absorptivity and composition, although longer reaction time may produce a larger effect on both properties. These results may simplify some aspects of atmospheric models (like negligible degradation) but may complicate others (highly variable absorptivity between glyoxal and methylglyoxal).

Counteraction of the deleterious effects of urea on structure and stability of mammalian kidney proteins by osmolytes.

PubMed

Dar, Mohammad Aasif; Wahiduzzaman; Islam, Asimul; Hassan, Md Imtaiyaz; Ahmad, Faizan

2018-02-01

Owing to the urine concentrating mechanism of kidney cells, urea concentration is very high (3.0-5.0M) in mammalian kidneys which may denature many kidney proteins. Methylamines are known to counteract the deleterious effects of urea on structure, stability and function of proteins at 2:1 molar ratio of urea to methylamines. It is known that mammalian kidney cells also contain stabilizing osmolytes, non-methylamines (myo-inositol and sorbitol). A question arises: Do these non-methylmine osmolytes have ability to counteract the deleterious effects of urea on kidney proteins? To answer this question, we took two kidney proteins, namely, sheep serum albumin and Human carbonic anhydrase II. We measured their thermodynamic stability (ΔG 0 N↔D , the Gibbs free energy change in absence of GdmCl (guanidinium chloride) associated with the equilibrium, native (N) state↔denatured (D) state) from the GdmCl-induced denaturation curves in the presence of different concentrations of urea and each kidney osmolyte individually and in combination. For both proteins, we observed that (i) glycine betaine and myo-inositol provide perfect counteraction at 2:1 molar ratio of urea to osmolyte, i.e., denaturing effect of 2M urea is 100% neutralized by 1M of glycine betaine (or myo-inositol), and (ii) sorbitol fails to refold urea denatured proteins. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantitative analysis of aliphatic amines in urbanaerosols based on online derivatization and highperformance liquid chromatography

NASA Astrophysics Data System (ADS)

Huang, X.; Zhuang, G.; Zhao, J.; Deng, C.

2016-12-01

A method combining online derivatization with high performance liquid chromatography/fluorescence detection was developed for the determination of seven aliphatic amines (ethanolamine, methylamine, ethylamine, propylamine, butylamine, pentylamine and hexylamine) in urban aerosols. The collected amines were online derivatized with o-phthalaldehyde to form highly fluorescent sulfonatoisoindole derivatives. The derivatives were completely separated in 13 min through gradient elution and detected by fluorescent detection at an excitation wavelength of 334 nm and an emission wavelength of 443 nm. Under the optimized conditions, the relative standard derivations (RSDs) of all detected amines were 0.02-2.03% and 1.04-1.52% for retention time and peak area, respectively. Excellent linearity was achieved for each analyte, ranging from 5 g/L to 1000 g/L (R20.99). Detection limits for all analytes were below 1.1 g/L. The proposed method was used to analyze aliphatic amines in 35 samples of urban PM2.5 collected in Shanghai and was found to be suitable for the determination of particulate aliphatic amines at the level of ng/m3 in ambient air. Based on our measurements, ethanolamine and methylamine were the most abundant species on average in Shanghai during dry and wet seasons. The highest concentration was 15.3 ng/m3 for ethanolamine and 13.2 ng/m3 for methylamine.

Something new from something old? Fracking stimulated microbial processes

NASA Astrophysics Data System (ADS)

Wrighton, K. C.; Daly, R. A.; Hoyt, D.; Trexler, R.; McRae, J.; Wilkins, M.; Mouser, P. J.

2015-12-01

Hydraulic fracturing, colloquially known as "fracking", is employed for effective gas and oil recovery in deep shales. This process injects organisms and liquids from the surface into the deep subsurface (~2500 m), exposing microorganisms to high pressures, elevated temperatures, chemical additives, and brine-level salinities. Here we use assembly-based metagenomics to create a metabolic blueprint from an energy-producing Marcellus shale well over a 328-day period. Using this approach we ask the question: What abiotic and biotic factors drive microbial metabolism and thus biogeochemical cycling during natural gas extraction? We found that after 49 days, increased salinity in produced waters corresponded to a shift in the microbial community, with only organisms that encode salinity adaptations detected. We posit that organic compatible solutes, produced by organisms adapting to increased salinity, fuels a methylamine-driven ecosystem in fractured shale. This metabolic network ultimately results in biogenic methane production from members of Methanohalophilus and Methanolobus. Proton NMR validated these genomic hypotheses, with mono-methylamine being highest in the input material, but detected throughout the sampling. Beyond abiotic constraints, our genomic investigations revealed that viruses can be linked to key members of the microbial community, potentially releasing methylamine osmoprotectants and impacting bacterial strain variation. Collectively our results indicate that adaptation to high salinity, metabolism in the absence of oxidized electron acceptors, and viral predation are controlling factors mediating microbial community metabolism during hydraulic fracturing of the deep subsurface.

Real-time observation of coadsorption layers on Ru(001) using a temperature-programmed ESDIAD/TOF system

NASA Astrophysics Data System (ADS)

Sasaki, T.; Itai, Y.; Iwasawa, Y.

1997-11-01

For the purpose of utilizing ESDIAD as a real-time probe for surface processes, we have developed an instrument which can measure ESDIAD images and time of flight (TOF) spectra of desorbing ions in temperature-programmed surface processes. TOF measurements are carried out to identify the mass and to determine the kinetic energy distribution of the desorbed ions. This temperature-programmed (TP-) ESDIAD/TOF system was used to observe coadsorption layers of methylamine and CO on Ru(001) which have been previously studied by our group using LEED, TPD and HREELS, also drawing upon a comparison of findings with the coadsorption system of CO and ammonia. ESDIAD images acquired for temperature-programmed surface processes in real time were found to provide new insight into the dynamic behaviour of the coadsorption layers. As to the pure adsorption of ammonia and methylamine, the second and the first (chemisorbed) layers can be easily discriminated in their different ESD detection efficiency due to the difference in neutralization rate. The intensity change of H + ions with temperature shows the process of the decomposition of methylamine to be dependent on CO coverage. The intensity of O + originating from CO changes due to the change of CO adsorption site in the reaction process. The angular distribution of H + ions which correspond to CH2NH…Ru species appears at 250-300 K in the presence of high CO pre-coverage.

Interactions of methylamine and ammonia with atmospheric nucleation precursor H{sub 2}SO{sub 4} and common organic acids: Thermodynamics and atmospheric implications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Y.; Jiang, L.; Bai, Z.

Interactions of the two common atmospheric bases, ammonia (NH{sub 3}) and methylamine MA (CH{sub 3}NH{sub 2}), which are considered to be important stabilizers of binary clusters in the Earth’s atmosphere, with H{sub 2}SO{sub 4}, the key atmospheric precursor, and 14 common atmospheric organic acids (COA) (formic (CH{sub 2}O{sub 2}), acetic (C{sub 2}H{sub 4}O{sub 2}), oxalic (C{sub 2}H{sub 2}O{sub 4}), malonic (C{sub 3}H{sub 4}O{sub 4}), succinic (C{sub 4}H{sub 6}O{sub 4}), glutaric acid (C{sub 5}H{sub 8}O{sub 4}), adipic (C{sub 6}H{sub 10}O{sub 4}), benzoic (C{sub 6}H{sub 5}COOH), phenylacetic (C{sub 6}H{sub 5}CH{sub 2}COOH), pyruvic (C{sub 3}H{sub 4}O{sub 3}), maleic acid (C{sub 4}H{sub 4}O{sub 4}),more » malic (C{sub 4}H{sub 6}O{sub 5}), tartaric (C{sub 4}H{sub 6}O{sub 6}) and pinonic acid (C{sub 10}H{sub 16}O{sub 3})) have been studied using the composite high-accuracy G3MP2 method. The thermodynamic stability of mixed (COA) (H{sub 2}SO{sub 4}), (COA)(B1) and (COA)(B2) dimers and (COA) (H{sub 2}SO{sub 4}) (B1) and (COA) (H{sub 2}SO{sub 4}) (B1) trimers, where B1 and B2 represent methylamine (CH{sub 3}NH{sub 2}) and ammonia (NH{sub 3}), respectively, have been investigated and their impacts on the thermodynamic stability of clusters containing H{sub 2}SO{sub 4} have been analyzed. It has been shown that in many cases the interactions of H{sub 2}SO{sub 4} with COA, ammonia and methylamine lead to the formation of heteromolecular dimers and trimers, which are certainly more stable than (H{sub 2}SO{sub 4}){sub 2} and (H{sub 2}SO{sub 4}){sub 3}. It has also been found that free energies of (COA) (H{sub 2}SO{sub 4})+ CH{sub 3}NH{sub 2}⇔(COA) (H{sub 2}SO{sub 4})(CH{sub 3}NH{sub 2}) reactions exceed 10-15 kcal mol{sup −1}. This is a clear indication that mixed trimers composed of COA, H{sub 2}SO{sub 4} and methylamine are very stable and can thus serve as possible nucleation sites. The present study leads us to conclude that the interactions of COA coexisting with H{sub 2}SO{sub 4} and common atmospheric bases in the Earth’s atmosphere may be an important factor affecting the stability of nucleating sulfuric acid clusters and that the impacts of COA on atmospheric nucleation should be studied in further details.« less

Glucose acutely decreases pH of secretory granules in mouse pancreatic islets. Mechanisms and influence on insulin secretion.

PubMed

Stiernet, Patrick; Guiot, Yves; Gilon, Patrick; Henquin, Jean-Claude

2006-08-04

Glucose-induced insulin secretion requires a rise in beta-cell cytosolic Ca2+ ([Ca2+]c) that triggers exocytosis and a mechanistically unexplained amplification of the action of [Ca2+]c. Insulin granules are kept acidic by luminal pumping of protons with simultaneous Cl- uptake to maintain electroneutrality. Experiments using patched, dialyzed beta-cells prompted the suggestion that acute granule acidification by glucose underlies amplification of insulin secretion. However, others found glucose to increase granular pH in intact islets. In this study, we measured islet granular pH with Lysosensor DND-160, a fluorescent dye that permits ratiometric determination of pH < 6 in acidic compartments. Stimulation of mouse islets with glucose reversibly decreased granular pH by mechanisms that are dependent on metabolism and Cl- ions but independent of changes in [Ca2+]c and protein kinase A or C activity. Granular pH was increased by concanamycin (blocker of the vesicular type H+-ATPase) > methylamine (weak base) > Cl- omission. Concanamycin and methylamine did not alter glucose-induced [Ca2+]c increase in islets but strongly inhibited the two phases of insulin secretion. Omission of Cl- did not affect the first phase but decreased the second phase of both [Ca2+]c and insulin responses. Neither experimental condition affected the [Ca2+]c rise induced by 30 mM KCl, but the insulin responses were inhibited by concanamycin > methylamine and not affected by Cl- omission. The amplification of insulin secretion by glucose was not suppressed. We conclude that an acidic granular pH is important for insulin secretion but that the acute further acidification produced by glucose is not essential for the augmentation of secretion via the amplifying pathway.

Metagenomic Analysis Revealed Methylamine and Ureide Utilization of Soybean-Associated Methylobacterium

PubMed Central

Minami, Tomoyuki; Anda, Misue; Mitsui, Hisayuki; Sugawara, Masayuki; Kaneko, Takakazu; Sato, Shusei; Ikeda, Seishi; Okubo, Takashi; Tsurumaru, Hirohito; Minamisawa, Kiwamu

2016-01-01

Methylobacterium inhabits the phyllosphere of a large number of plants. We herein report the results of comparative metagenome analyses on methylobacterial communities of soybean plants grown in an experimental field in Tohoku University (Kashimadai, Miyagi, Japan). Methylobacterium was identified as the most dominant genus (33%) among bacteria inhabiting soybean stems. We classified plant-derived Methylobacterium species into Groups I, II, and III based on 16S rRNA gene sequences, and found that Group I members (phylogenetically close to M. extorquens) were dominant in soybean-associated Methylobacterium. By comparing 29 genomes, we found that all Group I members possessed a complete set of genes for the N-methylglutamate pathway for methylamine utilization, and genes for urea degradation (urea carboxylase, urea amidolyase, and conventional urease). Only Group I members and soybean methylobacterial isolates grew in a culture supplemented with methylamine as the sole carbon source. They utilized urea or allantoin (a urea-related compound in legumes) as the sole nitrogen source; however, group III also utilized these compounds. The utilization of allantoin may be crucial in soybean-bacterial interactions because allantoin is a transported form of fixed nitrogen in legume plants. Soybean-derived Group I strain AMS5 colonized the model legume Lotus japonicus well. A comparison among the 29 genomes of plant-derived and other strains suggested that several candidate genes are involved in plant colonization such as csgG (curli fimbriae). Genes for the N-methylglutamate pathway and curli fimbriae were more abundant in soybean microbiomes than in rice microbiomes in the field. Based on these results, we discuss the lifestyle of Methylobacterium in the legume phyllosphere. PMID:27431374

Methylamine adsorption and decomposition on B12N12 nanocage: A density functional theory study

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Nurazar, Roghaye

2014-08-01

Density functional theory calculations are performed to investigate the adsorption and decomposition of methylamine (CH3NH2) on the surface of a B12N12 fullerene-like nanocage. Two adsorption types and two reaction channels are identified. It is found that the electrical conductivity of the nanocage can be modified upon the adsorption of CH3NH2. The pathways of CH3NH2 decomposition via bond scission of the Csbnd N and Nsbnd H bonds are examined. The results indicate that Nsbnd H bond scission is the most favorable pathway on the B12N12 surface. The side reaction that generates CH3 and NH2 fragments is endothermic by 15.6 kcal/mol with an energy-barrier height of 81.5 kcal/mol. For the CH3NH2 decomposition on the B12N12 surface, the rate-determining step appears to be as the following reaction: CH3NH → CH3N + H.

Catalysis by Methylamine Dehydrogenase and Electron Transfer to Amicyanin and Cytochrome C(551I) from Paracoccus Denitrificans.

NASA Astrophysics Data System (ADS)

Brooks, Harold Burns

1995-01-01

The quinoprotein methylamine dehydrogenase (MADH), a type I copper protein, amicyanin, and cytochrome c _{55li} form a physiologic ternary complex (Chen et al. (1994) Science 264, 86-90) in which electrons are transferred from tryptophan tryptophylquinone to copper to heme. The reduction of MADH by rm H_3- and rm D_3 -methylamine, the reoxidation of MADH by amicyanin, and the reduction of cytochrome c_{55li } by reduced amicyanin in the presence of MADH have been studied by stopped-flow spectroscopy. When rm CD_3NH_2 was used as a substrate for MADH a deuterium kinetic isotope effect of 17.2 was measured for the hydrogen abstraction step. The maximum deuterium kinetic isotope effect that was measured in steady-state kinetic experiments was 3.0. The temperature dependencies of the rate constants for the reaction of methylamine with MADH were also determined. An iminosemiquinone intermediate for the oxidation of substrate-reduced MADH by amicyanin was detected using stopped-flow spectroscopy, and the presence of the substrate derived nitrogen was confirmed by electron spin echo envelope modulation (ESEEM) spectroscopy. Marcus theory, which was used to analyze the electron transfer reaction between the dithionite-generated redox forms of MADH and amicyanin, gave values of 218 kJ rm mol^{ -1} (2.3 eV) for the reorganizational energy (lambda ) and 11.6 rm cm^{-1} for the coupling rm (H_{AB}). In contrast, the oxidation of substrate-reduced MADH by amicyanin was a gated electron transfer reaction with values for DeltaH* of 76 kJ rm mol^ {-1} and DeltaS* of -41 J rm mol^{ -1} ^circ K^ {-1}. These studies are consistent with the formation of transient unstable intermediates preceeding electron transfer between MADH and amicyanin. Preliminary investigations of the ternary complex of MADH, amicyanin, and cytochrome c_{55li } suggest two distinct cytochrome c _{55li} binding sites on amicyanin. This conclusion is supported by the biphasic nature of the stopped -flow trace, the inhibition of the rm k^ {fast}_{obs} by MADH, and the ionic strength dependence of the two phases. The slow phase had a rate of 3.1 rm s^ {-1} which is consistent with electron transfer between amicyanin and cytochrome c_ {55li} within the ternary complex. The fast phase does not exhibit saturation behavior, must have an electron transfer rate greater than 1000 rm s^{-1}, and likely involves a complex of amicyanin and cytochrome c_{55li } near the hydrophobic patch of amicyanin.

NMR Determination of Hydrogen Bond Thermodynamics in a Simple Diamide: A Physical Chemistry Experiment

ERIC Educational Resources Information Center

Morton, Janine G.; Joe, Candice L.; Stolla, Massiel C.; Koshland, Sophia R.; Londergan, Casey H.; Schofield, Mark H.

2015-01-01

Variable temperature NMR spectroscopy is used to determine the ?H° and ?S° of hydrogen bond formation in a simple diamide. In this two- or three-day experiment, students synthesize N,N'-dimethylmalonamide, dimethylsuccinamide, dimethylglutaramide, or dimethyladipamide from methylamine and the corresponding diester (typically in 50% recrystallized…

Glycine Betaine as a Direct Substrate for Methanogens (Methanococcoides spp.)

PubMed Central

Watkins, Andrew J.; Roussel, Erwan G.; Parkes, R. John

2014-01-01

Nine marine methanogenic Methanococcoides strains, including the type strains of Methanococcoides methylutens, M. burtonii, and M. alaskense, were tested for the utilization of N-methylated glycines. Three strains (NM1, PM2, and MKM1) used glycine betaine (N,N,N-trimethylglycine) as a substrate for methanogenesis, partially demethylating it to N,N-dimethylglycine, whereas none of the strains used N,N-dimethylglycine or sarcosine (N-methylglycine). Growth rates and growth yields per mole of substrate with glycine betaine (3.96 g [dry weight] per mol) were similar to those with trimethylamine (4.11 g [dry weight] per mol). However, as glycine betaine is only partially demethylated, the yield per methyl group was significantly higher than with trimethylamine. If glycine betaine and trimethylamine are provided together, trimethylamine is demethylated to dimethyl- and methylamine with limited glycine betaine utilization. After trimethylamine is depleted, dimethylamine and glycine betaine are consumed rapidly, before methylamine. Glycine betaine extends the range of substrates that can be directly utilized by some methanogens, allowing them to gain energy from the substrate without the need for syntrophic partners. PMID:24162571

Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov-Gerasimenko.

PubMed

Altwegg, Kathrin; Balsiger, Hans; Bar-Nun, Akiva; Berthelier, Jean-Jacques; Bieler, Andre; Bochsler, Peter; Briois, Christelle; Calmonte, Ursina; Combi, Michael R; Cottin, Hervé; De Keyser, Johan; Dhooghe, Frederik; Fiethe, Bjorn; Fuselier, Stephen A; Gasc, Sébastien; Gombosi, Tamas I; Hansen, Kenneth C; Haessig, Myrtha; Jäckel, Annette; Kopp, Ernest; Korth, Axel; Le Roy, Lena; Mall, Urs; Marty, Bernard; Mousis, Olivier; Owen, Tobias; Rème, Henri; Rubin, Martin; Sémon, Thierry; Tzou, Chia-Yu; Hunter Waite, James; Wurz, Peter

2016-05-01

The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples, a cometary origin was deduced from the (13)C isotopic signature. We report the presence of volatile glycine accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result demonstrates that comets could have played a crucial role in the emergence of life on Earth.

Prebiotic chemicals—amino acid and phosphorus—in the coma of comet 67P/Churyumov-Gerasimenko

PubMed Central

Altwegg, Kathrin; Balsiger, Hans; Bar-Nun, Akiva; Berthelier, Jean-Jacques; Bieler, Andre; Bochsler, Peter; Briois, Christelle; Calmonte, Ursina; Combi, Michael R.; Cottin, Hervé; De Keyser, Johan; Dhooghe, Frederik; Fiethe, Bjorn; Fuselier, Stephen A.; Gasc, Sébastien; Gombosi, Tamas I.; Hansen, Kenneth C.; Haessig, Myrtha; Jäckel, Annette; Kopp, Ernest; Korth, Axel; Le Roy, Lena; Mall, Urs; Marty, Bernard; Mousis, Olivier; Owen, Tobias; Rème, Henri; Rubin, Martin; Sémon, Thierry; Tzou, Chia-Yu; Hunter Waite, James; Wurz, Peter

2016-01-01

The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples, a cometary origin was deduced from the 13C isotopic signature. We report the presence of volatile glycine accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result demonstrates that comets could have played a crucial role in the emergence of life on Earth. PMID:27386550

The use of trimethylamine N-oxide as a primary precipitating agent and related methylamine osmolytes as cryoprotective agents for macromolecular crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, Haley; Venkat, Murugappan; Hti Lar Seng, Nang San

2012-01-01

The stabilizing osmolyte trimethylamine N-oxide (TMAO) is shown to be an efficient primary precipitant for protein crystal growth. In addition to TMAO, two other methylamine osmolytes, sarcosine and betaine, are shown to be effective cryoprotective agents for protein crystal cooling. Both crystallization and cryoprotection are often bottlenecks for high-resolution X-ray structure determination of macromolecules. Methylamine osmolytes are known stabilizers of protein structure. One such osmolyte, trimethylamine N-oxide (TMAO), has seen occasional use as an additive to improve macromolecular crystal quality and has recently been shown to be an effective cryoprotective agent for low-temperature data collection. Here, TMAO and the relatedmore » osmolytes sarcosine and betaine are investigated as primary precipitating agents for protein crystal growth. Crystallization experiments were undertaken with 14 proteins. Using TMAO, seven proteins crystallized in a total of 13 crystal forms, including a new tetragonal crystal form of trypsin. The crystals diffracted well, and eight of the 13 crystal forms could be effectively cryocooled as grown with TMAO as an in situ cryoprotective agent. Sarcosine and betaine produced crystals of four and two of the 14 proteins, respectively. In addition to TMAO, sarcosine and betaine were effective post-crystallization cryoprotective agents for two different crystal forms of thermolysin. Precipitation reactions of TMAO with several transition-metal ions (Fe{sup 3+}, Co{sup 2+}, Cu{sup 2+} and Zn{sup 2+}) did not occur with sarcosine or betaine and were inhibited for TMAO at lower pH. Structures of proteins from TMAO-grown crystals and from crystals soaked in TMAO, sarcosine or betaine were determined, showing osmolyte binding in five of the 12 crystals tested. When an osmolyte was shown to bind, it did so near the protein surface, interacting with water molecules, side chains and backbone atoms, often at crystal contacts.« less

Molecular characterization of the Hansenula polymorpha FLD1 gene encoding formaldehyde dehydrogenase.

Treesearch

Richard J. Baerends; Grietje J. Sulter; Thomas W. Jeffries; James M. Cregg; Marten Veenhuis

2002-01-01

Glutathione-dependent formaldehyde dehydrogenase (FLD) is a key enzyme required for the catabolism of methanol as a carbon source and certain primary amines, such as methylamine as nitrogen sources in methylotrophic yeasts. Here we describe the molecular characterization of the FLD1 gene from the yeast Hansenula polymorpha. Unlike the recently described Pichia pastoris...

Analysis of the MT1/MT2 Systems Involved in the Metabolism of One-Carbon Compounds in "Methanosarcina acetivorans" C2A

ERIC Educational Resources Information Center

Opulencia, Rina Bagsic

2009-01-01

Methanogens are strictly anaerobic Archaea that derive their energy for growth by reducing a limited number of substrates to methane. "Methanosarcina" spp. utilize the methylotrophic pathway to grow on methanol, methylamines and methylsulfides. These compounds enter the methylotrophic pathway as methyl-coenzyme M, the synthesis of which is…

Stabilization of sulfuric acid dimers by ammonia, methylamine, dimethylamine, and trimethylamine

NASA Astrophysics Data System (ADS)

Jen, Coty N.; McMurry, Peter H.; Hanson, David R.

2014-06-01

This study experimentally explores how ammonia (NH3), methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) affect the chemical formation mechanisms of electrically neutral clusters that contain two sulfuric acid molecules (dimers). Dimers may also contain undetectable compounds, such as water or bases, that evaporate upon ionization and sampling. Measurements were conducted using a glass flow reactor which contained a steady flow of humidified nitrogen with sulfuric acid concentrations of 107 to 109 cm-3. A known molar flow rate of a basic gas was injected into the flow reactor. The University of Minnesota Cluster Chemical Ionization Mass Spectrometer was used to measure the resulting sulfuric acid vapor and cluster concentrations. It was found that, for a given concentration of sulfuric acid vapor, the dimer concentration increases with increasing concentration of the basic gas, eventually reaching a plateau. The base concentrations at which the dimer concentrations saturate suggest NH3 < MA < TMA ≲ DMA in forming stabilized sulfuric acid dimers. Two heuristic models for cluster formation by acid-base reactions are developed to interpret the data. The models provide ranges of evaporation rate constants that are consistent with observations and leads to an analytic expression for nucleation rates that is consistent with atmospheric observations.

Chemical vapor deposition growth of boron-carbon-nitrogen layers from methylamine borane thermolysis products

NASA Astrophysics Data System (ADS)

Leardini, Fabrice; Flores, Eduardo; Galvis E, Andrés R.; Ferrer, Isabel J.; Ramón Ares, José; Sánchez, Carlos; Molina, Pablo; van der Meulen, Herko P.; Gómez Navarro, Cristina; López Polin, Guillermo; Urbanos, Fernando J.; Granados, Daniel; García-García, F. Javier; Demirci, Umit B.; Yot, Pascal G.; Mastrangelo, Filippo; Grazia Betti, Maria; Mariani, Carlo

2018-01-01

This work investigates the growth of B-C-N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B-C-N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C-N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B-C-N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

Secondary organic aerosol formation during evaporation of droplets containing atmospheric aldehydes, amines, and ammonium sulfate.

PubMed

Galloway, Melissa M; Powelson, Michelle H; Sedehi, Nahzaneen; Wood, Stephanie E; Millage, Katherine D; Kononenko, Julia A; Rynaski, Alec D; De Haan, David O

2014-12-16

Reactions of carbonyl compounds in cloudwater produce organic aerosol mass through in-cloud oxidation and during postcloud evaporation. In this work, postcloud evaporation was simulated in laboratory experiments on evaporating droplets that contain mixtures of common atmospheric aldehydes with ammonium sulfate (AS), methylamine, or glycine. Aerosol diameters were measured during monodisperse droplet drying experiments and during polydisperse droplet equilibration experiments at 75% relative humidity, and condensed-phase mass was measured in bulk thermogravimetric experiments. The evaporation of water from a droplet was found to trigger aldehyde reactions that increased residual particle volumes by a similar extent in room-temperature experiments, regardless of whether AS, methylamine, or glycine was present. The production of organic aerosol volume was highest from droplets containing glyoxal, followed by similar production from methylglyoxal or hydroxyacetone. Significant organic aerosol production was observed for glycolaldehyde, acetaldehyde, and formaldehyde only at elevated temperatures in thermogravimetric experiments. In many experiments, the amount of aerosol produced was greater than the sum of all solutes plus nonvolatile solvent impurities, indicating the additional presence of trapped water, likely caused by increasing aerosol-phase viscosity due to oligomer formation.

Automation of flow injection gas diffusion-ion chromatography for the nanomolar determination of methylamines and ammonia in seawater and atmospheric samples

PubMed Central

Gibb, Stuart W.; Wood, John W.; Fauzi, R.; Mantoura, C.

1995-01-01

The automation and improved design and performance of Flow Injection Gas Diffusion-Ion Chromatography (FIGD-IC), a novel technique for the simultaneous analysis of trace ammonia (NH3) and methylamines (MAs) in aqueous media, is presented. Automated Flow Injection Gas Diffusion (FIGD) promotes the selective transmembrane diffusion of MAs and NH3 from aqueous sample under strongly alkaline (pH > 12, NaOH), chelated (EDTA) conditions into a recycled acidic acceptor stream. The acceptor is then injected onto an ion chromatograph where NH3 and the MAs are fully resolved as their cations and detected conductimetrically. A versatile PC interfaced control unit and data capture unit (DCU) are employed in series to direct the selonoid valve switching sequence, IC operation and collection of data. Automation, together with other modifications improved both linearily (R2 > 0.99 MAs 0-100 nM, NH3 0-1000 nM) and precision (<8%) of FIGD-IC at nanomolar concentrations, compared with the manual procedure. The system was successfully applied to the determination of MAs and NH3 in seawater and in trapped particulate and gaseous atmospheric samples during an oceanographic research cruise. PMID:18925047

Intralines of quasi-conical intersections on torsion planes: methylamine as a case study.

PubMed

Levi, C; Halász, G J; Vibók, A; Bar, I; Zeiri, Y; Kosloff, R; Baer, M

2009-06-18

Recently we reported on a novel feature associated with the intersection of the two lowest states (1)A' and (1)A'' of the methylamine (J. Chem. Phys. 2008, 128, 244302). We established the existence of a finite (closed) line of conical intersections (ci), namely, a finite seam, located in the HC-NHH symmetry plane, a line that is formed by moving a single hydrogen on that plane while locking the positions of the (six) other atoms. In the present article, this study is extended to the corresponding torsion planes formed by rotating the methyl group around the CN axis. The torsion planes, in contrast with the HC-NHH symmetry plane, do not satisfy the symmetry feature that enables the seam just mentioned. Nevertheless, the calculated nonadiabatic coupling terms (NACTs) resemble features similar to those encountered in the HC-NHH symmetry plane. Following a tedious numerical study supported by a theoretical model (Section III), it was verified that these NACTs may become similar to those on the symmetry plane, sometimes even to the level of almost no distinction, but lack one basic feature; namely, they are not singular and therefore do not form topological effects.

Synthesizing Pt nanoparticles in the presence of methylamine: Impact of acetic acid treatment in the electrocatalytic activity of formic acid oxidation

NASA Astrophysics Data System (ADS)

Ooi, M. D. Johan; Aziz, A. Abdul

2017-05-01

Surfactant removal from the surface of platinum nanoparticles prepared by solution based method is a prerequisite process to accomplish a high catalytic activity for electrochemical reactions. Here, we report a possible approach of combining acid acetic with thermal treatment for improving catalytic performance of formic acid oxidation. This strategy involves conversion of amine to amide in acetic acid followed by surfactant removal via subsequent thermal treatment at 85 °C. This combined activation technique produced monodisperse nanoparticle with the size of 3 to 5 nm with enhanced formic acid oxidation activity, particularly in perchloric acid solution. Pt treated in 1 h of acetic acid and heat treatment of 9 h shows high electrochemical surface area value (27.6 m2/g) compares to Pt without activation (16.6 m2/g). The treated samples also exhibit high current stability of 0.3 mA/cm2 compares to the as-prepared mA/cm2). Shorter duration of acid wash and longer duration of heating process result in high electrocatalytic activity. This work demonstrates a possible technique in improving catalytic activity of platinum nanoparticles synthesized using methylamine as surfactant.

Cometary Glycine Detected in Stardust-Returned Samples

NASA Technical Reports Server (NTRS)

Elsila, Jamie E.; Glavin, D. P.; Dworkin, J. P.

2010-01-01

In January 2006, NASA's Stardust spacecraft returned samples from comet 81P/Wild 2 to Earth. The Stardust cometary collector consisted of aerogel cells lined with aluminum foils designed to capture impacting particles and facilitate removal of the aerogel. Preliminary examinations of these comet-exposed materials revealed a suite of organic compounds, including several amines and amino acids which were later examined in more detail. Methylamine (NH2CH3) and ethylamine (NH2C2H5) were detected in the exposed aerogel at concentrations greatly exceeding those found in control samples, while the amino acid glycine (NH2CH2COOH) was detected in several foil samples as well as in the comet-exposed aerogel. None of these three compounds had been previously detected in comets, although methylamine had been observed in the interstellar medium. Although comparison with control samples suggested that the detected glycine was cometary. the previous work was not able to conclusively identify its origin. Here, we present the results of compound-specific carbon isotopic analysis of glycine in Stardust cometary collector foils. Several foils from the interstellar side of the Stardust collector were also analyzed for amino acid abundance, but concentrations were too low to perform isotopic ana!ysis.

Time-dependent vibrational spectral analysis of first principles trajectory of methylamine with wavelet transform.

PubMed

Biswas, Sohag; Mallik, Bhabani S

2017-04-12

The fluctuation dynamics of amine stretching frequencies, hydrogen bonds, dangling N-D bonds, and the orientation profile of the amine group of methylamine (MA) were investigated under ambient conditions by means of dispersion-corrected density functional theory-based first principles molecular dynamics (FPMD) simulations. Along with the dynamical properties, various equilibrium properties such as radial distribution function, spatial distribution function, combined radial and angular distribution functions and hydrogen bonding were also calculated. The instantaneous stretching frequencies of amine groups were obtained by wavelet transform of the trajectory obtained from FPMD simulations. The frequency-structure correlation reveals that the amine stretching frequency is weakly correlated with the nearest nitrogen-deuterium distance. The frequency-frequency correlation function has a short time scale of around 110 fs and a longer time scale of about 1.15 ps. It was found that the short time scale originates from the underdamped motion of intact hydrogen bonds of MA pairs. However, the long time scale of the vibrational spectral diffusion of N-D modes is determined by the overall dynamics of hydrogen bonds as well as the dangling ND groups and the inertial rotation of the amine group of the molecule.

The structure and function of supported molybdenum nitride and molybdenum carbide hydrotreating catalysts

NASA Astrophysics Data System (ADS)

Dolce, Gregory Martin

1997-11-01

A series of gamma-Alsb2Osb3 supported molybdenum nitrides and carbides were prepared by the temperature programmed reaction of supported molybdates with ammonia and methane/hydrogen mixtures, respectively. In the first part of this research, the effects of synthesis heating rates and molybdenum loading on the catalytic properties of the materials were examined. A significant amount of excess carbon was deposited on the surface of the carbides during synthesis. The materials consisted of small particles which were very highly dispersed. Oxygen chemisorption indicated that the nitride particles may have been two-dimensional. The dispersion of the carbides, however, appeared to decrease as the loading increased. The catalysts were evaluated for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). The molybdenum loading had the largest effect on the activity of the materials. For the nitrides, the HDN and HDS activities were inverse functions of the loading. This suggested that the most active HDN and HDS sites were located at the perimeter of the two-dimensional particles. The HDN and HDS activities of the carbides followed the same trend as the oxygen uptake. This result suggested that oxygen titrated the active sites on the supported carbides. Selected catalysts were evaluated for methylcarbazole HDN, dibenzothiophene HDS, and dibenzofuran HDO. The activity and selectivity of the nitrides and carbides were competitive with a presulfided commercial catalyst. In the second part of this work, a series of supported nitrides and carbides were prepared using a wider range of loadings (5-30 wt% Mo). Thermogravimetric analysis was used to determine the temperature at which excess carbon was deposited on the carbides. By modifying the synthesis parameters, the deposition of excess carbon was effectively inhibited. The dispersions of the supported nitrides and carbides were constant and suggested that the materials consisted of two-dimensional raft-like particles. The HDN activity of the nitrides decreased as the loading increased, while that of the carbides was relatively constant. Carbon monoxide and methylamine adsorbed on the same types of sites on the nitrides and carbides. Infrared spectroscopy and temperature programmed desorption revealed that some methylamine underwent HDN on the nitrides and carbides. Carbon monoxide appeared to adsorb on two types of sites. One type of site adsorbed CO which desorbed upon heating while the other type of site adsorbed CO which dissociated when the material was heated. The relative amounts of desorbed CO and methylamine scaled with the activity of the nitrides suggesting that CO and methylamine titrated the active sites. It appeared that the active sites of the supported carbides were different from those on the supported nitrides. It was proposed that the active sites on the supported nitrides were at the perimeter of the two-dimensional particles while the active sites of the carbides were "on top" of the particles.

Detailed Kinetic Mechanism of the Combustion of Homogeneous Gaseous Mixtures with Participation of Oxygen-containing Oxidants

NASA Astrophysics Data System (ADS)

Baevich, V. Ya

1987-05-01

The kinetic mechanisms of the oxidation and combustion of hydrogen, methane, methyl alcohol, acetylene, ethylene, ethane, and methylamine, using oxygen as well as hydrogen peroxide and nitric acid as oxidants, are discussed. The calculated and experimental data obtained under static conditions, in a flow, during flame propagation, and in shock tubes are compared. The bibliography includes 184 references.

Inhibition of electron transport on the oxygen-evolving side of photosystem II by an antiserum to a polypeptide isolated from the thylakoid membrane.

PubMed

Schmid, G H; Menke, W; Koenig, F; Radunz, A

1976-01-01

A polypeptide fraction with the apparent molecular weight 11 000 was isolated from stroma-freed chloroplasts from Anthirrhinum majus. An antiserum to this polypeptide fraction inhibits photosynthetic electron transport in chloroplasts from Nicotiana tabacum. The relative degree of inhibition is pH dependent and has its maximum at pH 7.4. The maximal inhibition observed was 93%. The dependence of the inhibition on the amount of antiserum yields a sigmoidal curve which hints at a cooperative effect. A calculation of the Hill interaction coefficient gave the value of 10. The inhibition occurs on the water splitting side of photosystem II between the sites of electron donation of tetramethyl benzidine and diphenylcarbazide. Tetramethyl benzidine donates its electrons before the site where diphenylcarbazide feeds in its electrons. Analysis of the steady state level of the variable fluorescence also indicates that the inhibition site is on the water splitting side of photosystem II. Tris-washed chloroplasts are equally inhibited by the antiserum and the inhibition is also observed in the presence of an inhibitor of photophosphorylation like dicyclohexyl carbodiimide and in the presence of the uncoupler carbonylcyanide m-chlorophenyl hydrazone (CCCP) which means that the inhibitory action is directed towards the electron transport chain. Valinomycin which is supposed to affect the cation permeability of the thylakoid membrane has no influence on the inhibitory action of the antiserum. The same is valid for gramicidin. Methylamine on the other hand can induce a state in the thylakoids in which the antiserum is not effective. If the antibodies are already adsorbed prior to the methylamine addition then the high inhibitory effect by the antiserum remains unchanged upon addition of methylamine. From the experiments it follows that a component from the vicinity of photosystem II is accessible to antibodies that is, the component is located in the outer surface of the thylakoid membrane. It appears that the inhibitory effect is produced in the course of the light reaction.

Titanium (III) cation selective electrode based on synthesized tris(2pyridyl) methylamine ionophore and its application in water samples

NASA Astrophysics Data System (ADS)

Rezayi, Majid; Karazhian, Reza; Abdollahi, Yadollah; Narimani, Leila; Sany, Seyedeh Belin Tavakoly; Ahmadzadeh, Saeid; Alias, Yatimah

2014-04-01

The introduction of low detection limit ion selective electrodes (ISEs) may well pave the way for the determination of trace targets of cationic compounds. This research focuses on the detection of titanium (III) cation using a new PVC-membrane sensor based on synthesized tris(2pyridyl) methylamine (tpm) ionophore. The application and validation of the proposed sensor was done using potentiometric titration, inductively coupled plasma atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). The membrane sensor exhibited a Nernstian response to the titanium (III) cation over a concentration range of 1.0 × 10-6-1.0 × 10-2 M and pH range from 1-2.5. The Nernstian slope, the lower of detection (LOD), and the response time (t95%) of the proposed sensor were 29.17 +/- 0.24 mV/dec, 7.9 × 10-7 M, and 20 s, respectively. The direct determination of 4-39 μg/ml of titanium (III) standard solution showed an average recovery of 94.60 and a mean relative standard deviation of 1.8 at 100.0 μg/ml. Finally, the utilization of the electrodes as end-point indicators for potentiometric titration with EDTA solutions for titanium (III) sensor was successfully carried out.

Comparison of microelectrode, DMO, and methylamine methods for measuring intracellular pH.

PubMed

Boron, W F; Roos, A

1976-09-01

The intracellular pH (pHi) of giant barnacle muscle fibers was measured with glass microelectrodes and also calculated from the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO) and methylamine (MA). Simultaneously applying any two of these methods to muscle fibers of the same barnacle, we found the pH measured with an intracellular electrode (pH-Elec) to be about 0.06 higher than the DMO-derived pH (pH-DMO), and pH-DMO to be about 0.10 higher than the MA-derived pH (p-ma). in studies on the pHi of squid giant axons, we found that pH-Elec (7.35) and pH-DMO (7.36) were not significantly different. In the barnacle experiments, DMO required about 30 min to reach a steady-state distribution, while MA required more than 5 h. The deviations of pH-DMO and pH-MA from pH-Elec for the barnacle can be explained by a) an error in the assumed intracellular pKa' of DMO or MA, b) membrane permeability to the ionic form of DMO or MA, or c) intracellular compartmentalization. Included is a detailed study of the apparent dissociation constant of DMO as affected by temperature, and ionic strength and composition.

Ammonia permeability of the aquaglyceroporins from Plasmodium falciparum, Toxoplasma gondii and Trypansoma brucei.

PubMed

Zeuthen, Thomas; Wu, Binghua; Pavlovic-Djuranovic, Slavica; Holm, Lars M; Uzcategui, Nestor L; Duszenko, Michael; Kun, Jürgen F J; Schultz, Joachim E; Beitz, Eric

2006-09-01

Plasmodium falciparum uses amino acids from haemoglobin degradation mainly for protein biosynthesis. Glutamine, however, is mostly oxidized to 2-oxoglutarate to restore NAD(P)H + H+. In this process two molecules of ammonia are released. We determined an ammonia production of 9 mmol h(-1) per litre of infected red blood cells in the early trophozoite stage. External application of ammonia yielded a cytotoxic IC50 concentration of 2.8 mM. As plasmodia cannot metabolize ammonia it must be exported. Yet, no biochemical or genomic evidences exist that plasmodia possess classical ammonium transporters. We expressed the P. falciparum aquaglyceroporin (PfAQP) in Xenopus laevis oocytes and examined whether it may serve as an exit pathway for ammonia. We show that injected oocytes: (i) acidify the medium due to ammonia uptake, (ii) take up [14C]methylamine and [14C]formamide, (iii) swell in solution with formamide and acetamide and (iv) display an ammonia-induced NH4+-dependent clamp current. Further, a yeast strain lacking the endogenous aquaglyceroporin (Fps1) is rescued by expression of PfAQP which provides for the efflux of toxic methylamine. Ammonia permeability was similarly established for the aquaglyceroporins from Toxoplasma gondii and Trypanosoma brucei. Apparently, these aquaglyceroporins are important for the release of ammonia derived from amino acid breakdown.

Mapping the primary structure of copper/topaquinone-containing methylamine oxidase from Aspergillus niger.

PubMed

Lenobel, R; Sebela, M; Frébort, I

2005-01-01

The amino acid sequence of methylamine oxidase (MeAO) from the fungus Aspergillus niger was analyzed using mass spectrometry (MS). First, MeAO was characterized by an accurate molar mass of 72.4 kDa of the monomer measured using MALDI-TOF-MS and by a pI value of 5.8 determined by isoelectric focusing. MALDI-TOF-MS revealed a clear peptide mass fingerprint after tryptic digestion, which did not provide any relevant hit when searched against a nonredundant protein database and was different from that of A. niger amine oxidase AO-I. Tandem mass spectrometry with electrospray ionization coupled to liquid chromatography allowed unambiguous reading of six peptide sequences (11-19 amino acids) and seven sequence tags (4-15 amino acids), which were used for MS BLAST homology searching. MeAO was found to be largely homologous to a hypothetical protein AN7641.2 (EMBL/GenBank protein-accession code EAA61827) from Aspergillus nidulans FGSC A4 with a theoretical molar mass of 76.46 kDa and pI 6.14, which belongs to the superfamily of copper amine oxidases. The protein AN7641.2 is only little homologous to the amine oxidase AO-I (32% identity, 49 % similarity).

Infusible silazane polymer and process for producing same. [protective coatings

NASA Technical Reports Server (NTRS)

Burks, R. E., Jr.; Lacey, R. E.; Christy, C. L., Jr. (Inventor)

1967-01-01

Coatings of high thermal and chemical stability for application to metal, glass, ceramics, and other surfaces are formed by reacting diphenyldichlorosilane in the presence of triethylamine with a nitrogen base selected from the group consisting of ammonia and methylamine. The pl polymeric, noncrystalline reaction product is heated in a reaction zone open to the atmosphere at a temperature ranging from approximately 250 C to 450 C until the infusible polymer is formed.

Report of the M16 Rifle Review Panel. Volume 10, Appendix 9. Audit Trail of Chief of Staff, Army Actions and Decisions Concerning the M16

DTIC Science & Technology

1968-06-01

CHEMORECEPTORS CHEMOTAXIS CHEMOTHERAPEUTIC AGENTS CHEMOTHERAPY CHERRIES CHESAPEAKE BAY CHI SQUARE TEST CHICKENS CHIKUNGUNYA VIRUS CHILDREN CHILE...METHYL SULFOXIDE METHYLAL METHYLAMINE METHYLATION METHYLENE BLUE METHYLENES METRIC SYSTEM METROLOGY MEXICO MEXICO GULF MICA MICA CAPACITORS...NEUTRON TRANSPORT THEORY NEUTRONS NEVADA NEW BRUNSWICK NEW ENGLAND NEW GUINEA NEW HAMPSHIRE NEW JERSEY NEW MEXICO NEW YORK NEW YORK CITY

High-resolution modeling of gaseous methylamines over a polluted region in China: source-dependent emissions and implications of spatial variations

NASA Astrophysics Data System (ADS)

Mao, Jingbo; Yu, Fangqun; Zhang, Yan; An, Jingyu; Wang, Lin; Zheng, Jun; Yao, Lei; Luo, Gan; Ma, Weichun; Yu, Qi; Huang, Cheng; Li, Li; Chen, Limin

2018-06-01

Amines have received increasing attention in recent years because of their potential role in new particle formation in the atmosphere and their impact on aerosol chemistry. High concentrations of amines are expected to be limited to the vicinity of source regions due to their short lifetime, highlighting the necessity of having a better understanding of contributions of emissions from different source types. This study presents the first high-resolution model simulation of concentrations of methylamines on a regional scale over the Yangtze River Delta region in East China. The WRF-Chem with nested grids is used in model simulations. In contrast to the very limited existing modeling studies that assumed a fixed ratio (FR) of amines to total ammonia emission, we derive source-dependent ratios (SDR) that distinguish C1-amine (CH3NH2), C2-amines (C2H7N), C3-amines (C3H9N) emissions from five different source types (agriculture, residential, transportation, chemical industry, and other industry). The amines-to-ammonia mass emission ratios, estimated from previous measurements, are 0.026, 0.0015, 0.0011, 0.0011, and 0.0011 for C1-amine; 0.007, 0.0018, 0.0015, 0.01, and 0.0009 for C2-amines; and 0.0004, 0.0005, 0.00043, 0.0006, and 0.0004 for C3-amines for chemical-industrial, other industrial, agricultural, residential, and transportational sources, respectively. The simulated concentrations of C1-, C2-, and C3-amines, based on both FR and SDR, have been compared with field measurements at a suburban site in Nanjing and at an urban site in Shanghai, China. SDR substantially improves the ability of the model in capturing the observed concentrations of methylamines. Concentrations of C1-, C2-, and C3-amines in the surface layer in the Yangtze River Delta region are generally in the range of 2-20, 5-50, and 0.5-4 pptv. Vertically, the concentrations of C1-, C2-, and C3-amines decrease quickly with altitude, dropping by a factor of ˜ 10 from the surface to ˜ 900 hPa. Results from the present study are critical to evaluating potential roles of amines in nucleation and chemical processes in polluted air.

Studies Towards the Leucetta-derived Alkaloids Spirocalcaridine A and B - Possible Biosynthetic Implications.

PubMed

Koswatta, Panduka B; Das, Jayanta; Yousufuddin, Muhammed; Lovely, Carl J

2015-04-01

An exploration of an abiotic approach to spirocalcaridines A and B is described centered on electrophile-induced dearomatizing spirocyclization of aryl enyne derivatives. Elaboration of the α-iodoenone via an Ullmann-like, copper-catalyzed amidation provided a formamide which upon treatment with methylamine undergoes a dienol-arene rearrangement, providing the corresponding kealiinine-like framework. This observation suggests a possible biosynthetic links between the spirocalcaridines and the naphthimidazole group of Leucetta alkaloids.

Titanium (III) cation selective electrode based on synthesized tris(2pyridyl) methylamine ionophore and its application in water samples

PubMed Central

Rezayi, Majid; Karazhian, Reza; Abdollahi, Yadollah; Narimani, Leila; Sany, Seyedeh Belin Tavakoly; Ahmadzadeh, Saeid; Alias, Yatimah

2014-01-01

The introduction of low detection limit ion selective electrodes (ISEs) may well pave the way for the determination of trace targets of cationic compounds. This research focuses on the detection of titanium (III) cation using a new PVC-membrane sensor based on synthesized tris(2pyridyl) methylamine (tpm) ionophore. The application and validation of the proposed sensor was done using potentiometric titration, inductively coupled plasma atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). The membrane sensor exhibited a Nernstian response to the titanium (III) cation over a concentration range of 1.0 × 10−6–1.0 × 10−2 M and pH range from 1–2.5. The Nernstian slope, the lower of detection (LOD), and the response time (t95%) of the proposed sensor were 29.17 ± 0.24 mV/dec, 7.9 × 10−7 M, and 20 s, respectively. The direct determination of 4–39 μg/ml of titanium (III) standard solution showed an average recovery of 94.60 and a mean relative standard deviation of 1.8 at 100.0 μg/ml. Finally, the utilization of the electrodes as end-point indicators for potentiometric titration with EDTA solutions for titanium (III) sensor was successfully carried out. PMID:24722576

Combined ab initio/empirical approach for optimization of Lennard-Jones parameters for polar-neutral compounds.

PubMed

Chen, I Jen; Yin, Daxu; MacKerell, Alexander D

2002-01-30

The study of small functionalized organic molecules in aqueous solution is a useful step toward gaining a basic understanding of the behavior of biomolecular systems in their native aqueous environment. Interest in studying amines and fluorine-substituted compounds has risen from their intrinsic physicochemical properties and their prevalence in biological and pharmaceutical compounds. In the present study, a previously developed approach which optimizes Lennard-Jones (LJ) parameters via the use of rare gas atoms combined with the reproduction of experimental condensed phase properties was extended to polar-neutral compounds. Compounds studied included four amines (ammonia, methylamine, dimethylamine, and trimethylamine) and three fluoroethanes (1-fluoroethane, 1,1-difluoroethane, and 1,1,1-trifluoroethane). The resulting force field yielded heats of vaporization and molecular volumes in excellent agreement with the experiment, with average differences less than 1%. The current amine CHARMM parameters successfully reproduced experimental aqueous solvation data where methylamine is more hydrophilic than ammonia, with hydrophobicity increasing with additional methylation on the nitrogen. For both the amines and fluoroethanes the parabolic relationship of the extent of methylation or fluorination, respectively, to the heats of vaporization were reproduced by the new parameters. The present results are also discussed with respect to the impact of parameterization approach to molecular details obtained from computer simulations and to the unique biological properties of fluorine in pharmaceutical compounds.

Torsion-inversion tunneling patterns in the CH-stretch vibrationally excited states of the G12 family of molecules including methylamine.

PubMed

Dawadi, Mahesh B; Bhatta, Ram S; Perry, David S

2013-12-19

Two torsion-inversion tunneling models (models I and II) are reported for the CH-stretch vibrationally excited states in the G12 family of molecules. The torsion and inversion tunneling parameters, h(2v) and h(3v), respectively, are combined with low-order coupling terms involving the CH-stretch vibrations. Model I is a group theoretical treatment starting from the symmetric rotor methyl CH-stretch vibrations; model II is an internal coordinate model including the local-local CH-stretch coupling. Each model yields predicted torsion-inversion tunneling patterns of the four symmetry species, A, B, E1, and E2, in the CH-stretch excited states. Although the predicted tunneling patterns for the symmetric CH-stretch excited state are the same as for the ground state, inverted tunneling patterns are predicted for the asymmetric CH-stretches. The qualitative tunneling patterns predicted are independent of the model type and of the particular coupling terms considered. In model I, the magnitudes of the tunneling splittings in the two asymmetric CH-stretch excited states are equal to half of that in the ground state, but in model II, they differ when the tunneling rate is fast. The model predictions are compared across the series of molecules methanol, methylamine, 2-methylmalonaldehyde, and 5-methyltropolone and to the available experimental data.

Orthorhombic fulleride (CH3NH2)K3C60 close to Mott-Hubbard instability: Ab initio study

NASA Astrophysics Data System (ADS)

Potočnik, Anton; Manini, Nicola; Komelj, Matej; Tosatti, Erio; Arčon, Denis

2012-08-01

We study the electronic structure and magnetic interactions in methylamine-intercalated orthorhombic alkali-doped fullerene (CH3NH2)K3C60 within the density functional theory. As in the simpler ammonia intercalated compound (NH3)K3C60, the orthorhombic crystal-field anisotropy Δ lifts the t1u triple degeneracy at the Γ point and drives the system deep into the Mott-insulating phase. However, the computed Δ and conduction electron bandwidth W cannot alone account for the abnormally low experimental Néel temperature, TN=11 K, of the methylamine compound, compared to the much higher value TN=40 K of the ammonia one. Significant interactions between CH3NH2 and C603- are responsible for the stabilization of particular fullerene-cage distortions and the ensuing low-spin S=1/2 state. These interactions also seem to affect the magnetic properties, as interfullerene exchange interactions depend on the relative orientation of deformations of neighboring C603- molecules. For the ferro-orientational order of CH3NH2-K+ groups we find an apparent reduced dimensionality in magnetic exchange interactions, which may explain the suppressed Néel temperature. The disorder in exchange interactions caused by orientational disorder of CH3NH2-K+ groups could further contribute to this suppression.

Studies Towards the Leucetta-derived Alkaloids Spirocalcaridine A and B – Possible Biosynthetic Implications

PubMed Central

Koswatta, Panduka B.; Das, Jayanta; Yousufuddin, Muhammed; Lovely, Carl J.

2015-01-01

An exploration of an abiotic approach to spirocalcaridines A and B is described centered on electrophile-induced dearomatizing spirocyclization of aryl enyne derivatives. Elaboration of the α–iodoenone via an Ullmann-like, copper-catalyzed amidation provided a formamide which upon treatment with methylamine undergoes a dienol-arene rearrangement, providing the corresponding kealiinine-like framework. This observation suggests a possible biosynthetic links between the spirocalcaridines and the naphthimidazole group of Leucetta alkaloids. PMID:26257576

Palladium-Catalyzed α-Arylation of Aryl Nitromethanes

PubMed Central

2015-01-01

Catalytic conditions for the α-arylation of aryl nitromethanes have been discovered using parallel microscale experimentation, despite two prior reports of the lack of reactivity of these aryl nitromethane precursors. The method efficiently provides a variety of substituted, isolable diaryl nitromethanes. In addition, it is possible to sequentially append two different aryl groups to nitromethane. Mild oxidation conditions were identified to afford the corresponding benzophenones via the Nef reaction, and reduction conditions were optimized to afford several diaryl methylamines. PMID:26584680

Isolation and Properties of Enterococcus hirae Mutants Defective in the Potassium/Proton Antiport System

PubMed Central

Kakinuma, Yoshimi; Igarashi, Kazuei

1999-01-01

A K+/H+ antiporter regulates cytoplasmic pH in Enterococcus hirae growing at alkaline pH. Mutants defective in this antiport activity were alkaline pH sensitive. One mutant, Pop1, lacked both K+/methylamine exchange at pH 9.5 and concomitant acidification of cytoplasmic pH. Pop1 grew well at pHs below 8 but did not at pHs above 9, conditions under which cytoplasmic pH was not fully acidified. PMID:10383981

Regulation of Ca(2+)-dependent protein turnover in skeletal muscle by thyroxine

NASA Technical Reports Server (NTRS)

Zeman, Richard J.; Bernstein, Paul L.; Ludemann, Robert; Etlinger, Joseph D.

1986-01-01

Dantrolene, an agent that inhibits Ca(2+) mobilization, improved protein balance in skeletal muscle, as thyroid status was increased, by altering rates of protein synthesis and degradation. Thyroxine (T4) caused increases in protein degradation that were blocked by leupeptin, a proteinase inhibitor previously shown to inhibit Ca(2+)-dependent nonlysosomal proteolysis in these muscles. In addition, T4 abolished sensitivity to the lysosomotropic agent methylamine and the autophagy inhibitor 3-methyladenine, suggesting that T4 inhibits autophagic/lysosomal proteolysis.

The effect of formaldehyde and nitrogen-containing compounds on the size and volume of aerosol particles

NASA Astrophysics Data System (ADS)

Millage, K.; Galloway, M. M.; De Haan, D. O.

2012-12-01

Atmospheric aerosol can interact with clouds in many ways, often resulting in the redistribution or absorption of solar energy or changes in precipitation efficiency. Secondary organic aerosol (SOA) in particular has been linked to climate change and a reduction in the number and size of cloud particles. The reactions of nitrogen containing compounds (primary amines, amino acids and ammonium sulfate) with carbonyl compounds (such as formaldehyde and glycolaldehyde) are potential sources of SOA. Aerosol containing formaldehyde and nitrogen-containing compounds (glycine, methylamine, arginine, or ammonium sulfate) was generated from buffered solutions (pH 5.4) using a nebulizer. The aerosol was then equilibrated into a chamber containing humid air (82-84% RH), and particle sizes were measured using a SMPS system over a period of 1 hour in order to examine how the size and volume of the aerosol particles changed. Formaldehyde concentrations were varied over multiple experiments. Arginine displayed a trend of increasing relative particle size with increasing formaldehyde concentration. Ammonium sulfate and formaldehyde displayed a decrease in relative particle sizes from 0:1 to 2:1 ratios of formaldehyde to ammonium sulfate, but then an increase in relative particle sizes with increasing amounts of formaldehyde. Similarly, glycine and methylamine initially displayed decreasing relative particle sizes, until reaching a 1:1 ratio of each to formaldehyde at which point the relative particle sizes steadily increased. These effects were likely caused by the evaporation of first-generation imine products.

Structural, optical, and electrical properties of PbSe nanocrystal solids treated thermally or with simple amines.

PubMed

Law, Matt; Luther, Joseph M; Song, Qing; Hughes, Barbara K; Perkins, Craig L; Nozik, Arthur J

2008-05-07

We describe the structural, optical, and electrical properties of films of spin-cast, oleate-capped PbSe nanocrystals that are treated thermally or chemically in solutions of hydrazine, methylamine, or pyridine to produce electronically coupled nanocrystal solids. Postdeposition heat treatments trigger nanocrystal sintering at approximately 200 degrees C, before a substantial fraction of the oleate capping group evaporates or pyrolyzes. The sintered nanocrystal films have a large hole density and are highly conductive. Most of the amine treatments preserve the size of the nanocrystals and remove much of the oleate, decreasing the separation between nanocrystals and yielding conductive films. X-ray scattering, X-ray photoelectron and optical spectroscopy, electron microscopy, and field-effect transistor electrical measurements are used to compare the impact of these chemical treatments. We find that the concentration of amines adsorbed to the NC films is very low in all cases. Treatments in hydrazine in acetonitrile remove only 2-7% of the oleate yet result in high-mobility n-type transistors. In contrast, ethanol-based hydrazine treatments remove 85-90% of the original oleate load. Treatments in pure ethanol strip 20% of the oleate and create conductive p-type transistors. Methylamine- and pyridine-treated films are also p-type. These chemically treated films oxidize rapidly in air to yield, after short air exposures, highly conductive p-type nanocrystal solids. Our results aid in the rational development of solar cells based on colloidal nanocrystal films.

A new cofactor in prokaryotic enzyme: Tryptophan tryptophylquinone as the redox prosthetic group in methylamine dehydrogenase

DOE Office of Scientific and Technical Information (OSTI.GOV)

McIntire, W.S.; Wemmer, D.E.; Chistoserdov, A.

Methylamine dehydrogenase (MADH), an {alpha}{sub 2}{beta}{sub 2} enzyme from numerous methylotrophic soil bacteria, contains a novel quinonoid redox prosthetic group that is covalently bound to its small {beta} subunit through two amino acyl residues. A comparison of the amino acid sequence deduced from the gene sequence of the small subunit for the enzyme from Methylobacterium extorquens AM1 with the published amino acid sequence obtained by Edman degradation method, allowed the identification of the amino acyl constituents of the cofactor as two tryptophyl residues. This information was crucial for interpreting {sup 1}H and {sup 13}C nuclear magnetic resonance, and mass spectralmore » data collected for the semicarbazide- and carboxymethyl-derivatized bis(tripeptidyl)-cofactor of MADH from bacterium W3A1. The cofactor is composed of two cross-linked tryptophyl residues. Although there are many possible isomers, only one is consistent with all the data: The first tryptophyl residue in the peptide sequence exists as an indole-6,7-dione, and is attached at its 4 position to the 2 position of the second, otherwise unmodified, indole side group. Contrary to earlier reports, the cofactor of MADH is not 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), a derivative thereof, of pro-PQQ. This appears to be the only example of two cross-linked, modified amino acyl residues having a functional role in the active site of an enzyme, in the absence of other cofactors or metal ions.« less

Elucidation of the trigonelline degradation pathway reveals previously undescribed enzymes and metabolites.

PubMed

Perchat, Nadia; Saaidi, Pierre-Loïc; Darii, Ekaterina; Pellé, Christine; Petit, Jean-Louis; Besnard-Gonnet, Marielle; de Berardinis, Véronique; Dupont, Maeva; Gimbernat, Alexandra; Salanoubat, Marcel; Fischer, Cécile; Perret, Alain

2018-05-08

Trigonelline (TG; N- methylnicotinate) is a ubiquitous osmolyte. Although it is known that it can be degraded, the enzymes and metabolites have not been described so far. In this work, we challenged the laboratory model soil-borne, gram-negative bacterium Acinetobacter baylyi ADP1 (ADP1) for its ability to grow on TG and we identified a cluster of catabolic, transporter, and regulatory genes. We dissected the pathway to the level of enzymes and metabolites, and proceeded to in vitro reconstruction of the complete pathway by six purified proteins. The four enzymatic steps that lead from TG to methylamine and succinate are described, and the structures of previously undescribed metabolites are provided. Unlike many aromatic compounds that undergo hydroxylation prior to ring cleavage, the first step of TG catabolism proceeds through direct cleavage of the C5-C6 bound, catalyzed by a flavin-dependent, two-component oxygenase, which yields ( Z )-2-(( N- methylformamido)methylene)-5-hydroxy-butyrolactone (MFMB). MFMB is then oxidized into ( E )-2-(( N- methylformamido) methylene) succinate (MFMS), which is split up by a hydrolase into carbon dioxide, methylamine, formic acid, and succinate semialdehyde (SSA). SSA eventually fuels up the TCA by means of an SSA dehydrogenase, assisted by a Conserved Hypothetical Protein. The cluster is conserved across marine, soil, and plant-associated bacteria. This emphasizes the role of TG as a ubiquitous nutrient for which an efficient microbial catabolic toolbox is available.

Survivability and reactivity of glycine and alanine in early oceans: effects of meteorite impacts.

PubMed

Umeda, Yuhei; Fukunaga, Nao; Sekine, Toshimori; Furukawa, Yoshihiro; Kakegawa, Takeshi; Kobayashi, Takamichi; Nakazawa, Hiromoto

2016-01-01

Prebiotic oceans might have contained abundant amino acids, and were subjected to meteorite impacts, especially during the late heavy bombardment. It is so far unknown how meteorite impacts affected amino acids in the early oceans. Impact experiments were performed under the conditions where glycine was synthesized from carbon, ammonia, and water, using aqueous solutions containing (13)C-labeled glycine and alanine. Selected amino acids and amines in samples were analyzed with liquid chromatography-mass spectrometry (LC/MS). In particular, the (13)C-labeled reaction products were analyzed to distinguish between run products and contaminants. The results revealed that both amino acids survived partially in the early ocean through meteorite impacts, that part of glycine changed into alanine, and that large amounts of methylamine and ethylamine were formed. Fast decarboxylation was confirmed to occur during such impact processes. Furthermore, the formation of n-butylamine, detected only in the samples recovered from the solutions with additional nitrogen and carbon sources of ammonia and benzene, suggests that chemical reactions to form new biomolecules can proceed through marine impacts. Methylamine and ethylamine from glycine and alanine increased considerably in the presence of hematite rather than olivine under similar impact conditions. These results also suggest that amino acids present in early oceans can contribute further to impact-induced reactions, implying that impact energy plays a potential role in the prebiotic formation of various biomolecules, although the reactions are complicated and depend upon the chemical environments as well.

Prebiotic synthesis and degradation of amino acids by UV-irradiation at room temperature and 77K.

NASA Astrophysics Data System (ADS)

Mita, H.; Shimoyama, A.

Amino acids (AAs) were synthesized prebioticaly by UV irradiation to aqueous solution of amines and nitriles, and mixtures of graphite-ammonia-water (GAW mix.) at room temperature (RT, model of the primitive ocean) and 77 K (model of comet ice), using a Xe excimer lamp (max is 172 nm) and a low-pressure mercury lamp (max is 185/254 nm). Degradation of glycine and, degradation and racemization of aspartic acid were carried out by UV irradiation at RT. AAs in the irradiated samples were determined quantitatively by a gas chromatograph combined with a mass spectrometer after derivatized with HCl/2-propanol and trifluoroacetic anhydride. Maximum 16 hydrolyzed AAs from C2 to C6 were detected quantitatively. Amino acids have chiral center were nearly racemic. Therefore, those amino acids were not contaminants. In the most case, glycine was the most abundant AA and its concentration was 4.1 μmol/l from 1mmol/l acetonitrile solu. at RT for 3 h, 1 nmol/l from 100 mmol/l acetonitrile solu. at 77K for 1 h, 3.8?μmol/l from 10 mmol/l methylamine solu. at RT for 15 h, 278 μmol/l from 1 mol/l methylamine solu. At 77K for 4h, and 38.6 pmol/g-Carbon from GAW mix. at RT for 24 h. Maximum producing time of glycine from acetonitrile was 3 h and the shortest, that from GAW mix. was the longest among our experiments. Amount of glycine was decreased in gradually, after maximum producing time. Yields of glycine from acetonitrile and methylamine at 77K were lower than those at RT. Amounts of large AAs were lower than those of small AAs as glycine and alanine. Half-life time of glycine UV irradiation at RT was nearly 30 min. and similar to that of aspartic acid. Half-life time of racemization of aspartic acid was 2.1 h. It was able to confirm that a lot of AAs were synthesized by UV irradiation in the model experiments of primitive environments, even in simulated comet ice, from different starting materials. AA formation from developed material, as acetonitrile was more rapid and higher yield than that from primitive material as GAW mix. Degradation rate of AAs was faster than formation rate of AAs. Therefore, some protective systems are required for accumulation of AAs.

Effects of coordination agents on the morphology of CdS nanocrystallites synthesized by the hydrothermal method

NASA Astrophysics Data System (ADS)

Nie, Qiulin; Yuan, Qiuli; Chen, Weixiang; Xu, Zhude

2004-05-01

CdS nanocrystallites were synthesized by the hydrothermal method and characterized by XRD, TEM, and XPS, respectively. Different coordination agents were chosen as the template to investigate their effects on the product morphology. It was found that the CdS nanocrystallites displayed a rod-like shape when ethylenediamine or methylamine were employed as the template. In contrast, only nanoparticles of CdS were observed when ammonia or pyridine were used. Based on our experimental results, a complex structure-controlling mechanism is proposed.

Preliminary Problem Definition Study of 48 Munitions Related Chemicals. Volume I. Explosives Related Chemicals

DTIC Science & Technology

1978-04-01

fungicide additive to prevent chemical "peal burn" in citrus fruits, and in the textile industry for improved shrinkproofing, dye...1967 undiluted oral Rabbits, 3 1.6-1.9 L0100 Treon at al., 1943 "young" *.a. oral mice 2.78 24 hr LD50 Caujolle & Caujolls, 1965 undiluted i.p. Mice 1.35...presented in Table IV-10. In general, che acute toxicity of the methylamines to mammals is fairly low with LD50 ’s averaging several hundred mg/kg

Two-step iron(0)-mediated N-demethylation of N-methyl alkaloids.

PubMed

Kok, Gaik B; Pye, Cory C; Singer, Robert D; Scammells, Peter J

2010-07-16

A mild and simple two-step Fe(0)-mediated N-demethylation of a number of tertiary N-methyl alkaloids is described. The tertiary N-methylamine is first oxidized to the corresponding N-oxide, which is isolated as the hydrochloride salt. Subsequent treatment of the N-oxide hydrochloride with iron powder readily provides the N-demethylated amine. Representative substrates include a number of opiate and tropane alkaloids. Key intermediates in the synthesis of semisynthetic 14-hydroxy pharmaceutical opiates such as oxycodone and oxymorphone are also readily N-demethylated using this method.

Graphene-supported Ag-based core-shell nanoparticles for hydrogen generation in hydrolysis of ammonia borane and methylamine borane.

PubMed

Yang, Lan; Luo, Wei; Cheng, Gongzhen

2013-08-28

Well-dispersed magnetically recyclable core-shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min(-1) (mol Ag)(-1)), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs.

Cultured rat vascular smooth muscle cells are resistant to methylamine toxicity: no correlation to semicarbazide-sensitive amine oxidase

NASA Technical Reports Server (NTRS)

Langford, S. D.; Trent, M. B.; Boor, P. J.

2001-01-01

Methylamine (MA), a component of serum and a metabolite of nicotine and certain insecticides and herbicides, is metabolized by semicarbazide-sensitive amine oxidase (SSAO). MA is toxic to cultured human umbilical vein and calf pulmonary artery endothelial cells. Endothelial cells, which do not exhibit endogenous SSAO activity, are exposed to SSAO circulating in serum. In contrast, vascular smooth muscle cells (VSMC) do exhibit innate SSAO activity both in vivo and in vitro. This property, together with the critical localization of VSMC within the arterial wall, led us to investigate the potential toxicity of MA to VSMC. Cultured rat VSMC were treated with MA (10-5 to 1 M). In some cultures, SSAO was selectively inhibited with semicarbazide or MDL-72145 [(E)-2-(3,4-dimethoxyphenyl)-3-fluoroallylamine]. Cytotoxicity was measured via MTT, vital dye exclusion, and clonogenic assays. MA proved to be toxic to VSMC only at relatively high concentrations (LC(50) of 0.1 M). The inhibition of SSAO with semicarbazide or MDL-72145 did not increase MA toxicity, suggesting that the production of formaldehyde via tissue-bound, SSAO-mediated MA metabolism does not play a role in the minimal toxicity observed in isolated rat VSMC. The omission of fetal calf serum (FCS), which contains high SSAO activity, from media similarly showed little effect on cytotoxicity. We conclude that VSMC--in contrast to previous results in endothelial cells--are relatively resistant to MA toxicity, and SSAO does not play a role in VSMC injury by MA.

Gd3+-DTPA-bis (N-methylamine) - anionic linear globular Dendrimer-G1; a more efficient MRI contrast media.

PubMed

Ghalandarlaki, N; Mohammadi, T D; Agha Babaei, R; Tabasi, M A; Keyhanvar, P; Mehravi, B; Yaghmaei, P; Cohan, R A; Ardestani, M S

2014-02-01

By advancing of molecular imaging techniques, magnetic resonance imaging (MRI) is becoming an increasingly important tool in early diagnosis. Researchers have found new ways to increase contrast of MRI images.Therefore some types of drug known as contrast media are produced. Contrast media improve the visibility of internal body structures in MRI images. Gadodiamide (Omniscan®) is one of these contrast media which is produced commercially and used clinically. In this study Gadodiamide was first synthesized and then qualitative and quantitative methods were carried out to ensure the proper synthesis of this drug then to increase the efficiency of this contrast medium use dendrimer that is one kind of nano particle. This dendrimer has a polyethylene glycol (PEG) core and citric acid branches. After dendrimer attached to Gadodiamide to ensure the proper efficient connection between them the stability studies were carried out and cytotoxicity of the drug was evaluated. Finally, after ensuring the non-toxicity of the drug, in vivo studies (injected into mice) MR imaging was performed to examine the impact of synthesis drug on the resolution of image.The result obtained from this study demonstrated that the attachment of Gadodiamide to dendrimer reduces its cytotoxicity and also improved resolution of image. Also the new contrast media (Gd3+-DTPA- bis [N-methylamine] - Dendrimer) - unlike Omniscan® - is biodegradable and able to enter the HEPG2 cell line. The results confirm the hypothesis that using dendrimer to synthesize this new nano contrast medium increases its effectiveness. © Georg Thieme Verlag KG Stuttgart · New York.

Genome of Methylobacillus flagellatus, Molecular Basis for Obligate Methylotrophy, and Polyphyletic Origin of Methylotrophy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chistoserdova, L; Lapidus, A; Han, C

Along with methane, methanol and methylated amines represent important biogenic atmospheric constituents; thus, not only methanotrophs but also nonmethanotrophic methylotrophs play a significant role in global carbon cycling. The complete genome of a model obligate methanol and methylamine utilizer, Methylobacillus flagellatus (strain KT) was sequenced. The genome is represented by a single circular chromosome of approximately 3 Mbp, potentially encoding a total of 2,766 proteins. Based on genome analysis as well as the results from previous genetic and mutational analyses, methylotrophy is enabled by methanol and methylamine dehydrogenases and their specific electron transport chain components, the tetrahydromethanopterin-linked formaldehyde oxidation pathwaymore » and the assimilatory and dissimilatory ribulose monophosphate cycles, and by a formate dehydrogenase. Some of the methylotrophy genes are present in more than one (identical or nonidentical) copy. The obligate dependence on single-carbon compounds appears to be due to the incomplete tricarboxylic acid cycle, as no genes potentially encoding alpha-ketoglutarate, malate, or succinate dehydrogenases are identifiable. The genome of M. flagellatus was compared in terms of methylotrophy functions to the previously sequenced genomes of three methylotrophs, Methylobacterium extorquens (an alphaproteobacterium, 7 Mbp), Methylibium petroleiphilum (a betaproteobacterium, 4 Mbp), and Methylococcus capsulatus (a gammaproteobacterium, 3.3 Mbp). Strikingly, metabolically and/or phylogenetically, the methylotrophy functions in M. flagellatus were more similar to those in M. capsulatus and M. extorquens than to the ones in the more closely related M. petroleiphilum species, providing the first genomic evidence for the polyphyletic origin of methylotrophy in Betaproteobacteria.« less

Hydration of the sulfuric acid-methylamine complex and implications for aerosol formation.

PubMed

Bustos, Danielle J; Temelso, Berhane; Shields, George C

2014-09-04

The binary H2SO4-H2O nucleation is one of the most important pathways by which aerosols form in the atmosphere, and the presence of ternary species like amines increases aerosol formation rates. In this study, we focus on the hydration of a ternary system of sulfuric acid (H2SO4), methylamine (NH2CH3), and up to six waters to evaluate its implications for aerosol formation. By combining molecular dynamics (MD) sampling with high-level ab initio calculations, we determine the thermodynamics of forming H2SO4(NH2CH3)(H2O)n, where n = 0-6. Because it is a strong acid-base system, H2SO4-NH2CH3 quickly forms a tightly bound HSO4(-)-NH3CH3(+) complex that condenses water more readily than H2SO4 alone. The electronic binding energy of H2SO4-NH2CH3 is -21.8 kcal mol(-1) compared with -16.8 kcal mol(-1) for H2SO4-NH3 and -12.8 kcal mol(-1) for H2SO4-H2O. Adding one to two water molecules to the H2SO4-NH2CH3 complex is more favorable than adding to H2SO4 alone, yet there is no systematic difference for n ≥ 3. However, the average number of water molecules around H2SO4-NH2CH3 is consistently higher than that of H2SO4, and it is fairly independent of temperature and relative humidity.

Laboratory controls of precursor and temperature on the kinetics and isotopic fractionations of microbial methane for deep subsurface environments

NASA Astrophysics Data System (ADS)

Ling, Y.; Lin, L.; Wang, P.; Sun, C.

2009-12-01

In subsurface environments, the mineralization of organic carbon involves complex interactions among geological and microbial processes. As the most reduced form and the shortest hydrocarbon chain, methane, is the final product of both microbial degradation and thermal-cracking of organic matter, it serves as the connection of carbon cycles between different reservoirs. Of various mechanisms for methane formation, microbial methane constitutes 85% of the total methane inventory investigated by far. However, the mechanisms and resultant carbon isotope fingerprints of methanogenesis in environments still remained largely unknown. The types of precursors and temperature might be the most critical factors governing methanogenesis. Lots of studies have been investigating the mechanisms responsible for methanogenesis by pure cultures, but it still remains obscure with regard to which precursors are predominantly utilized by methanogens in natural settings. The effect of temperature is especially prominent for anoxic sediments within which the temperature increases with depth in accordance with the local geotherm. Commonly observed temperatures for methanogenesis span from ambient temperature to 90OC, a temperature range for most diagenetic reactions. In order to address how different precursors would be activated for microbially catalytic methane formation upon different temperatures, we incubated the sediments collected from Kuan-Tzu-Ling hot spring at temperatures up to 90OC. Five precursors including acetate, formate, methanol, methylamine, and hydrogen were added with the inocula to stimulate methanogenesis and inhibit fermentation, and were monitored together with methane production through time. Results of this experiments indicated that methanogenesis was positive at temperatures from room temperature to 80OC and precursors investigated despite substantial variations in the maximum rates and yields. In the experiment supplied with hydrogen and formate, methanogenic rates were rapid at all temperatures. Maximum methane production rates occurred at 40~50OC for incubations with methanol, 40~60OC for incubation with acetate, and 50OC for those with methylamine. The patterns of carbon isotopic compositions on methane were either consistent with the prediction of the Rayleigh fractionation in a closed system, trending toward more depleted through time or invariant through time, suggesting variable physiological responses and microbial assemblages to precursor additions. The obtained ɛ values were 0~-12‰ for incubations with acetate, -16~-45‰ for incubations with hydrogen, -50~-80‰ for incubations with methanol, and -87~-115‰ for incubations with methylamine. Acetoclastic methanogenesis appears to fractionate carbon isotopes at the smallest magnitude. This when combined with the results from positive controls and the field observation suggests that acetoclastic methanogenesis produced methane with isotopic signatures comparable with those with thermogenic in origin and contributed significantly to the total methane inventory in the Kuan-Tzu-Ling hotspring area.

Methyl-compound use and slow growth characterize microbial life in 2-km-deep subseafloor coal and shale beds.

PubMed

Trembath-Reichert, Elizabeth; Morono, Yuki; Ijiri, Akira; Hoshino, Tatsuhiko; Dawson, Katherine S; Inagaki, Fumio; Orphan, Victoria J

2017-10-31

The past decade of scientific ocean drilling has revealed seemingly ubiquitous, slow-growing microbial life within a range of deep biosphere habitats. Integrated Ocean Drilling Program Expedition 337 expanded these studies by successfully coring Miocene-aged coal beds 2 km below the seafloor hypothesized to be "hot spots" for microbial life. To characterize the activity of coal-associated microorganisms from this site, a series of stable isotope probing (SIP) experiments were conducted using intact pieces of coal and overlying shale incubated at in situ temperatures (45 °C). The 30-month SIP incubations were amended with deuterated water as a passive tracer for growth and different combinations of 13 C- or 15 N-labeled methanol, methylamine, and ammonium added at low (micromolar) concentrations to investigate methylotrophy in the deep subseafloor biosphere. Although the cell densities were low (50-2,000 cells per cubic centimeter), bulk geochemical measurements and single-cell-targeted nanometer-scale secondary ion mass spectrometry demonstrated active metabolism of methylated substrates by the thermally adapted microbial assemblage, with differing substrate utilization profiles between coal and shale incubations. The conversion of labeled methylamine and methanol was predominantly through heterotrophic processes, with only minor stimulation of methanogenesis. These findings were consistent with in situ and incubation 16S rRNA gene surveys. Microbial growth estimates in the incubations ranged from several months to over 100 y, representing some of the slowest direct measurements of environmental microbial biosynthesis rates. Collectively, these data highlight a small, but viable, deep coal bed biosphere characterized by extremely slow-growing heterotrophs that can utilize a diverse range of carbon and nitrogen substrates.

Acrolein generation stimulates hypercontraction in isolated human blood vessels

PubMed Central

Conklin, D.J.; Bhatnagar, A.; Cowley, H.R.; Johnson, G.H.; Wiechmann, R.J.; Sayre, L.M.; Trent, M.B.; Boor, P.J.

2012-01-01

Increased risk of vasospasm, a spontaneous hyperconstriction, is associated with atherosclerosis, cigarette smoking, and hypertension—all conditions involving oxidative stress, lipid peroxidation, and inflammation. To test the role of the lipid peroxidation- and inflammation-derived aldehyde, acrolein, in human vasospasm, we developed an ex vivo model using human coronary artery bypass graft (CABG) blood vessels and a demonstrated acrolein precursor, allylamine. Allylamine induces hypercontraction in isolated rat coronary artery in a semicarbazide-sensitive amine oxidase activity (SSAO) dependent manner. Isolated human CABG blood vessels (internal mammary artery, radial artery, saphenous vein) were used to determine: (1) vessel responses and sensitivity to acrolein, allylamine, and H2O2 exposure (1 μM–1 mM), (2) SSAO dependence of allylamine-induced effects using SSAO inhibitors (semicarbazide, 1 mM; MDL 72274-E, active isomer; MDL 72274-Z, inactive isomer; 100 μM), (3) the vasoactive effects of two other SSAO amine substrates, benzylamine and methylamine, and (4) the contribution of extracellular Ca2+ to hypercontraction. Acrolein or allylamine but not H2O2, benzylamine, or methylamine stimulated spontaneous and pharmacologically intractable hypercontraction in CABG blood vessels that was similar to clinical vasospasm. Allylamine-induced hypercontraction and blood vessel SSAO activity were abolished by pretreatment with semicarbazide or MDL 72274-E but not by MDL 72274-Z. Allylamine-induced hypercontraction also was significantly attenuated in Ca2+-free buffer. In isolated aorta of spontaneously hypertensive rat, allylamine-induced an SSAO-dependent contraction and enhanced norepinephrine sensitivity but not in Sprague–Dawley rat aorta. We conclude that acrolein generation in the blood vessel wall increases human susceptibility to vasospasm, an event that is enhanced in hypertension. PMID:17095030

Computational Study of Oxidation of Guanine by Singlet Oxygen (1 Δg ) and Formation of Guanine:Lysine Cross-Links.

PubMed

Thapa, Bishnu; Munk, Barbara H; Burrows, Cynthia J; Schlegel, H Bernhard

2017-04-27

Oxidation of guanine in the presence of lysine can lead to guanine-lysine cross-links. The ratio of the C4, C5 and C8 crosslinks depends on the manner of oxidation. Type II photosensitizers such as Rose Bengal and methylene blue can generate singlet oxygen, which leads to a different ratio of products than oxidation by type I photosensitizers or by one electron oxidants. Modeling reactions of singlet oxygen can be quite challenging. Reactions have been explored using CASSCF, NEVPT2, DFT, CCSD(T), and BD(T) calculations with SMD implicit solvation. The spin contamination in open-shell calculations were corrected by Yamaguchi's approximate spin projection method. The addition of singlet oxygen to guanine to form guanine endo- peroxide proceeds step-wise via a zwitterionic peroxyl intermediate. The subsequent barrier for ring closure is smaller than the initial barrier for singlet oxygen addition. Ring opening of the endoperoxide by protonation at C4-O is followed by loss of a proton from C8 and dehydration to produce 8-oxoG ox . The addition of lysine (modelled by methylamine) or water across the C5=N7 double bond of 8-oxoG ox is followed by acyl migration to form the final spiro products. The barrier for methylamine addition is significantly lower than for water addition and should be the dominant reaction channel. These results are in good agreement with the experimental results for the formation of guanine-lysine cross-links by oxidation by type II photosensitizers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of the free energy dependence of an interprotein electron transfer reaction by variation of pH and site-directed mutagenesis.

PubMed

Dow, Brian A; Davidson, Victor L

2015-10-01

The interprotein electron transfer (ET) reactions of the cupredoxin amicyanin, which mediates ET from the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase to cytochrome c-551i have been extensively studied. However, it was not possible to perform certain key experiments in that native system. This study examines the ET reaction from reduced amicyanin to an alternative electron acceptor, the diheme protein MauG. It was possible to vary the ΔG° for this ET reaction by simply changing pH to determine the dependence of kET on ΔG°. A P94A mutation of amicyanin significantly altered its oxidation-reduction midpoint potential value. It was not possible to study the ET from reduced P94A amicyanin to cytochrome c-551i in the native system because that reaction was kinetically coupled. However, the reaction from reduced P94A amicyanin to MauG was a true ET reaction and it was possible to determine values of reorganization energy (λ) and electronic coupling for the reactions of this variant as well as native amicyanin. Comparison of the λ values associated with the ET reactions between amicyanin and the TTQ of methylamine dehydrogenase, the diheme center of MauG and the single heme of cytochrome c-551i, provides insight into the factors that dictate the λ values for the respective reactions. These results demonstrate how study of ET reactions with alternative redox partner proteins can complement and enhance our understanding of the reactions with the natural redox partners, and further our understanding of mechanisms of protein ET reactions. Copyright © 2015 Elsevier B.V. All rights reserved.

Identification of the nitrogen-based blister agents bis(2-chloroethyl)methylamine (HN-2) and tris(2-chloroethyl)amine (HN-3) and their hydrolysis products on soil using ion trap secondary ion mass spectrometry.

PubMed

Gresham, G L; Groenewold, G S; Olson, J E

2000-12-01

The nitrogen blister agents HN-2 (bis(2-chloroethyl)methylamine) and HN-3 (tris(2-chloroethyl)amine) were directly analyzed on the surface of soil samples using ion trap secondary ion mass spectrometry (SIMS). In the presence of water, HN-1 (bis(2-choroethyl)ethylamine), HN-2 and HN-3 undergo hydrolysis to form N-ethyldiethanolamine, N-methyldiethanolamine and triethanolamine (TEA), respectively; these compounds can be readily detected as adsorbed species on soil particles. When soil samples spiked with HN-3 in alcohol were analyzed, 2-alkoxyethylamine derivatives were observed on the sample surfaces. This result shows that nitrogen blister agents will undergo condensation reactions with nucleophilic compounds and emphasizes the need for an analytical methodology capable of detecting a range of degradation and condensation products on environmental surfaces. The ability of ion trap SIMS to isolate and accumulate ions, and then perform tandem mass spectrometric analysis improves the detection of low-abundance surface contaminants and the selectivity of the technique. Utilizing these techniques, the limits of detection for HN-3 were studied as a function of surface coverage. It was found that HN-3 could be detected at a surface coverage of 0.01 monolayer, which corresponds to 20 ppm (mass/mass) for a soil having a surface area of 2.2 m(2) g(-1). TEA, the exhaustive hydrolysis product of HN-3, was detected at a surface coverage of 0.001 monolayer, which corresponds to 0.86 ppm. Copyright 2000 John Wiley & Sons, Ltd.

Polar-solvent-free colloidal synthesis of highly luminescent alkylammonium lead halide perovskite nanocrystals

NASA Astrophysics Data System (ADS)

Vybornyi, Oleh; Yakunin, Sergii; Kovalenko, Maksym V.

2016-03-01

A novel synthesis of hybrid organic-inorganic lead halide perovskite nanocrystals (CH3NH3PbX3, X = Br or I) that does not involve the use of dimethylformamide or other polar solvents is presented. The reaction between methylamine and PbX2 salts is conducted in a high-boiling nonpolar solvent (1-octadecene) in the presence of oleylamine and oleic acid as coordinating ligands. The resulting nanocrystals are characterized by high photoluminescence quantum efficiencies of 15-50%, outstanding phase purity and tunable shapes (nanocubes, nanowires, and nanoplatelets). Nanoplatelets spontaneously assemble into micrometer-length wires by face-to-face stacking. In addition, we demonstrate amplified spontaneous emission from thin films of green-emitting CH3NH3PbBr3 nanowires with low pumping thresholds of 3 μJ cm-2.A novel synthesis of hybrid organic-inorganic lead halide perovskite nanocrystals (CH3NH3PbX3, X = Br or I) that does not involve the use of dimethylformamide or other polar solvents is presented. The reaction between methylamine and PbX2 salts is conducted in a high-boiling nonpolar solvent (1-octadecene) in the presence of oleylamine and oleic acid as coordinating ligands. The resulting nanocrystals are characterized by high photoluminescence quantum efficiencies of 15-50%, outstanding phase purity and tunable shapes (nanocubes, nanowires, and nanoplatelets). Nanoplatelets spontaneously assemble into micrometer-length wires by face-to-face stacking. In addition, we demonstrate amplified spontaneous emission from thin films of green-emitting CH3NH3PbBr3 nanowires with low pumping thresholds of 3 μJ cm-2. Electronic supplementary information (ESI) available: Materials and methods, additional figures. See DOI: 10.1039/c5nr06890h

Methyl-compound use and slow growth characterize microbial life in 2-km-deep subseafloor coal and shale beds

PubMed Central

Trembath-Reichert, Elizabeth; Morono, Yuki; Ijiri, Akira; Hoshino, Tatsuhiko; Dawson, Katherine S.; Inagaki, Fumio

2017-01-01

The past decade of scientific ocean drilling has revealed seemingly ubiquitous, slow-growing microbial life within a range of deep biosphere habitats. Integrated Ocean Drilling Program Expedition 337 expanded these studies by successfully coring Miocene-aged coal beds 2 km below the seafloor hypothesized to be “hot spots” for microbial life. To characterize the activity of coal-associated microorganisms from this site, a series of stable isotope probing (SIP) experiments were conducted using intact pieces of coal and overlying shale incubated at in situ temperatures (45 °C). The 30-month SIP incubations were amended with deuterated water as a passive tracer for growth and different combinations of 13C- or 15N-labeled methanol, methylamine, and ammonium added at low (micromolar) concentrations to investigate methylotrophy in the deep subseafloor biosphere. Although the cell densities were low (50–2,000 cells per cubic centimeter), bulk geochemical measurements and single-cell–targeted nanometer-scale secondary ion mass spectrometry demonstrated active metabolism of methylated substrates by the thermally adapted microbial assemblage, with differing substrate utilization profiles between coal and shale incubations. The conversion of labeled methylamine and methanol was predominantly through heterotrophic processes, with only minor stimulation of methanogenesis. These findings were consistent with in situ and incubation 16S rRNA gene surveys. Microbial growth estimates in the incubations ranged from several months to over 100 y, representing some of the slowest direct measurements of environmental microbial biosynthesis rates. Collectively, these data highlight a small, but viable, deep coal bed biosphere characterized by extremely slow-growing heterotrophs that can utilize a diverse range of carbon and nitrogen substrates. PMID:29078310

Process for producing amorphous and crystalline silicon nitride

DOEpatents

Morgan, P.E.D.; Pugar, E.A.

1985-11-12

A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of whiskers'' or needles is heated at temperature ranging from about 900 C to about 1,200 C to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900 C. 6 figs.

Luminescent Li-based metal-organic framework tailored for the selective detection of explosive nitroaromatic compounds: direct observation of interaction sites.

PubMed

Kim, Tae Kyung; Lee, Jae Hwa; Moon, Dohyun; Moon, Hoi Ri

2013-01-18

A luminescent lithium metal-organic framework (MOF) is constructed from the solvothermal reaction of Li(+) and a well-designed organic ligand, bis(4-carboxyphenyl)-N-methylamine (H(2)CPMA). A Li-based MOF can detect an explosive aromatic compound containing nitro groups as an explosophore, by showing a dramatic color change with concurrent luminescence quenching in the solid state. The detection sites are proven directly through single-crystal-to-single-crystal transformations, which show strong interactions between the aromatic rings of the electron-rich CPMA(2-) molecules and the electron-deficient nitrobenzene.

Role of organic and inorganic cations on thermal behavior of lead iodide perovskites

NASA Astrophysics Data System (ADS)

Singh, Rajan Kumar; Dash, Saumya R.; Kumar, Ranveer; Jain, Neha; Singh, Jai

2018-04-01

Recently, organic-inorganic perovskite materials have attracted much attention due to their enormous potential for use in future of new sustainable energy sources. However, fabrication of environmental friendly perovskite and achieving better stability is a major concern towards the commercialization. Here we study the role of cations in the perovskite powder and their influence upon thermodynamic stability. In this study we find, inorganic (cesium, Cs+) cation is shown to be more efficient in the thermal stabilization of the perovskite material than organic (methylamine, CH3NH2+) cation. This study reviles that stability of perovskite can be improved by incorporation of inorganic cation.

Process for producing amorphous and crystalline silicon nitride

DOEpatents

Morgan, Peter E. D.; Pugar, Eloise A.

1985-01-01

A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

Effects of temperature on microbial succession and metabolite change during saeu-jeot fermentation.

PubMed

Lee, Se Hee; Jung, Ji Young; Jeon, Che Ok

2014-04-01

To investigate the effects of temperature on saeu-jeot (shrimp) fermentation, four sets of saeu-jeot samples with approximately 25% (w/v) NaCl were fermented at 10 °C, 15 °C, 20 °C, and 25 °C. The pH values of the 10 °C and 15 °C samples were relatively constant during the entire fermentation period, whereas those of the 20 °C and 25 °C samples gradually decreased after 25 days of fermentation. Quantitative PCR showed that the maximum bacterial abundance was greater in higher temperature samples, and the bacterial abundance in the 10 °C samples steadily decreased during the entire fermentation period. Community analysis using pyrosequencing revealed that the initially dominant Proteobacteria including Pseudoalteromonas, Photobacterium, Vibrio, Aliivibrio, and Enterovibrio were replaced rapidly with Firmicutes such as Psychrobacter, Staphylococcus, Salimicrobium, Alkalibacillus, and Halanaerobium as the fermentation progressed. However, Vibrio, Photobacterium, Aliivibrio, and Enterovibrio, which may include potentially pathogenic strains, remained even after 215 days in the 10 °C samples. Metabolite analysis using (1)H NMR showed that amino acid profiles and initial quick increases of glucose and glycerol were similar and independent of bacterial growth in all temperature samples. After 25 days of fermentation, the levels of glucose, glycerol, and trimethylamine N-oxide decreased with the growth of Halanaerobium and the increase of acetate, butyrate, and methylamines in the 20 °C and 25 °C samples although the amino acid concentrations steadily increased until approximately 105 days of fermentation. Statistical triplot analysis showed that the bacterial successions occurred similarly regardless of the fermentation temperature, and Halanaerobium was likely responsible for the production of acetate, butyrate, and methylamines. This study suggests that around 15 °C might be the optimum temperature for the production of safe and tasty saeu-jeot. Copyright © 2013 Elsevier Ltd. All rights reserved.

Reactive low temperature plasma ionization mass spectrometry for the determination of organic UV filters in personal care products.

PubMed

Ding, Xuelu; Gerbig, Stefanie; Spengler, Bernhard; Schulz, Sabine

2018-02-01

Organic UV filters in personal care products (PCPs) have been persistently reported as a potential threat to human health. In order to guarantee consumers ' safety, the dose of these compounds in PCPs needs to be monitored. Here, a methodology based on reactive low temperature plasma ionization (LTP) mass spectrometry (MS) has been developed for the determination of common organic UV filters in PCPs including benzophenone-3, ethylhexyl dimethyl p-aminobenzoic acid, ethylhexyl methoxycinnamate, 4-methylbenzylidene camphor, octocrylene, and ethylhexyl salicylate. The experiments were carried out in transmission geometry where the LTP ion source, samples loaded on a stainless steel mesh, and the MS inlet were aligned coaxially. Four chemicals, ammonia, ammonium formate, aniline, and methylamine were considered as reactive additives allowing reactions with the UV filters through different mechanisms. Methylamine-induced reactive LTP-MS showed the most prominent improvement on the detection of UV filter compounds. Compared to direct LTP-MS, the developed method improved the detection limits of UV filters more than 10 fold. Moreover, the method enabled fast semi-quantitative screening of UV filters in authentic PCPs. Concentrations of active ingredients in eight authentic PCPs as determined with reactive LTP-MS were found comparable to values offered by the cosmetic companies and corresponding HPLC data. The methodology provides high throughput analysis (70s per sample) and sensitive identification of organic UV filters. Lowest detectable concentrations ranged from 0.13µg/g for 4-methylbenzylidene camphor to 7.67µg/g for octocrylene in spiked cream. In addition, it shows the potential to be used as a screening tool for legal authentications of these chemicals in the future due to its semi-quantitative determination of UV filters in PCPs without tedious sample preparation and time-consuming chromatographic separation. Copyright © 2017 Elsevier B.V. All rights reserved.

Nucleophilic modification of human complement protein C3: correlation of conformational changes with acquisition of C3b-like functional properties.

PubMed

Isenman, D E; Kells, D I; Cooper, N R; Müller-Eberhard, H J; Pangburn, M K

1981-07-21

Inactivation of C3 by enzymatic cleavage, nucleophilic addition, or slow freezing and thawing resulted in the acquisition of similar end-state conformations as judged by near-UV circular dichroism. Although inactivation by the two nonenzymatic processes involves no peptide bond scission, the inactivated C3 resembled C3b in that it possessed a free sulfhydryl group not present in the native protein and an increased surface hydrophobicity as evidenced by enhanced binding of the fluorophore 8-anilino-1-naphthalensulfonate (ANS). The C3b-like functional properties of modified C3 [Pangburn, M. K., & Müller-Eberhard, H. J. (1980) J. Exp. Med. 152, 1102-1114] may thus be understood in terms of the similarity of its conformation to that of C3b. The rate of the conformational change following proteolytic cleavage was fast and appeared to be limited by the rate of the enzymatic reaction. In contrast, the rate of conformational change following addition of methylamine was slow and rate limited by the conformational rearrangement itself, not by the chemical modification. A kinetic analysis of the changes in circular dichroism and ANS fluorescence enhancement suggested that the nucleophilic addition was spectroscopically undetectable and was followed by a minimally biphasic, spectroscopically demonstrable conformational rearrangement. The appearance of C3b-like functional activity in nucleophile-modified C3 largely parallels the time course of the spectroscopically detectable conformational change but is distinctly slower than the rate at which hemolytic activity is lost. While fully transconformed methylamine-inactivated C3 can bind factor B and is susceptible to cleavage by C3b inactivator and its cofactor beta 1H, this cleavage occurs at a substantially slower rate than the equivalent process in C3b. The implications of these findings in terms of the mechanism through which the alterative pathway of complement is initiated are discussed.

Methylarcula marina gen. nov., sp. nov. and Methylarcula terricola sp. nov.: novel aerobic, moderately halophilic, facultatively methylotrophic bacteria from coastal saline environments.

PubMed

Doronina, N V; Trotsenko, Y A; Tourova, T P

2000-09-01

A new genus, Methylarcula, with two new species, Methylarcula marina and Methylarcula terricola, are proposed for strains h1T and h37T of moderately halophilic facultatively methylotrophic bacteria isolated from the coastal saline habitats. These methylobacteria are aerobic, Gram-negative, asporogenous, non-motile, colourless rods that multiply by binary fission. Their cellular fatty acids profiles consist primarily of straight-chain unsaturated (C18:1; 70-80%), saturated (C18:0; 14-16%) and cyclopropane (C19:0; 5-6%) acids. The major ubiquinone is Q-10. The dominant phospholipids are phosphatidylethanolamine and phosphatidylcholine. Both strains could use methylamine, some sugars and organic acids as carbon and energy sources. They grew well under optimal conditions (29-35 degrees C, pH 7.5-8.5, 0.5-1.0 M NaCl) and accumulated intracellularly poly-beta-hydroxybutyrate and the compatible solute ectoine. The ectoine pool was found to increase upon increasing the external NaCl concentration and accounted for 18% of the dry cellular weight. Both strains oxidized methylamine by the N-methylglutamate (N-MG) pathway enzymes (gamma-glutamylmethylamide synthetase/lyase and N-MG synthetase/lyase) to formaldehyde and assimilated it via the icl- serine pathway. The DNA G+C content was 60-4 mol% for Methylarcula marina h1T and 57.1 mol% for Methylarcula terricola h37T. The DNA-DNA hybridization value between strains hl and h37 was 25-30%, although they had a low level of DNA relatedness (5-7%) with the type strains of the serine pathway methylobacteria belonging to the genera Methylobacterium, Aminobacter, Methylorhabdus and Methylopila. A comparative 16S rDNA sequence-based phylogenetic analysis placed the two species of Methylarcula into a separate branch of the alpha-3 subclass of the Proteobacteria. The type strains of the new species are Methylarcula marina h1T (= VKM B-2159T) and Methylarcula terricola h37T (= VKM B-2160T).

Methylobacterium genome sequences: a reference blueprint to investigate microbial metabolism of C1 compounds from natural and industrial sources.

PubMed

Vuilleumier, Stéphane; Chistoserdova, Ludmila; Lee, Ming-Chun; Bringel, Françoise; Lajus, Aurélie; Zhou, Yang; Gourion, Benjamin; Barbe, Valérie; Chang, Jean; Cruveiller, Stéphane; Dossat, Carole; Gillett, Will; Gruffaz, Christelle; Haugen, Eric; Hourcade, Edith; Levy, Ruth; Mangenot, Sophie; Muller, Emilie; Nadalig, Thierry; Pagni, Marco; Penny, Christian; Peyraud, Rémi; Robinson, David G; Roche, David; Rouy, Zoé; Saenampechek, Channakhone; Salvignol, Grégory; Vallenet, David; Wu, Zaining; Marx, Christopher J; Vorholt, Julia A; Olson, Maynard V; Kaul, Rajinder; Weissenbach, Jean; Médigue, Claudine; Lidstrom, Mary E

2009-01-01

Methylotrophy describes the ability of organisms to grow on reduced organic compounds without carbon-carbon bonds. The genomes of two pink-pigmented facultative methylotrophic bacteria of the Alpha-proteobacterial genus Methylobacterium, the reference species Methylobacterium extorquens strain AM1 and the dichloromethane-degrading strain DM4, were compared. The 6.88 Mb genome of strain AM1 comprises a 5.51 Mb chromosome, a 1.26 Mb megaplasmid and three plasmids, while the 6.12 Mb genome of strain DM4 features a 5.94 Mb chromosome and two plasmids. The chromosomes are highly syntenic and share a large majority of genes, while plasmids are mostly strain-specific, with the exception of a 130 kb region of the strain AM1 megaplasmid which is syntenic to a chromosomal region of strain DM4. Both genomes contain large sets of insertion elements, many of them strain-specific, suggesting an important potential for genomic plasticity. Most of the genomic determinants associated with methylotrophy are nearly identical, with two exceptions that illustrate the metabolic and genomic versatility of Methylobacterium. A 126 kb dichloromethane utilization (dcm) gene cluster is essential for the ability of strain DM4 to use DCM as the sole carbon and energy source for growth and is unique to strain DM4. The methylamine utilization (mau) gene cluster is only found in strain AM1, indicating that strain DM4 employs an alternative system for growth with methylamine. The dcm and mau clusters represent two of the chromosomal genomic islands (AM1: 28; DM4: 17) that were defined. The mau cluster is flanked by mobile elements, but the dcm cluster disrupts a gene annotated as chelatase and for which we propose the name "island integration determinant" (iid). These two genome sequences provide a platform for intra- and interspecies genomic comparisons in the genus Methylobacterium, and for investigations of the adaptive mechanisms which allow bacterial lineages to acquire methylotrophic lifestyles.

Intercalation chemistry of zirconium 4-sulfophenylphosphonate

NASA Astrophysics Data System (ADS)

Svoboda, Jan; Zima, Vítězslav; Melánová, Klára; Beneš, Ludvík; Trchová, Miroslava

2013-12-01

Zirconium 4-sulfophenylphosphonate is a layered material which can be employed as a host for the intercalation reactions with basic molecules. A wide range of organic compounds were chosen to represent intercalation ability of zirconium 4-sulfophenylphosphonate. These were a series of alkylamines from methylamine to dodecylamine, 1,4-phenylenediamine, p-toluidine, 1,8-diaminonaphthalene, 1-aminopyrene, imidazole, pyridine, 4,4‧-bipyridine, poly(ethylene imine), and a series of amino acids from glycine to 6-aminocaproic acid. The prepared compounds were characterized by powder X-ray diffraction, thermogravimetry analysis and IR spectroscopy and probable arrangement of the guest molecules in the interlayer space of the host is proposed based on the interlayer distance of the prepared intercalates and amount of the intercalated guest molecules.

Synthesis and pharmacological characterization of novel inverse agonists acting on the viral-encoded chemokine receptor US28.

PubMed

Hulshof, Janneke W; Vischer, Henry F; Verheij, Mark H P; Fratantoni, Silvina A; Smit, Martine J; de Esch, Iwan J P; Leurs, Rob

2006-11-01

G-protein coupled receptors encoded by viruses represent an unexplored class of potential drug targets. In this study, we describe the synthesis and pharmacological characterization of the first class of inverse agonists acting on the HCMV-encoded receptor US28. It is shown that replacement of the 4-hydroxy group of lead compound 1 with a methylamine group results in a significant 6-fold increase in affinity. Interestingly, increasing the rigidity of the spacer by the introduction of a double bond also leads to a significant increase in binding affinity compared to 1. These novel inverse agonists serve as valuable tools to elucidate the role of constitutive signaling in the pathogenesis of viral infection and may have therapeutic potential as leads for new antiviral drugs.

Functional expression of amine oxidase from Aspergillus niger (AO-I) in Saccharomyces cerevisiae.

PubMed

Kolaríková, Katerina; Galuszka, Petr; Sedlárová, Iva; Sebela, Marek; Frébort, Ivo

2009-01-01

The aim of this work was to prepare recombinant amine oxidase from Aspergillus niger after overexpressing in yeast. The yeast expression vector pDR197 that includes a constitutive PMA1 promoter was used for the expression in Saccharomyces cerevisiae. Recombinant amine oxidase was extracted from the growth medium of the yeast, purified to homogeneity and identified by activity assay and MALDI-TOF peptide mass fingerprinting. Similarity search in the newly published A. niger genome identified six genes coding for copper amine oxidase, two of them corresponding to the previously described enzymes AO-I a methylamine oxidase and three other genes coding for FAD amine oxidases. Thus, A. niger possesses an enormous metabolic gear to grow on amine compounds and thus support its saprophytic lifestyle.

Methane production from coal by a single methanogen

NASA Astrophysics Data System (ADS)

Sakata, S.; Mayumi, D.; Mochimaru, H.; Tamaki, H.; Yamamoto, K.; Yoshioka, H.; Suzuki, Y.; Kamagata, Y.

2017-12-01

Previous geochemical studies indicate that biogenic methane greatly contributes to the formation of coalbed methane (CBM). It is unclear, however, what part of coal is used for the methane production and what types of microbes mediate the process. Here we hypothesized that methylotrophic methanogens use methoxylated aromatic compounds (MACs) derived from lignin. We incubated 11 species of methanogens belonging to order Methanosarcinales with 7 types of MACs. Two strains of methanogens, i.e., Methermicoccus shengliensis AmaM and ZC-1, produced methane from the MACs. In fact, these methanogens used over 30 types of commercially available MACs in addition to methanol and methylamines. To date, it is widely believed that methanogens use very limited number of small compounds such as hydrogen plus carbon dioxide, acetate, and methanol, and only three methanogenic pathways are recognized accordingly. Here, in contrast, two Methermicoccus strains used many types of MACs. We therefore propose this "methoxydotrophic" process as the fourth methanogenic pathway. Incubation of AmaM with 2-methoxybenzoate resulted in methanogenesis associated with the stoichiometric production of 2-hydroxybenzoate. Incubation with 2-methoxy-[7-13C] benzoate and with [13C] bicarbonate indicated that two thirds of methane carbon derived from the methoxy group and one third from CO2. Furthermore, incubation with [2-13C] acetate resulted in significant increases of 13C in both methane and CO2. These results suggest the occurrence of O-demethylation, CO2 reduction and acetyl-CoA metabolism in the methoxydotrophic methanogenesis. Furthermore, incubation of AmaM with lignite, subbituminous or bituminous coals in the bicarbonate-buffered media revealed that AmaM produced methane directly from coals via the methoxydotrophic pathway. Although 4 types of MACs were detected in the coal media in addition to methanol and methylamines, their total concentrations were too low to account for the methane production, suggesting that AmaM produced methane from MACs in the media not analyzed this time and/or MACs bound to the coal surface. In conclusion, the contribution of methoxydotrophic methanogenesis may be important not only to the formation of CBM but also to the global carbon cycle.

Methylobacterium Genome Sequences: A Reference Blueprint to Investigate Microbial Metabolism of C1 Compounds from Natural and Industrial Sources

PubMed Central

Lee, Ming-Chun; Bringel, Françoise; Lajus, Aurélie; Zhou, Yang; Gourion, Benjamin; Barbe, Valérie; Chang, Jean; Cruveiller, Stéphane; Dossat, Carole; Gillett, Will; Gruffaz, Christelle; Haugen, Eric; Hourcade, Edith; Levy, Ruth; Mangenot, Sophie; Muller, Emilie; Nadalig, Thierry; Pagni, Marco; Penny, Christian; Peyraud, Rémi; Robinson, David G.; Roche, David; Rouy, Zoé; Saenampechek, Channakhone; Salvignol, Grégory; Vallenet, David; Wu, Zaining; Marx, Christopher J.; Vorholt, Julia A.; Olson, Maynard V.; Kaul, Rajinder; Weissenbach, Jean; Médigue, Claudine; Lidstrom, Mary E.

2009-01-01

Background Methylotrophy describes the ability of organisms to grow on reduced organic compounds without carbon-carbon bonds. The genomes of two pink-pigmented facultative methylotrophic bacteria of the Alpha-proteobacterial genus Methylobacterium, the reference species Methylobacterium extorquens strain AM1 and the dichloromethane-degrading strain DM4, were compared. Methodology/Principal Findings The 6.88 Mb genome of strain AM1 comprises a 5.51 Mb chromosome, a 1.26 Mb megaplasmid and three plasmids, while the 6.12 Mb genome of strain DM4 features a 5.94 Mb chromosome and two plasmids. The chromosomes are highly syntenic and share a large majority of genes, while plasmids are mostly strain-specific, with the exception of a 130 kb region of the strain AM1 megaplasmid which is syntenic to a chromosomal region of strain DM4. Both genomes contain large sets of insertion elements, many of them strain-specific, suggesting an important potential for genomic plasticity. Most of the genomic determinants associated with methylotrophy are nearly identical, with two exceptions that illustrate the metabolic and genomic versatility of Methylobacterium. A 126 kb dichloromethane utilization (dcm) gene cluster is essential for the ability of strain DM4 to use DCM as the sole carbon and energy source for growth and is unique to strain DM4. The methylamine utilization (mau) gene cluster is only found in strain AM1, indicating that strain DM4 employs an alternative system for growth with methylamine. The dcm and mau clusters represent two of the chromosomal genomic islands (AM1: 28; DM4: 17) that were defined. The mau cluster is flanked by mobile elements, but the dcm cluster disrupts a gene annotated as chelatase and for which we propose the name “island integration determinant” (iid). Conclusion/Significance These two genome sequences provide a platform for intra- and interspecies genomic comparisons in the genus Methylobacterium, and for investigations of the adaptive mechanisms which allow bacterial lineages to acquire methylotrophic lifestyles. PMID:19440302

Methanolobus taylorii sp nov, a new methylotropic, estuarine methanogen

USGS Publications Warehouse

Oremland, Ronald S.; Boone, David R.

1994-01-01

Strain GS-16T (T = type strain) is a methylotrophic methanogen that was isolated from estuarine sediments from San Francisco Bay (4) and has been deposited in the Oregon Collection of Methanogens (Oregon Graduate Institute, Portland) as strain OCM 5ST. This strain was isolated by using dimethyl sulfide as the catabolic substrate (4), but it can also grow on methylamines (13) and methanethiol (8, 9) and grew when it was inoculated into MSHA medium (6) supplemented with 20 mM methanol as the sole catabolic substrate. Strain GS-16T cells form methane from methylmercury (12) and dimethylselenide (16), although they cannot grow on these substrates, and form traces of ethane from diethyl sulfide (15). Methanogenesis from trimethylamine is inhibited by methyl fluoride (11) and methyl bromide (14), but not by dimethyl ether (1 1).

Heterogeneous chemistry of alkylamines with sulfuric acid: implications for atmospheric formation of alkylaminium sulfates.

PubMed

Wang, Lin; Lal, Vinita; Khalizov, Alexei F; Zhang, Renyi

2010-04-01

The heterogeneous interaction of alkylamines with sulfuric acid has been investigated to assess the role of amines in aerosol growth through the formation of alkylaminium sulfates. The kinetic experiments were conducted in a low-pressure fast flow reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS). The measurements of heterogeneous uptake of methylamine, dimethylamine, and trimethylamine were performed in the acidity range of 59-82 wt % H(2)SO(4) and between 243 and 283 K. Irreversible reactive uptakes were observed for all three alkylamines, with comparable uptake coefficients (gamma) in the range of 2.0 x 10(-2) to 4.4 x 10(-2). The measured gamma value was slightly higher in more concentrated sulfuric acid and at lower temperatures. The results imply that the heterogeneous reactions of alkylamines contribute effectively to the growth of atmospheric acidic particles and, hence, secondary organic aerosol formation.

Alkylation of Staurosporine to Derive a Kinase Probe for Fluorescence Applications.

PubMed

Disney, Alexander J M; Kellam, Barrie; Dekker, Lodewijk V

2016-05-06

The natural product staurosporine is a high-affinity inhibitor of nearly all mammalian protein kinases. The labelling of staurosporine has proven effective as a means of generating protein kinase research tools. Most tools have been generated by acylation of the 4'-methylamine of the sugar moiety of staurosporine. Herein we describe the alkylation of this group as a first step to generate a fluorescently labelled staurosporine. Following alkylation, a polyethylene glycol linker was installed, allowing subsequent attachment of fluorescein. We report that this fluorescein-staurosporine conjugate binds to cAMP-dependent protein kinase in the nanomolar range. Furthermore, its binding can be antagonised with unmodified staurosporine as well as ATP, indicating it targets the ATP binding site in a similar fashion to native staurosporine. This reagent has potential application as a screening tool for protein kinases of interest. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Quantitative determination of the hydrolysis products of nitrogen mustards in human urine by liquid chromatography-electrospray ionization tandem mass spectrometry.

PubMed

Lemire, Sharon W; Ashley, David L; Calafat, Antonia M

2003-01-01

Nitrogen mustards are a public health concern because of their extreme vesicant properties and the possible exposure of workers during the destruction of chemical stockpiles. A sensitive, rapid, accurate, and precise analysis for the quantitation of ultratrace levels of N-ethyldiethanolamine (EDEA) and N-methyldiethanolamine (MDEA) in human urine as a means of assessing recent exposure to the nitrogen mustards bis(2-chloroethyl)ethylamine and bis(2-chloroethyl)methylamine, respectively, was developed. The method was based on solid-phase extraction, followed by analysis of the urine extract using isotope-dilution high-performance liquid chromatography-mass spectrometry with TurbolonSpray ionization and multiple-reaction monitoring. The method limits of detection were 0.41 ng/mL for EDEA and 0.96 ng/mL for MDEA in 1 mL of urine with coefficients of variation < 10% for both compounds.

A Highly Selective and Robust Co(II)-Based Homogeneous Catalyst for Reduction of CO2 to CO in CH3CN/H2O Solution Driven by Visible Light.

PubMed

Ouyang, Ting; Hou, Cheng; Wang, Jia-Wei; Liu, Wen-Ju; Zhong, Di-Chang; Ke, Zhuo-Feng; Lu, Tong-Bu

2017-07-03

Visible-light driven reduction of CO 2 into chemical fuels has attracted enormous interest in the production of sustainable energy and reversal of the global warming trend. The main challenge in this field is the development of efficient, selective, and economic photocatalysts. Herein, we report a Co(II)-based homogeneous catalyst, [Co(NTB)CH 3 CN](ClO 4 ) 2 (1, NTB = tris(benzimidazolyl-2-methyl)amine), which shows high selectivity and stability for the catalytic reduction of CO 2 to CO in a water-containing system driven by visible light, with turnover number (TON) and turnover frequency (TOF) values of 1179 and 0.032 s -1 , respectively, and selectivity to CO of 97%. The high catalytic activity of 1 for photochemical CO 2 -to-CO conversion is supported by the results of electrochemical investigations and DFT calculations.

Formation of nitrogen-containing oligomers by methylglyoxal and amines in simulated evaporating cloud droplets.

PubMed

De Haan, David O; Hawkins, Lelia N; Kononenko, Julia A; Turley, Jacob J; Corrigan, Ashley L; Tolbert, Margaret A; Jimenez, Jose L

2011-02-01

Reactions of methylglyoxal with amino acids, methylamine, and ammonium sulfate can take place in aqueous aerosol and evaporating cloud droplets. These processes are simulated by drying droplets and bulk solutions of these compounds (at low millimolar and 1 M concentrations, respectively) and analyzing the residuals by scanning mobility particle sizing, nuclear magnetic resonance, aerosol mass spectrometry (AMS), and electrospray ionization MS. The results are consistent with imine (but not diimine) formation on a time scale of seconds, followed by the formation of nitrogen-containing oligomers, methylimidazole, and dimethylimidazole products on a time scale of minutes to hours. Measured elemental ratios are consistent with imidazoles and oligomers being major reaction products, while effective aerosol densities suggest extensive reactions take place within minutes. These reactions may be a source of the light-absorbing, nitrogen-containing oligomers observed in urban and biomass-burning aerosol particles.

[Analysis of DNA-DNA homologies in obligate methylotrophic bacteria].

PubMed

Doronina, N V; Govorukhina, N I; Lysenko, A M; Trotsenko, Iu A

1988-01-01

The genotypic affinity of 19 bacterial strains obligately dependent on methanol or methylamine as carbon and energy sources was studied by techniques of molecular DNA hybridization. The high homology level (35-88%) between motile strain Methylophilus methanolovorus V-1447D and nonmotile strain Methylobacillus sp. VSB-792 as well as other motile strains (Pseudomonas methanolica ATCC 21704, Methylomonas methanolica NRRL 5458, Pseudomonas sp. W6, strain A3) indicates that all of them belong to one genus. Rather high level of homology (62-63%) was found between Methylobacillus glycogenes ATCC 29475 and Pseudomonas insueta ATCC 21276 and strain G-10. The motile strain Methylophilus methylotrophus NCIB 10515 has a low homology (below 20%) to other of the studied obligate methylobacteria. Therefore, at least two genetically different genera of obligate methylobacteria can be distinguished, namely Methylophilus and Methylobacillus, the latter being represented by both motile and nonmotile forms.

Hydrothermal carbon nanosphere-based agglomerated anion exchanger for ion chromatography.

PubMed

Zhao, Qiming; Wu, Shuchao; Zhang, Kai; Lou, Chaoyan; Zhang, Peiming; Zhu, Yan

2016-10-14

This work reports the application of hydrothermal carbon nanospheres (HCNSs) as stationary phases in ion chromatography. HCNSs were facilely quaternized through polycondensation of methylamine and 1,4-butanediol diglycidyl ether. The quaternization was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Owing to the electrostatic interaction, quaternized HCNSs were equably attached onto the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) beads to construct the anion exchangers. The aggregation was verified by scanning electron microscopy and elemental analysis. Common anions, aliphatic monocarboxylic acids, polarizable anions, and aromatic acids were well separated on the stationary phases with good stability and symmetry. The prepared column was further applied to detect phosphate content in Cola drink samples. The limit of detection (S/N=3) was 0.09mg/L, and the relative standard deviation (n=10) of retention time was 0.31%. The average recovery was 99.58%. Copyright © 2016 Elsevier B.V. All rights reserved.

Possibility of the Nonenzymatic Browning (Maillard) Reaction in the ISM

NASA Astrophysics Data System (ADS)

Jalbout, Abraham F.; Shipar, M. Abul Haider

2008-04-01

The possibility of the occurrence of the nonenzymatic browning reaction in the gaseous phase in the interstellar medium has been investigated by using Density Functional Theory computations. Mechanisms for the reactions between formaldehyde ( Fald) + glycine ( Gly), Fald + NH 3 and Fald + methylamine ( MeAm) have been proposed, and the possibility of the formation of different compounds in the proposed mechanisms has been evaluated through calculating the Gibb's free energy changes for different steps of the reaction, by following the total mass balance. The Fald + Gly reaction under basic conditions is found as the most favorable for producing 1-methyl-amino methene or 1-methyl-amino methelene ( MAM). The reaction under acidic conditions is found to be the least favorable for producing MAM. The Fald + NH 3 reaction is found to be plausible for the production of MeAm, which can participate by reaction with Fald, resulting in the formation of MAM.

Terpenoid-Alkaloids: Their Biosynthetic Twist of Fate and Total Synthesis.

PubMed

Cherney, Emily C; Baran, Phil S

2011-04-01

Terpenes and alkaloids are ever-growing classes of natural products that provide new molecular structures which inspire chemists and possess a broad range of biological activity. Terpenoid-alkaloids originate from the same prenyl units that construct terpene skeletons. However, during biosynthesis, a nitrogen atom (or atoms) is introduced in the form of β-aminoethanol, ethylamine, or methylamine. Nitrogen incorporation can occur either before, during, or after the cyclase phase. The outcome of this unique biosynthesis is the formation of natural products containing unprecedented structures. These complex structural motifs expose current limitations in organic chemistry, thus providing opportunities for invention. This review focuses on total syntheses of terpenoid-alkaloids and unique issues presented by this class of natural products. More specifically, it examines how these syntheses relate to the way terpenoid-alkaloids are made in Nature. Developments in chemistry that have facilitated these syntheses are emphasized, as well as chemical technology needed to conquer those that evade synthesis.

Atypical archaeal tRNA pyrrolysine transcript behaves towards EF-Tu as a typical elongator tRNA

PubMed Central

Théobald-Dietrich, Anne; Frugier, Magali; Giegé, Richard; Rudinger-Thirion, Joëlle

2004-01-01

The newly discovered tRNAPyl is involved in specific incorporation of pyrrolysine in the active site of methylamine methyltransferases in the archaeon Methanosarcina barkeri. In solution probing experiments, a transcript derived from tRNAPyl displays a secondary fold slightly different from the canonical cloverleaf and interestingly similar to that of bovine mitochondrial tRNASer(uga). Aminoacylation of tRNAPyl transcript by a typical class II synthetase, LysRS from yeast, was possible when its amber anticodon CUA was mutated into a lysine UUU anticodon. Hydrolysis protection assays show that lysylated tRNAPyl can be recognized by bacterial elongation factor. This indicates that no antideterminant sequence is present in the body of the tRNAPyl transcript to prevent it from interacting with EF-Tu, in contrast with the otherwise functionally similar tRNASec that mediates selenocysteine incorporation. PMID:14872064

Vibrational spectra and fragmentation pathways of size-selected, D2-tagged ammonium/methylammonium bisulfate clusters.

PubMed

Johnson, Christopher J; Johnson, Mark A

2013-12-19

Particles consisting of ammonia and sulfuric acid are widely regarded as seeds for atmospheric aerosol nucleation, and incorporation of alkylamines has been suggested to substantially accelerate their growth. Despite significant efforts, little direct experimental evidence exists for the structures and chemical processes underlying multicomponent particle nucleation. Here we are concerned with the positively charged clusters of ammonia and sulfuric acid with compositions H(+)(NH3)m(H2SO4)n (2 ≤ m ≤ 5, 1 ≤ n ≤ 4), for which equilibrium geometry structures have been reported in recent computational searches. The computed harmonic vibrational spectra of such minimum energy structures can be directly compared with the experimental spectra of each cluster composition isolated in the laboratory using cryogenic ion chemistry methods. We present one-photon (i.e., linear) infrared action spectra of the isolated gas phase ions cryogenically cooled to 10 K, allowing us to resolve the characteristic vibrational signatures of these clusters. Because the available calculated spectra for different structural candidates have been obtained using different levels of theory, we reoptimized the previously reported structures with several common electronic structure methods and find excellent agreement can be achieved for the (m = 3, n = 2) cluster using CAM-B3LYP with only minor structural differences from the previously identified geometries. At the larger sizes, the experimental spectra strongly resemble that observed for 180 nm ammonium bisulfate particles. The characteristic ammonium- and bisulfate-localized bands are clearly evident at all sizes studied, indicating that the cluster structures are indeed ionic in nature. With the likely (3,2) structure in hand, we then explore the spectral and structural changes caused when methylamine is substituted for ammonia. This process is found to occur with minimal perturbation of the unsubstituted cluster. The thermal decomposition pathways were also evaluated using multiple-photon induced dissociation and are, in all cases, dominated (>100:1) by evaporation of a neutral ammonia molecule rather than methylamine. Spectra obtained for the product cluster ions resulting from this evaporation are consistent with the formation of a single hydrogen bond between two neighboring bisulfate ions, partially regenerating a sulfuric acid molecule. These results provide critical experimental benchmarks for ongoing theoretical efforts to understand the early stages of aerosol growth.

Charge Transport between Coupling Colloidal Perovskite Quantum Dots Assisted by Functional Conjugated Ligands.

PubMed

Dai, Jinfei; Xi, Jun; Li, Lu; Zhao, JingFeng; Shi, Yifei; Zhang, Wenwen; Ran, Chenxin; Jiao, Bo; Hou, Xun; Duan, Xinhua; Wu, Zhaoxin

2018-05-14

Long alkyl-chain capping ligands are indispensable for preparing stable colloidal quantum dots. However, its insulating feature blocks efficient carrier transport among QDs, leading to inferior performance in light-emitting diodes (LEDs). The trade-off between conductivity and colloidal stability of QDs has now been overcome. Methylamine lead bromide (MAPbBr 3 ) QDs with a conjugated alkyl-amine, 3-phenyl-2-propen-1-amine (PPA), as ligands were prepared. Owing to electron cloud overlapping and the delocalization effect of conjugated molecules, the conductivity and carrier mobility of PPA-QDs films increased almost 22 times over that of OA-QD films without compromising colloidal stability and photoluminescence. PPA-QDs LEDs exhibit a maximum current efficiency of 9.08 cd A -1 , which is 8 times of that of OA-QDs LEDs (1.14 cd A -1 ). This work provides critical solution for the poor conductivity of QDs in applications of energy-related devices. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The chemical biology of methanogenesis

NASA Astrophysics Data System (ADS)

Ferry, James G.

2010-12-01

Two distinct pathways account for most of the CH 4 produced in the majority of the diverse and vast anaerobic environments of Earth's biosphere by microbes that are classified in the Archaea domain of life: conversion of the methyl group of acetate to CH 4 in the aceticlastic pathway and reduction of CO 2 with electrons derived from H 2, formate or CO in the CO 2 reduction pathway. Minor, albeit ecologically important, amounts of CH 4 are produced by conversion of methylotrophic substrates methanol, methylamines and methyl sulfides. Although all pathways have terminal steps in common, they deviate in the initial steps leading to CH 4 and mechanisms for synthesizing ATP for growth. Hydrogen gas is the major reductant for CO 2-reducing methanogens in the deep subsurface, although H 2 is also utilized by CO 2-reducing microbes from the Bacteria domain that produce acetate for the aceticlastic methanogens. This review presents fundamentals of the two major CH 4-producing pathways with a focus on understanding the potential for biologically-produced CH 4 on Mars.

Secondary organic aerosol formation from primary aliphatic amines with NO3 radical

NASA Astrophysics Data System (ADS)

Malloy, Q. G. J.; Qi, Li; Warren, B.; Cocker, D. R., III; Erupe, M. E.; Silva, P. J.

2009-03-01

Primary aliphatic amines are an important class of nitrogen containing compounds emitted from automobiles, waste treatment facilities and agricultural animal operations. A series of experiments conducted at the UC-Riverside/CE-CERT Environmental Chamber is presented in which oxidation of methylamine, ethylamine, propylamine, and butylamine with O3 and NO3 have been investigated. Very little aerosol formation is observed in the presence of O3 only. However, after addition of NO, and by extension NO3, large aerosol mass yields (~44% for butylamine) are seen. Aerosol generated was determined to be organic in nature due to the small fraction of NO and NO2 in the total signal (<1% for all amines tested) as detected by an aerosol mass spectrometer (AMS). We propose a reaction mechanism between carbonyl containing species and the parent amine leading to formation of particulate imine products. These findings can have significant impacts on rural communities with elevated nighttime PM loadings, when significant levels of NO3 exist.

Secondary organic aerosol formation from primary aliphatic amines with NO3 radical

NASA Astrophysics Data System (ADS)

Malloy, Q. G. J.; Qi, Li; Warren, B.; Cocker, D. R., III; Erupe, M. E.; Silva, P. J.

2008-07-01

Primary aliphatic amines are an important class of nitrogen containing compounds found to be emitted from automobiles, waste treatment facilities and agricultural animal operations. A series of experiments conducted at the UC-Riverside/CE-CERT Environmental Chamber is presented in which oxidation of methylamine, ethylamine, propylamine, and butylamine with NO3 has been investigated. Very little aerosol formation is observed in the presence of O3 only. However, after addition of NO, and by extension NO3, large yields of aerosol mass loadings (~44% for butylamine) are seen. Aerosol generated was determined to be organic in nature due to the small fraction of NO and NO2 in the total signal (<17% for all amines tested) as detected by an aerosol mass spectrometer (AMS). We propose a reaction mechanism between carbonyl containing species and the parent amine leading to formation of particulate imine products. These findings can have significant impacts on rural communities and lead to elevated nighttime PM loadings, when significant levels on NO3 exist.

Betaine protects urea-induced denaturation of myosin subfragment-1.

PubMed

Ortiz-Costa, Susana; Sorenson, Martha M; Sola-Penna, Mauro

2008-07-01

We have demonstrated previously that urea inhibits the activity and alters the tertiary structure of skeletal muscle myosin in a biphasic manner. This was attributed to differential effects on its globular and filamentous portion. The inhibition of catalytic activity was counteracted by methylamines. With the aim of comprehending the effects of urea on the catalytic (globular) portion of myosin, this study examines the effects of urea and the countereffects of betaine on the catalytic activity and structure of myosin subfragment-1. It is shown that urea inactivates subfragment-1 in parallel with its ability to induce exposure of the enzyme hydrophobic domains, as assessed using intrinsic and extrinsic fluorescence. Both effects are counteracted by betaine, which alone does not significantly affect subfragment-1. Urea also enhances the accessibility of thiol groups, promotes aggregation and decreases the alpha-helix content of S1, effects that are also counteracted by betaine. We conclude that urea-induced inactivation of the enzyme is caused by partial unfolding of the myosin catalytic domain.

Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales.

PubMed

Daly, Rebecca A; Borton, Mikayla A; Wilkins, Michael J; Hoyt, David W; Kountz, Duncan J; Wolfe, Richard A; Welch, Susan A; Marcus, Daniel N; Trexler, Ryan V; MacRae, Jean D; Krzycki, Joseph A; Cole, David R; Mouser, Paula J; Wrighton, Kelly C

2016-09-05

Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here, the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that many of the persisting organisms play roles in methylamine cycling, ultimately supporting methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while thiosulfate reduction could produce sulfide, contributing to reservoir souring and infrastructure corrosion. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.

Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daly, Rebecca A.; Borton, Mikayla A.; Wilkins, Michael J.

Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that methylamine cycling supports methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while sulfide generation from thiosulfate represents a poorly recognized corrosion mechanism inmore » shales. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.« less

Uptake of Alkylamines on Dicarboxylic Acids Relevant to Secondary Organic Aerosol Formation

NASA Astrophysics Data System (ADS)

Marrero-Ortiz, W.; Secrest, J.; Zhang, R.

2017-12-01

Aerosols play a critical role in climate directly by scattering and absorbing solar radiation, and indirectly by functioning as cloud condensation nuclei (CCN); both represent the largest uncertainties in climate predictions. New particle formation contributes significantly to CCN production; however, the mechanisms related to particle nucleation and growth processes are not well understood. Organic acids are atmospherically abundant, and their neutralization by low molecular weight amines may result in the formation of stable low volatility aminium salt products contributing to the growth of secondary organic aerosols and even the alteration of the aerosol properties. The acid-base neutralization of particle phase succinic acid and tartaric acid by low molecular weight aliphatic amines, i.e. methylamine, dimethylamine, and trimethylamine, has been investigated by employing a low-pressure fast flow reactor at 298K with an ion drift - chemical ionization mass spectrometer (ID-CIMS). The heterogeneous uptake is time dependent and influenced by organic acids functionality, alkylamines basicity, and steric effect. The implications of our results to atmospheric nanoparticle growth will be discussed.

Genetic and physical analyses of Methylobacterium organophilum XX genes encoding methanol oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machlin, S.M.; Tam, P.E.; Bastien, C.A.

When allyl alcohol was used as a suicide substrate, spontaneous mutants and UV light- and nitrous acid-generated mutants of Methylobacterium organophilum XX were selected which grew on methylamine but not on methanol. There was no detectable methanol dehydrogenase (MDH) activity in crude extracts of these mutants, yet Western blots revealed that some mutants still produced MDH protein. Complementation of 50 mutants by a cosmid gene bank of M. organophilum XX demonstrated that three major regions of the genome, each of which was separated by a minimum of 40 kilobases, were required for expression of active MDH. By subcloning and Tn5more » insertion mutagenesis of subcloned fragments, at least 11 genes clustered within these three regions were subsequently identified. The identity of the MDH structural gene, which was initially determined by hybridization to the structural gene of Methylobacterium sp. strain AM1, was confirmed by Western blot analysis of an MDH-..beta..-galactosidase fusion protein.« less

Borylnitrenes: electrophilic reactive intermediates with high reactivity towards C-H bonds.

PubMed

Bettinger, Holger F; Filthaus, Matthias

2010-12-21

Borylnitrenes (catBN 3a and pinBN 3b; cat = catecholato, pin = pinacolato) are reactive intermediates that show high tendency towards insertion into the C-H bonds of unactivated hydrocarbons. The present article summarizes the matrix isolation investigations that were aimed at identifying, characterizing and investigating the chemical behaviour of 3a by spectroscopic means, and of the experiments in solution and in the gas phase that were performed with 3b. Comparison with the reactivity reported for difluorovinylidene 1a in solid argon indicates that 3a shows by and large similar reactivity, but only after photochemical excitation. The derivative 3b inserts into the C-H bonds of hydrocarbon solvents in high yields and thus allows the formation of primary amines, secondary amines, or amides from "unreactive" hydrocarbons. It can also be used for generation of methylamine or methylamide from methane in the gas phase at room temperature. Remaining challenges in the chemistry of borylnitrenes are briefly summarized.

Enzymatic studies using quantum mechanical and molecular mechanical techniques

NASA Astrophysics Data System (ADS)

Faulder, Paul F.

Enzymes have evolved to increase the rate of biological reactions using fundamental physical processes. Until recently, the nature of catalysis has been based upon a classical model but it has since been considered that certain aspects of catalysis, particularly those concerning the transfer of a hydrogen species, may be accounted for using the theory of quantum mechanics. This thesis reports the use of reaction paths obtained using QMMM (combined quantum mechanics-molecular mechanics), combined with canonical variational transition state theory and multidimensional tunnelling corrections, to study two dehydrogenase enzymes, Liver Alcohol Dehydrogenase (LADH) and Methylamine Dehydrogenase (MADH). These methods are used to investigate the nature of these models in explaining reported experimental data indicative of quantum mechanical tunnelling within these enzymes. The results obtained are in good agreement with experimental data indicating the presence of tunnelling in LADH and, to a greater degree, in MADH, reflected in the magnitude of the calculated kinetic isotope effects (KIEs). For LADH, a primary tritium KIE of 5.6 is reported, calculated using transition state theory (TST) with a Wigner tunnelling correction, and compares favourably with an experimental value of 7.1. For MADH, a KIE of 11.1 was determined using canonical variational theory (CVT) with a small curvature tunnelling (SCT) correction, and compared favourably with an experimental value of 16.8. In addition, a relationship is observed between the contribution due to tunnelling in each system and the geometric positioning of the donating and accepting atoms of the transferring species, and is in qualitative agreement with current opinion concerning tunnelling and the dynamic nature of catalysis. Potential energy barriers have been obtained for both systems using QMMM. For LADH, barriers of 8.2 kcal mol-1 and 22.0 kcal mol-1, and reaction energies of -25.7 kcal mol-1 and +3.4 kcal mol-1, are reported for PM3 semiempirical and HF/3-21G respectively compared with an experimental barrier of 15.6 kcal mol-1 and reaction energy of +1.0 kcal mol-1. In MADH, a potential energy barrier of 9.1 kcal mol-1 is reported for PM3, compared with 10.7 kcal mol-1 experimentally. A reaction energy of -3.5 kcal mol-1 is also reported although no experimental data is available for comparison. All ah initio calculations produced significantly higher barriers and endothermic reaction energies. Chapter 1 presents a review of protein structure and classical enzyme catalysis, providing the foundations for a discussion of recent work concerning the application of quantum tunnelling in rationalising catalysis in certain enzymatic systems. Chapter 2 utilises the background information provided in Chapter 1 in a discussion specifically applied to previous experimental data concerning the structure, function and catalytic behaviour reported for the enzymes LADH and MADH. Chapter 3 presents a background to the methodology behind the theoretical methods used in the investigation of LADH and MADH reported in this thesis, in addition to reporting the development of extra code which has allowed the integration of our QMMM software with the rate determining program, POLYRATE, allowing the calculation of KIEs for these enzymes. Chapter 4 presents the preparation of the enzyme model of LADH with two separate substrates and the results obtained from subsequent QMMM calculations carried out on these models. These results are presented alongside results obtained by other workers, for comparative analysis. Chapter 5 details the preparation of a model of MADH with the substrate methylamine, and the QMMM investigation of the mode of catalysis for this enzyme using a variety of separate QMMM models. The calculation of KIEs on this enzyme, using the modified POLYRATE, are then presented in addition to KIEs determined for LADH based on results obtained from Chapter 4, and are discussed. The results of QMMM calculations carried out on MADH from a separate species are then presented in the context of validating the first set of results. Finally, QMMM calculations are presented for MADH bound to the substrate ethanolamine, attempting to elucidate the catalytically similar mechanism to methylamine.

Top-down systems biology integration of conditional prebiotic modulated transgenomic interactions in a humanized microbiome mouse model

PubMed Central

Martin, Francois-Pierre J; Wang, Yulan; Sprenger, Norbert; Yap, Ivan K S; Rezzi, Serge; Ramadan, Ziad; Peré-Trepat, Emma; Rochat, Florence; Cherbut, Christine; van Bladeren, Peter; Fay, Laurent B; Kochhar, Sunil; Lindon, John C; Holmes, Elaine; Nicholson, Jeremy K

2008-01-01

Gut microbiome–host metabolic interactions affect human health and can be modified by probiotic and prebiotic supplementation. Here, we have assessed the effects of consumption of a combination of probiotics (Lactobacillus paracasei or L. rhamnosus) and two galactosyl-oligosaccharide prebiotics on the symbiotic microbiome–mammalian supersystem using integrative metabolic profiling and modeling of multiple compartments in germ-free mice inoculated with a model of human baby microbiota. We have shown specific impacts of two prebiotics on the microbial populations of HBM mice when co-administered with two probiotics. We observed an increase in the populations of Bifidobacterium longum and B. breve, and a reduction in Clostridium perfringens, which were more marked when combining prebiotics with L. rhamnosus. In turn, these microbial effects were associated with modulation of a range of host metabolic pathways observed via changes in lipid profiles, gluconeogenesis, and amino-acid and methylamine metabolism associated to fermentation of carbohydrates by different bacterial strains. These results provide evidence for the potential use of prebiotics for beneficially modifying the gut microbial balance as well as host energy and lipid homeostasis. PMID:18628745

A mechanism for bacterial transformation of dimethylsulfide to dimethylsulfoxide: a missing link in the marine organic sulfur cycle.

PubMed

Lidbury, Ian; Kröber, Eileen; Zhang, Zhidong; Zhu, Yijun; Murrell, J Colin; Chen, Yin; Schäfer, Hendrik

2016-09-01

The volatile organosulfur compound, dimethylsulfide (DMS), plays an important role in climate regulation and global sulfur biogeochemical cycles. Microbial oxidation of DMS to dimethylsulfoxide (DMSO) represents a major sink of DMS in surface seawater, yet the underlying molecular mechanisms and key microbial taxa involved are not known. Here, we reveal that Ruegeria pomeroyi, a model marine heterotrophic bacterium, can oxidize DMS to DMSO using trimethylamine monooxygenase (Tmm). Purified Tmm oxidizes DMS to DMSO at a 1:1 ratio. Mutagenesis of the tmm gene in R. pomeroyi completely abolished DMS oxidation and subsequent DMSO formation. Expression of Tmm and DMS oxidation in R. pomeroyi is methylamine-dependent and regulated at the post-transcriptional level. Considering that Tmm is present in approximately 20% of bacterial cells inhabiting marine surface waters, particularly the marine Roseobacter clade and the SAR11 clade, our observations contribute to a mechanistic understanding of biological DMSO production in surface seawater. © 2016 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Nucleotide Sequence and Genetic Structure of a Novel Carbaryl Hydrolase Gene (cehA) from Rhizobium sp. Strain AC100

PubMed Central

Hashimoto, Masayuki; Fukui, Mitsuru; Hayano, Kouichi; Hayatsu, Masahito

2002-01-01

Rhizobium sp. strain AC100, which is capable of degrading carbaryl (1-naphthyl-N-methylcarbamate), was isolated from soil treated with carbaryl. This bacterium hydrolyzed carbaryl to 1-naphthol and methylamine. Carbaryl hydrolase from the strain was purified to homogeneity, and its N-terminal sequence, molecular mass (82 kDa), and enzymatic properties were determined. The purified enzyme hydrolyzed 1-naphthyl acetate and 4-nitrophenyl acetate indicating that the enzyme is an esterase. We then cloned the carbaryl hydrolase gene (cehA) from the plasmid DNA of the strain and determined the nucleotide sequence of the 10-kb region containing cehA. No homologous sequences were found by a database homology search using the nucleotide and deduced amino acid sequences of the cehA gene. Six open reading frames including the cehA gene were found in the 10-kb region, and sequencing analysis shows that the cehA gene is flanked by two copies of insertion sequence-like sequence, suggesting that it makes part of a composite transposon. PMID:11872471

Glyoxal in aqueous ammonium sulfate solutions: products, kinetics and hydration effects.

PubMed

Yu, Ge; Bayer, Amanda R; Galloway, Melissa M; Korshavn, Kyle J; Fry, Charles G; Keutsch, Frank N

2011-08-01

Reactions and interactions between glyoxal and salts in aqueous solution were studied. Glyoxal was found to react with ammonium to form imidazole, imidazole-2-carboxaldehyde, formic acid, N-glyoxal substituted imidazole, and minor products at very low concentrations. Overall reaction orders and rates for each major product were measured. Sulfate ions have a strong and specific interaction with glyoxal in aqueous solution, which shifts the hydration equilibria of glyoxal from the unhydrated carbonyl form to the hydrated form. This ion-specific effect contributes to the observed enhancement of the effective Henry's law coefficient for glyoxal in sulfate-containing solutions. The results of UV-vis absorption and NMR spectroscopy studies of solutions of glyoxal with ammonium, methylamine, and dimethylamine salts reveal that light absorbing compounds require the formation of nitrogen containing molecules. These findings have implications on the role of glyoxal in the atmosphere, both in models of the contribution of glyoxal to form secondary organic aerosol (SOA), the role of nitrogen containing species for aerosol optical properties and in predictions of the behavior of other carbonyls or dicarbonyls in the atmosphere.

Hygroscopicity of dicarbonyl-amine secondary organic aerosol products investigated with HTDMA

NASA Astrophysics Data System (ADS)

Hawkins, L. N.; de Haan, D. O.

2010-12-01

Recent studies have shown the importance of amine-dicarbonyl chemistry as a secondary organic aerosol (SOA) formation pathway, producing imines, imidazoles, and N-containing oligomers. Preliminary work in our group has suggested that some of these products may be surface active. Therefore, the presence of these products may result in important changes to submicron particle hygroscopicity that affect aerosol scattering and cloud condensation nuclei (CCN) activity, especially in regions with significant amine-containing particles. To investigate their hygroscopicity, we have designed a hygroscopicity tandem differential mobility analyzer (HTDMA) system around a 300 L Teflon chamber that allows for longer humidification times needed for some organic aerosol components that are only slightly hygroscopic. This modification provides a range of residence times from 2.5 minutes up to 1 hour, unlike previously published systems that vary from 2-30 seconds. Using the modified hygroscopicity tandem differential mobility analyzer (HTDMA), we have measured the hygroscopic growth factor (HGF) of SOA formed from reactions of glyoxal (and methylglyoxal) with methylamine, ammonium sulfate, and several amino acids. Changes to inorganic aerosol HGF in response to the presence of SOA products are also investigated.

Self-assembly of 2-aldehyde-8-hydroxyquinolinate-based lanthanide complexes and NIR luminescence

NASA Astrophysics Data System (ADS)

Zhang, Meiqi; Li, Hongfeng; Chen, Peng; Sun, Wenbin; Zhang, Lei; Yan, Pengfei

2015-02-01

Self-assembly reaction of 2-aldehyde-8-hydroxyquinoline, tris(hydroxymethyl)aminomethane and LnCl3ṡ6H2O affords a series of mononuclear lanthanide complexes Ce(baho)2·Et2O (1) (H2baho = 2,8-bis(2-(8-hydroxylquinolinyl))-1-aza-5-hydroxymethyl-3,7-dioxabicyclo[3.3.0]octane), Dy(nhm)2Cl·0.5H2O (2) and Ln(nhm)2Cl·0.5C6H14 (Ln = Ho (3), Er (4), Yb (5) and Hnhm = N-(2-(8-hydroxylquinolinyl)methylene)(trishydroxymethyl)methylamine. The crystal structures have been determined by X-ray crystallographic analysis, and the tetravalence of Ce in 1 has been proven by XPS. Interestingly, the positive charge of Ce4+ ion in 1 is neutralized by two deprotonated baho2- ligands, while two deprotonated nhm- ligands and one Cl- compensate the positive charge of Ln3+ ions in 2-5. Complex 5 exhibit essential NIR luminescence of Yb3+ ion with lifetime of 17.64 μs in solid and 9.96 μs in CH3OH solution.

Amine-Amine Exchange in Aminium-Methanesulfonate Aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawson, Matthew L.; Varner, Mychel E.; Perraud, Veronique M.

2014-12-18

Aerosol particles are ubiquitous in the atmosphere and have been shown to impact the Earth’s climate, reduce visibility, and adversely affect human health. Modeling the evolution of aerosol systems requires an understanding of the species and mechanisms involved in particle growth, including the complex interactions between particle- and gas-phase species. Here we report studies of displacement of amines (methylamine, dimethylamine or trimethylamine) in methanesulfonate salt particles by exposure to a different gas-phase amine, using a single particle mass spectrometer, SPLAT II. The variation of the displacement with the nature of the amine suggests that behavior is dependent on water inmore » or on the particles. Small clusters of methanesulfonic acid with amines are used as a model in quantum chemical calculations to identify key structural elements that are expected to influence water uptake, and hence the efficiency of displacement by gas-phase molecules in the aminium salts. Such molecular-level understanding of the processes affecting the ability of gas-phase amines to displace particle-phase aminium species is important for modeling the growth of particles and their impacts in the atmosphere.« less

Complex Organic Molecules Formation in Space Through Gas Phase Reactions: A Theoretical Approach

NASA Astrophysics Data System (ADS)

Redondo, Pilar; Barrientos, Carmen; Largo, Antonio

2017-02-01

Chemistry in the interstellar medium (ISM) is capable of producing complex organic molecules (COMs) of great importance to astrobiology. Gas phase and grain surface chemistry almost certainly both contribute to COM formation. Amino acids as building blocks of proteins are some of the most interesting COMs. The simplest one, glycine, has been characterized in meteorites and comets and, its conclusive detection in the ISM seems to be highly plausible. In this work, we analyze the gas phase reaction of glycine and {{{CH}}5}+ to establish the role of this process in the formation of alanine or other COMs in the ISM. Formation of protonated α- and β-alanine in spite of being exothermic processes is not viable under interstellar conditions because the different paths leading to these isomers present net activation energies. Nevertheless, glycine can evolve to protonated 1-imide-2, 2-propanediol, protonated amino acetone, protonated hydroxyacetone, and protonated propionic acid. However, formation of acetic acid and protonated methylamine is also a favorable process and therefore will be a competitive channel with the evolution of glycine to COMs.

Detecting Pyrolysis Products from Bacteria on Mars

NASA Technical Reports Server (NTRS)

Glavin, Daniel; Schubert, Michael; Botta, Oliver; Kminek, Gerhard; Bada, Jeffrey L.

2001-01-01

A pyrolysis/sublimation technique was developed to isolate volatile amine compounds from a Mars soil analogue inoculated with approx. 10 billion Escherichia coli cells. In this technique, the inoculated soil is heated to 500 C for several seconds at Martian ambient pressure and the sublimate, collected by a cold finger, then analyzed using high performance liquid chromatography. Methylamine and ethylamine, produced from glycine and alanine decarboxylation, were the most abundant amine compounds detected after pyrolysis of the cells. A heating cycle similar to that utilized in our experiment was also used to release organic compounds from the Martian soil in the 1976 Viking gas chromatography/mass spectrometry (GC/MS) pyrolysis experiment. The Viking GC/MS did not detect any organic compounds of Martian origin above a level of a few parts per billion in the Martian surface soil. Although the Viking GC/MS instruments were not specifically designed to search for the presence of living cells on Mars, our experimental results indicate that at the part per billion level, the degradation products generated from several million bacterial cells per gram of Martian soil would not have been detected.

DAMP, an acidotropic pH indicator, can be used as a tool to visualize non-esterified cholesterol in cells.

PubMed

Li, Weimin; Wang, Rong; Zhang, Shaojuan; Li, Xu

2015-02-01

Cholesterol-rich regions are attractive targets for studying metabolic disorders that involve accumulation of cholesterol. Despite efforts to develop probes for labelling cholesterol-rich regions in cells, few of these reagents have a low molecular weight. Previous studies have shown that the acidotropic pH indicator, N-{3-[(2,4-dinitrophenyl)amino]propyl}-N-(3-aminopropyl)methylamine dihydrochloride (DAMP), reacts with cholesterol-rich organelles, such as endocrine secretary granules from endocrine cells. In this study, we demonstrated that DAMP could react with free cholesterol in a dose-dependent manner, and DAMP was able to detect cholesterol-rich subcellular organelles. DAMP was sufficiently potent to detect free cholesterol-enriched organs, but was unable to detect atherosclerotic plaques primarily composed of esterified cholesterol. Taken together, these results demonstrate that DAMP facilitates the study of cholesterol-enriched lipid rafts and disorders which involve cholesterol accumulation. © The Author 2015. Published by ABBS Editorial Office in association with Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.

Isolation and complementation analysis of 10 methanol oxidation mutant classes and identification of the methanol dehydrogenase structural gene of Methylobacterium sp. strain AM1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nunn, D.N.; Lidstrom, M.E.

A method has been developed for the direct selection of methanol oxidation mutants of the facultative methylotroph Methylobacterium sp. strain AM1 (formerly Pseudomonas sp. strain AM1). Using this direct selection technique, we have isolated mutants of Methylobacterium sp. strain AM1 that are no longer capable of growth on methanol but retain the ability to grow on methylamine. These methanol oxidation (Mox) mutants were complemented with a genomic clone bank of this organism constructed in the broad-host-range cosmid pVK100, and subcloning and Tn5 mutagenesis experiments have assigned the Mox mutants to 10 distinct complementation groups. Using an open reading frame beta-galactosidasemore » fusion vector and antibodies specific for Methylobacterium sp. strain AM1 methanol dehydrogenase, we have identified the methanol dehydrogenase structural gene and determined the direction of transcription. The results suggest that the synthesis and utilization of an active methanol dehydrogenase in this organism requires at least 10 different gene functions.« less

A microanalytical method for ammonium and short-chain primary aliphatic amines using precolumn derivatization and capillary liquid chromatography.

PubMed

Moliner-Martínez, Y; Herráez-Hernández, R; Campíns-Falcó, P

2007-09-14

A new microscale method is presented for the determination of ammonium and primary short-chain aliphatic amines (methylamine, ethylamine, propylamine, n-butylamine and n-pentylamine) in water. The assay uses precolumn derivatization with the reagent o-phthaldialdehyde (OPA) in combination with the thiol N-acetyl-L-cysteine (NAC), and capillary liquid chromatography with UV detection at 330 nm. The described method is very simple and rapid as no preconcentration of the analytes is necessary, and the volume of sample required is only 0.1 mL. Under the proposed conditions good linearity has been obtained up to a concentration of the analytes of 10.0 mgL(-1), the limits of detection being of 8-50 microgL(-1). No matrix effect was found, and recoveries between 97 and 110% were obtained. The precision of the method was good, and the achieved variation coefficients were below 12%. The reliability of the proposed approach has been tested by analyzing a microsample of fogwater collected from leaf surfaces.

Phase equilibrium measurements on twelve binary mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giles, N.F.; Wilson, H.L.; Wilding, W.V.

1996-11-01

Phase equilibrium measurements have been performed on twelve binary mixtures. The PTx method was used to obtain vapor-liquid equilibrium data for the following binary systems at two temperatures each: ethanethiol + propylene; nitrobenzene + methanol; pyridine + ethyl acetate; octane + tert-amyl methyl ether; diisopropyl ether + butane; 1,3-dichloro-2-propanol + epichlorohydrin; 2,3-dichloro-1-propanol + epichlorohydrin; 2,3-epoxy-1-propanol + epichlorohydrin; 3-chloro-1,2-propanediol + epichlorohydrin; methanol + hydrogen cyanide. For these systems, equilibrium vapor and liquid phase compositions were derived from the PTx data using the Soave equation of state to represent the vapor phase and the Wilson, NRTL, or Redlich-Kister activity coefficient model tomore » represent the liquid phase. The infinite dilution activity coefficient of methylamine in N-methyl-2-pyrrolidone was determined at three temperatures by performing PTx measurements on the N-methyl-2-pyrrolidone was determined at three temperatures by performing PTx measurements on the N-methyl-2-pyrrolidone-rich half of the binary. Liquid-liquid equilibrium studies were made on the triethylene glycol + 1-pentene system at two temperatures by directly analyzing samples taken from each liquid phase.« less

Reactivity and biological properties of a series of cytotoxic PtI2(amine)2 complexes, either cis or trans configured.

PubMed

Messori, Luigi; Cubo, Leticia; Gabbiani, Chiara; Álvarez-Valdés, Amparo; Michelucci, Elena; Pieraccini, Giuseppe; Ríos-Luci, Carla; León, Leticia G; Padrón, José M; Navarro-Ranninger, Carmen; Casini, Angela; Quiroga, Adoración G

2012-02-06

Six diiodido-diamine platinum(II) complexes, either cis or trans configured, were prepared, differing only in the nature of the amine ligand (isopropylamine, dimethylamine, or methylamine), and their antiproliferative properties were evaluated against a panel of human tumor cell lines. Both series of complexes manifested pronounced cytotoxic effects, with the trans isomers being, generally, more effective than their cis counterparts. Cell cycle analysis revealed different modes of action for these new Pt(II) complexes with respect to cisplatin. The reactivity of these platinum compounds with a number of biomolecules, including cytochrome c, two sulfur containing modified amino acids, 9-ethylguanine, and a single strand oligonucleotide, was analyzed in depth by mass spectrometry and NMR spectroscopy. Interestingly, significant differences in the reactivity of the investigated compounds toward the various model biomolecules were observed: in particular we observed that trans complexes preferentially release their iodide ligands upon biomolecule binding, while the cis isomers may release the amine ligands with retention of iodides. Such differences in reactivity may have important mechanistic implications and a relevant impact on the respective pharmacological profiles.

Time-resolved FT EPR and optical spectroscopy study on photooxidation of aliphatic alpha-amino acids in aqueous solutions; electron transfer from amino vs carboxylate functional group.

PubMed

Tarabek, Peter; Bonifacić, Marija; Beckert, Dieter

2006-06-08

Using time-resolved Fourier transform electron paramagnetic resonance, FT EPR, and optical spectroscopy, the photooxidation of glycine, alpha-alanine, alpha-aminoisobutyric acid, and model compounds beta-alanine, methylamine and sodium acetate, by excited triplets of anthraquinone-2,6-disulfonate dianion was studied in aqueous solutions in the pH range 5-13. Anthraquinone radical trianions showing strong emissive spin-polarization (CIDEP) were formed, indicating fast electron transfer from the quenchers to the spin-polarized quinone triplet as the primary reaction. None of the primary radicals formed upon one-electron oxidation of quenchers could be detected at the nanosecond time scale of FT EPR measurements because of their very fast transformation into secondary products. The latter were identified to be decarboxylated alpha-aminoalkyl radicals for alpha-amino acids anions and zwitterions, beta-aminoalkyl radicals for beta-alanine zwitterions, and methyl radicals for acetate anions; corresponding aminyl radicals were the first EPR detectable products from beta-alanine anions and methylamine. Thus, anthraquinone-2,6-disulfonate triplet can take an electron from both NH(2)- and -CO(2)(-) functional groups forming aminium ((+*)NH(2)-) and acyloxyl (-CO(2)(*)) radicals, respectively. Aminium radicals derived from beta-alanine anions and CH(3)-NH(2) stabilize by deprotonation into aminyl radicals, whereas these derived from alpha-amino acids anions are known to suffer ultrafast decarboxylation (tau approximately 10 ps). Analysis of the polarization patterns revealed that decarboxylation from acyloxyl radicals are considerably slower (ns < tau < 0.1 micros). Therefore, in the case of alpha-amino acids, the isoelectronic structures NH(2)-CR(2)-CO(2)(*) and (+*)NH(2)-CR(2)-CO(2)(-) probably do not constitute resonance mesomeric forms of one and the same species and the decarboxylation of aminium radicals is not preceded by the intramolecular carboxylate to amino group electron transfer. Absolute triplet quenching rate constants at zero ionic strength were in the range of 2 x 10(8) to 2 x 10(9) M(-1) s(-1) for R-NH(2) and 2 x 10(7) to 10(8) M(-1) s(-1) for R-CO(2)(-) type of electron donors, reflecting in principle their standard reduction potentials. The strengths of acids: (+)NH(3)-(*)CH(2), (+)NH(3)-(*)C(CH(3))H, and (+)NH(3)-(*)C(CH(3))(2), pK(a) <4, >6, and >7, respectively, were found to be remarkably strongly dependent on alpha-C substitution. The conjugate bases of these alpha-aminoalkyl radicals reduce anthraquinone-2,6-disulfonate dianion ground state with k(sec) = 3 x 10(9) M(-1) s(-1).

Salinity and Temperature Constraints on Microbial Methanogenesis in the Lei-Gong-Huo Mud Volcano of Eastern Taiwan

NASA Astrophysics Data System (ADS)

Sun, W.; Lin, L.; Wang, P.

2012-12-01

Terrestrial mud volcano is thought to be one of the most important natural sources of methane emission. Previous studies have shown that methane cycling in terrestrial mud volcanoes involves a complex reaction network driven by the interactions between subsurface and surface abiotic and microbial processes. In situ methanogenesis appears to produce methane at quantities exceeding those of deeply-sourced thermogenic methane and the capacities of anaerobic methanotrophy at shallow depth levels, thereby contributing significantly to the methane emission. Various degrees of evaporation at surface also lead to the enhancement of chloride concentrations in pore water, favoring the proliferation of halo-tolerant and/or halophilic methanogens. The goal of this study is to investigate the extent of methanogenesis in terrestrial mud volcanoes by incubating mud slurries with various precursors (H2/CO2, acetate, methanol, and methylamine) at different salinities (up to 2000 mM) and temperatures (up to 50 oC). Methane concentrations were monitored through time and molecular analyses were applied to investigate the changes of methanogenic communities. Methanogenesis was stimulated by any investigated precursor at room temperature. However, the methanogenic response to salinity varied. Of the investigated precursors, H2/CO2 and methyl-compounds (methanol and methylamine) stimulated methanogenesis at all investigated salinities. The rates and yields of hydrogen- and methyl-utilizing methanogenesis declined significantly at salinities greater than 1500 mM. Acetate-utilizing methanogenesis proceeded at salinities less than 700 mM. At 40 oC, methanogenesis was stimulated by all investigated precursors at the in situ salinity (~400 mM). At 50 oC, only H2-utilizing methanogenesis was stimulated. Analyses of terminal restriction fragment length polymorphism (TRFLP) for 16S rRNA genes revealed various patterns upon different precursors and salinities. The TRFLP results combined with clone library analyses indicated that major RFs recovered from incubations with methyl-compounds at room temperature and 40 oC were represented by sequences affiliated with Methanococcoides spp., Methanosarcina spp., and Methanolobus spp. In particular, only Methanosarcina- and Methanococcoides-related members were detected at salinities greater than 1000 mM or at 40 oC. RFs recovered from incubations with H2/CO2 at room temperature and 40 oC were represented by sequences related to different Methanococcus spp. Overall, methanogens utilizing H2/CO2 and methyl-compounds appear to be capable of actively producing methane at salinities greater than acetate-utilizing methanogens could tolerate. These methanogens might adapt better to the fluctuation of salinity or extremely high salinity induced by the surface evaporation in terrestrial mud volcanoes. When considering the overall methane emission from terrestrial mud volcanoes, these halo-tolerant methanogens become a significant factor. Key words: mud volcano, Methane, Methanogenesis, Salinity

Comparison of point-source pollutant loadings to soil and groundwater for 72 chemical substances.

PubMed

Yu, Soonyoung; Hwang, Sang-Il; Yun, Seong-Taek; Chae, Gitak; Lee, Dongsu; Kim, Ki-Eun

2017-11-01

Fate and transport of 72 chemicals in soil and groundwater were assessed by using a multiphase compositional model (CompFlow Bio) because some of the chemicals are non-aqueous phase liquids or solids in the original form. One metric ton of chemicals were assumed to leak in a stylized facility. Scenarios of both surface spills and subsurface leaks were considered. Simulation results showed that the fate and transport of chemicals above the water table affected the fate and transport of chemicals below the water table, and vice versa. Surface spill scenarios caused much less concentrations than subsurface leak scenarios because leaching amounts into the subsurface environment were small (at most 6% of the 1 t spill for methylamine). Then, simulation results were applied to assess point-source pollutant loadings to soil and groundwater above and below the water table, respectively, by multiplying concentrations, impact areas, and durations. These three components correspond to the intensity of contamination, mobility, and persistency in the assessment of pollutant loading, respectively. Assessment results showed that the pollutant loadings in soil and groundwater were linearly related (r 2  = 0.64). The pollutant loadings were negatively related with zero-order and first-order decay rates in both soil (r = - 0.5 and - 0.6, respectively) and groundwater (- 1.0 and - 0.8, respectively). In addition, this study scientifically defended that the soil partitioning coefficient (K d ) significantly affected the pollutant loadings in soil (r = 0.6) and the maximum masses in groundwater (r = - 0.9). However, K d was not a representative factor for chemical transportability unlike the expectation in chemical ranking systems of soil and groundwater pollutants. The pollutant loadings estimated using a physics-based hydrogeological model provided a more rational ranking for exposure assessment, compared to the summation of persistency and transportability scores in the chemical ranking systems. In the surface spill scenario, the pollutant loadings were zeros for all chemicals, except methylamine to soil whose pollutant loading was smaller than that in the subsurface leak scenario by 4 orders of magnitude. The maximum mass and the average mass multiplied by duration in soil greatly depended on leaching fluxes (r = 1.0 and 0.9, respectively), while the effect of leaching fluxes diminished below the water table. The contribution of this work is that a physics-based numerical model was used to quantitatively compare the subsurface pollutant loading in a chemical accident for 72 chemical substances, which can scientifically defend a simpler and more qualitative assessment of pollutant loadings. Besides, this study assessed pollutant loadings to soil (unsaturated zone) and groundwater (saturated zone) all together and discussed their interactions.

Biological and nonbiological modifications of carbamates

PubMed Central

Knaak, James B.

1971-01-01

Methylcarbamate insecticides undergo hydrolysis, oxidation, dealkylation, and conjugation in animals, plants, and insects to form similar or identical products. Carbaryl is hydroxylated in biological systems to form hydroxy, dihydro-dihydroxy, and N-hydroxymethyl carbaryl and is hydrolysed to form 1-naphthol. The products are conjugated, stored, or excreted. Carbofuran is hydroxylated at the 3 position and propoxur at the 5 position to form hydroxylated derivatives. N-hydroxymethyl derivatives of these two carbamates may also be formed. Hydrolysis appears to be the major metabolic pathway of carbofuran in the animal. Aldicarb is oxidized to its sulfoxide and then hydrolysed to the oxime sulfoxide in animals and plants. Plants hydrolyse the oxime sulfoxide to form the corresponding aldehyde, which is an intermediate in the formation of 2-methyl-2-(methyl-sulfinyl)propanol. Methomyl, which is structurally similar to aldicarb, is metabolized in plants to acetonitrile, carbon dioxide, and methylamine. Bux and Meobal undergo hydrolysis and hydroxylation to form N-hydroxy methylcarbamates, as well as hydroxybutylphenyl and hydroxymethylphenyl methylcarbamates. Zectran, which contains a dimethylamino group, is converted to the methylamino, amino, and methylformamido derivatives by insects and plants. In soil and water, methylcarbamate insecticides are hydrolysed to their respective phenols or oximes. PMID:4999481

Evidence for a Na/H Antiporter in Membrane Vesicles Isolated from Roots of the Halophyte Atriplex nummularia.

PubMed

Braun, Y; Hassidim, M; Lerner, H R; Reinhold, L

1988-05-01

The ATP-dependent establishment of a positive membrane potential (measured as S(14)CN(-)-accumulation) in membrane vesicles isolated from the roots of Atriplex nummularia Lindl. was not inhibited by NaMes and KMes at concentrations up to 140 millimolar. On the other hand, the formation of DeltapH (measured as (14)C-methylamine accumulation or quenching of quinacrine fluorescence), was depressed by NaMes concentrations as low as 30 millimolar. Supply of NaMes after the DeltapH had been established brought about partial dissipation within 30 seconds. Extent of dissipation of DeltapH increased with NaMes concentration over the range tested (up to 180 millimolar). The H(+)/Na(+) exchange indicated by these results was not due to the creation of a Na(+) diffusion potential. Formation of DeltapH in these vesicles was stable to NO(3) (-) up to 100 millimolar; further, the dissipating effect of Na(+) supply was apparent on a DeltapH formed in the presence of 30 millimolar NO(3) (-). Additional evidence that the origin of the membrane vesicles observed in this investigation was not the tonoplast and was probably the plasmalemma included the vanadate sensitivity of the establishment of the membrane potential.

The permeability of the endplate channel to organic cations in frog muscle

PubMed Central

1980-01-01

The relative permeability of endplate channels to many organic cations was determined by reversal-potential criteria. Endplate currents induced by iontophoretic "puffs" of acetylcholine were studied by a Vaseline gap, voltage clamp method in cut muscle fibers. Reversal potential changes were measured as the NaCl of the bathing medium was replaced by salts of organic cations, and permeability ratios relative to Na+ ions were calculated from the Goldman-Hodgkin-Katz equation. 40 small monovalent organic cations had permeability ratios larger than 0.1. The most permeant including NH4+, hydroxylamine, hydrazine, methylamine, guanidine, and several relatives of guanidine had permeability ratios in the range 1.3--2.0. However, even cations such as imidazole, choline, tris(hydroxymethyl)aminomethane, triethylamine, and glycine methylester were appreciably permeant with permeability ratios of 0.13--0.95. Four compounds with two charged nitrogen groups were also permeant. Molecular models of the permeant ions suggest that the smallest cross-section of the open pore must be at least as large as a square, 6.5 A x 6.5 A. Specific chemical factors seem to be less important than access or friction in determining the ionic selectivity of the endplate channel. PMID:6247422

Brown Carbon Production in Aldehyde + Ammonium Sulfate Mixtures: Effects of Formaldehyde and Amines

NASA Astrophysics Data System (ADS)

Powelson, M.; De Haan, D. O.

2012-12-01

The formation of light-absorbing 'brown carbon,' or HULIS (humic- like substances), in atmospheric aerosol has an important impact on climate. However, the precursors responsible for brown carbon formation have not been identified. Several aldehydes present in clouds (methylglyoxal, glycolaldehyde, hydroxyacetone, glyoxal, and acetaldehyde) have the potential to create brown products when reacted with ammonium sulfate or primary amines such as methylamine or glycine. The formation of light-absorbing products from these reactions was characterized as a function of cloud-relevant pH (from 3- 6) using UV-Visible spectroscopy. Of the different aldehydes teste, the largest production rates of light-absorbing compounds were observed in reactions of glycolaldehyde and methylglyoxal. Primary amines produced more light- absorbing products than ammonium sulfate at lower concentrations. The addition of formaldehyde to any reaction with other aldehydes decreased the formation of light-absorbing products, while the addition of a small amount (1:5 mole ratio) of glycine to aldehyde + ammonium sulfate reactions can increase the production of light-absorbing products. These results suggest that the presence of primary amines significantly influence atmospheric brown carbon production by aldehydes even when much greater quantities of ammonium sulfate are present.

Biotechnological and Agronomic Potential of Endophytic Pink-Pigmented Methylotrophic Methylobacterium spp.

PubMed Central

Dourado, Manuella Nóbrega; Aparecida Camargo Neves, Aline; Santos, Daiene Souza; Araújo, Welington Luiz

2015-01-01

The genus Methylobacterium is composed of pink-pigmented facultative methylotrophic (PPFM) bacteria, which are able to synthesize carotenoids and grow on reduced organic compounds containing one carbon (C1), such as methanol and methylamine. Due to their high phenotypic plasticity, these bacteria are able to colonize different habitats, such as soil, water, and sediment, and different host plants as both endophytes and epiphytes. In plant colonization, the frequency and distribution may be influenced by plant genotype or by interactions with other associated microorganisms, which may result in increasing plant fitness. In this review, different aspects of interactions with the host plant are discussed, including their capacity to fix nitrogen, nodule the host plant, produce cytokinins, auxin and enzymes involved in the induction of systemic resistance, such as pectinase and cellulase, and therefore plant growth promotion. In addition, bacteria belonging to this group can be used to reduce environmental contamination because they are able to degrade toxic compounds, tolerate high heavy metal concentrations, and increase plant tolerance to these compounds. Moreover, genome sequencing and omics approaches have revealed genes related to plant-bacteria interactions that may be important for developing strains able to promote plant growth and protection against phytopathogens. PMID:25861650

Unravelling the Conformational Landscape of Nicotinoids: the Structure of Cotinine by Broadband Rotational Spectroscopy

NASA Astrophysics Data System (ADS)

Uriarte, Iciar; Ecija, Patricia; Cocinero, Emilio J.; Perez, Cristobal; Caballero-Mancebo, Elena; Lesarri, Alberto

2015-06-01

Alkaloids such as nicotine, cotinine or anabasine share a common floppy structural motif consisting of a two-ring assembly with a 3-pyridil methylamine skeleton. In order to investigate the structure-activity relationship of these biomolecules, structural studies with rotational resolution have been carried out for nicotine and anabasine in the gas phase, where these molecules can be probed in an "interaction-free" environment (no solvent or crystal-packing interactions). We hereby present a structural investigation of cotinine in a jet expansion using the chirped-pulse Fourier-transform microwave (CP-FTMW) spectrometer recently built at the University of the Basque Country (UPV-EHU). The rotational spectrum (6-18 GHz) reveals the presence of two different conformations. The conformational preferences of cotinine originate from the internal rotation of the two ring moieties, the detected species differing in a near 180° rotation of pyridine. The final structure is modulated by steric effects. J.-U. Grabow, S. Mata, J. L. Alonso, I. Peña, S. Blanco, J. C. López, C. Cabezas, Phys. Chem. Chem. Phys. 2011, 13, 21063. A. Lesarri, E. J. Cocinero, L. Evangelisti, R. D. Suenram, W. Caminati, J.-U. Grabow, Chem. Eur. J. 2010, 16, 10214.

Methylophaga natronica sp. nov., a new alkaliphilic and moderately halophilic, restricted-facultatively methylotrophic bacterium from soda lake of the Southern Transbaikal region.

PubMed

Doronina, Nina; Darmaeva, Tsyregma; Trotsenko, Yuri

2003-09-01

A new, moderately haloalkaliphilic and restricted-facultatively methylotrophic bacterium (strain Bur2T) with the ribulose monophosphate pathway of carbon assimilation is described. The isolate, which utilizes methanol, methylamine and fructose, is an aerobic, Gram-negative, asporogenous, motile short rod multiplying by binary fission. It is auxotrophic for vitamin B12, and requires NaHCO3 or NaCl for growth in alkaline medium. Cellular fatty acids profile consists primarily of straight-chain saturated C16:0, unsaturated C16:1 and C18:1 acids. The major ubiquinone is Q-8. The dominant phospholipids are phosphatidylethanolamine and phosphatidylglycerol. Diphosphatidylglycerol is also present. Optimal growth conditions are 25-29 degrees C, pH 8.5-9.0 and 2-3% (w/v) NaCl. Cells accumulate ectoine and glutamate as the main osmoprotectants. The G + C content of the DNA is 45.0 mol%. Based on 16S rDNA sequence analysis and DNA-DNA relatedness (25-35%) with type strains of marine and soda lake methylobacteria belonging to the genus Methylophaga, the novel isolate was classified as a new species of this genus and named Methylophaga natronica (VKM B-2288T).

Structure prediction and analysis of MxaF from obligate, facultative and restricted facultative methylobacterium.

PubMed

Singh, Raghvendra Pratap; Singh, Ram Nageena; Srivastava, Manish K; Srivastava, Alok Kumar; Kumar, Sudheer; Dubey, Ramesh Chandra; Sharma, Arun Kumar

2012-01-01

Methylobacteria are ubiquitous in the biosphere which are capable of growing on C1 compounds such as formate, formaldehyde, methanol and methylamine as well as on a wide range of multi-carbon growth substrates such as C2, C3 and C4 compounds due to the methylotrophic enzymes methanol dehydrogenase (MDH). MDH is performing these functions with the help of a key protein mxaF. Unfortunately, detailed structural analysis and homology modeling of mxaF is remains undefined. Hence, the objective of this research is the characterization and three dimensional modeling of mxaF protein from three different methylotrophs by using I-TASSER server. The predicted model were further optimize and validate by Profile 3D, Errat, Verifiy3-D and PROCHECK server. Predicted and best evaluated models have been successfully deposited to PMDB database with PMDB ID PM0077505, PM0077506 and PM0077507. Active site identification revealed 11, 13 and 14 putative functional site residues in respected models. It may play a major role during protein-protein, and protein-cofactor interactions. This study can provide us an ab-initio and detail information to understand the structure, mechanism of action and regulation of mxaF protein.

Structure prediction and analysis of MxaF from obligate, facultative and restricted facultative methylobacterium

PubMed Central

Singh, Raghvendra Pratap; Singh, Ram Nageena; Srivastava, Manish K; Srivastava, Alok Kumar; Kumar, Sudheer; Dubey, Ramesh Chandra; Sharma, Arun Kumar

2012-01-01

Methylobacteria are ubiquitous in the biosphere which are capable of growing on C1 compounds such as formate, formaldehyde, methanol and methylamine as well as on a wide range of multi-carbon growth substrates such as C2, C3 and C4 compounds due to the methylotrophic enzymes methanol dehydrogenase (MDH). MDH is performing these functions with the help of a key protein mxaF. Unfortunately, detailed structural analysis and homology modeling of mxaF is remains undefined. Hence, the objective of this research is the characterization and three dimensional modeling of mxaF protein from three different methylotrophs by using I-TASSER server. The predicted model were further optimize and validate by Profile 3D, Errat, Verifiy3-D and PROCHECK server. Predicted and best evaluated models have been successfully deposited to PMDB database with PMDB ID PM0077505, PM0077506 and PM0077507. Active site identification revealed 11, 13 and 14 putative functional site residues in respected models. It may play a major role during protein-protein, and protein-cofactor interactions. This study can provide us an ab-initio and detail information to understand the structure, mechanism of action and regulation of mxaF protein. PMID:23275704

Room-Temperature Synthesis of Thiostannates from {[Ni(tren)]2[Sn2S6]}n.

PubMed

Hilbert, Jessica; Näther, Christian; Weihrich, Richard; Bensch, Wolfgang

2016-08-15

The compound {[Ni(tren)]2[Sn2S6]}n (1) (tren = tris(2-aminoethyl)amine, C6H18N4) was successfully applied as source for the room-temperature synthesis of the new thiostannates [Ni(tren)(ma)(H2O)]2[Sn2S6]·4H2O (2) (ma = methylamine, CH5N) and [Ni(tren)(1,2-dap)]2[Sn2S6]·2H2O (3) (1,2-dap = 1,2-diaminopropane, C3H10N2). The Ni-S bonds in the Ni2S2N8 bioctahedron in the structure of 1 are analyzed with density functional theory calculations demonstrating significantly differing Ni-S bond strengths. Because of this asymmetry they are easily broken in the presence of an excess of ma or 1,2-dap immediately followed by Ni-N bond formation to N donor atoms of the amine ligands thus generating [Ni(tren)(amine)](2+) complexes. The chemical reactions are fast, and compounds 2 and 3 are formed within 1 h. The synthesis concept presented here opens hitherto unknown possibilities for preparation of new thiostannates.

The Composition of Comet C/2009 PI (Garradd) from Infrared Spectroscopy: Evidence for an Oxygen-Rich Heritage?

NASA Technical Reports Server (NTRS)

DiSanti, M. A.; Bonev, B. P.; Villanueva, G. L.; Paganini, L.; Mumma, M. J.; Charnley, S. B.; Keane, J. V.; Meech, K. J.; Blake, G. A.; Boehnhardt, H.;

The Composition of Comet C/2009 P1 (Garradd) from Infrared Spectroscopy: Evidence for an Oxygen-Rich Heritage?

NASA Technical Reports Server (NTRS)

DiSanti, M. A.; Bonev, B. P.; Villaneueva, G. L.; Paganini, L.; Mumma, M. J.; Charnley, S. B.; Keane, J. V.; Blake, G. A.; Boehnhardt, H.; Lippi, M.

2012-01-01

Comets retain relatively primitive icy material remaining from the epoch of Solar System formation, however the extent to which their ices are modified remains a key question in cometary science. One way to address this is to measure the relative abundances of primary (parent) volatiles in comets (i.e., those ices native to the nucleus). High-resolution (lambda/delta lambda greater than 10(exp 4)) infrared spectroscopy is a powerful tool for measuring parent volatiles in comets through their vibrational emissions in the approximately 3-5 micrometer region. With modern instrumentation on world-class telescopes, we can quantify a multitude of species (e.g., H2O, C2H2, CH4, C2H6, CO, H2CO, CH3OH, HCN, NH3), even in comets with modest gas production. In space environments, compounds of keen interest to astrobiology could originate from HCN and NH3 (leading to amino acids), H2CO (leading to sugars), or C2H6, and CH4 (suggested precursors of ethyl- and methylamine). Measuring the abundances of these precursor molecules and their variability among comets contributes to understanding the synthesis of the more complex prebiotic compounds.

Photometric Characterization of the Reductive Amination Scope of the Imine Reductases from Streptomyces tsukubaensis and Streptomyces ipomoeae.

PubMed

Matzel, Philipp; Krautschick, Lukas; Höhne, Matthias

2017-10-18

Imine reductases (IREDs) have emerged as promising enzymes for the asymmetric synthesis of secondary and tertiary amines starting from carbonyl substrates. Screening the substrate specificity of the reductive amination reaction is usually performed by time-consuming GC analytics. We found two highly active IREDs in our enzyme collection, IR-20 from Streptomyces tsukubaensis and IR-Sip from Streptomyces ipomoeae, that allowed a comprehensive substrate screening with a photometric NADPH assay. We screened 39 carbonyl substrates combined with 17 amines as nucleophiles. Activity data from 663 combinations provided a clear picture about substrate specificity and capabilities in the reductive amination of these enzymes. Besides aliphatic aldehydes, the IREDs accepted various cyclic (C 4 -C 8 ) and acyclic ketones, preferentially with methylamine. IR-Sip also accepted a range of primary and secondary amines as nucleophiles. In biocatalytic reactions, IR-Sip converted (R)-3-methylcyclohexanone with dimethylamine or pyrrolidine with high diastereoselectivity (>94-96 % de). The nucleophile acceptor spectrum depended on the carbonyl substrate employed. The conversion of well-accepted substrates could also be detected if crude lysates were employed as the enzyme source. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Genomics of Methylotrophy in Gram-Positive Methylamine-Utilizing Bacteria

PubMed Central

McTaggart, Tami L.; Beck, David A. C.; Setboonsarng, Usanisa; Shapiro, Nicole; Woyke, Tanja; Lidstrom, Mary E.; Kalyuzhnaya, Marina G.; Chistoserdova, Ludmila

2015-01-01

Gram-positive methylotrophic bacteria have been known for a long period of time, some serving as model organisms for characterizing the specific details of methylotrophy pathways/enzymes within this group. However, genome-based knowledge of methylotrophy within this group has been so far limited to a single species, Bacillus methanolicus (Firmicutes). The paucity of whole-genome data for Gram-positive methylotrophs limits our global understanding of methylotrophy within this group, including their roles in specific biogeochemical cycles, as well as their biotechnological potential. Here, we describe the isolation of seven novel strains of Gram-positive methylotrophs that include two strains of Bacillus and five representatives of Actinobacteria classified within two genera, Arthrobacter and Mycobacterium. We report whole-genome sequences for these isolates and present comparative analysis of the methylotrophy functional modules within these genomes. The genomic sequences of these seven novel organisms, all capable of growth on methylated amines, present an important reference dataset for understanding the genomic basis of methylotrophy in Gram-positive methylotrophic bacteria. This study is a major contribution to the field of methylotrophy, aimed at closing the gap in the genomic knowledge of methylotrophy within this diverse group of bacteria. PMID:27682081

Biotechnological and agronomic potential of endophytic pink-pigmented methylotrophic Methylobacterium spp.

PubMed

Dourado, Manuella Nóbrega; Camargo Neves, Aline Aparecida; Santos, Daiene Souza; Araújo, Welington Luiz

2015-01-01

The genus Methylobacterium is composed of pink-pigmented facultative methylotrophic (PPFM) bacteria, which are able to synthesize carotenoids and grow on reduced organic compounds containing one carbon (C1), such as methanol and methylamine. Due to their high phenotypic plasticity, these bacteria are able to colonize different habitats, such as soil, water, and sediment, and different host plants as both endophytes and epiphytes. In plant colonization, the frequency and distribution may be influenced by plant genotype or by interactions with other associated microorganisms, which may result in increasing plant fitness. In this review, different aspects of interactions with the host plant are discussed, including their capacity to fix nitrogen, nodule the host plant, produce cytokinins, auxin and enzymes involved in the induction of systemic resistance, such as pectinase and cellulase, and therefore plant growth promotion. In addition, bacteria belonging to this group can be used to reduce environmental contamination because they are able to degrade toxic compounds, tolerate high heavy metal concentrations, and increase plant tolerance to these compounds. Moreover, genome sequencing and omics approaches have revealed genes related to plant-bacteria interactions that may be important for developing strains able to promote plant growth and protection against phytopathogens.

Recent Selected Ion Flow Tube (SIFT) Studies Concerning the Formation of Amino Acids in the Gas Phase

NASA Technical Reports Server (NTRS)

Jackson, Douglas M.; Adams, Nigel G.; Babcock, Lucia M.

2006-01-01

Recently the simplest amino acid, glycine, has been detected in interstellar clouds, ISC, although this has since been contested. In order to substantiate either of these claims, plausible routes to amino acids need to be investigated. For gas phase synthesis, the SIFT technique has been employed to study simple amino acids via ion-molecule reactions of several ions of interstellar interest with methylamine, ethylamine, formic acid, acetic acid, and methyl formate. Carboxylic acid type ions were considered in the reactions involving the amines. In reactions where the carboxylic acid and methyl formate neutrals were studied, the reactant ions were primarily amine ion fragments. It was observed that the amines and acids preferentially fragment or accept a proton whenever energetically possible. NH3(+), however, uniquely reacted with the neutrals via atom abstraction to form NH4(+). These studies yielded a body of data relevant to astrochemistry, supplementing the available literature. However, the search for gas phase routes to amino acids using conventional molecules has been frustrated. Our most recent research investigates the fragmentation patterns of several amino acids and several possible routes have been suggested for future study.

Methylobacterium gossipiicola sp. nov., a pink-pigmented, facultatively methylotrophic bacterium isolated from the cotton phyllosphere.

PubMed

Madhaiyan, Munusamy; Poonguzhali, Selvaraj; Senthilkumar, Murugaiyan; Lee, Jung-Sook; Lee, Keun-Chul

2012-01-01

A pink, aerobic, facultatively methylotrophic, motile, Gram-negative rod, designated Gh-105(T), was isolated from the phyllosphere of cotton from Coimbatore (Tamilnadu, India). 16S rRNA gene sequence analysis showed clearly that the isolate belonged to the Methylobacterium cluster. Strain Gh-105(T) was most closely related to Methylobacterium adhaesivum AR27(T) (99% 16S rRNA gene sequence similarity) and Methylobacterium iners 5317S-33(T) (97.5%). The isolate grew with C(1) compounds such as methanol and dichloromethane, but not with formaldehyde, formate, methylamine, trimethylamine or methane, as sole carbon sources and carried mxaF, which encodes methanol dehydrogenase and supports methylotrophic metabolism. The major fatty acid was C(18:1)ω7c and the G+C content of the genomic DNA was 64.2 mol%. Physiological and biochemical data and DNA-DNA relatedness with M. adhaesivum KACC 12195(T) and M. iners KACC 11765(T) revealed clear phenotypic and genotypic differences. For this reason, we propose that strain Gh-105(T) (=CCM 7572(T) =NRRL B-51692(T)) represents the type strain of a novel species, with the name Methylobacterium gossipiicola sp. nov.

A Novel Pentadentate Coordination Mode for the Carbonato Bridge: Synthesis, Crystal Structure, and Magnetic Behavior of (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)], a New Trinuclear Nickel(II) Carbonato-Bridged Complex with Strong Antiferromagnetic Coupling.

PubMed

Escuer, Albert; Vicente, Ramon; Kumar, Sujit B.; Solans, Xavier; Font-Bardía, Mercé; Caneschi, Andrea

1996-05-22

The trinuclear complex (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] was obtained by reaction of basic solutions of nickel(II), Medpt (bis(3aminopropyl)methylamine) and thiocyanate ligand with atmospheric CO(2) or by simple reaction with carbonate anion. (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] crystallizes in the triclinic system, space group P&onemacr;, with a = 12.107(5) Å, b = 12.535(7) Å, c = 16.169(9) Å, alpha = 102.69(5) degrees, beta = 92.91(5) degrees, gamma = 118.01(4) degrees, Z = 2, and R = 0.043. The three nickel atoms are asymmetrically bridged by one pentadentate carbonato ligand, which shows a novel coordination mode. The (&mgr;(3)-CO(3))[Ni(3)(Medpt)(3)(NCS)(4)] compound shows a very strong antiferromagnetic coupling. Fit as irregular triangular arrangement gave J(1) = -88.4, J(2) = -57.7, and J(3) = -9.6 cm(-)(1), which is the strongest AF coupling observed to date for Ni(3) compounds. The magnetic behavior of the carbonato bridge is discussed.

Synthesis, spectroscopic characterization and biological evaluation of unsymmetrical aminosquarylium cyanine dyes.

PubMed

Friães, Sofia; Silva, Amélia M; Boto, Renato E; Ferreira, Diana; Fernandes, José R; Souto, Eliana B; Almeida, Paulo; Ferreira, Luis F Vieira; Reis, Lucinda V

2017-07-15

New unsymmetrical aminosquarylium cyanine dyes were synthesized and their potential as photosensitizers evaluated. New dyes, derived from benzothiazole and quinoline, were prepared by nucleophilic substitution of the corresponding O-methylated, the key intermediate that was obtained by methylation with CF 3 SO 3 CH 3 of the related zwitterionic unsymmetrical dye, with ammonia and methylamine, respectively. All three news dyes herein described displayed intense and narrow bands in the Vis/NIR region (693-714nm) and their singlet oxygen formation quantum yields ranged from 0.03 to 0.05. In vitro toxicity, in Caco-2 and HepG2 cells, indicated that dark toxicity was absent for concentrations up to 5µM (for the less active dye) or up to 1µM (for the two more active dyes). The three dyes present potential as photosensitizers, differing in irradiation conditions and period of incubation in the presence of irradiated dye. The less active dye needs a longer irradiation period to exhibit phototoxicity which is only evident after longer period of contact with cells (24h). However, the remaining two more active dyes produce higher phototoxicity, even at shorter incubation periods (1h), with shorter irradiation time (7min). Although in different extents, these dyes show promising in vitro results as photosensitizers. Copyright © 2017 Elsevier Ltd. All rights reserved.

The role of protein crystallography in defining the mechanisms of biogenesis and catalysis in copper amine oxidase.

PubMed

Klema, Valerie J; Wilmot, Carrie M

2012-01-01

Copper amine oxidases (CAOs) are a ubiquitous group of enzymes that catalyze the conversion of primary amines to aldehydes coupled to the reduction of O(2) to H(2)O(2). These enzymes utilize a wide range of substrates from methylamine to polypeptides. Changes in CAO activity are correlated with a variety of human diseases, including diabetes mellitus, Alzheimer's disease, and inflammatory disorders. CAOs contain a cofactor, 2,4,5-trihydroxyphenylalanine quinone (TPQ), that is required for catalytic activity and synthesized through the post-translational modification of a tyrosine residue within the CAO polypeptide. TPQ generation is a self-processing event only requiring the addition of oxygen and Cu(II) to the apoCAO. Thus, the CAO active site supports two very different reactions: TPQ synthesis, and the two electron oxidation of primary amines. Crystal structures are available from bacterial through to human sources, and have given insight into substrate preference, stereospecificity, and structural changes during biogenesis and catalysis. In particular both these processes have been studied in crystallo through the addition of native substrates. These latter studies enable intermediates during physiological turnover to be directly visualized, and demonstrate the power of this relatively recent development in protein crystallography.

Large unexplained suite of chemically reactive compounds present in ambient air due to biomass fires.

PubMed

Kumar, V; Chandra, B P; Sinha, V

2018-01-12

Biomass fires impact global atmospheric chemistry. The reactive compounds emitted and formed due to biomass fires drive ozone and organic aerosol formation, affecting both air quality and climate. Direct hydroxyl (OH) Reactivity measurements quantify total gaseous reactive pollutant loadings and comparison with measured compounds yields the fraction of unmeasured compounds. Here, we quantified the magnitude and composition of total OH reactivity in the north-west Indo-Gangetic Plain. More than 120% increase occurred in total OH reactivity (28 s -1 to 64 s -1 ) and from no missing OH reactivity in the normal summertime air, the missing OH reactivity fraction increased to ~40 % in the post-harvest summertime period influenced by large scale biomass fires highlighting presence of unmeasured compounds. Increased missing OH reactivity between the two summertime periods was associated with increased concentrations of compounds with strong photochemical source such as acetaldehyde, acetone, hydroxyacetone, nitromethane, amides, isocyanic acid and primary emissions of acetonitrile and aromatic compounds. Currently even the most detailed state-of-the art atmospheric chemistry models exclude formamide, acetamide, nitromethane and isocyanic acid and their highly reactive precursor alkylamines (e.g. methylamine, ethylamine, dimethylamine, trimethylamine). For improved understanding of atmospheric chemistry-air quality-climate feedbacks in biomass-fire impacted atmospheric environments, future studies should include these compounds.

Finite-Size Effects of Binary Mutual Diffusion Coefficients from Molecular Dynamics

PubMed Central

2018-01-01

Molecular dynamics simulations were performed for the prediction of the finite-size effects of Maxwell-Stefan diffusion coefficients of molecular mixtures and a wide variety of binary Lennard–Jones systems. A strong dependency of computed diffusivities on the system size was observed. Computed diffusivities were found to increase with the number of molecules. We propose a correction for the extrapolation of Maxwell–Stefan diffusion coefficients to the thermodynamic limit, based on the study by Yeh and Hummer (J. Phys. Chem. B, 2004, 108, 15873−15879). The proposed correction is a function of the viscosity of the system, the size of the simulation box, and the thermodynamic factor, which is a measure for the nonideality of the mixture. Verification is carried out for more than 200 distinct binary Lennard–Jones systems, as well as 9 binary systems of methanol, water, ethanol, acetone, methylamine, and carbon tetrachloride. Significant deviations between finite-size Maxwell–Stefan diffusivities and the corresponding diffusivities at the thermodynamic limit were found for mixtures close to demixing. In these cases, the finite-size correction can be even larger than the simulated (finite-size) Maxwell–Stefan diffusivity. Our results show that considering these finite-size effects is crucial and that the suggested correction allows for reliable computations. PMID:29664633

[Ketamine--dreams and realities].

PubMed

Arditti, J; Spadari, M; de Haro, L; Brun, A; Bourdon, J H; Valli, M

2002-01-01

Ketamine is an anaesthetic used in human medicine and veterinary practice, synthesised on 1962 and marketed on 1970 in France. Recreational uses were described during 1992 in the medical community and in 1996 in the dance settings. The chemical name of ketamine is 2--(2chlorophenyl)2-(methylamine)-cyclohexanone, an aryl cyclohexylamine, structurally related to phencyclidine. Ketamine is known under the following street names: Keta K, Kate, Special K, Vitamin K, la Golden, la Vétérinaire. Ketamine is used intranasally, orally and intramusculary in recreational use. Ketamine is manufactured by the chemical industry. Due to the complicated synthesis, it is sold illicitly for recreational use. Ketamine is a dissociative drug, and the user enters in a psychedelic dream with hallucinations, floating sensation, feeling of dissociation of the mind from the body. The dream is forgotten, the user full in reality with loss of self control, risk of acute intoxication. In long-term exposure, tolerance, dependence, withdrawal signs and flash back are described. Ketamine trademarks are subject to control in France through medicine legislation Ketamine and its salts are subject to control under the national legislation on narcotics and psychotropics substance. From September 2001, the theft of medical and veterinary trademarks have to be declared to police, care health authority Pharmacy control authority and French Health Products Safety Agency.

Evidence for a Na+/H+ Antiporter in Membrane Vesicles Isolated from Roots of the Halophyte Atriplex nummularia1

PubMed Central

Braun, Yael; Hassidim, Miriam; Lerner, Henri R.; Reinhold, Leonora

1988-01-01

The ATP-dependent establishment of a positive membrane potential (measured as S14CN−-accumulation) in membrane vesicles isolated from the roots of Atriplex nummularia Lindl. was not inhibited by NaMes and KMes at concentrations up to 140 millimolar. On the other hand, the formation of ΔpH (measured as 14C-methylamine accumulation or quenching of quinacrine fluorescence), was depressed by NaMes concentrations as low as 30 millimolar. Supply of NaMes after the ΔpH had been established brought about partial dissipation within 30 seconds. Extent of dissipation of ΔpH increased with NaMes concentration over the range tested (up to 180 millimolar). The H+/Na+ exchange indicated by these results was not due to the creation of a Na+ diffusion potential. Formation of ΔpH in these vesicles was stable to NO3− up to 100 millimolar; further, the dissipating effect of Na+ supply was apparent on a ΔpH formed in the presence of 30 millimolar NO3−. Additional evidence that the origin of the membrane vesicles observed in this investigation was not the tonoplast and was probably the plasmalemma included the vanadate sensitivity of the establishment of the membrane potential. PMID:16666082

Nitrogen-Containing, Light-Absorbing Oligomers Produced in Aerosol Particles Exposed to Methylglyoxal, Photolysis, and Cloud Cycling.

PubMed

De Haan, David O; Tapavicza, Enrico; Riva, Matthieu; Cui, Tianqu; Surratt, Jason D; Smith, Adam C; Jordan, Mary-Caitlin; Nilakantan, Shiva; Almodovar, Marisol; Stewart, Tiffany N; de Loera, Alexia; De Haan, Audrey C; Cazaunau, Mathieu; Gratien, Aline; Pangui, Edouard; Doussin, Jean-François

2018-04-03

Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon aerosol particles collected from cloud cycling/photolysis chamber experiments, where gaseous methylglyoxal and methylamine interacted with glycine, ammonium, or methylammonium sulfate seed particles. Eighteen N-containing oligomers were identified in the particulate phase by liquid chromatography/diode array detection/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry. Chemical formulas were determined and, for 6 major oligomer products, MS 2 fragmentation spectra were used to propose tentative structures and mechanisms. Electronic absorption spectra were calculated for six tentative product structures by an ab initio second order algebraic-diagrammatic-construction/density functional theory approach. For five structures, matching calculated and measured absorption spectra suggest that they are dominant light-absorbing species at their chromatographic retention times. Detected oligomers incorporated methylglyoxal and amines, as expected, but also pyruvic acid, hydroxyacetone, and significant quantities of acetaldehyde. The finding that ∼80% (by mass) of detected oligomers contained acetaldehyde, a methylglyoxal photolysis product, suggests that daytime methylglyoxal oligomer formation is dominated by radical addition mechanisms involving CH 3 CO*. These mechanisms are evidently responsible for enhanced browning observed during photolytic cloud events.

Brown carbon formation by aqueous-phase carbonyl compound reactions with amines and ammonium sulfate.

PubMed

Powelson, Michelle H; Espelien, Brenna M; Hawkins, Lelia N; Galloway, Melissa M; De Haan, David O

2014-01-21

Reactions between small water-soluble carbonyl compounds, ammonium sulfate (AS), and/or amines were evaluated for their ability to form light-absorbing species in aqueous aerosol. Aerosol chemistry was simulated with bulk phase reactions at pH 4, 275 K, initial concentrations of 0.05 to 0.25 M, and UV-vis and fluorescence spectroscopy monitoring. Glycolaldehyde-glycine mixtures produced the most intense absorbance. In carbonyl compound reactions with AS, methylamine, or AS/glycine mixtures, product absorbance followed the order methylglyoxal > glyoxal > glycolaldehyde > hydroxyacetone. Absorbance extended into the visible, with a wavelength dependence fit by absorption Ångstrom coefficients (Å(abs)) of 2 to 11, overlapping the Å(abs) range of atmospheric, water-soluble brown carbon. Many reaction products absorbing between 300 and 400 nm were strongly fluorescent. On a per mole basis, amines are much more effective than AS at producing brown carbon. In addition, methylglyoxal and glyoxal produced more light-absorbing products in reactions with a 5:1 AS-glycine mixture than with AS or glycine alone, illustrating the importance of both organic and inorganic nitrogen in brown carbon formation. Through comparison to biomass burning aerosol, we place an upper limit on the contribution of these aqueous carbonyl-AS-amine reactions of ≤ 10% of global light absorption by brown carbon.

The Role of Protein Crystallography in Defining the Mechanisms of Biogenesis and Catalysis in Copper Amine Oxidase

PubMed Central

Klema, Valerie J.; Wilmot, Carrie M.

2012-01-01

Copper amine oxidases (CAOs) are a ubiquitous group of enzymes that catalyze the conversion of primary amines to aldehydes coupled to the reduction of O2 to H2O2. These enzymes utilize a wide range of substrates from methylamine to polypeptides. Changes in CAO activity are correlated with a variety of human diseases, including diabetes mellitus, Alzheimer’s disease, and inflammatory disorders. CAOs contain a cofactor, 2,4,5-trihydroxyphenylalanine quinone (TPQ), that is required for catalytic activity and synthesized through the post-translational modification of a tyrosine residue within the CAO polypeptide. TPQ generation is a self-processing event only requiring the addition of oxygen and Cu(II) to the apoCAO. Thus, the CAO active site supports two very different reactions: TPQ synthesis, and the two electron oxidation of primary amines. Crystal structures are available from bacterial through to human sources, and have given insight into substrate preference, stereospecificity, and structural changes during biogenesis and catalysis. In particular both these processes have been studied in crystallo through the addition of native substrates. These latter studies enable intermediates during physiological turnover to be directly visualized, and demonstrate the power of this relatively recent development in protein crystallography. PMID:22754303

Mechanism of the Antimicrobial Action of Pyrithione: Effects on Membrane Transport, ATP Levels, and Protein Synthesis

PubMed Central

Chandler, Carol J.; Segel, Irwin H.

1978-01-01

Pyrithione is a general inhibitor of membrane transport processes in fungi. A brief preincubation of Penicillium mycelia with pyrithione resulted in a marked decrease in the activities of a variety of independently regulated transport systems, including those for inorganic sulfate, inorganic phosphate, methylamine (actually, the NH4+ permease), choline-O-sulfate, glucose, l-methionine (a specific system), and several hydrophobic l-α-amino acids (the general amino acid permease). The degree of inhibition at any fixed pyrithione concentration and exposure time increased as the pH of the incubation medium was decreased. This result strongly suggests that the active species is the un-ionized molecule and that pyrithione acts by collapsing a transmembrane ΔpH driving force. The degree of transport inhibition caused by a given concentration of pyrithione increased with increasing time of exposure to the inhibitor. However, exposure time and pyrithione concentration were not reciprocally related. At “low” pyrithione concentrations, transport inhibition plateaued at some finite value. This observation suggests that the fungi can detoxify low levels of the inhibitor. The concentration of pyrithione required for a given degree of growth inhibition increased as the experimental mycelial density increased. This phenomenon was consistent with the suggestion that the fungi are capable of inactivating pyrithione. PMID:28693

Towards understanding the role of amines in the SO2 hydration and the contribution of the hydrated product to new particle formation in the Earth's atmosphere.

PubMed

Lv, Guochun; Nadykto, Alexey B; Sun, Xiaomin; Zhang, Chenxi; Xu, Yisheng

2018-08-01

By theoretical calculations, the gas-phase SO 2 hydration reaction assisted by methylamine (MA) and dimethylamine (DMA) was investigated, and the potential contribution of the hydrated product to new particle formation (NPF) also was evaluated. The results show that the energy barrier for aliphatic amines (MA and DMA) assisted SO 2 hydration reaction is lower than the corresponding that of water and ammonia assisted SO 2 hydration. In these hydration reactions, nearly barrierless reaction (only a barrier of 0.1 kcal mol -1 ) can be found in the case of SO 2  + 2H 2 O + DMA. These lead us to conclude that the SO 2 hydration reaction assisted by MA and DMA is energetically facile. The temporal evolution for hydrated products (CH 3 NH 3 + -HSO 3 - -H 2 O or (CH 3 ) 2 NH 2 + -HSO 3 - -H 2 O) in molecular dynamics simulations indicates that these complexes can self-aggregate into bigger clusters and can absorb water and amine molecules, which means that these hydrated products formed by the hydration reaction may serve as a condensation nucleus to initiate the NPF. Copyright © 2018 Elsevier Ltd. All rights reserved.

Lipid and cationic polymer based transduction of botulinum holotoxin, or toxin protease alone, extends the target cell range and improves the efficiency of intoxication.

PubMed

Kuo, Chueh-Ling; Oyler, George; Shoemaker, Charles B

2010-01-01

Botulinum neurotoxin (BoNT) heavy chain (Hc) facilitates receptor-mediated endocytosis into neuronal cells and transport of the light chain (Lc) protease to the cytosol where neurotransmission is inhibited as a result of SNARE protein cleavage. Here we show that the role of BoNT Hc in cell intoxication can be replaced by commercial lipid-based and polycationic polymer DNA transfection reagents. BoNT "transduction" by these reagents permits efficient intoxication of neuronal cells as well as some non-neuronal cell lines normally refractory to BoNT. Surprisingly, the reagents facilitate delivery of recombinant BoNT Lc protease to the cytosol of both neuronal and non-neuronal cells in the absence of BoNT Hc, and with sensitivities approaching that of BoNT holotoxin. Transduction of BoNT, as with natural intoxication, is inhibited by bafilomycin A1, methylamine and ammonium chloride indicating that both pathways require endosome acidification. DNA transfection reagents facilitate intoxication by holotoxins, or isolated Lc proteases, of all three BoNT serotypes tested (A, B, E). These results suggest that lipid and cationic polymer transfection reagents facilitate cytosolic delivery of BoNT holotoxins and isolated Lc proteases by an endosomal uptake pathway.

Down-modulation of receptors for phorbol ester tumor promoter in primary epidermal cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solanki, V.; Slaga, T.J.

1982-01-01

The specific (20-/sup 3/H)phorbol 12,13-dibutyrate ((/sup 3/H)PDBu) binding to intact epidermal cells displayed the phenomenon of down-modulation, i.e., the specific binding of (/sup 3/H)PDBu to its receptors on primary epidermal cells reached a maximum within 1 h and steadily declined thereafter. The apparent down-modulation of radiolabel resulted from a partial loss in the total number of receptors; the affinity of receptors for the ligand was essentially unchanged. A number of agents such as chloroquine, methylamine, or arginine which are known to prevent clustering, down-modulation, and/or internalization of several hormone receptors did not affect the down-modulation of phorbol ester receptors. Furthermore,more » cycloheximide had no effect either on down-modulation or on the binding capacity of cells. The surface binding capacity of down-modulated cells following a 90-min incubation with unlabeled ligand was almost returned to normal within 1 h. The effect of the antidepressant drug chlorpromazine, which is known to interact with calmodulin, on (/sup 3/H)PDBu binding was also investigated. Our data indicate that the effect of chlorpromazine on (/sup 3/H)PDBu binding is probably unrelated to its calmodulin-binding activity.« less

Photochemical attenuation of N-nitrosodimethylamine (NDMA) and other nitrosamines in surface water.

PubMed

Plumlee, Megan H; Reinhard, Martin

2007-09-01

The aqueous photolysis of seven alkyl nitrosamines was studied by irradiation in a solar simulator. Nitrosamines included N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA), N-nitrosopiperidine (NPip), and N-nitrosopyrrolidine (NPyr). Direct photolysis at irradiations of 765 W/m2, representing Southern California midsummer, midday sun, resulted in half-lives of 16 min for NDMA and 12-15 min for the other nitrosamines. The quantum yield for NDMA was determined to be phi = 0.41 and phi = 0.43-0.61 for the other nitrosamines. Quantified products of NDMA photolysis included methylamine, dimethylamine, nitrite, nitrate, and formate, with nitrogen and carbon balances exceeding 98 and 79%, respectively. Indirect photolysis of nitrosamines in surface water was not observed; increasing dissolved organic carbon (DOC) slowed the NDMA photolysis rate because of light screening. Removal of NDMA measured in tertiary treated effluent flowing in a shallow, sunlit engineered channel agreed with photolysis rates predicted based on the measured quantum yield and system parameters. Because biodegradation is relatively slow, aquatic photolysis of NDMA is generally expected to be more significant even at relatively low levels of solar irradiation (t(1/2) = 8-38 h at 244-855 W/m2, 51 degrees N latitude, 1 m depth).

Generation of an endogenous DNA-methylating agent by nitrosation in Escherichia coli.

PubMed Central

Taverna, P; Sedgwick, B

1996-01-01

Escherichia coli ada ogt mutants, which are totally deficient in O6-methylguanine-DNA methyltransferases, have an increased spontaneous mutation rate. This phenotype is particularly evident in starving cells and suggests the generation of an endogenous DNA alkylating agent under this growth condition. We have found that in wild-type cells, the level of the inducible Ada protein is 20-fold higher in stationary-phase and starving cells than in rapidly growing cells, thus enhancing the defense of these cells against DNA damage. The increased level of Ada in stationary cells is dependent on RpoS, a stationary-phase-specific sigma subunit of RNA polymerase. We have also identified a potential source of the mutagenic agent. Nitrosation of amides and related compounds can generate directly acting methylating agents and can be catalyzed by bacteria] enzymes. E. coli moa mutants, which are defective in the synthesis of a molybdopterin cofactor required by several reductases, are deficient in nitrosation activity. It is reported here that a moa mutant shows reduced generation of a mutagenic methylating agent from methylamine (or methylurea) and nitrite added to agar plates. Moreover, a moa mutation eliminates much of the spontaneous mutagenesis in ada ogt mutants. These observations indicate that the major endogenous mutagen is not S-adenosylmethionine but arises by bacterially catalyzed nitrosation. PMID:8752326

Methylopila helvetica sp. nov. and Methylobacterium dichloromethanicum sp. nov.--novel aerobic facultatively methylotrophic bacteria utilizing dichloromethane.

PubMed

Doronina, N V; Trotsenko, Y A; Tourova, T P; Kuznetsov, B B; Leisinger, T

2000-06-01

Eight strains of Gram-negative, aerobic, asporogenous, neutrophilic, mesophilic, facultatively methylotrophic bacteria are taxonomically described. These icl- serine pathway methylobacteria utilize dichloromethane, methanol and methylamine as well as a variety of polycarbon compounds as the carbon and energy source. The major cellular fatty acids of the non-pigmented strains DM1, DM3, and DM5 to DM9 are C18:1, C16:0, C18:0, Ccy19:0 and that of the pink-pigmented strain DM4 is C18:1. The main quinone of all the strains is Q-10. The non-pigmented strains have similar phenotypic properties and a high level of DNA-DNA relatedness (81-98%) as determined by hybridization. All strains belong to the alpha-subgroup of the alpha-Proteobacteria. 16S rDNA sequence analysis led to the classification of these dichloromethane-utilizers in the genus Methylopila as a new species - Methylopila helvetica sp.nov. with the type strain DM9 (=VKM B-2189). The pink-pigmented strain DM4 belongs to the genus Methylobacterium but differs from the known members of this genus by some phenotypic properties, DNA-DNA relatedness (14-57%) and 16S rDNA sequence. Strain DM4 is named Methylobacterium dichloromethanicum sp. nov. (VKM B-2191 = DSMZ 6343).

Impacts of Future European Emission Reductions on Aerosol Particle Number Concentrations Accounting for Effects of Ammonia, Amines, and Organic Species.

PubMed

Julin, Jan; Murphy, Benjamin N; Patoulias, David; Fountoukis, Christos; Olenius, Tinja; Pandis, Spyros N; Riipinen, Ilona

2018-01-16

Although they are currently unregulated, atmospheric ultrafine particles (<100 nm) pose health risks because of, e.g., their capability to penetrate deep into the respiratory system. Ultrafine particles, often minor contributors to atmospheric particulate mass, typically dominate aerosol particle number concentrations. We simulated the response of particle number concentrations over Europe to recent estimates of future emission reductions of aerosol particles and their precursors. We used the chemical transport model PMCAMx-UF, with novel updates including state-of-the-art descriptions of ammonia and dimethylamine new particle formation (NPF) pathways and the condensation of organic compounds onto particles. These processes had notable impacts on atmospheric particle number concentrations. All three emission scenarios (current legislation, optimized emissions, and maximum technically feasible reductions) resulted in substantial (10-50%) decreases in median particle number concentrations over Europe. Consistent reductions were predicted in Central Europe, while Northern Europe exhibited smaller reductions or even increased concentrations. Motivated by the improved NPF descriptions for ammonia and methylamines, we placed special focus on the potential to improve air quality by reducing agricultural emissions, which are a major source of these species. Agricultural emission controls showed promise in reducing ultrafine particle number concentrations, although the change is nonlinear with particle size.

Lipid and cationic polymer based transduction of botulinum holotoxin, or toxin protease alone, extends the target cell range and improves the efficiency of intoxication

PubMed Central

Kuo, Chueh-Ling; Oyler, George; Shoemaker, Charles B.

2009-01-01

Botulinum neurotoxin (BoNT) heavy chain (Hc) facilitates receptor-mediated endocytosis into neuronal cells and transport of the light chain (Lc) protease to the cytosol where neurotransmission is inhibited as a result of SNARE protein cleavage. Here we show that the role of BoNT Hc in cell intoxication can be replaced by commercial lipid-based and polycationic polymer DNA transfection reagents. BoNT “transduction” by these reagents permits efficient intoxication of neuronal cells as well as some non-neuronal cell lines normally refractory to BoNT. Surprisingly, the reagents facilitate delivery of recombinant BoNT Lc protease to the cytosol of both neuronal and non-neuronal cells in the absence of BoNT Hc, and with sensitivities approaching that of BoNT holotoxin. Transduction of BoNT, as with natural intoxication, is inhibited by bafilomycin A1, methylamine and ammonium chloride indicating that both pathways require endosome acidification. DNA transfection reagents facilitate intoxication by holotoxins, or isolated Lc proteases, of all three BoNT serotypes tested (A, B, E). These results suggest that lipid and cationic polymer transfection reagents facilitate cytosolic delivery of BoNT holotoxins and isolated Lc proteases by an endosomal uptake pathway. PMID:19852976

Human health risk assessment of nitrosamines and nitramines for potential application in CO2 capture.

PubMed

Ravnum, S; Rundén-Pran, E; Fjellsbø, L M; Dusinska, M

2014-07-01

Emission and accumulation of carbon dioxide (CO2) in the atmosphere exert an environmental and climate change challenge. An attempt to deal with this challenge is made at Mongstad by application of amines for CO2 capture and storage (CO2 capture Mongstad (CCM) project). As part of the CO2 capture process, nitrosamines and nitramines may be emitted. Toxicological testing of nitrosamines and nitramines indicate a genotoxic potential of these substances. Here we present a risk characterization and assessment for five nitrosamines (N-Nitrosodi-methylamine (NDMA) N-Nitrosodi-ethylamine (NDEA), N-Nitroso-morpholine (NNM), N-Nitroso-piperidine (NPIP), and Dinitroso-piperazine (DNP)) and two nitramines (N-Methyl-nitramine (NTMA), Dimethyl-nitramine (NDTMA)), which are potentially emitted from the CO2 capture plant (CCP). Human health risk assessment of genotoxic non-threshold substances is a heavily debated topic, and no consensus methodology exists internationally. Extrapolation modeling from high-dose animal exposures to low-dose human exposures can be crucial for the final risk calculation. In the work presented here, different extrapolation models are discussed, and suggestions on applications are given. Then, preferred methods for calculating derived minimal effect level (DMEL) are presented with the selected nitrosamines and nitramines. Copyright © 2014 Elsevier Inc. All rights reserved.

Angiotensin II promotes iron accumulation and depresses PGI₂ and NO synthesis in endothelial cells: effects of losartan and propranolol analogs.

PubMed

Mak, I Tong; Landgraf, Kenneth M; Chmielinska, Joanna J; Weglicki, William B

2012-10-01

Angiotensin may promote endothelial dysfunction through iron accumulation. To research this, bovine endothelial cells (ECs) were incubated with iron (30 µmol·L⁻¹) with or without angiotensin II (100 nmol·L⁻¹). After incubation for 6 h, it was observed that the addition of angiotensin enhanced EC iron accumulation by 5.1-fold compared with a 1.8-fold increase for cells incubated with iron only. This enhanced iron uptake was attenuated by losartan (100 nmol·L⁻¹), d-propranolol (10 µmol·L⁻¹), 4-HO-propranolol (5 µmol·L⁻¹), and methylamine, but not by vitamin E or atenolol. After 6 h of incubation, angiotensin plus iron provoked intracellular oxidant formation (2'7'-dichlorofluorescein diacetate (DCF-DA) fluorescence) and elevated oxidized glutathione; significant loss of cell viability occurred at 48 h. Stimulated prostacyclin release decreased by 38% (6 h) and NO synthesis was reduced by 41% (24 h). Both oxidative events and functional impairment were substantially attenuated by losartan or d-propranolol. It is concluded that angiotensin promoted non-transferrin-bound iron uptake via AT-1 receptor activation, leading to EC oxidative functional impairment. The protective effects of d-propranolol and 4-HO-propranolol may be related to their lysosomotropic properties.

Molecules coating magnetic nanoparticles for oil-field applications

NASA Astrophysics Data System (ADS)

Zuluaga, Sebastian; Manchanda, Priyanka; Pantelides, Sokrates

Magnetic nanoparticles have recently attracted significant attention in scientific and industrial communities due to their use in the fields of catalysis, spintronics, biomedical applications, and oil recovery and reservoir characterization. However, these nanoparticles have to be protected with a coating layer of molecules that prevents the nanoparticles from oxidation, which is known to occur in air, and from agglomeration into larger nanoparticles. Therefore, the binding of the molecules to the nanoparticles is critical before a large scale implementation can be done. Here we report results of density functional theory calculations on several molecules (methylamine, acetic acid, boronic acid, ethyl phosphate, and ethyl trihydroxysilane) and magnetic nanoparticles (Fe3O4, NiFe2O4, and Fe3C). We focus on two main points: 1) the bond strength between the organic molecule and the nano particle, and 2) how, H2O and H+ in the oil well may facilitate the desorption of the molecules. The results show that H+ and H2O molecules facilitate the desorption of molecules reducing the bond strength by several eV. On the other hand, the results allow us to identify and design molecules that exhibit the best performance in protecting each nanoparticle. Supported by a Grant from the Petroleum Institute, Abu Dhabi.

Effects of inorganic phosphate on the light dependent thylakoid energization of intact spinach chloroplasts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heineke, D.; Heldt, H.W.; Stitt, M.

1989-09-01

The light dependent energization of the thylakoid membrane was analyzed in isolated intact spinach (Spinacia oleracea L.) chloroplasts incubated with different concentrations of inorganic phosphate (Pi). Two independent methods were used: (a) the accumulation of ({sup 14}C)5,5-dimethyl-2,4-oxazolidinedione and ({sup 14}C)methylamine; (b) the energy dependent chlorophyll fluorescence quenching. The inhibition of CO{sub 2} fixation by superoptimal medium Pi or by adding glyceraldehyde - an inhibitor of the Calvin cycle - leads to an increased energization of the thylakoid membrane; however, the membrane energization decreases when chloroplasts are inhibited by suboptimal Pi. This specific low phosphate effect could be partially reversed bymore » adding oxaloacetate, which regenerates the electron acceptor NADP{sup +} and stimulates linear electron transport. The energization seen in low Pi is, however, always lower than in superoptimal Pi, even in the presence of oxaloacetate. Energization recovers in the presence of low amounts of N,N{prime}-dicyclohexylcarbodiimide, which reacts with proton channels including the coupling factor 1 ATP synthase. N,N{prime}-Dicyclohexylcarbodiimide has no effect on energization of chloroplasts in superoptimal Pi. These results suggest there is a specific low phosphate proton leak in the thylakoids, and its origin is discussed.« less

Gas-phase fragmentation of coordination compounds: loss of CO(2) from inorganic carbonato complexes to give metal oxide ions

PubMed

Dalgaard; McKenzie

1999-10-01

Using electrospray ionization mass spectrometry, novel transition metal oxide coordination complex ions are proposed as the products of the collision-induced dissociation (CID) of some carbonato complex ions through the loss of a mass equivalent to CO(2). CID spectra of [(tpa)CoCO(3)](+) (tpa = tris(2-pyridylmethyl)methylamine), [(bispicMe(2)en)Fe(&mgr;-O)(&mgr;-CO(3))Fe(bispicMe(2)en)]2+ (bispicMe(2)en = N,N'-dimethyl-N,N'-bis(2-pyridylmethy)eth- ane-1, 2-diamine) and [(bpbp)Cu(2)CO(3)](+) (bpbp(-) = bis[(bis-(2-pyridylmethyl)amino)methyl]-4-tertbutylpheno-lato(1-)), show peaks assigned to the mono- and dinuclear oxide cations, [(tpa)CoO](+), [(bispicMe(2)en)(2)Fe(2)(O)(2)]2+ and [(bpbp)Cu(2)O](+), as the dominant species. These results can be likened to the reverse of typical synthetic reactions in which metal hydroxide compounds react with CO(2) to give metal carbonato compounds. Because of the lack of available protons in the gas phase, novel oxide species rather than the more common hydroxide ions are generated. These oxide ions are relevant to the highly oxidizing species proposed in oxygenation reactions catalysed by metal oxides and metalloenzymes. Copyright 1999 John Wiley & Sons, Ltd.

PF 9601N [N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine], a new MAO-B inhibitor, attenuates MPTP-induced depletion of striatal dopamine levels in C57/BL6 mice.

PubMed

Perez, Virgili; Unzeta, Mercedes

2003-02-01

Monoamine oxidase isoform B (MAO-B) is involved in Parkinson's disease (PD) induced by the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxin (MPTP) in human and non-human-primate. MAO-B inhibitors, such as L-deprenyl have shown to prevent against MPTP-toxicity in different species, and it has been used in Parkinson therapy, however, the fact that it is metabolized to (-)-methamphetamine and (-)-amphetamine highlights the need to find out new MAO-B inhibitors without a structural amphetaminic moiety. In this context we herein report, for the first time, anywhere a novel non-amphetamine-like MAO-B inhibitor, PF 9601N, N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine. This attenuates the MPTP-induced striatal dopamine depletion in young-adult and adult-old C57/BL mice, using different schedules of administration, and which behave "ex vivo" as a slightly more potent and selective MAO-B inhibitor than L-deprenyl, assayed for comparative purposes in the same experimental conditions. The MAO-B ID(50) values were calculated from the total MAO-B activity measured against [14C] phenylethylamine (22 microM) as substrate, at each inhibitor concentration. The MAO-B ID(50) values resulted to be 381 and 577 nmol/kg for PF 9601N and L-deprenyl, respectively. The intraperitoneally (i.p.) co-administration to young-adult C57/BL6 mice of MPTP (30 mg/kg), with different concentrations of PF 9601N or L-deprenyl (29.5-0.357 micromol/kg) showed a dose-dependent protective effect against striatal dopamine depletion, measuring the dopamine contents and its metabolites by HPLC. The ED(50) value proved to be 3.07 micromol/kg without any significant differences between either MAO-B inhibitor. Nevertheless, lower doses of PF 9601N (1.5 micromol/kg) were necessary to get almost total protection, without any change in the DOPAC and HVA content, when administered 2 h before MPTP (30 mg/kg), whereas partial protection (45%) against dopamine depletion was observed in the case of L-deprenyl. In both cases, MAO-B inhibition was a necessary condition in order to observe the protective effect. When adult-old (8-10 months) C57/BL6 mice were used, MPTP (25 mg/kg) administration induced 25 days later, an irreversible dopamine depletion. In these conditions, chronic administration with 0.15 micromol/kg of PF 9601N, before the toxin, every 24 h for 10 days, rendered almost total protection of dopamine depletion, whereas L-deprenyl yielded only 50% protection of the dopamine content, assayed in the same conditions. It is worth remarking, that in both cases MAO-B was not affected. From these results, it can be concluded that PF 9601N attenuates MPTP neurotoxicity "in vivo" better than L-deprenyl through different mechanisms, with special relevance to the protective effect, independent of MAO-B inhibition, observed in the irreversibly MPTP-lesioned adult-old mice. Therefore, this novel non-amphetamine MAO-B inhibitor could be potentially effective in PD therapy. Copyright 2003 Elsevier Science Ltd.

Methanogenic activity and diversity in the centre of the Amsterdam Mud Volcano, Eastern Mediterranean Sea.

PubMed

Lazar, Cassandre Sara; John Parkes, R; Cragg, Barry A; L'Haridon, Stephane; Toffin, Laurent

2012-07-01

Marine mud volcanoes are geological structures emitting large amounts of methane from their active centres. The Amsterdam mud volcano (AMV), located in the Anaximander Mountains south of Turkey, is characterized by intense active methane seepage produced in part by methanogens. To date, information about the diversity or the metabolic pathways used by the methanogens in active centres of marine mud volcanoes is limited. (14)C-radiotracer measurements showed that methylamines/methanol, H(2)/CO(2) and acetate were used for methanogenesis in the AMV. Methylotrophic methanogenesis was measured all along the sediment core, Methanosarcinales affiliated sequences were detected using archaeal 16S PCR-DGGE and mcrA gene libraries, and enrichments of methanogens showed the presence of Methanococcoides in the shallow sediment layers. Overall acetoclastic methanogenesis was higher than hydrogenotrophic methanogenesis, which is unusual for cold seep sediments. Interestingly, acetate porewater concentrations were extremely high in the AMV sediments. This might be the result of organic matter cracking in deeper hotter sediment layers. Methane was also produced from hexadecanes. For the most part, the methanogenic community diversity was in accordance with the depth distribution of the H(2)/CO(2) and acetate methanogenesis. These results demonstrate the importance of methanogenic communities in the centres of marine mud volcanoes. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Dietary protein deficiency reduces lysosomal and nonlysosomal ATP-dependent proteolysis in muscle

NASA Technical Reports Server (NTRS)

Tawa, N. E. Jr; Kettelhut, I. C.; Goldberg, A. L.

1992-01-01

When rats are fed a protein deficient (PD) diet for 7 days, rates of proteolysis in skeletal muscle decrease by 40-50% (N. E. Tawa, Jr., and A. L. Goldberg. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E317-325, 1992). To identify the underlying biochemical adaptations, we measured different proteolytic processes in incubated muscles. The capacity for intralysosomal proteolysis, as shown by sensitivity to methylamine or lysosomal protease inhibitors, fell 55-75% in muscles from PD rats. Furthermore, extracts of muscles of PD rats showed 30-70% lower activity of many lysosomal proteases, including cathepsins B, H, and C, and carboxypeptidases A and C, as well as other lysosomal hydrolases. The fall in cathepsin B and proteolysis was evident by 3 days on the PD diet, and both returned to control levels 3 days after refeeding of the normal diet. In muscles maintained under optimal conditions, 80-90% of protein breakdown occurs by nonlysosomal pathways. In muscles of PD rats, this ATP-dependent process was also 40-60% slower. Even though overall proteolysis decreased in muscles of PD rats, their capacity for Ca(2+)-dependent proteolysis increased (by 66%), as did the activity of the calpains (+150-250%). Thus the lysosomal and the ATP-dependent processes decrease coordinately and contribute to the fall in muscle proteolysis in PD animals.

Factors influencing uptake and retention of amino-containing drugs in large unilamellar vesicles exhibiting transmembrane pH gradients.

PubMed

Maurer-Spurej, E; Wong, K F; Maurer, N; Fenske, D B; Cullis, P R

1999-01-12

The level of uptake and retention of amino-containing drugs in large unilamellar vesicles (LUVs) following uptake in response to a transmembrane pH gradient (DeltapH) can vary dramatically depending on the drug. For example, the anticancer drugs doxorubicin and epirubicin can be readily retained, whereas the anticancer drug vincristine and the antibiotic ciprofloxacin tend to leak out rapidly. In this investigation, we examine the influence of the hydrophobicity of the entrapped amines (that induce the DeltapH) and the anionic lipid content of the LUV on drug retention. It is shown that entrapment of increasingly hydrophobic monoamines (methylamine to amylamine) all lead to an induced DeltapH of 3 units and essentially complete drug uptake under the conditions employed, but do not lead to improved retention of vincristine and ciprofloxacin. However, significantly improved retention could be achieved by substitution of the anionic lipid distearoylphosphatidylglycerol (DSPG) for distearoylphosphatidylcholine (DSPC) in the LUV bilayer. Further, it is shown that if the induced DeltapH is reduced to 1.4 units (driven by entrapped diamine) nearly 100% accumulation of doxorubicin and epirubicin could be achieved, whereas only 25% loading for vincristine and ciprofloxacin was observed. Taken together these results provide methodology for improving (weak base) drug retention in liposomes and indicate that drugs that can partition into the lipid bilayer exhibit improved uptake and retention characteristics.

Brown Carbon Production in Ammonium- or Amine-Containing Aerosol Particles by Reactive Uptake of Methylglyoxal and Photolytic Cloud Cycling.

PubMed

De Haan, David O; Hawkins, Lelia N; Welsh, Hannah G; Pednekar, Raunak; Casar, Jason R; Pennington, Elyse A; de Loera, Alexia; Jimenez, Natalie G; Symons, Michael A; Zauscher, Melanie; Pajunoja, Aki; Caponi, Lorenzo; Cazaunau, Mathieu; Formenti, Paola; Gratien, Aline; Pangui, Edouard; Doussin, Jean-François

2017-07-05

The effects of methylglyoxal uptake on the physical and optical properties of aerosol containing amines or ammonium sulfate were determined before and after cloud processing in a temperature- and RH-controlled chamber. The formation of brown carbon was observed upon methylglyoxal addition, detected as an increase in water-soluble organic carbon mass absorption coefficients below 370 nm and as a drop in single-scattering albedo at 450 nm. The imaginary refractive index component k 450 reached a maximum value of 0.03 ± 0.009 with aqueous glycine aerosol particles. Browning of solid particles occurred at rates limited by chamber mixing (<1 min), and in liquid particles occurred more gradually, but in all cases occurred much more rapidly than in bulk aqueous studies. Further browning in AS and methylammonium sulfate seeds was triggered by cloud events with chamber lights on, suggesting photosensitized brown carbon formation. Despite these changes in optical aerosol characteristics, increases in dried aerosol mass were rarely observed (<1 μg/m 3 in all cases), consistent with previous experiments on methylglyoxal. Under dry, particle-free conditions, methylglyoxal reacted (presumably on chamber walls) with methylamine with a rate constant k = (9 ± 2) × 10 -17 cm 3 molecule -1 s -1 at 294 K and activation energy E a = 64 ± 37 kJ/mol.

Umbilical choline and related methylamines betaine and dimethylglycine in relation to birth weight.

PubMed

Hogeveen, Marije; den Heijer, Martin; Semmekrot, Ben A; Sporken, Jan M; Ueland, Per M; Blom, Henk J

2013-06-01

Low birth weight (LBW) is associated with increased morbidity and mortality for the newborn and risk of chronic disease in adulthood. Choline plays an essential role in the integrity of cell membranes, methylation reactions, and memory development. We examined whether choline, betaine, and dimethylglycine (DMG) concentrations were associated with LBW in Dutch women. Blood was sampled from umbilical cords (UCs) at delivery in singleton pregnancies (n = 1,126). Maternal blood was sampled at 30-34 wk of gestational age (GA) (n = 366). We calculated birth weights standardized for GA and defined LBW as standardized birth weight ≤ 2,500 g. Maternal concentrations were lower as compared with UC concentrations and were not associated with birth weight. UC choline and betaine were inversely associated with birth weight (β = -60 (-89, -31) and β = -65 (-94, -36), respectively), whereas UC DMG was positively associated with birth weight (β = 35 (6.1, 63)). Odds ratios for LBW were 4.12 (1.15, 14.78), 5.68 (1.24, 25.91), and 0.48 (0.09, 2.65) for the highest UC choline, betaine, and DMG quartiles, respectively, as compared with the lowest quartiles. We observed an increased risk of LBW with increased umbilical choline and betaine in venous UC blood. These results might reflect a change in choline consumption or metabolism or a disturbed placental function.

Amine content of vaginal fluid from untreated and treated patients with nonspecific vaginitis.

PubMed Central

Chen, K C; Forsyth, P S; Buchanan, T M; Holmes, K K

1979-01-01

We examined the vaginal washings from patients with nonspecific vaginitis (NSV) to seek biochemical markers and possible explanations for the signs and symptoms of this syndrome. Seven amines were identified including methylamine, isobutylamine, putrescine, cadaverine, histamine, tyramine, and phenethylamine. These amines may contribute to the symptoms of NSV and may contribute to the elevated pH of the vaginal discharge. They may also be partly responsible for the "fishy" odor that is characteristic of vaginal discharges from these patients. Among the seven amines, putrescine and cadaverine were the most abundant and were present in all vaginal discharges from each of ten patients before treatment. These amines are produced in vitro during growth of mixed vaginal bacteria in chemically defined medium, presumably by decarboxylation of the corresponding amino acids. We hypothesize the anaerobic vaginal organisms, previously shown to be quantitatively increased in NSV, are responsible for the amine production, because metronidazole inhibited the production of amines by vaginal bacteria in vitro, and Haemophilus vaginalis did not produce amines. H. vaginalis did release high concentrations of pyruvic acid and of amino acids during growth in peptone-starch-dextrose medium, whereas, other vaginal flora consumed both pyruvic acid and amino acids in the same medium during growth. These findings suggest that a symbiotic relationship may exist between H. vaginalis and other vaginal flora in patients with NSV. Images PMID:447831

On the theory of time dilation in chemical kinetics

NASA Astrophysics Data System (ADS)

Baig, Mirza Wasif

2017-10-01

The rates of chemical reactions are not absolute but their magnitude depends upon the relative speeds of the moving observers. This has been proved by unifying basic theories of chemical kinetics, which are transition state theory, collision theory, RRKM and Marcus theory, with the special theory of relativity. Boltzmann constant and energy spacing between permitted quantum levels of molecules are quantum mechanically proved to be Lorentz variant. The relativistic statistical thermodynamics has been developed to explain quasi-equilibrium existing between reactants and activated complex. The newly formulated Lorentz transformation of the rate constant from Arrhenius equation, of the collision frequency and of the Eyring and Marcus equations renders the rate of reaction to be Lorentz variant. For a moving observer moving at fractions of the speed of light along the reaction coordinate, the transition state possess less kinetic energy to sweep translation over it. This results in the slower transformation of reactants into products and in a stretched time frame for the chemical reaction to complete. Lorentz transformation of the half-life equation explains time dilation of the half-life period of chemical reactions and proves special theory of relativity and presents theory in accord with each other. To demonstrate the effectiveness of the present theory, the enzymatic reaction of methylamine dehydrogenase and radioactive disintegration of Astatine into Bismuth are considered as numerical examples.

Hydrothermal Synthesis of TiO2 Porous Hollow Nanospheres for Coating on the Photoelectrode of Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Madhu Mohan, Varishetty; Murakami, Kenji

2012-02-01

Various sizes of TiO2 hollow nanosphers were synthesized by a hydrolysis followed by the hydrothermal treatment using different water content and titanium isopropoxide (TTIP) while the remaining components such as methylamine, ethanol and acetonitrile were kept as a constant. We synthesized the various sizes of spheres, 150, 250, 400, 450, and 600 nm in diameter; those are represented as SP150, SP250, SP400, SP450, and SP600. The prepared spheres diameters were confirmed by scanning electron microscopy (SEM). These spheres were coated by using a simple spray technique with the TiO2 colloidal solution as a scattering layer for the TiO2 photoelectrode of dye-sensitized solar cells. Optical absorption measurements did not find a difference in the dye adsorption amount with and without the scattering layer. The scattering effect was observed by incident photon to current conversion efficiency (IPCE) measurements especially in the wavelength region of 550-700 nm. The current-voltage (I-V) measurements show that the scattering layer with 450 nm spheres coated on the photoelectrode gave the improved photovoltaic performances compared to other diameters of the spheres. In the present study, the best energy conversion efficiency of 9.56% was obtained for the photoelectrode with the scattering layer, while the pure photoelectrode without the layer gave 8.4%.

Metabolomic profiling of urinary changes in mice with monosodium glutamate-induced obesity.

PubMed

Pelantová, Helena; Bártová, Simona; Anýž, Jiří; Holubová, Martina; Železná, Blanka; Maletínská, Lenka; Novák, Daniel; Lacinová, Zdena; Šulc, Miroslav; Haluzík, Martin; Kuzma, Marek

2016-01-01

Obesity with related complications represents a widespread health problem. The etiopathogenesis of obesity is often studied using numerous rodent models. The mouse model of monosodium glutamate (MSG)-induced obesity was exploited as a model of obesity combined with insulin resistance. The aim of this work was to characterize the metabolic status of MSG mice by NMR-based metabolomics in combination with relevant biochemical and hormonal parameters. NMR analysis of urine at 2, 6, and 9 months revealed altered metabolism of nicotinamide and polyamines, attenuated excretion of major urinary proteins, increased levels of phenylacetylglycine and allantoin, and decreased concentrations of methylamine in urine of MSG-treated mice. Altered levels of creatine, citrate, succinate, and acetate were observed at 2 months of age and approached the values of control mice with aging. The development of obesity and insulin resistance in 6-month-old MSG mice was also accompanied by decreased mRNA expressions of adiponectin, lipogenetic and lipolytic enzymes and peroxisome proliferator-activated receptor-gamma in fat while mRNA expressions of lipogenetic enzymes in the liver were enhanced. At the age of 9 months, biochemical parameters of MSG mice were normalized to the values of the controls. This fact pointed to a limited predictive value of biochemical data up to age of 6 months as NMR metabolomics confirmed altered urine metabolic composition even at 9 months.

Unusual organic osmolytes in deep-sea animals: adaptations to hydrostatic pressure and other perturbants.

PubMed

Yancey, Paul H; Blake, Wendy R; Conley, James

2002-11-01

Shallow-living marine invertebrates use free amino acids as cellular osmolytes, while most teleosts use almost no organic osmolytes. Recently we found unusual osmolyte compositions in deep-sea animals. Trimethylamine N-oxide (TMAO) increases with depth in muscles of some teleosts, skates, and crustaceans (up to 300 mmol/kg at 2900 m). Other deep-sea animals had high levels of (1). scyllo-inositol in echinoderms, gastropods, and polychaetes, (2). that polyol plus beta-alanine and betaine in octopods, (3). hypotaurine, N-methyltaurine, and unidentified methylamines in vestimentiferans from hydrothermal vents and cold seeps, and (4). a depth-correlated serine-phosphate osmolyte in vesicomyid clams from trench seeps. We hypothesize that some of these solutes counteract effects of hydrostatic pressure. With lactate dehydrogenase, actin, and pyruvate kinase, 250 mM TMAO (but not glycine) protected both ligand binding and protein stability against pressure. To test TMAO in living cells, we grew yeast under pressure. After 1 h at 71 MPa, 3.5 h at 71 MPa, and 17 h at 30 MPa, 150 mM TMAO generally doubled the number of cells that formed colonies. Sulfur-based osmolytes which are not correlated with depth, such as hypotaurine and thiotaurine, are probably involved in sulfide metabolism and detoxification. Thus deep-sea osmolytes may have at least two other roles beyond acting as simple compatible osmotica.

MAPbI2.9-xBrxCl0.1 hybrid halide perovskites: Shedding light on the effect of chloride and bromide ions on structural and photoluminescence properties

NASA Astrophysics Data System (ADS)

Atourki, Lahoucine; Vega, Erika; Marí, Bernabé; Mollar, Miguel; Ait Ahsaine, Hassan; Bouabid, Khalid; Ihlal, Ahmed

2016-12-01

The optical and structural properties of CH3NH3PbI3 can be adjusted by introducing other extrinsic ions such as chloride and bromide. In this work, mixed bromide iodide lead perovskites with a 10% fraction of chloride were prepared from methylamine, lead nitrate and the corresponding hydro acid (X = I, Br, Cl). The effect of bromide and chloride incorporation on different properties of perovskite thin film was investigated. The Pawley fit method indicates the formation of the iodide halide MAPbI3 Pm-3 m cubic phase for x = 0 and the tetragonal P4/mmm phase for x ≥ 0.3. All deposited films showed a strong absorbance in the UV-vis range. The band gap values were estimated from absorbance measurements. It was found that the onset of the absorption edge for MAPbI2.9-xBrxCl0.1 thin film perovskites ranges between 1.60 and 1.80 eV. Moreover, it was found that both Cl and Br affect the PL emission of the mixed halide lead perovskite, the MAPbI2.9-xBrxCl0.1 films displayed intermediate values from 730 nm (MAPbI2.2Br0.7Cl0.1) to 770 nm (MAPbI2.6Br0.3Cl0.1).

The genome of Methylobacillus flagellatus, the molecular basis forobligate methylotrophy, and the polyphyletic origin ofmethylotrophy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chistoserdova, Ludmila; Lapidus, Alla; Han, Cliff

Along with methane, methanol and methylated amines representimportant biogenic atmospheric constituents, thus not only methanotrophs,but also non-methanotrophic methylotrophs play a significant role inglobal carbon cycling. The complete genome of a model obligate methanoland methylamine utilizer, Methylobacillus flagellatus (strain KT) wassequenced. The genome is represented by a single circular chromosome ofapproximately 3 Mb pairs, potentially encoding a total of 2,766 proteins.Based on genome analysis as well as the results from previous genetic andmutational analyses, methylotrophy is enabled by methanol- andmethylamine dehydrogenases, the tetrahydromethanopterin-linkedformaldehyde oxidation pathway, the assimilatory and dissimilatorybranches of the ribulose monophosphate cycle, and by formatedehydrogenases. Some of the methylotrophymore » genes are present in more thanone (identical or non-identical) copy. The obligate dependence on singlecarbon compounds appears to be due to the incomplete tricarboxylic acidcycle, as no genes potentially encoding alpha ketoglutarate, malate orsuccinate dehydrogenases are identifiable. The genome of M. flagellatuswas compared, in terms of methylotrophy functions, to the previouslysequenced genomes of three methylotrophs: Methylobacterium extorquens(Alphaproteobacterium, 7 Mbp), Methylibium petroleophilum(Betaproteobacterium, 4 Mbp), and Methylococcus capsulatus(Gammaproteobacterium, 3.3 Mbp). Strikingly, metabolically and/orphylogenetically, methylotrophy functions in M. flagellatus were moresimilar to the ones in M. capsulatus and M. extorquens than to the onesin the more closely related M. petroleophilum, providing the firstgenomic evidence for the polyphyletic origin of methylotrophy inBetaproteobacteria.« less

Removal of trimethylamine (fishy odor) by C₃ and CAM plants.

PubMed

Boraphech, Phattara; Thiravetyan, Paitip

2015-08-01

From screening 23 plant species, it was found that Pterocarpus indicus (C3) and Sansevieria trifasciata (crassulacean acid metabolism (CAM)) were the most effective in polar gaseous trimethylamine (TMA) uptake, reaching up to 90% uptake of initial TMA (100 ppm) within 8 h, and could remove TMA at cycles 1-4 without affecting photosystem II (PSII) photochemistry. Up to 55 and 45% of TMA was taken up by S. trifasciata stomata and leaf epicuticular wax, respectively. During cycles 1-4, interestingly, S. trifasciata changed its stomata apertures, which was directly induced by gaseous TMA and light treatments. In contrast, for P. indicus the leaf epicuticular wax and stem were the major pathways of TMA removal, followed by stomata; these pathways accounted for 46, 46, and 8%, respectively, of TMA removal percentages. Fatty acids, particularly tetradecanoic (C14) acid and octadecanoic (C18) acid, were found to be the main cuticular wax components in both plants, and were associated with TMA removal ability. Moreover, the plants could degrade TMA via multiple metabolic pathways associated with carbon/nitrogen interactions. In CAM plants, one of the crucial pathways enabled 78% of TMA to be transformed directly to dimethylamine (DMA) and methylamine (MA), which differed from C3 plant pathways. Various metabolites were also produced for further detoxification and mineralization so that TMA was completely degraded by plants.

Albibacter methylovorans gen. nov., sp. nov., a novel aerobic, facultatively autotrophic and methylotrophic bacterium that utilizes dichloromethane.

PubMed

Doronina, N V; Trotsenko, Y A; Tourova, T P; Kuznetsov, B B; Leisinger, T

2001-05-01

A novel genus, Albibacter, with one species, Albibacter methylovorans sp. nov., is proposed for a facultatively chemolithotrophic and methylotrophic bacterium (strain DM10T) with the ribulose bisphosphate (RuBP) pathway of C1 assimilation. The bacterium is a Gram-negative, aerobic, asporogenous, nonmotile, colourless rod that multiplies by binary fission. The organism utilizes dichloromethane, methanol, methylamine, formate and CO2/H2, as well as a variety of polycarbon compounds, as carbon and energy sources. It is neutrophilic and mesophilic. The major cellular fatty acids are straight-chain unsaturated C18:1, saturated C16:0 and cyclopropane C19:0 acids. The main ubiquinone is Q-10. The dominant phospholipids are phosphatidyl ethanolamine, phosphatidyl glycerol, phosphatidyl choline and cardiolipin. The DNA G+C content is 66.7 mol%. Strain DM10T has a very low degree of DNA-DNA hybridization (4-7%) with the type species of the genera Paracoccus, Xanthobacter, Blastobacter, Angulomicrobium, Ancylobacter and Ralstonia of RuBP pathway methylobacteria. Another approach, involving comparative 16S rDNA analysis, has shown that the novel isolate represents a separate branch within the alpha-2 subgroup of the Proteobacteria. The type species of the new genus is Albibacter methylovorans sp. nov.; the type strain is DM10T (= VKM B-2236T = DSM 13819T).

Host-parasite co-metabolic activation of antitrypanosomal aminomethyl-benzoxaboroles

PubMed Central

Scullion, Paul; del Pino, Ricardo C.; Vincent, Isabel M.; Zhang, Yong-Kang; Alley, Michael R. K.; Jacobs, Robert T.; Read, Kevin D.

2018-01-01

Recent development of benzoxaborole-based chemistry gave rise to a collection of compounds with great potential in targeting diverse infectious diseases, including human African Trypanosomiasis (HAT), a devastating neglected tropical disease. However, further medicinal development is largely restricted by a lack of insight into mechanism of action (MoA) in pathogenic kinetoplastids. We adopted a multidisciplinary approach, combining a high-throughput forward genetic screen with functional group focused chemical biological, structural biology and biochemical analyses, to tackle the complex MoAs of benzoxaboroles in Trypanosoma brucei. We describe an oxidative enzymatic pathway composed of host semicarbazide-sensitive amine oxidase and a trypanosomal aldehyde dehydrogenase TbALDH3. Two sequential reactions through this pathway serve as the key underlying mechanism for activating a series of 4-aminomethylphenoxy-benzoxaboroles as potent trypanocides; the methylamine parental compounds as pro-drugs are transformed first into intermediate aldehyde metabolites, and further into the carboxylate metabolites as effective forms. Moreover, comparative biochemical and crystallographic analyses elucidated the catalytic specificity of TbALDH3 towards the benzaldehyde benzoxaborole metabolites as xenogeneic substrates. Overall, this work proposes a novel drug activation mechanism dependent on both host and parasite metabolism of primary amine containing molecules, which contributes a new perspective to our understanding of the benzoxaborole MoA, and could be further exploited to improve the therapeutic index of antimicrobial compounds. PMID:29425238

Laboratory observations of temperature and humidity dependencies of nucleation and growth rates of sub-3 nm particles

NASA Astrophysics Data System (ADS)

Yu, Huan; Dai, Liang; Zhao, Yi; Kanawade, Vijay P.; Tripathi, Sachchida N.; Ge, Xinlei; Chen, Mindong; Lee, Shan-Hu

2017-02-01

Temperature and relative humidity (RH) are the most important thermodynamic parameters in aerosol formation, yet laboratory studies of nucleation and growth dependencies on temperature and RH are lacking. Here we report the experimentally observed temperature and RH dependences of sulfuric acid aerosol nucleation and growth. Experiments were performed in a flow tube in the temperature range from 248 to 313 K, RH from 0.8% to 79%, and relative acidity (RA) of sulfuric acid from 6 × 10-5 to 0.38 (2 × 107-109 cm-3). The impurity levels of base compounds were determined to be NH3 < 23 pptv (parts per thousand by volume), methylamine < 1.5 pptv, and dimethylamine < 0.52 pptv. Our results showed that low temperatures favor nucleation at fixed sulfuric acid concentration but impede nucleation when RA is fixed. It is also shown that binary nucleation of sulfuric acid and water is negligible in planetary boundary layer temperature and sulfuric acid ranges. An empirical algorithm was derived to correlate the nucleation rate with RA, RH, and temperature together. Collision-limited condensation of free-sulfuric acid molecules fails to predict the observed growth rate in the sub-3 nm size range, as well as its dependence on temperature and RH. This suggests that evaporation, sulfuric acid hydration, and possible involvement of other ternary molecules should be considered for the sub-3 nm particle growth.

In vitro effects of sodium bicarbonate buffer on rumen fermentation, levels of lipopolysaccharide and biogenic amine, and composition of rumen microbiota.

PubMed

Mao, Shengyong; Huo, Wenjie; Liu, Junhua; Zhang, Ruiyang; Zhu, Weiyun

2017-03-01

Diets containing high levels of carbohydrates provoke a rapid decrease of rumen pH and high levels of biogenic amines and lipopolysaccharides (LPS), which severely impair the health and performance of ruminants. The goal of this study was to evaluate the effects of sodium bicarbonate (BC) buffer on rumen fermentation, levels of LPS and biogenic amine, and composition of rumen microbiota using in vitro rumen cultures. Sodium bicarbonate supplementation increased (P < 0.05) the final pH levels and concentrations of total volatile fatty acids and LPS, as well as the proportions of acetate, propionate, isobutyrate, isovalerate and valerate, and it decreased (P < 0.05) the proportion of butyrate and the levels of lactic acid, methylamine, tryptamine, tyramine, histamine and putrescine compared with the control. Pyrosequencing of the 16S rRNA gene showed that BC inclusion increased (P < 0.05) the bacterial diversity index compared with the control. Adding BC also decreased (P < 0.05) the relative abundance of Streptococcus and Butyrivibrio and increased (P < 0.05) the proportions of Ruminococcus, Succinivibrio and Prevotella. Sodium bicarbonate supplementation has beneficial effects in the reduction of bioamine levels and the increase in ruminal pH, and in modifying the microbial ecology of the rumen; however, it results in an accumulation of LPS under high-grain diet conditions. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Can Internal Conversion BE Controlled by Mode-Specific Vibrational Excitation in Polyatomic Molecules

NASA Astrophysics Data System (ADS)

Portnov, Alexander; Epshtein, Michael; Bar, Ilana

2017-06-01

Nonadiabatic processes, dominated by dynamic passage of reactive fluxes through conical intersections (CIs) are considered to be appealing means for manipulating reaction paths. One approach that is considered to be effective in controlling the course of dissociation processes is the selective excitation of vibrational modes containing a considerable component of motion. Here, we have chosen to study the predissociation of the model test molecule, methylamine and its deuterated isotopologues, excited to well-characterized quantum states on the first excited electronic state, S_{1}, by following the N-H(D) bond fission dynamics through sensitive H(D) photofragment probing. The branching ratios between slow and fast H(D) photofragments, the internal energies of their counter radical photofragments and the anisotropy parameters for fast H photofragments, confirm correlated anomalies for predissociation initiated from specific rovibronic states, reflecting the existence of a dynamic resonance in each molecule. This resonance strongly depends on the energy of the initially excited rovibronic states, the evolving vibrational mode on the repulsive S_{1} part during N-H(D) bond elongation, and the manipulated passage through the CI that leads to radicals excited with C-N-H(D) bending and preferential perpendicular bond breaking, relative to the photolyzing laser polarization, in molecules containing the NH_{2} group. The indicated resonance plays an important role in the bifurcation dynamics at the CI and can be foreseen to exist in other photoinitiated processes and to control their outcome.

The in vivo pH of the extravascular space of the lung

PubMed Central

Effros, Richard M.; Chinard, Francis P.

1969-01-01

The partition of 5,5-dimethyloxazolidine-2,4-dione (DMO) and of 11 amines between the vascular and extravascular spaces of the lung has been determined by the multiple indicator dilution technique. Four amines (nicotine, pentylamine, quinine, and benzylamine) were found to have pH-sensitive tissue to blood concentration ratios. Of these, tritiated nicotine appears to be the nost satisfactory indicator of tissue pH and values for the pH of the pulmonary extravascular space (pHe) have been calculated from the nicotine data. At an arterial pH (pHart) between 7.38 and 7.43 pHe averaged 6.69 ±0.07. Changes in pHe usually paralleled but were consistently less than concomitant changes in pHart. Alterations in PCO2 at constant pHart regularly produced relatively small, parallel changes in extravascular hydrogen ion concentrations. Local alterations in tissue pH due to PCO2 changes are apparently buffered quite rapidly and the pHe of the lung seems more closely linked to pHart than the cellular pH of other tissues. DMO, guanidine, methylamine, morphine, and atropine were confined to the vascular volume during the first circulation and could not be used to measure tissue pH. Histamine appeared to be bound to a pH-insensitive site. The extravascular distributions of antipyrine and aniline were unresponsive to alterations in arterial pH, presumably because they are essentially uncharged at pH levels found in the lung. PMID:4898722

Na+/H+ and K+/H+ Antiport in Root Membrane Vesicles Isolated from the Halophyte Atriplex and the Glycophyte Cotton 1

PubMed Central

Hassidim, Miriam; Braun, Yael; Lerner, Henri R.; Reinhold, Leonora

1990-01-01

Proton fluxes have been followed into and out of membrane vesicles isolated from the roots of the halophyte Atriplex nummularia and the glycophyte Gossypium hirsutum, with the aid of the ΔpH probe [14C]methylamine. Evidence is presented for the operation of Na+/H+ and K+/H+ antiporters in the membranes of both plants. Cation supply after a pH gradient has been set up across the vesicle membrane (either as a result of providing ATP to the H+-ATPase or by imposing an artificial pH gradient) brings about dissipation of the ΔpH, but does not depolarize the membrane potential as observed in similar experiments, but in the absence of Cl−, using the ΔΨ probe SCN−. Cation/H+ exchange is thus indicated. This exchange is not due to nonspecific electric coupling, nor to competition for anionic adsorption sites on the membrane, nor to inhibition of the H+-ATPase; coupling of the opposed cation and H+ fluxes by a membrane component is the most likely explanation. Saturation kinetics have been observed for both Na+/H+ and K+/H+ antiport in Atriplex. Moreover, additive effects are obtained when Na+ is supplied together with saturating concentrations of K+, and vice versa, suggesting that separate antiporters for Na+ and for K+ may be operating. In the case of both Atriplex and Gossypium evidence was obtained suggesting the presence of antiporters in both plasmalemma and tonoplast. PMID:16667918

Na/H and k/h antiport in root membrane vesicles isolated from the halophyte atriplex and the glycophyte cotton.

PubMed

Hassidim, M; Braun, Y; Lerner, H R; Reinhold, L

1990-12-01

Proton fluxes have been followed into and out of membrane vesicles isolated from the roots of the halophyte Atriplex nummularia and the glycophyte Gossypium hirsutum, with the aid of the DeltapH probe [(14)C]methylamine. Evidence is presented for the operation of Na(+)/H(+) and K(+)/H(+) antiporters in the membranes of both plants. Cation supply after a pH gradient has been set up across the vesicle membrane (either as a result of providing ATP to the H(+)-ATPase or by imposing an artificial pH gradient) brings about dissipation of the DeltapH, but does not depolarize the membrane potential as observed in similar experiments, but in the absence of Cl(-), using the DeltaPsi probe SCN(-). Cation/H(+) exchange is thus indicated. This exchange is not due to nonspecific electric coupling, nor to competition for anionic adsorption sites on the membrane, nor to inhibition of the H(+)-ATPase; coupling of the opposed cation and H(+) fluxes by a membrane component is the most likely explanation. Saturation kinetics have been observed for both Na(+)/H(+) and K(+)/H(+) antiport in Atriplex. Moreover, additive effects are obtained when Na(+) is supplied together with saturating concentrations of K(+), and vice versa, suggesting that separate antiporters for Na(+) and for K(+) may be operating. In the case of both Atriplex and Gossypium evidence was obtained suggesting the presence of antiporters in both plasmalemma and tonoplast.

Estimating Atomic Contributions to Hydration and Binding Using Free Energy Perturbation.

PubMed

Irwin, Benedict W J; Huggins, David J

2018-06-12

We present a general method called atom-wise free energy perturbation (AFEP), which extends a conventional molecular dynamics free energy perturbation (FEP) simulation to give the contribution to a free energy change from each atom. AFEP is derived from an expansion of the Zwanzig equation used in the exponential averaging method by defining that the system total energy can be partitioned into contributions from each atom. A partitioning method is assumed and used to group terms in the expansion to correspond to individual atoms. AFEP is applied to six example free energy changes to demonstrate the method. Firstly, the hydration free energies of methane, methanol, methylamine, methanethiol, and caffeine in water. AFEP highlights the atoms in the molecules that interact favorably or unfavorably with water. Finally AFEP is applied to the binding free energy of human immunodeficiency virus type 1 protease to lopinavir, and AFEP reveals the contribution of each atom to the binding free energy, indicating candidate areas of the molecule to improve to produce a more strongly binding inhibitor. FEP gives a single value for the free energy change and is already a very useful method. AFEP gives a free energy change for each "part" of the system being simulated, where part can mean individual atoms, chemical groups, amino acids, or larger partitions depending on what the user is trying to measure. This method should have various applications in molecular dynamics studies of physical, chemical, or biochemical phenomena, specifically in the field of computational drug discovery.

Complex coupled metabolic and prokaryotic community responses to increasing temperatures in anaerobic marine sediments: critical temperatures and substrate changes

PubMed Central

Roussel, Erwan G.; Cragg, Barry A.; Webster, Gordon; Sass, Henrik; Tang, Xiaohong; Williams, Angharad S.; Gorra, Roberta; Weightman, Andrew J.; Parkes, R. John

2015-01-01

The impact of temperature (0–80°C) on anaerobic biogeochemical processes and prokaryotic communities in marine sediments (tidal flat) was investigated in slurries for up to 100 days. Temperature had a non-linear effect on biogeochemistry and prokaryotes with rapid changes over small temperature intervals. Some activities (e.g. methanogenesis) had multiple ‘windows’ within a large temperature range (∼10 to 80°C). Others, including acetate oxidation, had maximum activities within a temperature zone, which varied with electron acceptor [metal oxide (up to ∼34°C) and sulphate (up to ∼50°C)]. Substrates for sulphate reduction changed from predominantly acetate below, and H2 above, a 43°C critical temperature, along with changes in activation energies and types of sulphate-reducing Bacteria. Above ∼43°C, methylamine metabolism ceased with changes in methanogen types and increased acetate concentrations (>1 mM). Abundances of uncultured Archaea, characteristic of deep marine sediments (e.g. MBGD Euryarchaeota, ‘Bathyarchaeota’) changed, indicating their possible metabolic activity and temperature range. Bacterial cell numbers were consistently higher than archaeal cells and both decreased above ∼15°C. Substrate addition stimulated activities, widened some activity temperature ranges (methanogenesis) and increased bacterial (×10) more than archaeal cell numbers. Hence, additional organic matter input from climate-related eutrophication may amplify the impact of temperature increases on sedimentary biogeochemistry. PMID:26207045

Mechanical forces regulate the reactivity of a thioester bond in a bacterial adhesin

PubMed Central

Echelman, Daniel J.; Lee, Alex Q.; Fernández, Julio M.

2017-01-01

Bacteria must withstand large mechanical shear forces when adhering to and colonizing hosts. Recent structural studies on a class of Gram-positive bacterial adhesins have revealed an intramolecular Cys-Gln thioester bond that can react with surface-associated ligands to covalently anchor to host surfaces. Two other examples of such internal thioester bonds occur in certain anti-proteases and in the immune complement system, both of which react with the ligand only after the thioester bond is exposed by a proteolytic cleavage. We hypothesized that mechanical forces in bacterial adhesion could regulate thioester reactivity to ligand analogously to such proteolytic gating. Studying the pilus tip adhesin Spy0125 of Streptococcus pyogenes, we developed a single molecule assay to unambiguously resolve the state of the thioester bond. We found that when Spy0125 was in a folded state, its thioester bond could be cleaved with the small-molecule nucleophiles methylamine and histamine, but when Spy0125 was mechanically unfolded and subjected to forces of 50–350 piconewtons, thioester cleavage was no longer observed. For folded Spy0125 without mechanical force exposure, thioester cleavage was in equilibrium with spontaneous thioester reformation, which occurred with a half-life of several minutes. Functionally, this equilibrium reactivity allows thioester-containing adhesins to sample potential substrates without irreversible cleavage and inactivation. We propose that such reversible thioester reactivity would circumvent potential soluble inhibitors, such as histamine released at sites of inflammation, and allow the bacterial adhesin to selectively associate with surface-bound ligands. PMID:28348083

Burning velocity measurements of nitrogen-containing compounds.

PubMed

Takizawa, Kenji; Takahashi, Akifumi; Tokuhashi, Kazuaki; Kondo, Shigeo; Sekiya, Akira

2008-06-30

Burning velocity measurements of nitrogen-containing compounds, i.e., ammonia (NH3), methylamine (CH3NH2), ethylamine (C2H5NH2), and propylamine (C3H7NH2), were carried out to assess the flammability of potential natural refrigerants. The spherical-vessel (SV) method was used to measure the burning velocity over a wide range of sample and air concentrations. In addition, flame propagation was directly observed by the schlieren photography method, which showed that the spherical flame model was applicable to flames with a burning velocity higher than approximately 5 cm s(-1). For CH3NH2, the nozzle burner method was also used to confirm the validity of the results obtained by closed vessel methods. We obtained maximum burning velocities (Su0,max) of 7.2, 24.7, 26.9, and 28.3 cm s(-1) for NH3, CH3NH2, C2H5NH2, and C3H7NH2, respectively. It was noted that the burning velocities of NH3 and CH3NH2 were as high as those of the typical hydrofluorocarbon refrigerants difluoromethane (HFC-32, Su0,max=6.7 cm s(-1)) and 1,1-difluoroethane (HFC-152a, Su0,max=23.6 cm s(-1)), respectively. The burning velocities were compared with those of the parent alkanes, and it was found that introducing an NH2 group into hydrocarbon molecules decreases their burning velocity.

New ferrocenic pyrrolo[1,2-a]quinoxaline derivatives: synthesis, and in vitro antimalarial activity.

PubMed

Guillon, Jean; Moreau, Stéphane; Mouray, Elisabeth; Sinou, Véronique; Forfar, Isabelle; Fabre, Solene Belisle; Desplat, Vanessa; Millet, Pascal; Parzy, Daniel; Jarry, Christian; Grellier, Philippe

2008-10-15

Following our search for antimalarial compounds, novel series of ferrocenic pyrrolo[1,2-a]quinoxaline derivatives 1-2 were synthesized from various substituted nitroanilines and tested for in vitro activity upon the erythrocytic development of Plasmodiumfalciparum strains with different chloroquine-resistance status. The pyrrolo[1,2-a]quinoxalines 1 were prepared in 6-8 steps through a regioselective palladium-catalyzed monoamination by coupling 4-chloropyrrolo[1,2-a]quinoxalines with 1,3-bis(aminopropyl)piperazine or -methylamine using Xantphos as the ligand. The ferrocenic bispyrrolo[1,2-a]quinoxalines 2 were prepared by reductive amination of previously described bispyrrolo[1,2-a]quinoxalines 9 with ferrocene-carboxaldehyde, by treatment with NaHB(OAc)(3). The best results were observed with ferrocenic pyrrolo[1,2-a]quinoxalines linked by a bis(3-aminopropyl)piperazine. Moreover, it was observed that a methoxy group on the pyrrolo[1,2-a]quinoxaline nucleus and no substitution on the terminal N-ferrocenylmethylamine function enhanced the pharmacological activity. Selected compounds 1b, 1f-h, 1l and 2a were tested for their ability to inhibit beta-haematin formation, the synthetic equivalent of hemozoin, by using the HPIA (heme polymerization inhibitory activity) assay. Of the tested compounds, only 2a showed a beta-haematin formation inhibition, but no inhibition of haem polymerization was observed with the other selected ferrocenic monopyrrolo[1,2-a]quinoxaline derivatives 1b, 1f-h and 1l, as the IC(50) values were superior to 10 equivalents.

Carbon source-dependent expansion of the genetic code in bacteria

PubMed Central

Prat, Laure; Heinemann, Ilka U.; Aerni, Hans R.; Rinehart, Jesse; O’Donoghue, Patrick; Söll, Dieter

2012-01-01

Despite the fact that the genetic code is known to vary between organisms in rare cases, it is believed that in the lifetime of a single cell the code is stable. We found Acetohalobium arabaticum cells grown on pyruvate genetically encode 20 amino acids, but in the presence of trimethylamine (TMA), A. arabaticum dynamically expands its genetic code to 21 amino acids including pyrrolysine (Pyl). A. arabaticum is the only known organism that modulates the size of its genetic code in response to its environment and energy source. The gene cassette pylTSBCD, required to biosynthesize and genetically encode UAG codons as Pyl, is present in the genomes of 24 anaerobic archaea and bacteria. Unlike archaeal Pyl-decoding organisms that constitutively encode Pyl, we observed that A. arabaticum controls Pyl encoding by down-regulating transcription of the entire Pyl operon under growth conditions lacking TMA, to the point where no detectable Pyl-tRNAPyl is made in vivo. Pyl-decoding archaea adapted to an expanded genetic code by minimizing TAG codon frequency to typically ∼5% of ORFs, whereas Pyl-decoding bacteria (∼20% of ORFs contain in-frame TAGs) regulate Pyl-tRNAPyl formation and translation of UAG by transcriptional deactivation of genes in the Pyl operon. We further demonstrate that Pyl encoding occurs in a bacterium that naturally encodes the Pyl operon, and identified Pyl residues by mass spectrometry in A. arabaticum proteins including two methylamine methyltransferases. PMID:23185002

Characterization of solution-phase and gas-phase reactions in on-line electrochemistry-thermospray tandem mass spectrometry.

PubMed

Volk, K J; Yost, R A; Brajter-Toth, A

1989-07-14

Electrochemistry was used on-line with high-performance liquid chromatography-thermospray tandem mass spectrometry to provide insight into the solution-phase decomposition reactions of electrochemically generated oxidation products. Products formed during electrooxidation were monitored as the electrode potential was varied. The solution reactions which follow the initial electron transfer at the electrode are affected by the vaporizer tip temperature of the thermospray probe and the composition of the thermospray buffer. Either hydrolysis or ammonolysis reactions of the initial electrochemical oxidation products can occur with pH 7 ammonium acetate buffer. Both the electrochemically generated and the synthesized disulfide of 6-thiopurine decompose under thermospray conditions to produce 6-thiopurine and purine-6-sulfinate. Solution-phase studies indicate that nucleophilic and electrophilic substitution reactions with purine-6-sulfinate result in the formation of purine, adenine, and hypoxanthine. Products were identified and characterized by tandem mass spectrometry. This work shows the first example of high-performance liquid chromatography used on-line with electrochemistry to separate stable oxidation products prior to analysis by thermospray tandem mass spectrometry. In addition, solution-phase and gas-phase studies with methylamine show that the site of the nucleophilic and electrophilic reactions is probably inside the thermospray probe. Most importantly, these results also show that the on-line combination of electrochemistry with thermospray tandem mass spectrometry provides valuable information about redox and associated chemical reactions of biological molecules such as the structures of intermediates or products as well as providing insight into reaction pathways.

Metabolic effects of dark chocolate consumption on energy, gut microbiota, and stress-related metabolism in free-living subjects.

PubMed

Martin, Francois-Pierre J; Rezzi, Serge; Peré-Trepat, Emma; Kamlage, Beate; Collino, Sebastiano; Leibold, Edgar; Kastler, Jürgen; Rein, Dietrich; Fay, Laurent B; Kochhar, Sunil

2009-12-01

Dietary preferences influence basal human metabolism and gut microbiome activity that in turn may have long-term health consequences. The present study reports the metabolic responses of free living subjects to a daily consumption of 40 g of dark chocolate for up to 14 days. A clinical trial was performed on a population of 30 human subjects, who were classified in low and high anxiety traits using validated psychological questionnaires. Biological fluids (urine and blood plasma) were collected during 3 test days at the beginning, midtime and at the end of a 2 week study. NMR and MS-based metabonomics were employed to study global changes in metabolism due to the chocolate consumption. Human subjects with higher anxiety trait showed a distinct metabolic profile indicative of a different energy homeostasis (lactate, citrate, succinate, trans-aconitate, urea, proline), hormonal metabolism (adrenaline, DOPA, 3-methoxy-tyrosine) and gut microbial activity (methylamines, p-cresol sulfate, hippurate). Dark chocolate reduced the urinary excretion of the stress hormone cortisol and catecholamines and partially normalized stress-related differences in energy metabolism (glycine, citrate, trans-aconitate, proline, beta-alanine) and gut microbial activities (hippurate and p-cresol sulfate). The study provides strong evidence that a daily consumption of 40 g of dark chocolate during a period of 2 weeks is sufficient to modify the metabolism of free living and healthy human subjects, as per variation of both host and gut microbial metabolism.

Quantitation of biomarkers of exposure to nitrogen mustards in urine from rats dosed with nitrogen mustards and from an unexposed human population.

PubMed

Lemire, Sharon W; Barr, John R; Ashley, David L; Olson, Carl T; Hayes, Timothy L

2004-01-01

The nitrogen mustards bis(2-chloroethyl)ethylamine (HN1), bis(2-chloroethyl)methylamine (HN2), and tris(2-chloroethyl)amine (HN3) have the potential to be used as chemical terrorism agents because of their extreme vesicant properties. We modified a previously reported method to incorporate automated solid-phase extraction, improve chromatography, and include the urinary metabolite for HN3. The improved method was used to measure levels of the urinary metabolites N-ethyldiethanolamine (EDEA), N-methyldiethanolamine (MDEA), and triethanolamine (TEA) in rats dosed with HN1, HN2, and HN3, respectively, and to establish background levels of EDEA, MDEA, and TEA in human urine samples from a population with no known exposure to nitrogen mustards. Rat dosing experiments confirmed that EDEA, MDEA, and TEA could be detected in urine for at least 48 h after exposure to HN1, HN2, and HN3, respectively. Substantial amounts of EDEA (89 ng/mL), MDEA (170 ng/mL), and TEA (1105 ng/mL) were measured in the urine of rats exposed to 10 mg HN1, HN2, and HN3, respectively, 48 h after exposure. The background concentrations for TEA in the human population ranged from below the limit of detection (LOD 3 ng/mL) to approximately 6500 ng/mL. Neither EDEA (LOD 0.4 ng/mL) nor MDEA (LOD 0.8 ng/mL) was detected above the LOD in the human samples.

On the Mechanism and Rate of Spontaneous Decomposition of Amino Acids

PubMed Central

Alexandrova, Anastassia N.; Jorgensen, William L.

2011-01-01

Spontaneous decarboxylation of amino acids is among the slowest known reactions; it is much less facile than the cleavage of amide bonds in polypeptides. Establishment of the kinetics and mechanisms for this fundamental reaction is important for gauging the proficiency of enzymes. In the present study, multiple mechanisms for glycine decomposition in water are explored using QM/MM Monte Carlo simulations and free energy perturbation theory. Simple CO2 detachment emerges as the preferred pathway for decarboxylation; it is followed by water-assisted proton transfer to yield the products, CO2 and methylamine. The computed free energy of activation of 45 kcal/mol, and the resulting rate-constant of 1 × 10−21 s−1, can be compared with an extrapolated experimental rate constant of ~2 × 10−17 s−1 at 25 °C. The half-life for the reaction is more than 1 billion years. Furthermore, examination of deamination finds simple NH3-detachment yielding α-lactone to be the favored route, though it is less facile than decarboxylation by kcal/mol. Ab initio and DFT calculations with the CPCM hydration model were also carried out for the reactions; the computed free energies of activation for glycine decarboxylation agree with the QM/MM result, while deamination is predicted to be more favorable. QM/MM calculations were also performed for decarboxylation of alanine; the computed barrier is 2 kcal/mol higher than for glycine in qualitative accord with experiment. PMID:21995727

Diffusion of aqueous solutions of ionic, zwitterionic, and polar solutes

NASA Astrophysics Data System (ADS)

Teng, Xiaojing; Huang, Qi; Dharmawardhana, Chamila Chathuranga; Ichiye, Toshiko

2018-06-01

The properties of aqueous solutions of ionic, zwitterionic, and polar solutes are of interest to many fields. For instance, one of the many anomalous properties of aqueous solutions is the behavior of water diffusion in different monovalent salt solutions. In addition, solutes can affect the stabilities of macromolecules such as proteins in aqueous solution. Here, the diffusivities of aqueous solutions of sodium chloride, potassium chloride, tri-methylamine oxide (TMAO), urea, and TMAO-urea are examined in molecular dynamics simulations. The decrease in the diffusivity of water with the concentration of simple ions and urea can be described by a simple model in which the water molecules hydrogen bonded to the solutes are considered to diffuse at the same rate as the solutes, while the remainder of the water molecules are considered to be bulk and diffuse at almost the same rate as pure water. On the other hand, the decrease in the diffusivity of water with the concentration of TMAO is apparently affected by a decrease in the diffusion rate of the bulk water molecules in addition to the decrease due to the water molecules hydrogen bonded to TMAO. In other words, TMAO enhances the viscosity of water, while urea barely affects it. Overall, this separation of water molecules into those that are hydrogen bonded to solute and those that are bulk can provide a useful means of understanding the short- and long-range effects of solutes on water.

The syntheses, characterization and in vitro metabolism of nitracaine, methoxypiperamide and mephtetramine.

PubMed

Power, John D; Scott, Kenneth R; Gardner, Elizabeth A; Curran McAteer, Bronagh M; O'Brien, John E; Brehon, Margaret; Talbot, Brian; Kavanagh, Pierce V

2014-01-01

Three legal highs; nitracaine (3-(diethylamino)-2,2-dimethylpropyl 4-nitrobenzoate), methoxypiperamide (MEOP, (4-methoxyphenyl)(4-methylpiperazin-1-yl)methanone) and mephtetramine (MTTA, 2-((methylamino)methyl)-3,4-dihydronaphthalen-1(2H)-one) appeared in 2013 as new psychoactive substances (NPS) on Internet websites selling 'research chemicals'. These compounds were synthesized and analyzed via our synthesize, analyze, and metabolize (SAM) protocol. Nitracaine was synthesized by the transesterification of methyl 4-nitrobenzoate with 3-(diethylamino)-2,2-dimethylpropan-1-ol. Methoxypiperamide was synthesized by the reaction of 4-methoxybenzoyl chloride with 1-methylpiperazine, and mephtetramine through the Mannich reaction of 1-tetralone with paraformaldehyde and methylamine hydrochloride. Each compound was characterized by nuclear magnetic resonance (NMR), gas chromatography with electron impact mass spectrometry (GC-EIMS), liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and high resolution electrospray ionization mass spectrometry (HR-ESI-MS). A sample of nitracaine was also test-purchased from an Internet vendor and its structure confirmed by GC-EIMS and LC-ESI-MS. Finally, the in vitro metabolism of the nitracaine, mephtetramine, and methoxypiperamide was investigated, using a human microsomal liver extract, in order to tentatively identify potential metabolites that may be encountered in the analysis of biological samples in clinical or toxicology labs. The use of our SAM protocol highlights the ability of academic research labs to quickly respond to and disseminate information about emerging NPS. Copyright © 2014 John Wiley & Sons, Ltd.

Aerobic biodegradation of amines in industrial saline wastewaters.

PubMed

Campo, Pablo; Platten, William; Suidan, Makram T; Chai, Yunzhou; Davis, John W

2011-11-01

The treatment of hypersaline wastewaters represents a challenge since high salt concentrations disrupt bacteria present in normal biological treatments. This study was conducted to determine the fate of amines in two hypersaline wastewaters obtained from an industrial treatment plant processing influents with 3% and 7% of NaCl. The compounds were aniline (ANL), 4,4'-methylenedianiline (4,4'-MDA), cyclohexylamine (CHA), N-(2-aminoethyl)ethanolamine (AEA), N,N-diethylethanolamine (DEA), N,N-bis(2-hydroxyethyl)methylamine (MDEA), and tris(2-hydroxyethyl)amine (TEA). Mixtures of these chemicals with a mixed liquor suspended solids concentration of 1000 mg L(-1) were prepared at two salinities (3% and 7% NaCl). Ethanolamines were readily biodegraded at both salinities, following first-order kinetics with half-lives ranging between 10 and 58 h. Hydroxyl groups present in the ethanolamines had a positive impact on the biodegradation. Salinity did not affect the biodegradation rate of TEA and MDEA, whereas AEA and DEA degraded faster in 3% NaCl. After 48h, CHA was metabolized within a 24-h period in 3% NaCl, while no degradation was observed in 7% NaCl. ANL exhibited lag phases in both salinities and, in the following 24-h period, ANL concentrations dropped 40% and disappeared after 48 h. 4,4'-MDA degraded in 3% NaCl (half-life of 123 h) and remained unaltered after 120 h in 7% NaCl. Copyright © 2011 Elsevier Ltd. All rights reserved.

Bi-functionality of Opisthorchis viverrini aquaporins.

PubMed

Geadkaew, Amornrat; von Bülow, Julia; Beitz, Eric; Tesana, Smarn; Vichasri Grams, Suksiri; Grams, Rudi

2015-01-01

Aquaporins (AQP) are essential mediators of water regulation in all living organisms and members of the major intrinsic protein (MIP) superfamily of integral membrane proteins. They are potential vehicles or targets for chemotherapy, e.g. in Trypanosoma brucei melarsoprol and pentamidine uptake is facilitated by TbAQP-2. Transcriptome data suggests that there are at least three active aquaporins in the human liver fluke, Opisthorchis viverrini, OvAQP-1, 2 and 3, and crude RNA silencing of OvAQP-1 and 2 has recently been shown to affect parasite swelling in destilled water. In the present work we demonstrate that OvAQP-3 is a major water-conducting channel of the parasite, that it can be detected from the newly excysted juvenile to the adult stage and that it is present in major tissues of the parasite. Furthermore, a comparative functional characterization of the three parasite AQPs was performed by using Xenopus oocyte swelling and yeast phenotypic assays. OvAQP-1, OvAQP-2, and OvAQP-3 were found to conduct water and glycerol while only the latter two were also able to conduct urea. In addition, all OvAQPs were found to transport ammonia and methylamine. Our findings demonstrate that the sequence-based classification into orthodox aquaporins and glycerol-conducting aquaglyceroporins is not functionally conserved in the parasite and implicate a broder range of functions for these channels. Copyright © 2014 Elsevier B.V. and Société française de biochimie et biologie Moléculaire (SFBBM). All rights reserved.

Mechanism of alpha-amino acids decomposition in the gas phase. experimental and theoretical study of the elimination kinetics of N-benzyl glycine ethyl ester.

PubMed

Tosta, Maria; Oliveros, Jhenny C; Mora, Jose R; Córdova, Tania; Chuchani, Gabriel

2010-02-25

The gas-phase elimination kinetics of N-benzylglycine ethyl ester was examined in a static system, seasoned with allyl bromide, and in the presence of the free chain radical suppressor toluene. The working temperature and pressure range were 386.4-426.7 degrees C and 16.7-40.0 torr, respectively. The reaction showed to be homogeneous, unimolecular, and obeys a first-order rate law. The elimination products are benzylglycine and ethylene. However, the intermediate benzylglycine is unstable under the reaction conditions decomposing into benzyl methylamine and CO(2) gas. The variation of the rate coefficients with temperature is expressed by the following Arrhenius equation: log k(1) (s(-1)) = (11.83 +/- 0.52) - (190.3 +/- 6.9) kJ mol(-1) (2.303RT)(-1). The theoretical calculation of the kinetic parameters and mechanism of elimination of this ester were performed at B3LYP/6-31G*, B3LYP/6-31+G**, MPW1PW91/6-31G*, and MPW1PW91/6-31+G** levels of theory. The calculation results suggest a molecular mechanism of a concerted nonsynchronous six-membered cyclic transition state process. The analysis of bond order and natural bond orbital charges implies that the bond polarization of C(=O)O-C, in the sense of C(=O)O(delta-)...C(delta+), is rate determining. The experimental and theoretical parameters have been found to be in reasonable agreement.

A Hybrid Program for Fitting Rotationally Resolved Spectra of Floppy Molecules with One Large-Amplitude Rotatory Motion and One Large-Amplitude Oscillatory Motion

PubMed Central

Kleiner, Isabelle; Hougen, Jon T.

2015-01-01

A new hybrid-model fitting program for methylamine-like molecules has been developed, based on an effective Hamiltonian in which the ammonia-like inversion motion is treated using a tunneling formalism, while the internal-rotation motion is treated using an explicit kinetic energy operator and potential energy function. The Hamiltonian in the computer program is set up as a 2×2 partitioned matrix, where each diagonal block contains a traditional torsion-rotation Hamiltonian (as in the earlier program BELGI), and the two off-diagonal blocks contain tunneling terms. This hybrid formulation permits the use of the permutation-inversion group G6 (isomorphic to C3v) for terms in the two diagonal blocks, but requires G12 for terms in the off-diagonal blocks. The first application of the new program is to 2-methylmalonaldehyde. Microwave data for this molecule were previously fit using an all-tunneling Hamiltonian formalism to treat both large-amplitude-motions. For 2-methylmalonaldehyde, the hybrid program achieves the same quality of fit as was obtained with the all-tunneling program, but fits with the hybrid program eliminate a large discrepancy between internal rotation barriers in the OH and OD isotopologs of 2-methylmalonaldehyde that arose in fits with the all-tunneling program. This large isotopic shift in internal rotation barrier is thus almost certainly an artifact of the all-tunneling model. Other molecules for application of the hybrid program are mentioned. PMID:26439709

Superoxo, μ-peroxo, and μ-oxo complexes from heme/O2 and heme-Cu/O2 reactivity: Copper ligand influences in cytochrome c oxidase models

PubMed Central

Kim, Eunsuk; Helton, Matthew E.; Wasser, Ian M.; Karlin, Kenneth D.; Lu, Shen; Huang, Hong-wei; Moënne-Loccoz, Pierre; Incarvito, Christopher D.; Rheingold, Arnold L.; Honecker, Marcus; Kaderli, Susan; Zuberbühler, Andreas D.

2003-01-01

The O2-reaction chemistry of 1:1 mixtures of (F8)FeII (1; F8 = tetrakis(2,6-diflurorophenyl)porphyrinate) and [(LMe2N)CuI]+ (2; LMe2N = N,N-bis{2-[2-(N′,N′-4-dimethylamino)pyridyl]ethyl}methylamine) is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F8)FeIII-(O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{-}}}\\end{equation*}\\end{document}) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F8)FeIII–(O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{2-}}}\\end{equation*}\\end{document})–CuII(LMe2N)]+ (4), which thermally converts to [(F8)FeIII–(O)–CuII(LMe2N)]+ (5), which has an unusually bent (Fe–O–Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the ν(O–O) values observed in 4 and give rise to the novel structural features in 5. PMID:12655050

Determination of ergocalciferol in human plasma after Diels-Alder derivatization by LC-MS/MS and its application to a bioequivalence study.

PubMed

Contractor, Pritesh; Gandhi, Abhishek; Solanki, Gajendra; Shah, Priyanka A; Shrivastav, Pranav S

2017-12-01

An accurate, sensitive and selective method is developed for determination of ergocalciferol (vitamin D 2 ) in human plasma using LC-MS/MS. After liquid-liquid extraction with n- hexane, ergocalciferol was derivatized by reacting with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), a strong dienophile based on Diels-Alder reaction. Ergocalciferol and its deuterated internal standard, ergocalciferol-d6, were analyzed on X Select CSH C 18 (100 mm×4.6 mm, 2.5 µm) column using acetonitrile and 0.1% (v/v) formic acid in water containing 0.14% methylamine within 6.0 min under gradient elution mode. Tandem mass spectrometry in positive ionization mode was used to quantify ergocalciferol by multiple reaction monitoring (MRM). Entire data processing was done using Watson LIMS™ software which provided excellent data integrity and high throughput with improved operational efficiency. The major advantage of this method includes higher sensitivity (0.10 ng/mL), superior extraction efficiency (≥83%) and small sample volume (100 µL) for processing. The method was linear in the concentration range of 0.10-100 ng/mL for ergocalciferol. The intra-batch and inter-batch accuracy and precision (% CV) values varied from 97.3% to 109.0% and 1.01% to 5.16%, respectively. The method was successfully applied to support a bioequivalence study of 1.25 mg ergocalciferol capsules in 12 healthy subjects.

Serum metabonomic analysis of protective effects of Curcuma aromatica oil on renal fibrosis rats.

PubMed

Zhao, Liangcai; Zhang, Haiyan; Yang, Yunjun; Zheng, Yongquan; Dong, Minjian; Wang, Yaqiang; Bai, Guanghui; Ye, Xinjian; Yan, Zhihan; Gao, Hongchang

2014-01-01

Curcuma aromatica oil is a traditional herbal medicine demonstrating protective and anti-fibrosis activities in renal fibrosis patients. However, study of its mechanism of action is challenged by its multiple components and multiple targets that its active agent acts on. Nuclear magnetic resonance (NMR)-based metabonomics combined with clinical chemistry and histopathology examination were performed to evaluate intervening effects of Curcuma aromatica oil on renal interstitial fibrosis rats induced by unilateral ureteral obstruction. The metabolite levels were compared based on integral values of serum 1H NMR spectra from rats on 3, 7, 14, and 28 days after the medicine administration. Time trajectory analysis demonstrated that metabolic profiles of the agent-treated rats were restored to control levels after 7 days of dosage. The results confirmed that the agent would be an effective anti-fibrosis medicine in a time-dependent manner, especially in early renal fibrosis stage. Targeted metabolite analysis showed that the medicine could lower levels of lipid, acetoacetate, glucose, phosphorylcholine/choline, trimethylamine oxide and raise levels of pyruvate, glycine in the serum of the rats. Serum clinical chemistry and kidney histopathology examination dovetailed well with the metabonomics data. The results substantiated that Curcuma aromatica oil administration can ameliorate renal fibrosis symptoms by inhibiting some metabolic pathways, including lipids metabolism, glycolysis and methylamine metabolism, which are dominating targets of the agent working in vivo. This study further strengthens the novel analytical approach for evaluating the effect of traditional herbal medicine and elucidating its molecular mechanism.

Oxidative degradation of tetramethylammonium hydroxide (TMAH) by UV/persulfate and associated acute toxicity assessment.

PubMed

Huang, Jingting; Wang, Kai-Sung; Liang, Chenju

2017-07-29

Tetramethylammonium hydroxide (TMAH) is widely used in high-tech industries as a developing agent. Ultraviolet (UV) light-activated persulfate (PS, S 2 O 8 2- ) can be used to generate strongly oxidative sulfate radicals, and it also exhibits the potential to treat TMAH-containing wastewater. This study initially investigated the effect of S 2 O 8 2- concentration and UV strength on the UV/S 2 O 8 2- process for the degradation of TMAH in a batch reactor. The results suggested that 15 watts (W) of UV-activated S 2 O 8 2- at concentrations of 10 or 50 mM resulted in pseudo-first-order TMAH degradation rate constants of 3.1-4.2 × 10 -2 min -1 , which was adopted for determining the hydraulic retention time (HRT) in a continuous stirred tank reactor (CSTR). The operating conditions (15 W UV/10 mM S 2 O 8 2- ) with a HRT of 129 min resulted in stable residual concentrations of S 2 O 8 2- and TMAH at approximately 2.6 mM and 20 mg L -1 in effluent, respectively. Several TMAH degradation intermediates including trimethylamine, dimethylamine, and methylamine were also detected. The effluent was adjusted to a neutral pH and evaluated for its biological acute toxicity using Cyprinus carpio as a bioassay organism. The "bio-acute toxicity unit" (TU a ) was determined to be 1.41, which indicated that the effluent was acceptable for being discharged into an aquatic ecosystem.

Metabolic and trophic interactions modulate methane production by Arctic peat microbiota in response to warming

PubMed Central

Tveit, Alexander Tøsdal; Urich, Tim; Frenzel, Peter; Svenning, Mette Marianne

2015-01-01

Arctic permafrost soils store large amounts of soil organic carbon (SOC) that could be released into the atmosphere as methane (CH4) in a future warmer climate. How warming affects the complex microbial network decomposing SOC is not understood. We studied CH4 production of Arctic peat soil microbiota in anoxic microcosms over a temperature gradient from 1 to 30 °C, combining metatranscriptomic, metagenomic, and targeted metabolic profiling. The CH4 production rate at 4 °C was 25% of that at 25 °C and increased rapidly with temperature, driven by fast adaptations of microbial community structure, metabolic network of SOC decomposition, and trophic interactions. Below 7 °C, syntrophic propionate oxidation was the rate-limiting step for CH4 production; above this threshold temperature, polysaccharide hydrolysis became rate limiting. This change was associated with a shift within the functional guild for syntrophic propionate oxidation, with Firmicutes being replaced by Bacteroidetes. Correspondingly, there was a shift from the formate- and H2-using Methanobacteriales to Methanomicrobiales and from the acetotrophic Methanosarcinaceae to Methanosaetaceae. Methanogenesis from methylamines, probably stemming from degradation of bacterial cells, became more important with increasing temperature and corresponded with an increased relative abundance of predatory protists of the phylum Cercozoa. We concluded that Arctic peat microbiota responds rapidly to increased temperatures by modulating metabolic and trophic interactions so that CH4 is always highly produced: The microbial community adapts through taxonomic shifts, and cascade effects of substrate availability cause replacement of functional guilds and functional changes within taxa. PMID:25918393

Prebiotic chemistry: chemical evolution of organics on the primitive Earth under simulated prebiotic conditions.

PubMed

Dondi, Daniele; Merli, Daniele; Pretali, Luca; Fagnoni, Maurizio; Albini, Angelo; Serpone, Nick

2007-11-01

A series of prebiotic mixtures of simple molecules, sources of C, H, N, and O, were examined under conditions that may have prevailed during the Hadean eon (4.6-3.8 billion years), namely an oxygen-free atmosphere and a significant UV radiation flux over a large wavelength range due to the absence of an ozone layer. Mixtures contained a C source (methanol, acetone or other ketones), a N source (ammonia or methylamine), and an O source (water) at various molar ratios of C : H : N : O. When subjected to UV light or heated for periods of 7 to 45 days under an argon atmosphere, they yielded a narrow product distribution of a few principal compounds. Different initial conditions produced different distributions. The nature of the products was ascertained by gas chromatographic-mass spectral analysis (GC-MS). UVC irradiation of an aqueous methanol-ammonia-water prebiotic mixture for 14 days under low UV dose (6 x 10(-2) Einstein) produced methylisourea, hexamethylenetetramine (HMT), methyl-HMT and hydroxy-HMT, whereas under high UV dose (45 days; 1.9 x 10(-1) Einstein) yielded only HMT. By contrast, the prebiotic mixture composed of acetone-ammonia-water produced five principal species with acetamide as the major component; thermally the same mixture produced a different product distribution of four principal species. UVC irradiation of the CH(3)CN-NH(3)-H(2)O prebiotic mixture for 7 days gave mostly trimethyl-s-triazine, whereas in the presence of two metal oxides (TiO(2) or Fe(2)O(3)) also produced some HMT; the thermal process yielded only acetamide.

Synthesis and Characterization of Methylammonium Borohydride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Kathryn R.; Bowden, Mark E.; Kemmitt, Tim

2011-01-06

A new borohydride, [CH3NH3]+[BH4]-, has been synthesised by the metathesis of CH3NH3X and MBH4 in methylamine in order to determine its behaviour in comparison to ammonium borohydride [NH4]+[BH4]-. The introduction of methyl groups is expected to disrupt the hydrogen bonding network of [NH4]+[BH4]- and in turn alter the hydrogen release properties. Room temperature X-ray diffraction studies have shown that [CH3NH3]+[BH4]- adopts a tetragonal unit cell with lattice parameters of a = 4.9486 Å and b = 8.9083 Å. The room temperature structure shows considerable hydrogen mobility similar to that observed in NH3BH3. The kinetics and thermodynamics of these reactions havemore » been investigated and show hydrogen release follows a similar pathway to that of [NH4]+[BH4]-. Both compounds decompose slowly at room temperature and rapidly at ca. 40 °C to form the diammoniate of diborane or the methylated analogue [BH2(CH3NH2)2]+BH4-. The first stage of decomposition has been further investigated by means on in-situ X-ray diffraction and solid state 11B NMR spectroscopy, and appears to occur in the absence of any detectable intermediates to form crystalline [BH2(CH3NH2)2]+BH4-. [(CH3)2NH2]+[BH4]- and [BH2{(CH3)2NH}2]+BH4- have also been synthesised by analogous routes, indicating a more general applicability of the synthetic method.« less

Identification using versatile sampling and analytical methods of volatile compounds from Streptomyces albidoflavus grown on four humid building materials and one synthetic medium.

PubMed

Claeson, A-S; Sunesson, A-L

2005-01-01

The Streptomyces spp. form a common group of bacteria found in the indoor air of water-damaged buildings. They are known for their capability to produce compounds, like geosmin, with low odor thresholds. In this study, two strains of Streptomyces albidoflavus were cultivated on pinewood, gypsum board, particle-board, sand and tryptone glucose extract agar (TGEA). Air samples from the cultures were collected on six different adsorbents and chemosorbents to sample a wide range of compounds such as VOCs, aldehydes, amines and lightweight organic acids. The samples were analyzed with gas chromatography, high-pressure liquid chromatography and ion chromatography. Mass spectrometry was used for identification of the compounds. Metabolites were found and identified in air samples from cultures on all materials except sand. Alcohols and ketones were the dominating compound groups produced by cultures grown on pinewood and gypsum board. Few metabolites were produced on particle-board. The culture growing on TGEA produced mainly sulfur compounds and sesquiterpenes. Ammonia, methylamine, diethylamine, ethylamine and one unidentifiable amine were also found from cultivation on TGEA. The growth medium was of crucial importance to the production of potentially irritating metabolites. Microbial growth and the production of volatile metabolites is one possible explanation for building-related health problems. Streptomyces spp. are frequently found in water-damaged buildings. This study shows that Streptomyces spp. are able to produce not only odorous compounds like geosmin, but also potentially irritating compounds. This finding should be of interest in indoor air investigations.

Methylene Homologues of Artemisone: An Unexpected Structure-Activity Relationship and a Possible Implication for the Design of C10-Substituted Artemisinins.

PubMed

Wu, Yuet; Wu, Ronald Wai Kung; Cheu, Kwan Wing; Williams, Ian D; Krishna, Sanjeev; Slavic, Ksenija; Gravett, Andrew M; Liu, Wai M; Wong, Ho Ning; Haynes, Richard K

2016-07-05

We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with divinyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The transcriptional response of microbial communities in thawing Alaskan permafrost soils.

PubMed

Coolen, Marco J L; Orsi, William D

2015-01-01

Thawing of permafrost soils is expected to stimulate microbial decomposition and respiration of sequestered carbon. This could, in turn, increase atmospheric concentrations of greenhouse gasses, such as carbon dioxide and methane, and create a positive feedback to climate warming. Recent metagenomic studies suggest that permafrost has a large metabolic potential for carbon processing, including pathways for fermentation and methanogenesis. Here, we performed a pilot study using ultrahigh throughput Illumina HiSeq sequencing of reverse transcribed messenger RNA to obtain a detailed overview of active metabolic pathways and responsible organisms in up to 70 cm deep permafrost soils at a moist acidic tundra location in Arctic Alaska. The transcriptional response of the permafrost microbial community was compared before and after 11 days of thaw. In general, the transcriptional profile under frozen conditions suggests a dominance of stress responses, survival strategies, and maintenance processes, whereas upon thaw a rapid enzymatic response to decomposing soil organic matter (SOM) was observed. Bacteroidetes, Firmicutes, ascomycete fungi, and methanogens were responsible for largest transcriptional response upon thaw. Transcripts indicative of heterotrophic methanogenic pathways utilizing acetate, methanol, and methylamine were found predominantly in the permafrost table after thaw. Furthermore, transcripts involved in acetogenesis were expressed exclusively after thaw suggesting that acetogenic bacteria are a potential source of acetate for acetoclastic methanogenesis in freshly thawed permafrost. Metatranscriptomics is shown here to be a useful approach for inferring the activity of permafrost microbes that has potential to improve our understanding of permafrost SOM bioavailability and biogeochemical mechanisms contributing to greenhouse gas emissions as a result of permafrost thaw.

Methanoculleus sediminis sp. nov., a methanogen from sediments near a submarine mud volcano.

PubMed

Chen, Sheng-Chung; Chen, Mei-Fei; Lai, Mei-Chin; Weng, Chieh-Yin; Wu, Sue-Yao; Lin, Saulwood; Yang, Tsanyao F; Chen, Po-Chun

2015-07-01

A mesophilic, hydrogenotrophic methanogen, strain S3Fa(T), was isolated from sediments collected by Ocean Researcher I cruise ORI-934 in 2010 near the submarine mud volcano MV4 located at the upper slope of south-west Taiwan. The methanogenic substrates utilized by strain S3Fa(T) were formate and H2/CO2 but not acetate, secondary alcohols, methylamines, methanol or ethanol. Cells of strain S3Fa(T) were non-motile, irregular cocci, 0.5-1.0 μm in diameter. The surface-layer protein showed an Mr of 128,000.The optimum growth conditions were 37 °C, pH 7.1 and 0.17 M NaCl. The DNA G+C content of the genome of strain S3Fa(T) was 62.3 mol%. Phylogenetic analysis revealed that strain S3Fa(T) was most closely related to Methanoculleus marisnigri JR1(T) (99.3% 16S rRNA gene sequence similarity). Genome relatedness between strain S3Fa(T) and Methanoculleus marisnigri JR1(T) was computed using both genome-to-genome distance analysis (GGDA) and average nucleotide identity (ANI) with values of 46.3-55.5% and 93.08%, respectively. Based on morphological, phenotypic, phylogenetic and genomic relatedness data, it is evident that strain S3Fa(T) represents a novel species of the genus Methanoculleus, for which the name Methanoculleus sediminis sp. nov. is proposed. The type strain is S3Fa(T) ( = BCRC AR10044(T) = DSM 29354(T)).

A liquid chromatography-electrospray ionization-tandem mass spectrometry study of ethanolamines in high salinity industrial wastewaters.

PubMed

Campo, Pablo; Suidan, Makram T; Chai, Yunzhou; Davis, John

2010-01-15

The detection and quantitation of four ethanolamines, tris(2-hydroxyethyl)amine (triethanolamine, TEA), N,N-bis(2-hydroxyethyl)methylamine (methyldiethanolamine, MDEA), N-(2-aminoethyl)ethanolamine (AEA), and N,N-diethylethanolamine (DEA), were achieved in wastewaters from two aerobic activated sludge bioreactors located in an industrial wastewater treatment plant. The streams had salt concentrations of approximately 3% and 7% by weight in Reactor 1 and Reactor 2, respectively. The use of liquid chromatography-electrospray ionization-tandem mass spectrometry avoided the need for some sample preparation steps such as extraction, concentration, and derivatization. Ion suppression in the electrospray, attributable to the presence of sodium clusters, was attenuated by a 10-fold dilution of the wastewaters with acetonitrile. A matrix-matched calibration model averted other potential interferences. For the compounds analyzed in selected reaction monitoring mode (TEA, MDEA, and DEA), the calibration curves presented linearity in a range of 10-1000microg/L with corresponding detection limits ranging from 2 to 11microg/L, depending upon the specific analyte and aqueous matrix. AEA was calibrated in selected ion monitoring mode (100-1000microg/L), with corresponding detection limits in the two wastewaters of 74.6 and 85.3microg/L, respectively. Overall good precision (<10%) and accuracy (97-110%) were achieved for both matrices, which fell within-laboratory reproducibility. Finally, the amines were introduced into six mixed liquor samples from both reactors and quantified following the reported protocol. Again, recoveries were close to 100% with a relative standard deviation of less than 10% in all cases.

Coherent Experimental and Simulation Approach To Explore the Underlying Mechanism of Denaturation of Stem Bromelain in Osmolytes.

PubMed

Rani, Anjeeta; Taha, Mohamed; Venkatesu, Pannuru; Lee, Ming-Jer

2017-07-13

Characterization of a protein in the context of its environment is of crucial importance for a complete understanding of its function. Although biophysical techniques provide powerful tools for studying the stability and activity of the enzyme in the presence of various cosolvents, an approach of combining both experimental techniques and molecular dynamic (MD) simulations may lead to the mechanistic insight into the interactions governing the stability of an enzyme. The knowledge of these interactions can be further utilized for range of modifications in the wild form of an enzyme for various pharmaceutical applications. Herein, we employed florescence, UV-visible, circular dichroism (CD), dynamic light scattering (DLS) study, and MD simulations for comprehensive understanding of stem bromelain (BM) in the presence of betaine, sarcosine, arginine, and proline. The thermal stability of BM in the presence of 1 M of osmolytes is found to be in order: proline > betaine > buffer > arginine > sarcosine. BM gets more preferentially hydrated in the presence of betaine and proline than in sarcosine and arginine. Nonetheless, MD simulations suggest that betaine, sarcosine, and arginine at 1 M interact with the active site of BM through H-bonding except proline which are responsible for more disruption of active site. The distances between the catalytic site residues are 1.6, 1.9, 4.3, 5.0, and 6.2 Å for BM in proline, buffer, betaine, arginine, and sarcosine at 1 M, respectively. To the best of our knowledge, this is the first report on detailed unequivocal evidence of denaturation and deactivation of BM in the presence of methylamines and amino acids.

Bacillus subtilis yckG and yckF Encode Two Key Enzymes of the Ribulose Monophosphate Pathway Used by Methylotrophs, and yckH Is Required for Their Expression

PubMed Central

Yasueda, Hisashi; Kawahara, Yoshio; Sugimoto, Shin-ichi

1999-01-01

The ribulose monophosphate (RuMP) pathway is one of the metabolic pathways for the synthesis of compounds containing carbon-carbon bonds from one-carbon units and is found in many methane- and methanol-utilizing bacteria, which are known as methylotrophs. The characteristic enzymes of this pathway are 3-hexulose-6-phosphate synthase (HPS) and 6-phospho-3-hexuloisomerase (PHI), neither of which was thought to exist outside methylotrophs. However, the presumed yckG gene product (YckG) of Bacillus subtilis shows a primary structure similar to that of methylotroph HPS (F. Kunst et al., Nature 390:249–256, 1997). We have also investigated the sequence similarity between the yckF gene product (YckF) and methylotroph PHI (Y. Sakai, R. Mitsui, Y. Katayama, H. Yanase, and N. Kato, FEMS Microbiol. Lett. 176:125–130, 1999) and found that the yckG and yckF genes of B. subtilis express enzymatic activities of HPS and PHI, respectively. Both of these activities were concomitantly induced in B. subtilis by formaldehyde, with induction showing dependence on the yckH gene, but were not induced by methanol, formate, or methylamine. Disruption of either gene caused moderate sensitivity to formaldehyde, suggesting that these enzymes may act as a detoxification system for formaldehyde in B. subtilis. In conclusion, we found an active yckG (for HPS)-yckF (for PHI) gene structure (now named hxlA-hxlB) in a nonmethylotroph, B. subtilis, which inherently preserves the RuMP pathway. PMID:10572115

[Regioselectivity in the dehydrogenation of substituted ethylenediamines as nicotine models].

PubMed

Möhrle, H; Berlitz, J

2009-09-01

The direction of dehydrogenation with Hg(II)-EDTA of 2-substituted pyrrolidines and piperidines is examined at the model substances 1-4 featuring a N-(2-amino-2-phenylethyl) substituent, which is able to capture an iminium intermediate. Compounds 1-4 represent mixtures of diastereomers; the separation of 2-phenylpyrrolidine derivative 1 into the racemic diastereomers 1A and 1B is achieved. The oxidation of 1 results in a double dehydrogenation to give the pyrrolizidine amidine 5, which, depending on the work-up conditions is partially hydrolyzed to pyrrolidone 6. The dehydrogenation of the 2-phenylpiperidine compound 2 yields as sole product nearly quantitatively the cyclic amidine 10, which shows no hydrolysis due a minor strain compared to 5. Thus, in both reactions the primary intermediate is the less substituted iminium ion in 5- and 6-position, respectively. On the contrary, the Hg(II)-EDTA treatment of the 2-methylpyrrolidine 3 leads to an electron withdrawal with a different regioselectivity and gives predominantly rise to the angular methylaminal 14. To a minor amount, the azapyrrolizidine 12 is received from the 5-iminium precursor 11. In the oxidation of the 2-methylpiperidine 4, an essentially similar regioselectivity is observed. Besides the angular methylindolizidine 15 as main product, the indolizidine aminal resulting from the less substituted iminium intermediate is due to a favourable steric situation further oxidized to the cyclic amidine 16. The diastereomeric mixtures of the anellated imidazolines 5, 10 and 16 were transfered by boiling with Pd/C in toluene or with activated MnO2 in chloroform to the racemic imidazoles 19-21 in good yields.

Genetic and Phenotypic Comparison of Facultative Methylotrophy between Methylobacterium extorquens Strains PA1 and AM1

PubMed Central

Nayak, Dipti D.; Marx, Christopher J.

2014-01-01

Methylobacterium extorquens AM1, a strain serendipitously isolated half a century ago, has become the best-characterized model system for the study of aerobic methylotrophy (the ability to grow on reduced single-carbon compounds). However, with 5 replicons and 174 insertion sequence (IS) elements in the genome as well as a long history of domestication in the laboratory, genetic and genomic analysis of M. extorquens AM1 face several challenges. On the contrary, a recently isolated strain - M. extorquens PA1- is closely related to M. extorquens AM1 (100% 16S rRNA identity) and contains a streamlined genome with a single replicon and only 20 IS elements. With the exception of the methylamine dehydrogenase encoding gene cluster (mau), genes known to be involved in methylotrophy are well conserved between M. extorquens AM1 and M. extorquens PA1. In this paper we report four primary findings regarding methylotrophy in PA1. First, with a few notable exceptions, the repertoire of methylotrophy genes between PA1 and AM1 is extremely similar. Second, PA1 grows faster with higher yields compared to AM1 on C1 and multi-C substrates in minimal media, but AM1 grows faster in rich medium. Third, deletion mutants in PA1 throughout methylotrophy modules have the same C1 growth phenotypes observed in AM1. Finally, the precision of our growth assays revealed several unexpected growth phenotypes for various knockout mutants that serve as leads for future work in understanding their basis and generality across Methylobacterium strains. PMID:25232997

Evidence for Methyl-Compound-Activated Life in Coal Bed System 2 km Below Sea Floor

NASA Astrophysics Data System (ADS)

Trembath-reichert, E.; Morono, Y.; Dawson, K.; Wanger, G.; Bowles, M.; Heuer, V.; Hinrichs, K. U.; Inagaki, F.; Orphan, V. J.

2014-12-01

IODP Expedition 337 set the record for deepest marine scientific drilling down to 2.4 kmbsf. This cruise also had the unique opportunity to retrieve deep cores from the Shimokita coal bed system in Japan with the aseptic and anaerobic conditions necessary to look for deep life. Onboard scientists prepared nearly 1,700 microbiology samples shared among five different countries to study life in the deep biosphere. Samples spanned over 1 km in sampling depths and include representatives of shale, sandstone, and coal lithologies. Findings from previous IODP and deep mine expeditions suggest the genetic potential for methylotrophy in the deep subsurface, but it has yet to be observed in incubations. A subset of Expedition 337 anoxic incubations were prepared with a range of 13C-methyl substrates (methane, methylamine, and methanol) and maintained near in situ temperatures. To observe 13C methyl compound metabolism over time, we monitored the δ13C of the dissolved inorganic carbon (by-product of methyl compound metabolism) over a period of 1.5 years. Elemental analysis (EA), ion chromatograph (IC), 13C volatile fatty acid (VFA), and mineral-associated microscopy data were also collected to constrain initial and endpoint conditions in these incubations. Our geochemical evidence suggests that the coal horizon incubated with 13C-methane showed the highest activity of all methyl incubations. This provides the first known observation of methane-activated metabolism in the deep biosphere, and suggests there are not only active cells in the deeply buried terrigenous coal bed at Shimokita, but the presence of a microbial community activated by methylotrophic compounds.

The transcriptional response of microbial communities in thawing Alaskan permafrost soils

PubMed Central

Coolen, Marco J. L.; Orsi, William D.

2015-01-01

Thawing of permafrost soils is expected to stimulate microbial decomposition and respiration of sequestered carbon. This could, in turn, increase atmospheric concentrations of greenhouse gasses, such as carbon dioxide and methane, and create a positive feedback to climate warming. Recent metagenomic studies suggest that permafrost has a large metabolic potential for carbon processing, including pathways for fermentation and methanogenesis. Here, we performed a pilot study using ultrahigh throughput Illumina HiSeq sequencing of reverse transcribed messenger RNA to obtain a detailed overview of active metabolic pathways and responsible organisms in up to 70 cm deep permafrost soils at a moist acidic tundra location in Arctic Alaska. The transcriptional response of the permafrost microbial community was compared before and after 11 days of thaw. In general, the transcriptional profile under frozen conditions suggests a dominance of stress responses, survival strategies, and maintenance processes, whereas upon thaw a rapid enzymatic response to decomposing soil organic matter (SOM) was observed. Bacteroidetes, Firmicutes, ascomycete fungi, and methanogens were responsible for largest transcriptional response upon thaw. Transcripts indicative of heterotrophic methanogenic pathways utilizing acetate, methanol, and methylamine were found predominantly in the permafrost table after thaw. Furthermore, transcripts involved in acetogenesis were expressed exclusively after thaw suggesting that acetogenic bacteria are a potential source of acetate for acetoclastic methanogenesis in freshly thawed permafrost. Metatranscriptomics is shown here to be a useful approach for inferring the activity of permafrost microbes that has potential to improve our understanding of permafrost SOM bioavailability and biogeochemical mechanisms contributing to greenhouse gas emissions as a result of permafrost thaw. PMID:25852660

Metabolic Profile and Root Development of Hypericum perforatum L. In vitro Roots under Stress Conditions Due to Chitosan Treatment and Culture Time.

PubMed

Brasili, Elisa; Miccheli, Alfredo; Marini, Federico; Praticò, Giulia; Sciubba, Fabio; Di Cocco, Maria E; Cechinel, Valdir Filho; Tocci, Noemi; Valletta, Alessio; Pasqua, Gabriella

2016-01-01

The responses of Hypericum perforatum root cultures to chitosan elicitation had been investigated through (1)H-NMR-based metabolomics associated with morpho-anatomical analyses. The root metabolome was influenced by two factors, i.e., time of culture (associated with biomass growth and related "overcrowding stress") and chitosan elicitation. ANOVA simultaneous component analysis (ASCA) modeling showed that these factors act independently. In response to the increase of biomass density over time, a decrease in the synthesis of isoleucine, valine, pyruvate, methylamine, etanolamine, trigonelline, glutamine and fatty acids, and an increase in the synthesis of phenolic compounds, such as xanthones, epicatechin, gallic, and shikimic acid were observed. Among the xanthones, brasilixanthone B has been identified for the first time in chitosan-elicited root cultures of H. perforatum. Chitosan treatment associated to a slowdown of root biomass growth caused an increase in DMAPP and a decrease in stigmasterol, shikimic acid, and tryptophan levels. The histological analysis of chitosan-treated roots revealed a marked swelling of the root apex, mainly due to the hypertrophy of the first two sub-epidermal cell layers. In addition, periclinal divisions in hypertrophic cortical cells, resulting in an increase of cortical layers, were frequently observed. Most of the metabolic variations as well as the morpho-anatomical alterations occurred within 72 h from the elicitation, suggesting an early response of H. perforatum roots to chitosan elicitation. The obtained results improve the knowledge of the root responses to biotic stress and provide useful information to optimize the biotechnological production of plant compounds of industrial interest.

Metabolic Profile and Root Development of Hypericum perforatum L. In vitro Roots under Stress Conditions Due to Chitosan Treatment and Culture Time

PubMed Central

Brasili, Elisa; Miccheli, Alfredo; Marini, Federico; Praticò, Giulia; Sciubba, Fabio; Di Cocco, Maria E.; Cechinel, Valdir Filho; Tocci, Noemi; Valletta, Alessio; Pasqua, Gabriella

2016-01-01

The responses of Hypericum perforatum root cultures to chitosan elicitation had been investigated through 1H-NMR-based metabolomics associated with morpho-anatomical analyses. The root metabolome was influenced by two factors, i.e., time of culture (associated with biomass growth and related “overcrowding stress”) and chitosan elicitation. ANOVA simultaneous component analysis (ASCA) modeling showed that these factors act independently. In response to the increase of biomass density over time, a decrease in the synthesis of isoleucine, valine, pyruvate, methylamine, etanolamine, trigonelline, glutamine and fatty acids, and an increase in the synthesis of phenolic compounds, such as xanthones, epicatechin, gallic, and shikimic acid were observed. Among the xanthones, brasilixanthone B has been identified for the first time in chitosan-elicited root cultures of H. perforatum. Chitosan treatment associated to a slowdown of root biomass growth caused an increase in DMAPP and a decrease in stigmasterol, shikimic acid, and tryptophan levels. The histological analysis of chitosan-treated roots revealed a marked swelling of the root apex, mainly due to the hypertrophy of the first two sub-epidermal cell layers. In addition, periclinal divisions in hypertrophic cortical cells, resulting in an increase of cortical layers, were frequently observed. Most of the metabolic variations as well as the morpho-anatomical alterations occurred within 72 h from the elicitation, suggesting an early response of H. perforatum roots to chitosan elicitation. The obtained results improve the knowledge of the root responses to biotic stress and provide useful information to optimize the biotechnological production of plant compounds of industrial interest. PMID:27148330

On-board Measurement of HCN and NH3 Emissions from Vehicles During Real-World Driving

NASA Astrophysics Data System (ADS)

Moss, J. A.; Baum, M. M.

2013-12-01

Emission control systems in light-duty motor vehicles have played an important role in improving regional air quality by dramatically reducing the concentration of criteria pollutants (carbon monoxide, hydrocarbons, and nitrogen oxides) in exhaust emissions. Unintended side-reactions occurring on the surface of three-way catalysts can, however, lead to emission of non-criteria pollutants such as ammonia (NH3) and hydrogen cyanide (HCN). A pair of spectrometers based on tunable diode lasers (TDL) emitting in the near-infrared (1529 nm) and mid-infrared (2975 nm) have been developed for determination of HCN and acetylene (C2H2) emission rates from light-duty motor vehicles in real-time, while driving. Both spectrometers have been evaluated extensively using standard gas mixtures in the laboratory and exhaust from idling and moving vehicles. The TDL spectrometers were incorporated into an on-board instrument suite containing instrumentation for measurement of CO2, HCN, C2H2, NH3 and amines, and exhaust flow rate. On-board measurements were carried out on a fleet of ten vehicles driving a 30 minute circuit representative of real-world urban driving conditions. These measurements afforded emission factors for NH3 (194 × 147 mg km-1) and HCN (3.33 × 3.61 mg km-1), as well as the first report of methylamine emission factors, 0.70 × 0.61 mg km-1. Emissions of both amines were highly correlated (R2 = 0.95). The temporally-resolved TDL spectrometer measurements indicate that the highest HCN and C2H2 emissions occur during specific emission modes that are a function of driving conditions.

Microbial Successions and Metabolite Changes during Fermentation of Salted Shrimp (Saeu-Jeot) with Different Salt Concentrations

PubMed Central

Lee, Se Hee; Jung, Ji Young; Jeon, Che Ok

2014-01-01

To investigate the effects of salt concentration on saeu-jeot (salted shrimp) fermentation, four sets of saeu-jeot samples with 20%, 24%, 28%, and 32% salt concentrations were prepared, and the pH, bacterial and archaeal abundances, bacterial communities, and metabolites were monitored during the entire fermentation period. Quantitative PCR showed that Bacteria were much more abundant than Archaea in all saeu-jeot samples, suggesting that bacterial populations play more important roles than archaeal populations even in highly salted samples. Community analysis indicated that Vibrio, Photobacterium, Psychrobacter, Pseudoalteromonas, and Enterovibrio were identified as the initially dominant genera, and the bacterial successions were significantly different depending on the salt concentration. During the early fermentation period, Salinivibrio predominated in the 20% salted samples, whereas Staphylococcus, Halomonas, and Salimicrobium predominated in the 24% salted samples; eventually, Halanaerobium predominated in the 20% and 24% salted samples. The initially dominant genera gradually decreased as the fermentation progressed in the 28% and 32% salted samples, and eventually Salimicrobium became predominant in the 28% salted samples. However, the initially dominant genera still remained until the end of fermentation in the 32% salted samples. Metabolite analysis showed that the amino acid profile and the initial glycerol increase were similar in all saeu-jeot samples regardless of the salt concentration. After 30–80 days of fermentation, the levels of acetate, butyrate, and methylamines in the 20% and 24% salted samples increased with the growth of Halanaerobium, even though the amino acid concentrations steadily increased until approximately 80–107 days of fermentation. This study suggests that a range of 24–28% salt concentration in saeu-jeot fermentation is appropriate for the production of safe and tasty saeu-jeot. PMID:24587230

Binding of Soluble Yeast β-Glucan to Human Neutrophils and Monocytes is Complement-Dependent

PubMed Central

Bose, Nandita; Chan, Anissa S. H.; Guerrero, Faimola; Maristany, Carolyn M.; Qiu, Xiaohong; Walsh, Richard M.; Ertelt, Kathleen E.; Jonas, Adria Bykowski; Gorden, Keith B.; Dudney, Christine M.; Wurst, Lindsay R.; Danielson, Michael E.; Elmasry, Natalie; Magee, Andrew S.; Patchen, Myra L.; Vasilakos, John P.

2013-01-01

The immunomodulatory properties of yeast β-1,3/1,6 glucans are mediated through their ability to be recognized by human innate immune cells. While several studies have investigated binding of opsonized and unopsonized particulate β-glucans to human immune cells mainly via complement receptor 3 (CR3) or Dectin-1, few have focused on understanding the binding characteristics of soluble β-glucans. Using a well-characterized, pharmaceutical-grade, soluble yeast β-glucan, this study evaluated and characterized the binding of soluble β-glucan to human neutrophils and monocytes. The results demonstrated that soluble β-glucan bound to both human neutrophils and monocytes in a concentration-dependent and receptor-specific manner. Antibodies blocking the CD11b and CD18 chains of CR3 significantly inhibited binding to both cell types, establishing CR3 as the key receptor recognizing the soluble β-glucan in these cells. Binding of soluble β-glucan to human neutrophils and monocytes required serum and was also dependent on incubation time and temperature, strongly suggesting that binding was complement-mediated. Indeed, binding was reduced in heat-inactivated serum, or in serum treated with methylamine or in serum reacted with the C3-specific inhibitor compstatin. Opsonization of soluble β-glucan was demonstrated by detection of iC3b, the complement opsonin on β-glucan-bound cells, as well as by the direct binding of iC3b to β-glucan in the absence of cells. Binding of β-glucan to cells was partially inhibited by blockade of the alternative pathway of complement, suggesting that the C3 activation amplification step mediated by this pathway also contributed to binding. PMID:23964276

Thermal Stability-Enhanced and High-Efficiency Planar Perovskite Solar Cells with Interface Passivation.

PubMed

Zhang, Weihai; Xiong, Juan; Jiang, Li; Wang, Jianying; Mei, Tao; Wang, Xianbao; Gu, Haoshuang; Daoud, Walid A; Li, Jinhua

2017-11-08

As the electron transport layer (ETL) of perovskite solar cells, oxide semiconductor zinc oxide (ZnO) has been attracting great attention due to its relatively high mobility, optical transparency, low-temperature fabrication, and good environment stability. However, the nature of ZnO will react with the patron on methylamine, which would deteriorate the performance of cells. Although many methods, including high-temperature annealing, doping, and surface modification, have been studied to improve the efficiency and stability of perovskite solar cells with ZnO ETL, devices remain relatively low in efficiency and stability. Herein, we adopted a novel multistep annealing method to deposit a porous PbI 2 film and improved the quality and uniformity of perovskite films. The cells with ZnO ETL were fabricated at the temperature of <150 °C by solution processing. The power conversion efficiency (PCE) of the device fabricated by the novel annealing method increased from 15.5 to 17.5%. To enhance the thermal stability of CH 3 NH 3 PbI 3 (MAPbI 3 ) on the ZnO surface, a thin layer of small molecule [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) was inserted between the ZnO layer and perovskite film. Interestingly, the PCE of PCBM-passivated cells could reach nearly 19.1%. To our best knowledge, this is the highest PCE value of ZnO-based perovskite solar cells until now. More importantly, PCBM modification could effectively suppress the decomposition of MAPbI 3 and improve the thermal stability of cells. Therefore, the ZnO is a promising candidate of electron transport material for perovskite solar cells in future applications.

Competition Between Two Large-Amplitude Motion Models: New Hybrid Hamiltonian Versus Old Pure-Tunneling Hamiltonian

NASA Astrophysics Data System (ADS)

Kleiner, Isabelle; Hougen, Jon T.

2017-06-01

In this talk we report on our progress in trying to make the hybrid Hamiltonian competitive with the pure-tunneling Hamiltonian for treating large-amplitude motions in methylamine. A treatment using the pure-tunneling model has the advantages of: (i) requiring relatively little computer time, (ii) working with relatively uncorrelated fitting parameters, and (iii) yielding in the vast majority of cases fits to experimental measurement accuracy. These advantages are all illustrated in the work published this past year on a gigantic v_{t} = 1 data set for the torsional fundamental band in methyl amine. A treatment using the hybrid model has the advantages of: (i) being able to carry out a global fit involving both v_{t} = 0 and v_{t} = 1 energy levels and (ii) working with fitting parameters that have a clearer physical interpretation. Unfortunately, a treatment using the hybrid model has the great disadvantage of requiring a highly correlated set of fitting parameters to achieve reasonable fitting accuracy, which complicates the search for a good set of molecular fitting parameters and a fit to experimental accuracy. At the time of writing this abstract, we have been able to carry out a fit with J up to 15 that includes all available infrared data in the v_{t} = 1-0 torsional fundamental band, all ground-state microwave data with K up to 10 and J up to 15, and about a hundred microwave lines within the v_{t} = 1 torsional state, achieving weighted root-mean-square (rms) deviations of about 1.4, 2.8, and 4.2 for these three categories of data. We will give an update of this situation at the meeting. I. Gulaczyk, M. Kreglewski, V.-M. Horneman, J. Mol. Spectrosc., in Press (2017).

Identification of (2-aminopropyl)indole positional isomers in forensic samples.

PubMed

Scott, Kenneth R; Power, John D; McDermott, Seán D; O'Brien, John E; Talbot, Brian N; Barry, Michael G; Kavanagh, Pierce V

2014-01-01

In 2012, 5-(2-aminopropyl)indole (5-API, 5-IT) was reported by Norwegian authorities to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) via the Early Warning System (EWS). The 3- isomer, 3-(2-aminopropyl)indole (3-API, AMT, alpha-methyltryptamine), has been available on the recreational drugs market for a somewhat longer time, having first been reported to the EMCDDA by Finnish authorities in 2001. Both isomers are available from online vendors of 'legal highs'. Recently, three forensic drug cases (two tablets and one powder) were presented for routine analysis and the active constituent was tentatively identified as an API isomer. The six positional isomers (2-, 3-, 4-, 5-, 6- and 7-(2-aminopropyl)indoles) were synthesized and analyses by a combination gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS) showed that these could be readily discriminated thus facilitating the identification of 3-API in the tablets and 5-API in the powder. With exception of 5- and 6-APIs, which co-eluted, it was found possible to separate the isomers by GC without derivatization. LC separation also proved to be a feasible method for the discrimination of the isomers. Although the 2- and 7- isomers were not fully resolved by LC, it was found possible to distinguish them using their product ion spectra as the 2- isomer produced the m/z 132 fragment ion formed by loss of vinylamine, whereas the 7- isomer formed m/z 158 through loss of methylamine. In the synthesis 2-API, a novel tricyclic by-product was formed in an annulation reaction where the reaction solvent, tetrahydrofuran, was incorporated into the molecule. Copyright © 2013 John Wiley & Sons, Ltd.

Characterization of labelling and de-labelling reagents for detection and recovery of tyrosine residue in peptide.

PubMed

Toyo'oka, Toshimasa; Mantani, Tomomi; Kato, Masaru

2003-01-01

This paper characterized the labelling and de-labelling reagents for reversible labelling of tyrosine (Tyr)-containing peptide, which involves detection and recovery. The phenolic hydroxyl group (-OH) in Tyr structure reacted with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), and 1-fluoro-2,4-dinitrobenzene (DNFB) under mild conditions at room temperature at pH 9.3. The labels in the resulting derivatives were removed with the treatment of nucleophiles, such as thiols (cysteine, N-acetyl-L-cysteine and dithiothreitol) and amines (dimethylamine, methylamine, diethylamine, ethylamine and pyrrolidine). The de-labelling reactions of NBD-labelled N-acetyl-L-tyrosine (N-AcTyr) with the nucleophiles produced N-AcTyr, accompanied by NBD-nucleophile. Although DBD-F and DNFB also successfully labeled the -OH group in N-AcTyr, the efficiency of Cbond;O bond cleavage and recovery of N-AcTyr by the nucleophiles was relatively low compared with NBD-label. Among the de-labelling reagents, N-acetyl-L-cysteine and dimethylamine were recommended for the elimination of NBD moiety, with respect to the reaction rate, the side reaction, and the yield of recovery. The proposed procedure, which includes the labelling with NBD-F and the removal of NBD moiety by the nucleophiles, was successfully applied to the reversible labelling of N-terminal amine-blocked peptides, i.e. N-AcTyr-Val-Gly, Z-Glu-Tyr, Z-Phe-Tyr, N-Formyl-Met-Leu-Tyr, and N-AcArg-Pro-Pro-Gly-Phe-Ser-Pro-Tyr-Arg. Copyright 2003 John Wiley & Sons, Ltd.

Genetic resources for methane production from biomass described with the Gene Ontology.

PubMed

Purwantini, Endang; Torto-Alalibo, Trudy; Lomax, Jane; Setubal, João C; Tyler, Brett M; Mukhopadhyay, Biswarup

2014-01-01

Methane (CH4) is a valuable fuel, constituting 70-95% of natural gas, and a potent greenhouse gas. Release of CH4 into the atmosphere contributes to climate change. Biological CH4 production or methanogenesis is mostly performed by methanogens, a group of strictly anaerobic archaea. The direct substrates for methanogenesis are H2 plus CO2, acetate, formate, methylamines, methanol, methyl sulfides, and ethanol or a secondary alcohol plus CO2. In numerous anaerobic niches in nature, methanogenesis facilitates mineralization of complex biopolymers such as carbohydrates, lipids and proteins generated by primary producers. Thus, methanogens are critical players in the global carbon cycle. The same process is used in anaerobic treatment of municipal, industrial and agricultural wastes, reducing the biological pollutants in the wastes and generating methane. It also holds potential for commercial production of natural gas from renewable resources. This process operates in digestive systems of many animals, including cattle, and humans. In contrast, in deep-sea hydrothermal vents methanogenesis is a primary production process, allowing chemosynthesis of biomaterials from H2 plus CO2. In this report we present Gene Ontology (GO) terms that can be used to describe processes, functions and cellular components involved in methanogenic biodegradation and biosynthesis of specialized coenzymes that methanogens use. Some of these GO terms were previously available and the rest were generated in our Microbial Energy Gene Ontology (MENGO) project. A recently discovered non-canonical CH4 production process is also described. We have performed manual GO annotation of selected methanogenesis genes, based on experimental evidence, providing "gold standards" for machine annotation and automated discovery of methanogenesis genes or systems in diverse genomes. Most of the GO-related information presented in this report is available at the MENGO website (http://www.mengo.biochem.vt.edu/).

Stimulation of pyruvate transport in metabolizing mitochondria through changes in the transmembrane pH gradient induced by glucagon treatment of rats.

PubMed

Halestrap, A P

1978-06-15

Glucagon treatment of rats allowed the isolation of liver mitochondria with enhanced rates of pyruvate metabolism measured in either sucrose or KCl media. No change in the activity of the pyruvate carrier itself was apparent, but under metabolizing conditions, use of the inhibitor of pyruvate transport, alpha-cyano-4-hydroxycinnamate, demonstrated that pyruvate transport limited the rate of pyruvate metabolism. The maximum rate of transport under metabolizing conditions was enhanced by glucagon treatment. Problems involved in measuring the transmembrane pH gradient under metabolizing conditions are discussed and a variety of techniques are used to estimate the matrix pH. From the distribution of methylamine, ammonia and D-lactate and the Ki for inhibition by alpha-cyano-4-hydroxycinnamate it is concluded that the matrix is more acid than the medium and that the pH of the matrix rises after glucagon treatment. The increase in matrix pH stimulates pyruvate transport. The membrane potential, ATP concentration and O2 uptake were also increased under metabolizing conditions in glucagon-treated mitochondria. These changes were correlated with a stimulation of the respiratory chain which can be observed in uncoupled mitochondria [Yamazaki (1975) J. Biol. Chem. 250, 7924--7930]. The mitochondrial Mg2+ content (mean +/- S.E.M.) was increased from 38.8 +/- 1.2 (n = 26) to 47.5 +/- 2.0 (n = 26) ng-atoms/mg by glucagon and the K+ content from 126.7 +/- 10.3 (n = 19) ng-atoms/mg. This may represent a change in membrane potential induced by glucagon in vivo. The physiological significance of these results in the control of gluconeogenesis is discussed.

Expression and use of the green fluorescent protein as a reporter system in Legionella pneumophila.

PubMed

Köhler, R; Bubert, A; Goebel, W; Steinert, M; Hacker, J; Bubert, B

2000-01-01

The gene encoding the green fluorescent protein (GFP) was used as a reporter gene in Legionella pneumophila. To analyze GFP expression in Legionella, transcriptional fusions of gfp with the Legionella-specific mip (Macrophage Infectivity Potentiator) promoter (P(mip)) and the sod (SuperOxide Dismutase) promoter (P(sod)) derived from Listeria monocytogenes were constructed. Following transformation into the virulent L. pneumophila strain JR 32, strong GFP-mediated fluorescence was detected with both plasmids, although the sod promoter was associated with a 1ten-fold higher intensity. No fluorescence was observed in L. pneumophila transformed with the promoterless gfp gene. Comparison of fluorescence yields between various L. pneumophila strains that differ in their virulence characteristics and were transformed with the P(mip)-gfp carrying plasmid revealed no differences in GFP expression. Infection studies using Acanthamoeba castellanii as host and recombinant L. pneumophila strains carrying the P(mip)-gfp and P(sod)-gfp fusions indicated that the mip promoter was expressed when the bacteria replicated intracellularly. GFP expression was also used to monitor, in infected A. castellanii cells, the intracellular survival of, and incidence of host-cell killing by. L. pneumophila strains that vary in their virulence properties. As quantified by flow cytometry the highly virulent L. pneumophila strain Corby was twice as infectious to A. castellanii as the Philadelphia strain JR 32. Using the avirulent Philadelphia derivative 25D invasion but no intracellular multiplication was observed. In addition, we examined by flow cytometry the influence of cytochalasin D, cycloheximide, and methylamine on the uptake of Legionella by A. castellanii. In conclusion, gfp appears to be a convenient reporter gene whose expression in Legionella can be followed in real time and allows analysis of promoter activities in Legionella and monitoring of the infection process.

Sterol content in the artificial diet of Mythimna separata affects the metabolomics of Arma chinensis (Fallou) as determined by proton nuclear magnetic resonance spectroscopy.

PubMed

Guo, Yi; Liu, Chen-Xi; Zhang, Li-Sheng; Wang, Meng-Qing; Chen, Hong-Yin

2017-12-01

Insects cannot synthesize sterols and must obtain them from plants. Therefore, reducing plant sterol content or changing sterol type might be an effective pest control strategy. However, the impacts of these changes on pests' natural predators remain unknown. Here, we fed artificial diets with reduced sterol content to Mythimna separata (Walker) (Lepidoptera: Noctuidae) and investigated the effects on its natural predator, Arma chinensis (Fallou) (Hemiptera: Pentatomidae). Reduced sterol content in M. separata (MS1, MS2, and MS5) was achieved by feeding them artificial diets prepared from a feed base subjected to one, two, or five cycles of sterol extractions, respectively. The content of most substances increased in A. chinensis (AC) groups feeding on MS2 and MS5. The content of eight substances (alanine, betaine, dimethylamine, fumarate, glutamine, glycine, methylamine, and sarcosine) differed significantly between the control (AC0) and treated (AC1, AC2, and AC5) groups. Metabolic profiling revealed that only AC5 was significantly distinct from AC0; the major substances contributing to this difference were maltose, glucose, tyrosine, proline, O-phosphocholine, glutamine, allantoin, lysine, valine, and glutamate. Furthermore, only two metabolic pathways, that is, nicotinate and nicotinamide metabolism and ubiquinone and other terpenoid-quinone biosynthesis, differed significantly between AC1 and AC5 and the control, albeit with an impact value of zero. Thus, the sterol content in the artificial diet fed to M. separata only minimally affected the metabolites and metabolic pathways of its predator A. chinensis, suggesting that A. chinensis has good metabolic self-regulation with high resistance to sterol content changes. © 2017 Wiley Periodicals, Inc.

Allosteric modulation of semicarbazide-sensitive amine oxidase activities in vitro by imidazoline receptor ligands

PubMed Central

Holt, Andrew; Wieland, Barbara; Baker, Glen B

2004-01-01

Evidence indicates that imidazoline I2 binding sites (I2BSs) are present on monoamine oxidase (MAO) and on soluble (plasma) semicarbazide-sensitive amine oxidase enzymes. The binding site on MAO has been described as a modulatory site, although no effects on activity are thought to have been observed as a result of ligands binding to these sites. We examined the effects in vitro of several imidazoline binding site ligands on activities of bovine plasma amine oxidase (BPAO) and porcine kidney diamine oxidase (PKDAO) in a spectrophotometric protocol. While both enzymes were inhibited at high concentrations of all ligands, clonidine, cirazoline and oxymetazoline were seen, at lower concentrations, to increase activity of BPAO versus benzylamine, but not of PKDAO versus putrescine. This effect was substrate dependent, with mixed or biphasic inhibition of spermidine, methylamine, p-tyramine and β-phenylethylamine oxidation observed at cirazoline concentrations that increased benzylamine oxidation. With benzylamine as substrate, clonidine decreased KM (EC50 8.82 μM, Emax 75.1% of control) and increased Vmax (EC50 164.6 μM, Emax 154.1% of control). Cirazoline decreased Vmax (EC50 2.15 μM, Emax 91.4% of control), then decreased KM (EC50 5.63 μM, Emax 42.6% of control) and increased Vmax (EC50 49.0 μM, Emax 114.4% of decreased Vmax value). Data for clonidine fitted a mathematical model for two-site nonessential activation plus linear intersecting noncompetitive inhibition. Data for cirazoline were consistent with involvement of a fourth site. These results reveal an ability of imidazoline ligands to modulate BPAO kinetics allosterically. The derived mechanism may have functional significance with respect to modulation of MAO by I2BS ligands. PMID:15451775

Comparison of a preQ1 riboswitch aptamer in metabolite-bound and free states with implications for gene regulation.

PubMed

Jenkins, Jermaine L; Krucinska, Jolanta; McCarty, Reid M; Bandarian, Vahe; Wedekind, Joseph E

2011-07-15

Riboswitches are RNA regulatory elements that govern gene expression by recognition of small molecule ligands via a high affinity aptamer domain. Molecular recognition can lead to active or attenuated gene expression states by controlling accessibility to mRNA signals necessary for transcription or translation. Key areas of inquiry focus on how an aptamer attains specificity for its effector, the extent to which the aptamer folds prior to encountering its ligand, and how ligand binding alters expression signal accessibility. Here we present crystal structures of the preQ(1) riboswitch from Thermoanaerobacter tengcongensis in the preQ(1)-bound and free states. Although the mode of preQ(1) recognition is similar to that observed for preQ(0), surface plasmon resonance revealed an apparent K(D) of 2.1 ± 0.3 nm for preQ(1) but a value of 35.1 ± 6.1 nm for preQ(0). This difference can be accounted for by interactions between the preQ(1) methylamine and base G5 of the aptamer. To explore conformational states in the absence of metabolite, the free-state aptamer structure was determined. A14 from the ceiling of the ligand pocket shifts into the preQ(1)-binding site, resulting in "closed" access to the metabolite while simultaneously increasing exposure of the ribosome-binding site. Solution scattering data suggest that the free-state aptamer is compact, but the "closed" free-state crystal structure is inadequate to describe the solution scattering data. These observations are distinct from transcriptional preQ(1) riboswitches of the same class that exhibit strictly ligand-dependent folding. Implications for gene regulation are discussed.

[Methylophaga murata sp. nov.: a haloalkaliphilic aerobic methylotroph from deteriorating marble].

PubMed

Doronina, N V; Li, Ts D; Ivanova, E G; Trotsenko, Iu A

2005-01-01

The haloalkaliphilic methylotrophic bacterium (strain Kr3) isolated from material scraped off the deteriorating marble of the Moscow Kremlin masonry has been found to be able to utilize methanol, methylamine, trimethylamine, and fructose as carbon and energy sources. Its cells are gram-negative motile rods multiplying by binary fission. Spores are not produced. The isolate is strictly aerobic and requires vitamin B12 and Na+ ions for growth. It is oxidase- and catalase-positive and reduces nitrates to nitrites. Growth occurs at temperatures between 0 and 42 degrees C (with the optimum temperatures being 20-32 degrees C), pH values between 6 and 11 (with the optimum at 8-9), and NaCl concentrations between 0.05 and 3 M (with the optimum at 0.5-1.5 M). The dominant cellular phospholipids are phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin. The major cellular fatty acids are palmitic (C16:0), palmitoleic (C16:1), and octadecenoic (C18:1) acids. The major ubiquinone is Q8. The isolate accumulates ectoine and glutamate, as well as a certain amount of sucrose, to function as osmoprotectants and synthesizes an exopolysaccharide composed of carbohydrate and protein components. It is resistant to heating at 70 degrees C, freezing, and drying; utilizes methanol, with the resulting production of formic acid, which is responsible for the marble-degrading activity of the isolate; and implements the 2-keto-3-deoxy-6-phosphogluconate variant of the ribulose monophosphate pathway. The G+C content of its DNA is 44.6 mol%. Based on 16S rRNA gene sequencing and DNA-DNA homology levels (23-41%) with neutrophilic and alkaliphilic methylobacteria from the genus Methylophaga, the isolate has been identified as a new species, Methylophaga murata (VKM B-2303T = NCIMB 13993T).

Activation of the ATP-ubiquitin-proteasome pathway in skeletal muscle of cachectic rats bearing a hepatoma

NASA Technical Reports Server (NTRS)

Baracos, V. E.; DeVivo, C.; Hoyle, D. H.; Goldberg, A. L.

1995-01-01

Rats implanted with Yoshida ascites hepatoma (YAH) show a rapid and selective loss of muscle protein due mainly to a marked increase (63-95%) in the rate of protein degradation (compared with rates in muscles of pair-fed controls). To define which proteolytic pathways contribute to this increase, epitrochlearis muscles from YAH-bearing and control rats were incubated under conditions that modify different proteolytic systems. Overall proteolysis in either group of rats was not affected by removal of Ca2+ or by blocking the Ca(2+)-dependent proteolytic system. Inhibition of lysosomal function with methylamine reduced proteolysis (-12%) in muscles from YAH-bearing rats, but not in muscles of pair-fed rats. When ATP production was also inhibited, the remaining accelerated proteolysis in muscles of tumor-bearing rats fell to control levels. Muscles of YAH-bearing rats showed increased levels of ubiquitin-conjugated proteins and a 27-kDa proteasome subunit in Western blot analysis. Levels of mRNA encoding components of proteolytic systems were quantitated using Northern hybridization analysis. Although their total RNA content decreased 20-38%, pale muscles of YAH-bearing rats showed increased levels of ubiquitin mRNA (590-880%) and mRNA for multiple subunits of the proteasome (100-215%). Liver, kidney, heart, and brain showed no weight loss and no change in these mRNA species. Muscles of YAH-bearing rats also showed small increases (30-40%) in mRNA for cathepsins B and D, but not for calpain I or heat shock protein 70. Our findings suggest that accelerated muscle proteolysis and muscle wasting in tumor-bearing rats result primarily from activation of the ATP-dependent pathway involving ubiquitin and the proteasome.

Genetic resources for methane production from biomass described with the Gene Ontology

PubMed Central

Purwantini, Endang; Torto-Alalibo, Trudy; Lomax, Jane; Setubal, João C.; Tyler, Brett M.; Mukhopadhyay, Biswarup

2014-01-01

Methane (CH4) is a valuable fuel, constituting 70–95% of natural gas, and a potent greenhouse gas. Release of CH4 into the atmosphere contributes to climate change. Biological CH4 production or methanogenesis is mostly performed by methanogens, a group of strictly anaerobic archaea. The direct substrates for methanogenesis are H2 plus CO2, acetate, formate, methylamines, methanol, methyl sulfides, and ethanol or a secondary alcohol plus CO2. In numerous anaerobic niches in nature, methanogenesis facilitates mineralization of complex biopolymers such as carbohydrates, lipids and proteins generated by primary producers. Thus, methanogens are critical players in the global carbon cycle. The same process is used in anaerobic treatment of municipal, industrial and agricultural wastes, reducing the biological pollutants in the wastes and generating methane. It also holds potential for commercial production of natural gas from renewable resources. This process operates in digestive systems of many animals, including cattle, and humans. In contrast, in deep-sea hydrothermal vents methanogenesis is a primary production process, allowing chemosynthesis of biomaterials from H2 plus CO2. In this report we present Gene Ontology (GO) terms that can be used to describe processes, functions and cellular components involved in methanogenic biodegradation and biosynthesis of specialized coenzymes that methanogens use. Some of these GO terms were previously available and the rest were generated in our Microbial Energy Gene Ontology (MENGO) project. A recently discovered non-canonical CH4 production process is also described. We have performed manual GO annotation of selected methanogenesis genes, based on experimental evidence, providing “gold standards” for machine annotation and automated discovery of methanogenesis genes or systems in diverse genomes. Most of the GO-related information presented in this report is available at the MENGO website (http://www.mengo.biochem.vt.edu/). PMID:25520705

Unusual Internal Rotation Coupling in the Microwave Spectrum of Pinacolone

NASA Astrophysics Data System (ADS)

Zhao, YueYue; Nguyen, Ha Vinh Lam; Stahl, Wolfgang; Hougen, Jon T.

2015-06-01

The molecular-beam Fourier-transform microwave spectrum of pinacolone (methyl tert-butyl ketone) has been measured in several regions between 2 and 40 GHz. Assignments of a large number of A and E transitions were confirmed by combination differences, but fits of the assigned spectrum using several torsion-rotation computer programs based on different models led to the unexpected conclusion that no existing program correctly captures the internal dynamics of this molecule. A second puzzle arose when it became clear that roughly half of the spectrum remained unassigned even after all predicted transitions were added to the assignment list. Quantum chemical calculations carried out at the MP2/6-311++G(d,p) level indicate that this molecule does not have a plane of symmetry at equilibrium, and that internal rotation of the light methyl group induces a large oscillatory motion of the heavy tert-butyl group from one side of the C_s saddle point to the other. The effect of this non-C_s equilibrium structure was modeled for J = 0 levels by a simple two-top torsional Hamiltonian, where magnitudes of the strong top-top coupling terms were determined directly from the ab initio two-dimensional potential surface. A plot of the resultant torsional levels on the same scale as a one-dimensional potential curve along the zig-zag path connecting the six (unequally spaced) minima bears a striking resemblance to the 1:2:1 splitting pattern of levels in an internal rotation problem with a six-fold barrier. A plot of the six minima closely resembles the potential surface for methylamine. This talk will focus on implications of these resemblances for future work.

The lumbrical muscle: a novel in situ system to evaluate adult skeletal muscle proteolysis and anticatabolic drugs for therapeutic purposes.

PubMed

Bergantin, Leandro Bueno; Figueiredo, Leonardo Bruno; Godinho, Rosely Oliveira

2011-12-01

The molecular regulation of skeletal muscle proteolysis and the pharmacological screening of anticatabolic drugs have been addressed by measuring tyrosine release from prepubertal rat skeletal muscles, which are thin enough to allow adequate in vitro diffusion of oxygen and substrates. However, the use of muscle at accelerated prepubertal growth has limited the analysis of adult muscle proteolysis or that associated with aging and neurodegenerative diseases. Here we established the adult rat lumbrical muscle (4/hindpaw; 8/rat) as a new in situ experimental model for dynamic measurement of skeletal muscle proteolysis. By incubating lumbrical muscles attached to their individual metatarsal bones in Tyrode solution, we showed that the muscle proteolysis rate of adult and aged rats (3-4 to 24 mo old) is 45-25% of that in prepubertal animals (1 mo old), which makes questionable the usual extrapolation of proteolysis from prepubertal to adult/senile muscles. While acute mechanical injury or 1- to 7-day denervation increased tyrosine release from adult lumbrical muscle by up to 60%, it was reduced by 20-28% after 2-h incubation with β-adrenoceptor agonists, forskolin or phosphodiesterase inhibitor IBMX. Using inhibitors of 26S-proteasome (MG132), lysosome (methylamine), or calpain (E64/leupeptin) systems, we showed that ubiquitin-proteasome is accountable for 40-50% of total lumbrical proteolysis of adult, middle-aged, and aged rats. In conclusion, the lumbrical model allows the analysis of muscle proteolysis rate from prepubertal to senile rats. By permitting eight simultaneous matched measurements per rat, the new model improves similar protocols performed in paired extensor digitorum longus (EDL) muscles from prepubertal rats, optimizing the pharmacological screening of drugs for anticatabolic purposes.

Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ13C Values of Methane Produced in Hypersaline Microbial Mats

PubMed Central

Nicholson, Brooke E.; Beaudoin, Claire S.; Detweiler, Angela M.; Bebout, Brad M.

2014-01-01

Methane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The δ13C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the δ13C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more 13C-depleted methane. Trimethylamine-amended samples produced lower methane δ13C values than the mat-amended samples. This difference in the δ13C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H2 concentrations and increased CO2/H2 methanogenesis. PMID:25239903

Benzylamine antihyperglycemic effect is abolished by AOC3 gene invalidation in mice but not rescued by semicarbazide-sensitive amine oxidase expression under the control of aP2 promoter.

PubMed

Grès, Sandra; Bour, Sandy; Valet, Philippe; Carpéné, Christian

2012-12-01

Semicarbazide-sensitive amine oxidase (SSAO) is a transmembrane enzyme that metabolizes primary amines from endogenous or dietary origin. SSAO is highly expressed in adipose, smooth muscle and endothelial cells. In each of these cell types, SSAO is implicated in different biological functions, such as glucose transport activation, extracellular matrix maturation and leucocyte extravasation, respectively. However, the physiological functions of SSAO and their involvement in pathogenesis remain uncompletely characterized. To better understand the role of adipose tissue SSAO, we investigated whether it was necessary and/or sufficient to produce the antihyperglycemic effect of the SSAO-substrate benzylamine, already reported in mice. Therefore, we crossed SSAO-deficient mice invalidated for AOC3 gene and transgenic mice expected to express human SSAO in an adipocyte-specific manner, under the control of aP2 promoter. The aP2-human AOC3 construct (aP2-hAOC3) was equally expressed in the adipose tissue of mice expressing or not the native murine form and almost absent in other tissues. However, the corresponding SSAO activity found in adipose tissue represented only 20 % that of control mice. As a consequence, the benzylamine antihyperglycemic effect observed during glucose tolerance test in control was abolished in AOC3-KO mice but not rescued in mice expressing aP2-hAOC3. The capacity of benzylamine or methylamine to activate glucose uptake in adipocytes exhibited parallel variations in the corresponding genotypes. Although the aP2-hAOC3 construct did not allow a total rescue of SSAO activity in adipose tissue, it could be assessed from our observations that adipocyte SSAO plays a pivotal role in the increased glucose tolerance promoted by pharmacological doses of benzylamine.

Dynamic changes in metabolic profiles of rats subchronically exposed to mequindox.

PubMed

Jiang, Limiao; Zhao, Xiuju; Huang, Chongyang; Lei, Hehua; Tang, Huiru; Wang, Yulan

2014-11-01

Mequindox is widely used as an antibacterial veterinary drug and a feeding additive for farm animals in China. Although its toxicity has been widely studied, little is known regarding the metabolic effects of subchronic exposure to mequindox, which is vital for the health of meat producing livestock. Here, we characterized the dose- and time-dependent metabolic alterations in female Wistar rats subchronically exposed to mequindox through dietary supplementation at the level of 40, 110 and 280 mg kg(-1) for 13 weeks, employing a NMR based metabonomics approach with supplementary information from serum clinical chemistry. We found that urinary metabolic profiles were significantly affected in all dosed groups during the supplementation period; plasma and hepatic metabolic profiles were significantly affected only in rats dosed with moderate and high levels of mequindox. We also observed a return to control levels, for the profiles of urine and liver, at all dose levels after a two weeks washout period. However, this was not the case for the metabolic profiles of plasma from rats dosed at high levels. At the molecular level, we showed that subchronic exposure to mequindox resulted in tricarboxylic acid cycle (TCA cycle) stimulation, suppression of glycolysis, and promotion of gluconeogenesis and lipid oxidation in rats. In addition, subchronic exposure to mequindox induced oxidative stress in rats. Furthermore, a disturbance of gut microbiota, manifested by alterations in the urinary excretion of hippurate, phenylacetylglycine, 3-(3-hydroxyphenyl)propionate, p-cresol glucuronide, methylamine, dimethylamine, and formate, was associated with mequindox exposure. The present study provided important holistic metabolic information on the effects of subchronic dosage of mequindox on rats, which is useful for evaluating the safety of mequindox usage in meat producing animals.

Detection of cometary amines in samples returned by Stardust

NASA Astrophysics Data System (ADS)

Glavin, D. P.; Dworkin, J. P.; Sandford, S. A.

2008-02-01

The abundances of amino acids and amines, as well as their enantiomeric compositions, were measured in samples of Stardust comet-exposed aerogel and foil using liquid chromatography with UV fluorescence detection and time of flight mass spectrometry (LC-FD/ToF-MS). A suite of amino acids and amines including glycine, L-alanine, β-alanine (BALA), γ-amino-n-butyric acid (GABA), ɛ-amino-n-caproic acid (EACA), ethanolamine (MEA), methylamine (MA), and ethylamine (EA) were identified in acid-hydrolyzed, hot-water extracts of these Stardust materials above background levels. With the exception of MA and EA, all other primary amines detected in cometexposed aerogel fragments C2054,4 and C2086,1 were also present in the flight aerogel witness tile that was not exposed to the comet, indicating that most amines are terrestrial in origin. The enhanced relative abundances of MA and EA in comet-exposed aerogel compared to controls, coupled with MA to EA ratios (C2054,4: 1.0 ± 0.2; C2086,1: 1.8 ± 0.2) that are distinct from preflight aerogels (E243-13C and E243-13F: 7 ± 3), suggest that these volatile amines were captured from comet Wild 2. MA and EA were present predominantly in an acid-hydrolyzable bound form in the aerogel, rather than as free primary amines, which is consistent with laboratory analyses of cometary ice analog materials. It is possible that Wild 2 MA and EA were formed on energetically processed icy grains containing ammonia and approximately equal abundances of methane and ethane. The presence of cometary amines in Stardust material supports the hypothesis that comets were an important source of prebiotic organic carbon and nitrogen on the early Earth.

Combined experimental and theoretical approach to understand the reactivity of a mononuclear Cu(II)-hydroperoxo complex in oxygenation reactions.

PubMed

Kamachi, Takashi; Lee, Yong-Min; Nishimi, Tomonori; Cho, Jaeheung; Yoshizawa, Kazunari; Nam, Wonwoo

2008-12-18

A copper(II) complex bearing a pentadentate ligand, [Cu(II)(N4Py)(CF(3)SO(3))(2)] (1) (N4Py = N,N-bis(2-pyridylmethyl)bis(2-pyridyl)methylamine), was synthesized and characterized with various spectroscopic techniques and X-ray crystallography. A mononuclear Cu(II)-hydroperoxo complex, [Cu(II)(N4Py)(OOH)](+) (2), was then generated in the reaction of 1 and H(2)O(2) in the presence of base, and the reactivity of the intermediate was investigated in the oxidation of various substrates at -40 degrees C. In the reactivity studies, 2 showed a low oxidizing power such that 2 reacted only with triethylphosphine but not with other substrates such as thioanisole, benzyl alcohol, 1,4-cyclohexadiene, cyclohexene, and cyclohexane. In theoretical work, we have conducted density functional theory (DFT) calculations on the epoxidation of ethylene by 2 and a [Cu(III)(N4Py)(O)](+) intermediate (3) at the B3LYP level. The activation barrier is calculated to be 39.7 and 26.3 kcal/mol for distal and proximal oxygen attacks by 2, respectively. This result indicates that the direct ethylene epoxidation by 2 is not a plausible pathway, as we have observed in the experimental work. In contrast, the ethylene epoxidation by 3 is a downhill and low-barrier process. We also found that 2 cannot be a precursor to 3, since the homolytic cleavage of the O-O bond of 2 is very endothermic (i.e., 42 kcal/mol). On the basis of the experimental and theoretical results, we conclude that a mononuclear Cu(II)-hydroperoxo species bearing a pentadentate N5 ligand is a sluggish oxidant in oxygenation reactions.

Proton-Mediated Block of Ca2+ Channels during Multivesicular Release Regulates Short-Term Plasticity at an Auditory Hair Cell Synapse

PubMed Central

Cho, Soyoun

2014-01-01

Synaptic vesicles release both neurotransmitter and protons during exocytosis, which may result in a transient acidification of the synaptic cleft that can block Ca2+ channels located close to the sites of exocytosis. Evidence for this effect has been reported for retinal ribbon-type synapses, but not for hair cell ribbon synapses. Here, we report evidence for proton release from bullfrog auditory hair cells when they are held at more physiological, in vivo–like holding potentials (Vh = −60 mV) that facilitate multivesicular release. During paired recordings of hair cells and afferent fibers, L-type voltage-gated Ca2+ currents showed a transient block, which was highly correlated with the EPSC amplitude (or the amount of glutamate release). This effect was masked at Vh = −90 mV due to the presence of a T-type Ca2+ current and blocked by strong pH buffering with HEPES or TABS. Increasing vesicular pH with internal methylamine in hair cells also abolished the transient block. High concentrations of intracellular Ca2+ buffer (10 mm BAPTA) greatly reduced exocytosis and abolished the transient block of the Ca2+ current. We estimate that this transient block is due to the rapid multivesicular release of ∼600–1300 H+ ions per synaptic ribbon. Finally, during a train of depolarizing pulses, paired pulse plasticity was significantly changed by using 40 mm HEPES in addition to bicarbonate buffer. We propose that this transient block of Ca2+ current leads to more efficient exocytosis per Ca2+ ion influx and it may contribute to spike adaptation at the auditory nerve. PMID:25429130

Sensitive, accurate and rapid detection of trace aliphatic amines in environmental samples with ultrasonic-assisted derivatization microextraction using a new fluorescent reagent for high performance liquid chromatography.

PubMed

Chen, Guang; Liu, Jianjun; Liu, Mengge; Li, Guoliang; Sun, Zhiwei; Zhang, Shijuan; Song, Cuihua; Wang, Hua; Suo, Yourui; You, Jinmao

2014-07-25

A new fluorescent reagent, 1-(1H-imidazol-1-yl)-2-(2-phenyl-1H-phenanthro[9,10-d]imidazol-1-yl)ethanone (IPPIE), is synthesized, and a simple pretreatment based on ultrasonic-assisted derivatization microextraction (UDME) with IPPIE is proposed for the selective derivatization of 12 aliphatic amines (C1: methylamine-C12: dodecylamine) in complex matrix samples (irrigation water, river water, waste water, cultivated soil, riverbank soil and riverbed soil). Under the optimal experimental conditions (solvent: ACN-HCl, catalyst: none, molar ratio: 4.3, time: 8 min and temperature: 80°C), micro amount of sample (40 μL; 5mg) can be pretreated in only 10 min, with no preconcentration, evaporation or other additional manual operations required. The interfering substances (aromatic amines, aliphatic alcohols and phenols) get the derivatization yields of <5%, causing insignificant matrix effects (<4%). IPPIE-analyte derivatives are separated by high performance liquid chromatography (HPLC) and quantified by fluorescence detection (FD). The very low instrumental detection limits (IDL: 0.66-4.02 ng/L) and method detection limits (MDL: 0.04-0.33 ng/g; 5.96-45.61 ng/L) are achieved. Analytes are further identified from adjacent peaks by on-line ion trap mass spectrometry (MS), thereby avoiding additional operations for impurities. With this UDME-HPLC-FD-MS method, the accuracy (-0.73-2.12%), precision (intra-day: 0.87-3.39%; inter-day: 0.16-4.12%), recovery (97.01-104.10%) and sensitivity were significantly improved. Successful applications in environmental samples demonstrate the superiority of this method in the sensitive, accurate and rapid determination of trace aliphatic amines in micro amount of complex samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Application of 1H NMR spectroscopy-based metabonomics to feces of cervical cancer patients with radiation-induced acute intestinal symptoms.

PubMed

Chai, Yanlan; Wang, Juan; Wang, Tao; Yang, Yunyi; Su, Jin; Shi, Fan; Wang, Jiquan; Zhou, Xi; He, Bin; Ma, Hailin; Liu, Zi

2015-11-01

Radiation-induced acute intestinal symptoms (RIAISs) are a common complication of radiotherapy for cervical cancer. The aim of this study was to use (1)H nuclear magnetic resonance ((1)H NMR) combined with chemometric analysis to develop a metabolic profile of patients with RIAISs. Fecal samples were collected from 66 patients with cervical cancer before and after pelvic radiotherapy. After radiotherapy, RIAISs occurred in eleven patients. We selected another 11 patients from participants without RIAISs whose age, stage, histological type and treatment methods are matched with RIAIS patients as the control group. (1)H NMR spectroscopy combined with multivariate pattern recognition analysis was used to generate metabolic profile data, as well as to establish a RIAIS-specific metabolic phenotype. Orthogonal partial least-squares discriminant analysis was used to distinguish samples between the pre- and post-radiotherapy RIAIS patients and between RIAIS patients and controls. Fecal samples from RIAIS patients after pelvic radiotherapy were characterized by increased concentrations of α-ketobutyrate, valine, uracil, tyrosine, trimethylamine N-oxide, phenylalanine, lysine, isoleucine, glutamine, creatinine, creatine, bile acids, aminohippurate, and alanine, accompanied by reduced concentrations of α-glucose, n-butyrate, methylamine, and ethanol relative to samples from RIAIS patients before pelvic radiotherapy, while in RIAIS patients relative to controls, trimethylamine, n-butyrate, fumarate and acetate were down-regulated and valine, TMAO, taurine, phenylalanine, lactate, isoleucine and creatinine were up-regulated. We obtained the metabolic profile of RIAIS patients from fecal samples using NMR-based metabonomics. This profile has the potential to be developed into a novel clinical tool for RIAIS diagnosis or therapeutic monitoring, and could contribute to an improved understanding of the disease mechanism. However, because of the limitations of methods, technique, bacterial contamination of feces and small sample size, further research and verification are needed. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Exhaled volatile substances mirror clinical conditions in pediatric chronic kidney disease

PubMed Central

Obermeier, Juliane; Trefz, Phillip; Happ, Josephine; Schubert, Jochen K.; Staude, Hagen

2017-01-01

Monitoring metabolic adaptation to chronic kidney disease (CKD) early in the time course of the disease is challenging. As a non-invasive technique, analysis of exhaled breath profiles is especially attractive in children. Up to now, no reports on breath profiles in this patient cohort are available. 116 pediatric subjects suffering from mild-to-moderate CKD (n = 48) or having a functional renal transplant KTx (n = 8) and healthy controls (n = 60) matched for age and sex were investigated. Non-invasive quantitative analysis of exhaled breath profiles by means of a highly sensitive online mass spectrometric technique (PTR-ToF) was used. CKD stage, the underlying renal disease (HUS; glomerular diseases; abnormalities of kidney and urinary tract or polycystic kidney disease) and the presence of a functional renal transplant were considered as classifiers. Exhaled volatile organic compound (VOC) patterns differed between CKD/ KTx patients and healthy children. Amounts of ammonia, ethanol, isoprene, pentanal and heptanal were higher in patients compared to healthy controls (556, 146, 70.5, 9.3, and 5.4 ppbV vs. 284, 82.4, 49.6, 5.30, and 2.78 ppbV). Methylamine concentrations were lower in the patient group (6.5 vs 10.1 ppbV). These concentration differences were most pronounced in HUS and kidney transplanted patients. When patients were grouped with respect to degree of renal failure these differences could still be detected. Ammonia accumulated already in CKD stage 1, whereas alterations of isoprene (linked to cholesterol metabolism), pentanal and heptanal (linked to oxidative stress) concentrations were detectable in the breath of patients with CKD stage 2 to 4. Only weak associations between serum creatinine and exhaled VOCs were noted. Non-invasive breath testing may help to understand basic mechanisms and metabolic adaptation accompanying progression of CKD. Our results support the current notion that metabolic adaptation occurs early during the time course of CKD. PMID:28570715

The carboxyl group of Glu113 is required for stabilization of the diferrous and bis-FeIV states of MauG

PubMed Central

Tarboush, Nafez Abu; Yukl, Erik T.; Shin, Sooim; Feng, Manliang; Wilmot, Carrie M.; Davidson, Victor L.

2013-01-01

The diheme enzyme MauG catalyzes a six-electron oxidation required for posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. Crystallographic studies have implicated Glu113 in the formation of the bis-FeIV state of MauG, in which one heme is FeIV=O and the other is FeIV with His-Tyr axial ligation. An E113Q mutation had no effect on the structure of MauG, but significantly altered its redox properties. E113Q MauG could not be converted to the diferrous state by reduction with dithionite, but was only reduced to a mixed valence FeII/FeIII state, which is never observed in wild-type (WT) MauG. Addition of H2O2 to E113Q MauG generated a high valence state that formed more slowly and was less stable than the bis-FeIV state of WT MauG. E113Q MauG exhibited no detectable TTQ biosynthesis activity in a steady-state assay with preMADH as the substrate. It did catalyze the steady-state oxidation of quinol MADH to the quinone, but 1000-fold less efficiently than WT MauG. Addition of H2O2 to a crystal of the E113Q MauG-preMADH complex resulted in partial synthesis of TTQ. Extended exposure of these crystals to H2O2 resulted in hydroxylation of Pro107 in the distal pocket of the high-spin heme. It is concluded that the loss of the carboxylic group of Glu113 disrupts the redox cooperativity between hemes that allows rapid formation of the diferrous state, and alters the distribution of high-valence species that participate in charge-resonance stabilization of the bis-FeIV redox state. PMID:23952537

Isolation and characterization of an N-methylcarbamate insecticide-degrading methylotrophic bacterium.

PubMed Central

Topp, E; Hanson, R S; Ringelberg, D B; White, D C; Wheatcroft, R

1993-01-01

A gram-negative bacterium which hydrolyzed aryl N-methylcarbamate insecticides was isolated from an agricultural soil which quickly degraded these pesticides. This organism, designated strain ER2, grew on carbofuran as a sole source of carbon and nitrogen with a doubling time of 3 h in a mineral salts medium. The aromatic nucleus of the molecule was not metabolized, and carbofuran 7-phenol accumulated as the end product of metabolism. The insecticides carbaryl, bendiocarb, and propoxur were similarly hydrolyzed, with each yielding the corresponding phenol. Strain ER2 contained two plasmids (120 and 130 kb). A probe cloned from the pDL11 plasmid of Achromobacter sp. strain WM111, which encodes the carbofuran hydrolase (mcd) gene (P. H. Tomasek and J. S. Karns, J. Bacteriol. 171:4038-4044, 1989), hybridized to the 120-kb plasmid. Restriction fragment profiles of pDL11 and strain ER2 plasmid DNAs suggested that the 120-kb plasmid of strain ER2 is very similar to pDL11. On the basis of the results of biochemical tests, 16S rRNA sequence analysis, and membrane lipid analyses, strain ER2 was found to be a phylogenetically unique type II methylotroph. The constitutive carbofuran hydrolase activity in glucose-grown cells increased sevenfold when strain ER2 was grown in the presence of 100 mg of carbofuran per liter as the sole source of carbon and nitrogen or as the sole nitrogen source in the presence of glucose. Growth on carbofuran resulted in the induction of enzymes required for methylamine-dependent respiration and the serine pathway of formaldehyde assimilation. These results indicate that the carbofuran hydrolase mcd gene is conserved on a plasmid found in organisms from different geographic areas and that the specific activity of carbofuran degradation may increase in response to carbofuran treatment. Images PMID:7504430

The multicatalytic proteinase complex (proteasome): structure and conformational changes associated with changes in proteolytic activity.

PubMed Central

Djaballah, H; Rowe, A J; Harding, S E; Rivett, A J

1993-01-01

The multicatalytic proteinase complex or proteasome is a high-molecular-mass multisubunit proteinase which is found in the nucleus and cytoplasm of eukaryotic cells. Electron microscopy of negatively stained rat liver proteinase preparations suggests that the particle has a hollow cylindrical shape (approximate width 11 nm and height 17 nm using methylamine tungstate as the negative stain) with a pseudo-helical arrangement of subunits rather than the directly stacked arrangement suggested previously. The side-on view has a 2-fold rotational symmetry, while end-on there appears to be six or seven subunits around the ring. This model is very different from that proposed by others for the proteinase from rat liver but resembles the structure of the simpler archaebacterial proteasome. The possibility of conformational changes associated with the addition of effectors of proteolytic activity has been investigated by sedimentation velocity analysis and dynamic light-scattering measurements. The results provide the first direct evidence for conformational changes associated with the observed positive co-operativity in one component of the peptidylglutamylpeptide hydrolase activity as well as with the stimulation of peptidylglutamylpeptide hydrolase activities by MnCl2. In the latter case, there appears to be a correlation between changes in the shape of the molecule and the effect on activity. KCl and low concentrations of SDS may also act by inducing conformational changes within the complex. Sedimentation-velocity measurements also provide evidence for the formation of intermediates during dissociation of the complex by urea, guanidinium chloride or sodium thiocyanate. Dissociation of the complex either by these agents or by treatment at low pH leads to inactivation of its proteolytic components. The results suggest that activation and inhibition of the various proteolytic activities may be mediated by measurable changes in size and shape of the molecules. Images Figure 1 Figure 2 PMID:8318014

Isomer-specific profiling of N-glycans derived from human serum for potential biomarker discovery in pancreatic cancer.

PubMed

Liu, Yufei; Wang, Chang; Wang, Ran; Wu, Yike; Zhang, Liang; Liu, Bi-Feng; Cheng, Liming; Liu, Xin

2018-06-15

Glycosylation is one of the most important post-translational modifications of protein. Recently, global profiling of human serum glycomics has become a noninvasive method for cancer-related biomarker discovery and many studies have focused on compositional glycan profiling. In contrast, structure-specific glycan profiling may provide more potential biomarkers with higher specificity than compositional profiling. In this work, N-glycans released from human serum were neutralized with methylamine and reduced by ammonia-borane complex prior to profiling using nanoLC-ESI-MS with porous graphitized carbon (PGC) and relative abundances of over 280 isomers were compared between pancreatic cancer (PC) cases (n = 32) and healthy controls (n = 32). Statistical analysis identified 25 specific-isomeric biomarkers with significant differences (p-value < 0.05). ROC and PCA analysis were performed to assess the potential biomarkers which were identified as being significantly altered in cancer. The AUCs of the significantly changed specific-isomers were ranging from 0.712 to 0.949. In addition, with the combination of all potential biomarkers, a higher AUC of 0.976 with sensitivity (93.5%) and specificity (90.6%) was obtained. Overall, the proposed strategy coupled to relative quantitative analysis of isomeric glycans make it possible to discover new biomarkers for the diagnosis of PC. Pancreatic cancer (PC) has a poor prognosis with a five-year survival rate <5%. Therefore, a strategy for accurate diagnosis of PC is indeed required. In this paper, a dual-derivatized strategy for structure-specific glycan profiling has been used and according to our best knowledge, this is the first application of this strategy for PC biomarker discovery, in which the separation, identification and relative quantification of isomeric glycans can be simultaneously obtained. In addition, by in-depth analysis of isomeric glycans, the full description of the stereo- and region- diversity of glycans can also be achieved, which might provide more potential information for PC biomarker discovery. Copyright © 2018 Elsevier B.V. All rights reserved.

Coenzyme Q10 quantification in muscle, fibroblasts and cerebrospinal fluid by liquid chromatography/tandem mass spectrometry using a novel deuterated internal standard.

PubMed

Duberley, Kate E C; Hargreaves, Iain P; Chaiwatanasirikul, Korn-Anong; Heales, Simon J R; Land, John M; Rahman, Shamima; Mills, Kevin; Eaton, Simon

2013-05-15

Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10 ; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9 , an endogenous ubiquinone in humans, as an internal standard. Deuterated CoQ10 (d6 -CoQ10 ) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6 -CoQ10 as internal standard and 5 mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150 × 3 mm, 3 µm). CoQ10 levels were linear over a concentration range of 0-200 nM (R(2) = 0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.7-8.7 nM; n = 17), fibroblasts (57.0-121.6 pmol/mg; n = 50) and muscle (187.3-430.1 pmol/mg; n = 15). Use of d6 -CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation. Copyright © 2013 John Wiley & Sons, Ltd.

A Reflectron Time-of-Flight Mass Spectrometric Study on the Degradation Pathways of Glycine on Mars in the Presence of Perchlorates and Ionizing Radiation

NASA Astrophysics Data System (ADS)

Góbi, Sándor; Förstel, Marko; Maksyutenko, Pavlo; Kaiser, Ralf I.

2017-02-01

The absence of abundant organics on the Martian surface is a much discussed observation. So far, no explanation is completely satisfactory. In this study we aim for a deeper understanding of the degradation processes of organics in the presence of perchlorates that can take place on the Martian surface. Our primary goal is to study the radiation-induced decomposition process of glycine (H2NCH2COOH) in the absence and presence of an oxidizer relevant to the Martian surface—perchlorate anions ({{{ClO}}4}-). Glycine and various samples of glycine-1-13C (+H3NC{{{{H}}}2}13COO-)-magnesium perchlorate hexahydrate (Mg(ClO4)2 · 6H2O) were exposed to energetic electrons mimicking secondary electrons originating from the interaction of galactic cosmic rays (GCRs) with the Martian regolith. Using isotope-labeled and deuterated pure glycine samples such as glycine-1-13C, glycine-d5 (+D3NCD2COO-), glycine-N,N,N-d3 (+D3NCH2COO-), and glycine-2,2-d2 (+H3NCD2COO-), we can conclude that decarboxylation (carbon dioxide loss) of the glycine molecule is exclusively the first decay step during irradiation regardless of whether perchlorate anions are present or not. In pure glycine samples, the decarboxylation co-product methylamine (CH3NH2) and its radiolytic decay product ammonia could both be detected explicitly for the first time. In the presence of perchlorates, (partial) oxidation of the glycine decarboxylation product CH3NH2 may occur. Because the decarboxylation is an equilibrium reaction and the CH3NH2 is effectively removed from the system by this oxidation, glycine cannot be recycled. Therefore the depletion of the CH3NH2 facilitates the process, resulting in an overall 10-fold increase in the formation rate of carbon dioxide and its elevated concentrations in the perchlorate-containing irradiated samples.

Biological amine transport in chromaffin ghosts. Coupling to the transmembrane proton and potential gradients.

PubMed

Johnson, R G; Pfister, D; Carty, S E; Scarpa, A

1979-11-10

The effect of the transmembrane proton gradient (delta pH) and potential gradient (delta psi) upon the rate and extent of amine accumulation was investigated in chromaffin ghosts. The chromaffin ghosts were formed by hypo-osmotic lysis of isolated bovine chromaffin granules and extensive dialysis in order to remove intragranular binding components and dissipate the endogenous electrochemical gradients. Upon ATP addition to suspensions of chromaffin ghosts, a transmembrane proton gradient alone, a transmembrane gradient alone, or both, could be established, depending upon the compositions of the media in which the ghosts were formed and resuspended. When chloride was present in the medium, addition of ATP resulted in the generation of a transmembrane proton gradient, acidic inside of 1 pH unit (measured by [14C]methylamine distribution), and no transmembrane potential (measured by [14C]-thiocyanate distribution). When ATP was added to chromaffin ghosts suspended in a medium in which chloride was substituted by isethionate, a transmembrane potential, inside positive, of 45 mV and no transmembrane proton gradient, was measured. In each medium, the addition of agents known to affect proton or potential gradients, respectively, exerted a predictable mechanism of action. Accumulation of [14C]epinephrine or [14C]5-hydroxytryptamine was over 1 order of magnitude greater in the presence of the transmembrane proton gradient or the transmembrane potential than in the absence of any gradient and, moreover, was related to the magnitude of the proton or potential gradient in a dose-dependent manner. When ghosts were added to a medium containing chloride and isethionate, both a delta pH and delta psi could be generated upon addition of ATP. In this preparation, the maximal rate of amine accumulation was observed. The results indicate that amine accumulation into chromaffin ghosts can occur in the presence of either a transmembrane proton gradient, or a transmembrane potential gradient, and that the maximal rate of accumulation may exist when both components of the protonmotive force are present.

Role of the 5-HT₂A receptor in the locomotor hyperactivity produced by phenylalkylamine hallucinogens in mice.

PubMed

Halberstadt, Adam L; Powell, Susan B; Geyer, Mark A

2013-07-01

The 5-HT₂A receptor mediates the effects of serotonergic hallucinogens and may play a role in the pathophysiology of certain psychiatric disorders, including schizophrenia. Given these findings, there is a need for animal models to assess the behavioral effects of 5-HT₂A receptor activation. Our previous studies demonstrated that the phenylalkylamine hallucinogen and 5-HT₂A/₂C agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) produces dose-dependent effects on locomotor activity in C57BL/6J mice, increasing activity at low to moderate doses and reducing activity at high doses. DOI did not increase locomotor activity in 5-HT₂A knockout mice, indicating the effect is a consequence of 5-HT₂A receptor activation. Here, we tested a series of phenylalkylamine hallucinogens in C57BL/6J mice using the Behavioral Pattern Monitor (BPM) to determine whether these compounds increase locomotor activity by activating the 5-HT₂A receptor. Low doses of mescaline, 2,5-dimethoxy-4-ethylamphetamine (DOET), 2,5-dimethoxy-4-propylamphetamine (DOPR), 2,4,5-trimethoxyamphetamine (TMA-2), and the conformationally restricted phenethylamine (4-bromo-3,6-dimethoxybenzocyclobuten-1-yl)methylamine (TCB-2) increased locomotor activity. By contrast, the non-hallucinogenic phenylalkylamine 2,5-dimethoxy-4-tert-butylamphetamine (DOTB) did not alter locomotor activity at any dose tested (0.1-10 mg/kg i.p.). The selective 5-HT₂A antagonist M100907 blocked the locomotor hyperactivity induced by mescaline and TCB-2. Similarly, mescaline and TCB-2 did not increase locomotor activity in 5-HT₂A knockout mice. These results confirm that phenylalkylamine hallucinogens increase locomotor activity in mice and demonstrate that this effect is mediated by 5-HT₂A receptor activation. Thus, locomotor hyperactivity in mice can be used to assess phenylalkylamines for 5-HT₂A agonist activity and hallucinogen-like behavioral effects. These studies provide additional support for the link between 5-HT₂A activation and hallucinogenesis. Copyright © 2013 Elsevier Ltd. All rights reserved.

Betaines and dimethylsulfoniopropionate as major osmolytes in cnidaria with endosymbiotic dinoflagellates.

PubMed

Yancey, Paul H; Heppenstall, Marina; Ly, Steven; Andrell, Raymond M; Gates, Ruth D; Carter, Virginia L; Hagedorn, Mary

2010-01-01

Most marine invertebrates and algae are osmoconformers whose cells accumulate organic osmolytes that provide half or more of cellular osmotic pressure. These solutes are primarily free amino acids and glycine betaine in most invertebrates and small carbohydrates and dimethylsulfoniopropionate (DMSP) in many algae. Corals with endosymbiotic dinoflagellates (Symbiodinium spp.) have been reported to obtain from the symbionts potential organic osmolytes such as glycerol, amino acids, and DMSP. However, corals and their endosymbionts have not been fully analyzed for osmolytes. We quantified small carbohydrates, free amino acids, methylamines, and DMSP in tissues of the corals Fungia scutaria, Pocillopora damicornis, Pocillopora meandrina, Montipora capitata, Porites compressa, and Porites lobata (all with symbionts) plus Tubastrea aurea (asymbiotic) from Kaneohe Bay, Oahu (Hawaii). Glycine betaine, at 33-69 mmol/kg wet mass, was found to constitute 90% or more of the measured organic solutes in all except the Porites species. Those were dominated by proline betaine and dimethyltaurine. DMSP was found at 0.5-3 mmol/kg in all species with endosymbionts. Freshly isolated Symbiodinium from Fungia, P. damicornis, and P. compressa were also analyzed. DMSP and glycine betaine dominated in the first two; Porites endosymbionts had DMSP, proline betaine, and dimethyltaurine. In all specimens, glycerol and glucose were detected by high-performance liquid chromatography only at 0-1 mmol/kg wet mass. An enzymatic assay for glycerol plus glycerol 3-phosphate and dihydroxyacetone phosphate yielded 1-10 mmol/kg. Cassiopeia andromeda (upside-down jelly; Scyphozoan) and Aiptasia puchella (solitary anemone; Anthozoan) were also analyzed; both have endosymbiotic dinoflagellates. In both, glycine betaine, taurine, and DMSP were the dominant osmolytes. In summary, methylated osmolytes dominate in many Cnidaria; in those with algal symbionts, host and symbiont have similar methylated amino acids, as do congeners. However, little glycerol was present as an osmolyte and was probably metabolized before it could accumulate.

Distribution of Aliphatic Amines in CO, CV, and CK Carbonaceous Chondrites and Relation to Mineralogy and Processing History

NASA Technical Reports Server (NTRS)

Aponte, Jose C.; Abreu, Neyda M.; Glavin, Daniel P.; Dworkin, Jason P.; Elsila, Jamie E.

2017-01-01

The analysis of water-soluble organic compounds in meteorites provides valuable insights into the prebiotic synthesis of organic matter and the processes that occurred during the formation of the solar system. We investigated the concentration of aliphatic monoamines present in hot acid water extracts of the unaltered Antarctic carbonaceous chondrites, Dominion Range (DOM) 08006 (CO3) and Miller Range (MIL) 05013 (CO3), and the thermally altered meteorites, Allende (CV3), LAP 02206 (CV3), GRA 06101 (CV3), Allan Hills (ALH) 85002 (CK4), and EET 92002 (CK5). We have also reviewed and assessed the petrologic characteristics of the meteorites studied here to evaluate the effects of asteroidal processing on the abundance and molecular distributions of monoamines. The CO3, CV3, CK4, and CK5 meteorites studied here contain total concentrations of amines ranging from 1.2 to 4.0 nmol/g of meteorite; these amounts are 1-3 orders of magnitude below those observed in carbonaceous chondrites from the CI, CM, and CR groups. The low-amine abundances for CV and CK chondrites may be related to their extensive degree of thermal metamorphism and/or to their low original amine content. Although the CO3 meteorites, DOM 08006 and MIL 05013, do not show signs of thermal and aqueous alteration, their monoamine contents are comparable to those observed in moderately/extensively thermally altered CV3, CK4, and CK5 carbonaceous chondrites. The low content of monoamines in pristine CO carbonaceous chondrites suggests that the initial amounts, and not asteroidal processes, play a dominant role in the content of monoamines in carbonaceous chondrites. The primary monoamines, methylamine, ethylamine, and n-propylamine constitute the most abundant amines in the CO3, CV3, CK4, and CK5 meteorites studied here. Contrary to the predominance of n-x-amino acid isomers in CO3 and thermally altered meteorites, there appears to be no preference for the larger n-amines.

Optimisation approaches for concurrent transmitted light imaging during confocal microscopy.

PubMed

Collings, David A

2015-01-01

The transmitted light detectors present on most modern confocal microscopes are an under-utilised tool for the live imaging of plant cells. As the light forming the image in this detector is not passed through a pinhole, out-of-focus light is not removed. It is this extended focus that allows the transmitted light image to provide cellular and organismal context for fluorescence optical sections generated confocally. More importantly, the transmitted light detector provides images that have spatial and temporal registration with the fluorescence images, unlike images taken with a separately-mounted camera. Because plants often provide difficulties for taking transmitted light images, with the presence of pigments and air pockets in leaves, this study documents several approaches to improving transmitted light images beginning with ensuring that the light paths through the microscope are correctly aligned (Köhler illumination). Pigmented samples can be imaged in real colour using sequential scanning with red, green and blue lasers. The resulting transmitted light images can be optimised and merged in ImageJ to generate colour images that maintain registration with concurrent fluorescence images. For faster imaging of pigmented samples, transmitted light images can be formed with non-absorbed wavelengths. Transmitted light images of Arabidopsis leaves expressing GFP can be improved by concurrent illumination with green and blue light. If the blue light used for YFP excitation is blocked from the transmitted light detector with a cheap, coloured glass filters, the non-absorbed green light will form an improved transmitted light image. Changes in sample colour can be quantified by transmitted light imaging. This has been documented in red onion epidermal cells where changes in vacuolar pH triggered by the weak base methylamine result in measurable colour changes in the vacuolar anthocyanin. Many plant cells contain visible levels of pigment. The transmitted light detector provides a useful tool for documenting and measuring changes in these pigments while maintaining registration with confocal imaging.

[Vitamin B12-independent strains of Methylophaga marina isolated from Red Sea algae].

PubMed

Li, Ts D; Doronina, N V; Ivanova, E G; Trotsenko, Iu A

2007-01-01

Two strains (KM3 and KM5) of halophilic methylobacteria isolated from Red Sea algae do not require vitamin B12 for growth and can use methanol, methylamine, dimethylamine, trimethylamine, dimethyl sulfide, and fructose as sources of carbon and energy. The cells of these strains are gram-negative motile monotrichous (strain KM3) or peritrichous (strain KM5) rods. The strains are strictly aerobic and require Na+ ions but not growth factors for growth. They are oxidase- and catalase-positive and reduce nitrates to nitrites. Both strains can grow in a temperature range of 4 to 37 degrees C (with optimal growth at 29-34 degrees C), at pH between 5.5 and 8.5 (with optimal growth at pH 7.5-8.0), and in a range of salt concentrations between 0.5 and 15% NaCl (with optimal growth at 5-9% NaCl). The phospholipids of these strains are dominated by phosphatidylethanolamine and phosphatidylglycerol and also include phosphatidylcholine, phosphatidylserine, and cardiolipin. The dominant fatty acids are C(16:1omega7c) and C(16:0). The major ubiquinone is Q8. The cells accumulate ectoin, glutamate, and sucrose as intracellular osmoprotectants. The strains implement the 2-keto-3-deoxy-6-phosphogluconate-dependent variant of the ribulose monophosphate pathway. The G+C content of the DNA is 44.4-44.7 mol %. Analysis of the 16S rRNA genes showed that both strains belong to Gammaproteobacteria and have a high degree of homology (99.4%) to Methylophaga marina ATCC 35842T . Based on the data of polyphasic taxonomy, strains KM3 and KM5 are identified as new strains M. marina KM3 (VKM B-2386) and M. marina KM5 (VKM B-2387). The ability of these strains to produce auxins (indole-3-acetic acid) suggests their metabolic association with marine algae.

Changes in methanogenic substrate utilization and communities with depth in a salt-marsh, creek sediment in southern England

NASA Astrophysics Data System (ADS)

John Parkes, R.; Brock, Fiona; Banning, Natasha; Hornibrook, Edward R. C.; Roussel, Erwan G.; Weightman, Andrew J.; Fry, John C.

2012-01-01

A combined biogeochemical and molecular genetic study of creek sediments (down to 65 cm depth) from Arne Peninsula salt-marsh (Dorset, UK) determined the substrates used for methanogenesis and the distribution of the common methanogens, Methanosarcinales and Methanomicrobiales capable of metabolising these substrates. Methane concentrations increased by 11 cm, despite pore water sulphate not being removed until 45 cm. Neither upward methane diffusion or anaerobic oxidation of methane seemed to be important in this zone. In the near-surface sulphate-reduction zone (5-25 cm) turnover time to methane for the non-competitive methanogenic substrate trimethylamine was most rapid (80 days), and were much longer for acetate (7900 days), methanol (40,500 days) and bicarbonate (361,600 days). Methylamine-utilizing Methanosarcinales were the dominant (60-95%) methanogens in this zone. In deeper sediments rates of methanogenesis from competitive substrates increased substantially, with acetate methanogenic rates becoming ˜100 times greater than H 2/CO 2 methanogenesis below 50 cm. In addition, there was a dramatic change in methanogen diversity with obligate acetate-utilizing, Methanosaeta related sequences being dominant. At a similar depth methanol turnover to methane increased to its most rapid (1700 days). This activity pattern is consistent with deeper methanogen populations (55 cm) being dominated by acetate-utilizing Methanosaeta with H 2/CO 2 and alcohol-utilizing Methanomicrobiales also present. Hence, there is close relationship between the depth distribution of methanogenic substrate utilization and specific methanogens that can utilize these compounds. It is unusual for acetate to be the dominant methanogenic substrate in coastal sediments and δ13C-CH 4 values (-74 to -71‰) were atypical for acetate methanogenesis, suggesting that common stable isotope proxy models may not apply well in this type of dynamic anoxic sediment, with multiple methanogenic substrates.

Protocol for the Solid-phase Synthesis of Oligomers of RNA Containing a 2'-O-thiophenylmethyl Modification and Characterization via Circular Dichroism.

PubMed

Francis, Andrew J; Resendiz, Marino J E

2017-07-28

Solid-phase synthesis has been used to obtain canonical and modified polymers of nucleic acids, specifically of DNA or RNA, which has made it a popular methodology for applications in various fields and for different research purposes. The procedure described herein focuses on the synthesis, purification, and characterization of dodecamers of RNA 5'-[CUA CGG AAU CAU]-3' containing zero, one, or two modifications located at the C2'-O-position. The probes are based on 2-thiophenylmethyl groups, incorporated into RNA nucleotides via standard organic synthesis and introduced into the corresponding oligonucleotides via their respective phosphoramidites. This report makes use of phosphoramidite chemistry via the four canonical nucleobases (Uridine (U), Cytosine (C), Guanosine (G), Adenosine (A)), as well as 2-thiophenylmethyl functionalized nucleotides modified at the 2'-O-position; however, the methodology is amenable for a large variety of modifications that have been developed over the years. The oligonucleotides were synthesized on a controlled-pore glass (CPG) support followed by cleavage from the resin and deprotection under standard conditions, i.e., a mixture of ammonia and methylamine (AMA) followed by hydrogen fluoride/triethylamine/N-methylpyrrolidinone. The corresponding oligonucleotides were purified via polyacrylamide electrophoresis (20% denaturing) followed by elution, desalting, and isolation via reversed-phase chromatography (Sep-pak, C18-column). Quantification and structural parameters were assessed via ultraviolet-visible (UV-vis) and circular dichroism (CD) photometric analysis, respectively. This report aims to serve as a resource and guide for beginner and expert researchers interested in embarking in this field. It is expected to serve as a work-in-progress as new technologies and methodologies are developed. The description of the methodologies and techniques within this document correspond to a DNA/RNA synthesizer (refurbished and purchased in 2013) that uses phosphoramidite chemistry.

Formation of aqueous-phase secondary organic aerosols from glycolaldehyde and ammonium sulfate/amines: A kinetic and mechanistic study

NASA Astrophysics Data System (ADS)

Yi, Yayi; Cao, Zhaoyu; Zhou, Xuehua; Xue, Likun; Wang, Wenxing

2018-05-01

Atmospheric particles are largely represented by secondary organic aerosols (SOAs) produced by either aqueous- or gas-phase reactions. Recently, the contribution of the former to SOA formation has been shown to substantially increase and even reach that of the latter, which necessitates in-depth mechanistic investigations. For a deeper understanding of aqueous-phase SOA generation, we herein studied the production of these aerosols in the dark from glycolaldehyde (GAld) and ammonium sulfate (AS)/amines (methylamine (MAm) and glycine (Gly)). UV-vis spectroscopy showed that reaction mixtures featured two main absorption bands (at 209-230 and 280-330 nm) that were attributed to the π-π* transitions of Schiff bases and the n-π* transitions of oligomers produced in the above reactions, respectively. Further studies revealed that irrespective of reactant concentration and pH, all the investigated reactions were well fitted by first-order kinetics and were accelerated by increasing AS/MAm concentrations and solution pH under acidic conditions. The reaction rate constants (determined from changes of absorption at 300 nm) followed the order of Gly (kI = 2.39 × 10-6 s-1) > MAm (kI = 1.19 × 10-6 s-1) > AS (kI = 8.33 × 10-7 s-1) at identical low AS/amine concentrations and were in the order of MAm (kI = 2.5 × 10-6 s-1) > AS (kI = 1.39 × 10-6 s-1) at high AS/MAm concentrations. The main reaction pathways corresponded to the aldol self-condensation of GAld and the nucleophilic attack of AS/amines on GAld followed by dehydration, which afforded imines as the major products. The stronger light absorption of (GAld + Gly) mixtures than that of (glyoxal/methylglyoxal + Gly) mixtures was ascribed to the increased amount of imine- and carbonyl group-containing products produced in the former case.

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

NASA Astrophysics Data System (ADS)

Sil, Milan; Gorai, Prasanta; Das, Ankan; Bhat, Bratati; Etim, Emmanuel E.; Chakrabarti, Sandip K.

2018-02-01

We consider six isomeric groups ({{CH}}3{{N}}, {{CH}}5{{N}}, {{{C}}}2{{{H}}}5{{N}}, {{{C}}}2{{{H}}}7{{N}}, {{{C}}}3{{{H}}}7{{N}}, and {{{C}}}3{{{H}}}9{{N}}) to review the presence of amines and aldimines within the interstellar medium (ISM). Each of these groups contains at least one aldimine or amine. Methanimine ({{CH}}2{NH}) from {{CH}}3{{N}} and methylamine ({{CH}}3{{NH}}2) from {{CH}}5{{N}} isomeric group were detected a few decades ago. Recently, the presence of ethanimine ({{CH}}3{CHNH}) from {{{C}}}2{{{H}}}5{{N}} isomeric group has been discovered in the ISM. This prompted us to investigate the possibility of detecting any aldimine or amine from the very next three isomeric groups in this sequence: {{{C}}}2{{{H}}}7{{N}}, {{{C}}}3{{{H}}}7{{N}}, and {{{C}}}3{{{H}}}9{{N}}. We employ high-level quantum chemical calculations to estimate accurate energies of all the species. According to enthalpies of formation, optimized energies, and expected intensity ratio, we found that ethylamine (precursor of glycine) from {{{C}}}2{{{H}}}7{{N}} isomeric group, (1Z)-1-propanimine from {{{C}}}3{{{H}}}7{{N}} isomeric group, and trimethylamine from {{{C}}}3{{{H}}}9{{N}} isomeric group are the most viable candidates for the future astronomical detection. Based on our quantum chemical calculations and from other approximations (from prevailing similar types of reactions), a complete set of reaction pathways to the synthesis of ethylamine and (1Z)-1-propanimine is prepared. Moreover, a large gas-grain chemical model is employed to study the presence of these species in the ISM. Our modeling results suggest that ethylamine and (1Z)-1-propanimine could efficiently be formed in hot-core regions and could be observed with present astronomical facilities. Radiative transfer modeling is also implemented to additionally aid their discovery in interstellar space.

Palladium nanoparticles decorated on reduced graphene oxide rotating disk electrodes toward ultrasensitive hydrazine detection: effects of particle size and hydrodynamic diffusion.

PubMed

Krittayavathananon, Atiweena; Srimuk, Pattarachai; Luanwuthi, Santamon; Sawangphruk, Montree

2014-12-16

Although metal nanoparticle/graphene composites have been widely used as the electrode in electrochemical sensors, two effects, consisting of the particle size of the nanoparticles and the hydrodynamic diffusion of analytes to the electrodes, are not yet fully understood. In this work, palladium nanoparticles/reduced graphene oxide (PdNPs/rGO) composites were synthesized using an in situ polyol method. Palladium(II) ions and graphene oxide were reduced together with a reducing agent, ethylene glycol. By varying the concentration of palladium(II) nitrate, PdNPs with different sizes were decorated on the surface of rGO sheets. The as-fabricated PdNPs/rGO rotating disk electrodes (RDEs) were investigated toward hydrazine detection. Overall, a 3.7 ± 1.4 nm diameter PdNPs/rGO RDE exhibits high performance with a rather low limit of detection of about 7 nM at a rotation speed of 6000 rpm and provides a wide linear range of 0.1-1000 μM with R(2) = 0.995 at 2000 rpm. This electrode is highly selective to hydrazine without interference from uric acid, glucose, ammonia, caffeine, methylamine, ethylenediamine, hydroxylamine, n-butylamine, adenosine, cytosine, guanine, thymine, and l-arginine. The PdNPs/rGO RDEs with larger sizes show lower detection performance. Interestingly, the detection performance of the electrodes is sensitive to the hydrodynamic diffusion of hydrazine. The as-fabricated electrode can detect trace hydrazine in wastewater with high stability, demonstrating its practical use as an electrochemical sensor. These findings may lead to an awareness of the effect of the hydrodynamic diffusion of analyte that has been previously ignored, and the 3.7 ± 1.4 nm PdNPs/rGO RDE may be useful toward trace hydrazine detection, especially in wastewater from related chemical industries.

Assessing the Origins of Aliphatic Amines in the Murchison Meteorite from their Compound-Specific Carbon Isotopic Ratios and Enantiomeric Composition

NASA Technical Reports Server (NTRS)

Aponte, Jose; Dworkin, Jason; Elsila, Jamie E.

2014-01-01

The study of meteoritic organic compounds provides a unique window into the chemical inventory of the early Solar System and prebiotic chemistry that may have been important for the origin of life on Earth. Multiple families of organic compounds have been extracted from the Murchison meteorite, which is one of the most thoroughly studied carbonaceous chondrites. The amino acids extracted from Murchison have been extensively analyzed, including measurements of non-terrestrial stable isotopic ratios and discoveries of L-enantiomeric excesses for alpha-dialkyl amino acids, notably isovaline. However, although the isotopic signatures of bulk amine-containing fractions have been measured, the isotopic ratios and enantiomeric composition of individual aliphatic amines, compounds that are chemically related to amino acids, remain unknown. Here, we report a novel method for the extraction, separation, identification and quantitation of aliphatic monoamines extracted from the Murchison meteorite. Our results show a complete suite of structural isomers, with a larger concentration of methylamine and ethylamine and decreasing amine concentrations with increasing carbon number. The carbon isotopic compositions of fourteen meteoritic aliphatic monoamines were measured, with delta C-13 values ranging from +21% to +129%, showing a decrease in C-13 with increasing carbon number, a relationship that may be consistent with the chain elongation mechanism under kinetic control previously proposed for meteoritic amino acids. We also found the enantiomeric composition of sec-butylamine, a structural analog to isovaline, was racemic within error, while the isovaline extracted from the same Murchison piece showed an L-enantiomeric excess of 9.7; this result suggested that processes leading to enantiomeric excess in the amino acid did not affect the amine. We used these collective data to assess the primordial synthetic origins of these meteoritic aliphatic amines and their potential linkage to meteoritic amino acids.

High-resolution spectroscopy of the C-N stretching band of methylamine

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Sun, Zhen-Dong; Billinghurst, B. E.

2011-09-01

The C-N stretching infrared fundamental of CH3NH2 has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH3 torsion and the NH2 inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the vt = 0 torsional state, along with many of the weaker sub-bands of the s species. The C-N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C-N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C-N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors ρ were fitted for the torsion and the inversion and differ significantly in the upper state. The C-N stretching vibrational energy is determined to be 1044.817 cm-1, while the effective upper state B-value is 0.7318 cm-1. Several anharmonic resonances with vt = 4 ground-state levels have been observed and partially characterized. A variety of J-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants.

Spectroscopic and Computational Investigations of a Mononuclear Manganese(IV)-Oxo Complex Reveal Electronic Structure Contributions to Reactivity

DOE PAGES

Leto, Domenick F.; Massie, Allyssa A.; Rice, Derek B.; ...

2016-11-01

The mononuclear Mn(IV)-oxo complex [Mn IV(O)(N4py)] 2+, where N4py is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine, we propose to attack C–H bonds by an excited-state reactivity pattern [Cho, K.-B.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2012, 3, 2851-2856 (DOI: 10.1021/jz301241z)]. In this model, a 4E excited state is utilized to provide a lower-energy barrier for hydrogen-atom transfer. This proposal is intriguing, as it offers both a rationale for the relatively high hydrogen-atom-transfer reactivity of [Mn IV(O)(N4py)] 2+ and a guideline for creating more reactive complexes through ligand modification. Here we employ a combination of electronic absorption and variable-temperature magnetic circularmore » dichroism (MCD) spectroscopy to experimentally evaluate this excited-state reactivity model. Using these spectroscopic methods, in conjunction with time-dependent density functional theory (TD-DFT) and complete-active space self-consistent-field calculations (CASSCF), we define the ligand-field and charge-transfer excited states of [MnIV(O)(N4py)]2+. Through a graphical analysis of the signs of the experimental C-term MCD signals, we unambiguously assign a low-energy MCD feature of [Mn IV(O)(N4py)] 2+ as the 4E excited state predicted to be involved in hydrogen-atom-transfer reactivity. The CASSCF calculations predict enhanced Mn III-oxyl character on the excited-state 4E surface, consistent with previous DFT calculations. Potential-energy surfaces, developed using the CASSCF methods, are used to determine how the energies and wave functions of the ground and excited states evolved as a function of Mn=O distance. Furthermore, the unique insights into ground- and excited-state electronic structure offered by these spectroscopic and computational studies are harmonized with a thermodynamic model of hydrogen-atom-transfer reactivity, which predicts a correlation between transition-state barriers and driving force« less

Protein control of true, gated, and coupled electron transfer reactions.

PubMed

Davidson, Victor L

2008-06-01

Electron transfer (ET) through and between proteins is a fundamental biological process. The rates of ET depend upon the thermodynamic driving force, the reorganization energy, and the degree of electronic coupling between the reactant and product states. The analysis of protein ET reactions is complicated by the fact that non-ET processes might influence the observed ET rate in kinetically complex biological systems. This Account describes studies of the methylamine dehydrogenase-amicyanin-cytochrome c-551i protein ET complex that have revealed the influence of several features of the protein structure on the magnitudes of the physical parameters for true ET reactions and how they dictate the kinetic mechanisms of non-ET processes that sometimes influence protein ET reactions. Kinetic and thermodynamic studies, coupled with structural information and biochemical data, are necessary to fully describe the ET reactions of proteins. Site-directed mutagenesis can be used to elucidate specific structure-function relationships. When mutations selectively alter the electronic coupling, reorganization energy, or driving force for the ET reaction, it becomes possible to use the parameters of the ET process to determine how specific amino acid residues and other features of the protein structure influence the ET rates. When mutations alter the kinetic mechanism for ET, one can determine the mechanisms by which non-ET processes, such as protein conformational changes or proton transfers, control the rates of ET reactions and how specific amino acid residues and certain features of the protein structure influence these non-ET reactions. A complete description of the mechanism of regulation of biological ET reactions enhances our understanding of metabolism, respiration, and photosynthesis at the molecular level. Such information has important medical relevance. Defective protein ET leads to production of the reactive oxygen species and free radicals that are associated with aging and many disease states. Defective ET within the respiratory chain also causes certain mitochondrial myopathies. An understanding of the mechanisms of regulation of protein ET is also of practical value because it provides a logical basis for the design of applications utilizing redox enzymes, such as enzyme-based electrode sensors and fuel cells.

Multiple evidence for methylotrophic methanogenesis as the dominant methanogenic pathway in hypersaline sediments from the Orca Basin, Gulf of Mexico

NASA Astrophysics Data System (ADS)

Zhuang, Guang-Chao; Elling, Felix J.; Nigro, Lisa M.; Samarkin, Vladimir; Joye, Samantha B.; Teske, Andreas; Hinrichs, Kai-Uwe

2016-08-01

Among the most extreme habitats on Earth, dark, deep, anoxic brines host unique microbial ecosystems that remain largely unexplored. As the terminal step of anaerobic degradation of organic matter, methanogenesis is a potentially significant but poorly constrained process in deep-sea hypersaline environments. We combined biogeochemical and phylogenetic analyses with incubation experiments to unravel the origin of methane in the hypersaline sediments of Orca Basin in the northern Gulf of Mexico. Substantial concentrations of methane, up to 3.4 mM, coexisted with high concentrations of sulfate from 16 to 43 mM in two sediment cores retrieved from the northern and southern parts of Orca Basin. The strong depletion of 13C in methane (-77‰ to -89‰) points towards a biological source. While low concentrations of competitive substrates limited the significance of hydrogenotrophic and acetoclastic methanogenesis, the presence of non-competitive methylated substrates (methanol, trimethylamine, dimethyl sulfide, dimethylsulfoniopropionate) supported the potential for methane generation through methylotrophic methanogenesis. Thermodynamic calculations demonstrated that hydrogenotrophic and acetoclastic methanogenesis were unlikely to occur under in situ conditions, while methylotrophic methanogenesis from a variety of substrates was highly favorable. Likewise, carbon isotope relationships between methylated substrates and methane suggested methylotrophic methanogenesis was the major source of methane. Stable and radio-isotope tracer experiments with 13C-labeled bicarbonate, acetate and methanol and 14C-labeled methylamine indicated that methylotrophic methanogenesis was the predominant methanogenic pathway. Based on 16S rRNA gene sequences, halophilic methylotrophic methanogens related to the genus Methanohalophilus dominated the benthic archaeal community in the northern basin and also occurred in the southern basin. High abundances of methanogen lipid biomarkers such as intact polar and polyunsaturated hydroxyarchaeols were detected in sediments from the northern basin, with lower abundances in the southern basin. Strong 13C-depletion of saturated and monounsaturated hydroxyarchaeol were consistent with methylotrophic methanogenesis as the major methanogenic pathway. Collectively, the availability of methylated substrates, thermodynamic calculations, experimentally determined methanogenic activity as well as lipid and gene biomarkers support the hypothesis that methylotrophic methanogenesis is the predominant pathway of methane formation in the presence of sulfate in Orca Basin sediments.

Adaptation of Methanogenic Inocula to Anaerobic Digestion of Maize Silage

PubMed Central

Wojcieszak, Martyna; Pyzik, Adam; Poszytek, Krzysztof; Krawczyk, Pawel S.; Sobczak, Adam; Lipinski, Leszek; Roubinek, Otton; Palige, Jacek; Sklodowska, Aleksandra; Drewniak, Lukasz

2017-01-01

A well-balanced microbial consortium is crucial for efficient biogas production. In turn, one of a major factor that influence on the structure of anaerobic digestion (AD) consortium is a source of microorganisms which are used as an inoculum. This study evaluated the influence of inoculum sources (with various origin) on adaptation of a biogas community and the efficiency of the biomethanization of maize silage. As initial inocula for AD of maize silage the samples from: (i) an agricultural biogas plant (ABP) which utilizes maize silage as a main substrate, (ii) cattle slurry (CS), which contain elevated levels of lignocelluloses materials, and (iii) raw sewage sludge (RSS) with low content of plant origin materials were used. The adaptation of methanogenic consortia was monitored during a series of passages, and the functionality of the adapted consortia was verified through start-up operation of AD in two-stage reactors. During the first stages of the adaptation phase, methanogenic consortia occurred very slowly, and only after several passages did the microbial community adapts to allow production of biogas with high methane content. The ABP consortium revealed highest biogas production in the adaptation and in the start-up process. The biodiversity dynamics monitored during adaptation and start-up process showed that community profile changed in a similar direction in three studied consortia. Native communities were very distinct to each other, while at the end of the Phase II of the start-up process microbial diversity profile was similar in all consortia. All adopted bacterial communities were dominated by representatives of Porphyromonadaceae, Rikenellaceae, Ruminococcaceae, and Synergistaceae. A shift from low acetate-preferring acetoclastic Methanosaetaceae (ABP and RSS) and/or hydrogenotrophic Archaea, e.g., Methanomicrobiaceae (CS) prevailing in the inoculum samples to larger populations of high acetate-preferring acetoclastic Methanosarcinaceae was observed by the end of the experiment. As a result, three independent, functional communities that syntrophically produced methane from acetate (primarily) and H2/CO2, methanol and methylamines were adapted. This study provides new insights into the specific process by which different inocula sampled from typical methanogenic environments that are commonly used to initiate industrial installations gradually adapted to allow biogas production from maize silage. PMID:29033919

Role of the 5-HT2A receptor in the locomotor hyperactivity produced by phenylalkylamine hallucinogens in mice

PubMed Central

Halberstadt, Adam L.; Powell, Susan B.; Geyer, Mark A.

2014-01-01

The 5-HT2A receptor mediates the effects of serotonergic hallucinogens and may play a role in the pathophysiology of certain psychiatric disorders, including schizophrenia. Given these findings, there is a need for animal models to assess the behavioral effects of 5-HT2A receptor activation. Our previous studies demonstrated that the phenylalkylamine hallucinogen and 5-HT2A/2C agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) produces dose-dependent effects on locomotor activity in C57BL/6J mice, increasing activity at low to moderate doses and reducing activity at high doses. DOI did not increase locomotor activity in 5-HT2A knockout mice, indicating the effect is a consequence of 5-HT2A receptor activation. Here, we tested a series of phenylalkylamine hallucinogens in C57BL/6J mice using the Behavioral Pattern Monitor (BPM) to determine whether these compounds increase locomotor activity by activating the 5-HT2A receptor. Low doses of mescaline, 2,5-dimethoxy-4-ethylamphetamine (DOET), 2,5-dimethoxy-4-propylamphetamine (DOPR), 2,4,5-trimethoxyamphetamine (TMA-2), and the conformationally restricted phenethylamine (4-bromo-3,6-dimethoxybenzocyclobuten-1-yl)methylamine (TCB-2) increased locomotor activity. By contrast, the non-hallucinogenic phenylalkylamine 2,5-dimethoxy-4-tert-butylamphetamine (DOTB) did not alter locomotor activity at any dose tested (0.1-10 mg/kg i.p.). The selective 5-HT2A antagonist M100907 blocked the locomotor hyperactivity induced by mescaline and TCB-2. Similarly, mescaline and TCB-2 did not increase locomotor activity in 5-HT2A knockout mice. These results confirm that phenylalkylamine hallucinogens increase locomotor activity in mice and demonstrate that this effect is mediated by 5-HT2A receptor activation. Thus, locomotor hyperactivity in mice can be used to assess phenylalkylamines for 5-HT2A agonist activity and hallucinogen-like behavioral effects. These studies provide additional support for the link between 5-HT2A activation and hallucinogenesis. PMID:23376711

Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota.

PubMed

Hoyles, Lesley; Jiménez-Pranteda, Maria L; Chilloux, Julien; Brial, Francois; Myridakis, Antonis; Aranias, Thomas; Magnan, Christophe; Gibson, Glenn R; Sanderson, Jeremy D; Nicholson, Jeremy K; Gauguier, Dominique; McCartney, Anne L; Dumas, Marc-Emmanuel

2018-04-20

The dietary methylamines choline, carnitine, and phosphatidylcholine are used by the gut microbiota to produce a range of metabolites, including trimethylamine (TMA). However, little is known about the use of trimethylamine N-oxide (TMAO) by this consortium of microbes. A feeding study using deuterated TMAO in C57BL6/J mice demonstrated microbial conversion of TMAO to TMA, with uptake of TMA into the bloodstream and its conversion to TMAO. Microbial activity necessary to convert TMAO to TMA was suppressed in antibiotic-treated mice, with deuterated TMAO being taken up directly into the bloodstream. In batch-culture fermentation systems inoculated with human faeces, growth of Enterobacteriaceae was stimulated in the presence of TMAO. Human-derived faecal and caecal bacteria (n = 66 isolates) were screened on solid and liquid media for their ability to use TMAO, with metabolites in spent media analysed by 1 H-NMR. As with the in vitro fermentation experiments, TMAO stimulated the growth of Enterobacteriaceae; these bacteria produced most TMA from TMAO. Caecal/small intestinal isolates of Escherichia coli produced more TMA from TMAO than their faecal counterparts. Lactic acid bacteria produced increased amounts of lactate when grown in the presence of TMAO but did not produce large amounts of TMA. Clostridia (sensu stricto), bifidobacteria, and coriobacteria were significantly correlated with TMA production in the mixed fermentation system but did not produce notable quantities of TMA from TMAO in pure culture. Reduction of TMAO by the gut microbiota (predominantly Enterobacteriaceae) to TMA followed by host uptake of TMA into the bloodstream from the intestine and its conversion back to TMAO by host hepatic enzymes is an example of metabolic retroconversion. TMAO influences microbial metabolism depending on isolation source and taxon of gut bacterium. Correlation of metabolomic and abundance data from mixed microbiota fermentation systems did not give a true picture of which members of the gut microbiota were responsible for converting TMAO to TMA; only by supplementing the study with pure culture work and additional metabolomics was it possible to increase our understanding of TMAO bioconversions by the human gut microbiota.

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutter-Fella, Carolin M.; Li, Yanbo; Cefarin, Nicola

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH 3NH 3I) and methylammonium bromide (CH 3NH 3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH 3NH 3PbX 3 with X = I, Br, Cl and their mixture) filmsmore » with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH 3NH 3PbI 3-xBr x by exposing the substrate to vapors of a mixture of CH 3NH 3I and CH 3NH 3Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH 3NH 3PbI 3-xBr x with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ E g ≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH 3NH 3PbI 3-xCl x. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.« less

Mechanism for the Coupled Photochemistry of Ammonia and Acetylene: Implications for Giant Planets, Comets and Interstellar Organic Synthesis

NASA Astrophysics Data System (ADS)

Keane, Thomas C.

2017-09-01

Laboratory studies provide a fundamental understanding of photochemical processes in planetary atmospheres. Photochemical reactions taking place on giant planets like Jupiter and possibly comets and the interstellar medium are the subject of this research. Reaction pathways are proposed for the coupled photochemistry of NH3 (ammonia) and C2H2 (acetylene) within the context Jupiter's atmosphere. We then extend the discussion to the Great Red Spot, Extra-Solar Giant Planets, Comets and Interstellar Organic Synthesis. Reaction rates in the form of quantum yields were measured for the decomposition of reactants and the formation of products and stable intermediates: HCN (hydrogen cyanide), CH3CN (acetonitrile), CH3CH = N-N = CHCH3 (acetaldazine), CH3CH = N-NH2 (acetaldehyde hydrazone), C2H5NH2 (ethylamine), CH3NH2 (methylamine) and C2H4 (ethene) in the photolysis of NH3/C2H2 mixtures. Some of these compounds, formed in our investigation of pathways for HCN synthesis, were not encountered previously in observational, theoretical or laboratory photochemical studies. The quantum yields obtained allowed for the formulation of a reaction mechanism that attempts to explain the observed results under varying experimental conditions. In general, the results of this work are consistent with the initial observations of Ferris and Ishikawa (1988). However, their proposed reaction pathway which centers on the photolysis of CH3CH = N-N = CHCH3 does not explain all of the results obtained in this study. The formation of CH3CH = N-N = CHCH3 by a radical combination reaction of CH3CH = N• was shown in this work to be inconsistent with other experiments where the CH3CH = N• radical is thought to form but where no CH3CH = N-N = CHCH3 was detected. The importance of the role of H atom abstraction reactions was demonstrated and an alternative pathway for CH3CH = N-N = CHCH3 formation involving nucleophilic reaction between N2H4 and CH3CH = NH is advanced.

Solar wind ion impacts into ice surfaces: A molecular-dynamics study using the REAX force field

NASA Astrophysics Data System (ADS)

Anders, Christian; Urbassek, Herbert M.

2017-01-01

Molecular dynamics simulation is used to study the effects of solar-wind ion irradiation on an ice target, focusing on the effects of nuclear energy deposition. A reactive force field (REAX) interatomic interaction potential is employed that allows us to model the breaking and formation of molecular bonds and hence to follow the chemistry occurring in the target. As ions we study H and He ions as typical constituents of the solar wind, and Ne as an example of a heavier ion; they impact at the speed of maximum flux in the solar wind, 400 km/s. The ice consists of a mixture of H2O, CO2, CH3OH and NH3. We find that molecular dissociations occur within 0.2 ps after ion impact and new products are formed up to a time of 1 ps; only water has a slower dynamics, due to highly mobile H atoms allowing for late recombinations. The number of dissociations, and hence also of product molecules increases from H over He to Ne ion projectiles and can be quantified by the amount of energy deposited in the target by these ions. The most abundant products formed include CO, OH and NH2. Reaction products are most complex for Ne impact, and include H3O, formaldehyde (H2CO), HO2, and NO. Formaldehyde is important as it is formed relatively frequently and is known as a precursor in the formation of sugars. In addition, molecules containing all CHON elements are formed, among which are CH2NO, CONH, methanolamine (CH5NO), and ethyne (C2H2). Repeated impacts generate novel, and more complex product species; we found CN, CH4, CH3NO, methylamine (CH3NH2), and acetamide (CH3CONH2), among others; the complex species are formed less frequently than the simple fragments. Sputtering occurs for all projectiles, even H. The ejecta are either original molecules - in particular CO2 - or simple fragments; only few product molecules are emitted.

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films

DOE PAGES

Sutter-Fella, Carolin M.; Li, Yanbo; Cefarin, Nicola; ...

2017-09-08

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH 3NH 3I) and methylammonium bromide (CH 3NH 3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH 3NH 3PbX 3 with X = I, Br, Cl and their mixture) filmsmore » with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH 3NH 3PbI 3-xBr x by exposing the substrate to vapors of a mixture of CH 3NH 3I and CH 3NH 3Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH 3NH 3PbI 3-xBr x with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ E g ≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH 3NH 3PbI 3-xCl x. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.« less

Spectroscopic and Computational Investigations of a Mononuclear Manganese(IV)-Oxo Complex Reveal Electronic Structure Contributions to Reactivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leto, Domenick F.; Massie, Allyssa A.; Rice, Derek B.

The mononuclear Mn(IV)-oxo complex [Mn IV(O)(N4py)] 2+, where N4py is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine, we propose to attack C–H bonds by an excited-state reactivity pattern [Cho, K.-B.; Shaik, S.; Nam, W. J. Phys. Chem. Lett. 2012, 3, 2851-2856 (DOI: 10.1021/jz301241z)]. In this model, a 4E excited state is utilized to provide a lower-energy barrier for hydrogen-atom transfer. This proposal is intriguing, as it offers both a rationale for the relatively high hydrogen-atom-transfer reactivity of [Mn IV(O)(N4py)] 2+ and a guideline for creating more reactive complexes through ligand modification. Here we employ a combination of electronic absorption and variable-temperature magnetic circularmore » dichroism (MCD) spectroscopy to experimentally evaluate this excited-state reactivity model. Using these spectroscopic methods, in conjunction with time-dependent density functional theory (TD-DFT) and complete-active space self-consistent-field calculations (CASSCF), we define the ligand-field and charge-transfer excited states of [MnIV(O)(N4py)]2+. Through a graphical analysis of the signs of the experimental C-term MCD signals, we unambiguously assign a low-energy MCD feature of [Mn IV(O)(N4py)] 2+ as the 4E excited state predicted to be involved in hydrogen-atom-transfer reactivity. The CASSCF calculations predict enhanced Mn III-oxyl character on the excited-state 4E surface, consistent with previous DFT calculations. Potential-energy surfaces, developed using the CASSCF methods, are used to determine how the energies and wave functions of the ground and excited states evolved as a function of Mn=O distance. Furthermore, the unique insights into ground- and excited-state electronic structure offered by these spectroscopic and computational studies are harmonized with a thermodynamic model of hydrogen-atom-transfer reactivity, which predicts a correlation between transition-state barriers and driving force« less

Tuning the reactivity of mononuclear nonheme manganese(iv)-oxo complexes by triflic acid

DOE PAGES

Chen, Junying; Yoon, Heejung; Lee, Yong -Min; ...

2015-04-14

Triflic acid (HOTf)-bound nonheme Mn( IV)-oxo complexes, [(L)Mn IV(O)] 2+–(HOTf) 2 (L = N4Py and Bn-TPEN; N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine and Bn-TPEN = N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethane-1,2-diamine), were synthesized by adding HOTf to the solutions of the [(L)Mn IV(O)] 2+ complexes and were characterized by various spectroscopies. The one-electron reduction potentials of the Mn IV(O) complexes exhibited a significant positive shift upon binding of HOTf. The driving force dependences of electron transfer (ET) from electron donors to the Mn IV(O) and Mn IV(O)–(HOTf) 2 complexes were examined and evaluated in light of the Marcus theory of ET to determine the reorganization energies of ET.more » The smaller reorganization energies and much more positive reduction potentials of the [(L)Mn IV(O)] 2+–(HOTf) 2 complexes resulted in greatly enhanced oxidation capacity towards one-electron reductants and para-X-substituted-thioanisoles. The reactivities of the Mn(IV)-oxo complexes were markedly enhanced by binding of HOTf, such as a 6.4 × 10 5-fold increase in the oxygen atom transfer (OAT) reaction (i.e., sulfoxidation). Such a remarkable acceleration in the OAT reaction results from the enhancement of ET from para-X-substituted-thioanisoles to the MnIV(O) complexes as revealed by the unified ET driving force dependence of the rate constants of OAT and ET reactions of [(L)Mn IV(O)] 2+–(HOTf) 2. In contrast, deceleration was observed in the rate of H-atom transfer (HAT) reaction of [(L)Mn IV(O)] 2+–(HOTf) 2 complexes with 1,4-cyclohexadiene as compared with those of the [(L)Mn IV(O)] 2+ complexes. Thus, the binding of two HOTf molecules to the Mn IV(O) moiety resulted in remarkable acceleration of the ET rate when the ET is thermodynamically feasible. When the ET reaction is highly endergonic, the rate of the HAT reaction is decelerated due to the steric effect of the counter anion of HOTf.« less

Can introduction of hydraulic fracturing fluids induce biogenic methanogenesis in the shale reservoirs?

NASA Astrophysics Data System (ADS)

Sharma, S.; Wilson, T.; Wrighton, K. C.; Borton, M.; O'Banion, B.

2017-12-01

The hydraulic fracturing fluids (HFF) injected into the shale formation are composed primarily of water, proppant and some chemical additives ( 0.5- 2% by volume). The additives contain a lot of organic and inorganic compounds like ammonium sulfate, guar gum, boric acid, hydrochloric acid, citric acid, potassium carbonate, glutaraldehyde, ethylene glycols which serve as friction reducers, gelling agents, crosslinkers, biocides, corrosion/scale inhibitors, etc. The water and additives introduced into the formation ensue a variety of microbiogechmical reactions in the reservoir. For this study produced, water and gas samples were collected from several old and new Marcellus wells in SE Pennsylvania and NE West Virginia to better understand these microbe-water-rock interactions. The carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the produced fluids and CO2 in produced gas (δ13CCO2) are highly enriched with values > +10‰ and +14 ‰ V-PDB respectively. The injected hydraulic fracturing fluid had low δ13CDIC values of < -8‰ V-PDB. The high carbon isotope values in produced fluids and gas possibly indicate 1) dissolution of 13C enriched carbonates in the host rock of reservoir, cement or drilling muds or 2) biogenic methanogenesis in the reservoir. The carbon signatures of carbonates in and around the landing zone and all possible sources of carbon put downhole were analyzed for their 13C signatures. The cement and silica sand had no detectable carbon in them. The drilling mud and carbonate veins had δ13C values of -1.8 and < 2.0 ‰ V-PDB respectively. Therefore, the high δ13CDIC signatures in produced water are possibly due to the microbial utilization of lighter carbon (12C) by microbes or methanogenic bacteria in the reservoir. It is possible that introduction of C containing nutrients like guar, methanol, methylamines, etc. stimulates certain methanogen species in the reservoir to produce biogenic methane. Genomic analysis reveals that methanogen species like Methanohalophilus or Methanolobus could be the possible sources of biogenic methane in these shale reservoirs. The evidence of microbial methanogenesis raises the possibility of enhanced gas recovery from these shales using biological amendments.

Concentration, size distribution and dry deposition of amines in atmospheric particles of urban Guangzhou, China

NASA Astrophysics Data System (ADS)

Liu, Fengxian; Bi, Xinhui; Zhang, Guohua; Peng, Long; Lian, Xiufeng; Lu, Huiying; Fu, Yuzhen; Wang, Xinming; Peng, Ping'an; Sheng, Guoying

2017-12-01

Size-segregated PM10 samples were collected in Guangzhou, China during autumn of 2014. Nine amines, including seven aliphatic amines and two heterocyclic amines, were detected using a gas chromatography-mass spectrometer after derivatization by benzenesulfonyl chloride. The total concentration of the nine amines (Ʃamines) was 79.6-140.9 ng m-3 in PM10. The most abundant species was methylamine (MA), which had a concentration of 29.2-70.1 ng m-3. MA, dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA) were the predominant amines in the samples and accounted for approximately 80% of Ʃamines in each size segment. Two heterocyclic amines, pyrrolidine (PYR) and morpholine (MOR), were detected in all samples and had average concentrations of 1.14 ± 0.37 and 1.89 ± 0.64 ng m-3, respectively, in particles with aerodynamic diameters < 3 μm. More than 80% of Ʃamines were found in particles with diameters <1.5 μm, indicating that amines are mainly enriched in fine particles. All amines exhibited a bimodal distribution with a fine mode at 0.49-1.5 μm and a coarse mode at 7.2-10 μm. The maximum contributions of amines to particles (0.21%) and amines-N to water-soluble organic nitrogen (WSON) (3.1%) were found at the sizes < 0.49 μm. The maximum contribution of amines-C to water-soluble organic carbon (WSOC) was 1.6% over the size range of 0.95-1.5 μm. The molar ratio of Ʃamines to ammonium ranged from 0.0068 to 0.0107 in particles with diameters <1.5 μm, and the maximum ratio occurred in the smallest particles (diameter< 0.49 μm). The average dry deposition flux and velocity of Ʃamines in PM10 were 7.9 ± 1.6 μg m-2 d-1 and 0.084 ± 0.0021 cm s-1, respectively. The results of this study provide essential information on the contribution of amines to secondary organic aerosols and dry removal mechanisms in urban areas.

Acid-base interactions and secondary structures of poly-L-lysine probed by 15N and 13C solid state NMR and Ab initio model calculations.

PubMed

Dos, Alexandra; Schimming, Volkmar; Tosoni, Sergio; Limbach, Hans-Heinrich

2008-12-11

The interactions of the 15N-labeled amino groups of dry solid poly-L-lysine (PLL) with various halogen and oxygen acids HX and the relation to the secondary structure have been studied using solid-state 15N and 13C CPMAS NMR spectroscopy (CP = cross polarization and MAS = magic angle spinning). For comparison, 15N NMR spectra of an aqueous solution of PLL were measured as a function of pH. In order to understand the effects of protonation and hydration on the 15N chemical shifts of the amino groups, DFT and chemical shielding calculations were performed on isolated methylamine-acid complexes and on periodic halide clusters of the type (CH3NH3(+)X(-))n. The combined experimental and computational results reveal low-field shifts of the amino nitrogens upon interaction with the oxygen acids HX = HF, H2SO4, CH3COOH, (CH3)2POOH, H3PO4, HNO3, and internal carbamic acid formed by reaction of the amino groups with gaseous CO2. Evidence is obtained that only hydrogen-bonded species of the type (Lys-NH2***H-X)n are formed in the absence of water. 15N chemical shifts are maximum when H is located in the hydrogen bond center and then decrease again upon full protonation, as found for aqueous solution at low pH. By contrast, halogen acids interact in a different way. They form internal salts of the type (Lys-NH3(+)X(-))n via the interaction of many acid-base pairs. This salt formation is possible only in the beta-sheet conformation. By contrast, the formation of hydrogen-bonded complexes can occur both in beta-sheet domains as well as in alpha-helical domains. The 15N chemical shifts of the protonated ammonium groups increase when the size of the interacting halogen anions is increased from chloride to iodide and when the number of the interacting anions is increased. Thus, the observed high-field 15N shift of ammonium groups upon hydration is the consequence of replacing interacting halogen atoms by oxygen atoms.

Mechanism for the Coupled Photochemistry of Ammonia and Acetylene: Implications for Giant Planets, Comets and Interstellar Organic Synthesis.

PubMed

Keane, Thomas C

2017-09-01

Laboratory studies provide a fundamental understanding of photochemical processes in planetary atmospheres. Photochemical reactions taking place on giant planets like Jupiter and possibly comets and the interstellar medium are the subject of this research. Reaction pathways are proposed for the coupled photochemistry of NH 3 (ammonia) and C 2 H 2 (acetylene) within the context Jupiter's atmosphere. We then extend the discussion to the Great Red Spot, Extra-Solar Giant Planets, Comets and Interstellar Organic Synthesis. Reaction rates in the form of quantum yields were measured for the decomposition of reactants and the formation of products and stable intermediates: HCN (hydrogen cyanide), CH 3 CN (acetonitrile), CH 3 CH = N-N = CHCH 3 (acetaldazine), CH 3 CH = N-NH 2 (acetaldehyde hydrazone), C 2 H 5 NH 2 (ethylamine), CH 3 NH 2 (methylamine) and C 2 H 4 (ethene) in the photolysis of NH 3 /C 2 H 2 mixtures. Some of these compounds, formed in our investigation of pathways for HCN synthesis, were not encountered previously in observational, theoretical or laboratory photochemical studies. The quantum yields obtained allowed for the formulation of a reaction mechanism that attempts to explain the observed results under varying experimental conditions. In general, the results of this work are consistent with the initial observations of Ferris and Ishikawa (1988). However, their proposed reaction pathway which centers on the photolysis of CH 3 CH = N-N = CHCH 3 does not explain all of the results obtained in this study. The formation of CH 3 CH = N-N = CHCH 3 by a radical combination reaction of CH 3 CH = N• was shown in this work to be inconsistent with other experiments where the CH 3 CH = N• radical is thought to form but where no CH 3 CH = N-N = CHCH 3 was detected. The importance of the role of H atom abstraction reactions was demonstrated and an alternative pathway for CH 3 CH = N-N = CHCH 3 formation involving nucleophilic reaction between N 2 H 4 and CH 3 CH = NH is advanced.

A Structural and Functional Elucidation of the Rumen Microbiome Influenced by Various Diets and Microenvironments

PubMed Central

Deusch, Simon; Camarinha-Silva, Amélia; Conrad, Jürgen; Beifuss, Uwe; Rodehutscord, Markus; Seifert, Jana

2017-01-01

The structure and function of the microbiome inhabiting the rumen are, amongst other factors, mainly shaped by the animal's feed intake. Describing the influence of different diets on the inherent community arrangement and associated metabolic activities of the most active ruminal fractions (bacteria and archaea) is of great interest for animal nutrition, biotechnology, and climatology. Samples were obtained from three fistulated Jersey cows rotationally fed with corn silage, grass silage or grass hay, each supplemented with a concentrate mixture. Samples were fractionated into ruminal fluid, particle-associated rumen liquid, and solid matter. DNA, proteins and metabolites were analyzed subsequently. DNA extracts were used for Illumina sequencing of the 16S rRNA gene and the metabolomes of rumen fluids were determined by 500 MHz-NMR spectroscopy. Tryptic peptides derived from protein extracts were measured by LC-ESI-MS/MS and spectra were processed by a two-step database search for quantitative metaproteome characterization. Data are available via ProteomeXchange with the identifier PXD006070. Protein- and DNA-based datasets revealed significant differences between sample fractions and diets and affirmed similar trends concerning shifts in phylogenetic composition. Ribosomal genes and proteins belonging to the phylum of Proteobacteria, particularly Succinivibrionaceae, exhibited a higher abundance in corn silage-based samples while fiber-degraders of the Lachnospiraceae family emerged in great quantities throughout the solid phase fractions. The analysis of 8163 quantified bacterial proteins revealed the presence of 166 carbohydrate active enzymes in varying abundance. Cellulosome affiliated proteins were less expressed in the grass silage, glycoside hydrolases appeared in slightest numbers in the corn silage. Most expressed glycoside hydrolases belonged to families 57 and 2. Enzymes analogous to ABC transporters for amino acids and monosaccharides were more abundant in the corn silage whereas oligosaccharide transporters showed a higher abundance in the fiber-rich diets. Proteins involved in carbon metabolism were detected in high numbers and identification of metabolites like short-chain fatty acids, methylamines and phenylpropionate by NMR enabled linkage between producers and products. This study forms a solid basis to retrieve deeper insight into the complex network of microbial adaptation in the rumen. PMID:28883813

Purification, characterization and molecular cloning of alpha-2-macroglobulin in cobia, Rachycentron canadum.

PubMed

Chuang, Wen-Hsiao; Liu, Ping-Chung; Hung, Chia-Yu; Lee, Kuo-Kau

2014-12-01

Alpha-2-macroglobulin (α-2-M) is a broad spectrum protease inhibitor which is abundant in the plasma of vertebrates and several invertebrates. The α-2-M was purified from cobia (Rachycentron canadum) plasma by a four-step procedure: poly ethylene glycol fractionation, affinity chromatography, hydrophobic interaction chromatography and ion exchange chromatography on Fast Protein liquid chromatography system in the present study. It migrated as one protein band with a molecular mass of about 360 kDa in the native state, whereas in SDS-PAGE it was about 180 kDa under non-reducing condition. This result revealed that the native protein was a dimer. In addition, it was cleaved into two different fragments of molecular mass about 93 and 87 kDa when reduced by dithiothreitol (DTT). The anti-protease activity of the purified α-2-M was apparently decreased as temperature elevated above 50 °C. The α-2-M exhibited highest protease inhibitory activity at pH 9. The results indicate that the α-2-M is a heat-labile and alkaline protease inhibitor. The purified α-2-M exhibited more than 50% protease inhibitory activity against extracellular products (ECP) of Vibrio alginolytius isolated from diseased cobia. It seems that the protease activities in ECP may be affected by the plasma α-2-M. The protease inhibitory activities of cobia plasma or purified α-2-M were decreased when incubated with 10 mM methylamine for 30 min. The α-2-M cDNA consisted of 4611 bp with an open reading frame of 4374 bp had been cloned from cobia liver. This sequence contained thioester domain (GCGEQ) and thirteen predicted N-linked glycosylation sites. In addition, the amino acid sequence of thioester domain and genes of adjacent regions of cobia α-2-M were further compared with sequences of known fish species in GenBank. The unweighted pair group method using arithmetic average (UPGMA) was employed to construct the phylogenetic trees of α-2-M among different fish species (freshwater fish, sea water fish and primitive fish), and all these fish species were then clustered into three groups. The cobia α-2-M was closer to that of sea water fish than that of freshwater fish compared basing on its similarity of amino acid sequence and phylogenetic analysis of the partial gene. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hepatotoxic constituents and toxicological mechanism of Xanthium strumarium L. fruits.

PubMed

Xue, Li-Ming; Zhang, Qiao-Yan; Han, Ping; Jiang, Yi-Ping; Yan, Rong-Di; Wang, Yang; Rahman, Khalid; Jia, Min; Han, Ting; Qin, Lu-Ping

2014-03-14

In the recent years, the international community has attached increasing importance to possible toxicity associated with Traditional Chinese Medicine (TCM). And hepatotoxicity is one of the major concerns, a fundamental pathological process induced by toxicant. This paper is in an attempt to identify the hepatotoxic components in Xanthium strumarium L. fruits (XSF) and interpret the toxicological mechanism induced by XSF. XSF extract was prepared and seven characteristic components were isolated and identified in XSF water extracts. We evaluated their hepatotoxicity effect on cell proliferation and lactate dehydrogenase (LDH) activity in L-02 and BRL liver cell line. An integrated metabonomics study using high-resolution (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy combined with multivariate statistical analysis was undertake to elucidate the hepatotoxicity mechanism induced in rats by XSF. The urine and serum metabolites were measured after treatment of rats with XSF (7.5, 15.0 and 30.0 g/kg/day) for 5 days. The results showed that atractyloside, carboxyatractyloside, 4'-desulphate-atractyloside and XSF induced significant cytotoxic effects in both L-02 and BRL liver cell lines, indicating that atractyloside, carboxyatractyloside, and 4'-desulphate-atractyloside were the toxic components of XSF. When rats were treated with XSF at 30.0 g/kg the hepatotoxicity was reflected in the changes observed in serum biochemical profiles and by the histopathological examination of the liver. The levels of VLDL/LDL, 3-HB, lactate, acetate, acetone and glutamate in serum were increased in this group, while d-glucose, choline and valine were decreased. The elevation in the levels of succinate, citrate, 2-oxo-glutamate, glycine, 3-HB, acetate, lactate, hippurate, dimethylglycine, methylamine, dimethylamine, phenylalanine and tryptophan was observed in urine, in contrast a reduction in the intensities of taurine, d-glucose, N-acetyl-glucoprotein and trimethylamine-N-oxide (TMAO) was observed. The results demonstrate that the major hepatotoxicity constituents are atractyloside, carboxyatractyloside and 4'-desulphate-atractyloside, and the hepatotoxicity of XSF involves mitochondrial inability, fatty acid metabolism, and some amino acids metabolism. This integrated (1)H NMR -based metabolic profiling approach has been able to capture and probe the metabolic alterations associated with the onset and progression of hepatotoxicity induced by XSF, and permits a comprehensive understanding of systemic toxicity for phytochemicals and other types of xenobiotic agents. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Metabolic Capabilities of Microorganisms Involved in and Associated with the Anaerobic Oxidation of Methane

PubMed Central

Wegener, Gunter; Krukenberg, Viola; Ruff, S. Emil; Kellermann, Matthias Y.; Knittel, Katrin

2016-01-01

In marine sediments the anaerobic oxidation of methane with sulfate as electron acceptor (AOM) is responsible for the removal of a major part of the greenhouse gas methane. AOM is performed by consortia of anaerobic methane-oxidizing archaea (ANME) and their specific partner bacteria. The physiology of these organisms is poorly understood, which is due to their slow growth with doubling times in the order of months and the phylogenetic diversity in natural and in vitro AOM enrichments. Here we study sediment-free long-term AOM enrichments that were cultivated from seep sediments sampled off the Italian Island Elba (20°C; hereon called E20) and from hot vents of the Guaymas Basin, Gulf of California, cultivated at 37°C (G37) or at 50°C (G50). These enrichments were dominated by consortia of ANME-2 archaea and Seep-SRB2 partner bacteria (E20) or by ANME-1, forming consortia with Seep-SRB2 bacteria (G37) or with bacteria of the HotSeep-1 cluster (G50). We investigate lipid membrane compositions as possible factors for the different temperature affinities of the different ANME clades and show autotrophy as characteristic feature for both ANME clades and their partner bacteria. Although in the absence of additional substrates methane formation was not observed, methanogenesis from methylated substrates (methanol and methylamine) could be quickly stimulated in the E20 and the G37 enrichment. Responsible for methanogenesis are archaea from the genus Methanohalophilus and Methanococcoides, which are minor community members during AOM (1–7‰ of archaeal 16S rRNA gene amplicons). In the same two cultures also sulfur disproportionation could be quickly stimulated by addition of zero-valent colloidal sulfur. The isolated partner bacteria are likewise minor community members (1–9‰ of bacterial 16S rRNA gene amplicons), whereas the dominant partner bacteria (Seep-SRB1a, Seep-SRB2, or HotSeep-1) did not grow on elemental sulfur. Our results support a functioning of AOM as syntrophic interaction of obligate methanotrophic archaea that transfer non-molecular reducing equivalents (i.e., via direct interspecies electron transfer) to obligate sulfate-reducing partner bacteria. Additional katabolic processes in these enrichments but also in sulfate methane interfaces are likely performed by minor community members. PMID:26870011

Possible survival of simple amino acids to X-ray irradiation in ice: the case of glycine

NASA Astrophysics Data System (ADS)

Pernet, A.; Pilmé, J.; Pauzat, F.; Ellinger, Y.; Sirotti, F.; Silly, M.; Parent, Ph.; Laffon, C.

2013-04-01

Context. Glycine, the simplest of amino acids, has been found in several carbonaceous meteorites collected on Earth, though its presence in the interstellar medium (ISM) has never been confirmed as of today. It is now considered that its synthesis took place in the icy mantles of interstellar grains, but it remains unclear how glycine, once synthesized and trapped in interplanetary particles, survives during the transfer to the Earth. Aims: Assuming that glycine was effectively formed in the ice, we address the question of its resistance to a solar-like radiation field and look for the possible molecular remnants that would be useful tracers of its former existence. Methods: The search was conducted using an interdisciplinary approach that mixes, on the one hand, irradiations in ultra high vacuum at 30 K on the TEMPO beam line of the synchrotron SOLEIL, simultaneously with near-edge X-ray absorption spectroscopy (NEXAFS) measurements, and on the other hand, quantum calculations to determine the energetics of the fragmentations and the relative stability of the different byproducts. The last points were addressed by means of density functional theory (DFT) simulations followed by high-level post Hartree-Fock calculations when more accurate relative energies were necessary. The constraints of an icy environment deserved special attention and the ice was modeled by a polarizable continuum medium that relies on the dielectric constant of water ice at 10-50 K. Results: Destruction of glycine is observed in the first seconds of irradiation, and carbon dioxide (CO2) and methylamine (CH3NH2) are formed. Carbon monoxide (CO), methanimine (CH2NH) and hydrogen cyanide (HCN) are also produced in secondary reactions. The amino acid destruction is the same for pure glycine and glycine in ice, indicating that the OH radicals released by the water matrix is barely involved in the photolytic process; however, these radicals are involved in the production of the secondary byproducts through dehydrogenation reactions as shown by ab initio quantum chemical simulation presented in this article along with the experimental results. Conclusions: The experiments show that glycine is only partially destroyed. Its abundance is found to stay at a level of ~30% of the initial concentration, for an irradiation dose equivalent to three years of solar radiation (at a distance of one astronomical unit). This result supports the hypothesis that, if trapped in protected icy environments and/or in the interior of interplanetary particles and meteorites, glycine may partly resist the radiation field to which it is submitted and, accordingly, survives its journey to the Earth.

Microbial Metabolic Diversity Study of the Kuantzuling Mud Hot Spring in the Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Lin, Y.; Wang, P.; Lin, L.

2009-12-01

Organic carbon, sulfate, methane, and hydrogen are available for microorganisms to carry on diverse metabolisms in the Kuantzuling mud hot spring, southwestern Taiwan. On the basis of bioenergetic evaluations and environmental DNA analyses, previous studies have inferred diverse metabolic capabilities, including methanogenesis, sulfate reduction, fermentation, aerobic heterotrophy and methanotrophy. However, active metabolisms have never been confirmed by cultivation-based analysis. Due to the temperature fluctuation of the Kuantzuling mud spring, this study performed a set of enrichment experiments at temperatures ranging from 25oC to 80oC to understand the activity and interaction among microorganisms at various temperatures. Pure stains were also isolated along with their physiological tests to reveal their possible roles in this terrestrial hot spring ecosystem. According to the geochemical and molecular data, nine types of media were designed to enrich different kinds of metabolisms in the slurry. Positive enrichments were obtained in all types of media, but not at all investigated temperatures. Methanogens using acetate, methanol, and hydrogen and carbon dioxide, sulfate reducers, thiosulfate reducers, fermenters, aerobic heterotrophs could be enriched at temperatures higher than 50oC and even 80oC. Methanogen using methylamine and aerobic methanotroph can only be enriched at temperatures lower than 50 oC. This result is generally consistent with previous energetic evaluation and molecular analysis. It also inferred that microbial assemblages possessing diverse metabolisms were either competitive or collaborative to each other for degradation of organic carbon or carbon cycling. Two strains were isolated from aerobic heterotrophic media. The 16S rDNA gene sequence of one strain exhibited a very close affiliation (at a similarity of 99%) with Meiothermus ruber strain SPS242 and that of the other showed an affiliation to that of Rhodobacter vinaykumarii JA123 at the similarity of 95%. The former grew at the pH values between 5 and 9, at the temperatures ranging from 20 to 70oC with the optimal growth temperature at 60oC, while the later can grow at the pH values between 6 and 9, at the temperatures ranging from 20 to 60oC with the optimal growth temperature at 50oC. The Kuantzuling mud spring harbors diverse microorganisms. Such a wide range of physiological capability might represent an unstable ecosystem constantly exposed to the substantial environmental fluctuations, such as temperature, oxygen content and fluid source.

Grape yield to soil N-NO3- ratio can explain the different levels of biogenic amines in wine from two vineyards in the AOC Rioja (Spain)

NASA Astrophysics Data System (ADS)

Pérez-Álvarez, Eva Pilar; Garde-Cerdán, Teresa; Santamaría, Pilar; García-Escudero, Enrique; Peregrina, Fernando

2014-05-01

Plant N status may affect the grape amino acid concentration, which act as precursors in the formation of biogenic amines in wine. Biogenic amines have negative effects on human health and so they reduce the wine quality. The objective of this study was to analyze, at bloom (when the vine N demand peaks) if both the available soil N and the N concentration in the leaf could explain the amino acid concentration in the must as well as the biogenic amines in wines from AOC Rioja. Two plots with cv. Tempranillo (Vitis vinifera L.) vines grafted on R-110 rootstock were chosen: "La Grajera" (2,998 plants ha-1) and "Nájera" (2,849 plants ha-1), both plots with a traditional soil tillage management system and classified according to the American Soil Taxonomy as Typic Haloxerepts and Oxyaquic Xerorthent, respectively. Both soils had a pH higher than 7, a silty loam texture and organic matter values lower than 2%. The climatic conditions were described as semiarid Mediterranean according to the UNESCO aridity index. In each vineyard, three non-adjacent experimental plots with 3 rows of 30 vines each, were set out. No fertilizer was applied during the project. Each plot was sampled in 2009, 2010 and 2011 seasons at bloom, analyzing the available soil N-NO3- at 0-15 and 15-45 cm depth and expressing the results in kg ha-1 by means of the bulk density of soil and the coarse elements content. Also at bloom, 30 leaves per experimental plot were collected and their N concentration was analyzed. At harvest, 200 berries were taken from each plot and the amino acid content in the musts was determined by HPLC. In addition, 100 kg of grapes from each plot were taken in order to elaborate wine according to the AOC Rioja common winemaking practices. When the winemaking process was finished, the concentration of biogenic amines in the wine (histamine, methylamine, ethylamine, tyramine, putrescine, cadeverine, phenylethylamine and isoamylamine) was determined by HPLC. Our results showed that both the total amino acid content in the must and the sum of biogenic amines in the wine were higher in 'La Grajera' than 'Nájera'. Positive correlations were observed between the total biogenic amine content and leaf N (R2=0.33, p=0.007), soil N-NO3- (R2= 0.43, p

Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome.

PubMed

Pinto-Sanchez, Maria Ines; Hall, Geoffrey B; Ghajar, Kathy; Nardelli, Andrea; Bolino, Carolina; Lau, Jennifer T; Martin, Francois-Pierre; Cominetti, Ornella; Welsh, Christopher; Rieder, Amber; Traynor, Jenna; Gregory, Caitlin; De Palma, Giada; Pigrau, Marc; Ford, Alexander C; Macri, Joseph; Berger, Bernard; Bergonzelli, Gabriela; Surette, Michael G; Collins, Stephen M; Moayyedi, Paul; Bercik, Premysl

2017-08-01

Probiotics can reduce symptoms of irritable bowel syndrome (IBS), but little is known about their effects on psychiatric comorbidities. We performed a prospective study to evaluate the effects of Bifidobacterium longum NCC3001 (BL) on anxiety and depression in patients with IBS. We performed a randomized, double-blind, placebo-controlled study of 44 adults with IBS and diarrhea or a mixed-stool pattern (based on Rome III criteria) and mild to moderate anxiety and/or depression (based on the Hospital Anxiety and Depression scale) at McMaster University in Canada, from March 2011 to May 2014. At the screening visit, clinical history and symptoms were assessed and blood samples were collected. Patients were then randomly assigned to groups and given daily BL (n = 22) or placebo (n = 22) for 6 weeks. At weeks 0, 6, and 10, we determined patients' levels of anxiety and depression, IBS symptoms, quality of life, and somatization using validated questionnaires. At weeks 0 and 6, stool, urine and blood samples were collected, and functional magnetic resonance imaging (fMRI) test was performed. We assessed brain activation patterns, fecal microbiota, urine metabolome profiles, serum markers of inflammation, neurotransmitters, and neurotrophin levels. At week 6, 14 of 22 patients in the BL group had reduction in depression scores of 2 points or more on the Hospital Anxiety and Depression scale, vs 7 of 22 patients in the placebo group (P = .04). BL had no significant effect on anxiety or IBS symptoms. Patients in the BL group had a mean increase in quality of life score compared with the placebo group. The fMRI analysis showed that BL reduced responses to negative emotional stimuli in multiple brain areas, including amygdala and fronto-limbic regions, compared with placebo. The groups had similar fecal microbiota profiles, serum markers of inflammation, and levels of neurotrophins and neurotransmitters, but the BL group had reduced urine levels of methylamines and aromatic amino acids metabolites. At week 10, depression scores were reduced in patients given BL vs placebo. In a placebo-controlled trial, we found that the probiotic BL reduces depression but not anxiety scores and increases quality of life in patients with IBS. These improvements were associated with changes in brain activation patterns that indicate that this probiotic reduces limbic reactivity. ClinicalTrials.gov no. NCT01276626. Copyright © 2017. Published by Elsevier Inc.

Fatty acid sulphoalkyl amides and esters as cosmetic surfactants.

PubMed

Petter, P J

1984-10-01

Synopsis A review is given of the manufacture, properties and applications of the anionic surfactants commonly known as taurates and isethionates (fatty acid sulphoalkyl amides and esters, respectively). Originally developed in the 1930s for textile processing, these surfactants are used increasingly in the cosmetic field, particularly those derived from coconut fatty acid. Both types are produced from sodium isethionate, HO degrees C(2)H(4)SO(3)Na. The acyl isethionate, R degrees COO degrees C(2)H(4)SO(3)Na, is obtained by reaction with a fatty acid ('direct process'). or fatty acid chloride ('indirect process'). The direct process is cheaper but requires extreme conditions which can lead to discoloration of the product and a loss of shorter chain fatty acid components. The N-methyl-N-acyltaurate, R degrees CON(R(1))C(2)H(4)SO(3)Na, is obtained by Schotten-Baumann reaction of a fatty acid chloride with N-methyltaurine, which is derived from sodium isethionate via methylamine. Taurates and isethionates retain the benefits of the soaps to which they are structurally similar, but chemical modifications have eliminated many undesirable features. Thus they combine good detergency and wetting with high foaming, and maintain their performance in hard or salt water. Taurates are stable to hydrolysis over the whole pH range. Isethionates are prone to hydrolysis at high (>8) or low (<5) pH, but this does not normally present a problem in cosmetic formulations. Above all, these surfactants are characterized by their extreme mildness to skin. Syndet and syndet/soap bars based on isethionate can be formulated at neutral pH ('Dove type'bars) instead of the alkaline pH of soap, and have been shown in various studies to be milder than soap and better tolerated by the young, the old and those with sensitive skins. Similarly, isethionates have been shown to be less irritating than other anionic or amphoteric surfactants used in cosmetics. The difference has been related to the negligible effect of isethionate on the water-binding capacity of stratum corneum. Other cosmetic applications besides toilet bars include shampoos (excellent cleaning, mild to scalp, some hair conditioning effects), liquid soaps (mild for all-over body use), bubble baths (copious stable foam, efficient lime soap dispersal, low irritancy), skin creams and lotions (emulsification, alleviation of 'dry skin'), baby care products (ultra-mild cleansing bars and milks, impregnated baby wipes) and oral products (foaming agents with low toxicity for toothpastes and mouthwashes).

Progressive response of large intestinal bacterial community and fermentation to the stepwise decrease of dietary crude protein level in growing pigs.

PubMed

Peng, Yu; Yu, Kaifan; Mu, Chunlong; Hang, Suqin; Che, Lianqiang; Zhu, Weiyun

2017-07-01

The study aimed to determine the effects of reduction of dietary crude protein (CP) level with balanced essential amino acids (EAA) on intestinal bacteria and their metabolites of growing pigs. Forty pigs (initial BW 13.50 ± 0.50 kg, 45 ± 2 days of age) were randomly assigned to four dietary treatments containing CP levels at 20.00% (normal crude protein, NP); 17.16% (medium crude protein, MP); 15.30% (low crude protein, LP); and 13.90% (extremely low crude protein, ELP), respectively. Crystalline AAs were added to meet the EAA requirement of pigs. After 4-week feeding, eight pigs per treatment (n = 8) were randomly selected and slaughtered for sampling of ileal, cecal, and colonic digesta and mucosa. Pigs with moderately reduced CP level had increased bacterial diversity, with the Shannon diversity indices for the colon digesta in the LP group and mucosa in the MP and LP groups significantly (P < 0.05) higher than those in the NP and ELP groups. As the CP level reduces, the Bifidobacterium population were linearly decreased (P < 0.05) both in ileum, cecum, and colon, and the ELP group had the lowest Bifidobacterium population in the cecum and colon, with its value significantly lower than NP and MP groups (P < 0.05). However, the ELP group had the highest population of Escherichia coli in the colon, with its value significantly higher than the LP group (P < 0.05). For bacterial metabolites, as CP level decreased, total short-chain fatty acid (T-SCFA), acetate, and butyrate were linearly increased (linear, P < 0.05) in the ileum, while all SCFAs except formate in the cecum and T-SCFA and acetate in the colon, were linearly decreased (P < 0.05). Reducing CP level led to a linear decrease of microbial crude protein (MCP) in the ileum (P < 0.05) and ammonia in all intestine segments (P < 0.05). The spermidine in cecum and total amines, cadaverine, methylamine, and spermidine in colon were shown a quadratic change (P < 0.05) as dietary CP decreases, with the highest concentration in LP group. These findings suggest that moderate reduction of dietary CP level may benefit large intestinal bacterial community and its fermentation, which was negatively affected by extremely low CP diet.

Myeloperoxidase-catalyzed incorporation of amines into proteins: role of hypochlorous acid and dichloramines.

PubMed

Thomas, E L; Jefferson, M M; Grisham, M B

1982-11-23

Myeloperoxidase-catalyzed oxidation of chloride (Cl-) to hypochlorous acid (HOCl) resulted in formation of mono- and dichloramine derivatives (RNHCl and RNCl2) of primary amines. The RNCl2 derivatives could undergo a reaction that resulted in incorporation of the R moiety into proteins. The probable mechanism was attack of RNCl2 or an intermediate formed in the decomposition of RNCl2 on histidine, tyrosine, and cystine residues and on lysine residues at high pH. Incorporation of radioactivity from labeled amines into stable, high molecular weight derivatives of proteins was measured by acid or acetone precipitation and by gel chromatography and electrophoresis. Whereas formation of RNCl2 was favored at low pH, the subsequent incorporation reaction was favored at high pH. Up to several hours were required for the maximum amount of incorporation, which was less than 10% of the label in RNCl2. For the amines tested, incorporation was in the order histamine greater than 1,2-diaminoethane greater than putrescine greater than taurine greater than lysine greater than glucosamine greater than leucine greater than methylamine. Initiation of the reaction required HOCl, and oxidized forms of bromide, iodide, or thiocyanate did not substitute. Inhibitors of incorporation fell into three classes. First, ammonia or amines competed with the labeled amine for reaction with HOCl, so that larger amounts of HOCl were required. Second, readily oxidized substances such as sulfhydryl or diketo compounds or thioethers (methionine) reduced RNCl2. Third, certain compounds competed with protein as the acceptor for the incorporation reaction. The amount required to block incorporation into protein depended on protein concentration. Among these inhibitors were imidazole compounds (histidine), phenols (tyrosine), and disulfides (glutathione disulfide, GSSG). Low yields of derivatives of histidine, tyrosine, and GSSG were detected by thin-layer chromatography. Acid-precipitable derivatives were obtained by reacting RNCl2 with polyhistidine or polytyrosine, and to a lesser extent with polylysine at high pH, but not with other poly(amino acids). Precipitable derivatives were also obtained by incubating MPO-containing extracts from leukocyte granules with hydrogen peroxide, Cl-, and labeled amines. The extracts were found to have a high content of substances with primary amino groups, which competed for incorporation. The results account for oxidative incorporation of amines into proteins in leukocytes and provide evidence that HOCl and nitrogen-chlorine (N-Cl) derivatives are formed in these cells. The characteristics of the incorporation reaction suggest that it would not contribute significantly to the antimicrobial activity of myeloperoxidase (MPO). Nevertheless, the reaction may provide a sensitive method for studying MPO action in vivo.

Spectroscopic characterization of Antarctic marine aerosol

NASA Astrophysics Data System (ADS)

Paglione, Marco; Zanca, Nicola; Rinaldi, Matteo; Dall'osto, Manuel; Simo, Rafel; Facchini, Maria Cristina; Decesari, Stefano

2017-04-01

Marine aerosol constitutes an important and not thoroughly investigated natural aerosol system. In particular, the poor knowledge of the physical-chemical properties of primary (sea-spray) and secondary particles, especially over biologically active seawaters, affects the current capability of modeling the effect of marine aerosol on climate (O'Dowd et al., 2004). In polar regions, surface seawater composition and its exchanges with the atmosphere is complicated also by the presence of sea-ice and of the variety of micro-organisms (viruses, prokaryotes and microalgae) living within it (Levasseur,2013). In the framework of the Spanish project PEGASO (Plankton-derived Emission of Gases and Aerosols in the Southern Ocean) submicron aerosol samples were collected during a 6 weeks long oceanographic cruise (2nd January 2015 - 11th February 2015) conducted in the regions of Antarctic Peninsula, South Orkney and South Georgia Islands, an area of the Southern Ocean characterized every summer by both large patches of productive waters (phytoplankton blooms) and sea-ice cover. The collected samples were analyzed by means of proton-Nuclear Magnetic Resonance (H-NMR) spectroscopy with aim of organic compounds characterization in terms of functional groups and specific molecular tracers identification (Decesari et al., 2011). H-NMR spectral features resulted quite variable among the different samples both in terms of relative abundance of main functional groups and in terms of presence of specific compounds. In all the samples were found biogenic markers, like low-molecular-weight alkyl-amines and methanesulphonate (MSA), of secondary origin (formed by the condensation of vapors onto particles). Resonance signals of other aliphatic compounds of possible primary origin, like lipids, aminoacids (e.g. alanine) and sugars (e.g. sucrose) are present in variable concentrations in the samples. A hierarchical cluster analysis applied on the NMR spectra allowed to identify similarities in the samples collected close the Weddell-Sea area, showing an enhancement of biogenic alkyl-amines (including mono-, di- and tri-methylamine) and MSA and suggesting a common source probably linked with the sea-ice cover dominating that region. As such, our results point to secondary organic aerosol (SOA) sources from precursors emitted by sea ice regions around Antarctica and call for better representation of the sea ice-ocean-atmosphere biogeochemistry in Earth system models. References: Decesari, S. et al., JGR-Atmospheres 116 (2011). Levasseur, M., Nature Geoscience, Vol. 6, September (2013). O'Dowd, C. et al., Nature 431, 676-680 (2004). Acknowledgments: The cruise was funded by the Spanish Ministry of Economy through projects PEGASO (CTM2012-37615) and Bio-Nuc (CGL2013-49020-R), and by the EU though the FP7-PEOPLE-2013-IOF program (Project number 624680, MANU - Marine Aerosol NUcleations).

Magnetic circular dichroism and computational study of mononuclear and dinuclear iron(iv) complexes† †Electronic supplementary information (ESI) available: VT MCD spectra, VT and VTVH MCD intensity analysis of complex 1, energies, S x, S z values and Boltzmann populations of S = 1 magnetic sublevels as a function of the applied magnetic field, derivation of the excited states arising from the 1b2 → 2b1 transition, determination of the C-term sign of band 1 and the E(2e → 2a1) transitions for complex 1, VTVH MCD spectra, VTVH simulations and the computed MCD spectrum of complex 2. See DOI: 10.1039/c4sc03268c Click here for additional data file.

PubMed Central

Xue, Genqiang; Krivokapic, Itana; Petrenko, Taras

2015-01-01

High-valent iron(iv)-oxo species are key intermediates in the catalytic cycles of a range of O2-activating iron enzymes. This work presents a detailed study of the electronic structures of mononuclear ([FeIV(O)(L)(NCMe)]2+, 1, L = tris(3,5-dimethyl-4-methoxylpyridyl-2-methyl)amine) and dinuclear ([(L)FeIV(O)(μ-O)FeIV(OH)(L)]3+, 2) iron(iv) complexes using absorption (ABS), magnetic circular dichroism (MCD) spectroscopy and wave-function-based quantum chemical calculations. For complex 1, the experimental MCD spectra at 2–10 K are dominated by a broad positive band between 12 000 and 18 000 cm–1. As the temperature increases up to ∼20 K, this feature is gradually replaced by a derivative-shaped signal. The computed MCD spectra are in excellent agreement with experiment, which reproduce not only the excitation energies and the MCD signs of key transitions but also their temperature-dependent intensity variations. To further corroborate the assignments suggested by the calculations, the individual MCD sign for each transition is independently determined from the corresponding electron donating and accepting orbitals. Thus, unambiguous assignments can be made for the observed transitions in 1. The ABS/MCD data of complex 2 exhibit ten features that are assigned as ligand-field transitions or oxo- or hydroxo-to-metal charge transfer bands, based on MCD/ABS intensity ratios, calculated excitation energies, polarizations, and MCD signs. In comparison with complex 1, the electronic structure of the FeIV 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 O site is not significantly perturbed by the binding to another iron(iv) center. This may explain the experimental finding that complexes 1 and 2 have similar reactivities toward C–H bond activation and O-atom transfer. PMID:26417426

A Computational Investigation of the Oxidative Deboronation of BoroGlycine, H2N–CH2–B(OH)2, Using H2O and H2O2

PubMed Central

Larkin, Joseph D.; Markham, George D.; Milkevitch, Matt; Brooks, Bernard R.; Bock, Charles W.

2014-01-01

We report results from a computational investigation of the oxidative deboronation of BoroGlycine, H2N–CH2–B(OH)2, using H2O and H2O2 as the reactive oxygen species (ROS) to yield aminomethanol, H2N–CH2–OH; these results complement our study on the protodeboronation of BoroGlycine to produce methylamine, H2N–CH3 (Larkin et al. J. Phys. Chem. A, 111, 6489–6500, 2007). Second-order Møller-Plesset (MP2) perturbation theory with Dunning-Woon correlation-consistent (cc) basis sets were used for the calculations with comparisons made to results from Density Functional Theory (DFT) at the PBE1PBE/6-311++G(d,p)(cc-pVDZ) levels. The effects of a bulk aqueous environment were also incorporated into the calculations employing PCM and CPCM methodology. Using H2O as the ROS, the reaction H2O + H2N–CH2–B(OH)2 → H2N–CH2–OH + H–B(OH)2 was calculated to be endothermic, the value of ΔH2980 was +12.0 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and +13.7 kcal/mol in PCM aqueous media; the corresponding value for the activation barrier, ΔH‡, was +94.3 kcal/mol relative to the separated reactants in vacuo and +89.9 kcal/mol in PCM aqueous media. In contrast, the reaction H2O2 + H2N–CH2–B(OH)2 → H2N–CH2–OH + B(OH)3 was calculated to be highly exothermic with a ΔH2980 value of −100.9 kcal/mol at the MP2(FC)/cc-pVTZ computational level in vacuo and −99.6 kcal/mol in CPCM aqueous media; the highest-energy transition state for the multi-step process associated with this reaction involved the rearrangement of H2N–CH2–B(OH)(OOH) to H2N–CH2–O–B(OH)2 with a ΔH‡ value of +23.2 kcal/mol in vacuo relative to the separated reactants. These computational results for BoroGlycine are in accord with the experimental observations for the deboronation of the FDA approved anti-cancer drug Bortezomib (Velcade™, PS-341) where it was found to be the principle deactivation pathway. (Labutti et al. Chem. Res. Toxicol., 19, 539–546, 2006). PMID:19810757

Topologically and geometrically flexible structural units in seven new organically templated uranyl selenates and selenite–selenates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gurzhiy, Vladislav V., E-mail: vladgeo17@mail.ru; Kovrugin, Vadim M.; Tyumentseva, Olga S.

2015-09-15

Single crystals of seven novel uranyl oxysalts of selenium with protonated methylamine molecules, [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)] (I), [C{sub 2}H{sub 8}N]{sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O)] (II), [C{sub 4}H{sub 15}N{sub 3}][H{sub 3}O]{sub 0.5}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 2.93}(SeO{sub 3}){sub 0.07}(H{sub 2}O)](NO{sub 3}){sub 0.5} (III), [C{sub 2}H{sub 8}N]{sub 3}[H{sub 5}O{sub 2}][(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}(H{sub 2}O){sub 2}]{sub 2}(H{sub 2}O){sub 5} (IV), [C{sub 2}H{sub 8}N]{sub 2}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 4}(HSeO{sub 3})(H{sub 2}O)](H{sub 2}SeO{sub 3}){sub 0.2} (V), [C{sub 4}H{sub 12}N]{sub 3}[H{sub 3}O][(UO{sub 2}){sub 3}(SeO{sub 4}){sub 5}(H{sub 2}O)] (VI), and [C{sub 2}H{sub 8}N]{sub 3}(C{sub 2}H{sub 7}N)[(UO{sub 2}){sub 3}(SeO{sub 4}){submore » 4}(HSeO{sub 3})(H{sub 2}O)] (VII) have been prepared by isothermal evaporation from aqueous solutions. Their crystal structures have been solved by direct methods and their uranyl selenate and selenite–selenate units investigated using black-and-white graphs from the viewpoints of topology of interpolyhedral linkages and isomeric variations. The crystal structure of IV is based upon complex layers with unique topology, which has not been observed previously in uranyl selenates. Investigations of the statistics and local distribution of the U–O{sub br}–Se bond angles demonstrates that shorter angles associate with undulations, whereas larger angles correspond to planar areas of the uranyl selenite layers. - Graphical abstract: Crystal structures of the seven novel Se-contaning uranyl oxysalts that contain protonated organic molecules as interlayer species have been investigated from the viewpoints of topology of interpolyhedral linkages, isomeric variations and flexibility of structural units. - Highlights: • Single crystals of seven novel uranyl oxysalts were prepared by evaporation method. • The graph theory was used for investigation of topologies of structural units. • The method of orientation matrices was applied to distinguish geometrical isomers. • The flexibility of structural complexes specifies the undulation of layered structural units.« less

The Coupled Photochemistry of Ammonia and Acetylene: Applications to the Atmospheric Chemistry on Jupiter

NASA Astrophysics Data System (ADS)

Keane, Thomas Christopher

1995-01-01

The existence of hydrogen cyanide (HCN) in the highly reducing atmosphere of Jupiter was a surprising discovery (Tokunaga et al., 1981). Previous studies that tested the theoretical proposal of Kaye and Strobel (1983a) that the HCN observed on Jupiter is the result of NH _3 photolysis in the presence of C _2H_2 established that acetonitrile (CH_3CN) and acetaldazine (CH _3CH=NN=CHCH_3) are important intermediates in HCN formation (Ferris and Ishikawa, 1988). In this study the rates of formation of these compounds, and of other recently detected intermediates, have been determined in static photolysis experiments at 296 K and at temperatures which are closer to those found in the Jovian atmosphere. Experiments were also performed, using a photochemical flow reactor, that allowed for a better approximation of the mixing ratios of reactant gases (8 times 10^{ -4} for NH_3 and 1 times 10^{-5} for C_2H_2) and the process of advection in the Jovian atmosphere. An overall reaction pathway for HCN formation is proposed. Major intermediates and products found in these laboratory simulations that have not yet been observed on Jupiter are acetonitrile (CH_3CN), acetaldazine (CH_3CH=NN=CHCH _3), acetaldehyde hydrazone (CH_3 CH=NNH_2), N-ethylethylideneimine (CH_3CH=NC_2H _5), ethylamine (C_2H _5NH_2) and methylamine (CH _3NH_2). HCN is formed by the photolysis of NH_3/C _2H_2 mixtures (40:5 torr) at 296 K and at low temperature (208 K, 195 K and 180 K) with the highest quantum efficiency for HCN formation observed at 180 K. In static experiments using a high partial pressure of H_2 the quantum yield for HCN formation decreased three-fold relative to the 296 K photolyses when no H_2 was used. An additional ten-fold decrease in the quantum yield for HCN formation occurred when using the flow system. The quantum yields for acetaldazine and acetaldehyde hydrazone formation were found to vary inversely to that for HCN formation. For those static experiments which best simulate Jovian reaction conditions (H_2: NH_3 : C_2H_2 = 600: 7.5: 5 torr, 180 K) the following products and their quantum yields for formation were obtained: C_2H_4 (0.129), CH_3 CH=NN=CHCH_3 (0.079), CH _3CH=NNH_2 (0.049), C_2H_5NH_2 (0.038), CH_3NH_2 (0.003), CH_3CN (0.002), HCN (0.001) and CH_3CH=NC _2H_5 (0.001).

Organometal Halide Perovskite Solar Absorbers and Ferroelectric Nanocomposites for Harvesting Solar Energy

NASA Astrophysics Data System (ADS)

Hettiarachchi, Chaminda Lakmal

Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH3NH3PbI3-xClx), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH3NH3PbI3-xClx perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid and methylamine) are quite expensive. This work describes a novel, single-step, simple, and cost-effective solution approach to prepare CH3NH3PbI3-xClx thin films by the direct reaction of the commercially available CH3NH 3Cl (or MACl) and PbI2. A detailed analysis of the structural and optical properties of CH3NH3PbI3-xCl x thin films deposited by aerosol assisted chemical vapor deposition is presented. Optimum growth conditions have been identified. It is shown that the deposited thin films are highly crystalline with intense optical absorbance. Charge carrier separation of these thin films can be enhanced by establishing a local internal electric field that can reduce electron-hole recombination resulting in increased photo current. The intrinsic ferroelectricity in nanoparticles of Barium Titanate (BaTiO3 -BTO) embedded in the solar absorber can generate such an internal field. A hybrid structure of CH3NH 3PbI3-xClx perovskite and ferroelectric BTO nanocomposite FTO/TiO2/CH3NH3PbI3-xClx : BTO/P3HT/Cu as a new type of photovoltaic device is investigated. Aerosol assisted chemical vapor deposition process that is scalable to large-scale manufacturing was used for the growth of the multilayer structure. TiO 2 and P3HT with additives were used as ETL and HTL respectively. The growth process of the solar absorber layer includes the nebulization of a mixture of PbI2 and CH3NH3Cl perovskite precursors and BTO nanoparticles dissolved in DMF, and injection of the aerosol into the growth chamber and subsequent deposition on TiO2. While high percentage of BTO in the film increases the carrier separation, it also leads to reduced carrier generation. A model was developed to guide the optimum BTO nanoparticle concentration in the nanocomposite films. Characterization of perovskite solar cells indicated that ferroelectric polarization of BTO nanoparticles leads to the increase of the width of depletion regions in the perovskite layer hence the photo current was increased by one order of magnitude after poling the devices. The ferroelectric polarization of BTO nanoparticles within the perovskite solar absorber provides a new perspective for tailoring the working mechanism and photovoltaic performance of perovskite solar cells.

Investigations of Methane Production in Hypersaline Environments

NASA Technical Reports Server (NTRS)

Bebout, Brad M.

2015-01-01

The recent reports of methane in the atmosphere of Mars, as well as the findings of hypersaline paleo-environments on that planet, have underscored the need to evaluate the importance of biological (as opposed to geological) trace gas production and consumption. Methane in the atmosphere of Mars may be an indication of life but might also be a consequence of geologic activity and/or the thermal alteration of ancient organic matter. Hypersaline environments have now been reported to be extremely likely in several locations in our solar system, including: Mars, Europa, and Enceladus. Modern hypersaline microbial mat communities, (thought to be analogous to those present on the early Earth at a period of time when Mars was experiencing very similar environmental conditions), have been shown to produce methane. However, very little is known about the physical and/or biological controls imposed upon the rates at which methane, and other important trace gases, are produced and consumed in these environments. We describe here the results of our investigations of methane production in hypersaline environments, including field sites in Chile, Baja California Mexico, California, USA and the United Arab Emirates. We have measured high concentrations of methane in bubbles of gas produced both in the sediments underlying microbial mats, as well as in areas not colonized by microbial mats in the Guerrero Negro hypersaline ecosystem, Baja California Mexico, in Chile, and in salt ponds on the San Francisco Bay. The carbon isotopic (d13C) composition of the methane in the bubbles exhibited an extremely wide range of values, (ca. -75 per mille ca. -25 per mille). The hydrogen isotopic composition of the methane (d2H) ranged from -60 to -30per mille and -450 to -350per mille. These isotopic values are outside of the range of values normally considered to be biogenic, however incubations of the sediments in contact with these gas bubbles reveals that the methane is indeed being produced by these sediments. Substrate limitation of methanogenesis in these environments, and not methane oxidation, would explain the isotopic values of the methane in these environments. Incubations with both isotopically labeled and unlabeled putative substrates for methanogenesis have shown that the substrates most important for methanogenesis in these environments are the so-called non-competitive substrates, e.g., methylamines, dimethylsulfide, and methanol. Acetate and bicarbonate appear not to be important substrates for methanogens in these environments. Extraction of DNA and analysis of a gene used for methane production (mcrA) has revealed that the community composition of methanogens is consistent with organisms known to use non-competitive substrates. Our work has shown that hypersaline environments have the potential to both produce and preserve methane for analysis, e.g., by capable rovers. Our work expends the range of methane isotopic values now known to be produced by active methanogenesis

Interaction of the HIV NCp7 Protein with Platinum(II) and Gold(III) Complexes Containing Tridentate Ligands.

PubMed

Bernardes, Victor H F; Qu, Yun; Du, Zhifeng; Beaton, James; Vargas, Maria D; Farrell, Nicholas P

2016-11-07

The human immunodeficiency virus (HIV) nucleocapsid protein (NCp7) plays significant roles in the virus life cycle and has been targeted by compounds that could lead to its denaturation or block its interaction with viral RNA. Herein, we describe the interactions of platinum(II) and gold(III) complexes with NCp7 and how the reactivity/affinity of potential inhibitors can be modulated by judicious choice of ligands. The interactions of [MCl(N 3 )] n+ (M = Pt 2+ (n = 1) and Au 3+ (n = 2); N 3 = tridentate chelate ligands: bis(2-pyridylmethyl)methylamine (Mebpma, L 1 ) and bis(2-pyridylmethyl)amine (bpma, L 2 ) with the C-terminal zinc finger of NCp7 (ZF2) were investigated by electrospray ionization-mass spectroscopy (ESI-MS). Mass spectra from the incubation of [MCl(Mebpma)] n+ complexes (PtL 1 and AuL 1 ) with ZF2 indicated that they were more reactive than the previously studied diethylenetriamine-containing analogues [MCl(dien)] n+ . The initial product of reaction of PtL 1 with ZF2 results in loss of all ligands and release of zinc to give the platinated apopeptide {PtF} (F = apopeptide). This is in contrast to the incubation with [PtCl(dien)] + , in which {Pt(dien)}-peptide adducts are observed. Incubation of the Au 3+ complex AuL 1 with ZF2 gave Au x F n+ species (x = 1, 2, 4, F = apopeptide) again with loss of all ligands. Furthermore, the formally substitution-inert analogues [Pt(N 3 )L] 2+ (L = 4-methylpyridine (4-pic), 4-dimethylaminopyridine (dmap), and 9-ethylguanine (9-EtGua)) were prepared to examine stacking interactions with N-acetyltryptophan (N-AcTrp), the Trp-containing ZF2, and the "full" two-finger NCp7 itself using fluorescence quenching titration. Use of bpma and Mebpma gave slightly higher affinity than analogous [Pt(dien)L)] 2+ complexes. The dmap-containing complexes (PtL 1 a and PtL 2 a) had the greatest association constants (K a ) for N-AcTrp and ZF2 peptide. The complex PtL 1 a had the highest K a when compared with other known Pt 2+ analogues: [Pt(dien)(9-EtGua)] 2+ < [Pt(bpma)(9-EtGua)] 2+ < [Pt(dien)(dmap)] 2+ < PtL 2 a < PtL 1 a. A K a value of ca. 40.6 ± 1.0 × 10 3 M -1 was obtained for the full NCp7 peptide with PtL 1 a. In addition, the mass spectrum of the interaction between ZF2 and PtL 1 a confirms formation of a 1:1 PtL 1 a/ZF2 adduct. The reactivity of selected complexes with sulfur-containing amino acid N-acetylcysteine (N-AcCys) was also investigated by 195 Pt and 1 H NMR spectroscopy and ESI-MS. The precursor compounds [PtCl(N 3 )] + PtL 1 and PtL 2 reacted readily, whereas their [Pt(N 3 )L] 2+ analogues PtL 1 a and PtL 2 a were inert to substitution.

Organic/carbon nanotubes hybrid thin films for chemical detection

NASA Astrophysics Data System (ADS)

Banimuslem, Hikmat Adnan

Metallophthalocyanines (MPcs) are classified as an important class of conjugated materials and they possess several advantages attributed to their unique chemical structure. Carbon nanotubes (CNT), on the other hand, are known to enhance the properties of nano-composites in the conjugated molecules, due to their one dimensional electronic skeleton, high surface area and high aspect ratio. In this thesis, work has been carried out on the investigation of different substituted metal-phthalocyanines with the aim of developing novel hybrid film structures which incorporates these phthalocyanines and single-walled carbon nanotubes (SWCNT) for chemical detection applications. Octa-substituted copper phthalocyanines (CuPcR[8]) have been characterised using UV-visible absorption spectroscopy. Obtained spectra have yielded an evidence of a thermally induced molecular reorganization in the films. Influence of the nature of substituents in the phthalocyanine molecule on the thin films conductivity was also investigated. Octa-substituted lead (II) phthalocyanines (PbPcR[8]) have also been characterized using UV-visible spectroscopy. Sandwich structures of ITO/PbPcR[8]/In were prepared to investigate the electronic conduction in PbPcR[8]. The variation in the J(V) behavior of the films as a result of heat treatment is expected to be caused by changes in the alignment inside the columnar stacking of the molecules of the films. Thin films of non-covalently hybridised SWCNT and tetra-substituted copper phthalocyanine (CuPcR[4]) molecules have been produced. FTIR, DC conductivity, SEM and AFM results have revealed the [mathematical equation]; interaction between SWCNTs and CuPCR[4] molecules and shown that films obtained from the acid-treated SWCNTs/CuPcR[4] hybrids demonstrated more homogenous surface. Thin films of pristine CuPCR[4] and CuPcR[4]/S WCNT were prepared by spin coating onto gold-coated glass slides and applied as active layers for the detection of benzo[a]pyrene, pentachlorophenol (PCP), 2-chlorophenol, diuron and simazine in water as well as amines vapours in ambient air utilizing total internal reflection spectroscopic ellipsometry (TIRE) as an optical detection method. Different concentrations of pesticides in water ranging from 1 to 25 mug/L have been examined. It was revealed that the shifts in [mathematical equation] spectra of CuPcR[4]SWCNT films were evidently larger than those produced by the pristine CuPcR[4] films, indicating largely improved films' sensitivity of the hybrid films. Adsorption of amines onto films' surfaces has been realised by monitoring changes in the phase shift [mathematical equation] of TIRE. Methylamine has shown higher sensitivity and lower response time among the studied amines. For all amines vapours, the sensitivity of SWCNT/CuPcR[4] hybrid films was higher than the sensitivity of pristine Cu[1]PCR[4] films. Further work has been carried out on hybrids of SWCNT with zinc phthalocyanines (ZnPc). Thin films of pristine SWCNT and SWCNT/ZnPc hybrids were prepared by drop casting onto interdigitated electrodes and applied as active layers to detect ammonia vapor by measuring electrical resistance changes. Influence of pyrene substituent in the phthalocyanine ring on the hybrid formation and their sensor response has also been verified.

Emission of Trimethylamine from Chenopodium vulvaria - first results from quantifiying plant emissions of amines

NASA Astrophysics Data System (ADS)

Sun, Shang; Neftel, Albrecht; Jörg, Sintermann; Derstroff, Bettina; Sauvage, Carina; Bohley, Katharina; Kadereit, Gudrun; Williams, Jonathan; Pöhlker, Christopher; Kesselmeier, Jürgen; Sörgel, Matthias

2016-04-01

Amines comprise a wide range of nitrogenous organic compounds such as aliphatic methylamines MA. TMA is the most common amine species emitted by various sources and the most abundant amine in the atmosphere (Ge et al., 2011a). Additionally, TMA has been found to be the dominant amine species in the gas-phase compared to MMA and DMA at agriculture sites (Schade and Crutzen, 1995). On the global scale, the knowledge about the fluxes of most amines is limited (Ge et al., 2011a). Furthermore, terrestrial vegetation is also assumed to be a potential source for amines (Schade and Crutzen, 1995). There are a few studies from the end of the 19th century until 1975, which described high amount of MA-emission from certain plant species, which was associated with their plant tissues or with blossoms during flowering (Smith, 1971). Despite the low atmospheric concentration of amines (DMA = 0.5 ppb (Okita, 1970), TMA = 0.6 -1.6 ppb (Fujii and Kitai, 1987)), previous studies have already shown that amines play an important role in the New aerosol Particle Formation (NPF) (Almeida et al., 2013, and summarized in Sintermann and Neftel, 2015). In the atmosphere, NPF occurs frequently from gas-phase precursors. High uncertainty exists in the estimation of the global secondary aerosols budget, which was cause to the uncertain contribution of the gas-phase precursors to the NPF (Spracklen et al., 2011). It becomes more clearly that instead of binary systems of sulfuric acid and water, ternary system of sulfuric acid, water and a neutralizing compound as NH3 or amines is a key system in NPF (Almeida et al., 2013, Kurten et al., 2014). Despite their low atmospheric concentrations amines may play, at least locally, a crucial role in aerosol formation. In this study, we focus on the plant species chenopodium vulvaria, which is well known as a strong TMA-emitter (Dessaignes, 1856). But TMA emission rates from that plant species was not determined systematically up to now. In this study, we investigate on the TMA emission from chenopodium vulvaria in our dynamic cuvette system described in Sun et al. (2015). As TMA plays a key role in the atmospheric NPF, the results should give a perception of the contribution of the TMA emission from the terrestrial vegetation to the global NPF. Reference Almeida et al., Nature, 502, 359-363, 2013. Ge et al., Atmospheric Environment, 45, 524-546, 2011. Dessaignes, M., C. R. Acad. Sei. (Paris), 43, 670-671, 1856. Fujii et al., Analytical Chemistry, 59, 379-382, 1987. Kurten et al., Proceedings of the National Academy of Sciences, 111, 15019-15024, 2014. Okita, T., Atmospheric Environment, 4, 93-102 1970. Schade, G.W. and Crutzen, P.J., Journal of Atmospheric Chemistry, 22, 319-346, 1995. Sintermann, J. and Neftel, A., Biogeosciences, 12(11), 3225-3240, 2015. Smith, T. A., Biological Reviews, 46, 201-241, 1971. Spracklen et al., Atmospheric Chemistry and Physics, 11, 12 109-12 136, 2011. Sun et al., Atmospheric Measurement Techniques Discuss, 8, 12051-12104, doi:10.5194/amtd-8-12051-2015, 2015

Primary Volatile Abundances in Comets from Infrared Spectroscopy: Implications for Reactions on Grain Surfaces in the Interstellar/Nebular Environment

NASA Technical Reports Server (NTRS)

DiSanti, M. A.; Bonev, B. P.; Vilanueva, G. L.; Paganini, L.; Radeva, Y. L.; Mumma, M. J.; Gibb, E.; Magee-Sauer, K.

2012-01-01

Comets retain relatively primitive icy material remaining from the epoch of Solar System formation, however the extent to which they are modified from their initial state remains a key question in cometary science. High-resolution lR spectroscopy has emerged as a powerful tool for measuring vibrational emissions from primary volatiles (i.e., those contained in the nuclei of comets). With modern instrumentation, most notably NIRSPEC at the Keck II 10-m telescope, we can quantify species of astrobiological importance (e.g., H20, C2H2, CH4, C2H6, CO, H2CO, CH30H, HCN, NH3). In space environments, compounds of keen interest to astrobiology could originate from HCN and NH3 (leading to amino acids), H2CO (leading to sugars), or C2H6 and CH4 (suggested precursors of ethyl- and methylamine). Measuring the abundances of these precursor molecules (and their variability among comets) is a feasible task that contributes to understanding their delivery to Earth's early biosphere and to the synthesis of more complex pre biotic compounds. Over 20 comets have now been measured with IR spectroscopy, and this sample reveals significant diversity in primary volatile compositions. From this, a taxonomic classification scheme is emerging, presumably reflecting the diverse conditions experienced by pre-cometary grains in interstellar and subsequent nebular environs. The importance of H-atom addition to C2H2 on the surfaces of interstellar grains to produce C2H6 was validated by the discovery of abundant ethane in comet C/1996 B2 (Hyakutake) with C2H6/CH4 well above that achievable by gas-phase chemistry , and then in irradiation experiments on laboratory ices at 10 - 50 K. The large abundance ratios C2H6/CH4 observed universally in comets establish H-atom addition as an important and likely ubiquitous process, and comparing C2H6/C2H2 among comets can provide information on its efficiency. The IR is uniquely capable since symmetric hydrocarbons (e.g., C2H2, CH4, C2H6) have no electric dipole moment and thus no allowed pure rotational transitions. CO should also be hydrogenated on grain surfaces. Irradiation experiments on interstellar ice analogs show this to require very low temperatures, the resulting yields of H2CO and CH30H being highly dependent on temperature in the range approx 10 - 25 K. The relative abundances of these chemically-related molecules in comets provide one measure of the efficiency of H-atom addition to CO Oxidation of CO is also important on grain mantles, as evidenced by the widespread presence of C02 ice towards interstellar sources observed with ISO and in a survey of 17 comets observed with AKARI. H-atom addition to C2H2 produces the vinyl radical, and through subsequent oxidation1reduction reactions can lead to vinyl alcohol, acetaldehyde, and ethanol This may have implications for interpreting observed abundance ratios CO/C2H2. We will discuss possible implications regarding formation conditions in the context of measured primary volatile compositions, emphasizing recently observed comets and published results. These are continually providing new insights regarding our taxonomic scheme and also delivery of pre-biological material to the young Earth.

A methodology of the assessment of environmental and human health risks from amine emissions from post combustion CO2 capture technology

NASA Astrophysics Data System (ADS)

Korre, Anna; Manzoor, Saba; Simperler, Alexandra

2015-04-01

Post combustion CO2 capture (PCCC) technology in power plants using amines as solvent for CO2 capture, is one of the reduction technologies employed to combat escalating levels of CO2 in the atmosphere. However, amine solvents used for capturing CO2 produce negative emissions such as, nitrosamines and nitramines, which are suspected to be potent carcinogens. It is therefore essential to assess the atmospheric fate of these amine emissions in the atmosphere by studying their atmospheric chemistry, dispersion and transport pathways away from the source and deposition in the environment, so as to be able to assess accurately the risk posed to human health and the natural environment. An important knowledge gap until recently has been the consideration of the atmospheric chemistry of these amine emissions simultaneously with dispersion and deposition studies so as to perform reliable human health and environmental risk assessments. The authors have developed a methodology to assess the distribution of such emissions away from a post-combustion facility by studying the atmospheric chemistry of monoethanolamine, the most commonly used solvent for CO2 capture, and those of the resulting degradation amines, methylamine and dimethylamine. This was coupled with dispersion modeling calculations (Manzoor, et al., 2014; Manzoor et al,2015). Rate coefficients describing the entire atmospheric chemistry schemes of the amines studied were evaluated employing quantum chemical theoretical and kinetic modeling calculations. These coefficients were used to solve the advection-dispersion-chemical equation using an atmospheric dispersion model, ADMS 5. This methodology is applicable to any size of a power plant and at any geographical location. In this paper, the humman health risk assessment is integrated in the modelling study. The methodology is demonstrated on a case study on the UK's largest capture pilot plant, Ferrybridge CCPilot 100+, to estimate the dispersion, chemical transformation and transport pathways of the amines and their degradation products away from the emitting facilities for the worst case scenario. The obtained results are used in calculating the cancer risks centred on oral cancer slope factor (CSF), risk-specific dose (RSD) and tolerant risk level of these chemical discharges. According to the CSF and RSD relationship (WQSA, 2011), at high CSF the RSD is small i.e. resulting in a high potent carcinogen risk. The health risk assessment is performed by following the US EPA method (USEPA, 1992) which considers atmospheric concentrations of these pollutants (mg m-3, evaluated by the dispersion model), daily intake through inhalation (mg kg-1 d-1), inhalation rate (m3 d-1), body weight (kg), average time (d), exposure time (d), exposure frequency (d), absorption factor and retention factor. Deterministic and probabilistic risk estimation of human health risks caused by exposure to these chemical pollutant discharges are conducted as well. From the findings of this study, it is suggested that the developed methodology is reliable in determining the risk these amine emissions from PCCC technology pose to human health. With this reliable and a universal approach it is possible to assess the fate of the amine emissions which remains a key area to address for the large scale CCS implementation.

Distinguishing between Dexter and rapid sequential electron transfer in covalently linked donor-acceptor assemblies.

PubMed

Soler, Monica; McCusker, James K

2008-04-09

The syntheses, physical, and photophysical properties of a family of complexes having the general formula [M2(L)(mcb)(Ru(4,4'-(X)2-bpy)2)](PF6)3 (where M = Mn(II) or Zn(II), X = CH3 or CF3, mcb is 4'-methyl-4-carboxy-2,2'-bipyridine, and L is a Schiff base macrocycle derived from 2,6-diformyl-4-methylphenol and bis(2-aminoethyl)-N-methylamine) are described. The isostructural molecules all consist of dinuclear metal cores covalently linked to a Ru(II) polypyridyl complex. Photoexcitation of [Mn2(L)(mcb)(Ru((CF3)2-bpy)2)](PF6)3 (4) in deoxygenated CH2Cl2 solution results in emission characteristic of the 3MLCT excited state of the Ru(II) chromophore but with a lifetime (tau(obs) = 5.0 +/- 0.1 ns) and radiative quantum yield (Phi(r) approximately 7 x 10(-4)) that are significantly attenuated relative to the Zn(II) model complex [Zn2(L)(mcb)(Ru((CF3)2-bpy)2)](PF6)3 (6) (tau(obs) = 730 +/- 30 ns and Phi(r) = 0.024, respectively). Quenching of the 3MLCT excited state is even more extensive in the case of [Mn2(L)(mcb)(Ru((CH3)2-bpy)2)](PF6)3 (3), whose measured lifetime (tau(obs) = 45 +/- 5 ps) is >10(4) shorter than the corresponding model complex [Zn2(L)(mcb)(Ru((CH3)2-bpy)2)](PF6)3 (5) (tau(obs) = 1.31 +/- 0.05 micros). Time-resolved absorption measurements on both Mn-containing complexes at room-temperature revealed kinetics that were independent of probe wavelength; no spectroscopic signatures for electron-transfer photoproducts were observed. Time-resolved emission data for complex 4 acquired in CH2Cl2 solution over a range of 200-300 K could be fit to an expression of the form k(nr) = k0 + A x exp{-DeltaE/kB T} with k0 = 1.065 +/- 0.05 x 10(7) s(-1), A = 3.7 +/- 0.5 x 10(10) s(-1), and DeltaE = 1230 +/- 30 cm(-1). Assuming an electron-transfer mechanism, the variable-temperature data on complex 4 would require a reorganization energy of lambda approximately 0.4-0.5 eV which is too small to be associated with charge separation in this system. This result coupled with the lack of enhanced emission at temperatures below the glass-to-fluid transition of the solvent and the absence of visible absorption features associated with the Mn(II)2 core allows for a definitive assignment of Dexter transfer as the dominant excited-state reaction pathway. A similar conclusion was reached for complex 3 based in part on the smaller driving force for electron transfer (DeltaG0(ET) = -0.1 eV), the increase in probability of Dexter transfer due to the closer proximity of the donor excited state to the dimanganese acceptor, and a lack of emission from the compound upon formation of an optical glass at 80 K. Electronic coupling constants for Dexter transfer were determined to be approximately 10 cm(-1) and approximately 0.15 cm(-1) in complexes 3 and 4, respectively, indicating that the change in spatial localization of the excited state from the bridge (complex 3) to the periphery of the chromophore (complex 4) results in a decrease in electronic coupling to the dimanganese core of nearly 2 orders of magnitude. In addition to providing insight into the influence of donor/acceptor proximity on exchange energy transfer, this study underscores the utility of variable-temperature measurements in cases where Dexter and electron-transfer mechanisms can lead to indistinguishable spectroscopic observables.

EDITORIAL: Special issue: CAMOP MOLEC XVI

NASA Astrophysics Data System (ADS)

Ascenzi, Daniela; Franceschi, Pietro; Tosi, Paolo

2007-09-01

In this special issue of CAMOP/Physica Scripta we would like to present a picture of the state-of-the-art in the field of the dynamics of molecular systems. It contains a collection of papers submitted in association with the most recent MOLEC meeting (MOLEC XVI), which was held in September 2006 in Levico Terme (Italy) to celebrate the 30th anniversary of the MOLEC conference series. The series of biennial European Conferences on the Dynamics of Molecular Systems (MOLEC) started in 1976, when the first meeting was held in Trento (Italy). Successive conferences were organized in Brandbjerg Højskole (Denmark, 1978), Oxford (UK, 1980), Nijmegen (The Netherlands, 1982), Jerusalem (Israel, 1984), Aussois (France, 1986), Assisi (Italy, 1988), Bernkastel-Kues (Germany, 1990), Prague (Czech Republic, 1992), Salamanca (Spain, 1994), Nyborg Strand (Denmark, 1996), Bristol (UK, 1998), Jerusalem (Israel, 2000), Istanbul (Turkey, 2002) and Nunspeet (The Netherlands, 2004). This is the second time that Physica Scripta has hosted a special issue dedicated to MOLEC. The previous issue ( Physica Scripta (2006) 73 C1-C89) was edited by Steven Stolte and Harold Linnartz following the MOLEC 2004 conference. Following the philosophy of CAMOP, we have asked invited speakers to summarize important problems in their research area, with the objective of setting forth the current thinking of leading researchers in atomic, molecular and optical physics. This comprises discussions of open questions, important new applications, new theoretical and experimental approaches and also predictions of where the field is heading. In addition to being authoritative contributions of acknowledged experts, we hope that the papers also appeal to non-specialists as each work contains a clear and broad introduction and references to the accessible literature. The present special issue comprises 17 papers, which are arranged according to the following topics: theoretical and experimental studies of molecular collisions and chemically reactive systems (papers by Toennies, Cavalli et al, Varandas, Nyman, Allan et al, Liu et al, Boxford et al); cooling and alignment of molecular systems (papers by Kumarappan et al, van de Meerakker et al); photon-matter interactions, spectroscopy and photodissociation (papers by Fárník and Buck, Golan et al, Borghesani et al, Coreno et al); theory of complex systems (papers by Villarreal et al, Bodo et al, Yurtsever and Calvo). The final contribution concerns the dynamics of systems of biological relevance (paper by Denicke et al). The paper by Toennies, one of the founding fathers of the MOLEC conference and winner of the MOLEC award in 1996, presents a comprehensive account of the experimental developments in the field of low energy collisions over the last 30 years, and provides a short outlook on how the most recent cooling and ultra cooling techniques (helium droplets and electro-magnetic laser traps) could open up new perspectives in the field of chemical reaction dynamics. Cavalli et al present a theoretical interpretation of overlapping resonances in the reactive cross section for the benchmark reaction F + H2→HF + H, explained by the formation of a short-lived state located in the transition state region and of a van der Waals metastable state in the exit valley. The subject of accurate ab initio calculations for potential energy surfaces is addressed by Varandas in a paper describing suitable modelling strategies to obtain intermolecular potentials at near spectroscopic resolution. In the following paper, Nyman gives an overview of how thermal rate constants for polyatomic chemical reactions can be calculated from first principles: the reaction H2 + CH3→CH4 + H is used as an example and theoretical results are compared with experimental ones. The `uncharted territory' of collision dynamics at the gas-liquid interface is explored in the pioneering contribution by Allan et al, in which experimental results on the reactivity of O atoms with long chain liquid hydrocarbons are interpreted with the aid of molecular dynamics calculations. The contribution of Liu et al shifts towards the reactivity of charged systems, by presenting results of crossed beam experiments on the reaction dynamics of ethylene with OD+ and D2O+ ions. Boxford et al continue with an experimental and theoretical study of the systematics of multiply-charged anion fragmentation in dianion-cation contact ion pairs. The next two contributions present the latest findings in the field of cooling and alignment of molecular systems. Kumarappan et al provide an overview of adiabatic and non-adiabatic laser-induced alignment of linear and asymmetric top molecules. van de Meerakker and Meijer discuss the state-of-the-art of Stark deceleration of OH radicals and the prospects for future applications of such tools in scattering experiments are presented. The third section of this issue comprises spectroscopy and photodissociation studies. Fárník and Buck discuss the photodissociation of HBr molecules in three different cluster environments: pure hydrogen bonded (HBr)n clusters, large van der Waals bonded HBr.Arn and HBr.(H2O)n clusters. Differences in the photofragmentation of rovibrationally excited methylamine and propyne molecules are taken as an example by Golan et al to demonstrate the importance of vibrationally mediated photodissociation for understanding energy flows in molecular systems. A study of the IR luminescence in excited and weakly bound rare gas complexes is reported in the contribution by Borghesani et al. Coreno et al discuss the generation of core hole states by soft x-ray absorption of molecules by presenting results on the visible and UV fluorescence decay from H2O, NH3 and CH4 molecules following core electron excitation and by proposing a mechanism of molecular dissociation. The fourth section includes three theoretical contributions. In the first one, by Villarreal et al, the simulation of IR spectra of molecules solvated in atomic clusters is reviewed by presenting a method to obtain energies and wave functions for systems composed of a molecular impurity immersed in He clusters. Bodo et al continue with an application of variational and diffusion Monte Carlo calculation procedure to the `solvation' of molecular and atomic ions in small He clusters. Yurtsever and Calvo describe the influence of a central point defect on the structure of 2D clusters consisting of point charge particles that are confined by an isotropic trap. Finally, Denicke et al review the imaging technique of single-beam and multi-beam two-photon laser-scanning microscopy for biomedical research by showing applications to the study of cell metabolism via NADH imaging. We are grateful to all the authors who participated with their contributions to this issue. We thank Physica Scripta for providing us with a platform for the publication of the MOLEC special issue and we hope that such a recently established tradition will continue to bring to readers new insights into the advances in the field of molecular dynamics.